Dynamic sequencing of jobs on conveyor systems for minimizing changeovers

Abstract

This research investigates the problem of minimizing setup costs in resequencing jobs in a system that consists of first-in-first-out conveyor segments. Sequence changes are limited at conveyor junctions in these systems. We first define the generalized problem of resequencing jobs to queues at intersections with precedence relationship between jobs. Sequential ordering problem is a special case of the above problem. Then, we limit our scope to the conveyor segment selection problem at a diverging junction with precedence relationship among jobs. We model it as a binary integer program. We show that the problem can be modeled as an assignment problem when load balancing is omitted. We also propose a Lagrangian relaxation-based algorithm, which utilizes a special problem structure for getting an optimal solution, as well as a heuristic algorithm for quickly getting a near-optimal solution with load balancing. Finally, we discuss the case study which motivated this research, details of the discrete-event simulation model we developed, and numerical results.