Issues in the design of the reconfigurable fixture modules for robotic assembly

Abstract

Abstract Workpiece positioning and constraining is an important factor in manufacturing processes such as machining, welding, bonding, and assembly. Jigs and fixtures are devices employed to position and constrain the workpiece in a desired location to ensure that it is in a state of static equilibrium and that dimensional accuracy is maintained during the manufacturing operation. Traditionally, fixtures have been designed and manufactured as single-purpose devices for specific parts and manufacturing operations. The traditional approach is costly due to the long load time and effort required to design and manufacture special-purpose fixtures, manual set-up and change of fixtures, and overhead cost associated with storing and retrieving a multiplicity of fixtures. Thus, the traditional approach is not suited to the flexible manufacturing environment where production volume is low and product variation is high. If flexible manufacturing systems (FMSs) are to be truly flexible, then the fixturing must also be flexible. This paper presents requirements, design principles, design rules, and a prototype system for flexible fixtures in robotic assembly. Such a fixturing system would employ a number of fixture modules that are set-up, adjusted and changed automatically by the assembly robot without human intervention. The design of the fixture layout is performed interactively on a commercially available computer-aided design (CAD) package. The guidelines for development of a dedicated software program to automatically generate robot program for setting up, adjusting, and dismantling the fixture, using the information retrieved from the CAD database, is presented.