Big Picture: A new take on unit-load storage

As end users optimize their facilities, high-density dynamic storage is getting a fresh look.

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If you attended the Modex show last February, you may have seen demonstrations of new unit-load storage technologies at booths sponsored by Power Automation Systems (PAS) and the Italian company Smoov.

Both companies were highlighting solutions that combine deep-lane storage rack with automatic carts or shuttles that move pallets to and from storage. They weren’t alone. Frazier Industrial was also exhibiting its semi-automated shuttle technology for pallet storage.

If you missed them, you’re not alone. For the last couple of years, automatic guided vehicles (AGVs) and mobile robots have been getting a tremendous amount of attention. Less noticed have been the innovations around pallet-handling storage technologies.

Look closely, however, and you’ll find technologies that fill the gap between conventional deep-lane pallet storage and a fully automated unit-load automated storage and retrieval system (AS/RS). Within the industry, these solutions are referred to as high-density dynamic storage. These solutions aren’t right for every application, or even every pallet handling and storage application; however, for facilities that have already gathered the low-hanging fruit, they may be the next level of improvement. 

These solutions also illustrate a way to think about storage. In many instances, storage is no longer simply a process unto itself. In fact, conventional reserve storage is set apart from modern supply chains designed to keep product in motion as much as possible.

Instead, as the term “dynamic” suggests, storage is becoming an integral component of other processes, such as manufacturing work-in-process, order fulfillment and shipping. Applied dynamically, storage becomes a tool that facilitates even faster movement of product through a facility. The best solutions minimize the space and labor devoted to storage as well as reduce the length of time a product remains at rest.

In this Big Picture, we’ll look at what’s behind this emerging area of unit-load storage and how the technologies are being applied.

What’s in a name?
The concept behind high-density dynamic storage isn’t new. Rack companies such as Interlake Mecalux, Frazier Industrial, Konstant and LoadBank— a solution now marketed by SafeFlo Technologies—have offered some type of high-density dynamic storage for years.

What differentiated these early solutions from conventional deep-lane pallet rack was the movement of the pallets within the rack—the dynamic part—so that a lift truck didn’t have to enter the rack system to store or retrieve a load. The idea was to improve productivity and reduce damage to the racks because a lift truck operator wouldn’t have to slow down to safely handle pallets deep in a lane.

What differentiated them from an AS/RS was the degree of automation: Regardless of the solution, they were designed to interface with a lift truck rather than operate autonomously like an AS/RS.
These largely niche solutions were used by manufacturers that needed to store a large number of pallets of a limited number of SKUs. More importantly, they didn’t need to go 60 or more feet high to justify the cost of implementation as is the case with a full-blown AS/RS. For those reasons, the primary competition was conventional rack. 

If the technology has been around so long, what’s changed? And, why are end users taking a harder look now? The simple answer is the increasing complexity of the supply chain: As end users push more and more requirements upstream, manufacturers and distributors need to meet those demands while still controlling costs.

“The analytics that our customers are deploying to understand their product mix and velocity is allowing them to be more refined about how they manage their SKUs,” says Dan Garside, general manager of Frazier Industrial’s Canadian operations. “That’s bringing a better appreciation for these unique systems.”

The systems allow shippers to isolate the ideal mix of SKUs and improve selectivity in a high-density environment. “A dynamic storage system allows you to get between 80% and 90% occupancy compared to about 60% occupancy in a conventional drive-in rack system,” says Garside. “That basically means you can reduce the amount of space you need for storage by about 30% for the same number of pallet positions and possibly use fewer lift trucks.” At the same time, he adds, productivity is improved because a pallet is always at an aisle and ready for pickup.

These solutions work especially well in operating environments where manufacturers are managing smaller levels of inventory per SKU, managing an increasing number of SKUs or making smaller and more frequent shipments, says Elisabet Fasano, brand marketing manager for Smoov ASRV S.r.l. “AS/RS technology can achieve high throughput and fast response times when the throughput is high and stable,” Fasano says. “But the design is rigid and cannot easily adapt to rapid changes in demand. Shuttle-based systems can be quickly and easily expanded to add more vehicles to support rapid growth or peak seasonal fluctuations.”

