chapter  9
49 Pages

Fixturing Accuracy Analysis and Verification

Manufacturing accuracy depends on relative positions of the machining tool and the workpiece (Rong and Wu, 1988). Fixtures are used to locate and hold a workpiece in proper position during machining processes. The de­ velopment of computer-aided fixture-design (CAFD) systems is becoming increasingly important within flexible manufacturing systems (FMS) and computer-integrated manufacturing systems (CIMS) (Thompson and Gandhi, 1986). Basically, two major approaches exist in CAFD. The first one is the rule-based (or knowledge-based) automated fixture design where geometric reasoning, kinematics analysis, or screw theory may be applied (Pham and de Sam Lazaro, 1990; Trappey and Liu, 1990a; Chou et al., 1989). The second is group technology (GT)-based search and retrieval of existing fix­ ture designs (Grippo et al., 1987; Rong and Zhu, 1992). The former is ideal for total automation but usually can only be applied to simple workpiece geometry because of the difficulties in geometric modeling and rule extrac­ tion. The latter is practical for industrial applications due to the use of ex­ isting knowledge in fixture designs.