Ramifications of tool magazine size on the makespan and routing flexibility of flexible manufacturing systems

Although tool magazine capacity is considered to affect the relative cost of the system, no study exists that examines its impact on the day-to-day performance of FMSs. Tool magazine capacity plays a vital role in part grouping, which subsequently affects tool loading and part routing. These, in turn, affect the makespan and routing flexibility. A key issue is how does makespan and routing flexibility of a system that requires part grouping due to inadequate tool magazine capacity compare with that of a system that doesn't require part grouping. Further, how do factors such as changes in part mix, production volumes, and operational policies chosen to run an FMS influence the foregoing effects? Alternately, the procedure developed can be used in solving FMS production planning problems, with the aim of achieving a performance level closer to that of an ideal FMS. In an ideal FMS, each machine is capable of performing all operations of all parts scheduled for production and it has the requisite tools in its tool magazine. The above issues are addressed while considering two levels of tool magazine size: limited and unlimited. By developing and using two relevant models which concurrently solve part grouping, tool loading, and part routing problems, two FMSs are modelled and their results are statistically compared. Results show that for an FMS with limited tool magazine capacity, the makespan increases by as much as 18%, and routing flexibility decreases by as much as 17%. In addition, the production environment and operating policies also are found to influence makespan and routing flexibility.