Browsing by Author "Duman, Mehmet"

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Citation Count: Cetinkaya, Ferda C.; Duman, Mehmet, "Lot streaming in a two-machine mixed shop" International Journal of Advanced Manufacturing Technology, Vol. 49, No. 9-12, pp. 1161-1173,(2010)
Lot Streaming In A Two-Machine Mixed Shop
(Springer London LTD, 2010) Çetinkaya, Ferda Can; Duman, Mehmet; 50129
Most classical scheduling models overlook the fact that products are often produced in job lots and assume that job lots are indivisible single entities, although an entire job lot consists of many identical items. However, splitting an entire lot (process batch) into sublots (transfer batches) to be moved to downstream machines allows the overlapping of different operations on the same product while work needs to be completed on the upstream machine. This approach is known as lot streaming in scheduling theory. In this study, the lot streaming problem of multiple jobs in a two-machine mixed shop where there are two different job types as flow shop and open shop is addressed so as to minimize the makespan. The optimal solution method is developed for the mixed shop scheduling problem in which lot streaming can improve the makespan.
Citation Count: Çetinkaya, Ferda Can; Duman, Mehmet. (2021). "Scheduling With Lot Streaming In A Two-Machine Re-Entrant Flow Shop", Operational Research in Engineering Sciences: Theory and Applications, Vol.4, No.3, pp.142-175.
Scheduling With Lot Streaming In A Two-Machine Re-Entrant Flow Shop
(2021) Çetinkaya, Ferda Can; Duman, Mehmet; 50129
Lot streaming is splitting a job-lot of identical items into several sublots (portions of a lot) that can be moved to the next machines upon completion so that operations on successive machines can be overlapped; hence, the overall performance of a multi-stage manufacturing environment can be improved. In this study, we consider a scheduling problem with lot streaming in a two-machine re-entrant flow shop in which each job-lot is processed first on Machine 1, then goes to Machine 2 for its second operation before it returns to the primary machine (either Machine 1 or Machine 2) for the third operation. For the two cases of the primary machine, both single-job and multi-job cases are studied independently. Optimal and near-optimal solution procedures are developed. Our objective is to minimize the makespan, which is the maximum completion time of the sublots and job lots in the single-job and multi-job cases, respectively. We prove that the single-job problem is optimally solved in polynomial-time regardless of whether the third operation is performed on Machine 1 or Machine 2. The multi-job problem is also optimally solvable in polynomial time when the third operation is performed on Machine 2. However, we prove that the multi-job problem is NP-hard when the third operation is performed on Machine 1. A global lower bound on the makespan and a simple heuristic algorithm are developed. Our computational experiment results reveal that our proposed heuristic algorithm provides optimal or near-optimal solutions in a very short time.