Procedures for Executing the Analysis

Use the Analysis area of the C-MOLD Control Panel to choose the analysis. Select Design Diagnostics. Then, from the list, select Integrated Shrinkage & Warpage Analysis.

At this point, you may optionally modify parameters. Parameters are constants that control the execution of the analysis. Default values are provided; however, if you decide to modify these, select Analysis Parameters from the Design Diagnostics menu. The parameters are described at the end of this chapter.

Next, to launch the analysis, select either Run Now or Run as Batch from the Design Diagnostics menu. If you choose Run Now, C-MOLD will display the input data and the status of the analysis on the screen. If you choose Run as Batch, an analysis log file (design_name.owl) will be generated, which you may examine later. Chapter 7 provides an example analysis log file.

Note: Experienced users can alternately launch a C-MOLD Integrated Shrinkage & Warpage Analysis directly from the keyboard, rather than from the Control Panel. The appropriate command is cmlaunch, documented in Appendix E.

At the beginning of program execution, C-MOLD Shrinkage & Warpage produces a report (on the screen or in the log file) of the parameters, material properties, process conditions, and statistics of the finite-element mesh used in the analysis. As the analysis proceeds, the status of the calculations, such as the type of applied loading, and the convergence parameter for the iterative solver, are displayed.

C-MOLD Shrinkage & Warpage checks the validity of the input data at the beginning of program execution. Parameter values are checked to see whether acceptable values are used.

The finite-element model is checked for proper element connectivity, and zero dimensions or areas. If there is any problem with the geometry, a list of the problematic nodes or elements is displayed.

The value of each material property is checked, to assure that it is in a physically meaningful range. For example, elastic moduli and thermal expansion coefficients must be positive values. An error message will appear if a required material property is not defined, or if the specified value is not meaningful.

The analysis will stop execution whenever an error is detected, but it will continue execution when warning messages are displayed.

When execution of the analysis is complete, the results will be available for your evaluation, as described in the next chapter. Figure 1-1 presents a flow chart of a C-MOLD Integrated Shrinkage & Warpage Analysis design cycle.

Parameters

C-MOLD Integrated Shrinkage & Warpage consists of polymer melt filling and post-filling, mold cooling, residual stress, and structural analyses. Therefore, you should make sure to specify the parameters necessary for all these analyses.

• For information on parameters related to the polymer melt analysis, refer to the C-MOLD Filling & Post-Filling User's Guide.
• For information on parameters related to the mold cooling analysis, refer to the C-MOLD Cooling User's Guide.
• For parameter information that is global to all C-MOLD analyses, refer to Getting Started With C-MOLD.
• This C-MOLD Shrinkage & Warpage User's Guide describes only the parameters that pertain specifically to the residual stress and structural analyses.

• Create / Edit Parameter File displays a template of parameters and their current values, which you may change. To customize a parameters template, select Options from the Control Panel, as described in Getting Started With C-MOLD.
• Use Existing Parameter File allows you to select a previously created set of parameters and values.
• Use Defaults specifies that the default parameter values will be used for the analysis.

The Parameter File

Parameters Specific to C-MOLD Shrinkage & Warpage

Residual stress analysis (W)

This parameter must be set to one. It specifies that a residual stress analysis will be performed. The residual stress analysis is required by C-MOLD Integrated Shrinkage & Warpage Analysis.

Option for structural analysis (W)

This parameter specifies whether C-MOLD will create interface files for ABAQUS structural analysis software. If this variable is assigned a value of 1, an interface file to ABAQUS with the linear option is generated. If a value of 2 is assigned to this variable, an interface file to ABAQUS with the non-linear option is generated. (Note that if a value of 1 is assigned to the parameter isolate mechanism for warpage, a total of three files will be generated: filename.inp, filename_s.inp, and filename_c.inp. Otherwise, only filename.inp is generated.)

No parameter is required to create an interface file to ANSYS. C-MOLD Integrated Shrinkage & Warpage Analysis generates the interface file filename.neu, or, if you are including fiber orientation analysis, the file filename.ppt. Interface files are discussed in Appendix F of the C-MOLD Reference Manual.

Isolate mechanism for warpage (W)

If the value of this parameter is set to 1, C-MOLD Shrinkage & Warpage separates the total shrinkage results into the following:

• non-uniform shrinkage
• shrinkage due to unbalanced cooling

By isolating the shrinkage and warpage mechanisms when examining output data, you can identify the dominant mechanism causing post-molding deformation. Based on that information, appropriate action can be taken to optimize the part design. This option is quite helpful, though note that the separation of the mechanisms of shrinkage and warpage is heuristic and cannot be proven in a rigorous mathematical way for any part geometry, because the terms shrinkage and warpage themselves cannot be given an exact mathematical definition. Shrinkage and warpage are measured by displacement. Further discussion of the isolation of the mechanisms of shrinkage and warpage can be found in the next chapter.

Stress analysis w/o C-COOL (W)

If the value of this parameter is set to 0, C-MOLD Integrated Shrinkage & Warpage Analysis executes the cooling analysis. If the value of this parameter is set to 1, the cooling analysis is not executed. Setting the value to 1 assumes a constant mold temperature, and simplifies the analysis.

Option for nonlinear structural analysis (W/O)

If the value of this parameter is set to 0, C-MOLD Shrinkage and Warpage will perform a linear analysis. If a value of 1 is assigned, C-MOLD will perform a nonlinear structural analysis.

Maximum number of iterations for nonlinear structural analysis(W/O)

This parameter is used for nonlinear structural analysis only. A nonlinear structural analysis consists of linear iterations, which should converge to a solution. The purpose of this parameter is to prevent an excessive number of iterations that may otherwise occur in some cases. If the analysis does not converge within the maximum number of iterations, the analysis stops and the result of the last iteration is reported.

If you have set the Option for nonlinear structural analysis to 1 (nonlinear), then the default value of the Maximum number of iterations for nonlinear structural analysis will be 20. You may change this value if you wish. Keep in mind that in general, the more a part deforms, the more iterations will be necessary.