Assembly Design > Assembly Design > Using Assembly > Working with Assemblies > About Entering Relations in Assembly
About Entering Relations in Assembly
You can add relations to parts or between parts within an assembly. Relations in Assembly follow the standard rules for relations except that you must first specify the model to which relations apply. This can be the main assembly, a subassembly, or a part. Once specified, all relation operations apply only to the specified model. For example, if the specified model is a part, the system shows only dimensions of the part in the assembly.
The notation you use to enter relations in Assembly differs from the notation you use to enter relations in Part mode.
In Assembly, for each assembly parameter, you must specify a session_ID that refers to a component in the assembly. The relations file contains a table that specifies the session ID for each part.
For example, parameters in an assembly appear for part with session_ID 1 as d0:1, d1:1, and d2:1; for part with session_ID 3, they appear as d0:3, d1:3, and d2:3. If you select a part in Assembly mode, you can enter the part relations either in Part format (d0 = 2*d1) or in Assembly format (d0:3 = 2*d1:3).
When using relations to relate parts within assemblies, keep in mind the following:
If the relation drives a part that is a member of the assembly, it does so only in the context of the assembly. (In Part mode, you can modify the driven value if the assembly containing the relation is not in memory.)
You can use assembly relations to drive dimensions only on dimensions driven by a family table.
You cannot add or edit an assembly relation that tries to drive a parameter that a part relation is already driving.
If you add a part relation that drives the same parameter as one that already exists in an assembly relation, the new part relation drives the parameter, but the system displays an error message during the assembly regeneration.