Model Based Definition (MBD) The ABCs of MBD

All product data lives in the 3D CAD model

Model based definition (MBD) is a process which culminates in a 3D CAD model that is the complete product definition.

Mechanical product design traditionally relied on 2D drawings to communicate product information. This system served engineers but burdened others in the enterprise with the task of recreating data in their own systems. The result? Human error, when combined with incorrect or misinterpreted 2D drawings, too often led to scrapped parts, product failures, or great frustration.

In contrast, model based Definition (MBD) means everyone – from the engineer to the packaging designer – has what they need. MBD allows 3D CAD data with embedded product manufacturing information (PMI) in the form of 3D annotations to be used by anyone who needs access to the complete product definition.


The authoring part of the MBD process has three major steps:

  • Adding 3D annotations such as dimensions, geometric tolerances, datum symbols, datum targets, surface finish, notes, and weld symbols to the model.
  • Organizing these annotations, making them easy to find and read.
  • Publishing the native CAD model into a derivative 3D format that accurately represents the geometry and preserves the integrity of the 3D annotations.

The engineering department then hands this 3D format to the downstream functions, who can use a simple viewing tool to view it with the confidence that it captures the full product definition of the native CAD model.

Correct geometric dimensioning and tolerancing (GD&T) is the final phase of MBD.

GD&T is painstaking manual work, as anyone knows who has spent more time detailing a model than designing it. Worse, the very nature of this complex process means it is prone to error. With our partners at Sigmetrix, we’ve developed the Creo GD&T Advisor Extension to resolve these issues and put your focus back to where it should be – on your design.

Download the Creo GD&T Advisor Extension Datasheet

Learn more about how companies are using PTC's suite of CAD software products to their best advantage.

KTM (motorsports)
College Park (prosthetics)
University of Tokyo (artificial heart)
Aston Martin
Aristides Guitars

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