Looking to stay on top of your order fulfillment game? Zone routing offers the benefits of goods-to-person picking at a fraction of the cost.
Polaris Industries' star is shining brightly these days. In fact, business has been so good that the company is expanding its picking capabilities at its largest distribution center, located in Vermillion, S.D. The well-known maker of snowmobiles, off-road vehicles, and other sporting equipment uses this facility and a regional one in Wilmington, Ohio, to distribute parts and accessories.
For the expansion project, the company has chosen a fulfillment method that combines conveyors with split-case picking. Known as zone routing, the strategy is a form of goods-to-person order fulfillment, meaning it eliminates the need for workers to travel up and down aisles to gather items for orders. And it can be a highly efficient strategy. Zone routing often results in productivity rates of 100 to 150 line items picked per operator per hour, according to Dematic, a company that specializes in automated material handling and logistics solutions and that supplied the Polaris zone routing system.
"One reason to use conveyance and zone routing is an efficiency play, as it eliminates walking. Instead, the cartons come to you," says Paul Eickhoff, director of operations for Polaris Parts, Garments, and Accessories (PG&A) distribution.
As for how it works, zone routing is essentially a variation of pick-and-pass technology. In pick-and-pass operations, conveyors send order cartons or totes through each of the various pick zones. Workers select any items needed from their zones and pass the carton along to the picker in the next zone. What's different about zone routing is that the carton is not routed through each zone. It is diverted only to those zones that contain items required for the order. In a sense, it has the advantages of a goods-to-person system at a fraction of price. Think of this as goods-to-person "lite."
"Zone routing is an accepted technology with a good return on investment," notes Ken Ruehrdanz, manager, distribution systems market for Dematic. "You can get a lot of throughput and performance from zone routing. It works for low, medium, and high rates, and is productive while being fairly compact." For these reasons, he says, the application has caught on across a wide range of industries, including apparel, industrial supplies, food and beverages, office supplies, pharmaceuticals, medical supplies, and personal care products.
Polaris is no newcomer to zone routing; it has used the strategy at both of its facilities for some years now. In fact, the system now undergoing expansion in Vermillion dates back to 1997. The current initiative calls for additional Dematic conveyors and new racking to be installed to double the split-case picking zones to 16 from eight. The new conveyors for the system are being installed next to the old conveyors. The two will run side by side until the transition is complete. The facility is also adding new conveyors that will allow cases to be picked directly to conveyor belts.
THERE'S SLOTS TO LIKE
For Polaris, much of zone routing's appeal is its ability to handle a wide range of products. The Vermillion facility alone houses 60,000 stock-keeping units (SKUs), which range from service parts and tires to filters and accessories. That kind of variety would be difficult to accommodate in a fully automated system, such as a miniload shuttle setup.
Not so with zone routing. Zones can be configured to be as large or small as needed, depending on the products' size, how often they're ordered, and the need to situate like-products together. Plus, these systems allow items to be stored in pallet flow racks, carton flow racks, and shelving, and permit fast reconfiguration as needs change.
Zone routing also gives companies the flexibility to handle fluctuations in volume, whether they're caused by seasonal swings or simply uneven daily order patterns. For instance, at Polaris, as many as five people might be assigned to a zone during peak periods, which typically occur between 11 and 2. When activity is slow, a single worker can cover two or more zones.
To take best advantage of all of that flexibility, of course, you must have good slotting. The system must be able to keep precise track of the whereabouts of every item. And it has to be able to balance work evenly across the various zones to avoid logjams while still ensuring workers in other areas are kept busy.
At Polaris, it's a job that's never finished. "Reslotting is a daily process," acknowledges Eickhoff. "We have someone working on it full time. Off road, on road, snow, and summer—we are in a constant state of motion on our SKUs and introduce lots of new products on a regular basis."
