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Proceedings Paper

New results from the Precessions polishing process scaled to larger sizes
Author(s): David D. Walker; Anthony T. H. Beaucamp; David Brooks; V. Doubrovski; Matthew D. Cassie; C. Dunn; Richard R. Freeman; Andrew King; M. Libert; Gerry McCavana; Roger Morton; David Riley; John Simms
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Paper Abstract

The Precessions process uses an inflated membrane-tool that delivers near-Gaussian polishing spots. The tool-motion over the part can be constructed to preserve an aspheric form whilst removing damage from preceding processes, or control the form through a tool-path prescribed by numerical optimization. The process has previously been validated on surfaces up to 200mm diameter and used extensively in industrial environments. In this paper we report the first trials on a substantially larger part - a 500mm diameter f/1 ellipsoidal mirror - as part of the UK’s technology-development for Extremely Large Telescopes. We draw attention to subtle problems that have arisen along the way. We also report on developing the process for free-form surfaces, in contrast to the axially-symmetric parts worked hitherto. The paper concludes with an assessment of the lessons learnt from the experiments, as they may impact on realization in a practical ELT segment fabrication facility.

Paper Details

Date Published: 24 September 2004
PDF: 10 pages
Proc. SPIE 5494, Optical Fabrication, Metrology, and Material Advancements for Telescopes, (24 September 2004); doi: 10.1117/12.553044
Show Author Affiliations
David D. Walker, Univ. College London (United Kingdom)
Zeeko Ltd. (United Kingdom)
Anthony T. H. Beaucamp, Zeeko Ltd. (United Kingdom)
David Brooks, Univ. College London (United Kingdom)
V. Doubrovski, Zeeko Ltd. (United Kingdom)
Matthew D. Cassie, Univ. College London (United Kingdom)
C. Dunn, Univ. College London (United Kingdom)
Richard R. Freeman, Zeeko Ltd. (United Kingdom)
Andrew King, Univ. College London (United Kingdom)
M. Libert, Zeeko Ltd. (United Kingdom)
Gerry McCavana, Zeeko Ltd. (United Kingdom)
Roger Morton, Zeeko Ltd. (United Kingdom)
David Riley, Zeeko Ltd. (United Kingdom)
John Simms, Zeeko Ltd. (United Kingdom)


Published in SPIE Proceedings Vol. 5494:
Optical Fabrication, Metrology, and Material Advancements for Telescopes
Eli Atad-Ettedgui; Philippe Dierickx, Editor(s)

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