Creo Simulate > Reference Links > Omit Unopposed Surfaces
  
Omit Unopposed Surfaces
If you omit unopposed surfaces from a pair, Creo Simulate compresses the model differently depending on the following factors:
Whether the surface you omitted is the top surface or bottom surface of the pair.
The state of the Remove Unopposed Surfaces check box on FEM Mesh Settings dialog box in FEM mode or the AutoGEM Settings dialog box in native mode.
For example, if you designed a collet and wanted to constrain a small section of the outside surface, you might add a region to the model. If you then omitted the region from your pairing scheme, Creo Simulate would compress and subsequently analyze the model differently depending on which surface was the top surface. To see how the compression results change when the unopposed surface is the top or bottom surface of the pair, see the collet cross section illustration.
After you pair your model, you can inspect the pairing scheme using the Simulation Geometry dialog box.
Return to Unopposed Surfaces.