Establishment of economic production rate, production batch size, and production sequence in manufacturing systems with flexible routing

Through automation, manufacturing systems today are being built with increased flexibility to accomodate alternate routings and perform complex operations. Through the technology of programmable fixturing, fixtures and other workholding devices can easily be configured to accommodate varying workpiece shapes and sized. Although increased flexibility is a desirable feature, it does in many cases increase the complexity of planning for production as a result of theincreased number of operations sequences that are available to the analyst. In this paper, the problem of lot sizing and process sequencing in a shop with sequence-dependent production rate, setup cost, and unit processing cost is addressed. Using standard lot sizing model with backorder, the paper develops two separate solution procedures, one based on dynamic programming and the other on graph theory, to simultaneously determine the production rate, operation sequence, and other lot sizing parameters that yield a minimum manufacturing cost plan. In doing so, the procedure automatically integrates the functions of process planning and inventory control. These two functions have traditionally been kept separate in most manufacturing organizations. The implementation of the model in a totally computerized process planning systems is also discussed.