Earlier this year, Pacific Sunwear moved into a new distribution center designed to efficiently deliver product to the growing chain's more than 700 mall-based clothing stores (See Hot fashions, Cool DC - July, 2002). In only its second month in the new facility, the company set a record for units and dollars processed, all with 30% less labor.

Much of those gains can be attributed to the materials handling system that includes four sliding shoe sorters that process receipts, sort to packing stations, divert cartons to sealing lanes and route store-bound shipments to the proper outbound docks.

While few facilities have as much sortation as Pacific Sunwear, the potential advantages of automated sorting systems are clear - efficient movement of many items to multiple destinations in the DC.

Fortunately, there are plenty of sortation options that can meet a variety of requirements. There are five major types of sorters; sliding shoes, pop-up diverters, pusher systems, tilt tray units, and crossbelt sorters. Each has its role in facility operations and is chosen for the product it can sort, the speed and quantity required, the available space within the building and the return on investment for the installation. When properly integrated with picking, shipping, receiving and other facility operations, major efficiencies can be gained. It is simply a matter of picking the right system for the job.

Sliding shoe sorters are the most common mid-capacity sorting systems in use. They offer high speed and positive diverting down any number of selected lanes. Sliding shoe sorters have the ability to sort just about any size or shape of carton efficiently. Depending on the size of the system, these sorters can handle up to 200 cartons per minute.

Sliding shoe sorters are placed in-line within a conveyor system. They consist of a long conveying apparatus with small rectangular blocks known as shoes situated to one side of the conveyor. Items sorted by the system must be in cartons or totes. These are scanned upon entry. As they reach the divert point, software directs a series of the shoes to slide across the conveyor, which causes the tote or carton to be gently pushed down a divert spur.

An advantage of sliding shoe sorters is that products do not have to be justified to a particular side as is the case with other sorters, such as push diverters. Instead, items can be sorted from either side. Accumulation, however, must be performed to produce the proper amount of spacing between cartons for the shoes to operate properly.

Sliding shoes are used in a variety of operations, such as shipping, receiving and order-filling. Many facilities use the same sorter for a number of duties with different diverts assigned to the various tasks within the building. Larger systems may combine two sliding shoes together with a short conveyor between them. These larger systems may have as many as 80 diverts, with some units working bi-directionally.

A sophisticated bi-directional sliding shoe sorter serves double duty at National Retail Systems' crossdocking facility in North Bergen, N.J. (see Crossdoc-King -Jan., 2002 ). NRS is a leading consolidator for department stores such as K-Mart and Marshalls. These clients rely on the facility to receive products from their warehouses and then sort cartons into loads destined for individual stores.

Upon receipt, cartons are conveyed up to the sliding shoe on the second level. The unit has 67 diverts, of which 60 serve shipping lanes. Cartons that are needed for immediate processing are diverted to the appropriate dock for loading onto outbound trucks. Others that will be loaded later are directed to six staging areas where they are held temporarily. During a later wave, these staged products are manually loaded onto a conveyor and fed back through the sorter for a second pass. This time they are diverted to one of the shipping lanes. The sorter can perform 125 sorts per minute, with a current throughput of 45,000 cartons in a shift.

The most commonly used sortation systems used in manufacturing and distribution environments are pop-up sorters. They are highly flexible and cost-efficient systems. Pop-up diverts are typically placed in-line within a conveyor system, which allows them to be located just about anywhere conveyors run within a building.

There are two major ways in which pop-up sorters are used. Some are simply used as stand-alone units to divert cartons from one conveyor to another. Others place a series of pop-up diverts in a line to re-direct cartons down various spurs or packing lanes. This set-up comprises a low-cost sorting solution.

Pop-up sorters are composed of a series of wheels or rollers set at an angle within the middle of the conveyor. The wheels pop up as the item to be diverted approaches, changing the direction of the carton.

Some systems use steerable wheels that allow tighter divert angles. The angle of divert greatly affects speed. Systems with a divert angle of only 30 degrees can sort 100 cartons per minute. Right angle transfers of 90 degrees typically handle about 60 cartons each minute. Many of these steerable wheel systems allow diverting to either side of the conveyor. Cartons typically retain their orientation when sorted on a pop-up system.

One user of pop-up sortation is Carlisle Tire & Wheel, one of the nation's largest manufacturers of tires for lawn and garden equipment, golf carts and trailers (see  Rollin' Rollin' Rollin' -   Feb., 2002 ). The company's Carlisle, Pa. distribution center uses the technology to divert tires to 30 packing lanes. Up to 65,000 tires pass daily through the sorter at peak.

The tires are picked from racking in a pick module and placed onto a conveyor that feeds the sorter. Other tires are brought from floor storage in a reserve area and also inducted into the sorter. The tires ride directly on the conveyors and pass into the sorter without requiring a slip sheet or container. When a tire reaches the proper point in the sorter, wheels pop up and redirect it down the packing spur. Workers then either place the tires gathered in the spur into large shipping cartons or stack them onto pallets.

