Light-directed activities: Order fulfillment at the speed you need

Rooted in increasingly complex software, the concept of pick-to-light has moved well beyond the pick and is now capable of relaying an array of information to workers throughout the fulfillment process.

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Ten years ago, most cell phones had single-color displays, and they were primarily used to make phone calls. Now glance at the phone in your pocket, think about its capabilities beyond dialing a number, and you will have some sense of the transformation of light-directed order fulfillment technology over the last decade. Whether stationary or cart-based, approaches such as pick-to-light, put-to-light, pack-to-light, pick-to-screen, and dozens of other variations are enabling radically different product flow through a facility.

“There is a level of creativity that now exists,” says Chris Castaldi, manager of business development for W&H Systems. “Before, there was the specific process of pick-to-light and essentially one way that it worked. Now we can decide how to get the best value out of lights in a variety of applications.”

Although a potentially transformational technology, not all successful light-directed applications require extensive reworking of existing fulfillment processes, says Ken Ruehrdanz, manager of the distribution systems market for Dematic.

The best solutions follow a crawl, walk, run progression with lights deployed to address specific stock keeping unit (SKU) profiles and bottlenecks. Mobile light-enabled carts and put walls for order consolidation can be targeted to improve speed and accuracy at any step in a picking application. Both upstream and downstream of the pick, light-directed technology can take the guesswork out of fast and precise product movement.

Pick-to-light and goods-to-person
If light technology is intended to increase the speed with which a picker locates and places each item, it follows that the best way to keep the picker productive is to keep them picking, not walking. Castaldi suggests that light-directed picking “is a game of seconds, which turn into minutes, hours and dollars.” Therefore, goods-to-person technology is an increasingly fundamental practice to effective light-picking solutions.

“Things can be slightly random in a pick-to-light environment,” says Gary Cash, vice president of design services for Wynright. “Even if lights are activated in sequence, these setups might still place a burden on the operator to determine the most efficient path. With goods-to-person, I can determine exactly what sequence in which I want to present product to the picker.”

Carousels, for example, are a natural fit for light-directed technology. In fact, George Fiorentino, East Coast director of sales and business development for Sapient Automation, says, “I don’t sell a single carousel or vertical lift module (VLM) for picking that doesn’t include light direction of some kind.”

In some carousel applications, the takeaway conveyor—located behind the worker as he faces the carousel—can be supplemented with flow rack locations above and below. “When the operator begins an order, he immediately has fast-moving items to pick from light-directed flow rack as the carousels present the next item,” says Fiorentino.

Bringing goods to the picker can boost that person’s productivity, but it can also impact the facility’s overall approach to storage and inventory, according to Kevin Reader, senior account executive with System Logistics. Typically, the speed of light-directed technology and the ability to address more than one order at a time make it suited to high-volume items.

“With goods-to-person, you could address the slow movers in the same space as fast movers and conceivably combine and collapse reserve storage and primary storage into one medium,” Reader says. “That can make for a much more efficient, waveless warehouse, with sustained picking rates of 600 lines per hour. I think that’s a real game-changer.”

Put-to-light and the put wall
Whether fed by manual batch pickers or an automated storage and retrieval system (AS/RS), setups where SKUs are in motion and orders stay in place lend themselves to put-to-light technology. At its most basic, a put-to-light approach delivers a carton or tote of a single SKU to a stationary operator who picks what he needs for active orders. Depending on the average line count and cube of those orders, an operator might be picking from a single SKU to a dozen or so simultaneous order locations, each with its own light bar, or with one screen directing all orders.

At the other end of the order cube spectrum, the customer might benefit from a put wall, a series of open-ended cubbies housing 50 or more dynamic order locations. Lights on the backside of the put wall alert the packer when each order is complete. Light prompts on the packer’s takeaway conveyor might indicate the appropriate size box for the order, says Castaldi, while allowing final weighing and freight rate shopping to occur just moments before the package leaves the building. The packers’ lights might also direct them to include various promotional material or other value-added items.

Because they are effective in a range of process steps, lights can either facilitate dramatic change in product flow or slow, incremental change in a facility. A light-directed pick station, put wall or mobile light-enabled pick cart can be folded into the current picking process to better address certain SKU and order profiles. Lights have also evolved and expanded alongside voice-directed technology. “It was thought that perhaps voice would replace lights, but in actuality, voice complements lights and allows more applications for both technologies,” says Dematic’s Ruehrdanz.

For example, in a traditional carton-to-store, pick-to-voice environment, a relatively small area of floor space could be designated for a light-directed put wall. A voice or light-directed pick cart might make a pass through the warehouse and fill a number of totes with SKUs for multiple orders before depositing them at the put wall for consolidation.

Consolidation and decoupling
The concept of order consolidation is rooted in the decoupling of steps in the order fulfillment process. In traditional batch picking, a single person is usually responsible for an entire order, and their paths through a warehouse will reflect that. Light technology’s emphasis on speed and accuracy means it can be deployed in targeted areas of a process as needed, allowing a batch picker to fulfill some or most of an order before a worker at a put wall completes or consolidates it. By enabling a fast and accurate means of sortation, light can also allow for added process steps while reducing the likelihood of error.

