A flexible tool for warehouse design and picking optimization

This paper describes the development of a software tool, programmed in Visual Basic for Applications - Microsoft ExcelTM, to support the design of a new warehouse, e.g. to decide on the number of aisles or cross-aisles as a function of the (expected) order size before the new warehouse is built. The software tool was designed to be flexible enough to reproduce the geometry of any warehouse as a function of its main parameters, i.e. number of blocks, number of cross-aisles, shape factor and total storage capacity. In the same tool, different routing policies have been embodied, including the traditional heuristic strategies (S-shape, return, largest gap and aisle-by-aisle), as well as an “advanced” return policy that allows exploiting the cross-aisles where available. The chosen context of analysis of these policies is that of manual, picker-to-parts, order picker systems. The effectiveness of the tool developed has been tested on a sample warehouse, of fixed storage capacity, where the software was used to compute the travel distance of the picker as a function of the routing policy, shape factors, number of aisles, number of cross-aisles and size of the order picking list. The best policy, i.e. the policy that returned the shortest path, was identified for each warehouse configuration investigated. Besides supporting the design a new warehouse, the proposed software tool is expected to be useful also to test the performance of an existing warehouse and to substantiate operational decisions, e.g. the choice of the routing policy to be implemented.