You can create masses within a project (in-place masses) or outside a project (loadable mass families). In-place masses are used for mass forms that are unique to a project. Loadable mass families are typically used when you will be placing multiple instances of the mass in a project, or when you will use mass families in multiple projects.
To create in-place masses and loadable mass families, use the conceptual design environment. You can nest other mass families into the mass family that you are creating. (See GUID-A3097388-C28F-4425-877A-406038BCD55F.htm#WS1A9193826455F5FF-7F10494411F03A24F24-6CEC.)
If you are importing geometry into a family, see Considerations for Imported Geometry in Mass or Generic Model Families.