Sometimes, simple is best.

That's what Lucent Technologies discovered when it designed a new materials handling system for a plant in Dublin, Ireland, that performs final assembly and test operations on Internet and information system switches and related network hardware.

This is the equipment of the new economy. The systems are used to transport electronic information over intranets and the Internet for a variety of service providers and enterprises.

"From a materials handling standpoint, we were starting from scratch with an empty floor," says Christy Mooney, the engineering projects manager at Lucent Technologies who worked on the design of the project.

"Our challenge was to devise a system to move heavy products through a series of sequential operations, and to do it with the flexibility to cope easily with changes," says Mooney.

Fork lifts could have been used to move the switches, which are the size of small refrigerators, from workstation to workstation. That would create a significant amount of traffic on the plant floor, and expose the equipment to potential damage.

What's more, because both production numbers and the product mix are unpredictable, the system designers had to create a system that could handle a wide variety of product.

"We defined a maximum system size, and said they'll never be bigger, higher, or heavier than this," says Mooney. "And we defined an upper production number and said, that's as fast as the system will ever have to run. Beyond that, we couldn't predict a whole lot because our systems are custom ordered."

What Mooney and the team of outside consultants came up with was a materials handling system designed around a horseshoe-shaped powered conveyor line (Ermanco Inc., a Paragon Technologies brand, www.ermanco.com,) that can manage the movement of work-in-process from beginning to end.

By elevating the section of conveyor that forms the U-shape over the work floor, the system also saves space.

"We do use fork lifts to get the chassis to the line, and a lift table to get it up on the line," says Mooney. "After that, the conveyor does the rest. The equipment never leaves the conveyor until it's in a crate and ready to go out the back door."

Don't confuse the simple layout for a system with limitations. The conveyor system is programmed to manage the routing and rerouting of the equipment throughout the testing process, insuring that no critical tests are missed.

The result saved space, reduced damage, and improved productivity.

The Dublin facility supplies customers in Europe, the Middle East, and Africa.

The manufacturing at this location primarily involves final assembly, customization, and testing. That's because the differentiators between switches are the circuit boards and software that Lucent installs and tests in Dublin.

Contract manufacturers in Ireland, Scotland, and the U.S. manufacture the components and fabricate the equipment chassis. The manufacturers also warehouse components and chassis at supply points in Dublin to serve Lucent.

The switches are customized to order at the Dublin plant. First, Lucent adds circuit boards in a receiving area. The chassis are then lifted onto the conveyor and directed to workstations, where software is loaded and the equipment is tested. A typical unit goes through six tests, which can last anywhere from an hour to a day. The speed of the production line is not nearly as important as the quality of the end product.

"This is a high-mix, low-volume facility," Mooney explains. "We might only do three thousand units per quarter, but every system is different."

"Our production chart looks like a hockey stick," Mooney adds. "Volume ramps up quite steeply in the last couple of weeks every quarter. It's just the nature of our business. The system is flexible enough to support the high volumes we need during our busy time."

The system consists of two lines of roller conveyor joined at one end to form a horseshoe. Each line measures 40 meters, or about 130 feet. The conveyors are fully zoned and rely on a zone-to-zone tracking system to track pallets from one station to the next.

Finally, each line is equipped with 16 addressable stations where product can be sent. Each addressable station has space for two work areas, providing a total of 32 work areas per conveyor line, or a combined 64 workstations.

The line and work cells can automatically be reconfigured to map any combination of test sequences based on the software that has to be tested and the available workstations across both conveyor lines. If a workstation is busy, the system will automatically plan a new route to an open station to complete a test.

Orders at the Dublin facility are inducted into the system when the manufacturing system creates a bill of materials.

The physical part of the manufacturing process begins when a subassembly arrives from one of Lucent's outside contractors. The chassis are then affixed to a slave pallet that will remain with the part throughout the production process. Next, Lucent adds any printed circuit boards, power supplies, or other components that haven't already been installed by outside contractors for that order.

Several tests are performed at that point. Once the subassembly passes those tests, it's ready for the customized software and testing that differentiates one switch from another.

Chassis are transported to the conveyor line by hand-controlled, walk-behind pallet trucks that have been customized to operate in the confined space of the Dublin facility.

The electric "walk-behind" trucks feature rear-wheel steering for maximum maneuverability and forks that were modified to allow a truck to pick up a variety of slave pallets.

A hydraulic lift table raises the chassis to transfer the product onto the conveyor system.

Once the equipment is on the line, a bar code is scanned. "There's a routing in the computer for each order," Mooney explains. "When you scan the model number, the computer knows the route for that subassembly. And, if there are multiple chassis at one station, the computer determines an alternative route among the 64 stations."

In fact, the software is designed to optimize the workload and reduce queuing at any one station. If necessary, however, operators can re-route products by entering commands through a touch keypad.

Once a chassis has been scanned and a route established, the switch begins its journey down the roller conveyor. This is the heart of the system.

Several considerations went into designing the line.

Space limitations were a factor. The system frees up floor space that could be used for workstations by driving discharge conveyor lanes and the in-feed lane with a single motor.

A lift conveyor connects the two lines at the back of the facility to save more space: switches are lifted and then travel overhead through the ceiling to connect to the other side of the conveyor.

As a subassembly travels down the line, photo-eye sensors and a zone-to-zone tracking system track the product through the test workstations.

When a subassembly reaches the correct workstation, transfer belts in the main conveyor line are activated. These divert the chassis onto a zone accumulation conveyor. The belts are kept under pressure to reduces the G-force on the product as it's transferred.

An operator pulls the chassis from the accumulation conveyor onto a ball table at his work station. There the software is loaded and tests are initiated.

Once a test is completed, the operator scans the model number to indicate that the tests are done, and pushes the chassis into an out queue at that cell. The accumulation conveyor relies on zone controls that receive a signal from a sensor when a product is present. One product per zone will always be maintained to avoid damage.

The system uses the route map in the computer, in addition to pass/fail information, to correctly route the equipment to the next process step.

If the next workstation on the route is free, the conveyor will take it away. If not, the chassis will remain in the queue.

After the software for a switch has been installed and tested, it is checked for electrical shorts and overall quality.

From there, the conveyor carries the completed switch through a wall and into a warehouse and shipping area. There, the switch is packed into a shipping container and scanned one last time. The completed product is conveyed to a shipping queue, where it's unloaded by a pallet truck and held until the rest of the order is ready for shipment.

Once all the components for an order have been scanned into the system, the computer system closes out an order and prints the shipping documentation that will accompany a delivery.

The system has proven itself. "It's very flexible, allowing us to have a mix of products on the line at any time," says Mooney, "and it's reduced the commotion on the factory floor. Without it, there would be a significant amount of fork lift traffic traveling between stations, and that would be dangerous for our employees and our products."

"We're extremely satisfied," he adds. "It's allowed us to reduce our labor costs since we're using much less manual labor, and increase our productivity and efficiency with the automated routing."