Recent Research on Computer-Aided Fixture Planning

Abstract

Fixtures are used to locate, hold and support workpieces in manufacturing operations such as machining, inspection, and assembly. Designing and fabricating fixtures can take up to 10-20% of the total cost of a manufacturing system. Fixture planning is a complex activity restricted by the extreme diversity of workpiece, product batch size, product geometry, part accessibility, and working force. Computer-Aided Fixture Planning (CAFP) has been used to improve the fixture design for over 20 years. CAFP contributes to the reduction of lead-time and human interaction in fixture planning. It helps verification of the fixture quality and integration of fixture design with CAD/CAM systems. This paper summarizes constraints of fixture planning and four phases of CAFP. Various approaches to CAFP are surveyed. Application systems of CAFP including some recent patents are reviewed. The paper concludes with the research trend of CAFP. The global competition and customer demand change lead to greater product variety, smaller product batch size, shorter production time and higher product quality. Industrial organizations have to pursue flexibility and automation in manufacturing systems to remain competitive and profitable. Flexible Manufacturing System (FMS) developed in the past decades is to meet such challenge. FMS usually consists of one or more CNC machines which are capable of machining a variety of workpieces. With the development of Computer- Aided Design and Computer-Aided Manufacturing (CAD/ CAM) technology, product design and machining program- ming have been greatly computerized. However, one of the difficulties in FMS is the fixture design for locating and securing a workpiece during manufacturing operations. Fixture planning is time-consuming as it is customized for workpieces. Computer-aided fixture planning (CAFP) aims to reduce the lead-time and human interaction in fixture planning. It can verify fixture quality to integrate fixture design with CAD/CAM systems by automating the reasoning process. The integration of CAFP with CAD/CAM has greatly reduced the production lead-time and cost for an overall optimal solution in product design and manufacturing (1). Fixtures are used to locate, hold and support workpieces in manufacturing operations such as machining, inspection, and assembly. Fixture design and manufacturing is costly due to the tight tolerance and restricted machining opera- tions. Designing and fabricating fixtures can take up to 10- 20% of the total cost of a manufacturing system. Dedicated fixtures are mostly applied in mass production to gain high efficiency. For smaller batch size, the fixture flexibility becomes more important than efficiency due to the workpiece variety and machining requirements. Flexible and