Pick-to-light’s evolution – Supply Chain Management Review

Angelena Iglesia

Pick-to-light remains a great picking technology, but it hasn’t remained the same. That is actually a good thing, as it’s evolving to become more flexible. Providers of light-directed solutions say the technology is no longer necessarily hardwired to shelf cubbies or used only for order picking. Light-directed solutions are also […]

Pick-to-light remains a great picking technology, but it hasn’t remained the same. That is actually a good thing, as it’s evolving to become more flexible.

Providers of light-directed solutions say the technology is no longer necessarily hardwired to shelf cubbies or used only for order picking. Light-directed solutions are also being paired with other technologies like wearable scanners—or can be augmented by voice.

What has remained consistent with pick-to-light and put-to-light systems is their efficiency in processing small, e-commerce sized orders. That keeps lights highly relevant, given that e-commerce has grown at close to 15% per year in recent years.

According to analysis by Adobe Systems, e-commerce shopping levels during Covid-19 (April to May 2020) were 7% higher than e-commerce during the 2019 holiday season. That’s a lot of small items to sort, pick and pack.

“Internet orders tend to average around 1.2 units per order, so it takes a lot of labor to fill those small orders if you don’t do some unique things with your automation,” says Dave Remsing, vice president of market development for Matthews Automation Solutions, a leading provider of pick-to-light systems under its Lightning Pick brand.

A traditional pick-to-light solution uses lights on a shelf or rack position to indicate to warehouse associates which item to pick from a location, or in an order consolidation application the item to “put” to a cubby location.

The systems work well for stock keeping units (SKUs) that are relatively small and fast moving, with pick-to-light mounted in a powered communication bus channel on shelving, carton flow rack, or even pallet positions to create an effective method to accurately pick a high volume of goods.

As with any warehouse automation choice, however, lights must be right for the job, advises Dan Hanrahan, CEO of Numina Group, a warehouse automation and warehouse execution system (WES) software provider.

“When examining and selecting picking methods, the first thing we do is dig into the application, the order volume profile data, and then we analyze the SKU velocity,” says Hanrahan. “With pick-to-light, the highest velocity SKUs are best suited to lights. That way, you can really reduce the walk time and have a high density of SKUs picked at once, so an operator using pick-to-light can perform at an average pick rate of 350 to 400 lines per hour.”

Some items in a distribution center are too big or slow-moving to work well in a pick-to-light zone, so other methods such as a batch picking with a cart using a wearable, wireless computer, or perhaps automated storage and retrieval (AS/RS) is better suited. “In today’s DC environments, it’s often a mix of methods and picking processes that provide the best performance,” says Hanrahan. “Voice picking blended with pick-to-light and mobile bar code terminals are in use with most of the pick-to-light or put-to-light order consolidation and picking solutions we’ve implemented the last few years.”

Lights plus other tech

A recent project where Numina provided pick-to-light, adds Hanrahan, is at United Medco, a direct-to-consumer medical supplier. The solution’s software brings together order items from multiple areas together at pack out.

A pick-to-light system handles most of the DC’s SKUs, but for oversized and slower-moving items, a secondary pick process is used, done with mobile handheld or paper-based picking. Any goods from this secondary process can then be consolidated with items picked from the pick-to-light zone at the DC’s pack out area.

Many of Numina’s pick-to-light deployments also involve the use of wearable bar code scanners and rugged mobile terminals that are worn by the warehouse associate, allowing the workers doing light-directed work to very quickly scan a bar code for serial tracking, or in a put-to-light application, scan a physical bar code at a put-wall cubby to scan and confirm product placement and trigger the acknowledgment display light.

“By building hands-free scanning into the process, you can maintain the speed advantages of pick-to-light, while incorporating an extra level of validation,” says Hanrahan.

About half of Numina’s deployments of its pick-to-light solution are put-to-light order consolidation applications. A put wall or put-to-light system, explains Hanrahan, is typically used when wave picking across multiple zones. Orders that are picked complete within a zone can go direct to packing, while the remaining picks that require items from multiple zones are directed to an order consolation put wall. The operators at a put wall typically scan each incoming tote and or SKU bar code to energize the displays and lights for directing the sorting of items to assigned order cubby positions.

