Reliable Precision Tooling
Precision Glass Moulding and beyond
Work Package 1 – Reliable Precision Tooling
The goal of work package 1 was to develop a tool making process chain for the tools needed for precision glass molding, with particular emphasis on high reliability, high quality, short delivery times and long tool life times.
|The different steps for mold manufacturing, e.g. mold design including process simulation, pre and fine machining operations, mold coating and software development, were developed with a holistic view on the overall process chain.
A developed simulation tool imitates the molding process at high temperatures, enabling an immediate shrinkage error compensation in the range of 1 µm even for complex aspherical lenses.
|This does not only significantly increase the lens quality; it also reduces the production time dramatically. Typically, several iteration loops have to be accomplished in order to compensate geometrical deviations caused by thermal shrinkage. These iterations can be eliminated by applying the developed simulation tool (Partners: Fraunhofer IPT).|
|Ultra precision grinding and diamond turning technologies are the most important processes for mold manufacturing. Based on the development and evaluation of these technologies, optimal process strategies could be identified in order to manufacture different geometries in highest accuracies: rotational symmetrical spheres and aspheres, cylindrical lens arrays and diffractive structures. A surface roughness of 5 nm Ra and shape accuracy below 250 nm were achieved (Partners: Aixtooling, Fraunhofer IPT).|
|Mold coating is a decisive factor for the life time of a mold. Therefore, a nano-coating facility was established in order to produce optical coating with a thickness of approximately 300 nm. Tests with different coatings proved Pt/Ir to be the most suitable coating material for the application (Partners: CemeCon, Fraunhofer IPT, Fisba).|
|Furthermore, a nanocrystalline tungsten carbide with grain size of approximately 200 nm and almost no cobalt binder was developed as a substrate material for the molds. It has proven its potential and established its position on the mold manufacturing market (Partners: Ceratizit).
As the optical surface of the molds is extremely important, a reproducible polishing process was developed. This process is capable of reducing the surface roughness without deteriorating the shape accuracy (Partners: ingeneric, Fraunhofer IPT).