1996-02-01

CAD Software System Requirements for Concurrent Engineering 960550

Most commercial CAD programs are equipped with a user-interface (such as pull-down window-based menu) and a graphics-based set of geometry creation utilities (to draw line, arcs, surfaces, etc.). They are quite useful for mathematically representing the 3-D geometry in solid format and to draw various 2-D views. Most users find such interactive capabilities convenient to create the geometry when designs are distinct from each other. Though, the interactive process of geometry creation is far better than keying data manually. The process is still quite laborious when multiple studies have to be conducted -- each differing only in a small aspect of the total geometry definition. Most studies are directed towards using some type of analysis or simulation to predict changes in design parameters that drives the resultant design geometry. This process is very similar to design modification, remodeling or design automation. In each case, one is interested in quickly generating a series of input-files for the dependent analysis and using the results of the analysis to drive design modifications. During this modification process, analysis is often used as an integral part of the design. Most CAD/CAM systems fail to capture the needed “design intent” and therefore, cannot easily modify the geometry based on the analysis results. There are a number of ways to capture a “design intent” of a part. The most popular approaches are: parametric, variational geometry, feature-based modeling and knowledge-based engineering. Using such techniques it is possible to regenerate the input-files for a modified part design at a fraction of time. This is compared to the actual analysis time or the time it took initially to create the part interactively. The initial creation of the “design intent” model is the key for reducing the time for subsequent creations of the altered geometry.
In this paper, first a set of requirements for an ideal dimension-driven CAD/CAM system for concurrent engineering is outlined in generic terms. Later an automotive part -- a switching hazard button -- is chosen as an example to illustrate some of the features required for CE. Due to lack of time and resources, the problem is modeled using only a feature-based parametric approach. Pro-engineer was used to create a feature-based parametric model of the part.

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