Sensitivity Analysis of the Unrelated Parallel Machine Scheduling Problem with Rework Processes and Machine Eligibility Restrictions

This paper deals with an unrelated parallel machine scheduling problem considering machine eligibility restrictions and release times. Setup times are both operation sequence and machine dependent, and defective items are possible to occur. In order to retrieve imperfect items and to improve them to meet an acceptance level of quality, rework processes are considered. A developed optimization model is used to minimize the makespan. Since the considered system involves several parameters, to understand how changes in parameters may affect the output of the model and to address the types of questions arise from parameter variations, it is necessary to perform sensitivity analysis. It is a hard task to track the effect of all parameters and their interactions. Therefore, this paper focuses on parameters which are recognized the most appropriate to perform sensitivity analysis. Hence, several scenarios and cases including some test problems are designed and the computational results are analyzed.