In addition to complexity, at least four other factors are influencing the interest in high-density storage.

  • The next level of optimization: Manufacturers have historically focused on building higher speed production lines to bring down their manufacturing costs. Now, they are being asked to do more with their distribution systems. “They can no longer rely on bulk storage on the floor,” says Fred Grafe, president of operations and sales for PAS Americas. “They have to reduce their supply chain costs.”

  • New packaging that won’t stack: The beverage industry, in particular, is looking at high-density storage as an alternative to floor stacking. “With new packaging designs, you can’t stack a pallet of PET bottles on top of another pallet of PET bottles,” says Tom Coyne, CEO of System Logistics. “Coming off the production line, you need an efficient way to store product.”

  • Retrofitting an existing building: Most end users would rather retrofit an existing building than build a new site, says Dan Quinn, president of SafeFlo Technologies. Some of that is being driven by green initiatives. Some is simple economics: High-density dynamic storage allows an end user to make use of the total cube in an existing building. Quinn adds that these solutions can also be configured to conform to the shape of the building or to work around structural supports. “If you need to make it L-shaped, you can make it L-shaped,” says Quinn.

  • Remove employees from a hostile operating environment: No one wants to work in a freezer or refrigerated warehouse space. What’s more, those spaces are expensive to operate. “The fuller you can fill a freezer, the lower the utility cost,” says Steven Beyer, director of business development for Retrotech. “With a high-density dynamic solution, you increase the storage density and there is no more need for a labor force that constantly requires warm up breaks.”

Regardless of the product or industry, the applications where high-density dynamic storage works best are manufacturing or distribution environments where product turns are measured by days or weeks instead of months.

“For many of the users we’re talking to, storage is taking on dimensions beyond just putting things away and then retrieving them when they’re needed,” says Beyer. “It’s a more active, dynamic and multi-faceted component of the supply chain.”

Four types of solutions
At least four types of high-density storage solutions are available on the market today. They include mechanical, semi-automated and automated solutions. All three combine high-density, flow-through rack storage with some type of technology to provide pallet movement.

Mechanical solutions: In this solution, pallets are loaded at one end of a lane and are retrieved from the other end. Pallet movement through the racks is controlled by air. Pallets rest on a rail on either side of the rack. Wheels or rollers are set atop an air hose in an inner channel on either side of the rail. When the pallet is at rest, the air hose is deflated. To move the pallets forward, the wheels or rollers are raised by the pulsation of air in the hose. When the channel rises, the load moves by gravity in a controlled manner. As the hose deflates and the inner channel is lowered, the load sets down on the rails for a soft braking. The solution can handle loads as light as 50 pounds and heavier loads from 4,000 to 10,000 pounds in the same lane. It will also operate in freezers as cold as -25ºF. “We’ve done projects as many as 20 pallets deep and the technology has been used in deeper lanes than that,” says Quinn of SafeFlo. The system works best in first-in/first-out applications, especially in buffer storage applications.

Radio-controlled shuttle technology: In this solution, radio-controlled shuttles or carts are used to move pallets. As with the mechanical solution, pallets are only moving forward or backward in a lane. A lift truck operator places a shuttle in a designated lane where work is about to take place. Once the cart is in place, the operator uses a radio transmitter to instruct the cart to perform the command. The operator may drive away to retrieve or deliver another pallet while the shuttle works on its own. “The beauty of a shuttle system is that you can match up the number of shuttles you need with the number of lift trucks working in an area,” says Grafe of PAS. He adds that a facility moving 16 to 18 pallets an hour with just a lift truck can move up to more than double that amount with a shuttle. “It’s best suited to high-volume, fast-moving product, especially at the receiving or shipping docks.”

