Assembly in Action: Assembly Automation Eliminates Wrong Numbers
AT&T’s private brand exchange (PBX) phone systems, manufactured in Denver, are customized for individual customers. They are in small and large businesses, hospitals and universities. Yet people take the complex technology behind each clear cross-country conversation for granted.
At the Denver facility, one look at a single printed circuit board, which makes up the PBX nerve center, is eye-popping. Hundreds of components, some not much larger than a pinhead, occupy its landscape.
Considering that some complex PBX systems, which support thousands of phones, have an array of dozens of boards, the question "How does AT&T get it right?" arises.
There’s no room for error. One wrong component compromises a board. The board must be pulled, and a technician has to troubleshoot it. The errant component is removed by hand, the solder is carefully cleaned away, the correct component is inserted and then the board is retested. The process takes hours and slows final assembly.
Now, the assembly operation is virtually error-free thanks to a device that includes bar coding and spread-spectrum radio frequency technology. Operators select bar-coded reels of components and place them in a predetermined order in a robot feeder. The robot, programmed to follow a board schematic, inserts the components.
When the reels are loaded onto the component feeders, the operators scan each one with a Symbol Technologies (Holtsville, NY) laser radio terminal (LRT) 3800. The boards are also barcoded and scanned.
The LRT 3800 combines a noncontact laser scanner, 16-bit DOS computer, keyboard and screen with the Symbol Spectrum One radio frequency network in a portable, handheld device. This device transmits the bar-coded information back over the Spectrum One network to the facility’s designated host computer. The information is cross-checked in real time against a file, and the operator is prompted with an audible signal. An incorrect reel triggers a distinguishable warning beep when scanned. "By combining bar-coding and radio frequency, we’ve improved quality, and we know it in real time," says Andy Zumfelde, a member of AT&T’s technical staff.
Operators used to pick the component reels and place them in a feeder, and another operator used to double- check the work. Each reel’s identifying code number was nine digits, and some of them had repetitive numbers. There could be 30 to 80 reels for each board setup. It was easy to select the wrong reel, and someArial the second operator missed that mistake.
"We’ve not only reduced our mistake rate down to virtually zero, we’ve also become more efficient. The 15-minute manual process to load and double-check the component feeder now takes about 2 minutes. We’re far more responsive," says Zumfelde.
One concern was the acceptance of the LRT 3800s and the new technology by operators who spent years manually loading and checking the component feeders.
"I was tentative at first," explains Karen Dwyer. "But now, I’m thrilled. It’s just a new tool that’s helping me do my job better. The very first time I used the scanner, I double-checked reels that I just placed in the feeder. Sure enough, I made a mistake. I was sold. Now, I wouldn’t think of working without it. We have a banner that hangs over the plant that reads, ‘Quality Systems. Quality People.’ This fits right in."
Another concern by Zumfelde was the use of the Spectrum One technology at the Denver site. The plant is 1.2 million square feet and lined with storage racks and heavy machinery, and the transmission range1,000 plus feet from wall to wallwas at the limit for a single transceiver and antenna setup.
"It hasn’t been an issue. We have two antennae, use 45 LRTs and we have the freedom to roam the site," Zumfelde points out. "Two favorable aspects about our implementation of spread spectrum radio frequency technology are the quick response and transaction turnaround time, and the option to reconfigure machines and operators without upsetting our configuration."
For more information on radio frequency technology, call 800-722-6234 or visit www.symbol.com.