Assigning Storage Locations in an Automated Warehouse

A common rule for retrieval from Automated Storage and Retrieval Systems (AS/RS) is to follow a first-in-first-out (FIFO) discipline. In many cases FIFO priority is set by date of manufacture. In some cases, however, the material may be stored in the warehouse according to a FIFO priority which depends on something other than the date of manufacture of that material, such as rules based on shipping container number or date of entry to warehouse. In this case, there needs to be a systematic approach to assigning a range of FIFO priority. A simulation model is developed to test the impact to an AS/RS of different FIFO schemes including assigning priority by arrival date, arrival shift, and container; with an associated range of tolerances for each case. The model is able to handle multiple aisles, multiple levels, and multiple depth-of-storage locations and is scalable in all these dimensions. We consider performance metrics such as average time for storage and retrieval, average time spent relocating items, and total number of crane movements required. The model is exercised in a case study with an automotive manufacturer receiving parts from multiple supplier sources into an AS/RS. Results show that a reduction of up to 20% in non-value-added moves can be achieved.