Flexible flow line scheduling problems with re-entrant flows and queue-time constraints

We consider scheduling problems in a flexible flow line (FFL) with re-entrant flows and queue time constraints. The objective of the scheduling problem is to minimize the number of tardy jobs. The problem considered in the study is a NP-hard problem in the strong sense. Since much computation time is required to find the optimal solution, heuristics are an acceptable practice for finding good solutions. In this research, rule-based heuristics are proposed to solve FFL problems with re-entrant flows and queue time constraints. To evaluate the performance of the proposed heuristics, a large number of test scenarios are designed to simulate practical shop floor problems. For these candidate problems, computational experiments are performed to compare the performance of the proposed heuristics against several well-known dispatching rules. The results show that the proposed heuristics outperform other heuristics.