Glass - Back to the Future!

Presenting Author:
Jens Bliedtner

article posted 21 March 2016

Jens Bliedtner studied precision engineering at the Friedrich-Schiller-University in Jena. He wrote his doctoral thesis in the fields of development of pulsed laser systems and special methods in macro material processing. Since 2000 Bliedtner has been a professor at the Ernst Abbe University of Applied Sciences in Jena and the head of the team production engineering and automation of production processes. Currently he is working in the research fields of optical technology and laser material processing.

Influences of Ultrasonic Assisted Grinding on Glass Materials

Jens Bliedtner*1, Matthias Rost1, Sebastian Henkel1, Stefan Schippel2, Stephan Anders2
1 University of Applied Sciences, Jena, Germany
2 LAYERTEC GmbH, Mellingen, Germany

This poster illustrates the research work in the field of ultrasonic assisted grinding of glass materials. First the kinematic principle of the procedure (rotation + longitudinal oscillation of the grinding tool) is demonstrated, which was initially examined in terms of frequency and amplitude. For this, different grinding tools were analysed by means of a laser vibrometer and a specific characteristic was determined for each tool, from which a process window could be defined. Thus it is possible to set amplitudes on the tool in 0.5 Ám steps. A process force reduction of the grinding procedure up to the maximum amplitude could be determined through subsequent in-situ measurements using a force measuring platform, which has positive effects on the processing of glass.

The centre of the poster presentation illustrates the ultrasound effects on the selected materials SiO2, N-BK7, F2 and Zerodur, showing the experimental designs and their results. These results are based on the examinations which were carried out by means of DoE in terms of roughness, edge breakouts as well as subsurface damages. Quartz glass, for example, turned out to be a material which can be processed very well by ultrasound. The subsurface damages (SSD) could thus be reduced by up to 75%. Higher roughness values, however, could be measured in contrast to the conventional grinding procedure. With N-BK7 a surface quality similar to quartz glass could be observed as well as an increase of the SSD. In contrast to that a lower roughness could be detected with F2 whereas the SSD remained almost the same. In terms of edge breakouts a reduction of over 20% could be measured with ultrasonic assisted grinding. Furthermore, the process strategy was optimised after finding out that a meandering processing causes a higher roughness and waviness than a circular processing.

Finally the poster shows the effects of ultrasound assistance on the processing of glass materials as well as its advantages and disadvantages compared to the conventional grinding procedure. The poster should give rise to discussions on the questions when the assistance of ultrasound is recommendable and which new geometries can be manufactured of glass.