Mathematical programming can be used to determine, from a set of part-type orders, an input stream composition which maximizes machine utilizations in an FMS (flexible manufacturing system) composed of specified machining resources. Simulation can then be used to estimate the degradation in these utilizations due to their dependency on the following factors ignored in the mathematical programming solution: (1)  secondary FMS resources  (e.g. pallets and fixtures; loading and unloading stations; buffers; type and capacity of equipment for transferring work-in-process); (2)  geometric considerations  (e.g., location of loading and unloading stations, machines, and buffers; routes for transfer of work-in-process); (3)  secondary time requirements  (e.g., transfer times; palletizing and depalletizing times; fixturing, defixturing, and refixturing times); (4)  operating procedures  (e.g., quantity of work-in-process; dispatching rules; part input sequence); (5)  operating discontinuities  (e.g., machine breakdowns; scheduled machine maintenance; machine substitution; breakdowns and/or maintenance of equipment for transferring work-in-process); and (6)  secondary job characteristics  (e.g., the sequence in which parts use machines; fixturing and refixturing requirements; due dates; lateness penalties). This paper presents an example illustrating the sequential use of mathematical programming and simulation to: (1) determine the level of selected secondary FMS resources required to maximize machine utilizations when transfer times are realistic; (2) estimate the degradation in machine utilizations when there are inadequate secondary resources; and (3) determine the sensitivity of machine utilizations to selected operating procedures.
['Thomas J. Schriber', 'Kathryn E. Stecke']
Using mathematical programming and simulation to study FMS machine utilizations