Goods-to-person picking: Delivering the goods
You might be able to increase productivity by turning your picking formula on its head and using automated storage, conveyance and data collection technologies to bring goods to your picker.
By Bob Trebilcock, Executive Editor -- Modern Materials Handling, 6/1/2009
For as long as there has been picking, sending a person out to get the goods has been the way to go. The concept is simple: Put the product away in storage or a pick face, and when it's time to fill an order, send a picker to that location to get the goods. Let's call that person-to-goods picking. It's a safe bet that in some ancient Egyptian tomb there's a hieroglyphic of a supervisor sending a worker to a central storage area to get the next block for the pyramids.
But person-to-goods picking isn't the only way to go. With the right order profile and volume, facilities can realize significant productivity gains by turning the tried and true picking formula on its head and employing automated storage, conveyance and data collection technologies to bring the goods to the person.
Let's call that goods-to-person picking. What kind of gains are we talking about? When it comes to slow-moving stock keeping units (SKUs), 100 picks per hour is an average rate in a conventional warehouse. A goods-to-person picking solution, on the other hand, can support sustained picking rates of 450 to 800 picks per hour, depending on the product and the system, and up to 1,000 picks per hour during a portion of a shift.
The gains in productivity come from keeping an associate in one place to do the job and then automatically delivering the items to be picked from storage. "Engineering studies show that the person picking in a conventional warehouse spends 40% to 60% of their time walking to a pick face," explains Ross Halket, director of automated systems for Schaefer Systems International Inc (704-731-1625, www.ssi-schaefer.com). "By bringing the goods to a picker at an ergonomically designed workstation, you eliminate the walking time between picks and enable more efficient picking at the point where the task is being completed."
Early adopters have been the pharmaceutical, optical, as well as the health, beauty and cosmetics industries. More recently, the systems have been finding a home in e-commerce fulfillment facilities, grocery distribution centers and retailers. One end user installed a system for kitting medical products for doctors' offices.
The common denominator in all of those examples is that the systems are used to consolidate and automate the handling of slow-moving items that get fewer than 25 to 30 picks per hour. "Those have relatively low velocity of movement, but you need a lot of space for pick faces and a lot of time is spent picking them," says Halket.
What's more, goods-to-person picking works best in an environment where there is a relatively high volume of total picks, says Ken Ruehrdanz, business development manager for Dematic (877-725-7500, www.dematic.us). "Generally, you're looking at a facility that might have to do 5,000 orders a day of one to three items," he says.
Finally, it usually involves goods that can be easily stored in a container or tote that can be efficiently conveyed to the picking station.
Meeting changing demand
In some respects, the concept of bringing the goods to a person is not new, says Tom Brady, vice president of the solutions development group at FKI Logistex (866-599-4735, www.fkilogistex.com). "Years ago, I had a client who was servicing about 150 retail stores," says Brady. "They received a truckload a day of fast-moving product. Rather than put it away, they set up a workstation at the dock where the order selectors picked right from the pallets."
While the most of the systems going in today are delivering containers, totes or individual items from a carousel or mini-load storage system to a picker, some users have adapted the concept to deliver unit loads from an automated storage and retrieval system (AS/RS) to a picking station. "We have installed solutions that deliver pallets to a workstation where an associate picks cartons to a shipping pallet," says Brady. "We have also installed solutions that use an automatic guided vehicle (AGV) or an automatic transfer car to deliver the pallets to a workstation."
Two important factors have come together to increase the interest, and affordability, of these solutions. One is the challenge of finding enough reliable labor willing to work in today's warehouses, especially as the workforce ages. "Piece picking is hard work and it's difficult to find someone willing to do that for a number of years," says Brady. "If you can make the job less strenuous on your associates, that's a good thing."
Second is that state-of-the-art warehouse control software systems (WCS) have made it possible to synchronize the automated materials handling and data collection components of a goods-to-person solution with the person doing the picking. The high picking rates deliver the return on investment that justifies installation. "We're now able, through software, to match up the storage tote with a batch of order totes and manage the material flow in a way that wasn't possible or affordable in the past," says Halket. "We're able to put together a total solution, and not just equipment with a payback in three years or less. That's the target."
Getting goods to the person
How then do these systems work? First, they are generally put together as a packaged solution that includes:
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A high-density automated storage medium, like a carousel, vertical lift module or mini- or micro-load storage system.
