TY - JOUR
T1 - Brittle-ductile transition in shape adaptive grinding (SAG) of SiC aspheric optics
AU - Beaucamp, Anthony
AU - Simon, Peter
AU - Charlton, Phillip
AU - King, Christopher
AU - Matsubara, Atsushi
AU - Wegener, Konrad
N1 - Funding Information:
This work was supported by the JSPS Grant-in-Aid for Scientific Research No. 15H06320 from the Japan Society for the Promotion of Science. The authors also acknowledge the HEIDENHAIN Corporate Group for supporting the student exchange program between Kyoto University and ETH Zürich, which contributed to this collaborative research.
Publisher Copyright:
© 2016 Elsevier Ltd
PY - 2017/4/1
Y1 - 2017/4/1
N2 - Silicon carbide is a ceramic material with a desirable combination of high thermal and mechanical stability, making it ideal for optical application in aerospace and next generation lithography. It is however notoriously difficult to machine down to super-fine finish when the shape is other than flat or spherical. In this paper, we describe the application of a “semi-elastic” machining method called shape adaptive grinding (SAG), in which an elastic tool is combined with rigid pellets made of nickel or resin, to which super abrasives are bonded. A comprehensive model of the physical interaction between SAG tool and workpiece is proposed, and used to understand the mechanics driving brittle-ductile transition on ceramic materials such as SiC. Machining parameters adequate for optical finishing are then derived from the model and demonstrated on an aspheric silicon carbide workpiece, which was manufactured by reaction bonding and coated with a layer of pure SiC by chemical vapour deposition (CVD). Through SAG processing and final polishing, this aspheric mirror was improved from an initial form error of 40 µm down to 112 nm Peak-to-Valley, with no residual damage visible on the surface.
AB - Silicon carbide is a ceramic material with a desirable combination of high thermal and mechanical stability, making it ideal for optical application in aerospace and next generation lithography. It is however notoriously difficult to machine down to super-fine finish when the shape is other than flat or spherical. In this paper, we describe the application of a “semi-elastic” machining method called shape adaptive grinding (SAG), in which an elastic tool is combined with rigid pellets made of nickel or resin, to which super abrasives are bonded. A comprehensive model of the physical interaction between SAG tool and workpiece is proposed, and used to understand the mechanics driving brittle-ductile transition on ceramic materials such as SiC. Machining parameters adequate for optical finishing are then derived from the model and demonstrated on an aspheric silicon carbide workpiece, which was manufactured by reaction bonding and coated with a layer of pure SiC by chemical vapour deposition (CVD). Through SAG processing and final polishing, this aspheric mirror was improved from an initial form error of 40 µm down to 112 nm Peak-to-Valley, with no residual damage visible on the surface.
KW - Ductile grinding
KW - Optical finishing
KW - Shape Adaptive Grinding (SAG)
KW - Silicon carbide
KW - Ultra-precision
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U2 - 10.1016/j.ijmachtools.2016.11.006
DO - 10.1016/j.ijmachtools.2016.11.006
M3 - Article
AN - SCOPUS:85007557197
SN - 0890-6955
VL - 115
SP - 29
EP - 37
JO - International Journal of Machine Tool Design & Research
JF - International Journal of Machine Tool Design & Research
ER -