A mold and die manufacturing shop is a complicated job shop that produces a variety of molds or dies. It takes several months to make a mold or a die and many machining, assembly, and disassembly operations are involved. There are many technological precedence constraints on the operations. The number of machines and workers are limited. Frequent engineering changes make it more difficult to operate the shop. The shop floor is subject to additional disturbances like defects and reworking, operation time variation, machine setups or breakdowns, and emergency work orders. The production schedule becomes obsolete soon and continual rescheduling is essential. The issue is to meet the due dates of the orders in such a complicated shop environment.
We discuss design and development of a loading scheduling and shop floor control system for a mold and die manufacturing shop. Users' needs and functional requirements are discussed and a system architecture is proposed. In order to capture the complicated mold and die manufacturing process, we propose a special process model called BOP (Bill of Process) that represents the processes for manufacturing a mold or a die in a directed graph based data structure. A GUI(graphical user interface) based BOP editor is developed. To generate an initial schedule or a schedule that satisfy given technological or managerial constraints, we developed heuristic dispatching algorithms. The algorithm uses the priority based on the weighted sum of the order importance, the due date of each activity of the order, and the remaining work times of each activity for the order. A Gantt chart based schedule editor is developed for the planner to tune the initial schedule so as to satisfy additional technological and managerial constraints that are not considered for generating the initial schedule. The editor is also used for rescheduling due to engineering changes and shop disturbances, and for shop floor control to manage the progress. The functional architecture and data structure for the schedule editor are discussed.
