An algorithm for batching, sequencing and picking operations in a warehouse

Order Batching is an optimization problem related to the picking process of orders in a warehouse. It consists in grouping the orders (each order is composed by a list of items to be collected) received in a warehouse in a set of batches of a maximum fixed capacity. Then, a route to collect the items in the same batch must be conformed. In this paper we tackle a variant of this problem known as Order Batching and Sequencing Problem where each order has a certain due date. This variant consists in grouping the orders into batches and then sequencing them, in such a way that the tardiness of each order (the extra time over the due date needed to collect it) is minimized. In this paper we propose a Variable Neighborhood Search algorithm to tackle the problem. Our approach outperforms previous attempts in the state of the art.