March 19, 2010
Column | techwatch

Should you let your equipment do the walking?

"Goods to person" picking systems that deliver items to workers can boost pick rates as high as 1,000 lines per hour, say suppliers.

By James A. Cooke

For years, distribution consultants have labored to find ways to reduce travel time in the warehouse operation. Traditionally, that's meant designing distribution center layouts to minimize the distance order pickers had to walk to retrieve items from storage. Common sense dictates that the less time workers spend traveling, the more time they'll have for order picking and the more productive they'll be.

But there's another way to increase picking productivity. Instead of merely reducing travel distances, some companies are opting to eliminate travel time altogether. They're doing this by using automated material handling equipment to deliver items to order pickers who remain in a fixed spot. It's a concept dubbed "goods to person," and a number of material handling equipment manufacturers are touting it as a way to improve warehouse productivity.

Goods-to-person order picking isn't a new concept. Consultant John Hill of TranSystems says the idea has been around since the late 1960s under various names, including "goods to picker." But the concept is attracting renewed interest today as more distribution operations grapple with the challenges of picking individual items, or "eaches," instead of full cases or pallets.

As for the equipment used in goods-to-person picking systems, there are a number of options. For example, some companies use automated storage and retrieval systems (AS/RS) with shuttles to deliver goods to workers. In this type of application, the automated storage and retrieval system uses cranes and conveyance vehicles to remove pallets, totes, or bins from storage racks and deliver them to a station at the end of an aisle. Once the containers arrive at the station, a worker retrieves the items needed and deposits them into the appropriate boxes or totes to fill customers' orders. Automated storage and retrieval systems designed for goods-to-person picking are available from such well-known vendors as Dematic, HK Systems, Knapp Logistics and Automation, and Witron Integrated Logistics.

Another option is to use carousels in conjunction with automatic extractors. Under this approach, the carousel spins to where the desired container is stored and presents it to the automatic extractor. The extractor, which resembles an elevator, then pulls the container from the carousel and deposits it on a conveyor for transport to the pick station. One of the leading suppliers of this type of equipment is Schaefer Systems International.

Perhaps the newest variation on goods-to-person order picking involves the use of robots. With a robotic order fulfillment system, a robot carries products stored on portable shelves to an order picker. Kiva Systems is the best-known vendor of this type of technology.

No matter what type of equipment is used, computer intelligence remains critical to the successful deployment of goods-to-person picking. In fact, recent advances in software programming have taken the systems' ability to optimize the flow of items to a whole new level. Typically, this software functionality is contained in the warehouse control system (WCS), the same application that controls the automated equipment. "WCS software is the enabler that has allowed goods-to-person work stations to obtain ultra-high pick rates," explains Ken Ruehrdanz, who's a distribution and warehousing market manager at Dematic. "The WCS software allows the loads to be retrieved from the storage system and presented to the pick station in a precise sequence."

Although these systems tend to carry a high price tag, they can bring about substantial improvements in throughput. In a recently published white paper, Dematic claims that operations that adopt the goods-to-person approach can achieve pick rates of between 500 and 1,000 lines per hour. For distribution centers seeking to boost throughput in their piece picking operations, goods to person may provide just the kind of "pickup" in productivity they're looking for.


Editor's note: Dematic's white paper, "Goods to Person" Order Fulfillment, can be downloaded for free from DC Velocity's Web site. Go to http://www.dcvelocity.com/whitepapers/.

More articles by James A. Cooke

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