You can add a Center of Mass (COM) point to an assembly. COM points added in component files also appear in the assembly.
The position of the COM point updates when the model's center of mass changes. For example, the position of the COM point updates as you add, modify, delete, or suppress components or add or delete assembly features. The COM point can be useful when you are designing assemblies requiring balanced mass (for example, to avoid excessive vibration).
In an active assembly, operations for the center of mass and equations linked to mass properties are updated only when they take 0.5 seconds or less. If the update takes more than 0.5 seconds, the center of mass and equations are marked with 
, and are not updated until you initiate a rebuild manually.
The calculation of the center of mass includes:
- Hidden components
- Lightweight components. However, COM and COMR points created in the component files of lightweight components are not visible in the parent assembly.
To exclude a component from the calculation of center of mass, make it an envelope component.
You can mate to the COM points of an assembly’s components in distance, coincident, and concentric mates. You cannot mate to the COM point of the assembly itself.
If you add COM points or Center of Mass Reference (COMR) points in component files, the points appear in the parent assembly:
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Center of Mass, part |
Indicates the center of mass of a component that is a part. Defined in the part document. |
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Center of Mass, subassembly |
Indicates the center of mass of a component that is a subassembly. Defined in the subassembly document. |
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Center of Mass, part, user-defined |
In an assembly, indicates a user-defined center of mass of a component that is a part. Defined in the part document, in the Override Mass Properties dialog box. |
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Center of Mass, subassembly, user-defined |
In an assembly, indicates a user-defined center of mass of a component that is a subassembly. Defined in the subassembly document, in the Override Mass Properties dialog box. |
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Center of Mass Reference Point |
Indicates the center of mass of the features above the point in the FeatureManager design tree of the part. |
For example, in this assembly, 
indicates the center of mass of the assembly, and indicates the centers of mass of three component parts:
If the COM and COMR points are not visible, click
View Center of Mass 
(View toolbar) or .