Dynamic scheduling rule selection for fab operations

In this paper, we exploit the speed of the ordinal optimization (OO)-based simulation tool designed by Hsieh et al (Proc. Int. Symp. Semicond. Manuf., pp. 53-56, 1999) to investigate dynamic selection of scheduling rules a when significant amount of WIP is held back due to engineering causes and when major machine failures occur. Four prominent dispatching rules, FSVCT, FIFO, LDF, and OSA, combined with the workload regulation release policy constitute 256 rule options over a 4-week horizon, where the dispatching rule may change weekly. The rule options are evaluated and ranked by the OO-based simulation tool under the performance index of per layer mean cycle time and throughput rate. Results clearly indicate that dispatching rules should be changed dynamically to handle these unusual events.