Dual-tray Vertical Lift Module for order picking : a performance and storage assignment preliminary study

Among all the warehouse operations, order picking is the activity that always attracts a lot of interest in research, since it presents a complex combination of several interacting factors, often involving human operators. Considering the system overall performance improvement, it has been proved that it can be achieved by reducing the distances travelled by the pickers, as well as by improving their ergonomics working conditions, also through the adoption of automated solutions. In small parts order picking, the need of reducing travelled distances and improving ergonomics turn out to be even more important. The present paper proposes a preliminary study concerning a particular automated parts-to-picker, small objects picking system, called Vertical Lift Module (VLM). Although the value of such a solution is already acknowledged in industry, its evaluation from a scientific point of view is still lacking. Here a first simulation model for the performance study of a VLM is introduced. Then, this simulation model is applied for the comparison of three different storage assignment strategies: random storage, class-based storage with the product classes divided per trays and class-based storage with the product classes divided within all trays.