Importantly, adds Hanrahan, the back side of the put wall can have a display that indicates when the order is complete, and the size carton or poly bag needed for packing. “Put walls are popular and efficient in that they can really integrate and balance the picking and packing process for DCs using wave-based, zone picking processes,” says Hanrahan.

Lights can also be used to speed up and provide greater accuracy at an in-line pack workstation, adds Hanrahan. In DCs that support direct-to-consumer e-commerce, coupons, product samples, marketing literature, or other documents often need to be added to the specific customer carton. A light-directed, pack out shelf can hold these materials and lights at each position to rapidly direct the worker to see which materials to grab and place into a customer package.

“It’s pick-to-light being used to support customer experience and improve the level of customer satisfaction with the packaging,” says Hanrahan. “By making the pack process fast and highly accurate, it also adds marketing value add to the packing process.”

Pick-to-light is improving in various ways to gain more effectiveness, says Remsing. One new feature that is becoming popular is the use of LED lights that illuminate an entire cubby on a pick wall, rather than just the light display bar. “That increases the visibility and makes things more productive and more accurate,” says Remsing.

In put-to-light applications, some large deployments with many put walls are now “decoupling” the putting operation on upstream side of the wall with the unloading and pack out steps on the back side of the wall by using rolling, moveable put wall sections. This avoids the problem of one side of the wall getting ahead of the other.

For instance, with a moveable wall, if the operator on the loading/putting side finishes up well before the operator on the other side, the wall can be quickly detached and moved to a pack out area for processing, allowing that putting operator to continue to work at top speed rather than having to wait for unloading operator to catch up. “Decoupled, mobile put walls allow an operation to do a much better job of balancing the workflows,” says Remsing.

Cloud-based deployment of pick-to-light software also is now possible, says Remsing. “It’s not super popular yet, but we expect growth in this option as an operation doesn’t have to maintain a server on the site,” he says.

Overall, pick-to-light is being deployed in more varied and mobile ways, says Remsing. Sometimes pick-to-light is being used to do replenishment for kitting or another downstream process, or put walls are being used in combination with other forms of automation, such as an AS/RS.

And rather than always using fixed walls, some operations are using light-directed picking carts or sleds, combined with pick lights on racking, to process small orders. “These hybrid type systems are gaining in popularity because they allow more flexibility in processing small orders,” says Remsing.

Wireless IoT displays

Another change with pick-to-light systems is the availability of Cloud display devices that can perform the light direction role, but without the need to be hardwired to a power source or communicating to an on-premise software, says Trevor Blumenau, CEO at Voodoo Robotics, a vendor of Cloud display devices.

Voodoo’s devices are wirelessly controlled using standard web protocols to communicate with a warehouse management or an enterprise resource planning system that manages the inventory for a DC. The devices light up in one of six colors, and display up to five lines of custom text, such as the SKU, the quantity to pick, or the order picker’s name. The devices can even play a custom tune for each order picker. Voodoo also provides small router units, allowing the wireless display devices to be placed and used very flexibly in a DC.

“Cloud display devices are revolutionary because they are changing up the way our customers can deploy light devices, the range of uses for them, and the economics of deploying them,” says Blumenau. “They can be deployed and adapted in a very flexible manner because there is no hard wiring. It is easy to change the devices and their applications, which is perfect for third-party logistics (3PL) operations or other operations that change up their inventories often.”

While some DCs use Voodoo’s Cloud display devices for pick-to-light on mobile shelves, the small modules can easily be attached to pallets, racks or other locations in a DC. Some users are even leveraging the devices for purposes other than pick- or put-to-light, such as one DC that has placed them on dock door bays, so when a truck shows up to load or unload, the appropriate bay door lights up and the trucker always knows which bay to use.

Devices can also be attached to a forklift and light up for validation, instructions or tasks, or used at a kitting location to enable light-directed kitting.

“We aren’t just a pick-to-light system provider as much as we’ve invented a flexible platform for operations to use for their own custom functionality, whether that is pick-to-light, put-to-light, or some other function they need,” says Blumenau.

