T-CODE#

00100

Range

[coarse 8,10,12,14,16,18,20 fine]

Default Value

12

Exception

20 is the default number of layers across the full gap for C-MOLD Gas-Assisted Molding.

Warning

Increasing this number increases the CPU time.

This parameter specifies the frequency at which these output variables are written to the results data file. The time interval between outputs is determined by dividing the specified fill time by the number of design outputs.

T-CODE#

00200

Range

[less disk space 0 - 100 more disk space]

Default Value

12

Warning

The disk storage requirement is linearly proportional to the number of design outputs; saving more design outputs requires more disk space.

Weld-line and air-trap analysis (in C-MOLD Filling EZ and C-MOLD Filling) requires at least 12 design outputs for reasonable interpretation.

This parameter specifies the frequency at which these output variables are written to the results data file. The time interval between outputs is determined by dividing the specified fill time by the number of detail outputs.

T-CODE#

00201

Range

[less disk space 0 - 100 more disk space]

Default Value

0

Warning

The disk storage requirement is linearly proportional to number of detail outputs; saving more detail outputs requires more disk space. One set of detail outputs requires much more disk space than one set of design outputs (by a factor of approximately one-half the specified number of layers across the full gap); for this reason, the default number of detail outputs is set to zero.

This parameter specifies the frequency at which these output variables are written to the results data file. The time interval between outputs is determined by dividing the specified post-fill time by the number of design outputs. The design outputs from C-MOLD Cooling are always saved, regardless of the number specified.

T-CODE#

00202

Range

[less disk space 0 - 100 more disk space]

Default Value

12

Warning

The disk storage requirement is linearly proportional to the number of design outputs; saving more design outputs requires more disk space.

This parameter specifies the frequency at which these output variables are written to the results data file. The time interval between outputs is determined by dividing the specified post-fill time by the number of detail outputs.

T-CODE#

00203

Range

[less disk space 0 - 100 more disk space]

Default Value

0

Warning

The disk storage requirement is linearly proportional to number of detail outputs; saving more detail outputs requires more disk space. One set of detail outputs requires much more disk space than one set of design outputs (by a factor of approximately one-half the specified number of layers across the full gap); for this reason, the default number of detail outputs is set to zero.

T-CODE#

00204

This parameter specifies the frequency at which these output variables are written to the results data file. The time interval between outputs is determined by dividing the specified mold-opening time by the number of detail outputs.

T-CODE#

00205

Range

[less disk space 0 - 100 more disk space]

Default Value

0

Warning

The disk storage requirement is linearly proportional to number of detail outputs; saving more detail outputs requires more disk space. One set of detail outputs require much more disk space than one set of design outputs (by a factor of approximately one-half the specified number of layers across the full gap); for this reason, the default number of detail outputs is set to zero.

This parameter specifies the frequency at which these output variables are written to the results data file. Design outputs in the filling stage of gas injection are saved based on filled volume; an equal volume is filled between consecutive outputs. The filling stage includes both resin injection and gas injection in filling.

T-CODE#

00206

Range

[less disk space 0 - 40 more disk space]

Default Value

4

Warning

The disk storage requirement is linearly proportional to number of detail outputs; saving more detail outputs requires more disk space.

The number of design outputs in gas injection must be less than the number of design outputs in filling (T-CODE: 00200)

If this parameter is set to zero, no design output will be saved for this stage.

This parameter specifies the frequency at which these output variables are written to the results data file. Detail outputs in the filling stage of gas injection are saved based on filled volume; an equal volume is filled between consecutive outputs. The filling stage includes both resin injection and gas injection in filling.

T-CODE#

00207

Range

[less disk space 0 - 20 more disk space]

Default Value

0

Warning

The disk storage requirement is linearly proportional to number of detail outputs; saving more detail outputs requires more disk space. One set of detail outputs require much more disk space than one set of design outputs (by a factor of approximately one-half the specified number of layers across the full gap); for this reason, the default number of detail outputs is set to zero.

This parameter specifies the frequency at which design output variables are written to the results data file during the analysis. Values recommended are 1-100.

T-CODE#

00208

Range

[less disk space 1 - 100 more disk space]

Default Value

12

Warning

The disk storage requirement is linearly proportional to the number of design outputs; saving more design outputs requires more disk space.

C-MOLD analyses use an iterative method to solve a system of algebraic equations, [A]{x} = {B}, which is derived from the finite-element/finite-difference/boundary-element formulation of the governing equations coupled with appropriate boundary conditions. [A] is called the coefficient matrix; {x} is the system of unknown (dependent) variables, and {B} is the vector of forcing terms and boundary conditions.

The iterative procedure continues until an "acceptable" pressure solution or the maximum number of iterations (see T-CODE 00400 for pressure iterations on page E-16) is reached. This acceptable solution is defined by the convergence criterion (error limit). If the difference in the function value from one iteration to the next is within the specified convergence criterion, then the solution is said to have converged, and the calculation stops.

The convergence of the solution is not always guaranteed. The factors on which convergence depends include the nature of the coefficient matrix [A] (whether it is sparse, banded, or dense), and also the number of iterations performed. On the other hand, non-convergence does not necessarily mean that the solution is bad. The outputs from the analyses have to be evaluated based on their consistency. In most cases, the results will be in the acceptable range.

Using proper meshing techniques, material properties, and processing conditions is the key to obtaining a good, converged solution.

T-CODE#

00300

Units (SI)

Percent (%)

Range

[tight 0 - 2 loose]

Default Value

0.5

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory (unrealistic, localized areas of high pressure, for example), it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

This parameter is not used in C-MOLD Filling and Post-Filling analyses, which provide solutions accurate to the machine limit.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable flow-rate solution (the maximum number of iterations) is defined in T-CODE 00401 on page E-17.

T-CODE#

00301

Units (SI)

Percent (%)

Range

[tight 0 - 2 loose]

Default Value

0.5

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory (unrealistic, localized areas of high flow rate, for example), it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

This parameter is not used in C-MOLD Filling and Post-Filling analyses, which impose the exact flow rate value at the polymer entrance(s).

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable melt-temperature solution (the maximum number of iterations) is defined in T-CODE 00402 on page E-17.

T-CODE#

00302

Units (SI)

K

Range

[tight 0 - 2 loose]

Default Value

0.2

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory (unrealistic, localized areas of high melt temperature, for example), it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

For highly temperature-sensitive materials (T_b > 20,000K in the Cross-exp model), the melt-temperature convergence criterion in C-MOLD Filling should be reduced.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. Before the melt front is advanced during the filling stage and before the time instant is advanced during the post-filling stage, C-MOLD Fiber Orientation checks whether the solution for the orientation tensor at the current iteration has changed by more than the specified percentage. The acceptable orientation solution (the maximum number of iterations) is defined in T-CODE 00405 on page E-18.

T-CODE#

00305

Units (SI)

Percent (%)

Range

[tight 0 - 2 loose]

Default value

0.5

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory, it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. Before the melt front is advanced during the filling stage and before the time instant is advanced during the post-filling stage, C-MOLD Reactive Molding checks whether the solution for the conversion level at the current iteration has changed by more than the specified percentage. The acceptable conversion solution (the maximum number of iterations) is defined in T-CODE 00406 on page E-18.

T-CODE#

00306

Units (SI)

Percent (%)

Range

[tight 0 - 2 loose]

Default Value

0.5

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory, it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

C-MOLD Runner Balancing uses the fill time as the optimization criterion; when filling is balanced, all cavities should fill at the same time. C-MOLD Runner Balancing uses an iterative procedure to determine the optimal runner sizes such that the filling of all cavities occurs at the same time.

The iterative procedure continues until an "acceptable" balancing solution or the maximum number of iterations (see T-CODE 00407 on page E-19 for balancing iterations) is reached. This acceptable solution is defined by the convergence criterion (error limit), which is defined as the maximum difference from the actual fill time, measured as a percentage of the fill time. If the difference in the function value from one iteration to the next is within the specified convergence criterion, then the solution is said to have converged, and the calculation stops.

T-CODE#

00307

Units (SI)

Percent (%)

Range

[tight 0 - 10 loose]

Default Value

5 (appropriate for most cases)

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory, it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

C-MOLD Blow Molding & Thermoforming performs equilibrium iterations for each loading step to obtain a converged solution. The governing finite-element equations are solved for each loading step. The convergence criterion (error limit) determines when the solution is deemed to have converged. Changes in both displacements and forces are checked against this value when testing for convergence.

The default value is 0.0003. The default value has been optimized to provide a good, converged solution in most cases.

T-CODE#

00308

Units (SI)

Percent (%)

Range

Recommended: 0.001 - 0.5%

Default Value

0.03%

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory, it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

where

T_int is the melt temperature at the mold-melt interface;

and are the negative- and positive-side mold-wall temperatures;

the subscripts, -b and +b, indicate the negative- and positive-side half-gap thicknesses;

k is the thermal conductivity of the polymer melt.

By default, the heat transfer coefficient is set to a high value in the C-MOLD analyses. This should not be changed unless a reliable experimental value is available.

T-CODE#

00310

Units (SI)

W/m²-K

Range

[insulated 0 - · perfect thermal contact]

Default Value

2.5 x 10⁴ W/m²-K

Warning

The mold-melt heat transfer coefficient should not be changed unless a reliable experimental value is available.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable mold-temperature solution (the maximum number of iterations) is defined in T-CODE 00403 on page E-20).

T-CODE#

00313

Units (SI)

Percent (%)

Range

[tight 0 - 2 loose]

Default Value

0.01%

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory (unrealistic, localized areas of high melt temperature, for example), it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

For cases where highly conductive materials are used, or if the cooling time is long, this mold-temperature convergence criterion in C-MOLD Cooling should be reduced.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable coolant-time solution (the maximum number of iterations) is defined in T-CODE 00413 on page E-20.

T-CODE#

00314

Units (SI)

Percent (%)

Range

[tight 0 - 2 loose]

Default Value

1.0

Warning

Tightening (reducing) this convergence criterion might, in certain cases, lead to a better solution, but at the cost of increased CPU time. The default convergence criterion used in C-MOLD analyses has been optimized and, in most cases, yields a good, converged solution.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory (unrealistic, localized areas of high temperature or post-fill time, for example), it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

For cases where highly conductive materials are used, this cooling-time convergence criterion in C-MOLD Cooling should be reduced.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable pressure convergence solution is defined by the convergence criterion (error limit; T-CODE 00300 on page E-8).

T-CODE#

00400

Range

Recommended 8 - 16

Default Value

8

Warning

Normally, there is no need to change this parameter. However, if the analysis reports non-convergence because the maximum number of iterations was exceeded and/or the solution does not look satisfactory (unrealistic, localized areas of high pressure, for example), it is advisable to increase the number of iterations (and/or tighten the convergence criterion) before executing the analysis again.

This parameter is not used in C-MOLD Filling and Post-Filling analyses, which always guarantee the solution will converge within n iterations (where n is the number of filled nodes).

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable flow-rate convergence solution is defined by the convergence criterion (error limit; T-CODE 00301 on page E-9).

T-CODE#

00401

Range

Recommended 125 - 250

Default Value

125

Warning

Normally, there is no need to change this parameter. However, if the analysis reports non-convergence because the maximum number of iterations was exceeded and/or the solution does not look satisfactory (unrealistic, localized areas of high flow rate, for example), it is advisable to increase the number of iterations (and/or tighten the convergence criterion) before executing the analysis again.

This parameter is not used in C-MOLD Filling and Post-Filling analyses.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable melt-temperature convergence solution is defined by the convergence criterion (error limit; T-CODE 00302 on page E-10).

T-CODE#

00402

Range

Recommended 100 - 200

Default Value

100

Warning

Normally, there is no need to change this parameter. However, if the analysis reports non-convergence because the maximum number of iterations was exceeded and/or the solution does not look satisfactory (unrealistic, localized areas of high melt temperature, for example), it is advisable to increase the number of iterations (and/or tighten the convergence criterion) before executing the analysis again.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable orientation convergence solution is defined by the convergence criterion (error limit; T-CODE 00305 on page E-11.

T-CODE#

00405

Default Value

100

Warning

Normally, there is no need to change this parameter. However, if the analysis reports non-convergence because the maximum number of iterations was exceeded and/or the solution does not look satisfactory, it is advisable to increase the number of iterations (and tighten the convergence criterion) before executing the analysis again.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable orientation convergence solution is defined by the convergence criterion (error limit; T-CODE 00306 on page E-11).

T-CODE#

00406

Default Value

100

Warning

Normally, there is no need to change this parameter. However, if the analysis reports non-convergence because the maximum number of iterations was exceeded and/or the solution does not look satisfactory, it is advisable to increase the number of iterations (and tighten the convergence criterion) before executing the analysis again.

C-MOLD Runner Balancing uses the fill time as the optimization criterion; when filling is balanced, all cavities should fill at the same time. C-MOLD Runner Balancing uses an iterative procedure to determine the optimal runner sizes such that the filling of all cavities occurs at the same time.

The iterative procedure continues until an acceptable balancing solution or the maximum number of iterations is reached. This acceptable solution is defined by the convergence criterion (error limit; T-CODE 00307 for balancing convergence), which is defined as the maximum difference from the actual fill time, measured as a percentage of the fill time. If the difference in the function value from one iteration to the next is within the specified convergence criterion, then the solution is said to have converged, and the calculation stops.

The maximum number of iterations provides a safety net to prevent computations from proceeding without termination for unrealistically small convergence criteria, and to re-calibrate iterative settings within the analysis if convergence is not achieved for any specific time step.

T-CODE#

00407

Default Value

10

Warning

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory, it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

C-MOLD Blow Molding & Thermoforming performs equilibrium iterations for each loading step to obtain a converged solution. The governing finite-element equations are solved for each loading step. The convergence criterion (error limit) determines when the solution is deemed to have converged. Changes in both displacements and forces are checked against this value when testing for convergence.

The number of iterations needed to achieve convergence for a loading step depends on the rate of convergence and the specified convergence criterion. If the convergence criterion is increased, fewer iterations would be required for convergence, possibly at the cost of solution accuracy, and vice-versa.

The maximum number of iterations provides a safety net to prevent computations from proceeding without termination for unrealistically small convergence criteria, and to re-calibrate iterative settings within the analysis if convergence is not achieved for any specific loading step.

If the maximum number of iterations is achieved repeatedly without convergence, the solution is terminated.

T-CODE#

00408

Default Value

20

Warning

If the maximum number of iterations is achieved repeatedly without convergence, the solution is terminated.

Normally, there is no need to change the convergence criterion; however, if the analysis reports non-convergence, or the solution does not look satisfactory, it is advisable to tighten this parameter (and increase the number of iterations) before executing the analysis again.

See paragraphs 2 through 5 in "Pressure convergence criterion," for a description on the iterative method C-MOLD analyses use to solve algebraic equations. The acceptable mold-temperature convergence solution is defined by the convergence criterion (error limit; T-CODE 00313 on page E-15).

T-CODE#

00413

Range

Recommended 20 - 100

Default Value

75

Warning

Normally, there is no need to change this parameter. However, if the analysis reports non-convergence because the maximum number of iterations was exceeded and/or the solution does not look satisfactory (unrealistic, localized areas of high mold temperature, for example), it is advisable to increase the number of iterations (and/or tighten the convergence criterion) before executing the analysis again.

If multiple restart times are specified, in subsequent executions, the program will continue the calculation by reading the restart file until it reaches the next earliest restart time.

This is a particularly useful feature when different post-fill times or pack/hold pressure profiles are examined in C-MOLD Post-Filling; in such cases, the restart time may be specified to be the fill time, and the subsequent analysis will continue from the end of the filling stage. This saves considerable computational time.

Intermediate results can also be viewed using this option.

T-CODE#

00512

Units (SI)

s

The contribution from pressure work is significant only in cases where the pressure gradient is very large. In all other cases, including this term will have negligible effect on the temperature calculation.

To include pressure work, this option must be set to 1.

T-CODE#

00514

Range

0 - No, 1 - Yes

Default Value

0

Warning

The effect of pressure work is usually very small compared to other effects, such as viscous heating. It is significant only in cases where the pressure gradient is very large.

Pressure losses occur in the runner system when the melt passes through runners with significant change in diameters. These pressure losses are especially pronounced in areas near the gate.

The analysis automatically traces the runner system and searches for any sudden contraction in the runner diameters that is greater than 2/1, in which case, it calculates the effect of juncture losses. The analysis uses by default an internally implemented model to calculate juncture losses; however, if a juncture-loss model is specified in the material properties data file (filename.mtl), it will override the internal model.

The constants for the juncture-loss model are obtained by applying the Bagley corrections to the capillary viscosity data.

T-CODE#

00516

Range

0 - No, 1 - Yes

Default Value

0

Warning

The juncture loss data should be characterized and specified in the material properties data file for the most accurate juncture-loss prediction.

If a subsequent analysis is executed where only the material properties or process conditions have been changed, then using the restart option saves CPU time by not recomputing the geometry information, which in some cases (depending on the model) might take a long time.

Memory requirements are large to store a restart file. The restart file itself might take up a lot of disk space depending on the size of the model; for this reason, the restart file is not saved by default (the option is set to 0 by default).

T-CODE#

00520

Range

0 - No, 1-Yes

Default Value

0

Warning

The restart option works only if no changes are made to the geometry.

Memory requirements are large to store a restart file; the larger the size of the model, the more disk space required to store the restart file.

If the mesh is fine, and no features of the part are close to each other, then reducing this value from its default value of 13 reduces the CPU time.

T-CODE#

00521

Range

Allowed values are 4, 7, and 13

Default Value

13

Warning

Do not use lower values of this parameter when the mesh is coarse. Doing so might reduce solution accuracy.

Machining accuracy must be kept in mind when defining this value. A more accurate figure for the diameter would not be useful, if the runner system could not be machined with matching accuracy.

T-CODE#

00542

Units (SI)

m

Range

0 - 1 (m)

Default Value

0.001 m

Warning

Machining accuracy must be kept in mind when defining this value. A more accurate figure for the diameter would not be useful, if the runner system could not be machined with matching accuracy.

This parameter also places a limit on unnecessary calculations.

T-CODE #

00544

Units (SI)

Percent (%)

Range

0 - 500

Default Value

25

Warning

This limit is set so that the volume of runners does not exceed a specified value when the runner size is adjusted.

T-CODE#

00550

Range

Values allowed are 11, 12, and 20
11 - Two-Dimensional axisymmetric analysis
12 - Two-Dimensional plane-strain analysis
20 - Three-Dimensional analysis

Default Value

20

This parameter allows the analysis to commence from a stable configuration, by imparting a non-singular stiffness to the initial parison or sheet geometry.

T-CODE#

00552

Range

Greater than 1.0 and less than 1.1.

Default Value

1.02

Warning

It is recommended that the default value be used.

The size of the initial increment for pressurization stages set by this parameter is subsequently adjusted depending on the rate of convergence. A smaller initial displacement results in more rapid initial convergence, at the cost of smaller advances in the solution itself. A larger initial displacement might result in lack of convergence within the maximum number of iterations specified for each loading step.

T-CODE#

00554

Equation

None

Units (SI)

Percent (%)

Range

0 - 1%

Default Value

0.5

Warning

A smaller initial displacement results in more rapid initial convergence, at the cost of smaller advances in the solution itself. A larger initial displacement might result in lack of convergence within the maximum number of iterations specified for each loading step.

The number of loading steps depends on the complexity of the problem. If the solution terminates due to reaching the maximum number of loading steps, the analysis can be executed again after increasing this parameter. This parameter must be increased for analysis involving movement of mold-surface regions with a high degree of complexity.

T-CODE#

00556

Range

Integers greater than 1 (recommended 1 - 300)

Default Value

100

Warning

The number of loading steps depends on the complexity of the problem. If the solution terminates due to reaching the maximum number of loading steps, the analysis can be executed again after increasing this parameter. This parameter must be increased for analysis involving movement of mold-surface regions with a high degree of complexity.

If the option is turned off (set to 0), then only regular post-filling analysis will be performed, and no interface file to structural analysis programs will be generated. If the option is set to 1, then C-MOLD Residual Stress will be executed, and the interface file for structural analysis will be generated according to the option for structural package (T-CODE 00602).

T-CODE#

00600

Range

0 - No, 1 - Yes

Default Value

1

Warning

Make sure this option is set to 1 if C-MOLD Residual Stress is to be executed.

The interface files contain all necessary input data for finite-element structural analysis. The structural analysis software packages for which the interface files can be written (other than C-MOLD) are ANSYS and ABAQUS.

The default interface file is the neutral file (the option set to 0), which is used by C-MOLD Shrinkage & Warpage and ANSYS. The other options are generating input (filename.inp) files for ABAQUS with linear and non-linear options (options 1 and 2, respectively).

T-CODE#

00602

Range

0 - Neutral file only (for C-MOLD Shrinkage & Warpage or ANSYS)
1 - Neutral file and input file for ABAQUS with linear option
2 - Neutral file and input file for ABAQUS with non-linear option

Default Value

0

If the option for structural analysis (T-CODE 00602) is set either to 1 or 2, to generate interface files for ABAQUS with linear or non-linear option, then by setting the isolate mechanism for warpage option to 1, interface files corresponding to various loading conditions will be generated. The loading conditions are as follows:

1. Total loading: This contains pseudo temperature difference, pseudo temperature gradient, nodal force and moments, stored in filename.inp.
2. Loading due to shrinkage effects only: This contains pseudo temperature difference and nodal forces, stored in filename_s.inp.
3. Loading due to uneven cooling only: This contains pseudo temperature gradients and nodal moments, stored in filename_c.inp.

T-CODE#

00604

Range

0 - No, 1 - Yes

Default Value

1

Warning

This option only works if the option for structural analysis (T-CODE 00602) is set to 1 or 2, to generate interface files for ABAQUS.

