CMM: Choosing B-Rep or Feature Migration

By Addison_Moore

Before beginning migration, there is an important question to answer. Should your items be migrated as B-Reps or with Features? A B-Rep, or Boundary Representation, migration will create an NX part using a body feature that maintains the item fidelity. That is, the NX part will match the source’s surface area and volume, as well as pass a point-to-point comparison. Feature migration will create the item in NX using the same feature “recipe” as the source CAD system.

The answer to this question will vary depending upon the user’s needs, however, the Siemens migration team typically recommends an 80/20 split of B-Rep to Features. Why choose B-Rep migrations, and why so much? Well to start, B-Rep migrations have an expected success rate of 99.9%. Additionally, though B-Rep items are not built with features, they can still be modified using NX Synchronous Modeling and new features can be created using traditional modeling techniques. B-Rep migration also saves time, as CMM will process items more quickly and post-migration repair should be unnecessary. B-Rep migration is therefore perfect for archived data that is no longer in design and especially if they are not receiving any engineering changes, which usually makes up the majority of a user’s data.

That brings us to migration with Features. This migration method is ideal for items that are still in design. Items migrated with this method will be built with fully parametrized features just as they were in the source CAD system, enabling continued design and engineering changes. If a feature migrates unsuccessfully it will be recovered by creating a body feature that maintains the item fidelity at that moment in the part’s creation (allowing subsequent features to still be accurate). This means that all items should still have accurate item fidelity, but unsuccessful features will need to be repaired for the part to be fully parametric.

The 80/20 split for B-Rep/Features is a rule of thumb and is not perfect for everyone. The migration team at Siemens is happy to discuss with users to help determine the best plan for their data.

Be sure to check back next week on Migration Monday to learn more about the installation of CMMFor more information, or to get started migrating to NX with the Content Migration Manager, please contact your local Siemens PLM Software representative!

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This article first appeared on the Siemens Digital Industries Software blog at