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Coalville, United Kingdom

Yu G.,Glyndwr University | Yu G.,University College London | Walker D.,Glyndwr University | Walker D.,University College London | And 3 more authors.
Applied Optics

The removal of mid-spatial-frequency errors is a challenging issue in most subaperture polishing technologies. A novel "grolishing" technology has been developed to deal with grinding errors of spatial wavelengths from 1 to 50 mm with the help of power spectral density analysis and filter theory. This grolishing process was implemented on Zeeko's IRP polishing machine, on which all the subsequent polishing was performed. This has greatly reduced the process time. Although different abrasive have been used, the process is self-contained. The process parameters have been optimized to leave an edge upstand of peak-to-valley of 1 μm over a width of 40 mm. © 2012 Optical Society of America. Source

Yu G.,Optic Glyndwr | Li H.,University College London | Walker D.,Optic Glyndwr | Walker D.,University College London | Walker D.,Zeeko Ltd.
Journal of the European Optical Society

BoX™ grinding technology has been adopted in our E-ELT segment process. The mid-spatial frequency features generated can be removed by several 'smoothing' processes. We have reported here a novel method that can smooth these features whilst avoiding edge down-turn. This process can be scaled up to E-ELT segment fabrication time-scale. It has been experimentally demonstrated that the surface quality is good enough for subsequent Zeeko form correction technology to achieve form specifications. Source

Li H.,Harbin Institute of Technology | Walker D.,University College London | Walker D.,Glyndwr University | Walker D.,Zeeko Ltd. | And 3 more authors.
Applied Optics

We present a simulation technique to predict tool influence functions (TIFs) based on the Precessions polishing process, which is driven by addressing mass fabrication of the European Extremely Large Telescope mirror segments. Precessions polishing requires accurate and predictable TIFs to optimize the multiple process parameters, particularly when sequential polishing runs are performed by different polishing tools. In this paper, the static and dynamic TIFs are simulated based on the Preston equation. The velocity distribution is calculated according to the geometry of the precession motion. The pressure distribution at the polishing spot is calculated by means of finite element analysis (FEA). The FEA result is validated by direct force measurement with a simulation error of 4.3%. The simulation results of TIFs are verified by an experiment that shows the residual errors are less than 5% for both static and dynamic TIFs. © 2013 Optical Society of America. Source

Beaucamp A.,Chubu University | Namba Y.,Chubu University | Charlton P.,Zeeko Ltd.
Applied Optics

The progressive transition from Excimer to extreme ultraviolet (EUV) lithography is driving a need for flatter and smoother photomask blanks. It is, however, proving difficult to meet the next-generation specification with the conventional chemical mechanical polishing technology commonly used for finishing photomask blanks. This paper reports on the application of subaperture computer numerical control precessed bonnet polishing technology to the corrective finishing of photomask substrates for EUV lithography. Full-factorial analysis was used to identify process parameters capable of delivering microroughness below 0.5 nm rms while retaining relatively high removal rates. Experimental results show that masks prepolished to 300-600 nm peak-to-valley (P-V) flatness by chemical/mechanical polishing can then be improved down to 50-100 nm P-V flatness using the automated technology described in this paper. A series of edge polishing experiments also hints at the possibility of increasing the quality area beyond the 142 mm square defined in the official EUV photomask specification. © 2014 Optical Society of America. Source

Axinte D.A.,University of Nottingham | Karpuschewski B.,Otto Von Guericke University of Magdeburg | Kong M.C.,University of Birmingham | Beaucamp A.T.,Chubu University | And 4 more authors.
CIRP Annals - Manufacturing Technology

With the increasing demands to generate complex parts on ever-more advanced, but difficult-to-cut materials, a group of technologies, generically called High Energy Fluid Jet Machining (HEFJet-Mach) has found niche applications that stimulated further development of science and technology in this field. Here HEFJet-Mach refers to unrestrained fluid jets used to remove and/or deform the workpiece material. The aim of this paper is to systematically present the recent developments of HEFJet-Mach from various perspectives: machine/system designs; modelling of both jet plumes and their interactions with the target surfaces; part quality including material integrity; supervision and control of the process; key aspects of machine maintenance and health and safety. © 2014 CIRP. Source

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