In this paper we address the problem of batching orders in a parallel-aisle warehouse, with the objective to minimize the maximum lead time of any of the batches. This is a typical objective for a wave picking operation. Many heuristics have been suggested to solve order batching problems. We present a branch-and-bound algorithm to solve this problem exactly. An initial upper bound for the branch-and-bound algorithm is obtained using a 2-opt heuristic.
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