Simultaneously Optimizing Storage Location Assignment at Forward Area and Reserve Area - a Decomposition Based Heuristic

This paper addresses the Two-level Storage Location Assignment Problem (TSLAP) for two level low-level picker-to-part warehouses. The first level consists of a forward area from which all picking is done. The second level consists of a reserve storage area, from which the forward area is replenished. A large part of the cost of operating the warehouse is a function of the assignment of items to locations at both the reserve storage and the forward area. The cost of the storage location assignment at the forward area is dependent on the storage location assignment at the reserve area and visa versa. This, however, is often neglected in the existing literature. We solve the TSLAP simultaneously for the reserve area and the forward area. Based on randomly generated test instances we show that the solutions of TSLAP compare favorably to solutions found by other algorithms proposed in the literature.