Automated Storage: Developments facilitate lean handling
June 02, 2010 - MMH Editorial
Automated storage systems -including tote-based mini-load automated storage and retrieval systems (AS/RS), pallet-based unit-load AS/RS, and piece-based horizontal and vertical carousels- continue to offer users myriad benefits. Among them, a reduction of labor in item retrieval and putaway, enhanced tracking and organization of stored items and a compact storage footprint.
As the economic downturn forces more companies to practice lean handling techniques, the latest developments in these technologies are yielding more efficient picking and enhanced returns on investment. Here is a look at the latest trends
Mini-load AS/RS systems have incrementally crept up in heights and speeds in recent years. Now reaching as high as 78 feet, with travel speeds as fast as 23 feet per second, suppliers have been developing independent mini-load handlers and drive systems that compensate for mast movement with motor-driven anti-pendulum and belt-driven omega drives.
Initially used as a stand-alone storage system, mini-loads have become a much more integrated part of an overall picking strategy. “In this economy, companies are trying to achieve the lowest cost per piece picked,” says Ross Halket, director of automated systems for Schaefer Systems International Inc. (704-731-1625, http://www.ssi-schaefer.us). To attain that goal, facilities are using systems like mini-loads to reduce labor.
As an example, carton flow rack is being installed alongside the mini-load aisle, allowing pick faces to be replenished directly by the system, Halket says. By picking here, users can store overstocks up high while compressing the storage footprint for more floor space. This also permits a technique called station by-pass picking.
“In a station by-pass system, there are two conveyors—one inside the carton flow rack, and one gravity conveyor in the front. Totes only get diverted to the pickfaces where product is needed,” Halket explains. “That reduces the number of pickers by eliminating traditional pick-and-pass picking, where speed is limited by the slowest picker in the line.”
Well-entrenched in food and beverage handling, mini-load AS/RS is growing in popularity for smaller retailers, adds Bill Ostermeyer, vice president of sales at viastore systems (616-977-3950, http://www.viastore.com). “The technology allows you to do a better job at sequencing and fine tuning the cubing and loading of trailers for efficient delivery and unloading at the retail stores. This is because of the ability to control the release out of the system in a very logical manner.”
Additionally, Ostermeyer continues, mini-loads are taking the place of conveyor in many facilities for sortation, holding lanes and sequencing.
New designs also include an approach with multiple shuttles in one unit for applications that need dynamic product sequencing to support goods-to-person picking, pick face replenishment and mixed case palletizing, says Ken Ruehrdanz, warehousing and distribution market manager for Dematic (877-725-7500, http://www.dematic.us).
In this approach, a shuttle located on each level within the system moves horizontally to deliver totes to an elevator. In turn, the elevator moves the totes on the vertical axis. “The high rate capacity of this design results in a smaller footprint with fewer aisles to achieve throughput rates,” says Ruehrdanz. “It’s also modular and scalable, which enables future flexibility.”
Unit-load AS/RS are used in distribution centers for storing pallet loads of goods, replenishing of mini-loads or for direct picking. In manufacturing plants they store raw materials, finished goods, work in process and spare parts for equipment.
“With companies being forced to do more with fewer resources and fewer employees, the benefits of a unit-load AS/RS are 100 percent order control, visibility and traceability within your facility,” says Todd Jedelsky, account executive with Murata Machinery (704-394-6900, http://www.muratec-usa.com). “The system keeps account of what’s going in and out, so users are not correcting mistakes as frequently.”
“In line with advances in supply chain management, users are seeking automated storage equipment with high-throughput for shorter lead time and inventory reduction,” adds Nobo Morita, president of Daifuku America Corporation (801-359-9900, http://www.diafukuamerica.com). “Users demand high-rise storage equipment to minimize floor space requirements.”
That need has translated into systems as high as 164 feet and an increased emphasis on equipment that reduces carbon dioxide emissions. Similarly, suppliers are working on reducing the weight of the equipment, particularly the stacker crane portion, says Jedelsky.
“Doing that reduces the drive motor capacity to enable lower power consumption,” he says. Also available is power regeneration through braking and downward movement of the hoisting carriage. This enables unit-load systems to return power to the grid for up to a 30 percent reduction in energy consumption, Jedelsky asserts.
For those interested in automating their unit-load handling but financially unable to invest in traditional unit-load AS/RS technology, vendors are creating work-arounds that utilize other equipment to mimic the process at a fraction of the cost.
“It’s what I call the ‘poor-man’s AS/RS,’” quips Mike Kotecki, senior vice president of HK Systems (262-860-7000, http://www.hksystems.com). “It’s very economy driven. Companies have been asset constrained for a while, so they’re only willing to invest in technology very carefully.”
This retrofit-based approach takes an existing conventional facility using either fork trucks or unit load very-narrow-aisle (VNA) trucks interfacing with standard rack and replacing those machines with automation. In one form, automatic guided vehicles with high reach perform AS/RS duties using existing rack under existing roofs.
“Alternately, we’ve developed an AS/RS made specifically for continued use of existing pallet rack comprised of rail-guided, forked vehicles—one per aisle—to replace manned machines with automation,” Kotecki explains.
Horizontal and vertical carousels
Offering a high return on investment, horizontal and vertical carousels continue to provide an ideal means to store small parts and handle slow- and medium-movers. Both technologies have evolved in their design and are used to provide increased storage density as well as more flexible picking.
While horizontal carousels have typically been used in a pod formation—with three to four units arranged in an arc to support one picker with minimal travel—some companies are moving to podless picking, arranging as many as nine carousels flush along one axis.
“This method allows be more flexible in their staffing,” explains Paul Roy, vice president of marketing and product management at System Logistics Corp. (207-784-1381, http://www.systemlogistics.com). “Previously, nine carousels would be divided into three zones and picked by three operators. With podless picking, companies can staff peak periods with three people, and slow periods with one person treating the area as a single zone—with the other two redeployed elsewhere.”
Although standard horizontal carousel bins measure 24.5 inches wide, certain suppliers offer bins as wide as 48 inches that are presented to the picker in a clamshell formation, doubling the pickface to 96 inches for increased productivity, says Roy.
Today’s vertical carousels and vertical lift modules offer increased flexibility through modular designs, notes Ed Romaine, vice president of marketing for KardexRemstar Inc. (800-639-5805, http://www.kardexremstar.com). “If your inventory changes, you can add pick windows, change heights, and program every tray within a unit to run at a different speed depending on whether its contents are fragile or not.”
Also, says Romaine, many systems incorporate light curtains that scan the heights of the items stored on each tray. The system’s firmware crunches the numbers and then automatically stores the trays in the unit to the closest half-inch for maximum density. During slow periods, the unit can be directed to re-scan and determine the most compressed stacking formation to free up additional space.
“The system also analyzes which trays are the most commonly used and stores them opposite the pick window for shortest travel time and fastest productivity,” says Romaine.
Finally, there has been a push for specialty vertical carousel applications that incorporate refrigeration, freezer, humidity or clean room control units, says Brian Cohen, vice president and general manager of Hanel Storage Systems (412-787-3444, http://www.hanel.us). The carousel becomes a self-contained environment, with monitoring systems to ensure that the products inside are kept at the desired state.
“The difference is between building and keeping a big room at temperature, or building and keeping a box at temperature. The box is more environmentally-friendly and more efficient from both a building and a running perspective,” Cohen concludes.