June 9, 2014
Two laser cutting technologies—one using additional axes of motion in the cutting head, and the other using scanning optics and no nozzle at all—shows the awesome potential of the solid-state laser in the cutting arena.
As fiber and disk lasers have done wonders to cutting throughput in this industry. What used to take days the 1-micron solid-state laser can finish within hours. The technology has presented one challenge over the past decade, though: As a manufacturer, how do you keep up with it?
This isn’t just a material handling challenge. It’s also a cutting machine design challenge too. 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 Dr. Andreas Wetzig of Germany-based Fraunhofer IWS, who offered two possible solutions, each applicable for different situations. Wetzig presented at the Advanced Laser Applications Workshop (ALAW), held June 2-4 in Plymouth, Mich., and organized by the Fabricators & Manufacturers Association, International®.
For the first solution, 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 effectively allows the head to move extraordinary quickly and, one day, may make 100 meters per minute a practical laser cutting speed, even for complex contours.
His second solution, for sheets about 0.5 mm and less, removes the nozzle assembly altogether. It follows the thinking behind remote laser beam welding, which guides the laser beam with high-speed scanning mirrors to different areas of the workpiece, moving nearly instantaneously from one weld to the next.
Remote laser beam cutting moves the beam with a high-speed scanning optics—and with 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 extremely thin material. The laser moves extremely quickly, but it takes multiple passes to melt through. As metal gets thicker, it takes longer to cut, 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.
Such speeds show the incredible potential of the solid-state laser. In a broader sense, it shows just how rapidly laser technology is advancing these days. Blink once, and you’ll miss yet another technological milestone.