Topology Optimization Warning: Loads or constraints applied to empty (keep out)

Topology Optimization Warning: Loads or constraints applied to empty (keep out)

Loads and constraints need to be applied to faces that will survive the optimization. For example, a pin hole might have been considered a Keep Out region for the optimization, but this feature most likely needs to survive the optimization, so it needs to be changed to a Shell which is a combination of a Keep Out and Keep in.  A Keep Out (no material in that space) is an area where faces are not maintained and can be optimized away - any applied constraints or loads will fail for a Keep Out.  The pin hole itself is a Keep Out, but the Shell offset is a Keep In. Thus, the pin hole is maintained as a cylindrical hole with a minimum wall thickness of the Shell offset, and the applied load or constraint is maintained.  The Shell is an important tool in the toolbox for Topology Optimization, and the definition needs to be applied appropriately to the model.