Mr. Hiroyoshi Yoko Profile

Hiroyoshi Yoko

Senior Expert at Toshiba Machine Co Ltd

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Proceedings Article | 18 August 2005 Paper

New mold manufacturing techniques

Chris Hall, Marc Tricard, Hiroshi Murakoshi, Yoshihiro Yamamoto, Kunitaka Kuriyama, Hiroyoshi Yoko

Proceedings Volume 5868, 58680V (2005) https://doi.org/10.1117/12.621097

KEYWORDS: Polishing, Magnetorheological finishing, Silicon carbide, Carbon, Manufacturing, Surface finishing, Glasses, Surface roughness, Tungsten, Magnetism

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Typically, optical molds have been made from silicon carbide (SiC) or tungsten carbide (WC). Magnetorheological Finishing (MRF) polishing results of SiC and WC molds will be reviewed. Impressive figure corrections have been demonstrated on both types of materials. The roughness performance of CVD-SiC, WC and binderless WC will be compared. However, the hardness and polycrystalline nature of these materials make them difficult to manufacture. In this paper we report positive initial results using an alternate mold material, glassy carbon. Test samples have been ground, pre-polished and finish polished to a 38 nm surface figure peak-to-valley (PV) and a 6 Å rms surface roughness, with improved cycle times versus SiC and WC. Glassy carbon is a promising mold material candidate as an amorphous material of lower hardness. The lower hardness leads to more effective diamond grinding process and results in a better surface rms roughness following MRF. After reviewing key material properties of glassy carbon material, this paper will describe some collaborative activities between Toshiba Machine Co., Ltd. and QED Technologies (QED) to manufacture representative examples of glassy carbon. Details of the grinding, pre-polishing and final polishing process will be provided along with the resultant metrology results after key steps. Molding experiments based on these developments will also be presented.

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