An Application of Warehouse Layout and Order Picking in a Distribution Center

In this study, the mixed pallet order picking process is examined in a distribution center of a logistic firm. For this purpose, we first developed a new layout plan for the distribution center by considering the demands and weights of the products. After the generation of the layout plans, we proposed a new mathematical model to minimize the total distance for picking the orders in a mixed pallet. To pick the process, we also considered that the weights of orders are placed in related mixed pallets. Since the orders are placed on top of each other in a mixed pallet, the following situation in which the heaviest product is placed at the top of all orders and the lightest product is placed at the bottom are avoided because of deformation. With this aspect, the considered problem is distinct from the well-known Travelling Salesman Problem (TSP) in literature. Therefore, by adding a new constraint to the TSP model, it is guaranteed that the rate of weights of orders — placed on the top of one another — will not exceed the threshold value. With the implementation of a mathematical model to the distribution center, we achieved about 28% improvement in the order picking process.