Assembly Design > Top Down Design > Data Sharing > Merge and Inheritance Features > Merge Features > Merge Restrictions
  
Merge Restrictions
The source part cannot be one of the following parts:
An assembly datum plane
A subassembly
An instance of a generic part (copy the part instance to another name and use the copy)
A sheetmetal part
The target part cannot be one of the following parts:
An assembly datum plane
A subassembly
The same part as part 1 (itself)
Part of an assembly pattern
In addition, the following rules apply:
If the target part references assembly components other than the source part, the assembly must be in session so that feature placement can be updated.
After removing material, delete or suppress the source part to view the merge part.
If you place the target part into the assembly using a Centered placement constraint with coordinate systems, all the assembly coordinate system references used for placement must belong to the source part.
Parts must be explicitly assembled. A part cannot be used if it was assembled using packaging options.
If you assemble a component that you have cut out to assembly datum planes, the system creates it without offset dimensions for component placement.
If you apply shrinkage by dimension to the reference model used in a remove material procedure, the model containing the Merge feature does not reflect the shrinkage dimensions. Original dimensions are used (before shrinkage).