Fraunhofer IPT has developed an innovative software concept for a digitalized glass optics production by means of precision glass molding and the belonging process chain. Thus, production data is used comprehensively and can be exploited conveniently for process development, production ramp-up and serial production. One striking innovation is the possibility to run part-specific simulation leading to a “Digital Twin” of every lens produced. The benefit for business is to enable advanced process developments, acceleration of production ramp-up and improved productivity in serial production. The concept is briefly introduced in conjunction with the current development state. Three possible use-cases for digitalized optics production are given and the paper concludes with further development steps necessary to implement the concept.
Precision glass molding is an established replicative manufacturing technology for mass production of glass optics. However, compared with injection molding of polymer optics, the production costs are still high, mainly due to longer cycle time. Two scale-up strategies of glass optic production can be applied to reduce the production costs per lens, namely multi-cavity molding and wafer scale molding. However, the efficiency of these two scaling strategies depends on a variety of factors. It is complicated to determine which scaling strategy should be used for the serial mass production of glass optics. In this study, the two scaling strategies will be introduced at both the technical and the economic level respectively. At the technical level, the molding environment, manufacturing accuracy, suitable lens geometries, and the technology readiness level of two scaling strategies will be compared. On the economic level, the productivity and production costs will be analyzed in detail. The goal is to develop a guideline for industry partners, which can be applied to determine the optimal scaling strategy. Furthermore, the concept of digitalized glass optics production, which is established by Fraunhofer IPT, may offer more potential to the scaling of glass optics compared with conventional optics production.
The use of chalcogenide glass in the thermal infrared domain is an emerging alternative to commonly used crystalline materials such as germanium. The main advantage of chalcogenide glass is the possibility of mass production of complex shaped geometries with replicative processes such as precision glass molding. Thus costly single point diamond turning processes are shifted to mold manufacturing and do not have to be applied to every single lens produced. The usage of FEM-Simulation is mandatory for developing a molding process for complex e.g. non rotational symmetric chalcogenide glass lenses in order to predict the flow of glass. This talk will present state of the art modelling of the precision glass molding process for chalcogenide glass lenses, based on thermal- and mechanical models. Input data for modelling are a set of material properties of the specific chalcogenide glass in conjunction with properties of mold material and wear protective coatings. Specific properties for the mold-glass interaction such as stress relaxation or friction at the glassmold interface cannot be obtained from datasheets and must be determined experimentally. A qualified model is a powerful tool to optimize mold and preform designs in advance in order to achieve sufficient mold filling and compensate for glass shrinkage. Application of these models in an FEM-Simulation “case study” for molding a complex shaped non-rotational symmetric lens is shown. The outlook will examine relevant issues for modelling the precision glass molding process of chalcogenide glasses in order to realize scaled up production in terms of multi cavity- and wafer level molding.
Precision Glass Molding (PGM) is a manufacturing method which enables cost efficient production of highly complex glass optics in medium to high quantities. The produced glass optics can be intended for applications in a spectral range from 180 nm ultraviolet to 13 μm thermal infrared. However, it is necessary to choose the glass type according to their intended task and wavelength domain. Typical glass types used for PGM are low Tg optical glasses. Fused silica and chalcogenide glasses expand applications to UV and IR. The use of different glass types entails a variation of the necessary temperature range in which the glass can be processed. The processing temperature of these glasses varies between 200 and 1400 °C. To ensure an economical processing, mold materials and mold manufacturing technologies are varied according to the task at hand. The application of PVD thin film coatings is one of the methods commonly used for prolonging the molds service lifetime. However, the specific coating has to be selected suitable for the glass type and mold material. To illustrate the differences in molding optical grade low Tg glass, fused silica and chalcogenide glass a representative process chain for PGM is described and peculiarities for each glass category is presented in regards to the state of the art. Finally an outlook on ongoing and future issues for applied research in the filed of PGM is given.