Published papers

In recent years, Fluid Jet Polishing (FJP) has been studied for its potential as a finishing method on optical lenses, mirrors and molds for a number of materials, such a glass and nickel. In this paper, the surface integrity of binderless tungsten carbide after polishing by FJP was studied experimentally. Two aspects in particular were focused on: (1) identifying process conditions under which grain boundaries may dislocate (thus leading to unintentional loss of grains from the substrate) and (2) identify process conditions under which abrasive particles may become embedded into the substrate, in order to prevent surface contamination. © 2014 The Authors. Published by Elsevier B.V.

Focusing short wavelength radiations such as Extreme Ultra-Violet (EUV) and X-rays can be accomplished by assemblies of reflective aspheric optics. Application of such systems ranges from research in X-ray astronomy and microscopy, to semiconductors production by EUV lithography. But such optical surfaces require finishing to very low levels of micro-roughness, in proportion to the wavelength of incoming radiation. In this paper, recent advances in super fine finishing technologies (capable of achieving micro-roughness below 0.5 nm rms) for aspheric and freeform optical surfaces are presented. The paper deals with both ultra-precision grinding and polishing technologies, with the performance and advantages/disadvantages of each method being discussed, and examples of applications provided.

There is a strong need for a new system to shorten the drill fabrication time, to reduce material costs, and to create new drill configurations by predicting their characteristics. Current drill shape prediction systems cannot comprehensively treat drill cross-section shape including the cutting edge, groove and so on, mathematically. Modelling would become more practical if the drill specification was mathematically formulated. This study reports the development of a system to predict not only cross-section shape but also various parameters from grinding wheels used in drill fabrication.

Zeeko's Precession polishing process uses a bulged, rotating membrane tool, creating a contact-area of variable size. In separate modes of operation, the bonnet rotation-axis is orientated pole-down on the surface, or inclined at an angle and then precessed about the local normal. The bonnet, covered with standard polishing cloth and working with standard slurry, has been found to give superb surface textures in the regime of nanometre to sub-nanometre Ra values, starting with parts directly off precision CNC aspheric grinding machines. This paper reports an important extension of the process to the precision-controlled smoothing (or 'fining') operation required between more conventional diamond milling and subsequent Precession polishing. The method utilises an aggressive surface on the bonnet, again with slurry. This is compared with an alternative approach using diamond abrasives bound onto flexible carriers attached to the bonnets. The results demonstrate the viability of smoothing aspheric surfaces, which extends Precessions processing to parts with inferior input-quality. This may prove of particular importance to large optics where significant volumes of material may need to be removed, and to the creation of more substantial aspheric departures from a parent sphere. The paper continues with a recent update on results obtained, and lessons learnt, processing free-form surfaces, and concludes with an assessment of the relevance of the smoothing and free-form operations to the fabrication of off-axis parts including segments for extremely large telescopes.

© 2017 The Authors. Published by Elsevier. In recent years, miniaturization and light weightedness are required for industrial products as well as high functionality. Thin plates are appropriate in terms of weight, however they are usually difficult to produce only by cutting operation due to the deformation by cutting force or vibration of the thin plate. This study deals with the machining of a twisted thin plate, whose height, width and thickness are 50 mm, 30 mm and 0.1 mm respectively, without using any auxiliary tool. Such a thin plate with high aspect ratio is easily broken down by the cutting force. Thus, the machining of thin plate with high aspect ratio is approached by devising a tool path strategy in this study. As the cutting force easily allows for deformation of twisted thin plate with high aspect ratio, two methods are devised with regard to the generation of the tool path, the method with a supporting frame and the peeling method so that the stiffness of the plate can be kept high. Then, the actual machining of thin plate with high aspect ratio, made of aluminum alloy, was realized without any breakage. As a result, it is found that such cutting method allows the possibility of fabricating such a twisted thin plate.

Electroless Nickel (ENi) and binderless Tungsten Carbide (WC) are widely used to make replication moulds for optics ranging from consumer camera lenses to high-accuracy X-ray mirrors. Aspheric shape generation is generally performed by diamond turning in the case of Nickel, and micro-grinding in the case of Tungsten Carbide. Both machining methods fail in general to meet the ultra-precision criteria required by an increasing number of applications. A 7-axis CNC machine equipped with sub-aperture fluid jet and precessed bonnet polishing technology was used to develop deterministic finishing processes on both Electroless Nickel and Tungsten Carbide. Corrective polishing to less than λ/20 (<31nm PV) form error can be achieved, as well as the ability to smooth surface texture down to 1nm Ra or less.

