# Best Practice for Configurations with External References

If a part contains external references from a multiconfiguration assembly, best practice is to have a corresponding part configuration for each assembly configuration.

With a multiple-to-one (n:1) relationship, only the most recently updated assembly configuration is up to date. The other assembly configurations are out-of-date, and can take time to rebuild when you activate them. Also, the different versions of the part's single configuration do not have unique identifiers, which could result in the wrong version being manufactured or purchased.

Best practice is to have a one-to-one (1:1) relationship between configurations of the assembly and the configurations of the part.

## Example

An assembly named Stack has a stack of blocks on a part named Fixture. You want the height of Fixture to be 20mm higher than the stack of blocks. That is, if the height of the stack of blocks is H, then the height of Fixture is H+20.

The assembly has three configurations. Each configuration has different sized blocks, and therefore different values for H. The fixture is created in the context of the assembly, and its height is defined as being offset 20mm from the face of the top block.

## Problem:

n:1 Relationship - Not Recommended

Several configurations of the assembly reference a single configuration of the part.
 Assembly: Stack (Small) Stack (Medium) Part: Fixture (Default) Fixture (Default) Assembly: Stack (Large) Part: Fixture (Default)
Assembly Configuration Height (H) Part Configuration Height (H+20)
Small 30 Default 50? 65? 80?

Depends on which assembly configuration is active.

Medium 45
Large 60
Up-to-date configuration data is saved only for the most recently updated assembly configuration, because the height of Fixture is out of date for the other two configurations. For example, if you activate assembly configuration Large, then the height of Fixture is 80. Therefore, for configurations Small and Medium, the height of Fixture is out of date.

## Solution:

1:1 Relationship - Best Practice

For each assembly configuration, create a corresponding configuration in the part.
 Assembly: Stack (Small) Stack (Medium) Part: Fixture (Short) Fixture (Average) Assembly: Stack (Large) Part: Fixture (Tall)
Assembly Configuration Height (H) Part Configuration Height (H+20)
Small 30 Short 50
Medium 45 Average 65
Large 60 Tall 80
Now each version of Fixture has a unique identifier. Up-to-date configuration data is saved for each assembly configuration. Time to switch between assembly configurations improves because the data does not need to be rebuilt.