High dynamic beam shaping by piezo driven modules for efficient and high quality laser beam cutting and welding

Today's laser remote processing e. g. cutting and welding is often limited by comparatively low oscillation frequency of the beam focus. Traditionally, high frequency in plane oscillations of the beam is realized with galvo-scanners. New requirements in industry are demanding for not only fast in plane motion but for high-speed active vertical distribution of the beam energy within the workpiece. For laser beam cutting of thick plates, an increase of cutting edge quality is expected. In terms of laser beam welding of aluminium material, a significant process stability improvement is aimed in connection with a weld seam quality enhancement. This paper describes a novel concept of beam shaping optics using piezo actuators for fast focus modulation in z-direction with working frequencies above 2.5 kHz. The development of the actuator concept will be presented as well as the technical realization of the piezo driven modules and their integration into commercial cutting and welding optics. Optical characterization of the beam propagation and the possibilities for dynamic z-modulation will be demonstrated. First application-oriented experimental investigations are presented too, proving the functional capability and showing basic interrelations between z-modulation and process behaviour for typical cutting and welding processes.