It is not strictly correct to separate the warpage as a combination of warpage due to shrinkage effects and warpage due to cooling effects because of the non-linear nature of the problem. This capability is provided only to identify the dominant cause of warpage.

T-CODE#

00606

Range

0 - No, 1 - Yes

Default Value

0

As the number increases, more Prony Series modes are used, and more accurate results are expected.

T-CODE#

00610

Range

1 - 3

Default Value

3

Warning

In this release, only values up to 3 can be used. Using higher numbers of constants requires the use of visco-elastic material model constants, which are difficult to obtain.

T-CODE#

00612

Range

0 - 1

Default Value

0

Warning

In this release, non-linear analysis of Shrinkage & Warpage with large loadings will introduce unbalance forces during the calculation of deformation, which may lead to an incorrect result. The proper way to do this is to use internal stresses instead of converted "equivalent loadings," such as the loadings in the neutral file. C-MOLD development is working on passing layer-based residual stress and property information from the Residual Stress calculation to the structural analysis.

T-CODE#

00613

Range

0 - 30

Default Value

20

If the option is turned off (set to 0), then only standard filling and post-filling analyses will be executed, and no interface file for structural analysis will be generated. If the option is turned on (set to 1), then C-MOLD Fiber Orientation will be executed.

T-CODE#

00620

Range

0 - No, 1 - Yes

Default Value

0

Warning

This parameter must be set to 1 for C-MOLD Fiber Orientation to be executed.

Alternately, this interaction coefficient can be estimated from the empirical equation proposed by Bay, as shown below:

where

is the scaled concentration

c is the fiber concentration

L is the fiber length

d is the fiber diameter

This equation is only valid if the scaled concentration > 1.

T-CODE#

00622

Equation

Units (SI)

c: Kg/Kg (dimensionless)
L: m
d: m

Default Value

0.001

Warning

This equation is valid only for > 1.

If the fiber shape factor is set equal to:

where re is the equivalent ellipsoidal aspect ratio, and the fiber interaction coefficient (T-CODE 00622) is set equal to 0, then the evolution equation reduces to Jeffrey's equation for the motion of a single ellipsoid.

T-CODE#

00624

Range

0 - 1

Default Value

1.0

If this parameter is set to 0, the fiber orientation state at the polymer entrance is assumed to be aligned at the skin and transverse at the core. This orientation state is more appropriate if the flow at the polymer entrance is radial, which typically occurs downstream from a pin gate.

If this parameter is set to 1, the fiber orientation state at the polymer entrance is assumed to be aligned at the skin and random at the core. This orientation state is more appropriate if the flow at the polymer entrance is unidirectional, which typically occurs downstream from a line gate.

The default boundary condition option is 0 (aligned at the skin and transverse at the core).

T-CODE#

00626

Equation

None

Units (SI)

N/A

Range

0 - aligned at the skin and transverse at the core
1 - aligned at the skin and random at the core

Default Value

0

Warning

The boundary condition option should be chosen with respect to the flow conditions at the polymer entrance (which depends on the type of gate).

If this option is turned off (set to 0), C-MOLD Fiber Orientation will stop at the end of the filling stage, and no fiber orientation data will be generated during the post-filling stage.

If the option is turned on (set to 1), C-MOLD Fiber Orientation continues the analysis through the post-filling stage.

In either case, the interface file to structural analysis will be written to the results data file.

Even though the dominant driving force for fiber orientation occurs during the filling stage, additional fiber alignment and randomization may also occur during the post-filling stage.

T-CODE#

00627

Range

0 or 1

Default Value

0

Warning

This option has to be turned on (set to 1) if fiber orientation analysis is to be performed during the post-filling stage.

C-MOLD allows you to choose one or two polymer materials The second polymer material is the same as the first polymer material, except the T-CODE number changes from 01xxx to 02xxx, and "-2" is added to the end of each description. For example, constant polymer density for the first polymer material has a T-CODE of 01000. The name of the second polymer material is constant polymer density -2, and the T-CODE is 02000.

Constant polymer density

This data set specifies the melt density of the polymer. C-MOLD Filling assumes that the melt density is constant (the melt is incompressible).

This single-point density of the polymer under processing conditions is measured using a capillary rheometer (extrusion flow rate measurement).

If the solid density is known, a reasonable estimate of the melt density is:

T-CODE#

01000

Units (SI)

kg/m³
Approximate order of magnitude

10³ kg/m³

Warning

C-MOLD Post-Filling requires pvT data for calculating the density variation with pressure and temperature (T-CODE 01003, 01004, or 01005).

Constant polymer density & transition temperature

This data set specifies the parameters of a model for constant polymer density and transition temperature.

T-CODE#

01002

Equation

Order of parameters in the data set

[b5, b6, ]

Units (SI)

b5: K
b6: K/Pa
: kg/m³

2-domain S-G polymer density

This data set specifies the parameters of the 2-domain S-G (Spencer-Gilmore) equation of state, which describes the variation of density (specific volume) with temperature and pressure in the melt and solid domains (pvT data).

The pvT data reflect the transitions as the material undergoes a phase change from one physical state to the other (from melt to solid). pvT data are required by C-MOLD Post-Filling, because this analysis considers the melt to be weakly compressible.

T-CODE#

01003

Equation

The subscripts, m and s, refer to the melt and solid states.
, , and are model constants.
Order of parameters in the data set

Units (SI)

b5: K
b6: K/Pa
: Pa
: Kg/m³
: J/Kg-K

Warning

The 2-domain modified Tait polymer density model (T-CODE 01004) has been found to be more accurate for C-MOLD Post-Filling.

2-domain modified Tait polymer density

This data set specifies the parameter of an equation of state that describes the variation of density (specific volume) with temperature and pressure in the melt and solid domains, between room temperature and processing temperature and over a pressure range of 0 - 200 MPa.

This model has been found to be adequate for C-MOLD Post-Filling, in which the melt is considered to be weakly compressible. The variation of density is much more significant in the post-filling stage.

The pvT data reflect the transitions as the material undergoes a phase change from one physical state to the other (from melt to solid). The kink in the curve of pvT data of amorphous thermoplastics at atmospheric pressure is the glass transition temperature of the material (T_g). This is a function of pressure. The slopes of the specific volume vs. temperature curves in the melt and solid domains (b2m and b2s) represent the bulk thermal expansion coefficients in the melt and solid states, respectively.

An abrupt transition in the specific volume vs. temperature curve is observed in the case of semi-crystalline polymers. This is associated with the crystallization temperature (T_c), which is also a function of pressure.

A high pressure dilatometry method is used to obtain the pvT data. This method is also known as the indirect method. It involves applying the pressure to the specimen by means of a confining fluid. The specimen and the fluid are enclosed in a chamber fitted with bellows. The deflection of the bellows is used to measure the change in volume.

Another common test method is the direct method, which involves applying the pressure directly to the specimen using a piston and cylinder setup. Piston deflections are used to measure the volume change when subjected to a range of pressures.

T-CODE#

01004

Equation

Universal constant, C = 0.0894

Transition temperature, T_t = b5 + b6 x p

where

The subscripts, m and s, refer to the melt and solid states.
Order of parameters in the data set

[b5, b6, b1m, b2m, b3m, b4m, b1s, b2s, b3s, b4s, b7, b8, b9]

Units (SI)

b5: K
b6: K/Pa
b1m, b1s, b7: m³/kg
b2m, b2s: m³/kg-K
b3m, b3s: Pa
b4m, b4s: 1/K
b8: 1/K
b9: 1/Pa
Orders of magnitude (for most polymers)

~ 10^-3 m³/kg
b5 ~ 400 K
b6 ~ 10^-7 K/Pa
b1 ~ 10 ^-3 m³/kg
b2 ~ 10^-6 m³/kg-K
b3 ~ 10⁸ Pa
b4 ~ 10³ 1/K
b7, b8, b9 ~ 0

Warning

If this pvT model is used for C-MOLD Filling, the program derives a constant density at the injection melt temperature and a pressure of 50 MPa.

If pvT data (in the form of the 2-domain modified Tait model) are not available for a particular grade of resin, then the model constants for the corresponding generic grade of resin may be used as a first approximation. The pvT constants for generic grades are available in the C-MOLD Database.

2-domain polymer density

This data set specifies the eight constants of the 2-domain polymer density model.

This pvT model is an equation of state that describes the variation of density (specific volume) with temperature and pressure in the melt and solid domains, in the processing range.

pvT data is required by C-MOLD Post-Filling, in which the melt is considered to be weakly compressible.

T-CODE#

01005

Equation

Transition temperature, T_t = b5 + b6 x p

where

The subscripts, m and s, refer to the melt and solid states.

b1, b5, b6, , and K are model constants.
Order of parameters in the data set

[b5, b6, b1m, m, K_m, b1s, s, K_s]

Units (SI)

b5: K
b6: K/Pa
b1m, b1s: m³/kg
m, s: 1/K
K_m, K_s: Pa

Constant polymer specific heat

This data set specifies the single-point melt specific heat. Specific heat refers to the amount of heat needed to raise the temperature of 1 kg of specimen by 1 K.

C-MOLD Filling requires the specification of the average specific heat over the processing temperature range, which is taken to be the melt (single-point) specific heat. C-MOLD Cooling also uses constant specific heat, if tabulated data (T-CODE 01101) are not available.

The standard method ASTM E1269 is used to determine specific heat capacity with a differential scanning calorimeter (DSC).

T-CODE#

01100

Units (SI)

J/kg-K
Order of magnitude (for most polymers)

10³ J/kg-K

Warning

It is crucial to incorporate the effect of temperature on specific heat (T-CODE 1101) in C-MOLD Post-Filling and C-MOLD Cooling.

Tabulated polymer specific heat

This data set specifies the specific heat values as a function of temperature. Specific heat refers to the amount of heat needed to raise the temperature of 1 kg of specimen by 1 K.

It is crucial to incorporate the change in specific heat with temperature over a large temperature range in C-MOLD Post-Filling. The temperature range must cover the region between the processing temperature and the solid state.

The inflection in the specific heat vs. temperature plot corresponds to the glass transition temperature for amorphous materials. Depending on the material, the specific heat may vary 50-70% between the processing temperature and room temperature.

For semi-crystalline polymers, the area under the peak and above the baseline represents the latent heat of crystallization. For these materials, the peak of specific heat is shifted according to DSC heating or cooling scan rate. In this case, crystallization kinetics have to be incorporated to describe the rate dependence of specific heat.

The standard method ASTM E1269 is used to determine specific heat capacity with a differential scanning calorimeter (DSC) over the temperature range between the processing temperature and the solid state.

T-CODE#

01101

Units (SI)

C_p: J/kg-K
T: K

Warning

If this tabulated specific heat data set is used in C-MOLD Filling, the program will derive the specific heat value at the injection melt temperature.

C-MOLD Cooling calculates the specific heat at a temperature that is the average of the inlet melt temperature and the coolant temperature.

Amorphous polymer specific heat function

This data set specifies the parameters for a model that describes the specific heat variation with temperature for amorphous polymers.

The specific heat data at temperatures between the processing temperature and room temperature are obtained using the standard method ASTM E1269 to determine specific heat with a differential scanning calorimeter (DSC).

The data obtained are fitted according to the following model:

where and c₁, c₂, c₃, c₄, and c₅ are model constants.

T-CODE#

01102

Equation

Order of parameters in the data set:

[c₅, c₁, c₂, c₃, c₄]

Units (SI)

c₅: K
c₁, c₃: J/kg-K
c₂: J/kg-K²
c₄: 1/K

Crystalline polymer specific heat function

This data set specifies the parameters for a model that describes the specific heat variation with temperature for semi-crystalline polymers.

The transition shifts for these materials can be dramatic when they undergo high cooling rates (quenching) that are typical during the injection molding process. It is desirable to obtain specific heat data under high cooling rates.

The specific heat data at temperatures between the processing temperature and room temperature are obtained using the standard method ASTM E1269 to determine specific heat with a differential scanning calorimeter (DSC).

The data obtained are fitted according to the following model:

where and c₅, c₁, c₂, c₃, and c₄ are model constants

T-CODE#

01103

Equation

Order of parameters in the data set

[c₅, c₁, c₂, c₃, c₄]

Units (SI)

c₅: K
c₁, c₃: J/kg-K
c₂: J/kg-K²
c₄: 1/K²

Constant polymer thermal conductivity

This data set specifies the constant polymer thermal conductivity.

Thermal conductivity is a very important polymer property. Physically, it represents the amount of heat conducted by the material per unit time, per unit area, and per unit negative temperature gradient. The value of thermal conductivity significantly influences the pressure prediction in injection molding simulation.

C-MOLD Filling uses the single-point, constant melt thermal conductivity. C-MOLD Cooling also uses this value, if tabulated data (T-CODE 01201) are not available.

A transient, line-source technique is used to measure thermal conductivity. The K-SYSTEM II from AC Technology is one of the thermal conductivity measuring devices available in the market.

T-CODE#

01200

Units (SI)

W/m-K
Order of magnitude (for most polymers)

10^-1 W/m-K

Warning

Using tabulated data for thermal conductivity (T-CODE 01201) improves the accuracy of predictions in C-MOLD Post-Filling.

Tabulated polymer thermal conductivity

This data set specifies the thermal conductivity as a function of temperature.

Thermal conductivity is a very important polymer property. Physically, it represents the amount of heat conducted by the material per unit time, per unit area, and per unit negative temperature gradient.

Thermal conductivity is a function of temperature. It is crucial to incorporate the change in thermal conductivity with temperature over a large temperature range in C-MOLD Post-Filling. The temperature range must cover the region between the processing temperature and the solid state.

For amorphous polymers, the plot of thermal conductivity vs. temperature consists of two distinct regions in a piece-wise, linear manner. The thermal conductivity remains constant above the glass transition temperature (T_g) and decreases linearly when the temperature falls below T_g. The slope of the line below T_g is approximately 0.04 W/m-K for almost all pure amorphous polymers.

For semi-crystalline polymers, the thermal conductivity abruptly increases when the temperature falls below the crystallization temperature, T_c. Below T_c, the crystalline phase appears, which creates regions of high thermal conductivity. It is important to consider these effects during the analysis.

A transient, line-source technique is used to measure thermal conductivity. For tabulated data, the thermal conductivity is scanned at temperatures from the processing temperature to the solid state temperature. More data points are collected near the transition temperature. The K-SYSTEM II from AC Technology is one of the thermal conductivity measuring devices available in the market.

T-CODE#

01201

Units (SI)

k: W/m-K
T: K

Warning

If this tabulated thermal conductivity data set is used in C-MOLD Filling, the program will derive the thermal conductivity value at the injection melt temperature.

C-MOLD Cooling calculates the thermal conductivity at a temperature that is the average of the inlet melt temperature and the coolant temperature.

Tanh function polymer thermal conductivity

This data set specifies the parameters of a model that describes the variation of thermal conductivity with temperature.

The thermal conductivity data at temperatures between the processing temperature and room temperature are obtained using the transient, line-source technique.

The data obtained are fitted according to the following model:

where and c₁, c₂, c₃, c₄, and c₅ are model constants.

T-CODE#

01202

Equation

where
Order of parameters in the data set

[c₅, c₁, c₂, c₃, c₄]

Units (SI)

c₅: K
c₁, c₃: W/m-K
c₂: W/m-K²
c₄: 1/K

Constant polymer viscosity

This data set specifies the constant polymer viscosity at the processing temperature.

Viscosity is a very important rheological property that measures the material resistance to deformation. It characterizes the flow behavior of the material. The viscosity function is required by C-MOLD Filling.

Viscosity of polymer melts varies with shear rate, pressure, and temperature. Because of this, using a constant value for viscosity is inappropriate and is not recommended.

T-CODE#

01300

Units (SI)

Pa-s

Warning

Viscosity of polymer melts varies with shear rate, pressure, and temperature. Because of this, using a constant value for viscosity is inappropriate and is not recommended.

Viscosity models that account for the variation with shear rate, pressure, and temperature should be used in the analysis. Such viscosity models include the Cross-Exp (T-CODE 01303) and Cross-WLF (T-CODE 01313) models.

Power-law-exp polymer viscosity

This data set defines the parameters for a power-law viscosity model. The model incorporates the effect of shear rate and temperature on viscosity.

Viscosity is a very important rheological property that measures the material resistance to deformation. It characterizes the flow behavior of the material.

Most polymers exhibit two regimes of flow behavior: Newtonian and shear thinning. Newtonian behavior occurs at low shear rates, when the shear-stress-to-shear-rate relationship is linear. At higher shear rates, the viscosity decreases as the shear rate increases; this behavior is called shear thinning.

This model only works when shear rates are high. This model also does not account for the effect of pressure. Using this power-law model alone might lead to inaccuracies in the solution and is not recommended.

Capillary rheometers are usually used to measure viscosity.

T-CODE#

01302

Equation

where T is the temperature

T_a is the ambient temperature

is the shear rate

n and A are model constants
Order of parameters in the data set

[n, A, T_a]

Units (SI)

n: dimensionless
A: Pa-sⁿ
T_a: K

Range

0 < n < 1

Warning

This model does not properly describe the polymer viscosity at low shear rates and does not account for the effect of pressure. Using this power-law model alone might lead to inaccuracies in the solution and is not recommended.

Cross-exp polymer viscosity

This data set specifies the five constants of the Cross-exp polymer viscosity model, which accounts for the effect of temperature, shear rate, and pressure on the viscosity.

Viscosity is a very important rheological property that measures the material resistance to deformation. It characterizes the flow behavior of the material.

Most polymers exhibit two regimes of flow behavior: Newtonian and shear thinning. Newtonian behavior occurs at low shear rates, when the shear-stress-to-shear-rate relationship is linear. At higher shear rates, the viscosity decreases as the shear rate increases; this behavior is called shear thinning.

In the Cross-exp model, the transition between the Newtonian and shear thinning regimes is characterized by the parameter, ^*. ^* represents the shear stress at which the onset of shear thinning behavior occurs.

The value of (1 - n), where n is a power-law coefficient in this model, represents the slope of the shear thinning curve. The remaining constants are used to model the zero-shear rate viscosity, ₀.

The parameter, T_b, characterizes the temperature sensitivity of ₀. This tends to depend on temperature, especially near T_g. However, in the filling stage, the bulk temperature is usually far higher than T_g, and because of this, the Cross-exp model is adequate for C-MOLD Filling.

The parameter, , characterizes the pressure dependence of ₀. It is not necessary to determine this constant, since most of the viscosity measurements are performed in the processing pressure range of nearly 50 Mpa. Accordingly, the data already includes the effect of pressure. As such, this parameter can be set to zero.

The parameter, , fixes the level of ₀.

The viscosity data are obtained using the standard method ASTM D3835 to determine rheological properties of thermoplastics with a capillary rheometer. Measurements are made for at least three different temperatures and over a wide shear rate range. The coefficients are derived by fitting the data to this model.

T-CODE#

01303

Equation

is the zero-shear-rate viscosity

is the shear rate

T is the temperature

p is the pressure

n, ^*, B, T_b, and are model constants
Order of parameters in the data set

[, ^*, B, T_b, ]

Units (SI)

n: dimensionless
^*: Pa
B: Pa-s
T_b: K
: 1/Pa

Range

0 < n < 1

Warning

This model is adequate for C-MOLD Filling. However, for C-MOLD Post-Filling, where the polymer melt undergoes substantial cooling throughout the cavity, the use of this model may become inappropriate. The value of T_b, which represents the temperature sensitivity of ₀, is a strong function of temperature. This model corresponds to a constant value of T_b, which is a poor approximation when modeling the behavior over a large temperature range. The Cross-WLF viscosity model (T-CODE 01313) is recommended for C-MOLD Post-Filling.

Carreau-exp polymer viscosity

This data set specifies the five constants of the Carreau-exp polymer viscosity model, which accounts for the affect of temperature, shear rate, and pressure on the viscosity.

Viscosity is a very important rheological property that measures the material resistance to deformation. It characterizes the flow behavior of the material.

This model is adequate for C-MOLD Filling.

Capillary viscosity measurements over different temperature and shear rate ranges are taken, and the data obtained are fitted to this model.

T-CODE#

01304

Equation

is the zero-shear-rate viscosity

is the shear rate

T is the temperature

p is the pressure

n, ^*, B, T_b, and are model constants
Order of parameters in the data set

[n, ^*, B, T_b, ]

Units (SI)

n: dimensionless
^*: Pa
B: Pa-s
T_b: K
: 1/Pa

Range

0 < n < 1

Warning

This model is adequate for C-MOLD Filling. However, for C-MOLD Post-Filling, where the polymer melt undergoes substantial cooling throughout the cavity, the use of this model may become inappropriate. The value of T_b, which represents the temperature sensitivity of ₀, is a strong function of temperature. This model corresponds to a constant value of T_b, which is a poor approximation when modeling the behavior over a large temperature range. The Cross-WLF viscosity model (T-CODE 01313) is recommended for C-MOLD Post-Filling.

Cross-WLF polymer viscosity

This data set specifies the seven constants of the Cross-WLF polymer viscosity model, which accounts for the effect of temperature, shear rate, and pressure on the viscosity, over a wide temperature range.

Viscosity is a very important rheological property that measures the material resistance to deformation. It characterizes the flow behavior of the material.

This model still represents the shear-thinning behavior in the same manner as the Cross-Exp model; however, the zero-shear-rate viscosity is represented by a more extensive model that is based on the WLF functional form.

The Cross-WLF model is more appropriate for C-MOLD Post-Filling, because the temperature and pressure sensitivities of the zero-shear-rate viscosity are better represented.

The viscosity data are obtained using the standard method ASTM D3835 to determine rheological properties of thermoplastics with a capillary rheometer. Measurements are made at at least three different temperatures and over a wide shear rate range. The coefficients are derived by fitting the data to this model.

