Optimizing Mixed Storage and Re-Marshalling Plans

Abstract

This study addresses the problem of optimizing the mixed storage and re-marshalling plans in a block stacking storage system with re-handling. Mixed storage is a storage method in which unit loads of different types are stored in the same bay. The re-marshalling is an activity of moving unit loads from mixed storage to other areas in which unit loads of different types are stored in a segregated way. This removes the need for re-handling during retrieval operations. The objectives of this study are to suggest methods for: (1) estimating the space requirement, including broken space, for mixed and segregated storage; and (2) determining the groups of unit load types to be placed in mixed storage, and the re-marshalling time for each group. Two uncertainties are considered: the types of unit loads to arrive and the times of arrival. A simulation model is used to estimate the space requirement for the two storage methods, and various load composition and arrival time distribution parameters are considered.