Product location, allocation and server home base location for an order picking line with multiple servers

In this paper, we are interested in several interrelated control issues for a ‘pick to order’ (or, ‘strict’ order picking) picking line which stores N=nk types of products in n bins, each with k shelves. To fill each order, a container is transported past the various locations containing products, and the appropriate quantity of each product is removed from its respective storage location and put into the order container using an ‘out and back’ picking strategy. Each of several pickers is assigned a set or ‘zone’ of products. We are interested in the concurrent problems of: (1) product location, (2) picker home base location, and (3) allocating products to each picker so that the expected order cycle time is minimized. We provide easily implemented algorithms to solve these problems and are able to show that the results apply for several alternate picking strategies. For fixed product locations, we develop an efficient dynamic programming algorithm which determines the optimal product allocation and server locations.