Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 40, Issue 95
Displaying 1-6 of 6 articles from this issue
  • - Effect of Multi Craters Formation on Surface Roughness-
    Keigo NISHIMOTO, Takeo IKAI, Kiyoto HASHIGUCHI, Yoshiyuki UNO
    2006 Volume 40 Issue 95 Pages 139-145
    Published: November 30, 2006
    Released on J-STAGE: August 22, 2008
    JOURNAL FREE ACCESS
    We propose a new electrical-discharge machining method, in which an isolated bundled electrode is used for a high removal rate without deteriorating the surface finish. This phenomenon is due to the formation of small multicraters by a single pulse, even in a high-energy discharge. The effects of the discharge conditions on crater shape in a single discharge and on surface roughness in multiple discharges were experimentally investigated. The experimental analysis clarified that the use of isolated bundled fine-wire electrodes results in superior surface roughness compared with the use of a solid electrode.
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  • Zhanbo YU, Yoshihiro WATANABE, Yoshiji UI, Nobuhiro NAKAJIMA, Sadao SA ...
    2006 Volume 40 Issue 95 Pages 146-153
    Published: November 30, 2006
    Released on J-STAGE: August 22, 2008
    JOURNAL FREE ACCESS
    In this study, we mainly use cemented carbide hard alloy material for investigating a new application of wire electric discharge machining (WEDM) under air conditions. As a result, we find that cemented carbide can be machined by wire electric discharge under air conditions. From the experimental results for this material, it can be concluded that the machining rate increases when we use wire material with a high melting point and a high tensile strength at a high temperature, such as tungsten wire. It is also found that feed rate of the wire can influence the machining rate and an optimal feed rate exists. We found also that the machining rate can be increased in dry wire electric discharge machining when using a pulse waveform with a low peak current and a long pulse for the same pulse energy as compared with a high peak and a short pulse current. Moreover, owing to the shorter gap of air machining, it is possible to carry out a micromachining process, which is difficult to realize in liquid machining.
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  • Takayuki TANI, Hiromitsu GOTOH, Yasushi FUKUZAWA, Naotake MOHRI
    2006 Volume 40 Issue 95 Pages 154-161
    Published: November 30, 2006
    Released on J-STAGE: August 22, 2008
    JOURNAL FREE ACCESS
    High-hardness structural materials such as fine ceramics and cemented carbides are widely used as materials in industrial tools, electronic components and precision instruments. However, these materials are difficult to machine through conventional machining processes because of their high hardness and brittleness. Electrical discharge machining (EDM) is used for the precision machining of hard materials. Recently, it has also be used for machining insulating ceramics by the assisting electrode method. In the EDM of cemented carbides and conductive ceramics, the machining rate affects their mechanical properties and chemical reactions with discharge phenomena. When insulating ceramics are machined by EDM, their surface becomes covered with an electrical conductive layer formed by cracked carbon. The conformation of this layer differs according to the ceramics type, and affects the machining characteristics. In this paper, we describe the EDM characteristics of high-hardness structural materials such as electrical conductive ceramics, cemented carbide and insulating ceramics.
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  • - Efforts at complex shape machining -
    Hiromitsu GOTOH, Takayuki TANI, Yasushi FUKUZAWA, Naotake MOHRI
    2006 Volume 40 Issue 95 Pages 162-168
    Published: November 30, 2006
    Released on J-STAGE: August 22, 2008
    JOURNAL FREE ACCESS
    The term “ceramics” is broadly used in industry nowadays, referring to a wide spectrum of materials with greater hardness, chemical stability, greater resistance to wear and high-temperature resistance to corrosion. To apply these functions to ceramic products, it is necessary that ceramics are machined into complex shapes. WEDM is generally known as a machining method for making a complex ruled surface by wire scanning. In this study, we machined insulating Si3N4 ceramics by WEDM. We discuss the effects of wire tension on machining characteristics in the machining of insulating ceramics. Machined shapes are also investigated in relation to the machining accuracy of a rod extracted from a thick plate and sliced thin plates.
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  • - Removal of Passive Film Using Honing Stick and High-Efficiency Surface Finishing -
    Akira OKADA, Atsushi HASHIMOTO, Yoshiyuki UNO, Shoichi YAMAMOTO, Masas ...
    2006 Volume 40 Issue 95 Pages 169-176
    Published: November 30, 2006
    Released on J-STAGE: August 22, 2008
    JOURNAL FREE ACCESS
    Honing has been widely applied to engine cylinders and hydraulic cylinders, since not only surface roughness but also the roundness and straightness of the hole can be improved by the process. However, in the case of a surface roughness less than 1μmRz, burrs formed by the abrasives used significantly affect the surface roughness and make it difficult to attain smoother surfaces. In our previous paper, the electrochemical internal-surface finishing of a small hole using a honing machine and a soluble fluid after honing was proposed for accurate and efficient finishing. Experimental results clarified that passive-film generation on the machined surface could be prevented by mixing an inverse electrolytic current with the normal one, and that the surface roughness could be reduced because only convex parts on the machined surface were selectively removed, even when the soluble fluid used in honing is an electrolyte. In this study, honing sticks were used to remove the passive-film during electrochemical finishing after honing. Also, optimum machining conditions were discussed to attain higher-efficiency surface finishing. As a result, the internal surface roughness was decreased to less than 0.5μmRz in only 10sec.
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  • Takeo TAMURA, Kenichi YAMAYA
    2006 Volume 40 Issue 95 Pages 177-183
    Published: November 30, 2006
    Released on J-STAGE: August 22, 2008
    JOURNAL FREE ACCESS
    As a method for processing cemented carbide with a fine hole, wire electrical discharge machining (WEDM) is generally used. However, surface defects such as cracks and micro-craters are generated on the inner wall of the hole by WEDM. It is desirable that these surface defects are removed. Lapping of the inner wall of the hole has usually been performed by finishing by hand using a bar daubed with diamond paste. However, this method requires considerable time to finish the hole. A recently developed high-speed flow finishing method seems to give an excellent performance in polishing the cemented carbide with a fine hole. However, it is difficult for the surface defects to be completely removed in this method. Thus, a combined polishing method, for the purpose of completely removing the surface defects, was developed in this study. This method combined the surface modification using an oxidizing treatment with flow polishing using an abrasive. As a result, the surface defects generated by WEDM could be completely removed in only 10 minutes by this combined polishing. Thus, this combined polishing method will be effective for polishing cemented carbide with a fine hole.
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