T-CODE#

01313

Equation

₀ is the zero-shear rate viscosity

is the shear rate

T is the temperature

p is the pressure

is a reference temperature and is typically taken as the glass transition temperature of the material.

n, ^*, D₁, D₂, D₃, A₁, and are model constants
Order of parameters in the data set

[n, ^*, D₁, D₂, D₃, A₁, ]

Units (SI)

n, A₁: dimensionless
^*: Pa
D₁: Pa-s
D₂, A₂: K
D₃: K/Pa

Range

0 < n < 1

Warning

If both Cross-exp and Cross-WLF data are specified for use in C-MOLD Post-Filling, the program will use the model with the greater number of constants; the Cross-WLF model will be used.

Carreau-WLF polymer viscosity

This data set specifies the seven constants of the Carreau-WLF polymer viscosity model, which accounts for the effect of temperature, shear rate, and pressure on the viscosity, over a wide temperature range.

Viscosity is a very important rheological property that measures the material resistance to deformation. It characterizes the flow behavior of the material.

This model still represents the shear-thinning behavior in the same manner as the Cross-Exp model; however, the zero-shear-rate viscosity is represented by a more extensive model that is based on the WLF functional form.

This model is more appropriate for C-MOLD Post-Filling, because the temperature and pressure sensitivities of the zero-shear-rate viscosity are better represented.

The viscosity data are obtained using the standard method ASTM D3835 to determine rheological properties of thermoplastics with a capillary rheometer. Measurements are made at at least three different temperatures and over a wide shear rate range. The coefficients are derived by fitting the data to this model.

T-CODE#

01314

Equation

₀ is the zero-shear rate viscosity

is the shear rate

T is the temperature

p is the pressure

is a reference temperature and is typically taken as the glass transition temperature of the material.

n, ^*, D₁, D₂, D₃, A₁, and are model constants
Order of parameters in the data set

[n, ^*, D₁, D₂, D₃, A₁, ]

Units (SI)

n, A₁: dimensionless
^*: Pa
D₁: Pa-s
D₂, A₂: K
D₃: K/Pa

Range

0 < n < 1

Warning

If both Cross-exp or Carreau-exp and Carreau-WLF data are specified for use in C-MOLD Post-Filling, the program will use the model with the greater number of constants; the Carreau-WLF model will be used.

Campus Carreau-WLF viscosity

This data set specifies the five constants of the Campus Carreau-WLF viscosity model.

T-CODE#

01315

Equation

_T is the zero-shear-rate viscosity at temperature, T

is the shear rate

K₁, K₂, K₃, K₄, and K₅ are model constants
Order of parameters in the data set

[K₁, K₂, K₃, K₄, K₅]

Units (SI)

K₁: Pa-s
K₂: s
K₃: dimensionless
K₄, K₅: C

Moldflow power-law viscosity

This data set specifies the four constants of the Moldflow Power-law viscosity model.

T-CODE#

01322

Equation

where T_{no flow} is the temperature of melt freeze-off, which is typically the glass transition temperature.

T is the temperature

is the shear rate

A, B, and C are model constants
Order of parameters in the data set

[A, B, C, T_{no flow}]

Units (SI)

A: Pa-s^1+B
B: dimensionless
C: 1/C
T_{no flow}: C

Warning

This model is not appropriate for C-MOLD Post-Filling, which requires higher-order terms to represent the viscosity over a wider range of temperature, pressure, and shear rates.

Moldflow second-order viscosity

This data set specifies the seven constants of the Moldflow second-order viscosity model.

T-CODE#

01325

Equation

where T_{no flow} is the temperature of melt freeze-off, which is typically the glass transition temperature.

Units (SI)

A, B, C, D, E, F: dimensionless
T: C

Melt flow index

This data set specifies the melt flow index, which is a measure of viscosity. The melt flow index is not used directly in C-MOLD Filling. It provides an approximate measure of viscosity at one temperature and at low shear rates.

The standard method ASTM D1238 is used to measure the melt flow index with a capillary rheometer. The basic principle involved is measuring the mass of polymer melt (at a given temperature) extruded through a capillary of known L/D ratio in 10 minutes. This flow rate is the melt flow index. It gives an indication of viscosity: the higher the flow rate (melt flow index), the lower the viscosity of the material, and vice-versa.

This value should be used only for comparing two similar resins. Depending on their respective melt flow indices, they might also be expected to show the same trends with respect to viscosities at higher shear rates. This could provide an idea of their filling behavior during injection molding.

T-CODE#

01330

Units (SI)

g/10min

Warning

This is not an exact measure of viscosity and is not used in C-MOLD Filling. This is meant only to provide a comparison of the flow behavior of similar resins.

Reactive polymer viscosity I

This data set specifies the six constants of the Reactive Polymer Viscosity (I) model, which describes the viscosity behavior as a function of temperature, shear rate, and conversion. In thermoset injection molding, the viscosity of the polymer is also a function of the conversion (or curing) level.

The viscosity increases dramatically when the conversion approaches the gelation conversion level. This model has been applied to most thermosets, such as polyurethanes, without including the shear thinning effects (the parameter, n, is set equal to 1). However, for rubbers, shear thinning effects become important.

This rheokinetics model can be loosely interpreted as a function of the shear-rate-dependent part (Cross-Arrhenius) and a conversion-dependent part.

In the equation, is the conversion level determined by curing kinetics. gel is the conversion level at which the polymer gels, and the viscosity becomes infinity. * represents the shear stress at which the shear-thinning behavior begins to occur. T_b represents the temperature sensitivity of the zero-shear rate viscosity, ₀(T). B is a pre-exponential factor that fixes the level of ₀(T). C₁ and C₂ are the conversion-dependent constants.

The rheokinetics data are obtained by following the standard method ASTM D4473 for measuring the cure behavior of thermosetting resins using dynamic mechanical procedures. A dynamic mechanical spectrometer typically is used for this purpose.

A frequency scan is made at low temperature (prior to curing) to determine the shear dependence of viscosity. This yields the Cross-Arrhenius model constants.

Later, temperature sweeps are made at different temperature rates using a single frequency. The scans are continued as far into the curing process as possible. The resulting torque transmitted through the test specimen is measured by a transducer. The dynamic storage modulus (G'), dynamic loss modulus (G") and the complex viscosity measurements are computed based on the measured torque.

The gelation conversion is determined based on the second G', G" crossover.

From the curing kinetics data, the conversion levels at different temperatures are known. Based on this data, as well as the rheokinetic measurements mentioned above, the ratio of complex viscosity and shear-rate viscosity can be plotted against conversion level. The model constants can then be derived by fitting this data.

T-CODE#

01352

Equation

is the shear rate

n, *, B, T_b, C₁, and C₂ are the viscosity model constants
Order of parameters in the data set

[n, *, B, T_b, C₁, C₂]

Units (SI)

n, C₁, C₂: dimensionless
*: Pa
B: Pa-s
T_b: K

Reactive polymer viscosity II

This data set specifies the twelve constants of the Reactive Polymer Viscosity model (II). This model is used exclusively for reaction injection molding materials, such as PA6 and Dicyclopentadiene.

The constants are derived from measurements of complex viscosity using oscillatory measurements and curing kinetics data.

T-CODE#

01354

Equation

Order of parameters in the data set

[XMP, XMI, AP, AI, EP, EI, BP, BI, C₁, C₂, C₃, C₄]

Units (SI

XMP, XMI, C₁, C₂, C₃, C₄: dimensionless
AP, AI: Pa-s
EP, EI: 1/K
BP, BI: Pa-s

Exp juncture loss

This data set specifies the two constants of the juncture-loss model.

When the polymer melt encounters any sudden contraction of diameter in the melt delivery system (runners or gates), the pressure drop will be higher, and this should be accounted for in the analysis.

C-MOLD Filling implements an internally defined model when the runner diameters contract by a ratio of two or greater. This exp juncture loss model accounts for the extra pressure effects and will override the internal (default) model if it is specified.

The pressure losses are lumped as an end pressure term, P_e, such that the wall shear stress, w, can now be expressed as

or

Without taking into account these extra juncture losses, the wall shear stress would be directly proportional to the pressure drop, which is not the case when the melt flows through runners of different diameters.

The following correlation is found to work fairly well for most polymer materials:

C₁ and C₂ in the above model are determined by conducting experiments with capillaries of different L/D ratios (performing the Bagley correction). Suggested values of C₁ and C₂ for various generic materials are tabulated in C-MOLD Process Estimator User's Guide, and C-MOLD Filling & Post-Filling User's Guide.

T-CODE#

01360

Units (SI)

C₁: Pa^{1 - C2}
C₂: dimensionless

Warning

Accurate material characterization (Bagley correction to the capillary viscosity data) is necessary to obtain these constants and to be used in the analysis.

N-th order kinetics w/ induction time

This data set specifies the eight constants of the N-th order curing kinetics model with exponential, isothermal induction time. This is the default model used in C-MOLD Reactive Molding.

The conversion or degree of cure at a given time, t, is defined as the ratio of total heat of reaction release at time t to the total heat of reaction.

Some resins undergo an induction period before proceeding to the curing stage. This induction time is described in terms of an induction model. Fast curing resins such as rubber molding compounds, epoxies, or polyurethanes, have no induction time.

This curing kinetics model is of a general form and has been applied to different reactive resins.

In the equations, B₁ and B₂ are the constants associated with the induction time, t_z. K₁ and K₂ are the reaction rate constants; A₁, and A₂ are the pre-exponential Arrhenius constants; and E₁ and E₂ are the energies of activation. The parameters, m and n, are associated with the reaction rate order, which is m + n.

If m + n = 2, then this model becomes a second-order curing kinetics model.

Differential scanning calorimetry is one of the methods employed to characterize the curing kinetics. The sample is heated at different heating rates, and the heat of reaction is determined. The conversion levels are calculated based on the partial areas method. The constants are obtained by non-linear fitting of the DSC data to this model.

T-CODE#

01400

Equation

Total heat of reaction: H

Isothermal induction time:

Isothermal curing kinetics:

Order of parameters in the data set

[H, B₁, B₂, m, n, A₁, A₂, E₁, E₂]

Units (SI)

H: J/kg
B₁: s
B₂, E₁, E₂: K
m, n: dimensionless
A₁, A₂: 1/s

Transition temperature

This data set is the temperature that corresponds to the polymer freeze temperature. At this temperature, the melt-to-solid transition occurs. This is distinct from the no-flow temperature. The polymer (and stresses) freeze at the melt-to-solid transition temperature and not at the no-flow temperature.

The transition temperature corresponds to the glass-transition temperature (T_g) for amorphous materials and to the crystallization temperature (T_c) for semi-crystalline polymers.

It is crucial to have a good estimate of the polymer transition temperature, as it affects the residual stress, shrinkage, and warpage measurements.

The transition points obtained from pvT, specific heat, thermal conductivity, and viscosity measurements are not usually close enough to have confidence in the data. This is because of current limitations on measurement techniques, as well as the cooling-rate dependence of this value in the case of semi-crystalline polymers.

The best method to determine the transition temperature is by a DSC cooling scan, following the standard method ASTM D3418 (Transition Temperatures of Polymers by Thermal Analysis).

If this data is not readily available, the following correlations can be used to determine the transition temperature based on handbook values of glass transition temperature (T_g), melting temperature (T_m), Vicat temperature, or heat deflection temperature (the last two are other measures of heat resistance of polymers):

For amorphous materials:

For semi-crystalline materials:

A simple rule of thumb is to use the lowest available temperature from all sources of data.

T-CODE#

01500

Units (SI)

K

Warning

The transition temperature is a very important physical property, and the proper value has to be used for running the analysis. Using incorrect values or estimated values might lead to erroneous results, especially in the shrinkage and warpage analysis.

Gelation conversion

This data set specifies the conversion (or cure) level at which the polymer gels, and the viscosity becomes infinity.

The polymer no longer flows at the gelation point. After the gelation point is reached, the cross-linking increases slowly at first and then rapidly at higher conversion levels.

The gelation point gives an estimation of the mold-filling limits in the case of reaction injection molding.

The standard method ASTM D4473 (Standard Practice for Measuring the Cure Behavior of Thermosetting Resins using Dynamic Mechanical Procedures) is used for determining the gelation conversion. The determination of the gelation conversion is based on the second G', G" crossover. (G' and G" are the dynamic storage modulus and dynamic loss modulus, respectively, which are measured by the mechanical spectrometer). They are plotted against time at a single frequency and a controlled temperature rate. Knowing the time at crossover and temperature, the corresponding conversion level can be determined from the curing kinetics data. This conversion level is taken to be the gelation conversion.

T-CODE#

01502

Iso elastic tensor

This data set specifies the elongational modulus (E) and the Poisson's ratio () for isotropic materials.

These mechanical properties are required to predict the shrinkage and warpage behavior of a molded part under various loading conditions.

The elongational (or elastic) modulus is the ratio of stress to strain in the direction of load, within the elastic range of the material. For isotropic materials, the measurement of the elongational modulus in the flow direction (E) is sufficient. A model appropriate for anisotropic materials requires measurement of this modulus both in the flow direction (E₁) and in the direction transverse to flow (E₂).

The standard method ASTM D638 (Tensile Properties of Plastics) is used to measure the elongational modulus. A tensile testing machine equipped with an extensometer is used. Specimens are cut in the flow and transverse-to-flow directions and subjected to a constant rate of elongation as the method of loading.

The Poisson's ratio () is defined as the ratio of lateral (or transverse) contraction strain to the longitudinal strain. This measurement is made at room temperature. A model appropriate for anisotropic materials requires measurement of two Poisson's ratios: ₁₂ (ratio of transverse-direction strain to longitudinal strain) and ₂₃ (ratio of strain in thickness direction to transverse-direction strain).

The standard method ASTM E132 (Poisson's Ratio at Room Temperature) is used to measure this mechanical property using a tensile testing machine.

The stress-strain behavior of a material that exhibits linear elasticity is described mathematically by the generalized Hooke's Law:

[]ij = [C]ijkl x []kl

where []ij refers to the nine components of the stress tensor, []k_l refers to the nine components of the strain tensor, and [C]ijkl is the elasticity, the components of which are called the elastic constants of the material.

Making use of certain symmetry conditions and transformation laws for the elasticity tensor, it can be reduced from an initial 81 components to 18 components, of which only nine are non-zero. With this reduction, the generalized Hooke's Law can be re-written as:

[]i = [C]ij x []j

i, j = 1, 2, 3, 4, 5, 6

The components of []i are ₁, ₂, ₃, ₂₃, ₃₁, and ₁₂. The corresponding components of []j are ₁, ₂, ₃, ₂₃, ₃₁, and ₁₂. and are the shear stress and shear strain, respectively. 1, 2, and 3 are the principal directions.

[C]ij is also called the stiffness matrix. The elements of this matrix can be easily determined by a simple, stress-strain analysis. The elements can be expressed in terms of material properties E, , and G (shear modulus) in the following manner:

where

The three material properties are related in the following way:

where G is the shear modulus of the material.

The bulk modulus of elasticity, , is defined by:

where P is the hydrostatic pressure. The sum of terms in the above equation represents the change in volume per unit volume, or dilation.

T-CODE#

01600
Order of parameters in the data set

[E, ]

Units (SI)

E: Pa
: dimensionless
Approximate order of magnitude of E and

E ~ 10⁹ Pa
0 < < 0.5 for isotropic materials

Warning

These constants are to be used for isotropic materials only.

Fiber-filled or crystalline regions introduce anisotropy. In these cases, the transversely isotropic material model (T-CODE 01602) must be used. If transversely isotropic material constants are not available, these isotropic constants can be used for shrinkage and warpage calculations only as a first approximation.

Transversely isotropic elastic tensor

This data set specifies the five constants of the transversely isotropic material model.

These constants are the elongational modulus in the flow direction (E₁) and transverse direction (E₂), Poisson's ratios in the flow and transverse directions (₁₂ and ₂₃), and the shear modulus (G).

These mechanical properties are required to predict the shrinkage and warpage behavior of a molded part under various loading conditions.

The nature of flow determines molecular and fiber orientations. These orientation distributions lead to anisotropy in the molded part. Anisotropy varies with the location of a material point on the plane of a part and through its thickness. As a first approximation, the material can be assumed to be transversely isotropic at a given planar location, i.e., it is assumed that there exists a unique axis, perpendicular to which the material planes exhibit isotropy (in other words, properties transverse to the flow direction are isotropic).

The elongational (or elastic) modulus is the ratio of stress to strain in the direction of load, within the elastic range of the material. A model appropriate for anisotropic materials requires measurement of this modulus both in the flow direction (E₁) and in the direction transverse to flow (E₂).

The standard method ASTM D638 (Tensile Properties of Plastics) is used to measure the elongational modulus. A tensile testing machine equipped with an extensometer is used. Specimens are cut in the flow and transverse-to-flow directions and subjected to a constant rate of elongation as the method of loading.

The Poisson's ratio () is defined as the ratio of lateral (or transverse) contraction strain to the longitudinal strain. This measurement is made at room temperature. A model appropriate for anisotropic materials requires measurement of two Poisson's ratios: ₁₂ (ratio of transverse-direction strain to longitudinal strain) and ₂₃ (ratio of strain in thickness direction to transverse-direction strain).

The standard method ASTM E132 (Poisson's Ratio at Room Temperature) is used to measure this mechanical property using a tensile testing machine.

The shear modulus is the ratio of shear stress to shear strain. A rail shear test method normally is used to determine this property. The technique uses a test fixture mounted in a level loading frame. Specimens (in the form of molded plaques) are machined to fit the fixture, with round end profiles to minimize end effects and produce a homogenous stress field. The specimen is mounted in the test fixture and bolted in position between the rails. An extensometer is placed on the specimen between the rails, with needle point arms at 45°° to the direction of loading. Loading is applied to the specimen and the shear strain is monitored by the extensometer. This is repeated in each of the four positions and the average value of G is calculated:

G = /

Shear stress, = P/2

where P is the load.

Shear strain, = 2 x 45°

where °is the 45°° strain.

Anisotropy in the shear modulus is so small that it might be neglected.

The transversely isotropic material model has five independent elastic constants (E₁, E₂, ₁₂, ₂₃, and G). The general stress-strain relations for this case can be written as:

[]i = [C](-1)ij x []j

i, j = 1, 2, 3, 4, 5, 6

The components of []i are ₁, ₂, ₃, ₂₃, ₃₁, and ₁₂. The corresponding components of []j are ₁, ₂, ₃, ₂₃, ₃₁, and ₁₂. and are the shear stress and shear strain, respectively. 1, 2, and 3 are the principal directions.

[C]^-1 is also called the compliance matrix. The elements of this matrix can be determined easily by a simple, stress-strain analysis. The elements can be expressed in terms of material properties E₁, E₂, ₁₂, ₂₃, and G (shear modulus) in the following manner:

T-CODE#

01602
Order of parameters in the data set

[E₁, E₂, ₁₂, ₂₃, G]

Units (SI)

E₁, E₂, G: Pa
₁₂, ₂₃: Dimensionless
Approximate order of magnitude of E1, E2

10⁹ Pa

Warning

These material constants must be used for anisotropic materials. If these constants are not available for a particular grade of resin, then the constants for generic grades may be used as a first approximation. These generic constants are included in C-MOLD Database.

Isotropic viscoelastic-elastic tensor w/ WLF

This data set specifies the parameters for the isotropic viscoelastic tensor model with the WLF form of shift function, which is used in C-MOLD Residual Stress.

In this model, the polymer melt is assumed to be an amorphous, isotropic, thermo-rheologically simple, viscoelastic material, whose dilational behavior is elastic.

Thermo-rheologically simple behavior means that the time-variant modulus of the material at different temperatures can be derived from a single master-curve of material behavior at some reference temperature. This is carried out by employing a time-temperature shift function that can be represented in terms of a WLF equation at high temperatures:

GT(t) = GT0 x a(T)

where GT and GT₀ are the shear relaxation moduli at temperature T and reference temperature T_ref, respectively, and a(T) is the WLF shift function:

where c₁, c₂ are universal constants.

It was found by Williams, Landel, and Ferry that the above empirical expression for the shift function was valid for many polymeric materials in the temperature range:

Tg < T < (Tg + 100)

where T_g is the glass transition temperature.

The shift function is very large for temperatures higher than T_g, which allows the material to respond quickly to applied disturbances. It is very small at lower temperatures (stress levels introduced into the material decay more slowly).

The shift in the master curve to obtain the response function at different temperatures is only along the horizontal (time or temperature) axis.

The following parameters are required for this model:

Reference temperature: T_ref

Shift function constants: c₁, c₂

Bulk modulus of the material:

Material time instants: ₁, ₂,, _n (The material time accounts for the temperature dependence of the material response rate; it can be expressed as an integral (between the limits 0 and elapsed time, t) of the WLF shift function).

Shear modulus at various material time instants: G(₁), G(₂),, G(_n)

A thermo-mechanical, constitutive equation is used for the stress calculations as a function of temperature and time. It relates the components of the Cauchy-stress tensor (as a function of temperature and time) and the linear strain tensor through the viscoelastic relaxation-modulus tensor. Assumption of material isotropy and elasticity leads to many simplifications and a further reduction in the number of viscoelastic relaxation moduli coefficients.

The components of the "reduced" viscoelastic moduli obtained after simplifications mentioned above can be expressed in terms of bulk modulus and shear modulus as follows:

where

The elongational modulus (E) and Poisson's ratio () can be expressed in terms of the bulk modulus and shear modulus as follows:

T-CODE#

01603
Order of parameters in the data set

[T_ref, C₁, C₂, , ₁, G(₁), ₂, G(₂), ]

Units (SI)

T_ref, C₂: K
, G(): Pa
: s

Warning

These material constants are very difficult to obtain. Because of this, caution should be exercised when using this data set for stress analysis.

Isotropic viscoelastic tensor w/ WLF

This data set is not used currently in C-MOLD analyses.

