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Model-Based Definition in the Tiers

Bruce Morey
By Bruce Morey Senior Technical Editor, SME Media

I had the privilege of researching and writing an article for the December issue of Manufacturing Engineering magazine on the topic of Model-Based Definition and Model-Based Enterprises. Boeing pushed the idea some time ago, even while others in aerospace were pushing digital twin concepts for maintenance and quality data collection.

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NIST Test models help developers and users test Model-Based Definition

The efficiencies in doing so seem massively worth it.

A 2016 study published by NIST [1] demonstrated that for one test cycle, the total time to complete one design annotation, manufacture, and inspection cycle was 60.3 hours with a standard drawing-based cycle compared to 15.2 hours for a model-based cycle. This reduced the time it took to prepare a part for production by 74.8% “when the design to manufacturing and inspection process is converted from drawing-based definitions to model-based definitions.”

I had the opportunity to interview one of the authors of this study, Allison Bernard Feeney, for my December article and the chance to ask her a question that is—or should be—foremost in the mind of any manufacturer contemplating a move to MBD. The December article covers more of the details of how and some of the whys. What is left is when?

So, I posed to Feeney the more detailed question: Are the tools and software available from the manufacturing software community available today ready? Can people at the small and medium enterprises, manufacturers at the tier one, tier two, tier three, implement a Model-Based Enterprise now?

“Absolutely. It’s usable now,” she stated. A key piece of MBD is the product manufacturing information (PMI.) This is the data needed in addition to a CAD model to tell a manufacturing engineer how to create and inspect a part. This includes surface finish specification, material identification, or GD&T. “The PMI is in there.”

Not only is MBD faster, it is more accurate.

To prove her point, she also noted that NIST has done several test pilots. “We did an activity where we took native CAD models and a derivative STEP model and sent them to two different manufacturers. One manufacturer was taking the 3D PDF of the model and building their own model inside their manufacturing system. The other group took the digital technical data package and used that as the source of data,” she explained. “We tracked those two processes and collected metrics. And it turned out that the model was correct but the drawing that was generated from the model had a through hole when it should not have been.”

But, as noted in the December article, adopting it requires careful consideration of culture and being sensitive to existing practices. She recommends going slow, perform a pilot project, do some testing.

“If your dimension and tolerancing schemes are simple, then it will work. The more complex, the more testing you should do to really make sure that you’re getting out of your CAD system what you expect. And if you need to transfer that to another system, that it will be imported correctly. So, companies that are trying to implement MBD really need to start off with a pilot project. They know what their workflows are, information exchange is important to them, and they just have to test it out.”

Eliminating almost 75% of current effort is a powerful motivation.

Feel free to email the author with comments at

[1] For more information see: Testing the Digital Thread in Support of Model-Based Manufacturing and Inspection. Hedberg, et. Al. Journal of Computing and Information Science in Engineering on 08 Mar 2016, ASME available online:


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