Fast manufacturing of E-ELT mirror segments using CNC polishing

C. Gray; I. Baker; G. Davies; R. Evans; N. Field; T. Fox-Leonard; W. Messelink; J. Mitchell; P. Rees; S. Waine; D. D. Walker; G. Yu

doi:10.1117/12.2023475

7 September 2013 Fast manufacturing of E-ELT mirror segments using CNC polishing

C. Gray, I. Baker, G. Davies, R. Evans, N. Field, T. Fox-Leonard, W. Messelink, J. Mitchell, P. Rees, S. Waine, D. D. Walker, G. Yu

Author Affiliations +

Proceedings Volume 8838, Optical Manufacturing and Testing X; 88380K (2013) https://doi.org/10.1117/12.2023475
Event: SPIE Optical Engineering + Applications, 2013, San Diego, California, United States

Abstract

We report on the first-ever demonstration of grinding and polishing full-size, off-axis aspheric, mirror segments as prototypes for an extremely large telescope, processed entirely in the final hexagonal shape. We first describe the overall strategy for controlling form and mid spatial frequencies, at levels in the vicinity of <10nm RMS surface. This relies first on direct CNC grinding of the base-form of these 1.4m segments, using the Cranfield BoX™ machine. The segments are then mounted on a custom designed (Optic Glyndwr Optoelectronic Engineering Group) three segment hydraulic support, and CNC polished on a Zeeko IRP 1600 machine using a variety of custom tooling. We overview the fullaperture and sub-aperture metrology techniques used to close the process-loop and certify quality, all of which operate with the segment in-situ on the IRP1600. We then focus on the pristine edge-definition achieved by the combination of tool-lift and smoothing operations; results never previously demonstrated on full-size pre-cut hexagonal segments. Finally, the paper discusses the feasibility of scaling the process to deliver 931 segments in seven years, as required for the E-ELT project.

Citation Download Citation

C. Gray, I. Baker, G. Davies, R. Evans, N. Field, T. Fox-Leonard, W. Messelink, J. Mitchell, P. Rees, S. Waine, D. D. Walker, and G. Yu "Fast manufacturing of E-ELT mirror segments using CNC polishing", Proc. SPIE 8838, Optical Manufacturing and Testing X, 88380K (7 September 2013); https://doi.org/10.1117/12.2023475

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available