Manual order picking optimization: an innovative approach

In the last years, a growing demand of smaller and smaller production lots lead warehouse operations to focus on the creation of multi-item unit loads and on the making of components kits to supply assembly/production systems. Several scientific contributions (de Koster, 2007) have showed that manual order picking is mainly composed by travelling, searching and picking activities. These contributions have widely studied the reduction of travel times, introducing a lot of models concerning the routing optimization, layout configuration and class-based storage allocation assignment, based on COI (Cube per Order Index) curves (Dallari et al., 2009, Heung & Guy, 2006, Manzini et al, 2007). The present paper aims to deepen this research field, introducing an innovative and integrated approach in order to optimize the picking activities, since they are very time-consuming and very expensive. Several new methods and procedures have been introduced and implemented in different warehouses to solve this problem, such as Part-to-Picker or particular Picker-to-Part solutions. The present research introduces an integrated approach to the correct choice of order picking solution to optimize the total time spent, considering also the searching and picking activities and using an innovative and evolved analysis of COI curves, based on the correlations between the classes.