Sub-surface damage issues for effective fabrication of large optics

Show simple item record Tonnellier, Xavier - Shore, Paul - Morantz, Paul - Baldwin, A. - Walker, D. - Yu, G. - Evans, R. - 2012-07-10T23:00:36Z 2012-07-10T23:00:36Z 2008-07-14T00:00:00Z -
dc.identifier.citation Tonnellier X, Shore P, Morantz P, et al., (2008) Sub-surface damage issues for effective fabrication of large optics. Proceedings of SPIE Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 23 June 2008, Marseille, France. Volume 7018
dc.identifier.isbn 978-081947228-1 -
dc.identifier.uri -
dc.description.abstract A new ultra precision large optics grinding machine, BoX®has been developed at Cranfield University. BoX®islocated at the UK's Ultra Precision Surfaces laboratory at the OpTIC Technium. This machine offers a rapidand economic solution for grinding large off-axis aspherical and free-form optical components.This paper presents an analysis of subsurface damage assessments of optical ground materials produced usingdiamond resin bonded grinding wheels. The specific materials used, Zerodur®and ULE®are currently understudy for making extremely large telescope (ELT) segmented mirrors such as in the E-ELT project.The grinding experiments have been conducted on the BoX®grinding machine using wheels with grits sizes of76 μm, 46 μm and 25 μm. Grinding process data was collected using a Kistler dynamometer platform. Thehighest material removal rate (187.5 mm3/s) used ensures that a 1 metre diameter optic can be ground in lessthan 10 hours. The surface roughness and surface profile were measured using a Form Talysurf. The subsurfacedamage was revealed using a sub aperture polishing process in combination with an etching technique.These results are compared with the targeted form accuracy of 1 μm p-v over a 1 metre part, surface roughnessof 50-150 nm RMS and subsurface damage in the range of 2-5 μm. This process stage was validated on a 400mm ULE®blank and a 1 metre hexagonal Ze en_UK
dc.language.iso en_UK -
dc.title Sub-surface damage issues for effective fabrication of large optics en_UK
dc.type Conference paper -

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