Here are two instances during which the rigid dynamics solver tries to mesh the parts: 1. When you are doing rigid-flexible body dynamics; only the parts that are marked as flexible are meshed. 2. When you have any contacts defined in your model; the contact algorithm uses the mesh nodes as contact detection points so it creates a surface mesh on the faces that are included under contact/target scoping. If you don’t have either of these things defined in your model, the rigid dynamics solver should not generate any mesh on the rigid bodies.