Minoru Ota
Kyoto Institute of Technology
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Publication
Featured researches published by Minoru Ota.
Advanced Materials Research | 2013
Vitchuda Lertphokanont; Takayuki Sato; Minoru Ota; Keishi Yamaguchi; Kai Egashira
Whirling Electrical Discharge Texturing (WEDT) was developed to create microstructures. It was thought that textured surface with low surface roughness could reduce friction coefficient on the sliding parts. In this research, surface quality was studied to evaluate the quality of WEDT textured surface. Surface quality was evaluated in terms of the surface roughness and surface integrity which were characterized by microstructure, composition and residual stress of the textured surface. The value of Rp and Rv of textured surface after finishing with improved finishing method were obtained as expected for low surface roughness to reduce friction coefficient. In addition, it was clarified that microstructure and composition of textured surface after texturing with WEDT and finishing with lapping-film depend on feed speed. Furthermore, the compressive residual stress was presented on WEDT textured surface and depended on feed speed. It was confirmed that good surface quality of textured surface could be obtained by WEDT.
Advanced Materials Research | 2012
Vitchuda Lertphokanont; Takayuki Sato; Minoru Ota; Keishi Yamaguchi; Kai Egashira
The authors developed Whirling Electrical Discharge Texturing (WEDT) in order to reduce friction coefficient of cylinder-shaped parts. In previous research, the authors verified fundamental characteristics of WEDT by observation of textured surface. It was found that a crater shape and texture-area ratio can be controlled by WEDT. The texture-area ratio depends on feed speed of tool electrode. In this research, crater depth, crater diameter, texture area ratio and total removal volume of craters were investigated to confirm characteristics of WEDT in detail. In addition, tungsten wire was used as a whirling shaft in order to improve stability of whirling phenomenon. Moreover, a textured surface was finished by lapping-film in order to remove protrusions around craters and reduce friction coefficient. As a result, it was verified that the texture-area ratio slightly increased with decreasing feed speed and it was confirmed that crater depth, crater diameter, and total removal volume of craters were also related to feed speed.
Materials Science Forum | 2016
Kai Egashira; Kenichi Kuriyama; Keishi Yamaguchi; Minoru Ota
There have been few reports on the drilling of microholes on rod end faces by cutting, which can be employed for fabricating micronozzles or microneedles. Such drilling was therefore attempted in the present study using a micro turn-milling machine with the tool and workpiece axes being parallel. The drilling was performed on the end faces of brass rods with cemented tungsten carbide micro-cutting tools processed by electrical discharge machining (EDM). As a result, a microhole 12 μm in diameter was successfully drilled using a 10-μm-diameter tool at a feed speed of 0.5 μm/s. The feed speed could be increased to 25 μm/s for a tool with a diameter of 20 μm and body length of 50 μm.
Materials Science Forum | 2016
Hirotaka Miwa; Takayoshi Katagi; Minoru Ota; Keishi Yamaguchi; Kai Egashira; Toshikazu Nanbu
Recently, diamonds have been utilized gradually for sliding parts and wear-resistant parts because of their excellent properties. The shape of diamond applied to these parts is not only plane but also arc-shaped inner surface. Therefore, development of diamond polishing technology is required. In this study, ultraviolet assisted polishing was thought to develop to polish polycrystalline diamond (PCD) on arc-shaped inner surface. The authors investigated effect of ultraviolet radiation on polishing efficiency and surface roughness. As a result, the surface roughness Ra of PCD showed less than 15 nanometers. In addition, polishing efficiency was improved about 30 percent due to ultraviolet assisted polishing.
Materials Science Forum | 2016
Keishi Yamaguchi; Minoru Ota; Kai Egashira; Hirotaka Miwa; Yoshiaki Onchi; Kenichi Tanada
Polycrystalline diamond (PCD) has excellent properties such as high hardness, high chemical inertness, high wear resistance and a low friction coefficient. Thus, it has been expected to be applied to used in various mechanical parts such as sliding parts. However, diamond is difficult to machine owing to its high hardness and chemical inertness. Therefore, a highly efficient and high-quality machining process is required for PCD. In this study, the authors developed fixed abrasive polishing tools for the mirror-like surface finishing of PCD that contain mechanochemical abrasive grains with diamond grains. As a result of fixed abrasive polishing experiments, it was clarified that a mirror-like surface can be obtained by fixed abrasive polishing using a tool containing SiO2 and diamond abrasives. Moreover, it was found that the removal efficiency can be increased under a high-temperature condition.
Key Engineering Materials | 2012
Atsushi Nakayama; V. Lertphokanon; Minoru Ota; Kai Egashira; Keishi Yamaguchi; Naomi Kawada; S. Kouno
The authors developed Whirling Electrical Discharge Machining (Whirling EDM) [1] with the feedback circuit to control gap distance between tool electrode and workpiece. It was found that the probability of discharge was increased by feedback circuit [2]. However, the motor rotational speed control conditions were not optimized and the machining characteristics were not clarified. In this paper, the rotational behavior of tool electrode in Whirling EDM was observed by high-speed camera, and it was considered that the influence of motor rotational speed control conditions on machining characteristics and the relationship between electrical conditions and machining characteristics. As a result, the discharge probability was able to be increased by decreasing range of motor rotational speed in feedback circuit. In addition, the machining characteristics of Whirling EDM which are influenced by electrical conditions were clarified.
Journal of Advanced Mechanical Design Systems and Manufacturing | 2012
Yasuhiro Mochimaru; Minoru Ota; Keishi Yamaguchi
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology | 2014
Kai Egashira; Ryokei Kumagai; Ryohei Okina; Keishi Yamaguchi; Minoru Ota
Journal of Advanced Mechanical Design Systems and Manufacturing | 2013
Vitchuda Lertphokanont; Minoru Ota; Hayato Yasui; Tooru Hamaoka; Tomoya Yabunaka
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology | 2016
Kai Egashira; Takuya Furukawa; Keishi Yamaguchi; Minoru Ota