Hybrid Flowshop Scheduling with Setups to Minimize Makespan of Rubber Coating Line for a Cable Manufacturer

Abstract

We consider the hybrid flowshop scheduling problem of a cable manufacturing company. We focus on rubber coating line to minimize the makespan. Industrial cables differ based on the number of cores and core colors. The rubber coating line is composed of three stages with two identical parallel machines in each stage. These stages are i) Isolation; ii) Bunching; iii) Sheathing. The input of the isolation stage is copper wire whereas the output of the isolation stage is cores with different colors. Before the isolation stage, a sequence-dependent setup time is required based on a cross-section of cables and a sequence-independent setup time is required to change the color of cores. The input of the bunching stage is cores with different colors whereas the output of the bunching stage is bunched cores. Before the bunching stage, a sequence-independent setup time is necessary based on the number of cores. The input of the sheathing stage is bunched cores whereas the output of the sheathing stage is rubber-coated cables. Before the sheathing stage, a sequence-dependent setup time is needed based on area. Since the problem is NP-hard, genetic algorithm is employed. With the help of genetic algorithm, we can determine the best job-machine assignments for each stage, the best job sequence on each machine at each stage, start and completion times of jobs on each stage, and the best makespan.