For instance, Todd Sherbinow, senior product manager for Lightning Pick Technologies, a Matthews International Company, has a customer who performs value-added services to items. The customer stocks several hundred SKUs of base product, which can become many thousands of SKUs as they become customized. The warehouse management system (WMS) will batch 10 direct-to-consumer orders, which are picked by light. Those batches are then sub-batched by workflow, with one group sent to stamping, one to embroidering, and one that stays generic. Then they are driven back to a light-directed put wall station for consolidation.

“Mass customization and speed are the key business drivers,” says Sherbinow. “They try to offer that sort of personalization and still maintain same-day ship objectives.”

Although light can be brought to product as needed, Wynright’s Cash says the placement of inventory at the outset should be shaped according to the capabilities of the light hardware. “The key to making these products successful is to move your SKUs around and get the right SKUs in front of the right technology,” he says. “If your slow-movers are in front of pick-to-light, it will not be successful.”

The light-directed order-filler
The picking rates of a stationary, light-directed order filler will be hard to beat. Although a goods-to-person system might be simple and low-cost or require significant capital investment and be highly automated, it’s not for every application. The zone-based pick module, a staple of traditional pick-to-light applications, has not escaped change as light hardware has evolved. With multicolored lights, what were once rigidly defined zones can now be shared by neighboring workers, or staffed by as many employees as is necessary to address spikes in volume.

“If the size of the zones can be flexed in real time, this gives you the ability to do true bucket brigade-type fulfillment,” says Lance Reese, director of technical solutions, order fulfillment for Intelligrated. Reese also highlights the concept of the “next best task,” where depending on order volume a picker might be directed to pack an order out, perform replenishment, or conduct a cycle count. “Light-directed order-fillers are now empowered to control the areas in which they work,” says Reese.

Each order or order filler might be assigned a color, and if one SKU’s light bar is capable of signaling picks to more than one color, the number of SKU locations has effectively doubled. Taking the concept of accountability one step further, some systems might even have a wrist-mounted RFID tag that can identify the person who extinguishes a light when the person’s hand is in proximity. Additionally, light software might direct the order conveyor to “follow” the operator as he or she moves through a zone.

Each worker can also be made more productive by light bars that span an entire shelf, as opposed to lights placed at 1-foot intervals designating fixed product lanes. The lights can dynamically indicate flexible SKU locations, maximizing SKUs per shelf and minimizing worker travel time to each item.

“In the past, the idea of changing every bar code label and light bar to accommodate changing SKU mixes was an opportunity for errors,” says Reese, who says such adjustments were painful when done quarterly, much less in real time. “Now there are light devices that can be used on the back side of the shelf to inform replenishment to match the dynamic shelf bars on the pick side.”

Typically in pick-to-light, the operator doesn’t have an opportunity to signal a replenishment, other than the occasional short. “Now, you can be a little more proactive,” says Cash. “Ideally, you will never see a short, whereas in older systems it would be all too common. Or, to avoid it, replenishment might consist of someone roaming around the rear side of the flow racks looking for low SKUs without any real guidance.”

Real-time orientation
From its roots in monochromatic, alphanumeric displays, light technology has come a long way. But each additional color and each additional layer of data communicated to the worker requires an exponential increase in software complexity. And since light picking is all about speed, real-time orientation is essential. Although not every customer’s order profiles are ideal for pick-to-light, System Logistics’ Reader argues most will benefit from systems with real-time capabilities.

“Real-time data and order-management is no longer a driver, it’s an ante,” says Reader. “Look what’s happening with the push to same-day delivery. If you can’t increase your order window until later in the day, that’s a real competitive problem.” Reader estimates that although just 25% of end users are at that level now, the number is quickly going nowhere but up.

Real-time capabilities enhance the responsiveness of zone-based pick- and put-to-light modules as well as goods-to-person stations, but it can also enhance an operation’s nimbleness throughout a facility. Cart-based light picking systems can roam into voice-pick areas, and vice versa, to respond to hot orders, rush orders or one-off orders in a concept Sherbinow calls “overlay.” And if the cart operator can accept new orders in real time, then the worker who happens to be in front of the SKU at the right time can grab it while he’s there.

Any overlay of light, voice, or any other picking technology demands robust software. Sherbinow is careful to emphasize the importance of deploying light technology on a common platform with other order fulfillment systems. “Smooth interoperability is rarely achieved by light software that must communicate with independent voice and WMS software, for instance,” says Sherbinow, who says light-directed software platforms might also include some level of conveyor control and labor management. “If everything works on the same database and platform, the customer has a single point of interface. As order waves come to the software, it manages the technology in different areas, but it all appears the same to the end user.”

Companies mentioned in this article
Lightning Pick:
Kardex Remstar:
Sapient Automation:
System Logistics:
W&H Systems:

About the Author

Josh Bond, Senior Editor
Josh Bond is Senior Editor for Modern, and was formerly Modern’s lift truck columnist and associate editor. He has a degree in Journalism from Keene State College and has studied business management at Franklin Pierce University.

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From the December 2017 Modern Materials Handling Issue
Confronting an aging materials handling system and new channels of business with new customer expectations, Rocky Brands installed a put-to-light and sortation system to ramp up fulfillment.
The Big Picture: Navigation Gets a Reboot for Automatic Vehicles
Top 20 3PL Warehouses 2017: Growth amid change
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