Performance comparison of assembly systems with fixed and flexible cycle times

The traditional assembly system consists of a series of balanced workstations operating at the same rate with fixed cycle times. Recent advances in technology allow more flexible assembly systems, in which workstations operate independently and cycle times vary from job to job. This article develops an anlytical model for comparing the throughputs (jobs per hour) of assembly systems with fixed and variable cycles times. The throughputs are compared on a common basis by requiring that both systems allow sufficient processing time to ensure product quality and that they have the same total times in system per job. Results indicate that an assembly system with variable cycle time can operate at a significantly higher throughput than one with fixed cycle times, provided there is sufficient buffer storage space between workstations to accommodate queueing. This benefit must be weighed against possible increased capital investment and practical considerations associated with system control.