Order Batching and Batch Scheduling in an Order Picking System

The easy accessibility of the internet in today’s world has contributed to the immense popularity of on-line purchasing and its prestige as a widely preferred sales channel for consumers worldwide. One of the significant effects of the booming e-commerce business has been the distinctive characterization of customer orders. To a large extent, these orders which are placed from a wide spectrum of products, consist of a small number of items, and have highly unpredictable demand quantities. This characteristic of the orders translates directly to the need of operational efficiency in managing warehouses that play a crucial role in correctly and quickly handling customer orders. Among several processes carried out in warehouses that are not automated, order picking is a manual operation which directly affects the efficiency of the warehouse. In this study, we address critical order picking problems such as the storage location assignment problem, the order batching problem, the batch assignment problem, the picker routing problem, and the batch scheduling problem. Some combinations of these problems have already been studied in the literature in a detailed fashion, while there exist few studies that integrate the batch scheduling problem with others. The aim of this chapter is twofold. First, it is concerned with the description of these integrated problems and their inter-relationships. Second and more importantly, it highlights potential research areas that arise as a result of the efforts to integrate batch scheduling issues with the other order picking problems.