Creo Simulate > Reference Links > Connected and Unconnected Parts
Connected and Unconnected Parts
After you start a run, Creo Simulate merges the individual parts into a single, multivolume body, where individual parts are either connected or unconnected.
Merging of the individual parts is as follows:
If parts in an assembly touch, Creo Simulate views the touching parts as individual volumes with common faces (surfaces) or edges (curves). In this case, the software recognizes an association between the volumes and treats that portion of the assembly as a single Creo Simulate body with multiple volumes. Interfaces are created between the individual parts to connect them. You can specify the default type of interface for your model.
One exception occurs if the common faces separating two volumes have contact interface. Contacts allow the two volumes to separate during the simulation.
If you compress the parts using midsurface compression, you can use end welds or perimeter welds, or let the software create automatic midsurface connections, to eliminate the gaps that occur between mating edges or surfaces of the parts. This ensures that touching entities remain connected. For more information, see Gaps in Assemblies.
If a part does not touch any other part, the part is treated as an unconnected body.
Depending on the tolerance between parts and the degree to which parts touch, Creo Simulate may or may not connect some of the parts in an assembly. For example, if you create the following assembly, the parts get connected as shown:
The two rectangular parts are close enough to be within tolerance, and they share enough surface to merge them into a single body. However, the sphere and rectangle have only one point of contact. Therefore, Creo Simulate does not merge the sphere with the rest of the assembly. In this case, the assembly would contain two connected parts and one unconnected part—two bodies in all.
Before you run an analysis or design study, you are prompted as to whether you want error detection. If you do, Creo Simulate checks for various modeling conditions including the presence of multiple bodies in the model. Should it encounter more than one body, Creo Simulate displays a message indicating the number of separate, or disjoint, bodies it finds. You can use this information to determine whether parts you thought were connected are truly connected. If you see an unexpected number of bodies, you may want to cancel the analysis or study and correct the assembly.
Return to Assembly Considerations.