A STUDY ON DECISION RULES OF A SCHEDULING MODEL IN AN FMS

Flexible manufacturing systems (FMSs) are designed to combine the efficiency of a mass-production line and the flexibility of a job shop for the batch production of a mid-volume and mid-variety of products. To control FMSs is more complex than transfer lines or job shops because of the flexibility of machines and operations. In general, FMS operation decisions can be divided into two phases: planning and scheduling. The planning phase considers the pre-arrangement of parts and tools before the FMS begins to process, and the scheduling phase deals with routing parts while the system is in operation. This paper focuses on the scheduling phase. We establish six decision points involved in the operations among parts, AGVs and machines. The dispatching rules associated are evaluated based on simulation experiments. The performance measurement is defined as a weighted index of multi-criteria, including time in system, mean tardiness, maximum tardiness, system utilization, number of machines locked, buffer size, and work in process. The Taguchi method is used in the simulation experiments to study the relationship between the multiple performance measures and the dispatching rules in six decision points.