August 6, 2014
The laser has helped define the modern precision metal fabrication industry, and this year’s Advanced Laser Applications Workshop shows just how far the laser has come. Blink once, and you miss another technological milestone.
Forty years ago, an all-caps font got the banner headline in this magazine: LASER METAL CUTTING. To the right is a black-and-white photo of a worker monitoring a 500-W CO2 laser fitted on the gantry of an oxyfuel cutting table. It was the first time The FABRICATOR, then just 4 years old, covered the laser in such detail, but it wouldn’t be the last. It was one of those rare moments when hype eventually (though not immediately) matched reality. The laser, it was said, would transform metal fabrication and manufacturing in general. Boy, did they get that right.
Over the decades the laser has defined the evolution of modern precision metal fabrication. It has become the ultimate soft tool, adaptable to an amazing variety of manufacturing demands. These demands were made extraordinarily evident at this year’s Advanced Laser Applications Workshop, organized by the Fabricators & Manufacturers Association International®, held in June in Detroit. Need to weld something? A laser can do that. Need to heat-treat something, clad it, or anneal it? A laser can do those too. Need to cut it at a speed that outpaces a stamping press? Not yet, at least for most standard applications, but a few presentations at ALAW showed the potential of what could be.
Central to many presentations was the high-powered, 1-micron-wavelength beam, including the fiber and disk laser, which has done wonders for cutting throughput. What used to take days the solid-state laser can finish within hours. The technology has presented one challenge over the past decade, though: As a fabricator, how do you keep up with it?
This isn’t just a material handling challenge; it’s also a cutting machine design challenge. When the laser machine’s gantry moves, especially when accelerating and changing direction—two things it does constantly when cutting complex contours—the machine can drive the cutting head only so fast.
“In some applications you could cut 100 meters per minute, but no machine would be able to handle it.”
So said Andreas Wetzig, department head for laser ablation and cutting at Germany-based Fraunhofer IWS (www.iws.fraunhofer.de). He offered two solutions, each applicable for different situations. For the first, Wetzig showed a system that takes a “dynamic local axes” approach. Not only does the gantry move the cutting head, but the head itself also moves in X and Y, independent of the gantry. Inside the head assembly, specialized scanning optics direct the collimated beam toward the focusing optic, through the nozzle, and to the workpiece. This allows the head to move extraordinarily quickly, even for complex contours.
His second solution, for sheets about 0.5 mm thick and less, removes the nozzle assembly altogether. It follows the thinking behind remote laser beam welding, during which high-speed scanning mirrors direct the beam to different areas of the workpiece, moving nearly instantaneously from one weld to the next. Similarly, in remote laser beam cutting, high-speed scanning optics move the beam, and there’s no nozzle. Yes, the process seems counterintuitive. After all, how can you make a clean cut without a nozzle to guide the assist gas? To overcome this challenge, Fraunhofer uses an intense single-mode laser (5 kW for 0.5-mm material, 1 kW for 200-micron material) that ablates the material layer by layer. The laser literally vaporizes metal to create the kerf.
At present this technology makes sense only for thin material. The laser moves extremely quickly, but it takes multiple passes to melt through. As metal gets thicker, it takes more passes to melt through, so the speed difference between conventional and remote laser cutting narrows. But for thin material, profiles are cut at eye-popping speeds. One blink and you’d miss it.
Sascha Weiler, program manager, microprocessing at Farmington, Conn.-based TRUMPF Inc. (www.us.trumpf.com), discussed the potential behind short-pulsed and ultrafast laser applications, the nanosecond, picosecond, and femtosecond pulsing that can allow the laser to perform an amazing variety of useful tasks, from microhole drilling and scribing to annealing and cleaning.
For instance, Weiler showed how a pulsed disk laser is being used to clean a specific area for weld preparation. A scanning laser head emits a line-shaped beam directly ahead of the laser welding beam, ablating contaminants and leaving a clean surface in its wake. Weiler showed how the process can be used for edge preparation of coated laser-welded blanks, removing the aluminum silicon coating, between 10 and 20 microns deep.
“You can selectively ablate the coating without touching the steel,” he said. “And you can go 15 to 20 meters per minute. The cleaning keeps up with the welding speed.”
Another laser application has epitomized the bleeding edge of modern fabrication: additive manufacturing, the focus of the conference’s final keynote, given by Sudhir Tewari, principal engineer at GE Aviation’s Manufacturing Technology Lean Lab (www.geaviation.com).
Tewari discussed not only the potential of additive manufacturing, but also the challenges. For instance, if you build up a part layer by layer, as with laser cladding or direct metal deposition, how does a company set up a quality regimen? In many sectors, industrywide specifications don’t exist yet.
At the same time, additive manufacturing is spurring truly unique-looking parts, proving that form should follow function, and additive manufacturing makes a lot of forms possible. Tewari showed a bracket design originally machined out of a metal casting. The additive-manufactured bracket had an almost claw-like shape, vaguely resembling eagle talons, but with holes placed in odd spots, all for weight savings and improved functionality. Such a part would be incredibly costly to make using conventional techniques. But with additive manufacturing, the designer’s palette expands.
The laser is helping to make all of this a reality, and so much of it would have been considered science fiction in 1974. What a difference four decades makes. Like in previous years, ALAW showed just how fast laser technology continues to advance. Blink once and you’ll miss yet another technological milestone.
The FABRICATOR® is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971. Print subscriptions are free to qualified persons in North America involved in metal forming and fabricating.