INS AND OUTS
While zone routing has been around for a couple of decades, advancements in conveyor design have made the process even more economical and productive. Some systems now allow cartons to be introduced at different start points, eliminating the time they would otherwise spend passing by zones with no picks. "If volumes are high and order sizes are small, you don't want the cartons to have to flow through the entire system," explains Luther Webb, director of operations and solutions consulting at Intelligrated, an automated material handling technology supplier. "You can also create 'early outs' so that the carton can go to shipping from a number of the zones without passing every zone," he says.
Today's systems also employ loops so that if a traffic jam develops in one zone, incoming cartons can be routed around the zone and sent back to it later. Alternatively, control software can be deployed to direct the carton to another zone that contains the same product.
Other conveyor technology advances, such as 24-volt direct current operation, help save energy and wear on equipment components. Most zone routing systems contain sensors designed to power down sections of conveyor when no cartons are present. Plus, new designs and faster diverts allow for more efficient processing than in the past. "Conveyors and diverts now have the ability to handle higher rates," says Boyce Bonham, director of integrated systems and controls at Hytrol Conveyor Co. "In the past, we could handle rates of about 20 to 25 [diverted] cartons a minute. Better controls and equipment now allow for about 35 to 40 cartons a minute through those zones."
Since zone routing systems usually incorporate conventional conveyors and controls, implementation can often be completed in a matter of months—a big time savings over designing and installing a fully automated goods-to-person system. "It is a quick turnaround," says Bonham. "It is low risk, and a tried-and-proven technology." On top of that, the technology is highly scalable—a plus for fast-growing operations like Polaris.
As for the "brains" of the operation, most zone routing systems are overseen by a warehouse control system. Polaris, for example, uses the Dematic Sort Director, which receives pick instructions from a warehouse management system (WMS) and then transmits directions to the handling equipment. But systems can also be set up to accept order information directly from an order entry system or enterprise system, bypassing the need for a WMS altogether.
When planning for the expansion of its picking system, Polaris decided to change its process to have workers pick items directly into shipping cartons rather than in-house totes. This saves the step of unloading items from the tote and repacking them in a shipping carton later in the process. But the decision also had some implications for the conveyor design. In particular, the shift meant the new conveyors had to be a bit more carton-friendly than their predecessors. For example, the rollers had to be spaced closer together than they were in previous models. In addition, the conveyors and transfer points had to be designed to convey empty (or nearly empty) cartons that have little weight to provide the necessary friction.
Polaris's new conveyors also feature accumulation areas to keep cartons from bumping up against one another. This is crucial for any zone routing application, says Intelligrated's Webb. "Accumulation allows you to pause the carton for a moment and wait for that zone to clear."
In Polaris's daily operations, bar codes attached to each carton are scanned automatically as the carton approaches a zone. If nothing from that zone is needed for the order, the carton continues its journey. But if that zone does contain a required item, a set of small belts, about the width of a car's fan belt, pop up between the conveyor's rollers to gently divert the carton to a nonpowered conveyor spur at the pick zone.
When a carton arrives at the zone, a worker stationed there scans its bar code with a radio-frequency (RF) device to find out what items are needed. (Voice and pick-to-light technology can also be used for this purpose.) Once the selections have been made, the worker deposits the carton back onto the powered conveyor system. If more items are needed to complete the order, the carton then heads to the appropriate zones; if not, it proceeds directly to shipping.
While Polaris opted to pick directly to cartons, not all operations make that choice. Some companies prefer to use totes to gather picks and repack the items later, according to Dematic's Ruehrdanz. That might be the case if the company's processes call for a worker to scan each item right before shipping for one last accuracy check or add extra protective packaging for high-value items.
It's worth noting that uses for zone routing systems aren't limited to order picking. Polaris, for instance, is also using the conveyors to feed replenishment. Workers can deposit original cartons from vendors or totes of repacked items directly onto the conveyor at the start of the zone routing system. The control system then diverts the cartons or totes to zones that require replenishment. Workers there scan the bar-code labels for directions on where in the racks to place the incoming items. Inventory systems are updated at the same time to reflect that the products are now available for orders.
About the Author
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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