The Effects of Loosely Coupled Hand-Off Operations on Bucket Brigade Order Picking Systems

초록

Hand-off delays in bucket brigade order picking systems occur when downstream pickers have to wait to receive totesfrom upstream pickers. This paper introduces a method, termed a loosely coupled hand-off, to reduce waiting delays,and it conducts analytical and simulation studies to identify insights. The loosely coupled hand-off method, which ispopular in industry, is preferred by pickers to reduce the expected hand-off delays of downstream pickers. We expressthe looseness of the hand-off synchronization, i.e., the threshold of the early release, as real number τ ≥ 0. To overcomethe throughput reduction, we generalize the looseness from the perspective of a picker’s decision making andthroughput improvement and extend the looseness parameter into a practical hand-off framework with measurementsincluding the relative looseness of the hand-off (δ), the increment of work-in-process (WIP) (ω), and the work rangeof the loosely coupled hand-off (ψ) allowed. We find that the adjusted loosely coupled hand-off framework to balancethe hand-off delay reduction and the throughput gains reduces hand-off delay by 30~88% and improves throughput by2.7~6.4%. In general, to attain the overall system’s throughput improvement, the gains in the hand-off delay requirethe WIP level and the range adjustments.

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