Testing Implementations of Geometric Dimensioning and Tolerancing in CAD Software

Applying geometric and dimensional tolerances (GD&T) to part features in computer-aided design (CAD) software is essential so that the part will function properly and to guide downstream manufacturing and inspection processes. However, it is not well characterized how CAD software implements capabilities for a designer to apply GD&T to a part. Of course, CAD software vendors do their own internal testing of those capabilities and users evaluate CAD software so that it satisfies their CAD modeling requirements. However, there has never been any rigorous public-domain testing of CAD software GD&T implementations. To improve that situation, the National Institute of Standards and Technology (NIST) has developed a system to test implementations of GD&T in CAD software. Representative part geometry with GD&T applied to features was modeled in four of the major CAD systems. Errors with semantic representation and graphical presentation of the GD&T were collected and analyzed. The testing methodology, test results, and data analysis demonstrate how well the CAD system GD&T implementations perform. The testing project results can be used as a basis for future testing, methods, and standards to evaluate defects in GD&T applied to part features.