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A conveyor to route storage containers to and from the storage device and shipping containers to and from the workstation.
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A data collection system to direct the pickers activities and capture information about the tasks performed. Usually that is a pick-to-light system, but pickers may also be directed by voice technology or a computer screen.
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An ergonomically designed workstation that enables efficient picking, often with room for multiple shipping containers so that a picker can work on several orders simultaneously.
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A software system to tie it all together and communicate back to a warehouse control and warehouse management system.
Once a batch of orders comes down to be picked, shipping containers are automatically delivered to the workstation and scanned into a picking slot. Meanwhile, the storage system will automatically begin retrieving and conveying storage containers to the picker, who is then directed by the data collection system to pick the right quantity of items to a specific container. When the pick is complete, the storage container is automatically returned to storage and the next container slides into place. The system keeps a steady flow of containers to the picking station.
Since a goods-to-person solution is most often used to automate the picking of slow-moving items, it's generally not the only picking solution in a facility. Instead, it's part of a broader picking strategy known as an ABC strategy, with different approaches to handle the fast movers (A), the medium movers (B), and the slowest movers (C).
For the A movers, a facility might install a fully automated picking solution like an AS/RS for full-pallet orders, a mini-load system to deliver cases to an automatic palletizer, or a high-speed A-frame for fast-moving individual items, like cosmetics, books or CDs.
The B movers can be handled by an associate who is on foot or on a lift truck and is directed by RF-scanning, voice or pick-to-light. Because the associate will be picking a large number of items from a relatively small number of pick faces, travel time is reduced. The goods-to-person solution for the C movers comes last. From there, an order will go to shipping.
While a goods-to-person solution isn't right for every facility, in the right facility it can deliver significant improvements over traditional picking.
Goods-to-person picking at Smith Drug Company
Using the new system, picking productivity increased from 140 lines to nearly 900 lines per man hour.
In 2008, Smith Drug Company installed three high-speed A-frames to improve picking operations at its 244,000 square foot distribution center in Spartanburg, S.C. It is one of two facilities operated by the pharmaceutical distributor to independent pharmacies throughout the mid-south and southeastern United States.
The A-frames were designed to handle the 6,300 fastest-moving stock keeping units (SKUs) in a facility that handles about 26,000 SKUs in total, says Isaac Rogers, director of organization development at Smith Drug. Getting more efficient with its fastest-moving items, however, highlighted inefficiencies in the rest of the facility.
"We discovered that we had about 10,500 slow-moving items so we could only get about 140 lines per man hour because we had to do so much walking," says Rogers. Given Smith Drug's tight turnaround times on orders, those slow movers bogged down operations. "We deliver 70% of our orders by 10 a.m. the next day," Rogers says. "We had to find a faster way to pick our slow movers."
The solution was a goods-to-person system (Schaefer Systems International, 704-731-1625, www.ssi-schaefer.com) that stores 10,500 SKUs in just 6,600 square feet. The remaining SKUs are still picked using voice recognition technology.
How does it work? The system consists of two pick stations with four horizontal carousel pods per station, or eight carousels in total. Each pick station has seven slots for shipping totes, which allow an associate to pick seven orders at a time. Product, meanwhile, is stored in the carousels in storage totes. Each storage tote can have up to eight storage compartments.
To fill orders, pre-labeled shipping totes are conveyed from an order start area to the pick station. Based on the orders to be filled, the system automatically retrieves and conveys storage totes from the carousel to the pick station. An automatic bar code scan identifies the storage tote when it arrives at the pick station, and a computer screen tells the associate how many items to pick from that tote. A separate light bar indicates which compartment to pick from. A light barrier confirms that the associate picked from the right compartment. "If you break the wrong light barrier, the system stops you and directs you to correct it," says Rogers. The system then indicates which shipping container gets the parts.
Once the last product has been picked to a shipping tote, the system releases it and automatically conveys it to a quality control station or directly to the shipping area.
Since going live last September, Rogers says associates who once picked 140 lines per hour are now picking 800 to 900 lines per hour. In fact, it's been so successful, that Smith is implementing another system in its Valdosta, Ga., facility. "We can get a new associate up and running on the system in about 7 minutes," Rogers says. "The space we've freed up by compressing the storage area will allow us to expand our business in the future without adding more space."
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