An MILP-based approach to the short-term scheduling of make-and-pack continuous production plants

C.A. MÉNDEZ; J. CERDÁ

Advanced Planning and Scheduling Solutions in Process Industry

Springer

Año: 2003; p. 295 - 321

Many fast moving consumers good manufacturing companies produce a moderate number of intermediates that are combined in many different ways to generate an enormous variety of end products. To do that, such companies usually run continuous production plants on a closed-shop mode; i.e. finished products are mostly required to replenish warehouse inventories. The process structure includes a fabrication area yielding basic intermediates that are stocked in a middle storage space and a packing sector where finished products are manufactured. Intermediates all undergo the same sequence of processing stages at several continuous production lines running in parallel. Those ones required by the same end product may be processed at different production lines and therefore a proper synchronization in the operation of production lines and packing units to avoid large work-in-process inventory is really needed. The problem objective is to develop the optimal short-term schedule for the whole plant such that all end-product requirements are satisfied at minimum make-span. In addition, no work-in-process inventory must remain at the end of the time horizon. A computationally efficient MILP continuous time problem formulation handling independently assignment and sequencing decisions and considering sequence-dependent setup times and specific due dates for export orders has been proposed and successfully applied to a large-scale industrial case.