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32 MMS April 2017 mmsonline.com RAPID TRAVERSE Machining Technology in Brief Fiber Laser Markers Do Much, Much More BY M AT T DA N FO R D L aser markers are less common than they appear to be—at least according to the strict definition of that term. "Laser micromachining center" is a better descriptor for many of the units in the field today, says Geof f Shannon, Ph.D., manager of advanced technology at Amada Miyachi America. This distinction may be semantic, but it can be eye-opening for those who have never con- sidered applications beyond marking. The right system, particularly one with a fiber gain medium, can provide a less costly, equally capable micro- machining alternative to milling, drilling, sinker EDM and more on parts ranging from surgical devices to tiny injection mold cavities, Dr. Shan- non says. "If you're marking, you're generally melting the material in a very thin layer, but what if you slow that down and use a higher-powered beam? You start to melt more of the material, and now you're welding. Eventually, you're cutting," he says. One reason fiber laser technology has become so popular is its generally competitive price point, he says. The reasons for this are well-documented: fewer costly consumables to replace and less frequent maintenance compared to other his- torically common laser marking technology, such as y ttrium or thovanadate ( Y V0 4 ) systems. For marking alone, the choice between fiber or YV0 4 might have nothing to do with performance and everything to do with economics. Beyond marking, however, other advantages of a fiber gain medium materialize quickly. Most importantly for metalcutting, fiber lasers are known for pulses with narrow spot sizes, sufficient power to remove material rather than create a thermal "tinting" effect, and sufficiently short duration to do so without impar ting too much heat. And whatever the capability of a YV0 4 unit, it's likely not as flexible or as easy to configure as a com- parable fiber system. "You can control spot size, pulse width, frequency—all the things you need to move between the different processes," Dr. Shannon says, referring to marking, welding and ablating/cutting. Still, he emphasizes that fiber lasers are not all created equal. He cites the following attributes as most beneficial for users hoping to alleviate the burden on milling, EDM or other equipment: H ig h b ea m q u a l i t y. A ny laser re sonator sustains only certain modes: essentially, wave patterns of light. Multi-mode lasers are typically delivered with a large fiber core (50 to 300 microns) and produce lower-intensity, flatter beam profiles. Single-mode lasers' smaller fiber cores (about 9 microns) deliver a narrower, more power ful beam, one that can be focused into a spot size as small as 20 microns. One factor to consider is M 2 rating, a measure of beam quality—specifically, how closely the beam matches the ideal Gauss- ian profile, in which intensity is greater at the center than the edges. The lower the M 2 rating, A fiber laser marker cut this 75-micron-wide channel into a metal foil measuring only 25 microns thick— that is, about one-fourth the width of a human hair. The channel was machined to 13 microns deep. That's the equivalent of micromachining away all but about one-tenth of a human hair's worth of material. Depth variation was held to ±1 micron.