Order picking systems: Batching and storage assignment strategies

We consider batching and storage allocation strategies in a manual order picking system of small parts which processes high volume of orders. The arrivals of orders are assumed to follow a Poisson process, and the quantity of items in an order is assumed to be independently and identically distributed negative binomial variates. The order picking system is modeled by a two-stage queueing system with batching and picking activities. Bounds and approximate estimates for the mean and variance of the turnover time (total service time) of a batch of orders are derived. The quality of the results is evaluated via simulation. A comparison between uniform and skewed item storage assignment is also presented. The effects of batching and the batch size on the service time are discussed.