There's no question GE Lighting Systems knows how to build lighting equipment at its Hendersonville, N.C. manufacturing plant. After all, it has been doing just that since the early 1950s. But just getting the job done was no longer sufficient. It now has to be done to Six Sigma quality levels, which require that operational inefficiencies be eliminated.

Management at the plant determined that its best approach to operations was demand flow technology (DFT) – a method of building to actual customer demand rather than to forecasts. It backed this approach up with a $2.2 million investment in equipment which included a complete overhaul of materials handling operations on the 800,000 square foot shop floor.

The company now builds high-intensity discharge (HID) lighting for utility companies, GE distributors, major retailers and others on a completely upgraded system that features 10 assembly lines. Furthermore, the entire manufacturing process has been overhauled. To support that conveyors and work carts feed work-in-process to workstations. An automated data collection system provides real-time analysis and performance reports. In addition, lift trucks that operate in the plant have been outfitted with wireless laptops, eliminating a paper-based system that was untimely and inaccurate.

The end result is a $1.6 million annualized saving in plant costs. "The payback of this system is huge," says David Smith, a Six Sigma master black belt (see sidebar - Making Six Sigma a Reality - below for an explanation of titles).

While operations had run relatively smoothly for many decades in Hendersonville, GE knew that change was in order. Operations were behind the times, and the materials handling equipment needed modernization to fit the new approach. "Our main assembly equipment was standard, belt-driven conveyors with variable speed motors," says Smith. "The system continuously moved and we placed our people around it."

The lines were organized in a front-to-back assembly sequence. Each worker had the control to stop the line if that person fell behind. Once the line came to a halt, other employees could help that person catch up, but still others sat and waited. In all, the system accounted for too much downtime.

In addition, employees tracked production with a paper-based system. "We used clipboards to record line stoppages – who stopped it, why and for how long," says Smith. "The result was that we had time unaccounted for."

After assessing the plant, GE determined that the answer lay in a flexible system built around workstations. That was coupled with a computer-controlled system to automatically collect operator performance data and provide feedback. The system also eliminated the inefficient paper-based tracking.

The first step was to trim down the variations in product work content and finished goods. This resulted in 24 design changes, which reduced component parts from 4,040 to 1,782. Finished goods stock keeping units (SKUs) fell from 6,852 to 2,762.

The next step was to change how HID lighting was assembled on the shop floor. Ten new production lines were designed (Advanced Equipment Co., www.aec-carolina.com). Eight of the lines are zero-pressure accumulation roller conveyor (Hytrol, www.hytrol.com). The other two are manual, tubular design systems (Worksmart Systems, www.worksmartsystems.com) that use a push cart to move products from one workstation to the next. "These are a step in between our old belt system and the new roller conveyor lines," explains Smith.

On a daily basis, management arranges a work schedule for the lines, taking several factors into consideration. "The schedule is put together using the customer request date, number of SKUs, work content of each SKU and what components are in place," says Smith. The work content and Takt time (time required to complete an assembly) determine how many people and workstations are needed on the line.

Each of the roller conveyor lines runs at a particular speed – slow, medium or fast – depending on demand for the finished HID lighting product. One, for instance, can produce up to 1,200 individual SKUs. "Once the Takt rate is selected for the day, the Takt stays consistent on each line," explains Smith. "If the workload changes, we adjust the number of stations we have in operation rather than the Takt."

On each line, as many as 12 people can work at stations to assemble the HIDs. If the line requires fewer than 12 people, operators adjust the conveyor system to bypass empty workstations with a push of a button on their data panel.

The first person on the line performs the required assembly, places the work-in-process back on a pallet on the conveyor and presses a pedal to release the pallet on down the line. Between stations, the pallet passes through accumulation zones, ensuring that the pallet arrives at the next station at exactly the right time for the next employee to begin work.

Throughout the day, operators work from a data panel at their workstations that gives them information about parts coming their way. The operators in turn enter information on the panels about the number of parts assembled, any mistakes that occurred and other relevant information.

All of the information is then compared to Six Sigma standards (see box below for more information about Six Sigma). "Throughout and at the end of each day, we analyze that information," notes Smith. "If the day's efficiency falls into the bottom quartile of performance, we take the top three 'dents,' or work stoppages/slowdowns, and seek to correct that action."

The assembly lines are arranged in a variety of configurations based on space availability and line requirements. Smith says that space had a lot to do with how each of the conveyor lines was designed. "We had to consider how much space was available, as well as how large the conveyor had to be."

There are four over-under conveyor lines. Designed for use in tight spaces, the under line begins on the bottom level. As it reaches the end of the line, a lift takes the pallet up to the over line.

One line is a loop that runs clockwise. When assembly is complete, a worker places the product on the conveyor for delivery to the end/beginning of the loop. There, a worker pulls the completed pallet off the conveyor and sets a new, empty one in its place.

Two of the lines are arranged in a side-by-side setup. "When a pallet reaches the end of the first line, a photoeye detects its presence and a conveyor chain automatically drives it across to the other line," explains Smith. "This is in an area where we have a lot of width but not length in the plant, so the system is shorter and wider than others."

The conveyor system, while a huge boon to the plant's operations, wouldn't be as effective if not for other enhancements to the plant's materials handling operations.

Eric Pate, a Six Sigma black belt, led the effort to upgrade the material flow in the plant. "We started by looking at individual areas in the plant," he states. "We saw that we were ineffective in getting parts where and when we needed them and were just building up storage."

One of the problems identified was that of the transactional logs. For instance, when a forklift driver picked up a crate of housings, he recorded it on a paper log. At the end of the day, someone else would pick up that and other paper logs and enter the data into a computer. "The system was subject to human error," says Pate. "We had to improve our accuracy with the help of digitization."

The solution was a wireless laptop mounted on each of the 10 sit-down fork trucks. Using Dell (www.dell.com) Latitude laptops, operators review schedules and see parts availability as they move throughout the plant. The laptops are hooked into a wireless local area network that keeps them in touch with the host computer wherever they are in the 800,000 square foot facility. Operators receive e-mails alerting them to demands or changes in the schedule. Each operator has further communication throughout the floor via company-provided cell phones. In all, outfitting each truck ran about $1,200 for a wireless laptop, the least expensive of the alternatives considered.

Pate says that the addition of the truck-mounted systems has been a great improvement to efficiency. "We were able to reduce transaction delays from less than 96 hours to less than 1minute, inventory accuracy has increased by 75% and material excess has been reduced by 80% as a result," he says.

In the end, the new shop floor layout teamed up with the improved lift truck movement of materials has resulted in new efficiencies that cut costs and facilitate achievement of Six Sigma standards.

Click on this icon to read how Zhone Technologies use conveyors for assembly.

Click on this icon to read how Ascend Communications use conveyors for assembly.