15 October 2013 Interaction of N-FK5 and L-BAL35 optical glass with various carbide and other precision glass mold tooling
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Proceedings Volume 8884, Optifab 2013; 88841Y (2013) https://doi.org/10.1117/12.2035217
Event: SPIE Optifab, 2013, Rochester, New York, United States
Precision glass molding (PGM) is an optical manufacturing process used to hot press optical glass into a specified lens shape. This is done by taking the glass to a temperature above Tg and exerting force using an upper and lower mold. These molds will, together, give the pressed lens its shape. This study focuses on the high temperature interactions between the mold tooling material and two optical oxide glasses, Ohara’s L-BAL35 and Schott’s N-FK5. Flat molds were used to press flat glass work pieces at high temperature and force; key post process parameters such as sample and mold surface contamination using EDS and visible degradation via SEM were catalogued and analyzed. The molds used were bare tungsten carbide (WC) and silicon carbide (SiC) with an amorphous SiC chemical vapor deposition (CVD) coating. The results showed that raw WC molds suffered the most degradation including physical damage as well as chemical adherence and reaction. The Ti binder used in the WC as well as some the tungsten itself transferred to both glasses and caused a white reflective layer to appear on the molded glass surface. Severe damage was evident after only 2 pressing cycles with potassium from N-FK5 being the most prominent chemical contaminant. N-FK5 proved to be the more corrosive of the two glasses in all occasions. The SiC coated molds fared better in terms of degradation than the WC, however sticking of glass to mold was a problem.
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E. Koontz, E. Koontz, P. Wachtel, P. Wachtel, J. David Musgraves, J. David Musgraves, K. Richardson, K. Richardson, S. Mourad, S. Mourad, M. Huber, M. Huber, A. Kunz, A. Kunz, M. Forrer, M. Forrer, "Interaction of N-FK5 and L-BAL35 optical glass with various carbide and other precision glass mold tooling", Proc. SPIE 8884, Optifab 2013, 88841Y (15 October 2013); doi: 10.1117/12.2035217; https://doi.org/10.1117/12.2035217

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