Similar to pop-up and sliding shoe sorters, push diverters are positioned in-line on a conveying system. As a product approaches its divert point, an arm or pusher slides out and gently moves the carton to its new destination lane. Designs vary, with some pushers impacting the carton while others sweep the carton as it contacts the pusher. Many systems simply use swing arms that move out over a conveyor so that when the carton arrives it encounters the obstacle blocking its path and turns to a divert lane.

Care must be taken with the type of product diverted. While these systems are suitable for totes, baggage handling or parcel post systems, the impact nature of the units do not make them acceptable for sorting cartons containing glassware or other fragile products.

Push systems are relatively simple and require little maintenance. Similar to pop-up units, they are used for lower-volume sorting of about 150 diverts a minute. Most push systems can be designed to cover a wide range of divert angles - typically from 20 degrees to 45 degrees. A more severe angle can also be attained, but to do so requires that the carton slow down.

Magid Glove & Safety, which manufactures and distributes industrial and consumer work gloves, protective clothing and safety equipment (see Retrofits like a glove -March, 2002 ), uses push diverters to process split-case orders at its Chicago distribution center. Magid's DC is unique, as it was originally built as a manufacturing facility in the 1930s. It consists of many small rooms that have been converted to storage and upgraded with new automation.

Order totes are used to gather products for individual customers. Conveyors carry the order tote to each room. If a pick is required from the items stored there, the tote is diverted with a swing arm to a staging spur. Workers then place the selections into the tote and send it on its way where it will again divert to any other rooms requiring picks.

Once all picks have been gathered, the tote enters a push divert sorter that feeds 16 packing lanes. As the tote reaches the proper divert, an arm reaches across to block its path, redirecting it down the lane. At the bottom, workers remove the items from the totes and pack them into outbound cartons.

Tilt trays are highly automated sorting solutions. They perform at a fast pace of up to 200-300 sorts a minute depending on system size. Facilities that do a large amount of batch picking often use tilt trays to break them into individual orders.

A system consists of a train of trays that runs along a circular track. Unlike the other sorters that work in-line within a conveyor, tilt trays are typically stand-alone systems that require either manual or automated induction. Instead of diverting to a conveyor spur, tilt trays usually divert products into chutes that gather the product for other processes.

Each product is placed on an individual tray upon entry and is then automatically scanned. When the circular train approaches the assigned destination, the tray tilts, causing the product to slide off of the tray and down the chute. Most units use mechanical systems to tilt the trays, while some systems utilize a wedge-shaped bellows below each tray that inflates and causes the tray to tilt.

The trays are designed to hold a wide range of light to medium-weight products, and are often well suited for shoes, soft goods such as clothing and other non-fragile items. Many systems are designed to sort bi-directionally.

Athletic wear manufacturer New Balance uses a tilt tray system to sort split case orders at its shoe distribution center in Ontario, Calif. (see  Achieve new balance - Oct., 2001 ). Picks are made into totes from a mezzanine and then conveyed to the sorter's induction stations. Here they join full cartons of shoes brought from other storage areas. Workers open the totes and cartons and manually place each box of shoes onto one of the sorter's trays.

A bar code on the shoebox is scanned, showing the management software that the box resides on that tray. Once the tray reaches its destination, it tilts the shoebox down a chute to a packing station below. The mixed SKUs of shoes are then placed into outbound cartons. The system can sort up 9,000 pairs of shoes an hour into its 360 double-layered chutes.

Crossbelts are typically the fastest sorters found in facilities. These high-capacity units are able to sort over 300 units per minute based on size. Because few facilities have such high demands, these are the least common sorters.

As with tilt trays, crossbelts are built in a circular track surrounding multiple destinations. These destinations are typically accumulation chutes, but can also be additional diverts or shelving. Instead of trays, a crossbelt system features a series of small powered belts installed perpendicular to the track. Products must also be inducted either manually or automatically into the system. When a product reaches its destination, the belt powers on, moving the product across the unit and to its destination of either a chute or conveyor.

An advantage of crossbelts is that they provide a positive discharge - the belt physically moves the product while other systems, such as tilt trays, rely on gravity. Because of this, crossbelts are suited to sorting small or lightweight items such as books, videotapes, and compact discs. Most systems are able to sort bi-directionally.

Everything from a videocassette to a four-foot long box can be sorted on the crossbelt system at Blockbuster Entertainment's distribution center near Dallas. The high performance of this technology was a major ingredient in Blockbuster's decision to consolidate nine warehouses into this one DC.

The sorter efficiently handles videos, music CDs and cassettes, directing them to a number of processing areas. Receipts and returns use the system to sort for putaway in storage and for returns to vendors. Similarly, orders are picked from storage and sorted to packing lanes.

The entire system features 414 carriers delivering product to 438 chutes and 95 stackers. This allows the facility to accurately service more than 4,000 Blockbuster video stores with up to 600,000 items daily.

Click on the company name link to read more about that specific company.
* Pacific Sunwear
* Carlisle Tire & Wheel
* National Retail Systems
* Magid Glove & Safety
* New Balance
* Blockbuster Entertainment