Burger King’s advertising jingle during the 1970s was, “Hold the pickles, hold the lettuce. Special orders don’t upset us. All we ask is that you let us serve it your way!”

In late August, Sarah E. Needleman profiled in the Wall Street Journal that entrepreneurial manufacturers are experiencing a demand for made-to-order goods. In her feature titled, “‘Custom’ is Customary,” Needleman hop-scotches through a variety of businesses from Create-a-mattress.com to Panraven, a 3-year-old customer photo-scrapbooking business.

Along with these customized products and one-at-a-time customer orders comes not only the opportunity for increased profit margin but also the potential for dissatisfied clients if the fulfillment process is lacking or mispicked. Returned materials, and the corrective actions and express shipping that result, can consume all the profit-margin benefits of a customer build-to-order operation.

The newest development in supply-chain efficiency techniques and tools is “build to light,” used by build-to-order and assemble-to-order manufacturers. Build to light is the latest generation of what is commonly referred to as “pick to light,” a light-directed, error-proofing system that reduces errors within critical procedures such as parts picking, kitting, assembly, and sequencing, among others. Pick-to-light systems have been around for more than 30 years. Lights mounted on workstations, bin shelving, or other material storage media direct operators to the correct parts, quantities, and sequences to execute their task with greater accuracy than paper-based methods.

However, with the increasing demand for customizable manufacturing throughout the supply chain, a newer pick-to-light technology is needed, one that can pioneer the next generation of cost-effective picking solutions. Build to light is that technology.

Light-directed order selection

A typical light-directed order selection system—whether a pick-to-light or a build-to-light system—uses light indicator modules mounted to shelving, flow rack, work benches, pallet rack, or other storage locations. A track-lighting style of duct is mounted to the front of the shelf. Light modules are placed within the duct underneath each product or part location. As you can see in the photo below, a dome light shows the operator which parts on the shelf are needed for the order. At each pick location there is also a quantity display telling the operator how many pieces of that specific item to pick. Whenever product is needed from a specific location, that particular indicator turns on, drawing attention where action is required. The operator picks the product quantity displayed and then confirms the pick by pressing the lighted button.

Difference between pick-to-light and build-to-light

For the past 25 years, traditional pick-to-light systems have been primarily used in logistics operations and distribution centers. As we see the technology migrate into the manufacturing market for error proofing of assembly operations (what we call a build-to-light system), there are a number of different challenges the technology will face. Vendors that attempt to apply the same pick-to-light products and packages which worked well in the logistics operations may struggle in adapting to these new manufacturing challenges. What are some of the differences?

Pick-to-light systems in logistics are generally applied to lines where a number of operators (pickers) fill the orders. Each order is different because it is based upon which of the many products the logistics center stocks that the end-customer chose to buy. The pickers work as a team, passing order containers down the line. Each picker’s job is roughly the same: pull product from stock and place it in the order container. Although pickers may have some secondary tasks such as applying price labels, their primary task is the picking activity. In most cases, it is unimportant what sequence the stock is placed into the order container provided that, by the end of the line, everything the customer ordered is in the container.

Comparing this with an assembly operation where a pick-to-light system is employed for error proofing points up a number of differences. First, the primary role of the operator is not picking the components. It is assembling the final product. If a pick-to-light system is to be used, it must be integrated into the assembly process. Unlike order filling, where sequence is typically unimportant, in assembly, sequence is essential. As a result, to be successful, the new build-to-light system must allow the process owner to have much greater control over the sequence for any given final product.

In stark contrast to warehousing operations where what is picked for any order is somewhat random based on what the customer ordered, assembly operations are driven by what is being built. Every time a specific final assembly is built, the same parts will be needed and the same sequence will be followed. As a result, assembly systems tend to be bill of materials-focused as opposed to order-focused. Even customized, short-run assembly work orders are expected to follow specific instructions for specific parts.

Assembly operations are focused on the work-cell concept, which is not typically used in logistic-order picking. Cells may differ a great deal from each other based on what operations are being done. As a result of this work, cell-focus process engineers choosing to apply build-to-light technology will frequently “prototype” the technology in one or two work cells to get experience and gain confidence in the technology. To be effective, the build-to-light systems must accommodate this desire for engineers to start small and grow their own systems. The scalability of the build-to-light method is one of its most inherent differences and advantages.

Another aspect of this work-cell differentiation is that mounting build-to-light hardware in assembly operations can vary widely. Unlike logistics operations, which typically use a fairly uniform “rack” to hold the items that are being picked, in assembly work cells, the assembly form is often unique to function. There is extensive use of tubular racks to build modular workstations. The individual build-to-light modules must accommodate these mounting variations. The build-to-light approach must offer a wide range of flexible deployment options to succeed.

During the past quarter century, one provider of build-to-light solutions, Lightning Pick Technologies, has helped many companies progress from error-prone manual material handling methodologies to more accurate light-directed processes by applying pick-to-light or build-to-light methods as best suited to the end-users’ specific application requirements. “We have collected data from many of these projects to effectively compare the productivity and accuracy of the two approaches,” says Bernie McCabe, a senior executive with Lightning Pick.

Needleman accurately notes that custom goods tend to be more time-consuming and expensive to put together than ready-made items. Growth in custom manufacturing processing is putting a greater strain on quality control. The technology response to these build-to-order products and services will dictate that build-to-light solutions are used to mitigate costly manufacturing mistakes.

Conclusion

As good and useful as legacy pick-to-light systems have been during the past 30 years, there have been many breakthroughs in today’s light-directed order-fulfillment technologies that differentiate them from their legacy counterparts. These new solutions offer cable-free light module hardware for greater ease in system installation, expansion, reslotting, and maintenance. More important, they also feature progressive software tools for better management of light-directed picking operations and improved visibility into the productivity of their pick process.