About Skeleton Models
When you use a skeleton model, you set the design and motion intent at the beginning of the design process for a part or subassembly. A skeleton model, placed in the assembly and propagated with it, can be developed independent of the assembly and inserted seamlessly at any time. A skeleton model can be used in more than one assembly.
A skeleton model can be created at any time in the design process. The system always lists and regenerates the newly created skeleton model before all the other components and assembly features.
Skeleton Models and Motion Skeleton Models
There are two types of skeleton models: standard skeleton models and motion skeleton models. You create standard skeleton models in an open assembly as parts. Motion skeleton models are subassemblies that contain design skeletons (standard skeletons or internal sketches) and body skeletons. You create standard skeletons using curves, surfaces, and datum features. They can also include solid geometry.
Although skeletons models can only be created in an assembly, you can retrieve, manipulate, and save them as ordinary parts (standard skeleton models) or assemblies (motion skeleton models). Body skeletons are automatically saved as parts when you create them.
Important Considerations for Skeleton Models
Before creating a skeleton model, consider the following points:
• Only one motion skeleton can be created or inserted in an assembly.
• Multiple standard skeletons can be created in an assembly when the multiple_skeletons_allowed configuration option is set to yes.
• A skeleton model is similar to any other assembly component. It has features, layers, relations, views, rigid bodies, and so on.
• External reference control settings can be used to restrict geometry and assembly placement references to skeleton models only. ( > > 
Model Properties and click change in the Reference Control line to open the External Reference Control dialog box.) These options control references for all skeletons in the assembly.
Model Properties and click change in the Reference Control line to open the External Reference Control dialog box.) These options control references for all skeletons in the assembly.• Skeleton models can maintain their own family tables. This means that assemblies can maintain different skeleton instances across a family table.
• All simplified representation functionality available in Part and Assembly mode is available for skeleton models (beginning with Pro/ENGINEER 2001).
• Skeleton models can be selected By Rule when you manage simplified representations.
Skeleton Models in BOMs and Model Trees
Skeleton models do not show up in the BOM unless you specifically include them. They do not contribute to mass or surface properties. They can be displayed in drawing views and can be included during the creation and manipulation of simplified representations and external shrinkwrap features.
Skeleton Parts and Motion Skeletons in the Model Tree
Skeleton parts and motion skeletons are placed in the Model Tree before components with solid geometry. Because the functional characteristics of skeletons are different from other components, they are identified in the Model Tree and Mechanism Design Model Tree by the following icons:
• 
—Standard skeletons and body skeletons
—Standard skeletons and body skeletons• 
—Motion skeletons
—Motion skeletons | Skeleton models created prior to Release 20.0 are blue by default. This color cannot be changed. Starting with Release 20.0, a component color is set only to the model, not to the component. You can create a user-defined color to display new skeleton models. |