A Study on Mathematical Models for Transforming the Job-Shop Layout Into Flow-Shop Layout

In this paper, we study the problem of transforming a job-shop layout into a flow-shop layout by introducing additional machines, so that all job-related operations can be processed in a flow-shop layout. The objective is to find the shortest sequence of machines, so that the overhead of introducing additional machines can be reduced. This transformation of job-shop layout into flow-shop layout has the advantage of automating the flow-line, which is an important step in digital manufacturing. The study first focuses on a special case (which is studied generally in the literature) where all the jobs would have the same and equal number of operations to be performed in a job-shop, but each job has a different machine routing when compared to other jobs. We propose a Mixed Integer Liner Programming (MILP) model for solving this special case. Further, in order to evaluate the performance of the proposed MILP model, we compare the same with an existing model in literature. From the results, we confirm that the proposed model is superior in terms of the CPU time, in solving the problem instances considered for the study. The study also extends this special case, and considers the generalized case where jobs could have different number of operations, and the study proposes a comprehensive MILP model for solving the generalized case.