Case-based reasoning in fixture design

Fixtures are designed to accurately locate and secure a part during machining operations such that the part can be manufactured to design specifications. To reduce the design costs associated with fixturing, various computer-aided fixture design (CAFD) methods have been developed through the years to assist the fixture designer. One approach is to use a case-based reasoning (CBR) approach where relevant design experience is retrieved from a design library, and adapted to provide a new fixture design solution. Indexing design cases is a critical issue in any CBR approach, and CBR systems can suffer from an inability to distinguish between cases if indexing is inadequate. This paper presents a CAFD methodology that adopts a rigorous approach to defining the indexing attributes in which Axiomatic Design "Functional Requirement" decomposition is adopted. Thus, a design requirement is decomposed in terms of functional requirements, physical solutions are retrieved and adapted for each individual requirement, and the design is then reconstituted to form a complete fixture design. Furthermore, adaptability is used as the basis by which designs are retrieved in place of the normal attribute similarity approach, which can sometimes return a case that is difficult or impossible to fix.