Cable-driven shuttle technology: The shuttles and carts described above are moved from rack to rack by a lift truck operator. In a variation, pallets are moved using a combination of three technologies that allows for computer-controlled load sequencing in a deep-lane storage area. The process begins when a pallet is loaded by a lift truck or a conveyor onto a vertical transfer lift. This device delivers the pallet to different levels in the pallet rack. Each level of the rack system has a cross-aisle transfer vehicle that can move across all the lanes of storage on each level. The cross-aisle transfer vehicle deposits the pallet onto a cable-driven shuttle that slides forward and backward in the deep storage lanes. “Because the system has three axes of travel, we can configure the system based on how pallets are shipped and routed and not just on increasing throughput,” says Retrotech’s Beyer. “The software automatically places loads into optimal positions based on the order patterns. Fast movers are more accessible and slow movers are positioned out of the way.”

Automated shuttle technology: Automated shuttle technology is used to automatically store and retrieve pallet loads of product. Where a unit-load AS/RS uses a crane in each aisle to store and retrieve pallets, automated shuttle technology uses a vertical lift to deliver the pallet to the right level in the system. One or more shuttle vehicles on each level move pallets to a storage location within the lane, similar to the shuttle in a mini-load shuttle. In a deep-lane configuration, a second shuttle or roll cart can drive into the rack to deposit or pick up pallets. The primary advantage is the additional speed in high-throughput applications. “Shuttle-based systems for totes are meant to be faster than conventional mini-load AS/RS systems,” says Coyne of System Logistics. “Similarly, these systems are faster than unit-load handling AS/RS systems.”

New processes
High-density dynamic storage solutions were initially installed to provide very efficient reserve storage. Today, as the nature of storage changes, they are being applied as a complement to a conventional process such as work-in-process or shipping. They are also being combined with other highly automated technologies to create new order fulfillment processes.

“The concept, and what we’re working on, is a blending of automation and high-density dynamic storage techniques,” says Quinn. “The merge between the two has been slow to catch on, but we’re now seeing interest among the end user community in solutions that bridge that gap.”

As an example, Quinn’s company worked with Muratec to develop an alternative to a conventional unit-load AS/RS for a freezer application in the meat industry. A mechanical solution provides the dense deep-lane storage. Instead of dedicating a pallet-handling crane to service each aisle in the AS/RS, the system will be serviced by one crane that can automatically load pallets into the system and a second crane at the front of the unit to remove pallets from storage to fill orders. “The cost savings came from reducing the number of cranes required to automate the system,” says Quinn. “In addition, we’re reducing the amount of energy required to maintain the temperature in the freezer since you don’t have to light it, and you don’t have lift trucks going in and out of the temperature-controlled area.”

System Logistics is pairing mechanical technologies and automated shuttle systems with a case buffering and picking system to automatically sequence and build mixed-SKU pallets. “SKU proliferation is creating a much more labor-intensive picking process,” says Coyne. “If there are a limited number of SKUs coming off the line, we can put them in a mechanical system. If there are a lot of SKUs, we can put them in an automated shuttle system.”

The high-density storage systems feed a mini-load case buffering system that sequences cartons to the palletizing line as needed. “The flow rate we get with one of these high-density systems allows us to build a 20,000-case buffer instead of an 80,000-case buffer and still keep up with demand,” says Coyne.

On the shipping dock, the solutions are being used to reduce the amount of space required for staging and to speed up the truck-loading process. In a typical solution, the system will begin pulling pallets required for an order when the truck driver pulls into the dock. When the truck is ready for loading, “the lift truck driver is simply pulling a pallet from the end of the system and putting it directly into the truck,” says Retrotech’s Beyer. “In one of our installations, it’s only 15 feet from the end of the system to the back of the truck.

“As we deploy more of these systems, we’re finding more end users who can get many of the benefits of AS/RS without the heavy costs associated with an implementation,” says Frazier’s Garside. “These systems aren’t right for everyone, but there are a lot of possibilities for many industries.”

Companies mentioned in this article
Automha USA
Frazier Industrial
Interlake Mecalux
Power Automation Systems (PAS)
SafeFlo Technologies
Smoov ASRV
http://systemlogistics.comSystem Logistics

About the Author

Bob Trebilcock
Bob Trebilcock, editorial director, has covered materials handling, technology, logistics and supply chain topics for nearly 30 years. In addition to Supply Chain Management Review, he is also Executive Editor of Modern Materials Handling. A graduate of Bowling Green State University, Trebilcock lives in Keene, NH. He can be reached at 603-357-0484.

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