Meshing a model

The quality of the mesh used in your analysis will determine the accuracy of your results.

The models you have worked with so far have already been meshed, but this is not how a model will be imported from a CAD program.

In this task, you will:

• Import a CAD model
• Generate a mesh on the model
• Compare the effect of different mesh densities

A Dual Domain mesh is the imported mesh type that is usually selected, and the one you will select. The reasons for this are:

• Most part geometry is shell-like in appearance, which is suitable for Dual Domain analysis.
• Midplane meshes usually require more cleanup than Dual Domain meshes.

  When an analysis that can only be performed on a midplane mesh is required, the mesh is usually generated in an external CAD package and imported as a midplane mesh.

• A 3D mesh requires a good Dual Domain mesh of the model as its starting point. This Dual Domain mesh is then converted into a 3D mesh. A solid part that obviously requires a 3D mesh analysis would still be imported as a Dual Domain mesh.

1. Ensure the Mesh tutorial project you used in the previous task is active. If it is not already open, click ( Get Started tab > Launch panel > Open Project) and select Mesh tutorial.
2. Click (Home tab > Import panel > Import).
3. In the Files of type drop down list, select IGES(*.igs,iges).
4. Navigate to Tutorial folder, typically C:\Program Files\Autodesk\Simulation Moldflow Insight 20xx\tutorial.
5. Select Dustpan.IGS and click Open.
6. In the Import dialog, ensure Dual Domain is the mesh type selected.
   Note: If you have Autodesk Simulation Moldflow Design Link installed, you can check the Process using Autodesk Simulation Moldflow Design Link option to improve the quality of the imported mesh.
7. Click OK.

   Later in this task, you are going to compare two different mesh densities. You need to duplicate this model so that you can compare results.

8. Select Dustpan_study in the Study Tasks pane.
9. Right-click on Dustpan_study and select Duplicate from the drop-down menu.
10. Right-click on Dustpan_study (copy) , and select Rename from the drop-down menu.
11. Enter the new study name Dustpan_mesh and click Enter.
12. You will now generate a Dual Domain mesh for this part. Double-click Dustpan_study in the Study Tasks pane.
13. In the Study Tasks pane, double-click Create Mesh.

    The Generate Mesh pane of the Tools tab appears.

14. Ensure the General tab is selected.
15. Note the suggested Global edge length of about 11.2 mm.
16. Click Preview. A representation of the major nodes that you will generate is shown.
17. Change the Global edge length to 5 mm.
18. Click Preview to view the finer mesh your change would represent.
19. Click Mesh Now. The Mesh Generation message dialog appears. Click Close to dismiss the dialog and begin the meshing operation. The generation of the mesh will take a short time. The Mesh Complete message dialog appears. Click OK to dismiss the dialog.
20. Rotate and zoom in on the part to investigate the mesh, especially at rounded corners and thin edges.
21. In the Study Tasks pane, note that the third line down now identifies the mesh type as Dual Domain Mesh . Note the number of elements in the mesh.

    Although a finer mesh gives a better result, there is a point beyond which additional mesh density fails to increase the value of the analysis results and only increases computational time.

22. Double-click Dustpan_mesh in the Study Tasks pane.
23. In the Study task pane, double-click Create Mesh.
24. Ensure the General tab is selected.
25. Leave the Global edge length at the default (about 11.2 mm).
26. Click Mesh Now. Close the message dialogs that appear before and after the meshing operation.
27. When the mesh has been created, rotate the part to investigate the mesh.
28. In the Study Tasks pane, note the number of elements in the mesh. This mesh has fewer elements than the first model.

    The mesh density should be optimized as far as possible. It is advisable to accept the default Global edge length as an initial estimate. This length is often too coarse and may have to be refined to one-third to one-half of the initial value. Alternatively, a Global edge length should be about 2 times the nominal wall thickness for a 3D mesh, and 2 to 5 times the nominal wall thickness for a Dual Domain mesh. You will now alter the mesh density.

29. Make sure the Dustpan_mesh study is the active study.
30. In the Study Tasks pane, right-click Dual Domain Mesh.
31. Select Generate Mesh.
32. From the General tab, alter the Global edge length to 8.5 mm.
33. Check the Remesh already meshed parts of the model checkbox that is located above the Mesh Now button.
34. In the Layers panel, if IGES Surface and IGES Curves are listed, ensure they are not ticked.
35. Click Mesh Now. Close the message dialogs that appear before and after the meshing operation.
36. The mesh density of the model has been altered. In the Study Tasks pane, note the updated number of elements in the mesh.
37. From the Application menu , click (Close > Project). Save each study if you are prompted to do so.

Click the Next topic link below to move on to the next task of the tutorial.