A study on order-batching methods of order-picking in a distribution centre with two cross-aisles

One common practice in order picking is order batching, in which items of two or more orders are picked together in one picking trip. Order batching can reduce the total order-picking travel distance if orders with similar picking locations are batched together and picked in the same order-picking trip. In this paper, the performance of different order-batching methods that are made up of one seed-order selection rule and one accompanying-order selection rule is investigated. A seed-order selection rule selects the first order (i.e. the seed order) in an order batch, while an accompanying-order selection rule selects the rest of orders (i.e. the accompanying orders) to be added to the order batch. In this paper, one investigates the performance of nine seed-order selection rules and 10 accompanying-order selection rules under two different route-planning methods and two different aisle-picking-frequency distributions. The problem environment is a distribution centre's warehouse which has an I/O point at one of its corners and two cross-aisles – one front cross-aisle and one back cross-aisle. One wants to understand not only the performance of every seed-order selection rule and every accompanying-order selection rule, but also their combined performance. The effects of route-planning methods and aisle-picking-frequency distributions on the performance of seed-order selection rules and accompanying-order selection rules are also investigated. Different random problems were generated and tested for this purpose. It is hoped that the knowledge learned from this study can benefit practitioners in distribution centres with order-batching operations.