© 2017 The Authors. Published by Elsevier. With increasing global competition, reduction in the machining cost is the most important issue after machining quality. The machining cost consists of various factors. Among them, the cost of cutting tool holds the first place. The reduction or suppression of tool cost results in an increase in competitive force. This study aims at lengthening the tool life, while decreasing the tool wear. Therefore, the cutting edge of a ball end mill is swung around its center by continuously changing the tool axis vector so that the cutting edge may be uniformly used. Taking account of the width of the flank wear of the ball end mill and the surface roughness of the workpiece in the finishing process, the study proposes an appropriate tool attitude and a suitable tool swing rate of the ball end mill. As a result, the machining method with the tool axis vector continuously swung allows for decreasing tool wear due to its dispersion across the entire tool surface. The proposed method can be applied to machining of workpieces with sculptured faces. From the experimental results, it is found that the proposed idea has the potential of saving tool cost.

ナノ粒子を用いた超微細ブラストの研究を行っている．自然状態ではナノ粒子は凝集粒子を形成し，その粒径のばらつきは精密仕上げに要求される砥粒の粒径分布より大きい．本研究では，粒子間の付着力を上回る外力を加えることで凝集粒子の平均径と分布幅を小さくする方法を提案する．有限要素解析と実験により，超音波振動と静電力を同時に印加すると粒径分布が改善するとわかったが，凝集粒子は完全には分離しなかった．

In recent years, the drill used to make holes is expected to exert both high machining accuracy and good processing capability. In order to meet those requirements, it is necessary to develop a new drill shape with good properties requested by designers. There is a strong need for a new system to shorten the drill fabrication time, to reduce material costs, and to create new drill configurations by predicting their characteristics. Current drill shape prediction systems cannot comprehensively and mathematically treat drill cross-section shape including the cutting edge, groove and so on. The prediction system would become more practical if the drill specification was mathematically formulated. This study reports the development of a system to predict not only the cross-sectional shape but also various parameters from the information of grinding wheels used in drill fabrication. Furthermore, this study proposes the new system to predict the most suitable grinding wheel setting from the grinding wheel shape and some drill specifications as the reverse process.

There is no actual plan to make next-generation X-ray telescope after ASTRO-H project. We are making aspheric fused silica molds for NASA/GSFC that launched hard X-ray telscope made of LCD sheet glasses last June. But the X-ray mirrors were conical shape, not accurate aspheric shape. We intend to make aspheric molding dies of 100 nm accuracy.

本研究では，走査型原子間力顕微鏡を用いて，ナノスケールでの単純押し込み実験と，単粒子による研磨加工の模擬実験を行った．また，準連続体解析と実験結果を比較することで，解析法の妥当性を検証した．その結果，単純押し込み実験においては，解析結果が実験結果と一致することがわかった．一方，単粒子研磨加工実験では，金属短針の摩耗という実験における問題点が明らかとなった．

Electroless Nickel (ENi) and binderless Tungsten Carbide (WC) are materials widely used in industry to make replication moulds for precision optics, with applications ranging from consumer camera lenses to high accuracy X-ray mirrors. The aspheric shape generation is generally performed by diamond turning in the case of Nickel, and microgrinding in the case of Tungsten Carbide. However, both machining methods fall short from meeting the ultra-precision criteria required by an increasing number of applications, because of insufficient form accuracy and the frequency content of the machining marks they leave on the surface. It is thus commonly observed in industry that moulds need to be subsequently polished by hand, a usually slow and human resource intensive operation. The Zeeko 7-axis CNC machine, equipped with sub-aperture fluid jet and precessed bonnet polishing technology, has been used to develop deterministic finishing processes on both Electroless Nickel and Tungsten Carbide. Corrective polishing to less than λ/20 (<31nm PV) form error can be achieved, as well as the ability to smooth surface texture down to 1nm Ra or less, in a time efficient manner. © 2011 SPIE.