Talking to experts, considering the system's design and how products are handled, are key steps managers need to take when they are determining if AS/RS is the right fit for their inventory management processes. Dan Graves, production engineering manager for Quad Graphics (www.qg.com), a printer of magazines and catalogs based in Sussex, Wis., made the decision to install the first automatic storage and retrieval system (AS/RS) more than 10 years ago.

Graves needed a fast and accurate system to handle work-in-progress and finished goods. Quad Graphics now has three unit-load AS/RS systems that are 85 ft. by 107 ft., and 120 ft. tall. The three AS/RS have a total of 42,000 storage locations that hold between 5,000 to 10,000 SKUs. The company actually outgrew its original AS/RS because the layout of its facility limited the expansion of the system.

Making the Right Equipment Specification

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A successful AS/RS application may have a 15-year lifecycle. The challenge, says Graves, is designing a flexible AS/RS that can remain relevant and productive over the years as industries and customer demands change. "You don't want to realize seven to eight years into the lifecycle that the system is not flexible enough for the changes in the industry." Incorporating flexibility into an AS/RS adds to its cost. However, adds Graves, "it will give you a longer lifecycle for your system."

Before making such an investment, Graves recommends leveraging the expertise of the AS/RS supplier base. "Find out who the AS/RS providers are and speak to as many of them as possible. Have them walk through your process, listen to what they have to say and start your quick study at that point," he says. Managers need to involve their production staffs in any decision process. They know the operation's processes best and will be able to discuss its finer details.

Building layout and lot size can constrain expansion plans. However, says Dan Labell, president of Westfalia Technologies, Inc. (York, Pa, www.westfaliausa.com), "AS/RS shines when you are landlocked and you need to go up." Most warehouses have 30 ft. ceilings. Modifying the building and installing a 100-ft. AS/RS system can give companies two to three times the amount of storage space in the same footprint. "This opens up a lot of opportunities to either stay at the same site or reduce the capital outlay for land, which could provide a good justification [for installing an AS/RS]," he says.

Customers who purchase AS/RS technology are paying for two things: storage capacity, the number of pallets being put in the rack, and throughput. How fast inventory turns through the rack is determined by the system's cranes. An effective setup requires the right pairing of the rack size to the crane size. Graves learned a valuable lesson with his first AS/RS. He added more rack without adding more cranes.

"The system ended up not having enough crane horsepower to service the addition volume of storage," he says. In retrospect, he adds, the system needed to have another aisle and crane so Quad Graphics could get the true benefit for its investment.

The company's two new AS/RS systems from Westfalia feature three rails under each pallet support, which allows for a variety of pallets to be stored in each location. This rack design eliminates the need for slave pallets to transfer loads from one pallet type to another.

To save space in any warehouse, different SKUs are often stored in the same storage bay. AS/RS systems enhance this capability. Pallet loads of different items can be stored on the same rack shelf and the cranes can quickly, accurately and efficiently shuffle pallets around and select the correct pallet for extraction.

Quad Graphic's current AS/RS configuration has two aisles and four cranes. Two cranes are located in each aisle. "If one crane goes down, the other crane in the aisle can be used. In addition, there is crane redundancy from the adjacent aisle, because the system's design allows for cranes to reach through the rack and reach pallets from adjacent aisles," Graves says.

When purchasing such a system, managers need to decide if they want to use hoists with chains or wire ropes. Chains cost more, but will last for about eight years. Wire ropes may need to be replaced every two years, which requires about eight hours of crane downtime. The chains on the cranes from Westfalia have a vertical lift speed of 400 ft per minute for a 1,500-lb. payload. "The result," Grave says, "is the vertical speed does not become the bottleneck [in the system]. The speed produces a smoother, faster process."

To facilitate greater uptime for its equipment, Westfalia's AS/RS locates all of the equipment that needs to be maintained on the floor level of the system, giving workers easier and faster access to the components when repairs are required.

There can be less product damage in AS/RS systems compared to a conventional system because the systems handle product more consistently compared to lift trucks, which can cause damage when a driver brakes or goes around a corner too quickly. In contrast, AS/RS systems are programmed with specific acceleration and deceleration curves that can vary by product. The more stable the system structure, the more aggressive the curves can be programmed, which makes the machine faster.

Another possible benefit of AS/RS systems is low utility costs. Many systems operate unlighted except in areas where order picking or replenishment occurs. Most AS/RS systems do have some lighting in the aisles to let employees spot debris or look for anything wrong with the machine.