Walker, D.D., Atkins, C., Baker, I., Evans, R., Hamidi, S., Harris, P., Li, H., Messelink, W., Mitchell, J., Parry-Jones, M., Rees, P. and Yu, G. (2011) Technologies for producing segments for Extremely Large Telescopes. Proceedings of SPIE, 8126. ISSN 0277-786X

We describe progress on a novel process-chain being used to produce eight 1.4m hexagonal segments as prototypes for the European Extremely Large Telescope - a Master Spherical Segment as a reference, and seven aspheric segments. A new pilot plant integrates a bespoke full-aperture test-tower designed and built by OpTIC Glyndŵr, with a Zeeko 1.6m polishing machine. The process chain starts with aspherising hexagonal segments on the Cranfield BoX grinder, followed by smoothing, corrective-polishing and edge-rectification using the Zeeko CNC platform. The paper describes the technology and progress, and anticipates how the process-chain is expected to evolve through the seven segments to increase both process-speed and surface-quality.

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