Product Code: ICA10_M205

Large-Scale Riblet Surfaces using Multi-Spot Micro Machining
Authors:
Frank Siegel, Laser Zentrum Hannover e.V.; Hannover Germany
Viktor Schütz, Laser Zentrum Hannover e.V.; Hannover Germany
Uwe Stute, Laser Zentrum Hannover e.V.; Hannover Germany
Rainer Kling, Laser Zentrum Hannover e.V.; Hannover Germany
Presented at ICALEO 2010

We report on a new approach for a substantial performance increase of large-scale micro machining using picosecond-lasers by combination of Diffractive Optical Elements (DOEs) for beam splitting with conventional scanner technology. We demonstrate practical multiplication of conventional single-spot machining at gentle ablation depths of 25 nm/pulse. This new approach is based upon the fabrication of Riblet surfaces on superior compressor blades as one exemplary application scenario for high-precision laser patterning of micro structures. Single-spot ablation rates of about 0.1 mm3/min are increased by the factor of 7 when applying multi-spot ablation with a 1 x 7 array. Limitations for using DOEs such as thermal interaction of adjoining spots as well as process-related heating of the work piece are observed, discussed and mathematically described. Applicable process windows for efficient parallel micro machining are identified. We conclude with an estimation of maximum achievable ablation rates up to 7.0 mm3/min and above, based on the power reserve of current picosecond-lasers combined with available DOEs with up to 225 spots.