Entwicklung eines Laserstrahlpolierverfahrens für Quarzglasoberflächen

Hecht, Kerstin GND

Ziel der Laserstrahlpolitur ist die schnelle, gleichmäßige, formerhaltende Glättung des Rauheitsprofils einer Quarzglasoberfläche. Der Laser wirkt dabei geometrieunabhängig, in der Art eines schnellen Subaperturwerkzeuges. Verschieden spanend bearbeitet Proben werden mittels Laserstrahlung poliert, wobei die Prozesseinflussgrößen, die Wechselwirkungen zwischen Laserstrahlung und Quarzglas sowie die Auswertung der Ergebnisse hinsichtlich Oberflächenqualität und Beeinflussung von Spannungen bzw. mechanischen Eigenschaften, die Untersuchungen und die Entwicklung eines industriell einsetzbaren Laserstrahlpolierverfahrens unterstützen. Experimentplanung, -durchführung und -auswertung erfolgen unter Anwendung statistischer Methoden. Die Temperatur wird während der Politur mit Pyrometer und Wärmebildkamera überwacht. Die Einsatzgebiete des Verfahrens liegen u. a. beim Polieren von 2D- und 2½D Bauteilen, Werkzeugformeinsätzen (Kunststoffverarbeitung) und in Teilbereichen optischer Komponenten.

The aim of laser beam polishing is to achieve an even surface finish in shortest possible time without changing the contour. Laser radiation acts as a topology-independent subaperture tool. The analyses of the influences towards the process, the interaction between laser radiation and fused silica as well as a comprehensive evaluation of the results concerning surface quality, manipulation of tensions and mechanical properties support the development of an industrial applicable laser polishing technology.All necessary basics are presented subsequent to the introduction. These include the general principle of laser beam polishing, the structure and properties of the applied laser systems as well as material properties and relevant material behavior of fused silica. A simulation of the laser beam polishing process as well as views on viscosity, surface tension and stock removal complete the fundamentals.Throughout the main part of the research working samples are pre-machined using several cutting technologies and then polished with laser radiation. The design, execution and evaluation of the experiments are carried out by means of statistic methods. These show that power and dwell time are the most significant factors for laser beam polishing. Temperature, as one of the most important parameters, is measured punctual or linear by pyrometer and 2-dimensional by infrared camera. In a temperature range from 1900…2100 °C a polishing process without stock removal is achieved. Measurements on a stylus instrument (2D and 3D) show, that laser beam polishing can reduce the initial roughness Ra from 0.1 … 0.4 µm down to 4 … 10 nm. The surfaces of the samples were observed by AFM-, SEM- and EDX-methods, hardness and bending strength analyses as well as tension gauge. Among other things it is indicated, that the laser beam polishing technology does not change the surface contour however a suitable cooling process to reduce tensions may be necessary. In contrast to the comparative mechanical finishing with a polishing rate of 228 s/cm² it is now possible to polish fused silica surfaces with 4,8 s/cm² by polishing with laser radiation.To extend the range of application of the laser beam polishing technology a piezo-scanner is brought from development via manufacturing up to testing, henceforth allowing a finish of 2½D-contours on fused silica surfaces.The graduate thesis ends with application examples, such as the successful grinding and laser beam polishing of injection mold inserts to process polymers for an industry-oriented research project.Further fields of application of this technology are polishing of 2D- and 2½D-parts, mold inserts for plastics processing and also particular areas of optical components.

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Zitierform:

Hecht, Kerstin: Entwicklung eines Laserstrahlpolierverfahrens für Quarzglasoberflächen. Ilmenau 2012. Universitätsverlag Ilmenau.

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