Aisle designs in unit-load warehouses with different flow policies of multiple pickup and deposit points

Abstract

This study focuses on investigating the best layouts of a unit-load warehouse for single-command operation. We propose a model for unit-load warehouses having a single cross aisle and multiple pickup & deposit (P&D) points located at the front side of the warehouse. The model is constructed in continuous space for single-command travel and allows the cross aisle and picking aisles to take any angle between 0 and pi. We then search for the best aisle arrangements that minimize the expected single-command distance from a given varying number of P&D points under randomized storage policy. Additionally we introduce three material flow policies to investigate the effect of usage density of P&D points on the design. We also investigate the effects of shape ratio on angles of aisles in the best designs. Last we also solved a problem instance with unsymmetrically allocated P&D points to show how to use our proposed models. Therefore we present that warehouses with width to depth ratio 3:1 are good for high number of P&D points. We also show that the best designs provide more savings in travel over the equivalent traditional design if flows are more concentrated around the central P&D point. The best-found designs also present that the single-command distance can be reduced to 8-20% based on the characteristics of the unit-load warehouse.