June 14, 2009
June 14, 2009
June 17, 2009
Engineering Design Graphics
14.421.1 - 14.421.11
Introduction Today’s engineering students will enter a work environment where the use of computer-aided design tools is ubiquitous. CAD tools are used throughout the design process 1. CAD tools are also used to facilitate global development projects with engineers located around the world all working on the same project 2. When used in concert with product lifecycle management systems; a complete library of CAD models can be accessed by engineers around the world 3. These trends increase the importance of designing in a manner that is both intuitively organized and amenable to change.
The design intent of a model should capture its function and allow the model to be easily altered 4-6 . Design intent is at the core of the CAD modeling process, encompassing feature* selection, order, and organization 4. To produce models that are amenable to change and use modern CAD tools to their full potential, the focus of CAD courses should be around how to convey design intent. Unfortunately, most CAD modeling instruction is focused on teaching declarative knowledge – the key strokes and button picks required to perform certain tasks in specific software platforms 7-8. Design intent would fall under the category of strategic knowledge 9. This type of knowledge can transcend a particular CAD program or version 10. It is important that students learn knowledge that is easily transferable, given the number of CAD programs available and the rate at which they update. Rynne et al, cite attributes such as: proper location and orientation of the base feature, use of symmetry, simple and well defined sketches, correct feature termination, and correct duplication methods as promoting proper design intent 11.
The importance of design intent is difficult to convey without some type of alteration to an existing model. Unfortunately, in most CAD courses students design components that are never altered, or in some cases only altered by the original designer. This is the case even though such exercises are viewed as beneficial in teaching students how to design 12. To demonstrate the importance of design intent to students, a model alteration exercise is presented in the next section. The results of the exercise from one semester are presented in the following section.
Background and Exercise Description The exercise described in this paper was prepared for a junior-level design course in a mechanical and manufacturing engineering technology program. CAD is taught as the laboratory portion of the course. The laboratory is one hour and fifty minutes long. The software used in the course is Pro/Engineer Wildfire 3.0. Most students had some experience with a CAD program previously (e.g., AutoCAD or SolidWorks). Very few students had experience with the Pro/Engineer software package (which the course uses). The laboratory is focused on creating models that are easy to alter and showing the effects of alterations when modeling using different methods. The exercise was carried out near the end of the semester after the students had been instructed in basic and intermediate part modeling. * Features are the building blocks of parametric CAD models. Depending on the software, they include basic elements (e.g., blocks, bosses, pockets, or holes) or sketch manipulations (e.g., extrusions, revolves, or blends).
Johnson, M. (2009, June), Design Under Alternative Incentives: Teaching Students The Importance Of Feature Selection And Organization In Cad Paper presented at 2009 Annual Conference & Exposition, Austin, Texas. https://peer.asee.org/4525
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