Watching a well-designed sortation system in action is endlessly fascinating. Products merge into the induction area and line up like well-drilled soldiers, jump onto the sort conveyor where they speed along until some unseen signal causes them to veer off to the takeaway chute. It's mesmerizing to watch, and a wonder that somehow some underlying software knows where each product is headed and directs it to the right place.
Of course, as with an elegant ballet, all that fluid and seemingly effortless movement is the result of plenty of sweat and preparation. What makes it work so well is carefully laid groundwork and substantial investment.
Sortation systems can offer enormous productivity gains to distribution centers with volumes as low as 30 cartons a minute or so. The trick is, first, determining if automated sortation is the way to go; second, choosing the right system—or set of systems—for a particular operation; and finally, taking the time to make sure it works the way it's supposed to work.
The choices for distribution have expanded in several ways in recent years as a result of technological advances. Today, there are systems that can handle items as small as a lipstick tube and others that can accommodate hefty cartons. The variety of items that can be handled by a single system has expanded as well. Specialized systems can fit in smaller footprints, making sortation an option for a greater number of facilities. And sortation is being used in a greater number of operations in the distribution center than was the case not too many years ago.
"When I first got into this business, we sold a lot of shipping sorters," says Brené Tymensky, vice president of design engineering for Fortna, a systems integrator. "Now we sell a lot for replenishment, we sell sorters for packing lanes, for print-and-apply lanes and for special operations like carton sealing or dunnage fill and sealing. I'm seeing more and more sorters used for direct-to-customer returns, sorting goods back into the active pick. I've even seen a sort system for putaway."
Adds Ken Ruehrdanz, business strategy Siemens Dematic, "Automated sortation systems in the distribution center can be made more efficient by allowing the sorter subsystem to provide multiple functions. For example, a cross-belt sorter could accommodate sortation required for returned merchandise as well as receiving, order consolidation and shipping."
Dean Starovasnik, a solution development manager for Peach State Integrated Technologies, also teaches seminars on sortation topics in association with Georgia Tech's Logistics Institute. He says sorting technology has advanced rapidly over the past decade. "We're seeing sorters in the 600 to 700 feet-per-minute range. You can get a 300-carton rate out of that. That's a twofold increase over the last six to eight years. And reliability has gone hand in hand with that. The manufacturers recognize that it's the heart of a shipping business and cannot afford to go down."
Tymensky says that technological developments such as the introduction of variable frequency drives have opened up the potential of sortation to more users. Both Tymensky and Starovasnik cite the development of narrow belt sorters and small item sorters as important contributions to sorting technology.
The potential for highly automated sortation is demonstrated by the distribution center operated by the German direct-to-consumer retailer Klingel, based in Pforzheim, Germany, and serving customers in Germany, Belgium, the Netherlands and Austria.
The highly automated system can sort 10,000 items an hour to packing stations. The cross-belt sorter, designed by Siemens Dematic, first delivers an appropriately sized carton from one of eight carton erectors to one of 100 packing stations. Once the cartons are in place, the system inducts products, which are diverted into the waiting cartons. Then the system takes the cartons away to a case sealer and label applicator. Peak output of the system, according to Siemens Dematic, is 5,000 cartons per hour.
Another, Phillips-Van Heusen, a large apparel business that distributes several other brands as well, recently completed a sortation project at its Jonesville, N.C., DC that was aimed at substantially improving productivity and volume to serve both its outlet stores and its retail customers. A particular challenge was the mix of products, some in polybags, some in boxes, with a variety of weights and handling characteristics. The company selected a Mantissa system and Hytrol conveyor that can sort 12,000 items per hour to more than 500 destinations. The system included a newly designed takeaway chute, dubbed Aardvark by Mantissa, that could handle the full array of items delivered by the tilt-tray sorter.
But getting to that point takes substantial preparation and coordination both with potential suppliers and an internal team.
More homework? Afraid so
Businesses often consider automated sortation when their growth leaves their existing fulfillment system unable to keep up. Starovasnik says, "The first questions to ask are, Do you need sortation? What are you trying to accomplish? Can it be handled manually?"
