Precision Mold Manufacturing for Polymer Optics

Abstract

Ophthalmic lenses, sensors, and sunglasses, among other things, are commonly made of polymer materials. Therefore, polymer optics is a growing market mainly for medium quality but also for precision optics. Polymer optics are usually produced in an injection molding process. Due to high quality requirements on the final product, the manufacturing process of the molds has to be very accurate and precise. Thus the master tool has to be fabricated to a high quality with regard to shape accuracy and roughness. The focus of this article is on the process chain for the fabrication of molds for polymer optics and the finite element simulation of this process. The typical existing process chains contain steps like nickel plating, diamond machining and manual polishing. Some of these steps are expensive and require very experienced staff. In the new process chain, an industrial robot with special tools is used for lapping and polishing. Robot polishing replaces the former nickel plating, diamond machining, and manual polishing steps. The lapping/polishing process was newly developed to achieve appropriate results. Different tool materials, polishing agents, and process parameters have been tested and compared to the finite element simulation to obtain excellent results directly on different mold materials.