Scheduling on three serial duplicate stations in assembly lines with multiple criteria

Due to their long cycle times, some assembly line stations have to be duplicated in order to balance the line. While the ideal case is to arrange the duplicate stations in parallel, material handling and space considerations force these stations to be arranged in series rather than in parallel in some assembly lines. This paper addresses the scheduling problem in an assembly line with three duplicate stations. The considered performance measures are total completion time, makespan, and station idle time. After the problem is formulated, it is shown that any regular performance measure can be minimized by only considering simultaneous assignment of three jobs to the three stations. Furthermore, two algorithms are developed to determine the optimal schedules with respect to the performance measures.