The wireless Cloud devices tap into backend software for inventory and warehouse orders using simple web URLs or REST APIs, says Blumenau. The REST APIs, he adds, are an easy way to present needed functions to the devices, such as showing a bar code on the device display that operators can scan to execute serial tracking functions. “We seek to give customers the ability to control their own destiny by giving them the tools they need to interact with the Cloud display device and customize it to their workflow needs,” he says.

Improving the proven

Pick-to-light systems are a proven method, but that doesn’t mean they can’t be improved. Jason Franklin, a senior offering manager with warehouse automation software and systems provider Honeywell Integrated, says one trend to keep on eye is combining other order-picking technologies such as voice-directed solutions with lights.

The key to this “mixed mode” potential is having warehouse execution system (WES) layer software that is smart enough to abstract a needed action, like “pick an item” and flexibly have the action carried out by the appropriate technology.

“From an innovation standpoint, we are looking at how can we potentially combine tools to capture the benefits of each, in what you could term mixed-mode order fulfillment, something like a combination of lights and voice,” says Franklin.


A traditional pick-to-light solution uses lights on a shelf or rack position to indicate to warehouse associates which item to pick from a location, or in an order consolidation application the item to “put” to a cubby location.


The management software for a mixed mode approach, adds Franklin, would look at the process as a series of tasks that need to happen, like pick an item, or put/place an item, or capture information about an item, and then call on the appropriate business logic for the picking solution, whether that be lights or voice. While this mixed-mode approach is not adopted by customers, Franklin says Honeywell Intelligrated software supports it. The benefit, he adds, is that it can blend the best aspects of lights, like speed and simplicity, with strong aspects of voice, such as high accuracy and the ability to flexibly manage exceptions. “We’re saying that by combining modes you could address the deficiencies of one mode through use of the other,” he says.

Covid-19 and social distancing best practices also are influencing innovation with pick-to-light, adds Franklin. One development to watch is touchless confirmation lights on displays, in which rather than physically touching a button on the light display to confirm an action, the worker breaks a beam of light to actuate the confirmation. That makes the process cleaner, with less chance of germ spread.

Another use of lights that supports social distancing while also efficiently filling direct to consumer orders in sectors like grocery of health products is light-based carts. Franklin says that mobile picking carts with lights can allow one worker to efficiency pick customer orders directly to a carton or tote.

The solution suits low-velocity items and distant break-pack picking areas, while lending itself to consumer demand trends such as online orders for grocery, wellness products or healthcare products.

“In some cases, a mobile cart with lights allows the operation to save a step, because the operator is building directly to an order container in the cart, rather than having to consolidate items back later on,” says Franklin.

To increase the adaptability of light deployments, other trends to watch include lights that are battery powered, as well as light setups that have expandable cubbies with moveable dividers to accommodate more goods. Another development is “lights-as-a-service” arrangements with vendors, says Franklin. “The trend with lights isn’t so much a brand-new development, but in areas like combining modes, and overcoming some of the deficiencies with how lights have been deployed,” says Franklin.

Though not limited to picking, another development is augmented reality (AR) picking in which the operator would wear smart glasses that would display any needed visual cues. While AR technology could be leveraged to create a virtual put wall, it can also be used for other reasons such as cycle counting or put away, explains Will Tritle, a logistics consultant with Bastian Solutions, a warehouse automation and software provider.

“AR provides that visual cue aspect, but instead of one device at each location, the glasses worn by the operator provide the visual cues for every needed location,” says Tritle. “AR has many capabilities, but generally, it’s more complex and requires more operator training than pick-to-light.”

The key trend, adds Tritle, is integrating lights with automation such as goods-to-person systems, whereby an operator could perform batch picks, with the needed inventory presented by the automation, and the put actions to select inventory into multiple customer order containers facilitated by light displays. This leveraging of light technology, adds Tritle, requires software integration between the lights and the automation, but carries the same simplicity and speed benefits as traditional pick-to-light set ups.

“The biggest trend going forward is probably combining pick-to-light with these automated systems,” says Tritle. “With lights, the key benefits are speed and simplicity. All that an operator has to do is scan a pick order, or a carton, and that lights up all the locations and all the quantities so the operator can see what needs to be done. I don’t think it gets any simpler than that from a picking perspective.”

Companies mentioned in this article:

Bastian Solutions
Honeywell Intelligrated
Matthews Automation Solutions
Numina Group
Voodoo Robotics

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