New Results from the Precessions Polishing Process Scaled to Larger Sizes

D. D. Walker, A. T.H. Beaucamp, D. Brooks, V. Doubrovski, M. Cassie, C. Dunn, R. Freeman, A. King, M. Libert, G. McCavana, R. Morton, D. Riley, J. Simms

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

46 Citations (Scopus)


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.

Original languageEnglish
Title of host publicationOptical Fabrication, Metrology, and Material Advancements for Telescopes
EditorsEli Atad-Ettedgui, Philippe Dierickx
Number of pages10
ISBN (Print)9780819454263, 0819454265
Publication statusPublished - 24 Sep 2004
Externally publishedYes
EventSPIE Astronomical Telescopes + Instrumentation - Glasgow, United Kingdom
Duration: 21 Jun 200425 Jun 2004

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceSPIE Astronomical Telescopes + Instrumentation
Country/TerritoryUnited Kingdom


Dive into the research topics of 'New Results from the Precessions Polishing Process Scaled to Larger Sizes'. Together they form a unique fingerprint.

Cite this