Design and operations of small-parts-handling automated warehouses

Abstract

During the last decade, in the area of material handling, unit-load automated storage/retrieval systems(AS/RSs) have been the subject of many researches. The needs for automated warehouses which handle small parts often found in electronic, pharmaceutical and chemical industries are expected to increase in the near future. In this regard, this thesis deals with the problems arising in the design and operation aspects of small-part handling warehouses such as storage carousels and man-on-board(MOB) AS/R systems. First part of this thesis is devoted to developing a design model of a storage carousel in which storage racks are rotating so that items can be picked without any travel of the S/R machine in the warehouse. We develop an analytic model to evaluate throughput performance of the system. And then, based on the results, we present a mathematical model for designing an economical configuration of the system which satisfies the required throughput. The model incorporates both initial investment and operating costs. A partial search procedure is employed to obtain an optimal solution and implemented on an IBM PC. Three fundamental policies in warehouse operation are where to store items (storage policy), how to combine orders to form batches (batching policy) and how to sequence items within a batch (batching policy) and how to sequence itemswithin a batch (picking policy). These policies are closely related to system efficiency and often required in simple form to ensure fast and efficient results. Second part of this thesis focuses on developing efficient rules for each policy in an MOB AS/RS. For the batching policy, an optimization model is derived with the objective of minimizing total processing time. Then, taking into account of the operation characteristics in the S/R system, heuristics are developed for the model based on cluster analysis, and compared with existing algorithms through computer simulation. Next, a heuristic procedure is developed fo...