A Reverse Engineering Design MethodologySpring 1995

Professor Kristin L. Wood Professor Kevin N. Otto

Dept. of Mechanical Engineering Dept. of Mechanical Engineering

The University of Texas at Austin Massachusetts Institute of Technology

A number of descriptive and prescriptive design methodologies have been developed for general engineering design problems, i.e., product design [Pahl 1984, Pugh 1990, Ullman 1992, Ulrich 1994, Asimow 1962]. While these methodologies are applicable to different types of design (adaptive, variant, etc.), they tend to emphasize design problems that seek "original solutions." This emphasis provides a sound foundation for teaching engineering design; it also provides a foundation for establishing corporate design processes in industry. However, for the class of problems known as redesign (adaptive, variant, etc.), an emphasis on original design may be too general as a problem solving approach. Sferro, Bolling, and Crawford argue the legitimacy of this claim, based on an analysis of the current variant design processes in the automobile industry [Sferro 1993]. They develop a new variant design methodology, referred to as Direct Engineering, to replace more general original design methods.As with original design, redesign problems include the process steps of "specification planning and development", "concept generation", and "product embodiment", but they also focus on an additional step, referred to here as "reverse engineering". Reverse engineering initiates the redesign process, wherein a product is observed, disassembled, analyzed, tested, "experienced," and documented in terms of its functionality, form, physical principles, manufacturability, and assemblability. The intent of this process step is to fully understand and represent the current instantiation of a product. Based on the resulting representation and understanding, a product may be evolved, either at the subsystem (adaptive), configuration (adaptive), component (variant), or parametric (variant) level.In this short document, a preliminary reverse-engineering design methodology is presented, motivated and influenced by the work of Sheppard and Tsai [Sheppard 1992] and Brereton and Leifer [Brereton 1993]. This methodology focuses on the process steps needed to understand and represent a current product. Contemporary techniques in engineering design are utilized at each stage in the reverse-engineering design process to meet this goal. The techniques, viewed singularly, are no different than the techniques used in other design methodologies. However, their specific use for product representation provides a novel context for application.Given these introductory comments, a ten-step reverse-engineering design methodology is presented below. A brief textual description of each process step is provided, in addition to recommended design techniques per step. A redesign example problem is also used to illustrate each process step, including expected graphical results. The specific example problem for this document is a caliper disk brake subsystem for an automobile. Figure 1 shows a schematic of a disc brake subsystem. Figure 2 provides a complete view of a automobile brake system, with human force input and frictional force output between the disc and the automobile wheels.