Automated storage and retrieval systems (AS/RS) are inventory management systems that are widely used in manufacturing facilities, distribution centers, and warehouses throughout the United States and the world. AS/RS systems generally consist of machines that move up and down one or multiple parallel storage aisles, storing and retrieving products and materials for dissemination to internal and external destinations alike.
The advantages of these systems are numerous. They provide users with increased inventory control and tracking, including greater flexibility to accommodate changing business conditions. These AS/RS systems are comprised of modular subsystems that can be easily replaced to minimize downtime and extend the service life of the overall system. They also reduce labor costs, lowering necessary workforce requirements, increasing workplace safety, and removing personnel from difficult working conditions (such as cold food storage environments). Perhaps most significantly, however, AS/RS systems can produce major savings in inventory storage costs, as vastly improved warehouse space utilization—both vertically and horizontally—creates greater storage density.
CONDITIONS THAT ARE FAVORABLE TO AS/RS
The facilities in which AS/RS are used vary greatly but Howard Zollinger discusses some of the more favorable operational conditions and environments into which these systems have been successfully installed in an article that appeared in Material Handling Management. The environments in which AS/RS can offer the greatest benefit are cold storage, frozen foods, and those in which very strict item tracking is necessary. In terms of the conditions into which an AS/RS installation may be most successfully installed, Zollinger lists the following ten conditions:
- Two or three shifts
- Critical inventory levels
- Production flexibility is essential
- Joint storage of parts and tools
- High land cost areas
- No limit on building height
- Skilled technicians are on-staff or available
- High value parts or assemblies are used
- The number of stock keeping units (SKUs) in not large
- Tight existing site space in which an AS/RS installation may eliminate the need to move
Every situation is different but these guidelines provide an overview of the sorts of applications that are best suited to AS/RS.
Automated storage and retrieval systems do require a considerable up-front investment to install and an ongoing financial commitment to maintain. "Maintaining highly integrated systems requires training and experience and is not without occasional frustrations," noted Michael Wigington in Plant Engineering. "Even the most experienced AS/RS user struggles to support the changing requirements of maintaining aging technology and tired mechanization." The cost of purchasing and implementing an effective automated storage/retrieval system is significant as well, encompassing everything from pre-purchase analysis of supply chain and inventory management needs to the actual purchase price of AS/RS equipment and software. In addition, experts in the use and maintenance of AS/RS systems note that companies often experience significant ongoing costs for maintenance and updating of various subsystems.
These capital expenses can tempt some business owners to cut financial corners, buying "bargain" systems that are ill-equipped for extensive, long-term use. In many cases, such decisions can end up costing far more in the long run. "A long and reliable service life [for an AS/RS system] begins with procurement, not maintenance," wrote Wigington. "Light-duty storage systems are particularly vulnerable by failing to deliver well-engineered equipment and software. These systems require a high level of upkeep and experience a sticky, entangled web of mechanical, electrical, and software problems." When such disruptions occur, the impact can be devastating to small and mid-sized businesses. The toll of interrupted AS/RS service extends from the measurable (lost production and shipping revenue, increased labor costs for repair) to the intangible (diminished workforce confidence in the company's operations, downgraded client confidence). As a result, businesses are urged to examine the long-term implications of their choices when they incorporate an automated storage and retrieval system into their operations.
Feare, Tom. "Staging/Storing: Up, Down, and All Around." Modern Materials Handling. February 2001.
Muller, Max. Essentials of Inventory Management. AMACOM a Division of American Management Association. 2002
Poirier, Charles C. Advanced Supply Chain Management. Berrett-Koehler, 1999.
"State of the Art in Automated Warehousing." Dairy Foods. March 1999.
Van Denberg, Jeroen, and A. Gademann. "Optimal Routing in an Automated Storage/Retrieval System with Dedicated Storage." IIE Transactions. May 1999.
Wild, Tony. Best Practice in Inventory Management. Wiley, 1998.
Zollinger, Howard. "How to Shop for AS/RS and VNA Systems." Material Handling Management. October 2001.