Order batching design for a modular fulfillment center

Mun Geet Ow Yong, Purdue University

Abstract

This thesis is divided into two chapters, each consisting of materials from independent journal papers that addresses the issue of order batching in fulfillment centers which utilize the modular order picking areas. In chapter one, an order batching framework designed for the modular picking area is proposed. A modular picking area is a unique picking layout; originally designed for the fulfillment of store orders. Each module is essentially a picking zone where a take-away belt is accessible at any point. In addition, each module has permanently assigned pickers who operate as a team to simultaneously fulfill a common batch of orders. The proposed framework utilizes a distance discriminator procedure to determine orders’ batching priority and to aid picks to picker assignment. The performance measures of interest are TPacked, which represents the system throughput and; MaxSlot, which gauges the congestion of the packaging chutes. Simulation results indicate that the proposed framework has an impact on the system throughput and is highly influenced by the interaction between order selection rule and batch size. The relationship between the two factors are identified and summarized. The main contribution of this chapter is the proposal of the order batching framework which take into consideration of the modular picking layout. In chapter two, a customer order is considered as complete only if it is shipped out. Thus, a new dimension namely the orders to outbound freights assignment is introduced. Four order selection rules, namely R1, R2, R3 and R4, that consider picking efficiencies as well as orders to freights assignment, are proposed. These rules are evaluated by their performance on the total number of orders picked, TP, and the total number of orders shipped, TS. Experimental results confirm that both R1 and R2, the single dimension rules, produced polarized performances. On the other hand, R3, the weighted approach produced mixed performance. The overall performance of R4 closely resembles the performance of R3. In addition, freight arrival schedules, batch sizes, weight ratios, lengths of lead windows as well as interactions among these factors have significant impact on the rules’ performances. This chapter has two contributions. First is the creation of the order selection rules which take into consideration the outbound freight patterns. The results gained from investigating the outbound freight patterns and its effects on the performance measures is the second contribution.

Degree

Ph.D.

Advisors

Yih, Purdue University.

Subject Area

Industrial engineering

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