@article{ZettlKlarRungetal.2021, author = {Zettl, Julian and Klar, Maximilian and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Laser turning with ultrashort laser pulses}, series = {Journal of Manufacturing Processes}, volume = {2021}, journal = {Journal of Manufacturing Processes}, number = {68}, doi = {10.1016/j.jmapro.2021.06.025}, pages = {1562 -- 1568}, year = {2021}, abstract = {We report on a comprehensive micromachining study of rotationally symmetric parts using femtosecond laser. A laser turning process with tangential impingement of the laser radiation complemented by a trepanning optics is implemented as to accomplish a true laser lathe micromachining approach. With the objective of optimized ablation rate and reduced surface roughness, the influence of pulse energy, feed rate, trepanning diameter and angular beam incidence, respectively, is investigated for processing stellite rods. We find the smallest feasible feature sizes of 8.5 μm in diameter and smoothest surfaces with an arithmetic average of the roughness profile as low as 0.18 μm. The surface roughness, however, appears to be limited by the occurrence of laser induced periodic surface structures provoked by the femtosecond laser radiation. Furthermore, the variation of the fluence in accordance to the incidence on a curved surface is discussed and the heat input into the material is examined through a longitudinal cross section.}, subject = {Ultrakurzer Lichtimpuls}, language = {en} } @article{ZettlKlarEsenetal.2020, author = {Zettl, Julian and Klar, Maximilian and Esen, Cemal and Hellmann, Ralf}, title = {Generation of Rotationally Symmetric Micro Tools using Ultrashort Laser Pulses}, series = {Journal of Laser Micro/Nanoengeneering}, volume = {15}, journal = {Journal of Laser Micro/Nanoengeneering}, number = {2}, doi = {10.2961/jlmn.2020.02.2007}, pages = {118 -- 122}, year = {2020}, abstract = {We report on the fabrication of rotationally symmetrical geometries with ultrashort laser pulses impinging the constant rotating workpiece tangentially. This particular micro machin-ing of geometry is referred to as laser turning, upon which the laser beam is, in general, orient-ed perpendicularly to the rotational axis and tangentially to the work piece. The target geome-try is realized by moving the constantly rotating specimen according to the specified geometry along the focused laser spot. In contrast to mechanical turning, laser turning induces a mini-mized amount of lateral forces through friction that might deteriorate the geometry. In this study, laser turning is examined for stellite as a function of pulse energy and pulse length in the range between 240 fs and 10 ps. Shorter pulse lengths and higher pulse energies increase the achievable ablation rate, while in the pulse length regime of below 1 ps lower roughness is achieved. With a maximum ablation rate of 1.27 mm³/min and a minimum roughness of 0.17 µm, laser turning combines both, fast processing and high surface quality.}, subject = {Ultrakurzzeitlaser}, language = {en} }