Concurrent routing, sequencing, and setups for a two-machine flexible manufacturing cell

An approach that allows in-process machine-loading through magazine setups, and concurrently routes and sequences the jobs on the versatile machines, is presented. To illustrate the concurrent approach, a specific two-versatile-machine flowshop scheduling problem, referred to as 2-VFSP, is defined and studied in detail. Theoretical results show that the optimal schedule for 2-VFSP need not have more than two in-process magazine setups, giving rise to the three possible scheduling configurations. Further, it is proven that obtaining the optimal schedule is an NP-complete problem. A heuristic is developed and tested on sets of random joblists, with different setup times corresponding to varying degrees of machine versatility. Results indicate that schedules which incorporate in-process magazine setup(s) may be more desirable when the setup time is small. Thus the use of concurrent scheduling approach which allows in-process magazine setups may be especially useful for systems with very versatile machines