“Model-based engineering” (MBE) seems to mean different things to different people. But according to CAD validation specialist Doug Cheney of ITI TranscenData in Milford, Ohio, the model-based approach represents the future of product development because machines — not humans — will read the data and validate models. A good model-based approach drives design decisions based on a company’s engineering and business rules. It should significantly slash costs by flagging design errors early on, when they are relatively inexpensive to fix. The main MBE tenet is that data is created once and directly reused by all downstream consumers.
Cheney says high-end OEMs use model-based approaches to reduce the number of drawings, or even do away with them all together. As industry leaders such as Daimler and Boeing lead the way into MBE, they are pushing CAD vendors to fully support 3D annotation, an important attribute of 3D product and manufacturing information (PMI). PMI conveys nongeometric attributes in 3D CAD that are needed for manufacturing. It can include GD&T, surface finish, and material specifications. Cheney also says it’s interesting that midrange packages such as SolidWorks and Solid Edge already support 3D PMI.
MBE means that OEMs and smaller companies no longer have to manually check drawings — but process owners should plan on using the latest tools for automatically checking models. Hand in hand with this technology change, it’s necessary to plan for model defect resolution processes during the CADmodel- creation stage. “Otherwise, a company’s MBE scheme will fall flat on its face,” says Cheney.
So what kind of technical roadblocks do companies face in moving to a model-based enterprise? Cheney say nontechnical issues include limited budgets and the natural human resistance to change. Technical issues include incomplete CAD software functionality, digital data variation, and lagging regulations.
There are several types of digital-data variation. They fall under the headings of “Can it be manufactured?” (i.e., no unrealistic features such as walls with zero thickness); “Is it equivalent?” (i.e., no data loss in migration or translation from CAD A to CAD B); and, “Is it correct and clear?” (i.e., no unintentional or undocumented changes).
To manage variation in model-based enterprises, it is necessary to automate the checking of data to ensure consistent structures, complete content, and realistic features. It is also critical to automate translation validation to eliminate data loss or degradation. Lastly, companies should automate ECO validation so that no unintentional changes get through and all intentional changes are clearly documented.
Cheney adds that STEP is an important part of MBE. Companies can collaborate in a few ways. They can give external suppliers access to their PLM systems. Or, they can publish models in various visualization formats. Another way is to share models through the latest version of STEP, AP242.
According to Cheney, some engineers predicted the death of STEP when visualization formats arose. But STEP has enough intrinsic value and supporters in the government and large aerospace/defense OEMs that it’s still an important part of companies’ strategies, especially for the long-term preservation of their MBE models. The real value of STEP is in preserving models when the authoring systems have disappeared into the wind.