Ultra precision grinding of wafer scale

Manufacturing moulds for the wafer-scale replication of precision glass optics sets new demands in terms of grinding tool lifetime and the processes to be applied. This paper will present different approaches to grinding processes and kinematics to machine wafer-scale tungsten carbide moulds with diameters of up to 100 mm and more than 100 single aspheric cavities, each featuring form accuracies in the micron range. The development of these processes will be described and advantages and disadvantages of the approaches derived from practical tests performed on an ultra precision grinding machine (Moore Nanotech 350FG) will be discussed. Finally, a comparison between the developed processes is made where achieved form accuracies and surface topography are analyzed.