Joint optimization of a flow-shop group scheduling with sequence dependent set-up times and skilled workforce assignment

Flow-shop sequence-dependent group scheduling (FSDGS) problem has been extensively investigated in the literaturealso due to many manufacturers who implemented the concept of group technology to reduce set-up costs, lead times,work-in-process inventory costs, and material handling costs. On the other hand, skilled workforce assignment (SWA) tomachines of a given shop floor may represent a key issue for enhancing the performance of a manufacturing system. Asthe body of literature addressing the group scheduling problems ignored up to now the effect of human factor on theperformance of serial manufacturing systems, the present paper moves in that direction. In particular, an M-machineflow-shop group scheduling problem with sequence-dependent set-up times integrated with the worker allocation issuehas been studied with reference to the makespan minimization objective. First, a Mixed Integer Linear Programmingmodel of the proposed problem is reported. Then, a well-known benchmark arisen from the literature is adopted to carryout an extensive comparison campaign among three properly developed metaheuristics based on a genetic algorithmframework. Once the best procedure among those tested is selected, it is compared with an effective optimizationprocedure recently proposed in the field of FSDGS problems, being this latter properly adapted to run the SWA issue.Finally, a further analysis dealing with the trade-off between manpower cost and makespan improvement is proposed.