Interfaces in Native Mode
The default interface type for mated surfaces in native mode is bonded, meaning that the surfaces will share nodes and Creo Simulate will, in effect, treat them as merged surfaces. If this is undesirable, click > 
Interface in native mode to open the Interface Definition dialog box. Specify which surfaces you want Creo Simulate to treat as free interfaces during meshing and analysis. You can assign free interfaces for any mated surfaces in your assembly that you do not want Creo Simulate to treat as bonded.
Interface in native mode to open the Interface Definition dialog box. Specify which surfaces you want Creo Simulate to treat as free interfaces during meshing and analysis. You can assign free interfaces for any mated surfaces in your assembly that you do not want Creo Simulate to treat as bonded.The Interface command is available only if you have a 3D assembly open. You can define free interfaces for the following types of entity pairs:
• Solid—solid
• Solid—shell
• Solid—midsurface
• Shell—shell
• Shell—midsurface
• Midsurface—midsurface
To define a free interface on a midsurface, you select the surface that will be compressed to a midsurface.
If your assembly includes components modeled with midsurfaces, Creo Simulate compresses these components during meshing, potentially creating gaps in the assembly. To prevent these assembly gaps, Creo Simulate creates automatic midsurface connections where the original surfaces of midsurface components mate or overlap with surfaces from other assembly components. If you want to avoid these automatic midsurface connections, you can define a free interface between the overlapping surfaces. In this case, your model will have inconsistent meshes for the contacting components where you have placed the free interfaces, and there will be assembly gaps at the free interfaces.
When you define an interface as Free, Creo Simulate outlines the interface and adds an interface icon to your assembly. When you transfer the assembly to independent mode Creo Simulate, the free interfaces will be outlined with a bold border.
Keep the following in mind if you work with your assembly in both native mode and FEM mode:
• The default interface type in native mode is Bonded. You cannot change the definition of the default interface type in native mode, but you can in FEM mode. If you define the default type in FEM mode as Free, and then enter native mode, Creo Simulate uses a default interface type of Bonded.
• If you specify a Bonded interface for surfaces in your assembly in FEM mode, and then enter native mode, the bonded interface definition will be suppressed.
Return to About Interfaces or Results When Using Automatic Connections.