Take Your Pick
Voice-directed or pick-to-light technology? The right choice is often a combination of both.
The hard and fast rule for deciding between voice-directed picking and pick-to-light technologies is this: There is no hard and fast rule. Companies looking to automate and modernize this critical warehousing function must consider a range of factors—from the size and scope of the facilities to the type of products and picking strategies involved. The resolution often results not in an either/or choice between the two technologies, but rather in a strategy that incorporates both.
Although manual, paper-based processes are still in play at many warehouse and distribution centers, the picking function is increasingly a candidate for automation in light of companies' continued struggle to cap, if not reduce, operating expenses. With customer retention a priority, particularly in a challenging economic climate, organizations are doing all they can to bolster customer service. That means putting in place an infrastructure that ensures the right products expediently get to the right customers.
That level of order accuracy isn't possible with paper-based processes, contends John Casagrande, vice president of client services at Voxware, a Hamilton, N.J.-based provider of voice-directed picking technology.
"Companies still using paper picking processes often incur high order checking and auditing costs," he explains. "That's just additional overhead, not to mention the rework when a product needs to be repacked or put back.
"Paper-based processes can be relatively fast, depending on the situation. They can be decent from a productivity standpoint. But they always suffer from an accuracy standpoint," Casagrande adds.
Addressing the challenge by adding more people to the picking operation isn't the most cost-effective solution for improving accuracy or increasing order-processing speed.
"Companies with manual environments add labor to increase throughput, but that simply balloons the cost," Casagrande says. "As companies with labor-intensive environments or complicated picking strategies evaluate their operations, they look for solutions that provide the flexibility to improve throughput while reducing labor costs."
Picking Technologies at Work
Those solutions come in the form of two different picking strategies—the more established pick-to-light capabilities and voice-directed picking, which has gathered steam over the past few years and has greatly matured from a technology standpoint. Both solutions promise significant benefits over paper-based picking processes, including increased worker productivity and fewer picking errors. Picking accuracy can be improved to up to 99.98-percent levels, while individual operator productivity can be boosted upwards of five times over what's possible with traditional manual picking solutions, according to independent studies and technology vendors.
Pick-to-light systems, which have become a staple in distribution centers and warehouses over the past several decades, promote efficiency via the use of lights to direct picking activity. The flashing light displays are mounted on shelving units, case flow, and storage racks -- or on machines such as vertical shuttles and carousels -- to direct workers to the items and quantities they need to pick, and where they need to physically place the picked materials.
In a typical pick-to-light operation, the warehouse management software or master materials management package issues a set of orders, and the pick-to-light subsystem determines the optimal picking sequence for each. Next, it transmits a signal to the light modules on the equipment, which then display a set of directions to guide individual operators in their picking tasks. The header display unit provides detailed data on pick quantity and the specific carton or tote to place the product. When finished, the operator presses a button on the light display to confirm the pick task is complete, and the software verifies that the correct item or items have been picked.
In comparison, voice-directed picking employs standard mobile devices or a small voice-supported terminal, along with headsets equipped with microphones to keep operators' hands and eyes free as they go about their picking tasks. Unlike RF scanners, pick-to-light systems, or even paper-based processes, which require the operator to read, scan, or punch keys to orchestrate a pick, operators using voice-directed solutions receive picking instructions through the headset, which communicates with the host system via a wireless connection to retrieve and issue its command sequences.
Similar to pick-to-light systems, voice solutions interface with a host warehouse management system (WMS) or enterprise resource planning (ERP) system, which create and deliver the picking assignments. After workers securely sign on to the voice solution, they receive their individual picking instructions via easy-to-understand voice prompts as to where to go, how much to pick, and where to physically place products as part of the order.
One advantage of a voice solution is the interactive dialogue and use of check-digits—a code the picking operator uses to acknowledge a specific instruction, such as how many items were picked, or that the right products were picked based on a set of numbers pulled off the pallet or location.
The Good, the Bad, the Ugly
For years, the relative immaturity of speech-recognition technology, and the fact that many early voice-picking systems primarily voice-enabled existing paper or RF-based workflows, gave pick-to-light technology an edge. But now that both technologies have evolved, the question remains: Which performs better and how should organizations choose between them?
