Job-shop scheduling problem with sequence dependent setup times

The majority of researches on scheduling assume setup times negligible or as a part of the processing time. In this paper, job shop scheduling with sequence dependent setup times is considered. After defining the problem, a mathematical model is developed. Implementing the mathematical model in large problems presents a weak performance to find the optimum results in reasonable computational times. Although the proposed mathematical model presents a good performance to obtain feasible solutions, it is unable to reach the optimum results in larger problems. Thus, a heuristic model based on priority rules is developed. Because of the inability to find optimum solutions in reasonable computational times, 3 different innovative lower bounds are developed, which could be implemented to evaluate different heuristics and metaheuristics in large problems. The performance of the heuristic model evaluated with a well-known example in the literature insures that the model seems to have a strong ability to solve jobshop scheduling with sequence dependent setup times problems and to obtain good solutions in reasonable computational times.