T-CODE#

01604

Transversely isotropic viscoelastic tensor w/ WLF

This data set specifies the parameters for the isotropic viscoelastic tensor model with WLF form of shift function, which is used in C-MOLD Residual Stress.

In this model, the polymer melt is assumed to be an amorphous, isotropic, thermo-rheologically simple, viscoelastic material.

Thermo-rheologically simple behavior means that the time-variant modulus of the material at different temperatures can be derived from a single master-curve of material behavior at some reference temperature. This is carried out by employing a time-temperature shift function that can be represented in terms of a WLF equation at high temperatures:

GT(t) = GT0 x a(T)

where GT and GT₀ are the shear relaxation moduli at temperature T and reference temperature T_ref, respectively and a(T) is the WLF shift function:

where c₁, c₂ are universal constants.

It was found by Williams, Landel, and Ferry that the above empirical expression for the shift function was valid for many polymeric materials in the temperature range:

Tg < T < (Tg + 100)

where T_g is the glass transition temperature.

The shift function is very large for temperatures higher than T_g, which allows the material to respond quickly to applied disturbances. It is very small at lower temperatures (stress levels introduced into the material decay more slowly).

The shift in the master curve to obtain the response function at different temperatures is only along the horizontal (time or temperature) axis.

The following parameters are required for this model:

Reference temperature: T_ref

Shift function constants: c₁, c₂

Shear modulus of the material: G

Material time instants: ₁, ₂,, n

The material time accounts for the temperature dependence of the material response rate; it can be expressed as an integral (between the limits 0 and elapsed time, t) of the WLF shift function).

A thermo-mechanical constitutive equation is used for stress calculations as a function of temperature and time. It relates the components of the Cauchy-stress tensor and the linear strain tensor through the viscoelastic relaxation-modulus tensor. Assumption of transverse isotropy leads to many simplifications and a further reduction in the number of viscoelastic relaxation moduli coefficients.

The components of the "reduced" viscoelastic moduli (which are functions of the material time, ) obtained after the simplifications mentioned above is expressed as:

The above components of the viscoelastic relaxation moduli are further expressed as response functions, which are evaluated by numerical quadrature. Computational effort is further reduced by expanding the relaxation moduli in terms of Prony series.

Further mathematical details involved in this calculation of residual stresses are too involved and are not presented here. Interested users can refer to the various references mentioned in C-MOLD Shrinkage & Warpage User's Guide.

T-CODE#

01605
Order of parameters in the data set

[T_ref, c₁, c₂, G, C₅₅(₁), C₁₁(₁), C₁₂(₁), C₂₂(₁),
C₂₃(₁), ₂, ]

Units (SI)

T_ref, c₂: K
C _IJ (₁), G: Pa
₁: s

Mooney-Rivlin hyperelastic

This data set specifies the constants of the Mooney-Rivlin hyperelastic model for C-MOLD Blow Molding & Thermoforming.

In the most general terms, thermoplastic materials exhibit viscoelastic behavior at elevated temperatures. In this case, the strains that develop in the material when a load is applied are a function of both the history of the loading and the magnitude of the load.

However, experimental evidence exists which shows that above the glass transition temperature, T_g, the polymer material behavior is nonlinear elastic (rubber-like), especially at high strain rates. This is attributed to chain rotation and uncoiling of the long polymer molecules with very little viscous effects.

The assumption of nonlinear elastic behavior greatly simplifies the formulation of the finite-element equations. The two most commonly used constitutive equations to model this behavior are the Mooney-Rivlin formulation and the Ogden formulation. Both these formulations have been developed for an ideally elastic solid that possesses a stress potential.

In the Mooney-Rivlin formulation, it is assumed that the strain energy function, W, can be expressed as a polynomial function of the invariants of the deformation tensor, I₁ and I₂ (or rather as polynomial function of (I₁ - 3) and (I₂ - 3), such that the stresses are zero when there is no strain).

The generalized Mooney-Rivlin form of the strain energy function is given by:

A_ij are the empirically determined constants; and A₀₀ = 0, since W = 0 in the undeformed state.

The material properties are specified for each polymer zone.

The Mooney-Rivlin constants have been determined experimentally for a number of materials.

Once the strain energy function is known, the stress tensor relationships can be determined.

One of the drawbacks of this formulation is that the expression for the stress is a highly non-linear function of the stretch, even for simple elongation.

T-CODE#

01610
Order of parameters in the data set

[0, A₀₁, A₀₂,, A₁₀,, A₃₀, A₃₁, A₃₂, A₃₃]

Units (SI)

A₀₁, A₀₂,, A₁₀,, A₃₀, A₃₁, A₃₂, A₃₃: Pa

Warning

It is recommended that the Ogden material constants (T-CODE 01620 or 01621) be used in the analysis, as those models provide better fit to the experimental stress-strain data.

Tabulated Mooney-Rivlin hyperelastic

This data set specifies the tabulated constants of the Mooney-Rivlin hyperelastic model at various temperatures for C-MOLD Blow Molding & Thermoforming.

In the most general terms, thermoplastic materials exhibit viscoelastic behavior at elevated temperatures. In this case, the strains that develop in the material when a load is applied are a function of both the history of the loading and the magnitude of the load.

However, experimental evidence exists which shows that above the glass transition temperature, T_g, the polymer material behavior is nonlinear elastic (rubber-like), especially at high strain rates. This is attributed to chain rotation and uncoiling of the long polymer molecules with very little viscous effects.

The assumption of nonlinear elastic behavior greatly simplifies the formulation of the finite-element equations. The two most commonly used constitutive equations to model this behavior are the Mooney-Rivlin formulation and the Ogden formulation. Both these formulations have been developed for an ideally elastic solid that possesses a stress potential.

In the Mooney-Rivlin formulation, it is assumed that the strain energy function, W, can be expressed as a polynomial function of the invariants of the deformation tensor, I₁ and I₂ [or rather as polynomial function of (I₁ - 3) and (I₂ - 3), such that the stresses are zero when there is no strain].

The generalized Mooney-Rivlin form of the strain energy function is given by:

A_ij are the empirically determined constants; and A₀₀ = 0, since W=0 in the undeformed state.

The material properties are specified corresponding to a particular temperature and for each polymer zone. The tabulated data, if available, provide a better representation of the material behavior.

The Mooney-Rivlin constants have been determined experimentally for a number of materials.

Once the strain energy function is known, the stress tensor relationships can be determined.

One of the drawbacks of this formulation is that the expression for the stress is a highly non-linear function of the stretch, even for simple elongation.

T-CODE#

01611
Order of parameters in the data set

[T₁, 0, A₀₁,, A₁₀,, A₃₀,, A₃₃, T₂, 0, A₀₁,, A₃₃,]

Units (SI)

T: K
A₀₁,, A₃₃: Pa

Warning

It is recommended that the Ogden material constants (T-CODE 01620 or 01621) be used in the analysis, as those models provides better fit to the experimental stress-strain data.

Ogden hyperelastic

This data set specifies the constants of the Ogden hyperelastic model for C-MOLD Blow Molding & Thermoforming.

In the most general terms, thermoplastic materials exhibit viscoelastic behavior at elevated temperatures. In this case, the strains that develop in the material when a load is applied are a function of both the history of the loading and the magnitude of the load.

However, experimental evidence exists which shows that above the glass transition temperature, T_g, the polymer material behavior is nonlinear elastic (rubber-like), especially at high strain rates. This is attributed to chain rotation and uncoiling of the long polymer molecules with very little viscous effects.

The assumption of nonlinear elastic behavior greatly simplifies the formulation of the finite-element equations. The two most commonly used constitutive equations to model this behavior are the Mooney-Rivlin formulation and the Ogden formulation. Both these formulations have been developed for an ideally elastic solid that possesses a stress potential.

In the Ogden hyperelastic formulation, the strain energy function, W, is expressed as a function of the principal stretches. The strain energy is written as an expansion in the principal stretches, ₁, ₂, and ₃, and is of the form:

where (i) and (i) are experimentally determined constants. They can be non-integer and negative, with the only restriction being that the total summation above must result in a positive strain energy function.

n is the number of modes of the Ogden model (n < 9).

Since the Ogden model is represented directly in terms of the stretches, , instead of the invariants of the rate of deformation tensor as in the Mooney-Rivlin formulation, the physical interpretation of the stress-strain relationship is much easier. Another advantage of the Ogden formulation is that it provides a better fit to the experimental stress-strain data.

It is recommended that a higher order (n > 2) Ogden model be used in the analysis.

Once the strain energy function is known, the stress tensor relationships can be determined.

T-CODE#

01620
Order of parameters in the data set

[(i), (i)] (for each mode)

Units (SI)

: Pa
: dimensionless

Warning

It is recommended that a higher order (n > 2) Ogden model be used in the analysis.

Tabulated Ogden hyperelastic

This data set specifies the tabulated constants of the Ogden hyperelastic model at various temperatures for C-MOLD Blow Molding & Thermoforming.

In the most general terms, thermoplastic materials exhibit viscoelastic behavior at elevated temperatures. In this case, the strains that develop in the material when a load is applied are a function of both the history of the loading and the magnitude of the load.

However, experimental evidence exists which shows that above the glass transition temperature, T_g, the polymer material behavior is nonlinear elastic (rubber-like), especially at high strain rates. This is attributed to chain rotation and uncoiling of the long polymer molecules with very little viscous effects.

The assumption of nonlinear elastic behavior greatly simplifies the formulation of the finite-element equations. The two most commonly used constitutive equations to model this behavior are the Mooney-Rivlin formulation and the Ogden formulation. Both these formulations have been developed for an ideally elastic solid that possesses a stress potential.

In the Ogden hyperelastic formulation, the strain energy function, W, is expressed as a function of the principal stretches. The strain energy is written as an expansion in the principal stretches, ₁, ₂, and ₃, and is of the form:

where (i) and (i) are experimentally determined constants. They can be non-integer and negative, with the only restriction being that the total summation above must result in a positive strain energy function.

n is the number of modes of the Ogden model (n < 9)

Since the Ogden model is represented directly in terms of the stretches, , instead of the invariants of the rate of deformation tensor as in the Mooney-Rivlin formulation, the physical interpretation of the stress-strain relationship is much easier. Another advantage of the Ogden formulation is that it provides a better fit to the experimental stress-strain data.

It is recommended that a higher order (n > 2) Ogden model be used in the analysis.

Once the strain energy function is known, the stress tensor relationships can be determined.

T-CODE#

01621
Order of parameters data set

[T₁, (1), (1), ,(n), (n), T₂, (1),
(1),, (n), (n),, T_n,]

Units (SI)

T: K
: Pa
: dimensionless

Warning

It is recommended that a higher order (n > 2) Ogden model be used in the analysis.

Isotropic thermal expansion coefficient

This data set specifies the thermal expansion coefficient of isotropic materials.

This is required in C-MOLD Residual Stress, in which the material response to change in temperature is taken into account.

The thermal expansion coefficient, , is defined as:

where L is the change in length of the specimen of original length L₀ when subjected to a change in temperature, T.

The value for isotropic materials is the same in all directions.

The standard method ASTM D696 (Coefficient of Linear Thermal Expansion of Plastics) is adopted to measure this property. The apparatus used is a quartz tube dilatometer. The specimen is prepared and placed at the bottom of the outer dilatometer tube, with the inner one resting on the specimen. The dial gauge, firmly attached to the outer tube, is placed in contact with the top of the inner tube so as to measure variations in the length of the specimen with changes in temperature.

Temperature changes are brought about by immersing the outer tube in a liquid bath at the desired temperature. The coefficient of thermal expansion is measured using the formula mentioned above.

T-CODE#

01700

Units (SI)

1/K
Approximate order of magnitude (for most polymers)

1.0 x 10^-4 - 1.0 x 10^-6 1/K

Warning

If the material is anisotropic, then ALPHA values in both the flow and transverse-to-flow directions must be used in the analysis.

if this isotropic thermal expansion coefficient is not available for a particular grade of resin, then the value for the generic grade may be used as a first approximation. This generic data is available in C-MOLD Database.

Transversely isotropic thermal expansion coefficient

This data set specifies the thermal expansion coefficient of transversely isotropic materials.

This is required in C-MOLD Residual Stress, in which the material response to change in temperature is taken into account.

Transversely isotropic means that the material properties transverse to the flow direction are isotropic.

The thermal expansion coefficient, , is defined as:

where L is the change in length of the specimen of original length L₀ when subjected to a change in temperature, T.

The standard method ASTM D696 (Coefficient of Linear Thermal Expansion of Plastics) is adopted to measure this property. The apparatus used is a quartz tube dilatometer. The specimen is prepared and placed at the bottom of the outer dilatometer tube, with the inner one resting on the specimen. The dial gauge, firmly attached to the outer tube, is placed in contact with the top of the inner tube so as to measure variations in the length of the specimen with changes in temperature.

Temperature changes are brought about by immersing the outer tube in a liquid bath at the desired temperature. The coefficient of thermal expansion is measured using the formula mentioned above.

For transversely isotropic materials, samples are cut both parallel to the flow direction as well as normal to the flow direction. The corresponding measurements are ₁ and ₂, respectively.

T-CODE#

01702
Order of parameters in the data set

[₁, ₂]

Units (SI)

1/K
Approximate order of magnitude (for most polymers)

1.0 x 10^-4 - 1.0 x 10^-6 1/K

Warning

If the values of ₁ and ₂ are not available for a particular grade of resin, then the value for the generic grade may be used as a first approximation. This generic data is available in C-MOLD Database.

Polymer material description

This data set specifies the name of the polymer material used in C-MOLD analyses.

Once a polymer material is selected from C-MOLD Database, its name is automatically written out to the material properties file. Alternately, it can be specified when creating or editing the material properties file.

It is not necessary to specify this data set to execute any C-MOLD analyses.

T-CODE#

01999

Second Polymer Material: 02000-02999

Second polymer material description

This data set specifies the name of the second polymer material used in C-MOLD Co-Injection.

Once a polymer material is selected from C-MOLD Database, its name is automatically written out to the material properties file. Alternately, it can be specified when creating or editing the material properties file.

It is not necessary to specify this data set to execute any of the C-MOLD analyses.

T-CODE#

02999

Fiber Material: 03000-03999

Constant fiber density

This data set specifies the value of the constant fiber density for C-MOLD Fiber Orientation and for C-MOLD Reactive Molding when simulating resin transfer molding (RTM) or structural reaction injection molding (SRIM).

The physical properties of the fiber are required, in addition to the material properties of the polymer.

C-MOLD Fiber Orientation assumes a default fiber density value, which is that of a glass fiber (2500 kg/m³).

T-CODE#

03000

Units (SI)

kg/m³
Approximate order of magnitude (for most glass fibers)

2500 kg/m³

Default value

2500 kg/m³ (in C-MOLD Fiber Orientation)

Constant fiber specific heat

This data set specifies the value of the constant fiber specific heat for C-MOLD Reactive Molding when simulating resin transfer molding (RTM) or structural reaction injection molding (SRIM).

The nature of resin flow and its temperature distribution during filling depends, not only on the initial melt temperature, velocity, thermal diffusivity, and mold-wall temperature, but also on the thermal diffusivity and initial temperature of the fiber. Thus, the physical properties of the fiber are required in addition to the material properties of the polymer.

T-CODE#

03100

Units (SI)

C_p: J/kg-K

Constant fiber thermal conductivity

This data set specifies the value of the constant fiber thermal conductivity for C-MOLD Reactive Molding when simulating resin transfer molding (RTM) or structural reaction injection molding (SRIM).

The nature of resin flow and its temperature distribution during filling depends not only on the initial melt temperature, velocity, thermal diffusivity, and mold-wall temperature, but also on the thermal diffusivity and initial temperature of the fiber. Thus, the physical properties of the fiber are required in addition to the material properties of the polymer.

T-CODE#

03200

Units (SI)

k: W/m-K

Fiber isotropic elastic tensor

This data set specifies the value of the constant fiber mechanical properties for C-MOLD Fiber Orientation.

The physical properties of the fiber are required in addition to the material properties of the polymer.

The orientation state of the fibers and the fiber volume fraction greatly influence the thermo-mechanical properties of composites. The properties of the oriented fiber-filled composite can be generated from the orientation state (determined from the fiber orientation analysis) and properties of the unidirectionally reinforced composites. This is done by using an orientation averaging scheme, i.e., by taking the weighted average of the unidirectional properties over all fiber directions, with the orientation distribution function as the weighting function.

The Halpin-Tsai equation is used to estimate the transversely-isotropic mechanical properties E₁₁, E₂₂, G₁₂, or G₂₃ (where E and G are the elastic modulus and shear modulus, respectively) of a unidirectional composite, based on the fiber volume fraction.

A mixture-rule is applied to predict the Poisson's ratio.

T-CODE#

03600
Order of parameters in the data set

[E, ]

Units (SI)

E: Pa
: dimensionless
Approximate order of magnitude of E (for most glass fibers)

72.4 GPa
Approximate range of MU (for most glass fibers)

0 < < 0.5

Default value

E: 7 x 10¹⁰ Pa
: 0.23

Warning

The default values will be used if the actual values are not specified.

Fiber isotropic thermal expansion coefficient

This data set specifies the value of the constant fiber isothermal expansion coefficient for C-MOLD Fiber Orientation.

The physical properties of the fiber are required in addition to the material properties of the polymer.

The orientation state of the fibers and the fiber volume fraction greatly influence the thermo-mechanical properties of composites. The properties of the oriented fiber-filled composite can be generated from the orientation state (determined from the fiber orientation analysis) and properties of the unidirectionally reinforced composites. This is done by using an orientation averaging scheme, i.e., by taking the weighted average of the unidirectional properties over all fiber directions, with the orientation distribution function as the weighting function.

The longitudinal and transverse thermal expansion coefficients for the unidirectional composite are estimated using an averaging scheme based on the fiber volume fraction.

T-CODE#

03700

Units (SI)

1/K
Approximate range (for most glass fibers)

2.0 x 10^-6 - 5.0 x 10^-6 1/K

Fiber weight fraction

This data set specifies the value of the fiber weight fraction for C-MOLD Fiber Orientation.

The orientation state of the fibers and the fiber volume fraction greatly influence the thermo-mechanical properties of composites. The properties of the oriented fiber-filled composite can be generated from the orientation state (determined from the fiber orientation analysis) and properties of the unidirectionally reinforced composites. This is done by using an orientation averaging scheme, i.e., by taking the weighted average of the unidirectional properties over all fiber directions, with the orientation distribution function as the weighting function.

The correct specification of the fiber volume fraction (or weight fraction) is thus very important in determining the properties of the composite.

The fiber volume fraction (vol) and the fiber weight fraction (wt) are related as follows:

where f and p are the densities of fiber and the polymer, respectively.

If the fiber weight fraction is zero, then the fiber orientation analysis will not be performed.

The default fiber weight fraction is zero.

T-CODE

03900

Units (SI)

Dimensionless

Range

0 wt < 1

Default value

0

Warning

The correct specification of the fiber volume fraction (or weight fraction) is very important in determining the properties of the composite.

This parameter has to be set to an non-zero value to perform C-MOLD Fiber Orientation.

Fiber aspect ratio

This data set specifies the fiber aspect ratio (length to diameter ratio, L/D) of fibers for C-MOLD Fiber Orientation Analysis.

The fiber aspect ratio influences the fiber-fiber interactions (which is taken into account in the evolution equation for fiber orientation tensor) as well as the properties of the polymer composite.

It is thus very important to specify the correct value of the fiber aspect ratio.

T-CODE#

03910

Units (SI)

Dimensionless

Default value

25

Warning

It is very important to specify the correct value of the fiber aspect ratio as it influences the fiber-fiber interactions (which is taken into account in the evolution equation for fiber orientation tensor) as well as the properties of the polymer composite.

Fiber-mat porosity and permeability

This data set specifies the fiber mat porosity and permeability for C-MOLD Reactive Induction Molding Analysis.

The parameters in this data set are:

Fiber mat ID

This parameter identifies the fiber mat as defined in the finite-element mesh file. It uniquely associates the fiber mat in the geometry model with the fiber mat porosity and permeability. This feature makes C-MOLD Reactive Molding capable of simulating the resin flow through more than one kind of fiber mat. There is no need to specify the fiber mat ID for un-reinforced (empty) regions.

Porosity ()

The porosity represents the packing density of the fiber mat in the cavity. It is defined as the ratio of the void volume to the cavity volume, before the cavity is filled with the resin. The void volume is equal to the cavity volume minus the volume occupied by the reinforcement.

When layers of different types of fiber mats are used, the porosity () is calculated as follows:

where n_i is the number of layers of the ith type of fiber mat, i is the surface density, and fi is the density of the fiber mat. The latter two values can be found in the supplier's literature.

Permeability

Permeabilities in three directions are

1. K₁₁: Permeability in the first principal direction, as will be defined by the reference vector for an anisotropic fiber mat.
2. K₂₂: Permeability in the second principal direction.
3. K₁₂: Cross-permeability.
4. b: Reference thickness at measurement.

For isotropic fiber mats, K₁₁ = K₂₂, and K₁₂ = 0.

For anisotropic fiber mats, K₁₁ is not equal to K₂₂, and K₁₂ may or may not be equal to zero.

According to Darcy's law, the flow resistance encountered by the resin when it flows through the fiber mat is calculated in terms of permeability. For one-dimensional flow, Darcy's law can be written as:

where Q is the volumetric flow rate, is the resin viscosity, A is the flow cross-sectional area, P/L is the pressure drop per unit length, and K_x is the permeability.

Permeability depends on the network structure of the fiber mat. The larger the permeability, the more easily the fluid flows through the medium.

Permeability is measured in terms of darcy units (1 darcy = 9.86874 x 10^-13 m²).

