Bavarian research group makes cutting edge advances in glass production

March 4, 2020 Company News7

Coherent Munich, Flabeg, Deggendorf Institute of Technology, University of Erlangen-Nuremberg Key Members

In the SmartCleave process, the beam source is applied in such a spatially precise and limited manner that there is no bulk heating of the glass, and therefore, no thermal damage to the material.

A multidisciplinary consortium of Bavarian companies and academic researchers are working together to improve the quality, extend the capabilities, and reduce the cost of fabricating glass components and products.

Key consortium members include laser system manufacturer Coherent Munich, hightechnology glass and mirror producer Flabeg, the Deggendorf Institute of Technology (DIT), and the University of Erlangen-Nuremberg (Friedrich- Alexander Universität, FAU), all Germany. While glass has been manufactured literally for millennia, its increasingly diverse use, particularly in displays in everything from automobiles to home appliances, is driving the need for glass with higher breakage resistance, as well as for manufacturing methods that can readily support production of complex curves and 3D, freeform shapes. This, in turn, necessitates technological advances in glass making and cutting processes, some of which have remained unchanged for centuries!

Gaining a Competitive Edge

The main focus of this consortium is on improving glass cutting technology. The traditional mechanical (scribe and break) technique for cutting glass isn’t adequate, particularly for touchscreen applications, for several reasons. First, mechanical cutting leaves residual stress in the glass edges which lowers its break resistance because, even when force is applied to the centre of a glass panel, any break usually initiates at the edge. Also, mechanical cutting produces microcracks, edge chips, and debris, necessitating post-processing (e.g., grinding, polishing). These additional steps increase production costs, the need for consumables (like water) and can create environmental concerns (especially the disposal of contaminated water). Finally, mechanical glass cutting can’t be easily applied to cutting of curved shapes or glass parts with complex 3D shapes. And, both of these capabilities are increasingly required, especially for displays and touch panels on automobiles, appliances, and handheld electronics. SmartCleave™ (the most effective form of filamentation cutting) is a sophisticated glass cutting process, developed by Coherent which utilizes a laser which produces ultra-short pulses (< 15 picoseconds or trillionths of a second). The very high focused laser power which is obtainable from this type of source can be applied in such a spatially precise and limited manner that there is no bulk heating of the glass, and therefore, no thermal damage to the material. The result is an extremely smooth edge, with no burrs, less cracks or breakouts, minimal edge stress, and completely eliminates the need for subsequent processing. Thus, all the additional grinding, washing, and drying steps, along with their energy consumption, time, cost and negative environmental impact, are absent. SmartCleave increases yields, improves quality, and lowers production costs. Plus, SmartCleave allows high-speed cutting of tight curves, without taper, and can be utilized to cut 3D shapes.

A Cooperative Research Project

The OptiGLas research project was initiated in 2015 by Flabeg, a company which continually strives to improve their product quality and reduce manufacturing costs by employing the latest technology. Flabeg wanted to explore the SmartCleave laser cutting method instead of mechanical separation and extend further its utility. In particular, the consortium identified several specific areas of exploration. The first was to investigate how SmartCleave parameters must be varied for use with different materials, in this particular case soda lime glass (in two different thicknesses), aluminosilicate glass, borosilicate glass, and glass ceramics. Of particular interest was borosilicate glass because it is proven among the experts to be the most challenging material to separate. Second, SmartCleave was originally developed primarily for cutting thin glass for touchscreen displays. Flabeg and Coherent agreed to extend the focal range of SmartCleave in order to cut thicker glass than it had been previously used with and to increase robustness. The development of new optical concepts for achieving this goal was necessary. Another goal was to refine the technology for cutting 3D shaped (not flat) parts. This requires accurate distance sensing during cutting to maintain laser focus at precisely the correct position. And, since there are always slight part-to-part variations and tolerances, this must be performed using active feedback. Flabeg recognized that several diverse types of expertise would be cooperatively required to achieve these goals. They initiated the project by first approaching Coherent for the critical laser and beam delivery knowledge. They then enlisted the Bavarian Ministry of Economic Affairs, Regional Development and Energy, who agreed to provide some of the financial support for the project. The Deggendorf Institute of Technology was involved in developing distance sensors and control methods for following part surface contours. The group at FAU contributed diagnostics. In particular, they used their scanning electron microscope and laser scanning microscope to characterize cut edge quality, and therefore filament shape, more precisely than had been done in the past. They estimated residual stresses using photo elasticity and vibrational spectroscopy. The research project is now in its third, and final, year. According to Dr. Alexander Roth, Vice President and General Manager Industrial Laser Systems at Coherent, “One of the most exciting outcomes to date has been the development of beam delivery optics which deliver improved cut quality and efficiency, resulting in the ability to cut glass that is 50% thicker than was previously possible.” The focus for the remaining year of the project is on achieving better results with borosilicate glass. However, given the success so far, Flabeg and the other team participants expect the use of SmartCleave to continue to expand as they push its capabilities and applications envelopes.

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