November 1, 2005
equipment & applications | AS/RS

It stores! it retrieves! it picks!

Sure they provide dense storage and fast retrieval, but today's automated storage systems have learned some new tricks too.

By David Maloney

It used to be that automated storage and retrieval systems (AS/RS) pretty much did just that—stored and retrieved products. But with today's push for DC efficiency, automated storage and retrieval systems are fast becoming a strategic part of inventory control and order fulfillment. You might say that these systems have come of age.

Traditionally, AS/RS have been known for their matchless ability to save space by providing dense storage (they can store pallets several deep) and by using normally underutilized ceiling space. Unlike sprawling rack systems, AS/RS are built up vertically—some rise over 100 feet—making them ideal for facilities that have limited footprints. Then there's their versatility: AS/RS can be designed to handle both pallet-sized loads, which they store in high-rise racking systems, and cases and totes, which are placed into mini-load systems.

So how are today's systems different from those of a generation ago? The most noticeable difference lies in the sophistication of their controls, which have become faster and more precise. But more importantly, the systems have become integrated into the picking process itself. "You can use the power of an AS/RS to bring bins of products directly to the worker. It no longer is [just] a storage machine; [it's] now a picking machine," says Rob Schmit of SSI Schaefer. That delivery capability alone allows two or three people to pick more than 1,000 order lines per hour—a particular plus for operations whose orders consist largely of small parts.

Not only can an AS/RS speed up the picking process, it also can increase accuracy. Typically only one tote containing a single SKU is delivered at a time from storage to a picking station, which means workers would have to go out of their way to make an error. Another key inventory control advantage is that products can be dynamically assigned to storage locations based on factors like shortest travel distance, first-in/first-out, pick frequency and product weight. That "slotting" freedom allows the system to optimize its movements.

Today's systems also permit sequenced picking—selecting products in a certain order. Sequencing has a number of advantages. Facilities that perform value-added services, for instance, can pick products from storage in the order in which they'll need to be presented to the workstations where the services are carried out. Companies can also pick in a particular order to build delivery routes, so that the products arrive at shipping docks in the order they'll need to be loaded onto trucks. Similarly, products can be delivered from the AS/RS in a sequence that will make store putaway faster. That is, products for aisle one can be picked into one carton, aisle two into the next, etc.

Some pallet storage systems can also pick a layer of product at a time to build loads destined for a particular customer. Instead of extracting the entire pallet, the AS/RS has grippers that peel off only the top layer, which is then placed onto an order pallet. Additional layers of other SKUs are also added to this rainbow pallet, creating a pallet of mixed SKUs that can be shipped right to the end customer without the need to repalletize products elsewhere in the facility.

Similarly, grippers can eliminate the need to place every item into a tote or onto a pallet. "Carton grippers attached to the AS/RS load extractor mechanism allow direct storage and retrieval of cartons, thereby eliminating the need to repack merchandise into tote boxes," reports Ken Ruehrdanz of Siemens Logistics & Assembly Systems. The result of all these changes has been a shift in the way companies look at the AS/RS. "There are companies now using AS/RS ... as part of [their efforts to change] their distribution business from the front door to the back door," says John King of Daifuku America. "The technology is faster now and allows more applications that were not options 30 years ago," adds Daifuku's Steve Bell.

The Brrrrr factor
Beyond the inventory and picking efficiencies, today's AS/RS can help a company manage one of its bigger expenses—labor. To be precise, an AS/RS can save labor by reducing the operation's reliance on lift trucks and the operators who drive them. A typical crane may do the work of two lift trucks per shift. Lessening the reliance on humans also has some side benefits, such as a reduction in product damage and greater security.

AS/RS can also reduce the need for workers in freezers and other harsh environments. "People do not like to work in freezers and it's often difficult to find people willing to work in that environment," says Dan Labell of Westfalia Technologies. And even if companies can find workers willing to brave the cold, they're likely to pay the price in productivity. Human productivity in an uncomfortable environment like a freezer drops as much as 30 to 60 percent below standard, reports Mike Kotecki of HK Systems. It's far better to allow cranes to operate there and then bring the products out to the worker, who can sit in the relative comfort of the DC.

Automating freezer areas has advantages that go beyond the comfort factor, however. Since an AS/RS requires a relatively small footprint, it can save on energy costs. Some DCs have reported that cooling or providing humidity control for these dense storage areas costs about half as much as climatizing conventional storage systems.

Plenty of choices
Whatever the type of operation, when it comes to installing an AS/RS, today's buyer has a lot of choices in the level of automation. Some customers opt to automate fully, using automated cranes capable of maneuvering in tight quarters to move products in and out. Others take the semiautomatic route, selecting one of the hybrid systems that use aisle-changing cranes controlled by an operator. These systems offer the flexibility to expand as a company grows. "A system like this requires a long planning horizon of five to 10 years," explains Ken Matson of FKI Logistex. Matson advises clients to allow space for additional aisles and cranes that can be added later as demand increases.

Other hybrid solutions include automated forklifts that work in conventional aisles and racking. These don't require operators and basically function as a combination lift truck and automatic guided vehicle.

Not every new AS/RS project requires major construction. Some existing storage areas can be adapted into AS/RS systems, depending on space and aisle width. "Miniloads are quite easy to retrofit into existing systems," says John Ripple of viastore systems. He says that unit load machines that handle pallets are most efficient where there are high ceilings. For buildings with lower ceilings, it's usually better to simply add a rack-supported AS/RS area.

Although height is a big advantage, that doesn't mean that areas with lower ceilings can't be adapted for use by a smaller system or a hybrid solution. "We prefer a ceiling height of at least 30 feet, but we have worked with less," says Terry Krantz of Witron. "Many people think [their sites] are too small to look at automation, but things are changing. There are some very interesting solutions out there that are smaller, modular and expandable and can work for many companies."

About the Author

David Maloney
Editorial Director
David Maloney has been a journalist for more than 35 years and is currently the editorial director for DC Velocity and Supply Chain Quarterly magazines. In this role, he is responsible for the editorial content of both brands of Agile Business Media. Dave joined DC Velocity in April of 2004. Prior to that, he was a senior editor for Modern Materials Handling magazine. Dave also has extensive experience as a broadcast journalist. Before writing for supply chain publications, he was a journalist, television producer and director in Pittsburgh. Dave combines a background of reporting on logistics with his video production experience to bring new opportunities to DC Velocity readers, including web videos highlighting top distribution and logistics facilities, webcasts and other cross-media projects. He continues to live and work in the Pittsburgh area.

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