Consideration of processing time dissimilarity in batch-cyclic scheduling of flowshop cells

Flowshop scheduling methods that appear in the literature assume that products are processed in either batch mode or cyclic mode. In batch mode, a product starts after another product is completely processed. On the other hand, in cyclic mode, products are run in mixed mode with unit transfer. In this paper, a new scheduling method, the batch-cyclic scheduling method, is proposed to schedule the products. In the proposed method, multiple sets of products (Cyclic Sets) are selected first and then products in each cyclic set are run in mixed mode. Overall, the general solution approach consists of three phases: (1) family formation based on processing similarity; (2) subfamily formulation based on a processing time dissimilarity (proposed mathematical model); (3) product scheduling using the batch-cyclic method (proposed mathematical model). As in the cyclic method, batch-cyclic scheduling is feasible when setup times are negligible. Due to the lack of work in this newly proposed batch-cyclic method, it is compared with the batch method. Additionally, the performance of the three-phase approach is compared with the two-phase approach using 27 scenarios. The results show that the proposed three-phase approach minimises the number of machines and lowers makespan when the bottleneck machine shifts.