Use of model-based definition to support learning of GD&T in a manufacturing engineering curriculum

Abstract

Model-based definition (MBD) has been attracting significant attention in industry as a means for consolidating access to critical engineering information using the CAD model as a portal. One of its goals is to improve engineering efficiency and reduce the time taken to develop a product throughout its design, manufacturing and marketing phases, by integrating engineering annotations with the 3D CAD model. This contrasts with the traditional approach of providing access to this information utilizing a 2D drawing, either in paper or electronic form. Case studies have shown that MBD has the potential to significantly reduce the development time with reductions in cost. At the same time there is resistance to embracing this methodology due to the continued preference for the traditional engineering drawing as a means to communicate nongeometric information on the production floor. As industry pursues greater adoption of MBD, it is also important to consider its use in engineering design and manufacturing curricula to promote better learning of product function, and how this can be captured through the specification of Geometric Dimensioning and Tolerancing (GD&T). As engineering design and graphics instruction has embraced 3D modeling, there is an argument to be made that there is an overemphasis on developing 3D parametric modeling skills. The integration of appropriate engineering annotation such as dimensions and specification of GD&T, which require greater insight into product function than just size and shape, are often relegated to an afterthought when a drawing is generated from the 3D model. This paper presents the experiences and challenges of using MBD technology in an undergraduate manufacturing engineering curriculum for capturing design function and manufacturing requirements through GD&T. It reviews a junior level Design for Manufacture course, where advanced concepts in GD&T are introduced, and where students are required to demonstrate their grasp of these concepts by utilizing MBD. To facilitate this methodology, students receive instruction in the use of CATIA's Functional Tolerancing and Annotation (FTA) workbench which they are required to use in their assignments and project work. In addition to allowing the integration of annotation with the 3D model, the FTA workbench provides a Tolerance Advisor that forces conformance with the ASME Y14.5-2009 standard. This tool guides students in making appropriate choices in their selection of datums, material conditions and geometry depending on the form controls applied. Finally, students are evaluated in their ability to independently apply this knowledge in a senior level Design of Tooling class. This paper will show examples of how learning is accomplished in the junior and senior classes and summarize how the use of MBD is leading to final 3D models and drawings that more fully capture the functional and manufacturing requirements of a design through appropriate use of GD&T.