Optimizing the pool allocation of multi-orders in an e-fulfilment centre

With the continuous transformation of digitalization in the past decades, e-commerce is becoming an indispensable part of our society. In the e-fulfilment centres that drive the e-commerce industry, efficient order picking systems are required to competitively handle a large extent of customer orders, selected from a wide product variety spread over an immense warehouse area, in a very limited time period. By pooling allocation, multi-ordered items are assigned to clustered zones within a warehouse. This pooling allocation stimulates the picking performance such that the average time required to pick an item is minimized, as this shortens the picking routes the operators process. As a result, this turns into minimization of labour costs. Simultaneously, fulfilment needs to be managed to ensure timely delivery. In a case study performed at bol.com, a set of constructive heuristics is designed to improve the current pooling allocation method. By a simulation approach, it is shown that the seconds per pick for multi-orders could significantly be reduced, which result in significant annual cost savings for the e-retailer. Accompanied by this reduction in average time per pick, the fraction of orders that are not automatically fulfilled on time increases slightly.