Elastic grinding wheels have previously been adopted for the development of the mirror surface finishing method for concave spheres. In this study, new conductive elastic grinding wheels, to which electrolytic in-process dressing (ELID) can be applied, are developed; the aim of the study is to address the challenge of maintaining a constant removal rate for rubber bond wheels. When ELID grinding is performed using a non-diene (isobutane isoprene rubber, IIR)-based wheel, a larger removal amount is achieved, and a higher-quality surface is also achieved compared to a diene (acrylonitrile-butadiene rubber, NBR)-based wheel. In addition, to investigate the effect of grinding wheel bond hardness on the removal amount and ground shape accuracy, grinding wheels with various levels of hardness are prepared by controlling the amount of carbon black contained in them, and grinding experiments are conducted. Thus, a larger removal amount is achieved using a harder grinding wheel, but the roughness of the ground surfaces deteriorates. Therefore, in practice, it is necessary to select an appropriate grinding wheel that can achieve both productivity and surface quality. Finally, to obtain a high-quality mirror finish on a concave spherical surface, ELID grinding is performed on the workpieces as is done for spherical lens molds. Thus, high-quality mirror surfaces with roughness Ra < 10 nm were generated. When the work pieces are ground using a grinding wheel of the same radius, excessive removal occurs at the edge of the concave spherical profile, decreasing the form accuracy. Numerical simulation demonstrates that chamfering of the grinding wheel is effective for improving the shape accuracy. The results of this study are expected to contribute to automation and cost reduction in the mirror-finishing process for concave molds.

1. [1] H. Ohmori and Y. Uehara, “Development of a Desktop Machine Tool for Mirror Surface Grinding,” Int. J. Automation Technol., Vol.4, No.2, pp. 88-86, 2010.
2. [2] H. Saito, H. Jung, E. Shamoto, S. Suganuma, and F. Itoigawa, “Mirror Surface Machining of Steel by Elliptical Vibration Cutting with Diamond-Coated Tools Sharpened by Pulse Laser Grinding,” Int. J. Automation Technol., Vol.12, No.4, pp. 573-581, 2018.
3. [3] M. Yoshimaru, Y. Fujita, T. Ito, M. Kouya, and H. Suzuki, “Development of Multi-Axis Cutting Method Using Non-Rotational Tool with Ultrasonic Vibration,” Int. J. Automation Technol., Vol.2, No.2, pp. 105-110, 2008.
4. [4] X. Tong, X. Wu, F. Zhang, G. Ma, Y. Zhang, B. Wen, and Y. Tian, “Mechanism and Parameter Optimization in Grinding and Polishing of M300 Steel by an Elastic Abrasive,” Materials, Vol.12, No.3, 340, 2019.
5. [5] K. Hara, H. Isobe, H. Yoshihara, A. Kyusojin, and K. Yanagi, “Ultrasonically Assisted Machining for Mirror Finishing of Die (2nd report) – Grinding Test with Self Electro plated Tool and Observation of Grinding Behavior –,” J. Jpn. Soc. Pre. Eng., Vol.73, No.4, pp. 460-464, 2007 (in Japanese).
6. [6] Y. C. Liou and W. L. Wang, “Lighting design of headlamp for adaptive front-lighting system,” J. Chin. Ins. Eng., Vol.30, No.3, pp. 411-422, 2007.
7. [7] M. Nagamachi, “Kansei engineering as a powerful consumer-oriented technology for product development,” App. Ergonomics, Vol.33, No.3, pp. 289-294, 2002.
8. [8] S. Wang, Q. Zhao, B. Guo, and Y. Pan, “Ultra-precision raster grinding of monocrystalline silicon biconical free-form optics using arc-shaped diamond grinding wheels,” J. Manuf. Proc., Vol.58, pp. 1064-1074, 2020.
9. [9] Y. Guangpeng and F. Fengzhou, “Fabrication of optical freeform molds using slow tool servo with wheel normal grinding,” CIRP Annals, Vol.68, Issue 1, pp. 341-344, 2019.
10. [10] E. S. Lee and S. Y. Baek, “A study on optimum grinding factors for aspheric convex surface micro-lens using design of experiments,” Int. J. Mach. Tools and Manuf., Vol.47, No.3-4, pp. 509-520, 2007.
11. [11] F. Chen, S. Yin, H. Huang, and H. Ohmori, “Fabrication of small aspheric moulds using single point inclined axis grinding,” Precision Eng., Vol.39, pp. 107-115, 2015.
12. [12] M. Saeki, T. Kuriyagawa, and K. Syoji, “Machining of aspherical molding dies utilizing parallel grinding method,” J. Jpn. Soc. Pre. Eng., Vol.68, No.8, pp. 1067-1071, 2002 (in Japanese).
13. [13] X. Wei, B. Li, L. Chen, M. Xin, B. Liu, and Z. Jiang, “Tool setting error compensation in large aspherical mirror grinding,” Int. J. Adv. Manuf. Technol., Vol.94, No.9, pp. 4093-4103, 2018.
14. [14] J. Xie, Y. W. Zhuo, and T. W. Tan, “Experimental study on fabrication and evaluation of micro pyramid-structured silicon surface using a V-tip of diamond grinding wheel,” Precision Eng., Vol.35, Issue 1, pp. 173-182, 2011.
15. [15] K. Inazawa, H. Ohmori, and N. Itoh, “Effects of O₂ Fine Bubbles on ELID Grinding Using Conductive Rubber Bond Grinding Wheel,” Int. J. Automation Technol., Vol.13, No.5, pp. 657-664, 2019.
16. [16] H. Tsukakoshi, N. Itoh, G. Itoh, A. Nemoto, T. Katoh, H. Ohmori, T. Matsuzawa, and H. Mizoguchi, “Development of conductive-rubber bonded wheel for ELID-grinding and its grinding characteristics – 2nd report: ELID mechanism of electro-conductive rubber bonded wheel,” J. Jpn. Soc. Abrasive Tech., Vol.52, No.6, pp. 339-342, 2008 (in Japanese).
17. [17] G. J. Han, J. H. Kim, M. A. Lee, S. Y. Chae, Y. H. Lee, and B. H. Cho, “Performance of a novel polishing rubber wheel in improving surface roughness of feldspathic porcelain,” Dental Materials J., Vo.33, No.6, pp. 739-748, 2014.
18. [18] X. J. Wu and X. Tong, “Study of trajectory and experiment on steel polishing with elastic polishing wheel device,” Int. J. Adv. Manuf. Technol., Vol.97, pp. 199-208, 2018.
19. [19] H. Ohmori, H. Kasuga, Y. Uehara, T. Kato, M. Mizutani, N. Itoh, A. Ezura, S. Kunimura, and Y. Kameyama, “Effect of Mirror Surface Grinding with ELID and its Characteristics,” J. Jpn, Soc. Precision Eng., Vol.79, No.4, pp. 278-286, 2013 (in Japanese).
20. [20] H. Ohmori, M. Mizutani, T. Kaneeda, N. Abe, Y. Okada, S. Moriyama, N. Hisamori, N. Nishimura, Y. Tsunashima, J. Tanaka, K. Kuramoto, and A. Ezura, “Surface generating process of artificial hip joints with hyper-hemispherical shape having higher smoothness and biocompatibility,” CIRP Annals, Vol.62, No.1, pp. 579-582, 2013.
21. [21] H. Ohmori, W. Lin, Y. Uehara, Y. Watanabe, S. Morita, T. Suzuki, and K. Katahira, “Nanoprecision Micromechanical Fabrication,” Int. J. Automation Technol., Vol.2, No.1, pp. 24-33, 2008.