Ball-end Milling of Free-form Surfaces for Optical Mold Inserts

摘要

One of the objectives of the Transregional Collaborative Research Center SFB/TR4 of the Universities of Aachen and Bremen, Germany, and Stillwater, Oklahoma is the development of diamond machining processes for metal molds integrated in the process chain for economic mass production of complex optical elements. In this paper we will discuss the application of diamond ball-end milling for machining of free-form surfaces with small radii of curvature, the generation of NC-programs, requirements on tool alignment and a new high-resolution method for measuring surface slopes, local radii of curvature and figure error of free-form surfaces based on fringe reflection. Surface definition by NURBS is used throughout the process chain from the design stage to mold manufacture, injection molding and testing. The aim of the work presented in this paper is to minimize the number of iteration loops needed for achieving the required surface quality.