Document Type: Research Paper
School of Engineering, Urmia University, Oroumieh, West Azerbaijan Province, Oroumieh, Iran
Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran
Technical and Vocational University, Tehran, Tehran Province, Iran
In this paper, we study the re-entrant no-wait flexible flowshop scheduling problem with makespan minimization objective and then consider two parallel machines for each stage. The main characteristic of a re-entrant environment is that at least one job is likely to visit certain stages more than once during the process. The no-wait property describes a situation in which every job has its own processing sequence with the constraint that no waiting time is allowed among operations within any jobs. This study develops a bottleneck-based heuristic (BBFFL) to solve a flexible flowshop problem including a bottleneck stage. Also, a genetic algorithm (GA) based on heuristics for the problem is presented. First, the mathematical model for the problem is proposed, and then the suggested algorithms are explained. For small-scale, the results of the BBFFL and GA are compared to the results derived from the GAMS. For large-scale problems, the results of the GA and BBFFL are compared with each other. For small-scale problems, the algorithms have a close performance but the BBFFL is likely to generate much better in finding solutions in large-scale problems.