Aachen / Apprimus (2017, 2018) [Book, Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (X, 145 Seiten) : Illustrationen, Diagramme
Ultra-short pulse (USP) lasers are already being successfully used in industry for laser structuring of injection-molding and embossing tools. The quality of the structuring result avoids the need for time-consuming and costly post-processing steps for removing burrs or melt deposits. Within the scope of this thesis a laser structuring system was developed that uses a polygon scanner for laser beam deflection. With the focal length of 163 mm, the system reaches scanning speeds of up to 360 m/s, which is clearly above the usual processing speed of 1 - 5 m/s with galvanometer scanners commonly used in the industry. As a result, the productivity and material ablation rate can be significantly increased while maintaining the highest surface quality. At these scanning speeds even laser pulses at pulse frequencies in the MHz range are separated which is essential for low thermal impact and exploiting the potential of today's high-performance USP lasers with more than 100 W average power. Geometrical deviations of the structuring result from the very small tolerances of the synchronization of all subsystems and the production of the components when laser structuring at these high scanning speeds and pulse frequencies in the MHz range. All relevant deviation sources, which contribute to a deviation of the structuring result from the target geometry, were analyzed and grouped into three categories: process data conversion, sys-tem- and process-related sources for deviations. The system-induced causes for geometry deviations can be statistically described for laser structuring with many processing layers. On the basis of the statistical individual error distributions of the components and signal flows of the system, the transfer function of the processing system can be calculated in the form of a point spread function. Using this statistical model, the expected geometry deviations of the processing result can be simulated using image processing methods.In addition, the point spread function can be used to compensate for the statistically expected deviations by preprocessing the process data. The comparison of the laser structuring results based on original and pre-processed process data shows that the laser ablated structure is visually sharpened by the pre-processing.
Schlaak, Helmut F.