ACO-ICSA based scheduling of re-entrant manufacturing system with Mix-processing Style

Semiconductor wafer fabrication facility (fab) is a typical re-entrant manufacturing system. It is characterized with reentrant process flows, mix processing models, large-scale and unbalanced production facilities. A hybrid method (ACO-ICSA), combining an ant colony optimization (ACO) with immune clone selection algorithm (ICSA), is proposed to solve its fab-wide scheduling problem. Its main idea is to find a scheduling solution for each bottleneck with batch or non-batch processing style by using an ACO or ICSA first, then re-unify these solutions to multiple scheduling plans for these bottlenecks satisfying precedence constraints, and finally obtain the scheduling plans of non-bottlenecks subject to those of bottlenecks and precedence constraints. These fab-wide scheduling plans are translated into the pheromone or affinity to guide artificial ants or antibodies to implement their new search processes. The Mini-fab model and an electrical equipment production line are used to verify and validate the proposed method. The simulation results show that ACO-ICSA improves the operational performance with better total weighted tardiness and makespan.