Ergonomic work rotation scheduling to balance the workload of employees in assembly lines

Human labor plays an important role in production and its evaluation is the subject of many studies. Assembly lines in mass production often consist of a large number of repetitive manual tasks, and the workload of workers in these systems is high. Due to the repetitive manual tasks and the prolonged movements during the working day, biomechanical overload of workers' limbs occurs and workers are at risk of musculoskeletal disorders. For this reason, it is crucial to balance the workload between the operators by considering the ergonomic elements on the assembly lines. In this study, the REBA method, one of the ergonomic risk assessment methods, was used to evaluate the risks arising from all posture positions of the operators, and a multi-criteria job rotation scheduling model was developed that takes into account the abilities and preferences of the operators. The proposed model aims to increase the motivation of the employees, balance the work in terms of workload and processing times, ensuring that the work is completed in the shortest time and that appropriate operators are assigned to the tasks on the assembly line. In the model developed differently from the literature, it is aimed to minimize the difference between the REBA scores of the operators, to make the assignments according to the preferences of the operators and to provide the balance between the processing times. The work carried out is a real-world application and was conducted in an automotive company operating in Ankara. Since the results of the proposed mathematical model provide long-term solutions, results can be obtained for a certain number of tasks. The results of the developed multi-criteria mathematical model and the Simulated Annealing heuristic were compared using different performance measures.