Next comes an analysis of the products involved and their handling characteristics. Tymensky points out that products for sortation must be readily identifiable by an auto ID system. "Do you have a system to identify the product and make the sort decision?" he asks. That's important because the technological brain that runs the system must rapidly identify every product and know its destination.
Volume is a critical determinant in whether automated sortation makes sense for an operation, as well as what technology to select. "The lower the rate, the harder the justification," Tymensky says. In general, he explains, rates of about 30 cartons a minute are at the low end of sortation systems. "At 30 to 70 cartons per minute, the justification is easier. Above 70 cartons per minute, usually sortation's justified."
Starovasnik says, "Once you've decided that automated sortation is a requirement, the next question is, What is it that you are sorting? What are the items' dimensions and weights? How heavy and small are they? Smaller items sometimes drive decisions. It's harder to sort small things." He adds that the discussion should also cover what items might not be included in an automated sort, either because their handling characteristics make it too difficult or because they are slow movers.
Tymensky agrees. "The key driver is the makeup of the product," he says. For instance, if sorting small parcels or envelopes, the solution may be a tilt-tray or cross-belt sorter rather than a shoe sorter.
Then come questions on the speed required. Again, that requires a detailed look at the operations. Starovasnik says, "Are you trying to ship parcels that all ship in the last hour, or are you shipping LTL and can scan and sort all day? If you're shipping 2,000 cartons but only during an hour a day, that's a lot different from shipping 2,000 cartons over the whole day."
Tymensky adds, "Rate is always an issue.You look at it not as an average, but when the business occurs. If you do a lot of pre-picks and holds and release at the end of the day to hit cutoffs, even though your average is low, you need a high-rate system."
An important part of the discussion is projected volumes for several years out. "Most sortation systems don't pay for themselves in the first year," Starovasnik says. "Most are designed for five to seven years— that's our standard."
Peak shipping volumes versus average volume are another consideration, Starovasnik says. If a peak rate is a large multiple of average rates, it may make more sense to staff up for peaks rather than build a system to handle it. "Otherwise, you're sorting air," he says. But he adds that some businesses, where peak season is crucial to annual profitability, may opt for a system to handle those volumes. So business strategy is an important component of the decision.
The sum of the parts
The sortation system does not act alone, of course, and once a goal is set for sort speed, it has implications for picking, for the induction system and for the takeaway system. It also affects the technology that drives all those systems—the sort controller and the way it receives and manages data from the warehouse management system. The sort controller, says Tymensky, "makes all the difference in the world."
Merge and induction systems account for a substantial portion of the cost, and the faster the system moves, the pricier those can get. "So much is affected by which sorter you choose, what tool you're using, you might as well be asking how you should design the building," Starovasnik asserts.
Tymensky says, "When I think of sortation, I think of it being all encompassing. In the early days, when we thought about high-rate sorters, you couldn't feed them fast enough or take away fast enough. You have to think of them as systems."
"The speeds and product types make up a matrix," adds Starovasnik. The more variety and the higher the speed, the higher the cost. Conversely, he says, "If you reduce the variety or the speed, you can reduce the cost."
While the primary driver for automated sortation is productivity, Tymensky points out that the systems yield other benefits as well. "Automated sortation allows more QA checks," he says. "You can check weights against anticipated weights, check shipping labels—you have quality control and higher accuracy.
"The other thing is, if you're doing mail or parcel sortation, it allows for a more finite sort. Automatic sortation allows route-stop sorting or segregation by product types." For instance, a grocery DC can sort by frozen, cooler or dry groceries, or sort so that fragile items arrive to be stacked on the top of a pallet.
Tymensky also says that a sortation system can provide benefits in picking processes that feed into it. "You can do a better batch pick," he says. "You can deliver a large quantity of an SKU to the end of the sorter. It really adds flexibility to your pick options."
The analysis, preparation and investment required in a sortation system means that a sortation project takes many months from the outset to completion.And it also means involvement of a team that starts with executive leadership and includes operations management, information technology specialists, engineering, and on to the supervisory level. It might also include IT suppliers, such as the WMS provider.
The projects are complex, and the effort required should be understood at the outset. One manager, who oversaw a multiyear project, told his system supplier, "The system, though still officially in start-up, is going well. But I have to say that pulling it off, making it a success, was the most significant challenge I've ever faced."