Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 31, Issue 68
Displaying 1-5 of 5 articles from this issue
  • Masaaki SANO, Masahiko HIHARA, Koji YATSUSHIRO, Yoshitsugu MUKOYAMA
    1997 Volume 31 Issue 68 Pages 1-10
    Published: November 29, 1997
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    The purpose of this report is to evaluate thermal fatigue characteristics of EDMed surface, which attribute to prolonging the life of die steels and stability of the quality of the product.
    EDMed surface treated with shot-peening, gas-nitriding and laser irradiation were evaluated for thermal fatigue by use of microphotographic observation and a X-ray residual stress measurement.
    As a result of these tests, it was found that tensile stress on the EDMed surface can be changed to compression stress by applying the various surface treatments, thus improving the thermal fatigue characteristics. Furthermore, the maximum crack length in the cross sectional area after the fatigue test was remarkably shorter, increasing the ability to withstand heat checking and thus proved to be an effective method for improving the EDMed surface.
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  • 1st report: Comparison of Spark Gap Detecting Signals on Wire EDM
    Haruki OBARA, Mitsuru ABE, Tsuyoshi OHSUMI
    1997 Volume 31 Issue 68 Pages 11-17
    Published: November 29, 1997
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    To prevent the wire breakage during wire EDM, there must be a reliable spark gap detecting signal which indicate the abnormal wire gap state just before the wire breakage. In this report we compare 3 gap detecting signals, namely the discharging voltage, the ignition delay time and the radio signal during wire EDM. To avoid the influence of wire impedance on the discharging voltage, a method which correct the discharging voltage depending on the discharged location is proposed.
    Results show that short circuits pulses, pulses of short ignition delay times and low level radio signal pulses are increasing just before the wire breakage. The detection of discharging voltage is the best method to premonitor the abnormal state of the wire or the gap state to prevent the wire breakage.
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  • 2nd Report: Averaged Wire Temperature during EDM
    Haruki OBARA, Seiji ADACHI, Tsuyoshi OHSUMI
    1997 Volume 31 Issue 68 Pages 18-25
    Published: November 29, 1997
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    To prevent the wire breakage during Wire EDM there should be information of the wire temperature because it is said that the wire may be broken by increasing of wire temperature. In our previous report we tried to measure the wire temperature distribution from discharging currents and voltage between the upper and the lower contactors contacting to the wire and averaged wire temperatures of 100°C or less were obtained. But these data were not calibrated and were not precise enough.
    In this report we retry to obtain precise averaged wire temperatures for two types of power supplying methods. In the first method the power is supplied from the lower contactor and in the 2nd the power is supplied simultaneously from the upper and the lower contactors. Also two types of workpiece materials, SUS304 and SKD11 are machined and results are compared. Wire temperatures are calibrated. It was found that during Wire EDM the wire resistance facing to the workpiece is greater than the static value and especially great in the case of ferromagnetic workpiece. Obtained averaged wire temperatures were almost 100°C at the maximum cutting speed for any cases.
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  • Akihiro GOTO, Takuji MAGARA, Yoshihito IMAI, Hidetaka MIYAKE, Nagao SA ...
    1997 Volume 31 Issue 68 Pages 26-31
    Published: November 29, 1997
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    This paper describes a new method of surface modification by EDM to create a hard surface on the workpiece. When a metallic material that can make a hard carbide is used an electrode of EDM, hard layer can be made in a certain condition. The process begins with electrode wear by heat of EDM. Then worn electrode material is combineds with carbon which is a constituent of dielectric fluid and becomes hard carbide. The carbide is piled up on a workpiece and becomes a layer.
    In this paper, the relation between electrical conditions to form the layer and thickness of the layer is examined. When pulse duration is short, the workpiece tends to be machined and the layer is thin. While pulse furation is long, the workpiece does not tend to be machined and the layer becomes thick.
    It is found that this hard layer has high wear resistance. In a experiment to check wear resistance, the surface which is given a hard layer by EDM is found to be three times as resistant as the one without the layer, and it is more resistant than a surface with TiN layer with PVD.
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  • Hiroaki HASHIMOTO, Masanori KUNIEDA
    1997 Volume 31 Issue 68 Pages 32-40
    Published: November 29, 1997
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    This paper describes the measurement of temperature variation of the arc plasma generated by the EDM pulse discharges in air using the spectroscopic analysis. Intensities of two radiation lines from copper atoms in the arc plasma are measured simultaneously using two monochrometers, and the temperature is obtained based on the line pair method. Although the measured radiant flux is significantly affected by the configurations of the electrodes, the obtained apparent temperatures during the discharge duration is between 6, 000 to 7, 000K regardless of the electrode configurations, discharge current or discharge duration. In the discharge interval, however, it takes longer time to decrease the plasma temperature and deionize the plasma, when the discharge current is higher, the discharge duration is longer or the rate of heat transfer from the plasma to the electrodes is lower. In a series of pulse discharges, the plasma temperature increases with the lapse of time as the surface temperatures of the electrodes are elevated.
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