Sorting out the options

Choosing the best sortation system for your warehouse or distribution center (DC) depends on many factors—and it can be an especially daunting task in light of today’s accelerated e-commerce activity and the growing array of high-tech solutions available from manufacturers and systems integrators. But before making plans to invest in that cool system you saw on YouTube or that cutting-edge solution that was demoed at a recent industry trade show, make sure to analyze your facility’s needs and future demands to ensure you make the best decision.

“The one critical [issue] is always data, data, data,” says Andy Lockhart, director of strategic engagement, warehousing solutions at Vanderlande, a company that supplies automated material handling solutions, including sortation systems, for airports, warehouses, and parcel distribution facilities. “What are you trying to sort? How big are the items? How much are you sorting, that kind of thing. Data [is essential] to designing the right system.” 

The right data can determine whether you need a simple sorting solution that’s been around for decades or a more advanced system designed for complex operations—or a combination of different technologies. And in some cases, emerging robotic solutions may be just what you need to get the job done.

MATERIALS AND THROUGHPUT

Sortation is the process of distributing items—by piece, case, tote, or polybag—to specific locations in a facility for packing, shipping, or routing to another destination in a company’s network. The process is common to every warehouse and DC, and at some point, managers will need to evaluate how well their system is working and whether or not it’s time to change or upgrade it.

The first step in that process is to look at what, exactly, is being sorted: What is the size range, the shape of the items, the kind of packaging each item comes in, and the throughput requirement? The answers to those questions will help determine what type of sorter is best for a particular operation, according to Dean Terrell, vice president of engineering at logistics automation and software company Fortna. 

For example, paddle and push sorters can be used to sort a wide range of items in rigid or semi-rigid packaging: Paddles swing outward to divert an item onto a particular path, and pushers extend to do the same. These types of sorters have been in use for decades and represent the most basic, and often most affordable, sorting solutions, Terrell says. 

At the other end of the spectrum, crossbelt sorters are ideal for handling parcels, polybags, apparel, and fragile items. These conveyor-based systems sort the items using “crossbelts”—small segments of conveyor that move products from one location to another within the system. 

Other options include tray-based sorters—often ideal for sorting odd-shaped items—and sliding shoe sorters, which convey items on a surface of aluminum extruded slats, each equipped with a pusher. A series of pushers can be used in succession to move the items off the sorter and divert them onto a particular path. 

“If the product is shipped in round cylinders, well that’s a hard item to handle, so a tray sorter is best for that,” Terrell explains. “If there are a lot of polybags, [flat items], and things of that nature, we would look toward a crossbelt sorter.”

Throughput makes a big difference in system selection. Paddle and push sorters are best for low-throughput applications, such as sorting boxes or totes to loading doors for shipping (although they can be used in high-throughput applications as well, according to Terrell). Crossbelt sorters, on the other hand, are best for high-throughput applications—even those involving small or fragile items—as well as in operations that are sorting a wide range of products, such as e-commerce fulfillment. Crossbelt sorters provide the most gentle and accurate method of sortation, even at high speeds, Terrell says. Sliding shoe sorters offer similar benefits for variable and high-speed operations, especially when sorting products of a variety of sizes, shapes, and weights, the experts say. Warehouse managers should also consider the number of destinations they are sorting to, as this increases the complexity of the sorting process and may drive the need for a higher-end solution. 

ROBOTICS TO THE RESCUE?

Advances in robotic technology are influencing the sorting process as well. Both Terrell and Lockhart say there is growing interest among warehouse and DC managers in incorporating autonomous mobile robots (AMRs) into the sorting process, much as e-commerce giant Amazon.com has done at some of its sortation centers nationwide. At those sites, workers place packages on top of a shuttle-like AMR equipped with a conveyor belt; the AMR then drives the package to a designated location and uses the conveyor belt to propel the package into a chute, which funnels the item to its next destination.

“You’ve effectively got picked goods, each one placed onto a single AMR,” Lockhart explains. “[The AMR] will then take that product to the right exit point. It’s like a shoe on a traditional sorter, dropping [the item] where it needs to go for shipping.”

Amazon’s accomplishments and the “cool factor” are driving much of the interest in AMR sorting, but there’s a long way to go before the process sees much uptake at even the largest, busiest DCs. Terrell says customers are beginning to test AMR solutions and that the future looks bright for large-scale adoption—but only if the customer can justify the investment compared to other automated sorting solutions. He gives an example: Some initial attempts at AMR sortation have involved the construction of expensive mezzanines on which fleets of mobile robots sort items into chutes that funnel the packages into containers below. The concept is sound, Terrell says, but the size and cost of the mezzanine structure can be prohibitive. Proper planning and design is essential to making it work.

“I don’t think suppliers or end-users have figured out the best way to apply AMRs for large-scale sortation just yet, but I do see applications for that in the future,” Terrell says, explaining that the technology is best suited for low- to medium-throughput operations that have a high number of sort destinations. “As the technology continues to improve and the cost continues to come down, robotic sortation will become feasible for more and more applications.”

In the end, it comes down to applying the right technology where it makes sense in your facility—and Lockhart reiterates the importance of planning and preparation in figuring that out.

“How much growth are you planning for? Hopefully, you have more than just next year’s time horizon in your plan,” he says. “I’ve talked to people who are mapping out a 20-year time horizon. It’s important that you size things right or that you build [a system] so you have expansion capabilities down the line. You have to understand your business, your process, and your data so you can design the right solution.”