Reprinted from TransForum (PDF format) newsletter, Vol. 2, No. 3, Fall 1999.

This weld monitor, developed in TD's laser lab, is used in Daimler Chrysler manufacturing plants.

DaimlerChrysler’s new state-of-the-art Indiana Transmission Plant (ITP) in Kokomo, Ind., which manufactures and assembles transmissions for the Jeep Grand Cherokee, is abandoning its current laser weld monitoring systems in favor of a new infrared (IR) laser weld monitoring technology pioneered by researchers at Argonne's Technology Development Division. The switch to the new technology, which has been further developed and commercialized by Spawr Industries, is expected to be completed by March 2000, according to company spokesman Jack Evanecky, area technical manager at ITP.

Throughout the automotive industry, laser welding has been rapidly overtaking traditional arc welding technology as the state of the art in recent years, but an easy-to-use, cost-effective means of detecting bad welds has been lacking. At ITP, where the production rate for gear-train components is 1,600 per day, welds were monitored by means of a cumbersome, expensive process that required immersing bulky parts in dunk tanks for testing via ultrasound. The test units cost $23,000 apiece for the equipment alone, plus another $100,000 for probes and automation. The ultrasonic equipment also poses a maintenance challenge and too often falsely idenfies satisfactory welds as defective.

Enter the IR weld monitor, initially developed by then-Argonne engineer Keng Leong and his colleagues in cooperation with private industry and USCAR’s Low Emissions Partnership (LEP). The monitor uses a passive sensor and related optics to detect heat from directly above laser welds as they are made (“real time” operation), so it doesn’t add to cycle time. It provides feedback in the form of ac and dc voltage traces that carry information about the weld’s surface, penetration depth, uniformity, the presence of impurities, spattering, etc. Spawr Industries (Lake Havasu City, Arizona) integrated the Argonne researchers’ technology into a laser beam delivery system that permits better control of process variations. Spawr offers the monitor as an off-the-shelf commercial product for $17,000 (with a personal computer and a scraper optic).

DaimlerChrysler bought two of the Spawr IR weld monitors for its ITP plant earlier this year. Over the summer, Evanecky and Spawr’s owners shared their ideas for improvements, “playing with the technology, exploring the limits and trying to get a handle on a good process window.” At present, four of the new units are in operation on the plant floor, and seven more will be installed (and process windows established) soon, entirely replacing the more expensive conventional units. “I have also purchased two additional units to be installed on our universal laser workstations,” says Evanecky, “to act as production support for the 11 systems; this makes a total of 13 Spawr units that will be in operation by mid-summer of 2000.” Cost savings, in equipment alone, are projected at well over a million dollars. In addition, by eliminating the need for destructive testing (once a routine operation) of welded components, the new technology is expected to cut scrap production by 10%.

Two more of the new IR weld monitors are being evaluated at Kokomo Transmission Plant (KTP), a sister facility to ITP. According to Evanecky, KTP is also very interested in replacing its existing ultrasound systems wherever possible; that switch could mean buying 20 more of Spawr’s monitors. And after that? Evanecky doesn’t hesitate to predict that the applications will go well beyond their present efforts. “There’s a whole lot of welding required in DaimlerChrysler’s manufacturing operations,” he says. “I really don’t see any limit to the potential for using this technology.”

Initial development of the IR laser weld monitoring technology at Argonne's TD division was supported through cooperative research and development agreements between DOE and Delphi Energy & Engine Systems and the LEP (consisting of General Motors, Ford, and DaimlerChrysler). Argonne's research under the cooperative research and development agreements was funded by DOE's Office of Science, Laboratory Technology Research Program.

The nation’s first national laboratory, Argonne National Laboratory supports basic and applied scientific research across a wide spectrum of disciplines, ranging from high-energy physics to climatology and biotechnology. Since 1990, Argonne has worked with more than 600 companies and numerous federal agencies and other organizations to help advance America's scientific leadership and prepare the nation for the future. Argonne is operated by the University of Chicago as part of the U.S. Department of Energy's national laboratory system. -- Floyd Bennett

For more information, please contact Catherine Foster (630/252-5580 or cfoster@anl.gov) at Argonne.