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

Abstract

In this thesis, we consider loading and scheduling problems in a flexible manufacturing system (FMS) in which each part visits only one machine for its entire processing. In this type of FMSs, if tools are not loaded on the tool magazine of the machine for a part assigned to it, they can be transferred from other machines or a tool crib. For an efficient operation of such systems, loading and scheduling of parts and tools should be done carefully. We consider problems of part loading, tool loading, and part sequencing with the objective of minimizing the total tardiness although most of previous research on these problems has focused on maximizing throughput. In this paper, we suggest three heuristic approaches, called list scheduling, sequential, and iterative approaches. List scheduling approach determines loading and schedule of parts and tools simultaneously according to part priorities. In the sequential approach, we solve the parallel machine scheduling problem to determine loading and sequence of parts and then tool loading problem is solved by a heuristic using estimate of tardiness improvement for each tool. The iterative approach solves the part loading and sequencing problem and tool loading problem iteratively using solution of the other problem. Results of computational test on randomly generated problems show that the iterative approach performs better than the others.