Makespan Minimization in a Flowshop Sequence Dependent Group Scheduling and Worker Assignment Problem

The aim of this paper is to propose a mathematical model and to develop an optimization procedure to find efficient solutions to the joint flow shop group scheduling and workers assignment problem. In the investigated manufacturing system, the jobs are grouped into families and should visit machines in the same order., The group set-up times are sequence dependent. In order to evaluate the real scheduling conditions, the influence of workers is modeled, too. In particular, the operator skill influences the set-up time length. Conversely, the processing time of each job is modeled as independent from the selected worker because the working operations are considered as automated. A proper genetic algorithm has been designed and tested for the problem by running a benchmark of process scenarios having different numbers of machines, groups, jobs, worker skills and learning ability.