Need a creative solution to a design problem? Try some out-of-the-box thinking. That's what two network engineers at Harley-Davidson did recently. Curiously enough, their problem involved--boxes.
Harley's York, PA, engineering and manufacturing plant needed to increase its motorcycle production rate to keep up with increasing customer demand. So, while one group of Harley engineers worked on upgrading the assembly line, Eric Martin and Greg Schuman set about upgrading the infrastructure--including the enclosures--to improve intraplant communications.
They arranged to wire up new fiber-optic cables for the plant's new intelligent hubs, the interconnection between the computer cables and the facility's network. The goal: give engineers more bandwidth for sharing CAD files, smooth the transfer of specific information on each new bike to the assembly line, enable accounting and other business operations to communicate with each other, and carry messages from management to employees over the plant's closed-circuit TV system, among other things.
"We had only eight weeks to complete the project," Martin recalls. Two stumbling blocks: The plant's existing enclosures were too small to handle the upgraded equipment, and they couldn't muffle the additional noise from the new equipment.
The noise came, primarily, from large fans required to control heat from the intelligent hubs. "The noise was unbelievable," Schuman recalls.
If they missed their deadline, productivity would have dropped at the plant, Martin says. "We couldn't let the lack of cabinets put the schedule in danger."
Nor could they compromise the upgraded communications system by specifying the wrong type of enclosures. So, in effect, they designed their own enclosures based on a modular product line from Hoffman (Anoka, MN). Here were the key design factors:
- The enclosures would have to be tight enough to protect the electronic equipment and fiber-optic cable terminations from dust on the factory floor. Dirt is a conductor, and dust can obscure the light source on the end of fiber-optic cables. Those potential dangers meant the enclosures would have to be NEMA 12-rated.
- While dust may have been the major enemy on the floor, heat was not far behind. Schuman estimated that temperatures in the boxes on the floor could go as high as 125F. That meant they would have to accommodate the air conditioners that would keep the temperature at about 85F. They had to make sure that the heat didn't go lower than 85F, otherwise the air conditioners would generate condensation and leak on the equipment.
- In the office areas, excessive heat was the major problem to consider in enclosure design. Schuman's goal there was to keep the temperature in the cabinets between 85 and 90F.
- The enclosures would also have to be rugged--especially on the floor. Someone could accidentally ram a skid against them, so they would have to be tough enough to withstand such a collision.
- They would also have to be flexible so Martin and Schuman could expand them if necessary. Flexibility was important because Harley changes its network technology every few years.
- They had to provide easy access to the cabling. "I can't go to shut a door and have it not work," Schuman says.
- And, the vendor would have to deliver on time.
(EMI/RFI is, generally, a big concern. Schuman says the fact that the cabinets they chose are metal and grounded was a plus.)
The company was already using a variety of solid-wall enclosures from Hoffman on the factory floor. They were rugged enough, but, says Schuman, they were hard to open and close. Schuman and Martin wanted to solve that access problem and at the same time allow for possible infrastructure expansion in the future.
That's where the out-of-the-box thinking came in. Why not have enclosures you can take apart and move easily, or expand by joining them together, they thought.
Prior experience. Actually, they already had enclosures like that elsewhere in the plant: the ones enclosing their Compaq servers. They were a proprietary design by Compaq, but Schuman and Martin figured a similar design could work for the intelligent hub.
After reviewing the plant environment, expected thermal issues, the angles of the racks that would be inside the cabinets, and the possibility of expansion, Martin and Schuman decided on Hoffman's PROLINE(TM) modular enclosures.
With frames consisting of seven roll-formed surfaces of 12-gauge steel, robotically welded corners, and solid steel corner blocks, they met the requirement for ruggedness, Schuman says.
The NEMA-12 design, which includes foam-in-place urethane gasketing, will keep out dust, dirt, moisture, and oil, and muffle the air conditioner noise, Hoffman promises.
And, the modular design gave Schuman and Martin the flexibility they wanted for future expansion. "I can pull the sides off and move the equipment around easily," Schuman says. "I can put individual cabinets together to make one larger cabinet."
Regarding access, Harley workers cut their own access holes in several areas on the cabinets. But, the access feature Schuman and Martin like the most--and one of the things that sold them on the enclosures--is the latch system.
The system is based on a hook-and-roller latching system. "To unlock the door, I turn the key and push a button and the handle pops out," Schuman reports. "Then, I turn the handle 90 degrees and the door opens. To close the door, I turn the handle back 90 degrees and push the knob in."
Plans across the sea
Enclosures are not only design components, they have to be designed themselves. Hoffman's PROLINE enclosures were the result of a two-year joint effort with engineers at the company's German partner, Schroff. "We both had modular enclosures, but they met different standards," says Todd Mickley, Hoffman's engineering manager for new product development. Hoffman's, of course, met National Electrical Code, Underwriters Laboratory, and Canadian Standards Association requirements, and were designed in English units. Schroff's were in metric and complied with standards of the International Electrical Commission. The major differences: UL's metal-thickness requirements were tougher, while the IEC's grounding requirements were tougher. "We decided to design to the most stringent standards in all areas of the product," Mickley says. They specified metric for all fasteners and for spacing in the frames. The design team consisted of four engineers in the U.S. and four in Germany. All used Alias for rendering, SDRC's I-DEAS Master Series software for CAD, and Parametric Technology Corp.'s Pro/MECHANICA for finite element analysis. Engineers faxed design suggestions to each other at the end of their respective days. The time difference gave the teams about six hours to work on each others' suggestions before their counterparts arrived for work. The teams also had video conferences each week using technology from PictureTel. Once a month, on an alternating basis, the teams crossed the ocean to have meetings to iron out design problems. Manufacturing of the enclosures is done in Germany and the U.S.