Layout design in manual picking systems: a simulation approach

Manual picking system productivity is greatly influenced by layout design (i.e. the layout scheme and the number of aisles). In fact, layout plays an important role in determining the expected length of pickers’ tours which is itself a relevant component of the time required to complete a given set of orders. This paper presents a simulation approach to efficient layout design of the picking area in picker‐to‐part systems using random or cube per order index (COI)‐based storage policies. The optimal number of aisles depends on both strategic/long‐term and short‐term decisions. Indeed, layout is a function of the total storage length which, in turn, is related to strategic decisions concerning the forward/reserve problem, i.e. the choice of the fraction of items to be located in the picking (forward) area. Moreover, layout preferences seem to be strongly affected by operating decisions concerning batch size, i.e. number of picks in a tour, and the adoption of a COI‐based storage policy. Some design guidelines are provided for both stable environments where the operating conditions are well defined, and for unstable contexts where conditions may vary.