Improvement of Surface Figure in the Polyurethane Pad Continuous Polishing Process

Abstract:

Primary factors determining surface figure of optics, including the velocity and pressure distributions, have been analyzed and improving methods provided accordingly for the pad continuous polishing (CP). With a septum on the exterior of the workpiece pre-pressing the pad, the inevitable depression on the edge of the workpiece incurred by the elastic response of the pad has been relieved obviously. By introducing the driving wheel system, the rotation speed of the septum & workpiece can be regulated and adjusted to that of the lap/pad, which produces a uniform velocity distribution on the polishing surface. Diamond conditioners with ring & disk patterns are employed to planarize the annular polyurethane pad and hence uniformise the pressure distribution on the workpiece/pad interface. Polishing experiments (Fused silica flat, 320 mm in diameter x 30 mm thick) conducted on the typical CP machine have demonstrated advantages of these methods.

• Periodical: Applied Mechanics and Materials (Volume 319)
• Pages: 107-112
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.319.107
• Online since: May 2013
• Authors: De Feng Liao, Heng Zhao, Zhi Gang Yuan, Rui Qing Xie
• Keywords: Diamond Conditioners, Driving Wheel System, Pad Continuous Polishing, Septum

References

[1] M. L. Spaeth, K. R. Manes, C. C. Widmayer, W. Williams, P. A. Whitman, and M. Henesian, "The National Ignition Facility Wavefront Requirements and Optical Architecture," UCRL-CONF-I 55442 (2004).

DOI: 10.1117/12.538478

[2] J. E. Yellowhair, "Advanced Technologies for Fabrication and Testing of Large Flat Mirrors," Ph.D. Dissertation, Univ. of Arizona, (Tucson, Arizona, 2007).

[3] R. A. Jones, "Optimization of computer controlled polishing," Appl. Opt. 16, 218-224 (1977).

[4] S. D. Jacobs, D. Golini, Y. Hsu, B. E. Puchebner, D. Strafford, I. V. Prokhorov, E. M. Fess, D. Pietrowski, and W. I. Kordonski, "Magnetorheological finishing: a deterministic process for optics manufacturing," Proc.SPIE 2576, 372-382 (1994).

DOI: 10.1117/12.215617

[5] H. R. Kaufman, P. D. Reader, and G. C. Isaacson, "Ion Sources for Ion Machining Application," AIAA Journal. 15, 843-847 (1977).

DOI: 10.2514/3.60716

[6] C. R. Dunn, and D. D. Walker, "Pseudo-random tool paths for CNC sub-aperture polishing and other applications," Optics Express. 16, 18942-18949 (2008).

DOI: 10.1364/oe.16.018942

[7] F. Cooke, N. Brown, and E. Prochnow, "Annular lapping of precision optical flatware," Opt. Eng. 15, 450-458 (1976).

DOI: 10.1117/12.7972011

[8] R. R. Berggren and R. A. Schmell, "Pad polishing for rapid production of large flats," SPIE 3134, 252-257 (1997).

DOI: 10.1117/12.295131

[9] M. A. Nichols, "Summary of Synthetic Lap Polishing Experiments at LLNL, FY'95," UCRL-JC-146026 (2001).