Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 35, Issue 78
Displaying 1-5 of 5 articles from this issue
  • Masahiko HIHARA
    2001 Volume 35 Issue 78 Pages 1-11
    Published: March 30, 2001
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
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  • Takeo TAMURA, Satoshi MATSUMOTO
    2001 Volume 35 Issue 78 Pages 12-18
    Published: March 30, 2001
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Heat-affected zones (HAZs), in which there are many cracks and microcraters, are generated by electrical discharge machining (EDM) of cemented carbides. These defects cause a substantial decrease in the strength of the materials. As one of the countermeasures, HAZs can be removed by polishing, which is dependent on hand finishing. However, it is difficult to remove HAZs completely through polishing. At present, a polishing operator subjectively evaluates whether defects such as cracks exist on a polished surface based on the degree of brilliance of the polished surface. In this study, the relationship between the reflectivity of the polished surface and the transverse rupture strength (IRS) was experimentally examined based on the assumption that polishing to a quasi-mirror-finish surface is not necessarily accompanied by recovery of the strength of the material. Our results showed that the reflectivity of the quasi-mirror-finish surface with surface roughness of 0.2μm Ry is 3-4 percent lower than that of a mirror-finish surface with surface roughness of less than 0.1μm Ry. The IRS ratio of a quasi-mirror-finish surface is 0.7, and that of an electrical discharge machined surface is 0.6 compared with 1.0 for a mirror-finish surface. Thus, we observed that the reflectivity of the quasi-mirror-finish surface is near that of the mirror-finish surface, and that the IRS of the quasi-mirror-finish surface is near that of the electrical discharge machined surface.
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  • Shin-ichiro KUBOTA, Yoshiyuki UNO, Hirokazu KURIBAYASHI, Seiichi YOKOM ...
    2001 Volume 35 Issue 78 Pages 19-25
    Published: March 30, 2001
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    This paper deals with fine deep boring of carbide alloys. Fine deep boring by EDM is superior for obtaining a qualitatively machined shape and high surface integrity compared to conventional processes. However, it is difficult to obtain a microhole smaller than 100μm in diameter with an aspect ratio larger than 5, because of remaining bubbles and debris in the small gap between the electrode and workpiece which cause unstable machining. A new fine boring method is proposed in which EDM and laser beam machining are combined. First, a penetrating prehole is machined with a YAG laser. In the next process, micro-EDM boring is carried out on the prehole. By removing the bubbles and debris through the prehole, it is possible to maintain stable EDM. With these two successive processes, a fine deep hole is obtained. The hole made by this method has a good roundness and a high aspect ratio that cannot be achieved using only the EDM process. We applied this method to a superfine grain carbide alloy which is widely used for precise metal molds and cutting tools. The main results of this study are as follows. (1) Using the combined process of EDM and LBM, ∅160μm holes were successfully machined through a 2-mm-thick superfine grain carbide. (2) It is possible to remove the bubbles and debris efficiently by suction flow through the prehole. (3) In the case of EDM boring with a prehole, electrode wear mainly occurs on the side of the electrode. (4) For a 1-mm-thick workpiece, it is possible to bore a microhole with a diameter of 100μm and an aspect ratio of 10.
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  • Toshio MORO, Akihiro GOTO, Naotake MOHRI, Nagao SAITO, Hidetaka MIYAKE ...
    2001 Volume 35 Issue 78 Pages 26-33
    Published: March 30, 2001
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    A surface modification technology with electrical discharge machining has been applied to cutting tools, molds and dies. A Ti-based powder composite structure electrode is used in this method, a high-speed modification technology which can generate a thin and hard layer on a substrate. In this report, experiments using a TiH2 green compact electrode are described. The results of the experiments are as follows: 1) The piled layer is functionally graded in atomic content and hardness which reaches 3000HV at the top of a 10-μm-thick layer in spite of voids involved. 2) The thickness and hardness are uniquely determined by the supplied energy density. The wear length of the electrode is reduced according to the decrease of its area due to the bubbles in the gap region. 3) The layer grows rapidly at the beginning of machining and then its hardness increases. After the maximum piling rate, the hardness decreases owing to the change of thermal properties of the piled layer.
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  • Automatic manufacturing of punch for the lead flame mold
    Makoto IKEGAME
    2001 Volume 35 Issue 78 Pages 34-38
    Published: March 30, 2001
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
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