Dispatching rules for a two-stage hybrid flow shop scheduling with no inter-stage waiting time

This computational study investigates a production scheduling problem for a two-stage hybrid flow shop (HFS) with parallel machines at least at one stage and with zero inter-stage waiting policies between process steps. This scenario is important in industries such as steel production and chemical processing, where cooling time between process steps must be avoided. In this paper, we propose eight dispatching rules that are applied to instances of up to 200 jobs, and benchmark them based on various performance metrics that demonstrate the effectiveness of the proposed heuristic approaches. The dispatching rules, such as Shortest Task Time (STT) and Shortest Processing Time (SPT) are combined with machine assignment rules, such as First Available Machine (FAM) and Minimum Idle Time (MIT), and optimized for makespan and total completion time in the no-wait HFS. Furthermore, for our computational study, we investigate two sequencing approaches - stage-oriented decomposition (A1) and reduction to a flow shop problem (A2) - in the benchmark of this computational study.