The in-plane and transverse-to-flow structures of the fiber mat might be different, and they can create different resistances to flow. In the case of such anisotropic fiber mats, the pore area distribution shows a maximum in one direction and a minimum in a direction orthogonal to the former.

When a resin flows through such a fiber mat, the flow in the direction of maximum pore area will have the longest flow length, because it has the least flow resistance. If the pore area distribution is smooth, the in-plane melt front exhibits an elliptic pattern, the shape of which depends on the maximum and minimum pore areas. This can be characterized by the so-called permeabilities of the principal directions.

One of the principal directions corresponds to the major axis of the ellipse. This direction is denoted as the first principal direction. The second principal direction corresponds to the minor axis of the ellipse.

The melt front takes a circular shape in the case of isotropic fiber mats.

Due to small ratio of the gap thickness to the planar dimensions in many RTM and SRIM applications, these processes are often modeled with two-dimensional flow. In such cases, the in-plane permeabilities are more important than the transverse permeability. The latter is used to characterize the flow of autoclave composite processing.

The in-plane permeabilities can be measured by a center-gated disk flow or a slit flow.

In the case of center-gated disk flow, a Newtonian fluid of known physical properties is driven through the preform at constant pressure and the melt-front advancement as a function of time is recorded by a video camera. The in-plane permeabilities are determined by correlating the experimental data with the theoretical equation of the melt front advancement as a function of time. This method, while requiring more data collection and more sophisticated experimental techniques, is a very reasonable method of predicting permeabilities, especially for anisotropic preforms.

In the case of slit flow, the anisotropic fiber mat is arranged so that one of its principal axes is parallel to the flow direction. The permeability of this direction can be calculated using the one-dimensional Darcy's law mentioned above, and the experimental data of pressure drop versus flow rate. Since Darcy's law is valid only in the creeping flow range, the permeability must be determined by the slope at the flow rate approaching zero.

The principal axis of the fiber mat can be predicted from its stitch structure or from a short-shot of the disk flow. This method is simple for experiments and data correlation. However, the channeling effect that occurs at the side walls can cause significant errors in measurement for a slit die with narrow width. This error can be reduced by using a wider die, but plug flow might not be able to be preserved.

If the fiber mat preform is the same as that used for measurements, then the permeability data can be used directly in the simulation.

In many applications, the permeability of the particular preform might not be available, but we might know the permeability of each composite layer. The "effective permeability" of the preform can be calculated by the following mixing rule:

where h is the cavity thickness, and h_j and K_j are the thickness and permeability of the jth layer fiber mat, respectively.

C-MOLD Reactive Molding can handle at most one anisotropic fiber mat, and multiple isotropic fiber mats..

The reference thickness at measurement is designated as b. If the cavity thickness at molding is different from the reference thickness specified in this data set, the porosity and permeability data will be internally modified by the analysis, based on the assumptions that the thickness variation in the cavity is not too large from the reference thickness, and the porosity is between 0.4 - 0.7. Otherwise, errors in the prediction could be introduced, or the analysis might be terminated due to fiber over-packing as a result of using improper values of the fiber mat properties.

T-CODE#

03920
Order of parameters in the data set

[id, , K₁₁, K₂₂, K₁₂, b]

Units (SI)

: dimensionless
K₁₁, K₂₂, K₁₂: m²
b: m

Warning

C-MOLD Reactive Molding can handle at most one anisotropic fiber mat, and multiple isotropic fiber mats.

The reference thickness at measurement is designated as b. If the cavity thickness at molding is different from the reference thickness specified in this data set, the porosity and permeability data will be internally modified by the analysis, based on the assumptions that the thickness variation in the cavity is not too large from the reference thickness, and the porosity is between 0.4 - 0.7. Otherwise, errors in the prediction may be introduced, or the analysis may be terminated due to fiber over-packing as a result of using improper values of the fiber mat properties.

Fiber material description

This data set specifies the name of the fiber used in C-MOLD Fiber Orientation, or in C-MOLD Reactive Molding when simulating resin transfer molding (RTM) or structural reaction injection molding (SRIM).

It can be specified when creating or editing a material template.

It is not necessary to specify this data set to execute any C-MOLD analyses.

T-CODE#

03999

First Coolant Material: 06000-06999

Constant coolant density

This data set specifies the value of the constant coolant density for C-MOLD Cooling.

The coolant physical properties are required in the coolant flow and heat transfer calculations. They are automatically written out in the material properties file when a coolant is selected.

T-CODE#

06000

Units (SI)

kg/m³
Approximate order of magnitude of coolant density

10³ kg/m³

Warning

If the coolant physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Constant coolant specific heat

This data set specifies the value of the constant coolant specific heat for C-MOLD Cooling.

The coolant physical properties are required in the coolant flow and heat transfer calculations. They are automatically written out in the material properties file when a coolant is selected.

T-CODE#

06100

Units (SI)

J/kg-K
Approximate order of magnitude of coolant specific heat

10³ J/kg-K

Warning

If the coolant physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Constant coolant thermal conductivity

This data set specifies the value of the constant coolant thermal conductivity for C-MOLD Cooling.

The coolant physical properties are required in the coolant flow and heat transfer calculations. They are automatically written out in the material properties file when a coolant is selected.

T-CODE#

06200

Units (SI)

W/m-K
Approximate order of magnitude of coolant thermal conductivity

0.1 W/m-K

Warning

If the coolant physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Constant coolant viscosity

This data set specifies the value of the constant coolant viscosity for C-MOLD Cooling.

The coolant physical properties are required in the coolant flow and heat transfer calculations. They are automatically written out in the material properties file when a coolant is selected.

T-CODE#

06300

Units (SI)

Pa-s

Warning

If the coolant physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Using a temperature-dependent coolant viscosity model (T-CODE 06302) might improve the accuracy of the simulation. The viscosity constants for this model are available for many coolants in C-MOLD Database.

Coolant viscosity w/ exp temperature dependence

This data set specifies the values of the coolant viscosity model with exponential temperature dependence for C-MOLD Cooling.

The coolant physical properties are required in the coolant flow and heat transfer calculations. They are automatically written out in the material properties file when a coolant is selected.

Using this temperature-dependent coolant viscosity model instead of the constant coolant viscosity improves the accuracy of the simulation. The viscosity constants for this model are available for many coolants in C-MOLD Database.

T-CODE#

06302

Equation

Order of parameters in the data set

[C₁, C₂, C₃]

Units (SI)

C₁: Pa-s
C₂, C₃: K

Warning

If the coolant physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Coolant material description

This data set specifies the name of the coolant material used in C-MOLD analyses.

Once a coolant material is selected from C-MOLD Database, its name is automatically written out to the material properties file. Alternately, it can be specified when creating or editing the material properties file.

It is not necessary to specify this data set to execute any C-MOLD analyses.

T-CODE#

06999

First Mold Material: 08000-08999

Constant mold density

This data set specifies the value of the constant mold material density for C-MOLD Cooling.

The mold material physical properties are required in the heat transfer calculations. They are automatically written out in the material properties file when a mold material is selected.

T-CODE#

08000

Units (SI)

kg/m³
Approximate order of magnitude of mold material density

10³ kg/m³

Warning

If the mold material physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Constant mold specific heat

This data set specifies the value of the constant mold material specific heat for C-MOLD Cooling.

The mold material physical properties are required in the heat transfer calculations. They are automatically written out in the material properties file when a mold material is selected.

T-CODE#

08100

Units (SI)

J/kg-K
Approximate order of magnitude of mold material specific heat

10² J/kg-K

Warning

If the mold material physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Constant mold thermal conductivity

This data set specifies the value of the constant mold material thermal conductivity for C-MOLD Cooling.

The mold material physical properties are required in the heat transfer calculations. They are automatically written out in the material properties file when a mold material is selected.

T-CODE#

08200

Units (SI)

W/m-K
Approximate order of magnitude of mold thermal conductivity

10 W/m-K

Warning

If the mold material physical properties are not specified, C-MOLD Cooling will not execute, and will return an error message.

Mold material description

This data set specifies the name of the mold material used in C-MOLD analyses.

Once a mold material is selected from C-MOLD Database, its name is automatically written out to the material properties file. Alternately, it can be specified when creating or editing the material properties file.

It is not necessary to specify this data set to execute any C-MOLD analyses.

T-CODE#

08999

Second Mold Material: 09000-09999

Second mold material description

This data set specifies the name of the second mold material used in C-MOLD analyses.

Once a mold material is selected from C-MOLD Database, its name is automatically written out to the material properties file. Alternately, it can be specified when creating or editing the material properties file.

It is not necessary to specify this data set to execute any C-MOLD analyses.

T-CODE#

09999

Data Sets Used in the Process Conditions File

Process Conditions: 10000-19999

Maximum machine clamp force

This data set defines the maximum clamp tonnage provided by the injection molding machine. In most modern injection molding machines, the clamp tonnage can be adjusted by changing the machine hydraulic pressure.

C-MOLD Filling and C-MOLD Post-Filling calculate the clamp tonnage requirement by multiplying the cavity pressure at the end of the filling stage by the projected cavity surface area on the parting plane. If this calculated clamp force exceeds the machine capacity, a warning message is issued by the analysis.

T-CODE#

10000

Units (SI)

N

Range

9.8 x 10⁴ - 6.8 x 10⁷ N (10 - 7000 ton(m))

Default Value

4.905 x 10⁷ N (5000 ton(m))

Warning

The default value of 4.905 x10⁷ N (5000 ton-m) will be used if no machine is specified. You may specify a machine by selecting one from C-MOLD Database, or you may edit the process conditions data file (filename.prc) to add the value of clamp force for your machine.

Maximum machine injection volume

This data set defines the theoretical injection volume that is provided by the machine manufacturer. This value is equal to the maximum machine injection stroke, multiplied by the cross sectional area of the barrel. The actual total injection volume will be approximately 80% of the theoretical machine maximum, because polymer shrinkage occurs.

If the total shot volume exceeds the maximum machine injection volume, then a warning message is issued by the analysis.

T-CODE#

10001

Units (SI)

m³

Default Value

0.02 m³

Warning

The default value of 0.02 m³ will be used if no machine is specified. You may specify a machine by selecting one from C-MOLD Database, or you may edit the process conditions data file (filename.prc) to add the value of maximum injection volume for your machine.

Maximum machine injection pressure

This data set defines the maximum machine injection pressure. This value is equal to the maximum hydraulic pressure available in the machine, multiplied by the ratio of cross-sectional area of the hydraulic piston to the cross-sectional area of the barrel, less any friction losses and nozzle pressure drops. A typical injection molding machine has an amplification factor of 7-10, and the friction losses can be as much as 10-20%.

If the calculated injection pressure exceeds the maximum machine injection pressure during the filling stage, a warning message is issued by the analysis. At this point, the analysis switches from flow rate control to pressure control. This value is then used as the entrance pressure until the end of the filling stage.

With a fixed entrance pressure, the actual flow rate will decrease as flow length increases. The analysis will issue a "short shot" warning message when the actual flow rate falls below 1% of the minimum specified flow rate before the cavity is completely filled.

This data set is also used to determine the absolute pack/hold pressure profile (T-CODE 10700) during the holding phase.

T-CODE#

10002

Units (SI)

Pa

Default Value

1.8 x 10⁸ Pa (180 MPa)

Warning

The default value of 1.8 x 10⁸ Pa (180 MPa) will be used if no machine is specified. You may specify a machine by selecting one from C-MOLD Database, or you may edit the process conditions data file (filename.prc) to add the value of maximum injection pressure for your machine.

Maximum machine injection rate

This data set defines the maximum machine injection rate, which is the limit of how fast the machine can inject the polymer into the mold. This value is equal to the maximum machine injection speed (linear), multiplied by the cross-sectional area of the barrel. If the flow rate at a given time step exceeds this value, a warning message is issued by the analysis.

If the specified fill time is too short, then the machine might not be able to deliver the necessary volume. In this case, the analysis maintains the injection rate at its maximum just as any real machine would do and issues a warning message. The actual fill time in this case would be longer than the specified fill time.

This data set is used as a limit for both the relative and absolute ram-speed profiles (T-CODEs 10600 and 10602).

T-CODE#

10005

Units (SI)

m³/s

Default Value

6.667 x 10^-3 m³/s

Warning

The default value of 6.667 x 10^-3 m³/s will be used if no machine is specified. You may specify a machine by selecting one from C-MOLD Database, or you may edit the process conditions data file (filename.prc) to add the value of maximum injection rate for your machine.

Machine hydraulic response time

This data set defines the machine response time to switch from one hydraulic pressure level to another during the pack/hold phase.

In practice, it is impossible to switch between hydraulic pressure levels instantaneously. The response time depends on the control scheme and the system dynamics of the hydraulic units. Most modern injection molding machines provide a close to linear transition from one holding pressure level to the next.

In C-MOLD Post-Filling, the pack/hold pressure is linearly interpolated between two pressure levels over the hydraulic response time. If the machine hydraulic response time is longer than the time interval between any two pack/hold pressure profile settings, a response time equal to half of the time interval between the settings is used.

T-CODE#

10006

Units (SI)

s

Default Value

0.2 s

Warning

The default value of 0.2 s will be used if no machine is specified. You may specify a machine by selecting one from C-MOLD Database, or you may edit the process conditions data file (filename.prc) to add the value of hydraulic response time for your machine.

Maximum gas pressure

This data set defines the maximum machine gas injection pressure capacity for C-MOLD Gas-Assisted Injection Molding.

This value is used as the reference gas pressure if the gas-pressure control option is chosen (T-CODE 11302 is set to 0). If the specified gas pressure or the calculated profiled gas pressure exceeds this value, a warning message is issued by the analysis.

If the gas-volume control option is chosen (T-CODE 11302 is set to 2), this maximum gas pressure value will be used if the calculated gas pressure exceeds this value. This is used to mimic real machine control, in which a safety valve will open to allow the release of extra gas pressure for safety reasons.

On the other hand, if the automatic gas-pressure profiling option is chosen (T-CODE 11302 is set to 1), the analysis will continue even if this maximum machine gas pressure is exceeded, allowing the gas pressure to increase above the machine's capacity in the simulation.

T-CODE#

10010

Units (SI)

Pa

Default Value

7.0 x 10⁷ Pa

Warning

The default value is taken as the maximum pressure beyond which a potential hazard might occur. Machine capabilities and safety considerations have to be taken into account before modifying this value.

Fill time

This data set specifies the time required to fill the entire cavity. After the mold closes, the molten polymer, which is maintained at a uniform temperature inside the barrel, is forced to flow through the nozzle, runner system, gate(s), and then into the cavity under controlled flow rate or pressure (depending on the control scheme of the machine).

The fill time is defined as the time needed for the polymer to fill the entire cavity. The fill time is usually short compared to the overall cycle time. However, the correct fill time is very important in controlling the pressure rise in the runners, gates, and part cavity, thereby helping to assure proper filling, good appearance, part strength, and dimensional tolerances.

A reasonable estimate of the fill time can be derived from the required cooling time of the part, which is approximately calculated as follows:

The penetration depth () of the solid, frozen layer on the mold wall is:

For the half-gap to be penetrated:

From equations (1) and (2) above, it follows that the cooling time, t, is:

Thus, knowing the nominal thickness and thermal diffusivity, it is possible to estimate the cooling time.

The fill time typically should be much less than the cooling time, to avoid premature solidification. As a rule of thumb, a good estimate of fill time should be one-tenth to one-fifth of the estimated cooling time.

The actual fill time predicted by the analysis will be equal to the specified fill time only if the entire filling stage is under ram-speed profile control. If the filling mode is switched to pack/hold pressure control before the end of filling, the process will be controlled by the specified pack/hold pressure at the entrance after switch-over. In this case, the actual fill time will be slightly different from the specified fill time.

The fill time is used to pro-rate the relative ram speed profile if specified concurrently; if the absolute ram speed is specified, it will override the specified fill time.

An optimal fill time can be found by performing several filling simulations. If the injection pressure is plotted against fill time, a U-shape process curve typically results, and the fill time corresponding to the minimum injection pressure would be the optimal fill time.

T-CODE#

10100

Units (SI)

s

Warning

The fill time is usually only a few seconds. Make sure that the specified fill time is physically realistic.

If absolute ram-speed profile is specified in the process conditions data file, it will override the fill time.

Resin-injection time

This data set specifies the resin-injection time for C-MOLD Gas-Assisted Injection Molding. This is the duration of resin injection as controlled by the machine ram speed. After resin injection, there could be an optional delay time before the onset of gas injection, which is used to complete the cavity filling and/or continue the post-filling process.

The actual fill time in C-MOLD Gas-Assisted Injection Molding is the sum of the resin-injection time and the gas-injection time during cavity filling.

When a constant ram-speed profile is used, the ratio of the resin-injection time to the total fill time defines the volume fraction of the polymer melt within the cavity.

T-CODE#

10101

Units (SI)

s

Range

Resin injection time Fill time

Warning

If the automatic gas-pressure profiling option is used (T-CODE 11302 is set to 1), then the resin-injection time must be the same as the timer for gas injection to assure a non-interrupted resin flow rate. A delay time is not allowed when automatic gas-pressure profiling is used.

Simultaneous injection of resin and gas is not allowed in C-MOLD Gas-Assisted Injection Molding, so the resin-injection time and timer for gas injection have to be set accordingly.

Post-fill time

This data set specifies the post-fill time. The post-fill time is defined as the time interval between the instant the fill-to-pack switch-over criterion is met (or the cavity is completely filled) and the instant the mold opens.

Alternative industry terms for this stage include holding time and cooling time.

The post-filling stage starts with a packing phase, when more material is packed into the cavity to compensate for material shrinkage. This is followed by a holding phase, when the melt is held in the mold under pressure as the part cools. This holding pressure is applied until gate freeze-off, at which time the melt can no longer flow into and out of the cavity.

The machine will be under specified pack/hold pressure control during the post-filling stage.

The polymer melt experiences cooling throughout the entire post-filling stage. Typically, more than three-quarters of the total cycle time is associated with the post-filling stage. It is approximately proportional to the square of the thickness and varies inversely with the thermal diffusivity, .

The post-fill time (or cooling time) should be of such duration that the part is sufficiently rigid to be ejected. On the other hand, it should not be so long that it unnecessarily adds to the total cycle time. The mold should be opened as soon as the part is sufficiently rigid to be ejected.

C-MOLD analyses provide two additional criteria for mold opening, which can be specified instead of the post-fill time. They are:

1. P/O switch-over by ejection temperature (T-CODE 10500): this sets the ejection temperature criterion. If the temperature of the entire part falls below this temperature, it triggers mold-opening. C-MOLD automatically computes the required post-fill time to meet this criterion.
2. P/O switch over by ejection conversion (T-CODE 10502): this sets the ejection conversion criterion for reactive molding applications. If the conversion level of the entire part meets this conversion level, it triggers mold-opening. C-MOLD automatically computes the required post-fill time to meet this criterion.

T-CODE#

10102

Units (SI)

s

Warning

If both post-fill time and a P/O switch-over criterion are specified in the process conditions file, then post-fill time will be used by C-MOLD Cooling.

Gas-injection time

This data set specifies the duration of gas injection in the gas-assisted injection molding process. It begins the instant the gas is injected, and ends the instant the gas pressure is released.

C-MOLD Gas-Assisted Injection Molding normally stops execution at the end of the gas-injection time. To avoid unnecessary execution time due to the specification of a very long gas-injection times, the analysis will stop calculation when the gas penetration has stopped during the post-filling stage.

T-CODE#

10103

Units (SI)

s

Mold-open time

This data set specifies the duration for which the mold is open. It begins when the mold is opened, and ends when the mold is closed to start the next cycle. It includes the mold opening and closing actions, as well as part ejection.

The mold-open time identifies the time at which mold surfaces lose contact with the polymer melt. Additional heat transfer occurs between the mold and its surroundings during this stage.

The total cycle time is the sum of the fill time, post-fill time (or cooling time), and mold-open time. Outputs such as mold-wall temperature, mold-wall heat flux, and temperature difference, are averaged over the entire cycle, so it is important to use an appropriate mold-open time in the analysis.

T-CODE#

10104

Units (SI)

s

Timer for core or gas injection

This data set is used in the simulation of co-injection and gas-assisted molding processes. In these processes, a timer is used to trigger the injection of core polymer in sequential co-injection molding or gas in gas-assisted injection molding. The timer is set during the filling stage.

In C-MOLD Co-Injection, the timer can be set from nearly zero (complete filling of core polymer) to nearly the fill time (complete filling of skin polymer). The program allows complete filling of core or skin materials (done by regular filling analysis).

The volume fraction of the skin polymer in the part would equal the timer setting for core injection, divided by the fill time. The theoretical maximum amount of core polymer that can be injected without appearing on the surface of the part is approximately 50% for rod-like parts and 70% for plate-like parts. However, the actual value that can be accomplished is much lower. If the timer setting for core injection is less than 40-50% of the fill time, it is very likely that core material will appear on the part surface.

Co-injection will not be simulated if the timer for core injection is not specified.

In C-MOLD Gas-Assisted Injection Molding, simultaneous injection of polymer and gas is not allowed; the timer for gas injection should be equal to or greater than the resin injection time. In this process, there could be an optional delay time between the end of resin injection and the time instant the gas injection is triggered. The delay time before gas injection allows the thin sections to solidify, thus eliminating gas permeation into thin sections (so-called fingering effect). Prolonged delay time, on the other hand, can lead to hesitation marks on the part surface where the melt front stagnates during the delay period. If the resin injection time and timer for gas injection are the same, then there is no delay time.

Note that in this process, a timer setting of zero is meaningless. However, the timer for gas injection might actually be larger than the fill time, if the delay time is long enough; this is because fill time is a reference value used in the resin-injection stage for gas-pressure and gas-volume control options.

The timer for gas injection setting is critical in controlling the entire process. If it is too small, gas will blow through the melt front; if it is set too close to the fill time, the material-saving advantage of this process will not be realized.

