Optimizing Plant-line Schedules and an Application at Hidden Valley Manufacturing Company

Abstract

A plant line schedule specifies a plant's sustained batch operations over time with detail sufficient to manage all activities. Plantwide considerations include restrictions on how production centers can be formed from production lines, packaging lines, conveyers, and so forth; the cost and time of product-package item setups, changeovers, and shutdowns; honoring instock service levels, minimum inventory, and committed shipments; recognizing efficiency gains with longer batch runs; respecting crew constraints; and the costs of materials, labor, and carrying inventory. We developed a cost-minimizing optimization model, PROFITS, that features multiple independent time streams for various categories of events that mimic existing periodic reviews of operations. PROFITS is embedded in a graphical user interface that eases the grueling aspects of scheduling, preparing data, controlling scenarios, and visualizing results. At Hidden Valley Manufacturing Company, completing an eight-week plant-line schedule takes about an hour. This is much faster than manual scheduling was-and the schedules are better.