Generating and implementing schedules for time-critical manufacturing processes

A complicating issue in scheduling parts through some manufacturing systems is that of critical operations. These operations have both a minimum and maximum processing time. (Heat treatment and etch processing are examples.) Critical operations, coupled with the natural interaction of resources that occur in all manufacturing systems, makes schedule generation quite difficult, particularly in an automated environment. It becomes necessary to plan ahead to insure that the necessary resources (e.g., carts) will be on hand to stop the processing when the allotted time is up. This paper briefly discusses existing approaches to the scheduling problem and introduces a new simulation-like method that has great flexibility and generality. In addition, and not to be minimized, the various practical problems of implementing such a scheduler are discussed.