T-CODE#

10200

Units (SI)

s

Warning

The timer setting is critical in process control and appearance of the part.

In C-MOLD Co-Injection, this value cannot be greater than the specified fill time.

In C-MOLD Gas-Assisted Injection Molding, this value may be greater than the fill time, depending on the length of the delay time. Simultaneous polymer and gas injection is not allowed, so this value should always be set equal to or greater than the resin-injection time.

Timer for valve gate

This data set sets the valve gate ID, and times when the valve gate opens and closes. In multi-gated cavities, strategically placed valve gates are used to control the melt-front advancement in such a manner as to reduce weld-line formation.

For C-MOLD analyses, a connector element in the finite-element model can be used as a valve gate with an associated timer ID, which points to a timer for valve gate opening or closing.

The valve gates are initially closed; they remain closed until the specified time for opening, then remain open until the specified time for closing. The timers can be triggered to open or close valve gates either concurrently or sequentially. Note that for a given timer ID, the closing time must be greater than the opening time. The timers can be set for values from zero to the specified fill time.

T-CODE#

10204
Order of parameters in the data set

[ID, time for opening, time for closing]

Units (SI)

s

Range

0 time for opening (or closing) fill time

Warning

The valve gates have to be placed and triggered to open or close such that they help to eliminate weld lines and also prevent hesitation in melt-front movement.

The timer settings should be between zero and the specified fill time.

The time for valve gate closing should be greater than the time for valve gate opening.

F/P switch-over by percent volume

This data set specifies the percent of volume filled as the criterion that switches the process from flow-rate (ram-speed) control in the filling stage to pack/hold pressure control in the post-filling stage, before the cavity is completely filled.

Switching the process control from flow-rate control to pack/hold pressure control before the cavity is completely filled helps avoid a pressure spike (excessive cavity pressures) at the end of filling, which can cause mold opening and flashing, and also helps avoid high impact of the ram, which may damage the injection molding machine and the mold.

If the fill-to-pack switch-over by percent volume is used, the process switches to pack/hold pressure control when the percentage of the total volume filled exceeds the specified value. The percentage of volume filled is the same as the percent of total stroke setting on an injection molding machine. A value of 0-100% may be specified for this transition. The default value is 99%.

In some injection molding machines, the controlling scheme is such that the filling stage is controlled by injection pressure, rather than flow rate. In such cases, a 0% fill-to-pack switch-over by volume can be specified, and the pack/hold pressure profile can be used to simulate the entire filling and post-filling process. The analysis will take the pack/hold pressure as the entrance pressure during the filling stage as well as during the packing and holding phases. The actual fill time will be determined by the pack/hold pressure profile.

After fill-to-pack switch-over, if the pack/hold pressure profile is not specified, the same entrance pressure at the switch-over point is maintained for the rest of the filling stage until the cavity is completely filled. If the pack/hold pressure is specified, the analysis will use the pressure profiles at the entrance after the fill-to-pack switch-over occurs.

Other fill-to-pack switch-over criteria that may be used are F/P switch-over by injection pressure (T-CODE 10302) or F/P switch-over by cavity pressure (T-CODE 10304).

T-CODE#

10300

Units (SI)

Percent (%)

Range

0 - 100

Default Value

99

Warning

The switch-over point has to be determined carefully. An early switch-over may cause an insufficient entrance pressure to fill the cavity, and result in a short shot.

F/P switch-over by injection pressure

This data set specifies the injection pressure at the polymer entrance as the criterion that switches the process from flow-rate (ram-speed) control in the filling stage to pack/hold pressure control in the post-filling stage, before the cavity is completely filled.

Switching the process control from flow-rate control to pack/hold pressure control before the cavity is completely filled helps avoid a pressure spike (excessive cavity pressures) at the end of filling, which may cause mold opening and flashing, and also helps avoid high impact of the ram, which may damage the injection molding machine and the mold.

If the fill-to-pack switch-over by injection pressure is used, the process switches to pack/hold pressure control when the entrance (nozzle) pressure exceeds the specified value.

After fill-to-pack switch-over, if the pack/hold pressure profile is not specified, the same entrance pressure at the switch-over point is maintained for the rest of the filling stage until the cavity is completely filled. If the pack/hold pressure is specified, the analysis will use the pressure profiles at the entrance after the fill-to-pack switch-over occurs.

Other fill-to-pack switch-over criteria that can be used are F/P switch-over by percent volume (T-CODE 10204) or F/P switch-over by cavity pressure (T-CODE 10304).

T-CODE#

10302

Units (SI)

Pa

Warning

The switch-over point has to be determined carefully. An early switch-over may cause an insufficient entrance pressure to fill the cavity, and result in a short shot.

F/P switch-over by cavity pressure

This data set specifies the cavity pressure as the criterion that switches the process from flow-rate (ram-speed) control in the filling stage to pack/hold pressure control in the post-filling stage, before the cavity is completely filled.

Switching the process control from flow-rate control to pack/hold pressure control before the cavity is completely filled helps avoid a pressure spike (excessive cavity pressures) at the end of filling, which can cause mold opening and flashing, and also helps avoid high impact of the ram, which can damage the injection molding machine and the mold.

If the fill-to-pack switch-over by cavity pressure is used, the process switches to pack/hold pressure control when the cavity pressure at a specified location exceeds the specified value. In practice, this requires the use of a pressure transducer in the mold.

In C-MOLD analyses, a node in the finite-element mesh (corresponding to the location of pressure transducer) should be specified, along with the desired switch-over pressure.

After fill-to-pack switch-over, if the pack/hold pressure profile is not specified, the same entrance pressure at the switch-over point is maintained for the rest of the filling stage until the cavity is completely filled. If the pack/hold pressure is specified, the analysis will use the pressure profiles at the entrance after the fill-to-pack switch-over occurs.

Other fill-to-pack switch-over criteria that can be used are F/P switch-over by percent volume (T-CODE 10204) or F/P switch-over by injection pressure (T-CODE 10302).

T-CODE#

10304
Order of parameters in the data set

[node number, switch-over pressure]

Units (SI)

Pressure: Pa

Warning

The switch-over point has to be determined carefully. An early switch-over may cause an insufficient entrance pressure to fill the cavity, and result in a short shot.

Timer for hold pressure

During part of the post-filling (cooling) stage, additional material is packed into the cavity under high holding pressure to compensate for material shrinkage that occurs because polymer density increases with increased pressure or decreased temperature. This data set, timer for hold pressure, specifies the time instant of the removal of holding pressure, which marks the end of the holding phase in the post-filling stage.

The timer for hold pressure begins when the fill-to-pack switch-over occurs. It can end at any time during the post-filling stage (including at the end of the post-filling stage). If the timer for hold pressure is not specified, C-MOLD Post-Filling will use the specified post-fill time. If the timer for hold pressure is specified, then when the timer for hold pressure is reached, the holding pressure is released, and C-MOLD Post-Filling continues until the post-fill time is reached.

The gate dimensions must be adjusted according to part thickness to assure proper packing during the holding phase.

T-CODE#

10400

Units (SI)

s

Range

F/P switch-over time timer for hold pressure post-fill time

Default Value

Post-fill time

Warning

If the timer for hold pressure is not specified, C-MOLD Post-Filling will use the specified post-fill time.

It is critical to specify a proper duration for hold pressure. Parts of maximum strength and toughness can be obtained only by maintaining a proper hold pressure until the gates freeze off. After the gates freeze, further application of the holding pressure will not influence the part and will only increase the mass of the runner system.

In conjunction with an appropriate pack/hold pressure profile, an appropriate holding time will also help to prevent shrinkage and voids or weak spots around the gate, which in turn could lead to part failure.

P/O switch-over by ejection temperature

This data set specifies the ejection temperature as the criterion for the machine control to switch from post-filling to mold opening. When the bulk temperature of the part falls below the specified ejection temperature, the mold-opening action is triggered.

The temperature of the part should be sufficiently low so that it is rigid enough to be ejected without significant deformation. In practice, the post-fill (cooling) time has to be determined by trial and error, but using control techniques by placing thermocouples in appropriate locations in the mold is sometimes unwieldy.

C-MOLD Cooling provides a convenient way to determine the required post-fill (cooling) time by simply specifying the ejection temperature criterion. This criterion is used for thermoplastic injection molding analysis only. If this criterion is specified, then the analysis computes the post-fill time. The program stops when the average bulk temperature falls below the specified ejection temperature.

Parts are normally ejected when the temperature falls below the glass transition temperature. Cooling the part much lower would merely increase the overall cycle time. An ideal (optimal) ejection temperature should be such that the entire part is sufficiently rigid to be ejected.

Using appropriate process conditions and cooling channel layout, it is possible to minimize the overall cycle time.

In C-MOLD Cooling, either the post-fill time or this P/O switch-over by ejection temperature may be used to trigger the mold-opening action. If both conditions are specified, C-MOLD Cooling will use the specified post-fill time.

T-CODE#

10500

Units (SI)

K

Warning

The ejection temperature should be such that the entire part is sufficiently rigid to be ejected without significant deformation.

If both conditions are specified, C-MOLD Cooling will use the specified post-fill time.

This criterion is used for thermoplastic injection molding analysis only.

P/O switch over by ejection conversion

This data set specifies the ejection conversion level as the criterion for the machine control to switch from post-filling to mold opening. When the bulk conversion level of the part is greater than the specified ejection conversion value, the mold-opening action is triggered.

The conversion level in the part should be such that it meets the part specifications, and the part is rigid enough to be ejected without significant deformation. In practice, this post-fill time (or curing time) has to be determined by trial and error, but using control techniques by measuring the conversion level of the part in the mold is sometimes unwieldy.

C-MOLD Reactive Molding provides a convenient way to determine the required post-fill time (or curing time) by simply specifying the ejection conversion criterion. This criterion is used for reactive injection molding analysis only. If this criterion is specified, then the analysis computes the post-fill time. The program stops when the average conversion at every node exceeds the specified ejection conversion value.

Ejection conversion values can be specified between the initial conversion level and 1. A conversion value of 1 means that the resin is completely cured, which, in theory, can never happen. If the specified conversion value is less than the initial conversion level or is equal to 1, C-MOLD Reactive Molding will not estimate the post-fill time (or curing time).

If both post-fill time and P/O switch-over by ejection conversion are specified, then C-MOLD Reactive Molding will use the specified post-fill time.

T-CODE#

10502

Range

Initial conversion level < ejection conversion criterion < 1

Warning

The ejection conversion level should be such that it meets the part specifications, and the part is rigid enough to be ejected without significant deformation.

If the specified conversion value is less than the initial conversion level or is equal to one, C-MOLD Reactive Molding will not estimate the post-fill time (or curing time).

If both post-fill time and P/O switch-over by ejection conversion are specified, then C-MOLD Reactive Molding will use the specified post-fill time.

This criterion is used for reactive injection molding analysis only.

Ram-speed profile (absolute)

This data set specifies an absolute ram-speed profile to control flow rate during the filling stage. During this stage, the plasticated melt in the barrel is compressed and forced through the nozzle by the ram motion into the cavity (through the melt delivery system).

The ram velocity is determined by the dynamics of the injection system. The injection rate can be better controlled in machines equipped with closed-loop controls, rather than open-loop controls. While many machines inject the melt at a constant flow rate, those equipped with sophisticated process controllers are capable of injecting the melt at a variable rate with typically five or ten control stages.

Variable-rate injection of the melt provides many advantages. These include improving surface finish (a variable injection rate can be used to reduce jetting and excessive shear stress problems by injecting the melt more slowly when it reaches the gate) and reducing injection pressure.

An optimal ram-speed profile delivers a slow flow rate as the melt passes through the gate area, then increases the flow rate as the melt fills the majority of the cavity, and finally reduces the flow rate prior to completing filling to eliminate a pressure spike (sharp increase in pressure) and flashing due to mold opening (caused by required clamp force exceeding the machine maximum clamp force capability).

In short, using an optimal ram speed profile improves the filling process and part quality.

The two parameters in the absolute ram-speed profile are percentage of stroke and percentage of speed. The injection rate in an absolute ram-speed profile is relative to the maximum machine injection rate. The percentage of stroke is pro-rated based on part volume. The fill time will be determined by the volume to be filled, the absolute ram-speed profile, and the maximum machine injection rate.

In injection machines, the barrel diameter is constant. The polymer melt can be considered to be incompressible, at least during the filling stage. Given these facts, the volumetric flow rate of the melt can be considered to be approximately proportional to the linear velocity of the ram.

Since the inputs are based on percentages, the settings should be between 0 and 100. The first and last setting for percentage of stroke must be 0 and 100, respectively. The ram speed between two controller settings is linearly interpolated. The same number of controller settings which exist on the machine should be used in the analysis.

If the velocity vs. position data is known, it can be easily converted to this input format as explained in this example:

Machine Parameters:

Maximum machine speed: 10 cm/s

Screw Diameter: 3.5 cm

Maximum injection rate = maximum speed x cross-sectional area ~ 96 cm³/s)

Controller settings:

Ram position (cm)	Velocity (cm/s)
0	1.5
1	3.0
2	6.0
3	6.0
4	1.5

Based on ram position, the percentage of stroke settings are 0%, 25%, 50%, 75%, and 100%.

Based on the maximum machine speed of 10 cm/s, the percentage of speed settings are 15%, 30%, 60%, 60%, and 15%.

Thus, the absolute ram-speed profile settings in this case are as follows:

percent of stroke	percent of speed
0	15
25	30
50	60
75	60
100	15

Suppose the volume to be filled (including both runners and part) is 40 cm^3. The percentage of stroke is pro-rated based on part volume: this means the volume to be filled is broken into segments based on the percentage of stroke. In the above case, the volume segments are each 25% of the total volume, or 10 cm³ each. The first 10 cm³ is filled at a rate of 96 x (15/100) = 14.4 cm³/s. The elapsed time is thus 10/14.4 ~ 0.7 s. The next 10 cm³ is filled at a rate of 96 x (30/100) = 28.8 cm³/s. The elapsed time is 10/28.8 ~ 0.35 s. In this way, the cumulative time, which will be the actual fill time, can be calculated.

In some machines, the controller settings can be input in terms of percentage of stroke and percentage of speed. With these machines, those settings may be used directly in the C-MOLD process conditions file.

In some cases, percentage of stroke vs. percentage of speed data is not readily available. What might be available is the position of ram vs. time data. The position of the ram is usually determined using linear variable displacement transducers (LVDTs). If LVDTs or any other automatic position measuring devices are not available, then a crude estimate can be obtained by using a stop watch and measuring position vs. time. Note that in this case, human response times are relatively large (100 - 300 milliseconds, which is about the same range as the changes that are tracked). However, by taking many measurements and averaging them, this method should provide a reasonable estimate.

The way to enter the settings based on this data is shown in the example below. Assume that position vs. time data is available for five controller settings.

In this example, the following will also be assumed:

Total volume to be filled (runners and part): 40 cm³

Machine stroke: 40 mm (4 cm)

Maximum machine speed: 10 cm/s

Maximum machine injection rate: 100 cm³/s

Position vs. time data:

position (cm)	time (s)
0	0.0
1	0.4
2	0.6
3	0.8
4	1.2

The percentage of stroke can be obtained based on the position. In the above case, the corresponding stroke settings would be 0%, 25%, 50%, 75%, and 100%.

The speed is determined by dividing the change in position by the elapsed time. In the above example, the change in position occurs in equal segments of 1 cm. For the first segment, the elapsed time is 0.4 s. Thus, the speed is 1/0.4 = 2.5 cm/s. For the next segment, the elapsed time is 0.2 s. Thus, the speed is 1/0.2 = 5 cm/s. The rest of the calculations can be done similarly. The percentage of speed is based on the maximum machine injection speed (10 cm/s). Thus, the percentage of speed settings for this example are 0%, 25%, 50%, 50%, and 25%.

The absolute ram-speed profile settings for the above example are:

percent of stroke	percent of speed
0	0
25	25
50	50
75	50
100	25

Thus, position vs. time data is easily converted to percentage of stroke vs. percentage of speed data.

There is usually some offset between the set points and the actual machine response. The machine response data should be used, if available.

Both C-MOLD Filling EZ and C-MOLD Filling calculate the recommended ram-speed profile, based on the requirement of constant melt-front velocity. This recommended profile is relative to the specified fill time (see relative ram-speed profile, T-CODE 01602); the injection flow rate is pro-rated by the total volume to be filled to achieve the specified fill time. This output subsequently can be used to prepare the absolute ram-speed profile settings.

T-CODE#

10600

Default Value

Constant flow rate

Warning

Absolute ram-speed profile will override the fill time if both are specified.

Ram speed profile (rel)

This data set specifies a relative ram-speed profile to control flow rate during the filling stage. During this stage, the plasticated melt in the barrel is compressed and forced through the nozzle by the ram motion into the cavity (through the melt delivery system).

The ram velocity is determined by the dynamics of the injection system. The injection rate can be better controlled in machines equipped with closed-loop controls, rather than open-loop controls. While many machines inject the melt at a constant flow rate, those equipped with sophisticated process controllers are capable of injecting the melt at a variable rate with typically five or ten control stages.

Variable-rate injection of the melt provides many advantages. These include improving surface finish (a variable injection rate can be used to reduce jetting and excessive shear stress problems by injecting the melt more slowly when it reaches the gate) and reducing injection pressure.

An optimal ram-speed profile delivers a slow flow rate as the melt passes through the gate area, then increases the flow rate as the melt fills the majority of the cavity, and finally reduces the flow rate prior to completing filling to eliminate a pressure spike (sharp increase in pressure) and flashing due to mold opening (caused by required clamp force exceeding the machine maximum clamp force capability).

In short, using an optimal ram speed profile improves the filling process and part quality.

The two parameters in the absolute ram-speed profile are percentage of stroke and percentage of speed. Since the inputs are based on percentages, the settings should be between 0 and 100. The first and last setting for percentage of stroke must be 0 and 100, respectively. The ram speed between two controller settings is linearly interpolated.

If the relative ram-speed profile is used, the injection rate is pro-rated by the total volume to be filled to achieve the specified fill time. In other words, the flow rate is automatically adjusted based on the specified ram-speed profile and fill time. The actual injection flow rate is also constrained by the maximum machine injection rate. The percentage of stroke is pro-rated based on part volume.

Both C-MOLD Filling EZ and C-MOLD Filling calculate the recommended ram-speed profile, based on the requirement of constant melt-front velocity. These analyses may be executed without specifying any ram-speed profile initially; the recommended ram-speed profile can be used subsequently to execute another analysis. This recommended ram-speed profile can be converted to machine settings easily as explained in the following example:

Recommended ram speed profile:

percent of stroke	percent of speed
0	20
20	60
40	00
60	80
80	60
100	20

Maximum machine speed: 10 cm/s

Barrel diameter: 3.5 cm

Maximum injection rate = maximum speed x cross-sectional area ~ 96 cm³/s)

Machine stroke: 5 cm

Total volume to be filled: 40 cm³

Target fill time: 2 s

One-hundred percent in the relative ram-speed profile corresponds to the maximum injection flow rate used in the process. Assume it is x cm³/s. For the same profile shape as the recommended ram-speed profile, the settings should be as follows:

percent of stroke	percent of speed
0	0.2 x x
20	0.4 x x
40	x
60	0.8 x x
80	0.6 x x
100	0.2 x x

Based on the percentage of stroke settings and total volume to be filled, each volume segment is 8 cm³.

The time to fill is:

Set the above expression equal to the target fill time of 2 s.

The value of x after solving the above equation is 66 cm³.

Based on the maximum machine capacity of 96 cm³, it is ~ 69%. The rest of the settings can be determined based on the profile.

Thus, the absolute ram-speed profile becomes:

percent of stroke	percent of speed
0	14
20	28
40	69
60	56
80	42
100	14

Alternately, the input for maximum machine injection rate may be changed to 66 cm³/s, and the same recommended ram-speed profile settings can be used as the absolute ram-speed profile.

T-CODE #

10602

Default Value

Constant flow rate

Gas plunger compression-speed profile

This data set defines the gas plunger compression-speed profile, used when the gas volume is controlled. The two parameters in this data set are percentage of plunger stroke and percentage of speed.

In gas-assisted injection molding, the two most widely used methods for controlling the gas injection are gas-pressure control and gas-volume control.

In the gas-volume control process, a fixed amount of gas is first metered into a compression cylinder and then compressed with a plunger into the mold to displace the polymer melt. C-MOLD Gas-Assisted Injection Molding computes the gas pressure based on the changing gas volume within the compression cylinder and the cavity, as well as the gas plunger compression-speed profile.

The actual gas-injection flow rate is pro-rated by the initial gas volume in the compression cylinder (T-CODE 12000) to be injected within the specified traveling time of the gas plunger (T-CODE 12300).

The number of settings should be set equal to the actual number of controller settings available in the machine.

Example settings:

Initial gas volume: 0.001 m³

Traveling time of the gas plunger: 2 s

Number of controller settings: 5

Gas plunger compression-speed profile:

percent of stroke	percent of speed
0	50
20	0
40	80
60	80
80	80
100	50

T-CODE#

10606
Order of parameters in the data set

[percentage of plunger stroke, percentage of speed]

Units (SI)

Percent (%)

Range

0 - 100

Default Value

Constant plunger speed

Absolute pack/hold pressure profile

This data set specifies an absolute profile that regulates the amount of pressure applied during the post-filling stage, based on the maximum machine injection pressure. This absolute pack/hold pressure profile has two parameters, percentage of time and percentage of maximum injection pressure. Since the values are in terms of percentages, they should be between 0 and 100. The first and last settings of the percentage of time should be 0 and 100, respectively. This data set can have as many settings as the actual controller on the injection molding machine.

During the early stages of the post-filling (cooling) stage, more material is packed into the cavity under high holding pressure to compensate for material shrinkage due to increased density of the polymer melt which in turn is due to increased pressure and decreased temperature.

