Microelectromechanical systems (MEMS) have been made available to the laser welding and cutting markets due to a new mirror coating developed by the Fraunhofer ISIT and IWS groups.
Previously, the silicon-based, fast-moving micromirrors had been unable to handle much more than a few milliwatts without melting, making them unsuitable to cutting and welding applications which require much higher powers. With the new coating however, MEMS can withstand kilowatt powers and allows their use in the cutting of aluminium and sheet steel.
Also, silicon micromirrors can guide laser beams at extremely high speeds, allowing operators to dose heat input to workpieces with a very high degree of precision, swivelled back and forth at extremely high speeds reaching up to 100,000Hz. This allows the laser energy to be distributed much more effectively than with conventional laser systems, whose mirrors swivel at only around 1,000 hertz.
This rapid oscillation means the user can distribute laser energy much more effectively and tailor it to the material, which improves the quality of a cut edge. While solid-state lasers are catching up with CO2 when it comes to cutting certain materials, the cut edges do not currently match up to the quality habitually achieved when cutting with CO2 lasers. However, the targeted heat input that can be provided by MEMS mirrors improves edge roughness and avoids burr formation on the underside of the cut edge.
Fraunhofer’s new MEMS micromirrors are also bigger than conventional ones, meaning they can handle broader beam diameters. For the developers, the challenge consisted in achieving high frequencies despite the size. ‘To address this issue, we operate the mirrors in air-evacuated vacuum pods in order to minimise attenuation of the oscillating mirror,’ says MEMS mirror expert Ulrich Hofmann at Fraunhofer ISIT.
Fraunhofer Institute for Silicon Technology ISIT in Itzehoe, Germany, and the Fraunhofer Institute for Material and Beam Technology IWS in Dresden, Germany, will present their work at the Laser World of Photonics trade show from June 22 to 25, 2015 in Munich, Germany.