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Topology Optimization in Assemblies
You can optimize the topology of only one single component at a time in an assembly. Therefore, these items apply to topology optimization in assemblies:
All the references for the topology regions that are included in an optimization study must belong to the same component.
The default maximum element size control of 1.5% of the model size is applied only to components or volumes for which topology regions are defined, and not to the entire model.
Analyses, topology regions, design objectives, design constraints, and topology studies are available from the top-level assembly, but are suppressed from lower-level components.
When you construct the geometry from the results of an optimization study, only the one component that you optimized is constructed. You can manually replace the original component in the assembly with the optimized component later.