Fixture-Based Design Similarity Measures for Variant Fixture Planning

Title of Thesis: FIXTURE-BASED DESIGN SIMILARITY MEASURES FOR VARIANT FIXTURE PLANNING Degree candidate: Sundar Balasubramanian Degree and year: Master of Science, 1999 Thesis directed by: Dr. Jeffrey W. Herrmann Department of Mechanical Engineering and Institute for Systems Research One of the important activities in process planning is the design of fixtures to position, locate and secure the workpiece during operations such as machining, assembly and inspection. The proposed approach for variant fixture planning is an essential part of a hybrid process planning methodology. The aim is to retrieve, for a new product design, a useful fixture from a given set of existing designs and their fixtures. Thus, the variant approach exploits this existing knowledge. However, since calculating each fixture’s feasibility and then determining the necessary modifications for infeasible fixtures would require too much effort, the approach searches quickly for the most promising fixtures based on a surrogate design similarity measure. Then, it evaluates the definitive usefulness metric for those promising fixtures and identifies the best one for the new design. This thesis explores the use of a design similarity measure to find existing designs that are likely to have useful fixtures. The approach aims to identify design attributes that reflect the underlying fixture usefulness. Then, it formulates a consistent design similarity measure that maps the design attributes of a new design and an existing design to the usefulness of the fixture associated with the existing design for the new product design. The correlation between the design similarity and fixture usefulness enables definition of a fixture-based design similarity measure. This approach has been developed for a class of part designs and modular fixtures. It will enable a manufacturing firm to reuse dedicated fixtures by identifying an existing fixture that requires only a minor change to become an effective fixture for a new design. This will reduce the amount of time spent constructing fixtures. In addition, the variant procedure requires less computational effort than a generative procedure. It is economical to have design families based on fixtures, so that a new design can be assigned to any of these families and changeover times can be reduced. Reusing both fixtures and fixturing solutions has far-reaching implications in terms of cost and lead times. FIXTURE-BASED DESIGN SIMILARITY MEASURES FOR VARIANT FIXTURE PLANNING by Sundar Balasubramanian Thesis submitted to the Faculty of the Graduate School of the University of Maryland at College Park in partial fulfillment of the requirements for the degree of Master of Science 1999 Advisory Committee: Dr. Jeffrey W. Herrmann, Chair/Advisor Dr. Satyandra K. Gupta Dr. Yu Wang