Order sequencing for picker’s fatigue reduction in the pick-and-pass order picking system

Pick-and-pass order picking is used widely for small but expensive products such as cosmetics, medicines, and healthcare products. In such picking, each picker picks items that are located in their own zone and passes the bin to the succeeding picker until all the orders are picked in sequence. In addition to the traditional objective of minimizing the makespan, in this study we consider the fatigue of the pickers, which we define to cumulatively increase as the picker has to work on the waiting bins without a break. Given a set of orders to pick, the fatigue of the pickers will depend on the sequence of the orders. We propose various heuristic rules for order sequencing to identify - using simulation - the rules that yield an order sequence which will reduce the total fatigue and deviation of fatigue among the pickers by evenly distributing the picking load for each picker over time.