Measuring Laser Beam Welding Power Using the Force of Light A novel optical laser-power measurement technique offers high accuracy in real time What could be more fun than welding with a laser? The idea of a beam of invisible (infrared) light powerful enough to melt metals such as steel and aluminum is not only intriguing but very practical. Laser beam welding takes advantage of the unique delivery mechanism of laser light in order to provide high energy density, deep penetration, minimal heat-affected zone, and the ability to weld at a distance from the workpiece. However, laser beam welding also brings with it new challenges in terms of characterizing the operating parameters. The most fundamental of these is the optical power delivered by the laser. Currently, there are two basic approaches to measure the laser power delivered to the welding work surface, but both have limitations. It comes down to a tradeoff: either the laser’s power can be measured accurately but not during the weld process, or it can be measured in “real time” while welding is taking place, but with greatly reduced accuracy. The benefit of both accurate and real-time power measurement would be a great improvement in laser-welding quality monitoring, especially when precise power delivery is required for critical welding applications such as aerospace manufacturing. In response to this need, the National Institute of Standards and Technology is developing a new way to measure laser power that allows both accurate and real-time measurements of laser welding power. Traditionally, accurate measurement of high laser powers involves measuring how much heat is delivered. Typically for this purpose, a “thermal” power meter is used. In principle, the 30 WELDING JOURNAL / MARCH 2016 BY PAUL WILLIAMS, JEFFREY SOWARDS, AND BRIAN SIMONDS Laser welding a pipe while simultaneously measuring the laser’s power by its force.
Welding Journal | March 2016
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