The time interval during which this occurs is the packing time, or holding time. The timer for hold pressure (T-CODE 10400) defines the duration of this time and signals the release of pressure during the post-filling (cooling) stage.

The packing pressure level is very important in preventing flashing and tool damage. The proper holding pressure helps to assure good surface finish and to prevent shrinkage or voids. In practice, the pack/hold pressure level is typically taken to be 80% of the injection pressure at the end of filling.

Advanced process controllers are capable of providing profiled pack/hold pressure levels. Providing a profiled pack/hold pressure offers many advantages, including lowering the clamp force requirement and maintaining good part quality.

The actual pack/hold pressure profile is determined by multiplying the maximum machine injection pressure (T-CODE 10002) by the individual percentage of injection pressure specified; the pressure setting is pro-rated with respect to the maximum machine injection pressure. The actual time is determined by multiplying the timer for hold pressure (T-CODE 10400) by the individual percentage of time.

The default pack/hold pressure is constant.

Example settings:

Maximum machine injection pressure: 80 MPa

Post-fill time: 50 s

Timer for hold pressure: 25 s

Pack/hold pressure profile (abs):

A	B	C	D
% time	actual time (s) (after F/P switch-over)	% of maximum injection pressure	actual packing pressure (MPa) (C/100 x 80)
0	0	50	40
20	5	70	56
40	10	90	72
60	15	75	60
80	20	75	60
100	25	0	0

If the machine hydraulic response time is longer than the time interval between the time settings, then a response time equal to half the time interval between the settings will be used in the pack/hold pressure profile.

If no pack/hold pressure profile is specified, C-MOLD Post-Filling assumes that the entrance pressure at the instant of fill-to-pack switch-over remains constant throughout the holding time.

The other pack/hold pressure control that can be specified is a relative pack/hold pressure profile (T-CODE 10702), in which the pressure level is pro-rated with respect to the entrance pressure at the instant of fill-to-pack switch-over.

T-CODE#

10700
Order of parameters in the data set

[percentage of time, percentage of maximum machine injection pressure]

Units (SI)

Percent (%)

Range

0 - 100

Default Value

Constant pressure

Warning

An abrupt transition between packing and holding pressures should be avoided as it could lead to potential part warpage.

Relative pack/hold pressure profile

This data set specifies a relative profile that regulates the amount of pressure applied during the post-filling stage, based on the entrance pressure at the instant of fill-to-pack switch-over. This relative pack/hold pressure profile has two parameters, percentage of time and percentage of maximum injection pressure. Since the values are in terms of percentages, they should be between 0 and 100. The first and last settings of the percentage of time should be 0 and 100, respectively. This data set can have as many settings as the actual controller on the injection molding machine.

During the early stages of the post-filling (cooling) stage, more material is packed into the cavity under high holding pressure to compensate for material shrinkage due to increased density of the polymer melt which in turn is due to increased pressure and decreased temperature.

The time interval during which this occurs is the packing time, or holding time. The timer for hold pressure (T-CODE 10400) defines the duration of this time and signals the release of pressure during the post-filling (cooling) stage.

The packing pressure level is very important in preventing flashing and tool damage. The proper holding pressure helps to assure good surface finish and to prevent shrinkage or voids. In practice, the pack/hold pressure level is typically taken to be 80% of the injection pressure at the end of filling.

Advanced process controllers are capable of providing profiled pack/hold pressure levels. Providing a profiled pack/hold pressure offers many advantages, including lowering the clamp force requirement and maintaining good part quality.

The actual pack/hold pressure profile is determined by multiplying the pressure at the polymer entrance at the instant of fill-to-pack switch-over by the individual percentage of pressure specified; the pressure setting is pro-rated with respect to the entrance pressure. The actual time is determined by multiplying the timer for hold pressure (T-CODE 10400) and the individual percentage of time.

The default pack/hold pressure is constant.

Example settings:

Entrance pressure at F/P switch-over: 50 MPa

Post-fill time: 30 s

Timer for hold pressure: 10 s

Pack/hold pressure profile (rel):

A	B	C	D
% time	actual time (s) (after F/P switch-over)	F/P switch-over pressure	actual packing pressure (MPa) (C/100 x 80)
0	0	90	45
20	2	90	45
40	4	80	40
60	6	80	40
80	8	70	35
100	10	50	25

If the machine hydraulic response time is longer than the time interval between the time settings, then a response time equal to half the time interval between the settings will be used in the pack/hold pressure profile.

If no pack/hold pressure profile is specified, C-MOLD Post-Filling assumes that the entrance pressure at the instant of fill-to-pack switch-over remains constant throughout the holding time.

The other pack/hold pressure control that can be specified is an absolute pack/hold pressure profile (T-CODE 10700), in which the pressure level is pro-rated with respect to the maximum machine injection pressure.

T-CODE#

10702
Order of parameters in the data set

[percentage of time, percentage of F/P switch-over pressure]

Units (SI)

Percent (%)

Default Value

Constant pressure

Warning

An abrupt transition between packing and holding pressures should be avoided as it could lead to potential part warpage.

Variable gas-pressure profile

This data set specifies the gas-pressure profile to be imposed at the gas entrance for C-MOLD Gas-Assisted Injection Molding. The two parameters in this data set are percentage of gas injection time and percentage of maximum gas pressure. The gas pressure at each step is calculated using the maximum gas pressure (T-CODE 10010) as the reference value. The time corresponding to the pressure level is relative to the gas-injection time (T-CODE 10103).

In gas-assisted injection molding, the two most widely used methods for controlling the gas injection are gas-pressure control and gas-volume control.

With gas-pressure control, a profiled (constant or step) gas pressure is imposed at the gas entrance point; the gas pressure is regulated during the gas-injection stage. Using the specified gas-pressure profile as the input, the analysis computes the resulting polymer melt flow rate in the filling and post-filling stages.

In C-MOLD Gas-Assisted Injection Molding, it also is possible to obtain an automatic gas-pressure profile, based on the relative ram-speed profile when the gas-injection control option is set to gas-pressure control (T-CODE 11302 is set to 0). The calculated gas-injection profile would be such that the melt fills the cavity based on the specified ram-speed profile.

Example Settings:

Gas-injection time: 10 s

Maximum gas pressure: 20 MPa

Variable gas-pressure profile:

% of gas-injection time	actual time after gas injection (s)	% of maximum gas pressure	actual pressure (MPa)
0	0	25	5
20	2	80	16
40	4	100	20
60	6	100	20
80	8	100	20
100	10	100	20

T-CODE#

10704
Order of parameters in the data set

[percentage of gas injection time, percentage of maximum gas pressure]

Units (SI)

Percent (%)

Default Value

Constant gas pressure throughout the gas-injection stage

Warning

The gas-pressure profile should be such that the melt front advances without hesitation, and gas does not blow through the melt front.

Ambient temperature

This data set specifies the ambient temperature for C-MOLD analyses. The ambient temperature affects the heat transfer in the mold. In general, it has very little influence on the part quality, except in the case of precision injection molding, where the ambient temperature must be rigorously controlled.

The ambient temperature value is used to calculate the heat transfer from mold exterior surfaces to the ambient medium (air). For this calculation, the mold exterior surface is considered to be a sphere with an equivalent diameter to preserve the minimum surface area of the box within which one can fit all cooling channels (excluding hoses), runner systems and cavity.

In C-MOLD analyses the default ambient temperature is taken to be 298.16 K (25 °C). The specified ambient temperature is also used as the mold temperature in C-MOLD Filling, if the coolant manifold control (T-CODE 11100) is not specified in the simulation.

T-CODE#

11000

Units (SI)

K

Default Value

298.16 K (25 °C)

Inlet melt temperature

This data set specifies the polymer melt temperature at the entrance points. In C-MOLD analyses, a constant inlet melt temperature is assumed at all entrances.

In the actual process, due to viscous heating effects in the nozzle, the actual inlet temperature might be higher than the barrel temperature setting on the injection molding machine. The temperature rise could be as much as 30 °C, depending on the injection speed and material properties.

There are two possible work-arounds for C-MOLD simulations to compensate for this nozzle temperature rise:

1. For thermoplastic injection molding, provide an air-shot temperature measurement, instead of using the barrel temperature setting. This measurement should be performed at the same barrel temperature and injection speed as would be used in the actual process.
2. Provide the barrel temperature, but include the nozzle in the finite-element mesh. The nozzle should be modeled as a hot runner to account for viscous heating in the predictions.

In any case, this inlet melt temperature data must be accurate for the simulations to generate good predictions.

The inlet melt temperature should be greater than the transition temperature of the polymer.

Handbook values of suggested inlet temperatures for various resins can be used as a starting point.

T-CODE#

11002

Units (SI)

K

Warning

The inlet melt temperature data must be accurate for the simulations to generate good predictions.

The inlet melt temperature should be greater than the transition temperature of the polymer.

In the case of thermoplastic injection molding, the air-shot temperature should be used instead of the barrel temperature setting.

Second melt temperature

This data set specifies the melt temperature of the second polymer material at the polymer entrances for C-MOLD Co-Injection. A constant inlet melt temperature is assumed at all entrances.

C-MOLD Co-Injection is capable of handling a different melt temperature for the second (core) polymer material.

In the actual process, due to viscous heating effects in the nozzle, the actual inlet temperature may be higher than the barrel temperature setting on the injection molding machine. The temperature rise may be as much as 30 °C, depending on the injection speed and material properties.

There are two possible work-arounds for C-MOLD simulations to compensate for this nozzle temperature rise:

1. For thermoplastic injection molding, provide an air-shot temperature measurement, instead of using the barrel temperature setting. This measurement should be performed at the same barrel temperature and injection speed as would be used in the actual process.
2. Provide the barrel temperature, but include the nozzle in the finite-element mesh. The nozzle should be modeled as a hot runner to account for viscous heating in the predictions.

In any case, this inlet melt temperature data must be accurate for the simulations to generate good predictions.

The inlet melt temperature should be greater than the transition temperature of the polymer.

Handbook values of suggested inlet temperatures for various resins can be used as a starting point.

C-MOLD Co-Injection will issue an error message and terminate execution, if the core polymer inlet melt temperature is not specified.

T-CODE#

11003

Units (SI)

K

Warning

The inlet melt temperature data must be accurate for the simulations to generate good predictions.

The inlet melt temperature should be greater than the transition temperature of the polymer.

In the case of thermoplastic injection molding, the air-shot temperature should be used instead of the barrel temperature setting.

Inlet melt initial conversion

This data set specifies the initial conversion (curing) level at the entrance for C-MOLD Reactive Molding. In the case of injection molding or transfer molding of reactive materials, the reaction process typically is not initiated in the barrel or transfer molding pot. The barrel or pot temperature is set low enough so that no significant reaction takes place in them. In the case of injection molding of rubber compounds, the material exhibits an induction period before curing starts.

In all, the inlet melt conversion of the material is typically very small prior to injection.

C-MOLD Reactive Molding assumes a constant inlet melt conversion at all entrance points. Any value between 0 and the material gelation conversion can be specified. If the material has an induction period, then any value between -1 and the gelation conversion can be specified. Values of -1, 0, and 1 for the inlet melt conversion correspond to the beginning of induction period, the beginning of conversion and the end of conversion, respectively.

One way to estimate the initial conversion is to quench a small material sample being injected through the nozzle or plunger, then perform a DSC experiment to measure the residual conversion. Another way to estimate the initial conversion is by using the material constants for isothermal induction time or isothermal curing kinetics, and the actual temperature and time history of the material before injection. For more details on this, refer to the C-MOLD Reactive Molding User's Guide.

T-CODE#

11010

Range

0 ₀ 1 during conversion
-1 ₀ 0 during induction period

Warning

Do not use zero as the inlet melt conversion level. If the initial conversion level actually is zero, use a very small, non-zero number (for example, 1.0 x 10^-5) instead. Using zero might, on occasion, lead to numerical computational problems.

Coolant manifold control

This data set specifies the parameters of the coolant manifold control.

The mold-wall temperature is determined by the heat transfer taking place between the coolant flow in the cooling channel network, heat released by the polymer melt in the cavity, and heat transfer to the ambient air.

The mold-wall temperature has little influence during the filling stage. The average coolant temperature or the ambient temperature can be assumed to be the approximate value of the mold-wall temperature in C-MOLD Filling.

However, the mold-wall temperature has a significant effect during the post-filling (cooling) stage, which has a direct impact on the overall cycle time and part quality. It is very important to determine the mold-wall temperature distribution as a function of time and position. C-MOLD Cooling performs such a calculation based on the coolant manifold control data, among other process conditions.

The parameters for the coolant manifold control are: manifold ID, inlet coolant temperature, total coolant flow rate, total coolant pressure drop, and coolant material ID.

A coolant manifold is defined as a connected network of cooling channels (regular, baffles, bubblers) that has one entrance and one exit point. Each coolant manifold is assigned a unique manifold control identification number (ID).

The entrance node of each coolant manifold has an associated inlet coolant temperature as specified. This temperature is a nodal property that points to the corresponding coolant manifold ID in the process conditions data file (filename.prc). The number of occurrences of the coolant manifold control data set in the process conditions data file should match the number of coolant manifolds used in the finite-element model.

Either the coolant flow rate or pressure drop can be specified as the boundary condition for C-MOLD Coolant Flow. If both are specified, then the total flow rate will be used. Based on the flow rate calculations, a heat transfer coefficient is estimated, and this becomes the boundary condition for calculating the heat transfer to the cooling channels. The flow rate should be chosen such that there is turbulent flow in the network, which leads to better heat transfer.

The coolant material ID is not used in the current C-MOLD release; only one coolant type can be used in the analysis.

T-CODE#

11100
Order of entries in the T-CODE

[ID, inlet temperature, total flow rate, total pressure drop, coolant material ID]

Units (SI)

Temperature: K
Flow rate: m³/s
Pressure drop: Pa

Warning

If coolant manifolds are defined in the finite-element mesh file (filename.fem), C-MOLD Cooling checks filename.prc for occurrences of the coolant manifold control data set; if none exist, or if the number of occurrences is less than the number of coolant manifolds defined in filename.fem, an error message is issued and the analysis terminates.

The flow rate should be chosen such that there is turbulent flow in the cooling channel network, which leads to better heat transfer.

Hot runner manifold control

This data set specifies the parameters of the hot runner manifold control. These are: hot runner manifold ID, hot runner wall temperature, and insulation thickness.

To obtain parts that are free of runners, flash, and gate stubs, hot runner systems (also referred to as hot manifold systems or runnerless molding) may be employed. The polymer melt in hot runners is maintained in a molten state by internal or external heaters, and it is not ejected with the molded part. The heated runner plates are insulated from the rest of the mold.

In the case of insulated runner systems, oversized passages of sufficient size are formed in the mold plate, such that under operating conditions, the insulation effect of the frozen plastic adjacent to the wall combined with the heat applied with each shot maintains an open, molten flow path.

Hot runners provide the advantage of maintaining a uniform melt temperature from the nozzle to the cavities.

In the current release of C-MOLD, only externally heated runners are handled.

It is common practice to control the temperatures at individual sections of the hot runner manifold to achieve a controlled flow distribution. All hot runner elements controlled under one section should point to a unique hot runner manifold ID with a properly assigned wall temperature; this information is stored in the finite-element mesh file (filename.fem).

At the beginning of the cycle, the melt temperature in the hot runner may not be equal to the inlet melt temperature or the hot runner wall temperature, as the melt typically undergoes shear heating during the filling stage and cooling during the post-filling (cooling) and mold-opening stages. An accurate estimate of the initial temperature in the hot runner should be determined by a cyclic, steady-state analysis.

The current C-MOLD analyses, however, assume the initial melt temperature in a hot runner to be equal to the inlet melt temperature or the hot runner wall temperature, depending on the initial fill condition specified for the analysis.

The hot runner manifolds are separated from the mold base by glass fiber insulation or by an air gap. C-MOLD Cooling uses this insulation thickness to determine the heat transfer from the hot runner manifold to the surrounding mold base. The insulation thickness used in C-MOLD Cooling depends on whether the insulation is provided by glass fiber or an air gap.

When glass-fiber insulation is used, its thickness is used as the insulation thickness value.

When a small air gap separates the hot runners from the mold base, an equivalent insulation thickness must be specified for the analysis. The equivalent insulation thickness can be computed as follows:

Insulation thickness = Air gap thickness x Kr

where

The thermal conductivity of glass fiber is ~ 0.04 W/m-K.

The thermal conductivity of air varies between 0.033-0.048 W/m-K in the temperature range of 90-320 °C. The actual value of the thermal conductivity corresponding to the hot runner temperature can be found in any heat transfer handbook.

Use the above formula to determine the equivalent air gap thickness and use that value as the insulation thickness for C-MOLD Cooling.

T-CODE#

11200
Order of parameters in the data set

[manifold ID, temperature, insulation thickness]

Units (SI)

Temperature: K
Insulation thickness: m

Default Value

Initial melt temp. in hot runner = Inlet melt temp.
Insulation thickness = 10 mm (0.01 m)

Warning

If hot runner manifolds are defined in the finite-element mesh file (filename.fem), C-MOLD analyses check filename.prc for occurrences of the hot runner manifold control data set; if none exist, or if the number of occurrences is less than the number of hot runner manifolds defined in filename.fem, an error message is issued and the analysis terminates.

Transient hot runner manifold control

This data set specifies the parameters for the transient hot runner manifold control. These are: hot runner manifold ID, time, and hot runner wall temperature.

On rare occasions, the hot runner wall temperature is controlled as a function of time. This is done to maintain a uniform temperature during the filling and packing stages of the injection molding cycle.

It is common practice to control the temperatures at individual sections of the hot runner manifold to achieve a controlled flow distribution. All hot runner elements controlled under one section should point to a unique hot runner manifold ID with a properly assigned wall temperature; this information is stored in the finite-element mesh file (filename.fem).

There can be as many occurrences of this data set in the process conditions data file (filename.prc) as the actual process controller settings in the machine.

T-CODE#

11202
Order of parameters in the data set

[Manifold ID, time, temperature]

Units (SI)

Time: s
Temperature: K

Range

N/A

Default Value

N/A

Warning

If hot runner manifolds are defined in the finite-element mesh file (filename.fem), C-MOLD analyses check filename.prc for occurrences of this data set; if none exist, or if the number of occurrences is less than the number of hot runner manifolds defined in filename.fem, an error message is issued and the analysis terminates.

The heat transfer between the hot runner manifold and mold base is not considered. Because of this, this data set is used only by C-MOLD Filling and C-MOLD Post-Filling. It is not used by C-MOLD Cooling.

Gas pressure

This data set specifies the constant gas-pressure level during the gas-injection period.

The gas pressure level is critical in assuring proper filling in the gas-assisted injection molding process. Since the effective gas-injection time (the interval between the beginning of gas injection and the instant the cavity is completely filled) is relatively short, the gas pressure at the gas entrance will be approximately constant during cavity filling. This is true regardless of whether the process employs a constant gas pressure, a profiled gas pressure, or even constant gas volume. The resulting change in gas pressure due to changes in gas-volume or gas-pressure control becomes significant only during the post-filling stage.

Prior to gas injection, the volumetric flow rate at both the melt front and polymer entrance is based on the specified ram-speed profile. After gas injection, the flow rate of the advancing melt front depends on the gas pressure level. In general, the higher the gas pressure, the faster the polymer flows, and the faster the fill time.

An estimate of the gas pressure can be obtained by first executing C-MOLD Gas-Assisted Injection Molding with the automatic gas-pressure profile option and then using a reasonable, average value from this output as the gas-pressure level at the entrance.

For a more realistic pressure control with varying gas pressure during filling and post-filling stages, use the variable gas pressure profile (T-CODE 10704) and the maximum gas pressure (T-CODE 10010).

T-CODE#

11300

Units (SI)

Pa

Warning

The gas pressure level should not be so high as to cause material degradation or gas-blow through, or so low as to cause hesitation in melt-front advancement.

Initial gas pressure

This data set specifies the initial pressure of the gas within the compression cylinder, which will be compressed by the gas plunger in gas-assisted injection molding processes using gas-volume control.

This, along with the initial gas volume (T-CODE 12000), is used to determine the subsequent change in pressure and volume of the gas, based on the rate of compression.

T-CODE#

11301

Units (SI)

Pa

Warning

The initial gas pressure should be specified only if the gas-volume control option is used (T-CODE 11302 is set to 2).

Gas-injection control option

This data set specifies the method of controlling gas injection for C-MOLD Gas-Assisted Injection Molding. Three options are allowed:

1. Gas-pressure control: This is indicated by a value of 0 in the data set. When this option is specified, the analysis takes a specified gas-pressure profile (constant, step) as the input, and computes the resulting polymer flow rate during filling and post-filling stages.
2. Automatic gas-pressure profiling: This is indicated by a value of 1 in the data set. When this option is specified, the analysis automatically predicts an ideally profiled gas pressure, so that the polymer melt flow rate during cavity filling follows the specified ram-speed profile. The purpose of this option is to provide a reasonable estimate of gas pressures that deliver a desirable melt velocity.
3. Gas-volume control: This is indicated by a value of 2 in the data set. With gas-volume control, a fixed amount of gas (T-CODE 12000) is metered into a compression cylinder, then the gas is compressed with a plunger into the mold. The analysis computes the gas pressure based on the changing gas volume within the compression cylinder and cavity, as well as the gas plunger compression-speed profile (T-CODE 10606).

T-CODE#

11302

Range

0, 1, 2

Default Value

0

Warning

If this option is set to 1 (automatic gas-pressure profile is used), it will override the constant (or profiled) gas-pressure input.

Initial gas volume

This data set specifies the initial volume of gas within the compression cylinder that will be compressed by the gas plunger when gas-assisted injection molding proceeds under gas-volume control.

