What Is Model-Based Definition?

Ryan Reid | Comments | January 28, 2016

MBD

Model-based definition, or MBD, lets you place the dimensions and notes right on the 3D model.

Tradition is not always bad, but if it gets in the way of truth, it’s time to reconsider. Traditional drafting practices have us creating 2D views of 3D models. On these 2D views, tradition would have us place all dimensions. But if you think of the 3D model as the source, the single truth, then 2D views of it are only interpretations. One mistake, or misinterpretation, and we have a problem.

So why did we ever start putting dimensions on 2D views in the first place? We had no choice when we only had paper. Everything had to get flattened into 2D views so it could be put on paper. But now, just about all our designs are in 3D.

Is it time to reconsider tradition and put the dimensions right on the 3D model itself?

What’s Behind the Buzzwords?

First, let’s get the acronyms out of the way. MBD stands for model-based definition. MBD is very similar to, or a synonym for, PIM, or product information modeling. GD&T is geometric dimensioning and tolerancing. It’s a different way of dimensioning parts in either 2D or 3D. It dimensions features and geometry instead of lines. There are other definitions of it, but I won’t get into that now.

MBD

MBD is the practice of placing either traditional or GD&T dimensions on the 3D model itself during the design process. The engineer or designer can place these dimensions on the model for a variety of uses.

Following is a brief overview of why MBD would be used.

  • Go paperless!

By putting all of the dimensions on the model itself, there is arguably no need for 2D representations of the design. No drafting department, no plotters, no interpretations of 2D views—so no ambiguity. Consider that a 2D representation is an interpretation of the model. Any time you add an interpretation, you are opening the door for quality-assurance problems.

 
GD&T

This image demonstrates how GD&T is placed on the model. All of the saved views that can be exported to a variety of mobile-capable formats, including eDrawings, PDFs, and 3D PDFs, appear below the model.

  • Saving on paper often easily justifies the cost of electronic equipment out on the shop floor. Especially since the cost of electronic “glass” at each station has dropped so dramatically over the past few years. Stations can be as low as $100.
  • Revision control is greatly simplified. When a shop worker looks up a drawing, or component instructions, he or she and manufacturing are completely assured
  • that they have the correct revision and that it is controlled by whatever product data management (PDM) system the company is using. There is little or no chance of a stray previous revision drawing out on the shop floor that would cause a large costly error. MBD supports this documentation that is intended for interactive consumption much quicker than traditional 2D representations.
  • Component instructions can be much more feature-rich. Tools such as SOLIDWORKS Composer and other CAD animation programs can provide much more interactive and better-communicated instructions to the end user.
  • The labor involved in maintaining a paper-centric environment is a substantially overlooked cost of manufacturing. Maintaining packets and failing to maintain packets can be very expensive.
  • Tolerance analysis, here we come!
    • Tolerance analysis is the practice of fully understanding all of the critical dimensions and their tolerances. To fully understand those dimensions, the designer needs to roll up every dimension into the highest assembly. This can be a very time-consuming operation if done by hand or even on spreadsheets. MBD, specifically SOLIDWORKS MBD (greatly improved in its newest release) and TolAnalyst, allows for that process to be automated and for the results to be shown graphically while designing in CAD. This allows designers to quickly ensure that all of the dimensions and tolerances make a functional design.
  • Don’t go paperless! But still use MBD!
    • By having the designer designate the critical dimensions, weld callouts and notes in the model prior to passing the design on to the drafter, there is a large reduction in back-and-forth between the designer and the drafter. The drafter can have all of the information they need as soon as it is ready. This creates a more efficient drafting process and allows a designer to focus on more design work. This alone can be a huge benefit to a company that must innovate and release products quickly—and who isn’t trying to do that?

So, there are the benefits of MBD. A file still needs to be created for consumption by the end users. I can’t just give the shop floor my CAD files. That would require near-workstation-class machines for

every user. Luckily, SOLIDWORKS MBD has some great options for this.

PDFs and 3D PDFs

  • MBD information is translated over to communicate to the end user.
  • After creating my model, I can export multiple 2D PDFs for each view, or a consolidated version of all of those views.
  • I can also export 3D PDFs, which include a full 3D representation of the model with all of the dimensions that I choose. SOLIDWORKS MBD 2016 supports multiple sheets, multiple viewports and multiple tables in 3D PDF publishing.
  • I can also do both. The 3D PDF can contain all of the views that I require, and the model itself.
  • SOLIDWORKS MBD has a very thorough set of capabilities for PDFs. It arguably has the largest set of options for PDFs.
  • These PDFs can have markup and measurement tools in them to support reference information and change processes.
  • Both 2D and 3D PDFs can be viewed on nearly any type of device (iOS, Android, Windows), making it the most flexible and lightweight format.

finalized_PDF

An example of a finalized PDF file.

eDrawings

  • MBD information is translated over to communicate to the end user.
  • eDrawings is a SOLIDWORKS-specific file format that can be published from SOLIDWORKS. It contains a more feature-rich toolset that includes more advanced BOMs, section views and markup and model manipulation tools.
  • eDrawings is also supported by all three major operating systems as an app.
  • eDrawings supports augmented reality, which means that if I print out a QR code and lay it on a table, I can use the camera on the device with eDrawings and eDrawings will superimpose a 3D model in the camera view. I can rotate the camera around and see all sides of it to scale. I can also manually rotate and scale the model as I choose.
  • eDrawings also supports a more advance configuration control of models from SOLIDWORKS.

Last but not least, SOLIDWORKS Composer

  • MBD-generated files can be linked into SOLIDWORKS Composer files for fully-comprehensive final documentation for the end user.
  • SOLIDWORKS Composer can give interactive step-by-step instructions of the assembly or fabrication of the design.
  • This can be saved as an HTML file to be used in most browsers.

A Composer file can be played back on a player, which can have limitations with operating systems. See your CAD vendor for details.

Great! Now you can see that there are many options to help you start saving your company money and start making your design process simpler while giving you more time to get new designs done.

soldiworks_mbd

The varied capabilities of SOLIDWORKS MBD in their relative packages.

Setting up and changing a company’s culture and process to support this relatively new technology is no easy task. I suggest you call or e-mail a SOLIDWORKS vendor to better understand how to take advantage of this technology for your company, and have them help you set it up. I believe that this technology can and will solve many of the problems that plague small- and large-size companies. With proper guidance and support, I believe that every company can solve these problems in a relatively small amount of time. You will be able to innovate faster with better quality and less waste than your competitor. And isn’t that what manufacturing is mostly about?


About the Author

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Ryan Reid is a CAD administrator, PLM enthusiast, designer, GD&T specialist, lead, lean philosophy supporter, Microsoft Office expert, 3D printing hobbyist and manufacturing-focused professional with 17 years of combined experience in those areas. Reid has accomplishments in all aspects of manufacturing engineering, from cradle to grave plastics/mold to structural, systems, process and change management design.

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