DETERMINING TRANSFER BATCH SIZES IN TRIP-BASED MATERIAL HANDLING SYSTEMS

Trip-based material handling systems such as AGV systems or lift truck s are often designed with a given How matrix (or from-to chart), which typically shows the number of loaded trips that the devices must perf orm per unit time between the workstations. A from-to chart that would result from the parts flow in a facility actually is dictated by the transfer batch size; that is, the number of parts transferred from one workstation to the next in one trip. In this paper. we present analyt ical and simulation results aimed at determining optimal or near-optim al transfer batch sizes in manufacturing systems and develop an analyt ical relationship between the material handling capacity and the expec ted work in process (WIP) in a manufacturing system. Although the resu lts apply to any discrete-parts How, trip-baled material handling syst em, they are particularly relevant for the electronics manufacturing i ndustry, where parts (such as printed circuit boards or substrates for Hat panel displays) typically are handled as a group (in specially de signed containers such as cassettes) and the costs associated with WIP tend to be large. In such applications, the cassette size is the tran sfer batch size.