Genetic algorithms for a single-machine multiple orders per job scheduling problem with a common due date

In this paper, we discuss a multiple orders per job (MOJ) scheduling problem. Front opening unified pods (FOUPs) transfer wafers in 300-mm wafer fabs. Several orders can be grouped in one FOUP which can be considered as a job. A lot processing environment is assumed. All the orders have an unrestrictively late common due date. The earliness and tardiness of the orders is minimized. Since the problem is NP-hard, we propose two hybridized genetic algorithms. Computational experiments on randomly generated problem instances are carried out that demonstrate that the genetic algorithms perform well.