Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 26, Issue 52
Displaying 1-5 of 5 articles from this issue
  • Improvement of machining accuracy of corner parts in finish-cutting
    Takuji MAGARA, Tsuyoshi YATOMI, Hisashi YAMADA, Kazuhiko KOBAYASHI
    1992 Volume 26 Issue 52 Pages 1-15
    Published: July 31, 1992
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    This paper descrives a detaled research investigation on improvement of machining accuracy of corner parts in finish-cutting of Wire-EDM.
    In finish-cutting (second cutting), forces by discharge are small in comparison with those of rough-cutting (first cutting) because of its small energy of discharge, so that the reason of corner shape errors may not be bends of wire electrodes. From this point of view, it is reasonable that there are some other reasons for corner shape errors in finish-cutting.
    In this paper, the machining feed speed at coner part can be simulated by concidering changes of removal thickness of finish-cutting. Shapes of corner parts after finishing can be also estimated by using the equation of side-gap integration effect. Non-linear control at corner parts improves accuracy of coner parts, and it corresponds to the result of preestimation in its trend.
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  • Chracteristics of Thermal Fatigue of Quenched and Tempered SKD61 Die Surface after EDM and WEDM
    Masahiko HIHARA, Yoshitsugu MUKOYAMA
    1992 Volume 26 Issue 52 Pages 16-26
    Published: July 31, 1992
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    It has been found that the eroded layers of die steels which are formed after the electric discharge machining (EDM) and the wire electric discharge machining (WEDM) affect the quality or accuracy of dies. The effects of EDM and WEDM on the thermal fatigue of quenched and tempered SKD61 die surface have been studied by measuring residual stress and observing cracks. The residual stress in the surface of die was measured using the X-ray method. The main results obtained are as follows. (1) The tensile stress in the die surface, which was generated during EDM and WEDM decreased with increasing the heating and cooling cycles. (2) The residual stress change curve suggests that compression stress is generated in the deep region of the die surface after the thermal fatigue test. (3) The number of cracks generated during the thermal fatigue test decreased with increasing the energy supplying duration, τon.
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  • Kiyoto HASHIGUCHI, Hiroyuki SAWA, Syuji NITTA
    1992 Volume 26 Issue 52 Pages 27-35
    Published: July 31, 1992
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    This paper presents the development for the method of EDM by using flour composite resin electrode. Multi-arc spots phenomena which take place during the course of one short current pulse by use of the composite electrode at least as one side of electrode has been discussed in our previous study.
    Bulks of this composite resin are prepared by means of hot-press method at 190°C after mixing up copper or carbon flour with methacrylate resin.
    The former composite resin in particular causes a good result to keep the repeating pulse discharge in stable, and micro-craters formed by the pulse discharge are dispersed all over opposite metal face homogeneously. The result shows that this composite electrode might have a superior property for the industrial electrode material for EDM. When using the latter composite electrode, micro-craters are dispersed heterogeneously and sometimes concentrated in limited area. The result indicates that this electrode may be rather inferior for the electrode material.
    The discharge current which belongs to small energy level pulse ignition, less than one ampere and micro-second ordered pulse width, can carve some letters or curved line on the opposite steal surface without any heating effects. Higher level discharge current which has more than several amperes current and milli-second ordered pulse width can cause the steal surface to make obvious effects of heat hardening, although flour composite resin electrode has low temperature softening point at most below 200°C.
    But these resin electrodes have a big failure of wearing itself, because of the fact that the ratio of wearing amount is rather plenty as 4-10 times for the ratio of weight loss for FCR/steal. These experimental results show that the composite resin electrode makes a possibility of useful applications to some industrial fields because of the easy preparation of electrodes.
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  • Kiyonori MASUI, Yukihiro SATO, Takumi SOME, Kei DEMIZU
    1992 Volume 26 Issue 52 Pages 36-46
    Published: July 31, 1992
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    In the injection molding process of plastics, some out gas generated from their plastics may attack the structure of the molding dies and cause corrosion. Especially EDM'd dies could be damaged on the corrosion process.
    This paper deals with the corrosion resistance and its improvement on EDM'd surface in the molding process of plastics. An autoclave test method with plastics powder was used to evaluate the corrosion resistance.
    The results are summarized as follows; 1) In general, corrosion grows up as a pit from the micro-cracks generated on EDM'd surface. 2) However, a smooth and/or a crack-free surface EDM'd under the workpiece positive polarity with micro-power discharge give relatively high corrosion resistance. 3) Heat treatment conditions for the specimen before EDMing influence on the corrosion process. 4) Subsequently, a glass beads blasting method for EDM'd surface could be hopeful to improve the corrosion resistance.
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  • Macroscopic Observation of Removal Phenomena
    Masayuki SUZUKI, Naotake MOHRI, Nagao SAITO, Hideki TAKEZAWA
    1992 Volume 26 Issue 52 Pages 47-55
    Published: July 31, 1992
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    There have been many studies on the mechanism of electrical discharge machining. However, the general principle of the machining has not been found yet because of its complex machining phenomena. This study aims to find a simple but practical law of removal rate related with thermal properties of work piece. The removal rate is almost determined by the product of thermal conductivity and melting temperature. And the effect of carbon layer which covers copper electrode on the wear of the electrode is discussed through the experiments with several kinds of materials of work pieces. The materials of work pieces are classified into two groups according to the wear rate of copper electrode.
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