A storage assignment problem with multi-stop picking tours in an automotive spare parts warehouse

In this study, a storage assignment problem for an automobile spare parts warehouse is considered. Incoming items from the suppliers are located at storage slots in pallet loads with single stop storage tours while outgoing items requested from the company’s service centers are collected on a daily basis with multi-stop pick tours. The problem involves seeking a layout (defined by an assignment of items to storage slots) to minimize the total distance items are moved from the receiving dock to storage slots and from storage slots to the shipping dock. The items requested each day are not the same. Consequently, the number and locations of pick stops in pick tours differ from day to day. This feature of the problem sufficiently complicates the structure to make analytical approaches difficult to use. Two simulation models are developed, one single-level and one multi-level model, to investigate factors that have some effect on the storage assignment problem under consideration. Various insights are obtained for a set of storage assignment alternatives for both models.