Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 25, Issue 50
Displaying 1-5 of 5 articles from this issue
  • Change in Curvature of a Machined Thin Plate and Surface Structure by Tempering
    Isao OGATA, Yoshitsugu MUKOYAMA, Masahiko HIHARA
    1991 Volume 25 Issue 50 Pages 1-12
    Published: November 30, 1991
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    When a thin plate is machined by EDM on one side, a certain curvature results owing to tensile residual stress generated on the surface of the workpiece. If the machined plate is tempered, some change in curvature of the thin plate appears to occur due to reduction in residual stress and changes in the degenerated layers.
    This study was conducted to examine changes in curvature of a machined thin plate under various tempering conditions, in relation to those in the properties (phase changes) of the machined surface, using an X-ray diffractometer
    Reduction in residual stress was concluded to occur due to stress relaxation, phase changes (transformation of γ Fe to α Fe) and the precipitation of carbides (Fe3C, M7C3). Change in curvature of thin plate was essentially the same as that noted by the X-ray stress measuring method. As a result, there occurs considerable plastic deformations (slip, twinning and lattice defects) of the EDM surface, owing to thermal effects.
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  • Hidekazu GOTO, Hachiro TSUCHIYA, Hidenao KATAOKA
    1991 Volume 25 Issue 50 Pages 13-22
    Published: November 30, 1991
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Cutting characteristics of ceramics (Al2O3, ZrO2 and Si3N4) by using localized reactive gas plasma were investigated theoretically and experimentally. Applying a breakdown voltage between two needle shaped Pt electrodes which are facing each other and holding a ceramic material (t0.6-2mm) between them in etching gas (1-2atm), repetitive discharge (1-15kHz) can be induced between the two electrodes along the material surface. Then a linearly localized reactive gas plasma whose diameter is about 40-60μm can be generated along the material surface and cutting process proceeds with the chemical reaction between the material surface and the reactive gas molecules generated in the plasma. Experimental results are as follows. Etching gas, gas pressure, gas flow rate, electrode gap length and resistance of discharge circuit were the parameters changed. Gas pressure was the most effective parameter to increase cutting rate. In the case of Al2O3 (t600μm), the cutting rate obtained in 2atm SF6 gas was 600μm/min. The cutting rate of Si3N4 was 2-3 times greater than that of Al2O3. ZrO2 was unable to be cut because a thermally affected layer was generated on the surface along the gas plasma.
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  • Akihiro GOTO, Masahiko FUKUI, Natsuo KINOSHITA
    1991 Volume 25 Issue 50 Pages 23-31
    Published: November 30, 1991
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Need for technique to dig curved tunnnel into metal is becoming increase. For example, in a field of the mould injection, they expect such a technique to appear, because it will improve the precision of injection. However, no study has been done to realize it for now.
    This paper deals with this new technique making use of EDM. we name it “Mole-EDM” for it is like a mole digging a tunnel into the ground.
    In this paper, the mechanism and the way of control are explained. The Mole-EDM machime's shape is like a bar which can be bent, and the SMA (shape memory alloy) is used as an actuater. This time the ultrasonic wave is used to detect the form of tunnels digged by the Mole-EDM.
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  • Estimation of Melting Remnant and Thermal Affected Layer Formed by an Impulsed Discharge
    Makoto MIYAZAKI, Hachiro TSUCHIYA, Michio INUI
    1991 Volume 25 Issue 50 Pages 32-38
    Published: November 30, 1991
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    In electric discharge machining, it is wellknown that any molten part remains as a melting remnant layer and under it a thermal affected layer is formed. This paper deals with an estimation of those layers based on the microstructure surrounding the impulsed discharge crater. The boundary between the melting remnant and the thermal affected layer can be clear. Furthermore, Ac1 and Ac3 transformation due to the higher heating and cooling action in an extremely short time are observed on the thermal affected layer. The Ac1 and Ac3 transformation temperatures are about 800°C and 900°C, respectively. The results present several thermal data for confirming the validity of a thermal conductive model for theoretical analysis of the size and form of the crater.
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  • Relationship between Two Dimensions Evalution of EDM Surface Roughness
    Yoshitsugu MUKOYAMA, Akiyoshi KAWATA
    1991 Volume 25 Issue 50 Pages 39-52
    Published: November 30, 1991
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Usually, the most of evalution about surface roughness are carried out in form of two dimensions. But in the case of removal machining based on discharging in liquid, the process of machining is effected considerably by uncertain factors between two electrodes, it is difficult that surface roughness is exactly measured by the statistical method because the shapes of surface are complicated and various.
    In this report, tracer method based on two dimensions is improved and software is supplemented, the removal crater by single discharging and surface roughness by repeated discharging are measured and evaluated in the form of three dimensions. As the result, the greatest real values of removed part and rised part of removal crator and surface roughness are measured. Moreover, the volume, the holding area of the volume and the weight of removed part and rised part of crator are evaluated and measured with that relation of numerical value between two dimensions and three dimensions are made clear.
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