Order batching and picker scheduling in warehouse order picking

This article focuses on the integration of order batching and picker scheduling decisions while taking into account two objectives that have been considered in literature, namely minimization both total travel time to collect all items makespan pickers. integrated problem not only occurs naturally wave picking systems which latest orders becomes key performance metric, but also arises when there is a limit operating time. We present models result from combining these analyze their relationship through bounds. propose column generation-based exact algorithm for problem. The novelty proposed approach lies ability efficiently solving optimality by designing generation subproblem based set batches, makes it challenging optimization due its size. alleviate this difficulty reformulating subproblem, allows efficient implicit enumeration variables. devised Variable Neighborhood Search used as subprocedure within solution algorithm. Finally, we conduct experiments randomly generated instances show algorithms are capable with up 100 orders.