title: Edges in CNC polishing: from mirror-segments towards semiconductors, paper 1: edges on processing the global surface.
abstract: Segment-edges for extremely large telescopes are critical for observations requiring high contrast and SNR, e.g. detecting exo-planets. In parallel, industrial requirements for edge-control are emerging in several applications. This paper reports on a new approach, where edges are controlled throughout polishing of the entire surface of a part, which has been pre-machined to its final external dimensions. The method deploys compliant bonnets delivering influence functions of variable diameter, complemented by small pitch tools sized to accommodate aspheric mis-fit. We describe results on witness hexagons in preparation for full size prototype segments for the European Extremely Large Telescope, and comment on wider applications of the technology.
authors.affiliation: Department of Physics and Astronomy, University College, Gower St, London, WC1E 6BT, UK. ddwlkr@aol.com
authors.forename: David
authors.initials: D
authors.lastname: Walker
authors.forename: Guoyu
authors.initials: G
authors.lastname: Yu
authors.forename: Hongyu
authors.initials: H
authors.lastname: Li
authors.forename: Wilhelmus
authors.initials: W
authors.lastname: Messelink
authors.forename: Rob
authors.initials: R
authors.lastname: Evans
authors.forename: Anthony
authors.initials: A
authors.lastname: Beaucamp
mesh_terms: D001256:Astronomy / Q000295:instrumentation*; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses