A dispatching scheme involving move control and weighted due date for wafer foundries

Increasing automation of wafer foundries in Taiwan has heightened the demand to automate dispatching decisions in recent years. To attain a better global performance, dispatching decisions should be made based on critical shop floor information. In this study, we present a dispatching scheme which combines move control and weighted due date concepts, genetic algorithm (GA) and simulation. The move control and weighted due date concept is applied to identify important dispatching decision factors respecting performance indices of due-date satisfaction and throughput. The GA is employed to derive proper weights for those decision factors. A simulation procedure capable of simultaneously considering product mix, reentrant process, and the influence of random events on the shop floor is developed to evaluate the system performance based on the derived weights of decision factors. A case study involving a simplified and revised data set from a Taiwanese wafer foundry is presented. Results show that the dispatching scheme proposed in this paper is effective and outperforms six conventional dispatching rules (FIFO, SPT, SRPT, EDD, SLACK, and CR) on performance measures of due date satisfaction, throughput, WIP level, critical machine utilization, and mean cycle time under both CONWIP and uniform release policies.