The answer is that both technologies have key strengths and weaknesses, and along with price and flexibility considerations, the choice boils down to a handful of guidelines that can direct companies to the technology that best matches their requirements.
Consider pick-to-light systems, which are long recognized as the fastest technology because of the simple and direct way that they guide workers through pick tasks. Pick-to-light is often the preferred method of automation for high-density picking environments, which move lots of smaller products, and where the picking area or zone is very small with little movement or travel time to fulfill orders.
Pick-to-light also makes sense in warehouses or distribution centers that have lower SKU counts, primarily because a smaller environment helps keep costs in check as the price of pick-to-light is directly tied to the number of SKUs because lights have to be physically installed on every rack and pick location.
"Companies typically use pick-to-light where a lot of product is packed into a condensed area with mezzanines and flow racks," says Chris Wappler, senior business development manager for voice solutions at Bellingham, Wash.-based Peak-Ryzex, a systems integrator specializing in supply chain and mobile workforce implementations. "Lights are priced and implemented per SKU, whereas voice is priced and implemented per operator.
"For a warehouse with 100 or fewer SKUs, a company has to buy only 100 lights. But, for a warehouse with 20,000 SKUs, and 20 to 30 pickers, the pricing model for voice is much better," he adds.
MWPVL International, a Montreal-based global supply chain and logistics consulting company, takes the math further. Its guidelines for a pick-to-light solution are to budget between $50,000 and $100,000 for fixed overhead costs, including system installation, software integration, and the computers and scanners. The budget also includes $100 to $130 for each pick location, which covers the cost of an LED light display and a header display for each flow rack. With those figures in mind, costs for pick-to-light installations can range upwards of $300,000, depending on the warehouse or DC installation, estimates MWPVL President Marc Walfraat.
Comparatively, a voice-directed picking solution for 25 users might range from $188,000 to $280,000—a cost that covers the RF network, server, and mobile hardware and software, as well as professional services, Walfraat says.
In addition to the cost comparison, speed is also a factor in the technology decision. While pick-to-light has traditionally held a cost advantage, improvements to voice technology have leveled that playing field.
"Whether lights or voice is faster depends on the environment," says Richard Stewart, principal of Vitech Business Group, a supply chain integration firm based in Bellingham, Wash. "Advocates of light technology say light is faster because it removes the time it takes the brain to translate a spoken word or visual location and associate it with the actual spot where operators move their hands. Voice advocates claim voice is faster because operators are not slowed down by having to push a button to confirm the pick.
"The truth is, both systems are so close in speed, it really depends on how the pick is measured, the actual environment, the travel time, and the units per grab," Stewart says.
Let's Get Flexible
Compared to pick-to-light technology, voice typically wins out in terms of flexibility. Voice solutions support multiple picking styles -- including case picking, piece picking, and cluster picking—and can also be deployed for other warehouse tasks such as receiving/putaway, replenishment, and shipping.
"Voice systems provide more flexibility than light systems," says Jennifer Lachenman, vice president of product strategy at Wexford, Pa.-based Lucas Systems, a voice-directed technology vendor. "When SKUs, or the location of SKUs change, voice allows greater flexibility, compared to a hard-wired pick-to-light system."
Voice technology's promise of hands- and eyes-free picking also affects flexibility. "Because workers are directed by voice, they can keep their eyes on their surroundings and that plays a big part in warehouse safety," Lachenman explains. "By contrast, pick-to-light instructions are displayed on an LED on a piece of equipment, so workers have to remember which display refers to which product they are working on. Voice takes the pressure off and it's a natural way to interface with a host system."
The bottom line: Sometimes there's a clear choice between the two picking technologies, but often the optimal solution is to deploy some combination of both, depending on the warehouse or distribution center environment. In either case, the project presents both cultural and operational changes, so management needs to put the proper programs in place to ensure workers are on board.
"Management needs to start educating the workforce early to help alleviate apprehension and create excitement," says Wappler. "Companies that don't spend time preparing the workforce for change will find people pushing back."