This, along with the initial gas pressure (T-CODE 11301), is used to determine the subsequent change in pressure and volume of the gas based on the rate of compression.

T-CODE#

12000

Units (SI)

m³

Warning

This process condition should be used only when the gas-volume control option is chosen (T-CODE 11302 is set to 2).

Volume of gas-injection line

This data set specifies the volume of the gas-injection line between the compression cylinder and the gas-injection point when gas-assisted injection molding proceeds under gas-volume control.

The volume of the gas-injection line is important in C-MOLD Gas-Assisted Injection Molding, to calculate the resulting gas pressure accurately. There will be significant variation in the final gas pressure if the volume of the gas-injection line is not taken into account, as the compression ratio will be different.

The volume of the gas-injection line can be estimated by measuring the length of the gas-injection tube between a control valve close to the exit of the compression cylinder and the gas-injection point, and multiplying this length by the internal cross-sectional area of the tube.

T-CODE#

12100

Units (SI)

m³

Warning

This process condition should be used only when the gas-volume control option is chosen (T-CODE 11302 is set to 2).

Traveling time of the gas plunger

This process condition specifies the traveling time of the gas plunger when gas-assisted injection molding proceeds under gas-volume control.

When the gas plunger compression-speed profile (T-CODE 10606) is used, the actual injection flow rate of the gas is pro-rated by the initial gas volume (T-CODE 12000) and this traveling time of the gas plunger.

T-CODE#

12300

Units (SI)

s

Warning

This process condition should be used only when the gas-volume control option is chosen (T-CODE 11302 is set to 2).

Pressurization stage

This data set specifies the parameters that define the pressurization events that occur during the blow-molding or thermoforming process. The pressurization stage is used to specify the blowing of parison into the mold cavity, or the application of vacuum to stretch the sheet into the mold in the thermoforming process. Each occurrence of this data set specifies the following parameters: the start time and end time (specified as percentage of the overall cycle time), depressurization option, maximum displacement, and a node release option.

C-MOLD Blow Molding & Thermoforming automatically determines the direction of positive pressure application to deform the parison or sheet on to the mold surfaces. If the depressurization option is set to 0, pressure or vacuum is applied in a manner that stretches the polymer onto the mold inner surfaces. If this option is set to 1, it specifies the depressurization stage, and the pressure is applied in a manner that withdraws the polymer or sheet from the mold inner surfaces. By default, this option is set to 0.

The extent of pressurization is determined by the maximum distance moved by a node associated with the polymer (parison or sheet); this is represented by the maximum displacement parameter in this data set.

A pre-pressurization stage in blow-molding is specified by entering a maximum displacement that corresponds to a small distance (say, 5%) of the parison diameter or sheet length.

A final pressurization stage is specified by entering a displacement that corresponds to the maximum distance a polymer node is expected to travel; a rule of thumb is to use the sum of the maximum length, width, and height dimensions of the mold inner surfaces to ensure that all polymer nodes in the parison or sheet that are expected to deform into the mold cavity do so before the analysis terminates.

The release option is used by the analysis to accommodate moving plugs or stretch rods, from which the polymer releases during the pressurization stage. If this option is set to 1, the polymer is allowed to lift off plugs or stretch rods. For most analyses, 0 would be the appropriate entry for this option.

T-CODE#

13000
Order of parameters in the data set

[start time, end time, depressurization option, maximum displacement, release option]

Units (SI)

Start and end times: Percent of total cycle time (%)
Maximum displacement: m

Range

Depressurization option: 0 or 1
Release option: 0 or 1

Default Value

Depressurization option: 0
Release option: 0

Warning

In most analyses, the release option should be set to 0.

Constant pressure mold closing

This data set specifies the parameters that define the mold-motion events that occur during the constant pressure displacement process. Each occurrence of this data set specifies the start time and end time (specified as percentage of the overall cycle time), mold ID (mold surface number), displacement, direction, and a node-release option.

The displacement stage is used to specify the movement of mold units, for instance, the closing of the two mold-halves in a blow-molding process. The displacement stage is further classified into two categories: constant pressure stage, or constant volume stage. The constant volume stage is used only in processes in which molds close around a parison with bottom pinch-off.

The time at which each mold-surface unit starts and stops moving in this displacement stage have to be entered. These time instances are used only to correctly synchronize the mold parts. Consequently, the absolute magnitudes of the instances are not important, although the relative magnitudes are important in the case of multiple mold motions.

An integer between 1 and 3 must be entered for the mold ID. This mold surface number identifies all the elements associated with this event. The same number occurs in the element property data set in the finite-element mesh file.

The displacement is the net distance moved by the mold during this stage. It must be specified for all mold-surface units that are in motion during this stage.

The direction identifies the global coordinate axis along which this motion occurs. The displacement directions are identified as follows:

1 for x

2 for y

3 for z

The appropriate number must be entered for each mold-surface unit.

The release option is used in the analysis to accommodate moving plugs or stretch rods, from which the polymer releases during the displacement stage. If this option is set to 1, the polymer is allowed to lift off plugs or stretch rods. For most analyses, 0 would be the appropriate entry for this option.

T-CODE#

13010
Order of parameters in the data set

[start time, end time, mold ID, displacement, direction, release option]

Units (SI)

Displacement: m
Start and end times: Percentage of total cycle time (%)

Range

Mold ID: 1, 2, or 3
Direction: 1, 2, or 3
Release option: 0 or 1

Default Value

Release option: 0

Warning

In most analyses, the release option should be set to 0.

Constant volume mold closing

This data set specifies the parameters that define the mold-motion events that occur during the constant volume displacement process. Each occurrence of this data set specifies the start time and end time (specified as percentage of the overall cycle time), mold ID (mold surface number), displacement, direction, and a node-release option.

The displacement stage is used to specify the movement of mold units, for instance, the closing of the two mold-halves in a blow-molding process. The displacement stage is further classified into two categories: constant pressure stage, or constant volume stage. The constant volume stage is used only in processes in which molds close around a parison with bottom pinch-off.

The time at which each mold-surface unit starts and stops moving in this displacement stage have to be entered. These time instances are only used to correctly synchronize the mold parts. Consequently, the absolute magnitudes of the instances are not important, although the relative magnitudes are important in the case of multiple mold motions.

An integer between 1 and 3 must be entered for the mold ID. This mold surface number identifies all the elements associated with this event. The same number occurs in the element property data set in the finite-element mesh file.

The displacement is the net distance moved by the mold during this stage. It must be specified for all mold-surface units that are in motion during this stage.

The direction identifies the global coordinate axis along which this motion occurs. The displacement directions are identified as follows:

1 for x

2 for y

3 for z

The appropriate number must be entered for all mold-surface units.

The release option is used in the analysis to accommodate moving plugs or stretch rods, from which the polymer releases during the displacement stage. If this option is set to 1, the polymer is allowed to lift off plugs or stretch rods. For most analyses, 0 would be the appropriate entry for this option.

T-CODE#

13012
Order of parameters in the data set

[start time, end time, mold ID, displacement, direction, release option]

Units (SI)

Displacement: m
Start and end times: Percentage of total cycle time (%)

Range

Mold ID: 1, 2, or 3
Direction: 1, 2, or 3
Release option: 0 or 1

Default Value

Release option: 0

Warning

Constant volume mold closing should be specified only in processes in which the mold closes around a parison with bottom pinch-off.

In most analyses, the release option should be set to 0.

Maximum shear rate

This data set specifies the maximum shear rate, based on the resin manufacturer's data. It is not used in the analysis directly; however, it should be used to evaluate the shear rate data calculated by C-MOLD analyses to make sure that it does not exceed the maximum value.

As the cavity fills, layers of the polymer melt flow parallel to each other. The layer adjacent to the wall is stationary, and other layers move at increasing rates the farther they are away from the wall. The maximum rate of this layer movement occurs somewhere between the mold wall and the center of the cavity. This layer movement of the polymer melt is called shearing.

Shear rate is the rate of movement of these layers. The shear rate is also called the deformation rate, or strain rate. The force per unit area acting on the fluid to produce this shearing action is called the shear stress.

Shear stress is a measure of force and shear rate (or strain rate) is a measure of deformation. The viscosity of the polymer is a function that relates the stress to the strain (or shear rate). Those fluids that exhibit a linear stress-strain behavior are known as Newtonian fluids. Typically, most polymer melts are non-Newtonian; they exhibit a non-linear stress-strain relationship. The viscosity of polymer melts usually decreases as the shear rate increases. This type of behavior is termed pseudoplastic.

Increasing the shear rate or shear stress to above certain critical values would lead to material degradation. It also would lead to flow instabilities, such as melt fracture. These critical levels of shear rate and shear stress depend on the nature of the polymer and must be determined experimentally. These values are usually obtained directly from the resin manufacturer. For some materials, this data also is available in C-MOLD Database.

The shear-rate and shear-stress levels should be kept below these maximum, critical values. Representative outputs are available from the analysis. Considerations should be given to ram speed, gate dimensions (and type of gate), and injection pressure to obtain more favorable shear rates and shear stresses.

T-CODE#

14000

Units (SI)

1/s

Warning

This data set is not used in the analysis directly; however, it should be used to evaluate the shear rate data calculated by C-MOLD analyses to make sure that it does not exceed the maximum value.

These values should be obtained from the resin manufacturer. For some materials, this data also is available in C-MOLD Database.

Maximum shear stress

This data set specifies the maximum shear stress, based on the resin manufacture's data. It is not used in the analysis directly; however, it should be used to evaluate the wall shear stress data calculated by C-MOLD analyses to make sure that it does not exceed the maximum value.

As the cavity fills, layers of the polymer melt flow parallel to each other. The layer adjacent to the wall is stationary, and other layers move at increasing rates the farther they are away from the wall. The maximum rate of this layer movement occurs somewhere between the mold wall and the center of the cavity. This layer movement of the polymer melt is called shearing.

Shear rate is the rate of movement of these layers. The shear rate is also called the deformation rate, or strain rate. The force per unit area acting on the fluid to produce this shearing action is called the shear stress.

Shear stress is a measure of force and shear rate (or strain rate) is a measure of deformation. The viscosity of the polymer is a function that relates the stress to the strain (or shear rate). Those fluids that exhibit a linear stress-strain behavior are known as Newtonian fluids. Typically, most polymer melts are non-Newtonian; they exhibit a non-linear stress-strain relationship. The viscosity of polymer melts usually decreases as the shear rate increases. This type of behavior is termed pseudoplastic.

Increasing the shear rate or shear stress to above certain critical values would lead to material degradation. It also would lead to flow instabilities, such as melt fracture. These critical levels of shear rate and shear stress depend on the nature of the polymer and must be determined experimentally. These values are usually obtained directly from the resin manufacturer. For some materials, this data also is available in the C-MOLD Database.

The shear-rate and shear-stress levels should be kept below these maximum, critical values. Representative outputs are available from the analysis. Considerations should be given to ram speed, gate dimensions (and type of gate), and injection pressure to obtain more favorable shear rates and shear stresses.

The shear-stress level should be kept low during the filling stage to improve surface finish and part quality.

As a rule of thumb, the maximum shear-stress level should be below 20 x *, the stress level at which the viscosity changes from Newtonian behavior to shear-thinning behavior. * is one of the Cross-exp viscosity model constants.

T-CODE#

14002

Units (SI)

Pa

Warning

This data set is not used in the analysis directly; however it should be used to evaluate the wall shear stress data calculated by C-MOLD analyses to make sure that it does not exceed the maximum value.

The shear-stress level should be kept low during the filling stage to improve surface finish and part quality.

Minimum and maximum melt temperatures

This data set specifies the recommended minimum and maximum melt temperature values. The minimum and maximum melt-temperature values depend on the type of polymer, as well as the part geometry. These values are not used directly by C-MOLD analyses.

An optimum melt temperature exists. This data can be obtained directly from the resin manufacturer or through trial and error. Recommended melt temperature ranges for various generic grades of resins are available in the C-MOLD Database, along with data for certain commercial grades. Typically, the upper range of temperatures provided by the manufacturer is used to mold thin sections, while the lower range is used to mold thick sections.

The melt temperature should be such that material can be forced into the cavity with relative ease. On the other hand, it should not be so low as to cause difficulty in filling by requiring high injection pressure. A combination of low melt temperature and high pressure often causes quality control problems and high warpage.

High melt temperature coupled with long residence time might lead to material degradation. Higher melt temperatures also require more time to cool and thus add to the overall cycle time.

Melt temperatures influence the degree of molecular orientation in the part, which in turn affects the final part quality.

T-CODE#

14004

Units (SI)

K

Warning

These values are not used directly by C-MOLD analyses. However, a warning message will be issued if the inlet melt temperature value exceeds the maximum or falls below the minimum melt temperature value.

Minimum and maximum coolant temperatures

This data set specifies the recommended minimum and maximum coolant temperatures. These values are not used directly by C-MOLD analyses.

The coolant temperature determines the mold-wall temperature. For effective cooling, the mold temperature must be kept at some optimal value. High mold temperature requires more time to cool and leads to longer cycle time, while low mold temperature might cause difficulty in filling and lead to short shot. This range of coolant temperatures is usually obtained from the manufacturer. Recommended values of mold temperature for various generic grades of resins are available in the C-MOLD Database, along with data for certain commercial grades.

The mold temperature also affects crystallization rate, which can affect the final part quality.

The optimum mold temperature is unique to every polymer and type of geometry.

T-CODE#

14006

Units (SI)

K

Warning

This data set is not used directly by C-MOLD analyses.

Data Sets Used in the Finite Element Mesh File

Nodal Properties: 20000-29999

Entrance for polymer

This nodal property is the location at which the melt enters the melt delivery system or the part. The information is mapped to the nodal property table in the finite-element mesh file.

T-CODE#

20000

No. of Properties

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Point Type: Polymer Entrance

Entrance for coolant manifold: (coolant manifold ID)

This nodal property is the location of the coolant entrance. This property points to the coolant manifold ID, as specified in T-CODE 11100, for inlet coolant temperature, total rate/pressure drop, and coolant material.

T-CODE#

20010

No. of Properties

1

Range

Integer from 1 to 32767

Default value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Point Type: Coolant Entrance
Coolant Manifold ID

Exit for coolant manifold: (coolant manifold ID)

This nodal property is the location of the coolant exit, and points to the coolant manifold ID.

T-CODE#

20012

No. of Properties

1

Range

Integer from 1 to 32767

Default value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Point Type: Coolant Exit
Coolant Manifold ID

Entrance for gas

This nodal property is the location at which the gas enters the gas delivery system or the part. The gas entrance and polymer entrance can be at separate locations.

T-CODE#

20020

No. of Properties

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Point Type: Gas Entrance

Node related to parting plane

This nodal property requires three nodes to determine the parting plane. The parting plane is defined as the normal of three nodes.

The parting plane normal defines the machine direction in which the clamp force is calculated. The default parting plane normal is along the z-axis of the global model coordinates.

T-CODE#

20030

No. of Properties

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Point Type: Parting Plane

Node related to fiber mat orientation

The first principal directions of the anisotropic fiber mat are defined by the reference vector which is defined by connecting two nodes. The reference vector will propagate over the entire cavity using Lay-flat technique.

T-CODE#

20050

No. of Properties

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Point Type: Orientation Vector

Nodal fixity

This nodal property refers to a known degree of freedom of the part in the service. At any point (or node) of a part there are six degrees of freedom (displacements in X, Y, and Z directions; rotations around X, Y, and Z axes), and they may be partially and totally constrained during the service.

Fixities are normally along the boundary edges (known as boundary conditions) where some displacements are fixed as zero, and they are defined by setting the corresponding displacements to zero for the service loading analysis. Fixities can also be applied where a screw is used to fix the part. Minimally, enough fixities must be supplied to fix the rigid-body movement for the service loading analysis, or the analysis will not converge. Rigid-body movement can be in X, Y, and Z directions, or rotate around X, Y, and Z axes; thus, the six degrees of freedom must be fixed through single or multiple nodes.

Constrained fixity has a value of 1, and unconstrained fixity has a value of 0.

T-CODE#

20100

No. of Properties

6

Range

0, 1

Default Value

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Nodal X Displacement
Nodal Y Displacement
Nodal Z Displacement
Nodal X Rotation
Nodal Y Rotation
Nodal Z Rotation

Elemental Properties: 30000-32000

Plastic element

The following is true for this elemental property: type=1 for part elements (default); type=2 for sprue/runner/gate elements; and type=3 for parison elements.

Plastic elements should also come with a mandatory element property of the thickness/diameter and shape factor (T-CODE 30100).

Optional element properties are the initial fill condition (T-CODE 30102) and the hot runner manifold ID (T-CODE 30104).

T-CODE#

30000

No. of Properties

1

Range

1, 2,3

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Region Type: Part Wall
Region Type: Parison or Sheet
Path Type: Part Runner
Path Type: Hot Runner
Path Type: Cold Solid Runner
Path Type: Parison or Sheet

Channel element

The following is true for this elemental property: type=1 for regular channel (default); type=2 for baffle; type=3 for bubbler; and type=4 for hose.

Channel elements should come with mandatory element properties of the diameter and shape factor (T-CODE 30100).

T-CODE#

30002

No. of Properties

1

Range

1, 2, 3, 4

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Path Type: Cooling Channel
Path Type: Cooling Baffle
Path Type: Cooling Bubbler
Path Type: Cooling Hose

Connector element (multiplicity factor)

The multiplicity factor gives the number of symmetric branches at the downstream of a connector (default=1).

T-CODE#

30004

No. of Properties

1

Range

Integer from 1 to 256

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Path Type: Connector
Connector Multiplicity

Mold element

The following is true for this elemental property: type=1 for cavity element (default); type=2 for exterior mold element; and type=3 for parting plane element.

Note: Exterior mold element, type=2, is not supported in v4.0, but reserved for future versions.

T-CODE#

30006

No. of Properties

1

Range

1, 2, 3

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Path Type: Mold Face
Path Type: Parting Plane
Region Type: Mold Face
Region Type: Parting Plane

Thickness/diameter and shape factor

The first value is thickness for TRI elements, and diameter for 1-D elements. The shape factor is used to describe non-circular runner or part surfaces with irregular cross-sections.

In the case of TRI elements, the shape factor is defined as ,

where t is the averaged thickness based on volume, S is the total top and bottom surface areas, and V is the volume between top and bottom surfaces.

In the case of 1-D elements, the shape factor is defined as ,

where d is the equivalent diameter based on , C is the perimeter, and A is the cross-sectional area.

The shape factor is equal to one for flat surface and circular runners.

T-CODE#

30100

No. of Properties

2

Units (Thick/diam)

meters

Range (Thick/diam)

1.0e-9 to 1.0

Range (Shape factor)

0.1 to 10.0

Def.Val.(Shape factor)

1.0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Thickness
Starting Diameter
Shape Factor

Initial fill condition

The following is true for this elemental property: f = 0 for element initially empty (default); f = 1 for element initially filled with polymer melt at inlet melt temperature; and f = 2 for element initially filled with polymer melt at hot runner manifold temperature.

T-CODE#

30102

No. of Properties

1

Range

0, 1, 2

Default Value

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Init. Fill: Empty
Init. Fill: Inlet Temp.
Init. Fill: Hot Runner Temp.

Hot runner manifold ID

This elemental property points to the hot runner manifold control (T-CODE 11200) for wall temperature of the hot runner.

This property is the optional element property for hot runner.

T-CODE#

30104

No. of Properties

1

Range

Integer from 1 to 32767

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Hot Runner Manifold ID

Valve-gate timer ID

This elemental property points to the timer for the valve gate opening (T-CODE 10202) for the valve-gate opening time.

T-CODE#

30106

No. of Properties

1

Range

Integer from 0 to 32767

Default Value

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Valve-gate Timer ID

Mold ID

This elemental property is specified to control the mold closing in the blow molding process. It points to the Mold ID in T-CODE 13020 and T-CODE 13030.

This property is the optional element property for mold elements.

T-CODE#

30110

No. of Properties

1

Range

Integer from 1 to 32767

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Mold Component ID

Mold material ID (positive side ID, negative side ID)

The first mold material properties will be used if the mold material ID is 1, and the second mold material properties will be used if the mold material ID is 2.

This elemental property is the optional element property for planar and 1-D elements; only positive side ID is used for 1-D elements.

T-CODE#

30112

No. of Properties

2

Range

1, 2

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Pos. Side Mold Mtl. ID
Neg. Side Mold Mtl. ID
1-D Mold Mtl. ID

Fiber mat ID

This elemental property points to the fiber mat ID in T-CODE 03920.

This property is the optional element property for planar elements. It is only used by the RTM/SRIM feature of C-MOLD Reactive Molding.

T-CODE#

30120

No. of Properties

1

Range

Integer from 1 to 32767

Default Value

1
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Fiber Mat ID

Tapered angle (x,y,z, )

The tapered angle, , is defined as the tapered angle from node 1 to node 2. The diameter at node 2 is greater than the diameter at node 1 if the tapered angle is positive.

The global coordinate of the starting point of the tapered runner is x,y,z. It should be coincided with the axis of the element.

This elemental property is the optional element property for runner elements.

T-CODE#

30200

No. of Properties

4

Units (x,y,z)

meters

Units (angle)

radians

Range (angle)

-/4 < angle < /4

Def. Val. (angle)

0
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Taper Half-Angle
Starting Diameter
Ending Diameter

Runner diameter limits (maximum diameter/minimum diameter)

The default maximum diameter is the square root of part volume divided by runner length; the default minimum diameter is 0.0015 m.

The runner diameter will not be changed if the maximum diameter and minimum diameter are equal.

This property is the optional element property for runner element.

T-CODE#

30202

No. of Properties

2

Units (max.)

meters

Units (min.)

meters
Related Attributes (see C-MOLD Modeler & Visualizer User's Guide)

Min. Allowable Diameter
Max. Allowable Diameter

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