Mathematical Models for the Warehouse Reassignment Problem

For several decades, researchers have developed optimization techniques for warehouse operations. These techniques are related in particular to the material handling, the order picking and storage assignment strategies for a myriad of warehouse configurations. It is often neglected that these strategies need to be regularly adjusted in order to adapt to changes in technology, in the demand and/or product offers. Most research on storage assignment provide excellent methods to determine where products should be located. However, the handling part of the problem is often set aside. Moving from one setup to another requires a large amount of work and disturbs regular order-picking operations. This chapter presents the warehouse reassignment problem in order to minimize the total workload to reassign the products to their new locations. We demonstrate how one can move from an out-of-date storage assignment to a better one, in a minimum of working time. We introduce three different mathematical formulations and compare them through extensive computational experiments in order to identify the best one.