Laser polishing is a technique for smoothing the surface of metallic substrates. The roughness after polishing does not only contain remains of the initial surface roughness, it also contains new roughness due to surface structures, which are introduced by the polishing process. Since these structures greatly contribute to the roughness, it is necessary to understand the mechanisms that lead to their formation so as to prevent the structures from forming and allow higher smoothing of the surface. Hence, in this publication it is investigated experimentally and numerically why these structures occur, what the influencing parameters are and how their influence on the roughness can be reduced, for both laser macro and laser micro polishing. It could be seen that the structures are influenced by the process parameters and the material of the workpiece. For a low surface roughness, the process parameters have to be adapted antithetically in some cases which means that it is not possible to prevent all structures at the same time and that surface structures will always occur during laser polishing. The process parameters must be adapted in such a way that all structures together lead to a surface roughness as low as possible.

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Mittels SLM hergestellte Bauteile weisen aufgrund der schichtweisen Herstellung aus pulverförmigem Material eine im Vergleich zu konventionell hergestellten Bauteilen große Oberflächenrauheit von Ra = 10-40 μm auf. Daher ist für viele Anwendungen eine aufwendige Nachbearbeitung zur Verbesserung der Oberflächenqualität notwendig. Ein alternatives Nachbearbeitungsverfahren von SLM-Oberflächen stellt das automatisierte Laserpolieren dar. Das Laserpolieren beruht auf dem Umschmelzen einer dünnen Randschicht und Glättung der Oberfläche infolge der Oberflächenspannung in der schmelzflüssigen Phase. Im Vergleich zu konventionellen Schleif- und Polierverfahren wird kein Material abgetragen sondern nur umverteilt. In dieser Veröffentlichung werden die ersten Ergebnisse zum Laserpolieren von mittels SLM hergestellten Oberflächen für die Werkstoffe Inconel 718 und ASTM F75 dargestellt. Durch Anpassung der Prozessparameter wird für Inconel 718 eine Rauheitsreduzierung von 99% erreicht, für den Werkstoff ASTM F75 kann die Rauheit um 97% reduziert werden

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The manufacturing of sheet metal parts or component edges often leads to burrs. Due to different requirements regarding the appearance, haptics, tribology et cetera the edges have to be deburred or rounded in a subsequent process. Especially for complex geometries, automated post-processing has been difficult up to now. Laser remelting is one possible solution. It is fully automated and suitable for most 3D geometries. During laser remelting the laser beam is focused on the surface, thus a thin surface layer up to 100 μm is melted. The surface tension in the liquid state is smoothing out the surface and the edge resolidifies rounded. The radius of the rounding is adjustable by the chosen process parameters, especially laser power PL and feed speed vfeed. Furthermore the resulting roughness and the gloss level are controllable via the process parameters. Typical processing speeds are 100 mm edge length per second. First studies with industry partners showed promising results. Laser remelting of push belts for the torque transmission in CVTs lead to an increase of fatigue strength by up to 200% which enables a higher torque.