Mariana Forrest perhaps knows ALAW® better than anyone. The president of laser consulting firm LASAP Inc., based in Troy Mich., has attended all 20 conferences. She was there back when it was called the Automotive Laser Applications Workshop, and in recent years, after the event was broadened and renamed (though conveniently keeping the same acronym) the Advanced Laser Applications Workshop.
During a brief presentation at this year’s event--organized by the Fabricators & Manufacturers Association Intl.® and held in Livonia, Mich., May 2-3--Forrest recalled all the years presenters from around the world, including Japan and Germany, came to Michigan to show advanced laser applications in automotive.
For many of those years North American automotive engineers were wary of the laser’s suitability for automotive applications, especially for body-in-white. Body panels had yet to be designed for laser processing. Unlike resistance spot welding, the laser needed to access a workpiece from just one side. But it also required precise fit-up. Then there were those ugly marks on coated material left by that pesky zinc outgassing.
What a difference two decades makes.
Laser welding has made great headway in the automotive business, now used for everything from long seam welds for roof panels, to the hundreds of welds used in seatbacks. In remote laser beam welding, with focal lengths of a meter or more and high-speed scanning heads, the beam moves from one weld to the next almost instantaneously.
Be it fixed or mounted on the end of a robot arm, the remote laser welding head sends short bursts of laser light to the workpiece below, completing hundreds of short welds in a matter of seconds. If needed prior to the operation, the laser beam can form small dimples in the metal that essentially give room for the vaporized zinc to escape.
This year ALAW got its first taste of a new kind of laser technology: a direct-diode laser with enough brightness and power to cut through conventional sheet metal. Not too long ago, cutting most sheet metal gauges efficiently with a direct-diode laser seemed like a farfetched concept, and for good reason. Historically, direct-diode lasers haven’t had adequate beam quality to do the job. That’s because there has always been a trade-off between high power and high beam quality. In a direct-diode setup, you couldn’t have both.
This may be changing. At ALAW, Jay Liebowitz, vice president of sales and marketing at TeraDiode Inc., Wilmington, Mass., described the company’s wavelength beam-combining technology.
“People were very excited when the diode laser was invented 50 years ago,” Liebowitz said. “It was economically efficient and small. But you couldn’t gang them together and maintain the brightness.” This, he said, has been why pumping mediums--be it a disc, double-clad fiber, or anything else--have been necessary to produce a laser suitable for most industrial metal cutting.
The problem has been that in a direct-diode approach, combined diode laser beams don’t travel in the same direction or merge neatly to produce a small spot size. In a low-powered direct-diode system, this degradation is relatively minor, but it becomes more significant as more diodes are ganged together for more power.
As Liebowitz explained, wavelength beam combining overcomes this by combining similar but slightly different wavelength beams from an array of diodes. Those wavelengths combine in such a way that produces one powerful beam with waves going in the same direction and to the same spot.
Over two decades the applications discussed at ALAW have given attendees a glimpse of the current state of the art and of the future--showing how, among all metal fabrication technologies, the laser stands apart. And this year’s presentations proved yet again that laser technology, even after all these years, remains in a state of continual evolution.