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Session #1338 Virtual CAD Parts to Enhance Learning of Geometric Dimensioning and Tolerancing

Lawrence E. Carlson and Jason C. Trabert

University of Colorado at Boulder / Lockheed Martin Space Systems Company

Introduction

Geometric dimensioning and tolerancing (GD&T) is an important design tool that has gained worldwide acceptance for its ability to accurately control tolerances while allowing maximum manufacturing flexibility to control costs. Many mechanical engineering (ME) departments capitalize on external review boards composed of engineers from relevant industries to provide advice and help guide their programs. At the University of Colorado at Boulder, for example, our Industrial Advisory Committee (IAC) meets semiannually. At a recent IAC meeting, the importance of including GD&T in the ME curriculum was reiterated.

Companies typically send design engineers to intense courses to learn GD&T, often as long as 40 hours, which is approximately as many contact hours as a typical three credit-hour university semester course. Such a course is typically supported by a comprehensive reference text such as Foster.1 On-line GD&T courses are also available.2

A logical place to introduce GD&T is in a first-year design graphics course. However, with the significant amount of other material that must be learned, often overlaid with learning computer- aided design (CAD) software, there is not likely to be room for more than an introduction of the concept of GD&T and a glimpse into its capabilities. While the topic of GD&T is included in a contemporary graphics textbook such as Bertoline,3 it is the last chapter and therefore unlikely to be covered in any detail. Unfortunately, GD&T is dry and dull, particularly when compared to the glamour of CAD.

In this paper, I describe a method for students to gain insight into GD&T by using virtual measurement techniques. In a first-year graphics course, students learn solid modeling using SolidWorks4 CAD software. To understand the meaning of manufacturing variation and how GD&T can monitor and control this variation, we have created several families of parts with intentionally distorted geometry. To illustrate the concepts, tolerances are large and variations are readily apparent. Parts within each family have different amounts of variation from perfect; some are within specification and others are not, mirroring the “real world.”

A student’s task is to “build” CAD fixtures, to measure the variation in each part and compare it to the GD&T specifications. Since each student is assigned a different part to inspect, s/he must

Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition Copyright © 2005, American Society for Engineering Education

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Trabert, J., & Carlson, L. (2005, June), Virtual Cad Parts To Enhance Learning Of Geometric Dimensioning And Tolerancing Paper presented at 2005 Annual Conference, Portland, Oregon. 10.18260/1-2--14839