Storage Allocation Methods, Storage Size and Service Level under Uncertainty in Manual Order-picking Systems

The most common objective of manual order-picking systems is to maximize the service level which is composed of a variety of factors such as average and variation of order travel time, order integrity, and accuracy. A crucial link between manual order-picking and service level is travel time, which has a great impact on allocation efficiency. Storage allocation methods and storage size are two main factors to concerns travel time. However, it is difficult to allocate storage blocks and fix on the size of storage blocks for customers because of stochastic demand. This paper gives the measurement of consistency of service level based on service time and the formulations for picking time, the first travel time, and the second travel time, which are components of service time. The paper emphasizes the impacts of storage allocation methods and storage size to service level under uncertainty. We also give and discuss the case in Kunming International Flower Auction Market (KIFA) about storage allocation methods, storage size and service level. When appropriate method to storage allocation is adopted and reasonable size is given in KIFA, service level and allocation efficiency will be improved rapidly.