Due-date based loading and scheduling methods for a flexible manufacturing system with an automatic tool transporter

We consider the loading and scheduling problems in flexible manufacturing systems (FMSs) in which each part visits only one machine for its entire processing. In this type of FMS, if required tools are not loaded on the tool magazine of a machine, they can be transferred from other machines or a tool crib. For the efficient operation of such systems, loading and scheduling of parts and tools should be done carefully. This paper focuses on the problems of part loading, tool loading, and part sequencing with the objective of minimizing the total tardiness. We suggest three heuristic approaches, called list scheduling, sequential, and iterative approaches. In the list scheduling approach, loading plans of parts and tools and schedules are determined simultaneously according to part priorities. In the sequential approach, a parallel machine scheduling problem is solved to determine the loading plan and the sequence of parts, and then the tool loading problem is solved using the part loading plan. With methods similar to those used in the sequential approach, the part loading and sequencing problem and tool loading problem are solved iteratively in the iterative approach. Results of computational tests on randomly generated problems show that the iterative approach performs better than the others.