June 26, 2011
June 26, 2011
June 29, 2011
Engineering Design Graphics
22.1017.1 - 22.1017.20
Linking CAD and Metrology to Explain, Demonstrate, and Teach Geometric Dimensioning and TolerancingGeometric dimensioning and tolerancing, or GD&T, is a symbolic language that permits designengineers, manufacturing personnel, and quality inspectors to communicate in an efficient andeffective manner. This communication focuses on providing a clear definition of geometricfeatures (e.g., surfaces, holes) and the allowable variation that each feature may contain.Unfortunately, owing in part to its complex rule based system, GD&T is also difficult to teachand learn. To address this difficulty, a technique has been developed that allows students tovisualize geometric tolerances and tolerance zones, and to directly see when a given data point isin or out of tolerance. The technique employs a portable coordinate measuring machine (CMM)interfaced with parametric solid modeling software, a 3D printer, and a granite surface table toaccomplish this.A set of engineering drawings is created, and a 3D printer is used to produce imperfect parts.These imperfections are intended to represent significant manufacturing variation. Then using aportable CMM and the surface table, data points are taken to visually map this manufacturingvariation to a 3D parametric modeling software package. Within this software a perfect part isalso modeled. Once the inspection data is taken, datum features on the perfect part are used toform the boundaries of the geometric tolerance zones. Through this process, studentsinteractively learn the meaning of datum references, as well as how the various tolerances createdifferent zones. Finally, students use the parametric modeling software to measure the inspectiondata points to visually see how in or out of specification a given feature is.Having developed a basic working understanding of GD&T, a second module is used to conveydesign intent through the use of GD&T. Using a simple assembly, students are charged withproviding a fully toleranced drawing for one component of this assembly. Students are given afully dimensioned drawing with basic dimensions and a list of fit, form, and functionalrequirements. From these resources, students must choose a datum scheme, tolerance partfeatures, and explain which requirements drive their decisions. In summary, the goal of theseeducational modules is to illustrate the complex topics of geometric dimensioning andtolerancing through practical application.
Hewerdine, K. P., & Leake, J. M., & Hall, W. B. (2011, June), Linking CAD and Metrology to Explain, Demonstrate, and Teach GD&T Paper presented at 2011 ASEE Annual Conference & Exposition, Vancouver, BC. https://peer.asee.org/18285
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