Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 32, Issue 70
Displaying 1-10 of 10 articles from this issue
  • Effect of Condenser Electrical Discharge
    Taemin SHIN, Hisashi YAMADA, Naotake MOHRI, Katsushi FURUTANI, Yasushi ...
    1998 Volume 32 Issue 70 Pages 1-7
    Published: July 31, 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Because of the high resistivity of insulating ceramics, there are some differences compared with the EDM of metallic materials. The secondary metal as an assisting electrode and a minus polarity of the electrode overcame the difficulties of machining for insulating ceramics. And the insertion of a condenser between the electrode and the workpiece improves the removal rate and the stability in electrical discharge machining for insulating ceramics. But there is no distinct explanation of the mechanisms. In this paper, we certified the mechanism and the effects of the condenser EDM for insulating ceramics as Si3N4, Sialon and SiC.
    There are two types of the electrical discharge waveforms in the condenser EDM of insulating ceramics. A high electrical resistance of the surface causes a discharge with longer pulse duration than the settled value of discharge duration, which produces a lot of carbon from the working oil by heating. The low electrical resistance generates short discharge pulses which waste the carbon gradually. These waveforms are affected by a discharge-detection voltage, an equivalent resistance of ceramics' surface, and electrical parameters of discharge circuits. An adequate balance of a long pulse and short pulses makes it possible to machine insulating ceramics with high removal rate and high stability.
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  • 2nd Report: Grouping Method of Gap Signals according to Discharged Location
    Haruki OBARA, Mitsuru ABE, Tsuyoshi OHSUMI
    1998 Volume 32 Issue 70 Pages 8-15
    Published: July 31, 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    In the 1st report we investigated about 3 gap monitoring signals: discharge voltage, ignition delay time and a radio signal just before wire breakage, in order to know which of them is the best signal to pre-monitor the wire breakage during wire EDM. Results showed that the discharge voltage is the best signal by which to pre-monitor the wire breakage. But other signals were not so clear.
    In the present report, we propose a new detecting method dividing these signals into groups according to discharged locations. This method clarify an abnormal gap state just before the wire breakage. Finally, we discuss a model of wire breakage that is able to explain obtained experimental results.
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  • 1st Report: Relation between Cut Groove Width, Wire Vibration Amplitude and Gap length on Rough Wire EDM
    Haruki OBARA, Toshihito KAMIWAKI, Tsuyoshi OHSUMI
    1998 Volume 32 Issue 70 Pages 16-23
    Published: July 31, 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    In this series reports, we deal with accuracy of Wire EDM from rough cutting to finish cutting discussing about reasons of spoiled precisions.
    In this first report, we investigate about the relation between cut groove width, wire vibration amplitude and gap length of the rough machining, and also about the relation between them and some EDM conditions.
    The wire vibration amplitude is measured with a optical fiber-slit detecting system. The gap length is calculated from ignition delay time using an experimentally obtained relationship between the ignition delay time and the gap length for a single discharge. The ignition delay time is calculated from mean working voltage and other EDM conditions.
    Results shows that the cut groove width is the sum of the wire diameter, the wire vibration amplitude and the double of gap length. The wire vibration amplitude is proportionally increasing with discharge frequency from the value of wire vibration amplitude caused by a single discharge, and also increasing with the gap length.
    It is clarified that the cut groove width is less sensitive to OFF duration of discharging pulse if the mean working voltage was used for a servo feed back system or if the mean working voltage was constant, because the increasing of gap length cancels the decreasing of wire vibration amplitude when the OFF duration was increased.
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  • Yoshiyuki UNO, Akira OKADA, Tomohiko YAMADA, Yasuhiro HAYASHI, Yoshiak ...
    1998 Volume 32 Issue 70 Pages 24-31
    Published: July 31, 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Aluminum bronze which has high corrosion resistance, high strength and easy castability is recently expected as a new plastic mold or a shell mold core material in place of steel conventionally used. On the other hand, it is reported that the EDMed surface with metal powder mixed fluid has smaller surface roughness and higher resistance to corrosion. From these points of view, EDM characteristics of aluminum bronze were experimentally investigated in the first place. Then, EDM with nickel powder mixed fluid for smoother surface roughness and higher surface integrity was proposed and evaluated. Main conclusions obtained in this study are as follows:
    (1) The metal removal rate in EDM of aluminum bronze is approximately the same as that of steel, and no electrode wear EDM is possible.
    (2) The EDMed surface with nickel powder mixed fluid has a smaller surface roughness than that in conventionl EDM with kerosene type fluid.
    (3) Resolidified layer containing nickel can be generated and the thickness of the layer becomes larger and uniform with an increase of nickel powder concentration in machining fluid.
    (4) The EDMed surface with nickel powder mixed fluid becomes harder than that with kerosene type fluid and it has high resistance to sand abrasion.
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  • Hisashi MINAMI, Kiyonori MASUI, Hidekazu TUKAHARA, Hideki HAGINO
    1998 Volume 32 Issue 70 Pages 32-39
    Published: July 31, 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    A new coloring method for titanium alloy by using EDM process is proposed. With this method, the requested colored surface is obtained during the finishing Wire-EDM process in a dielectric water without any other post treatment. In this paper, the coloring mechanism for titanium alloy and the influence of the processing condition to the color tone are discussed.
    The results obtained are as follows:
    (1) A molten and resolidified surface created by electrical discharge process is colored directly by the interference phenomena in the anodic oxide film formed with electrolytic affection.
    (2) The thickness of the oxide film determines the color tone, so it can be possible to give various kind of colors by controlling the average working voltage.
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  • Shin'ichiro KUBOTA, Yoshiyuki UNO, Nobuyuki NISHIHARA, Takashi TAKAGI
    1998 Volume 32 Issue 70 Pages 40-48
    Published: July 31, 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    This paper deals with machining methods of fine graphite electrode for EDM by Q-switched Nd: YAG laser. Graphite is a superior material as an electrode for EDM and has widely been used. However, it is difficult to make a complicated shape of thin graphite plate less than 1mm by the conventional machining methods because of its brittleness. In this paper, Q-switched Nd: YAG laser is used for machining the micro rectangular parallelepiped graphite electrode whose thickness is 0.35mm.
    Main conclusions obtain are as follows:
    1. The rectangular parallelepiped whose sections is about 0.35mm square can be machined precisely by Q-switched YAG laser.
    2. Cutting off method of 2 plates of workpieces together leads to a better rectangular parallelepiped shape of the lower plate.
    3. The roughness of machined surface is improved by another scanning with lower power laser.
    4. In normal polarity EDM with RC circuit in deionized water, a better rectangular hole can be generated with copper impregnated graphite electrode.
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  • 1998 Volume 32 Issue 70 Pages 77a
    Published: 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Download PDF (677K)
  • 1998 Volume 32 Issue 70 Pages 77b
    Published: 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Download PDF (677K)
  • 1998 Volume 32 Issue 70 Pages 77c
    Published: 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
    Download PDF (677K)
  • 1998 Volume 32 Issue 70 Pages 77d
    Published: 1998
    Released on J-STAGE: March 12, 2010
    JOURNAL FREE ACCESS
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