Optimizing dual resource constrained flexible job shop scheduling: managing fatigue and scheduling efficiency through break time

The dual resource constrained flexible job shop problem (DRCFJSP) optimizes operation assignments to machines and workers by incorporating human factors, aligning with Industry 5.0’s emphasis on human-centered and sustainable production. Although recent DRCFJSP models consider worker fatigue, workload, and other human factors, the explicit use of break time as a scheduling decision for worker recovery has received limited attention. This study develops a MILP-based DRCFJSP model that determines whether and when workers should take breaks according to fatigue and recovery conditions, while incorporating worker competence into the fatigue–recovery formulation to minimize makespan. The model is validated using Gurobi on real-world data from a metal manufacturing environment and benchmarked against a GA-based metaheuristic. The results show that incorporating break times reduces the makespan by up to 18.8%. In the industrial case study, break-time scheduling reduces the makespan by 2.8% and increases worker productivity by 16.96%.