For the fabrication of highly precise glass optics, Precision Glass Molding (PGM) is the state-of-the-art replicative manufacturing process. However, the process efficiency is mainly determined by the service lifetime of the molding tools and, in particular, the performance of the protective coatings. Testing the lifetime in real molding machines is extremely cost and effort intensive. In a new testing facility the protective coating performance can be evaluated by systematically inducing tool wear under realistic process conditions. A high number of pressing cycles can be executed under minimal time and material effort, reducing the cost consumption for such coating validation tests significantly. In this paper, a fast method for evaluating the performance of coatings is provided. The machine concept and evaluation method are presented in comparison to the production conditions. Investigations are targeted on the similarities between tool wear in production and those induced in the testing facility. After inducing wear patterns on test specimens in the new facility, surface alterations are characterized with light microscopy. The results show similar degradation patterns as known from production, on the coated tools. The results presented show that the facility provides unique opportunity for optimizing coatings, but also glass compositions, for use in Precision Glass Molding.
Precision glass molding is the technology of choice for the production of complex-shaped optical components. Protective coatings can significantly extend the lifetime of the molding tools, but the coating properties have to be exactly customized for individual application conditions. The current biggest challenge is to ensure the reliability of newly developed coatings without resorting to extensive and expensive practical testing. However, the usual coating qualification methods either cannot be used or don't provide meaningful results. In this work a new three-tier, application-specific methodology for the qualification such coatings is presented. First, the basic characterization of coating properties is discussed, taking into account the specific characteristics of the coatings used for precision glass molding tools. In the second step, application-specific testing methods are devised, based on the analysis of the loads during glass molding. Finally, a new machine for testing the lifetime of the coated molding tools is proposed. Three case studies are presented where nanoscratch, nanoimpact and glass contact tests are performed with Pt-Ir, TiAlN, and CrAlN-coated samples in combination with various glass types, showcasing the usefulness of the proposed three-tier methodology.
Precision glass molding is the technology of choice for the production of complex-shaped optical components. Protective
coatings can significantly extend the lifetime of the molding tools, but the coating properties have to be exactly
customized for the individual application conditions, or else an improvement in the tool performance cannot be
guaranteed. The currently biggest challenge is to ensure the reliability of newly developed coatings without resorting to
extensive and expensive practical testing. However, the usual coating qualification methods either cannot be used or
don't provide meaningful results. In this work a new three-tier, application-specific methodology for the qualification
such coatings is presented.
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