Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 48, Issue 117
Displaying 1-3 of 3 articles from this issue
Paper
  • Katsushi FURUTANI, Hiroyuki SHINTANI, Yasuo MURASE, Shuichi ARAKAWA
    2014 Volume 48 Issue 117 Pages 6-14
    Published: 2014
    Released on J-STAGE: July 11, 2014
    JOURNAL FREE ACCESS
      This paper deals with the monitoring of the current during electrochemical discharge machining (ECDM) with multiple electrodes. A gravity-feed-type unit with six electrodes for ECDM was fabricated. The polarity of the electrodes was set to be negative. While some holes were machined by ECDM on glass, the discharge current was forced to disperse by switching the electrodes to decrease the number of cracks (divided power). The current in the divided power was observed during the machining process and compared with those in the cases of multiple electrodes connected electrically in parallel (equipotential) and of a single electrode. Bubbles were generated by current pulses with a duration of several milliseconds when the voltage was applied. However, they disappeared during pulse intervals. A current pulse with a duration of two to five milliseconds preceded a series of sharp pulses below 200 μs in the single-electrode and divided-power methods. Long and low-peak-current pulses frequently occurred, and the current pulses were concentrated at the electrodes at the two ends with equipotential power.
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  • Katsushi FURUTANI, Daisuke HIRAOKA
    2014 Volume 48 Issue 117 Pages 15-21
    Published: 2014
    Released on J-STAGE: July 11, 2014
    JOURNAL FREE ACCESS
      This paper deals with an electrode feeding device based on AZARASHI mechanism for microhole electrical discharge machining. This device has a controlled friction device, a friction device for applying a constant friction and an extension device for changing the distance between the friction devices. To adjust the friction easily, a stacked piezoelectric actuator was embedded in a displacement magnification system for the controlled friction device, and a constant friction was applied with a coil spring. The performance of the concurrent machining in the case of using two devices was compared with that in the case of using a single device. The two devices were concurrently controlled with a digital signal processor. The piercing of each tool electrode was detected by the electric contact between the tool electrode and a target plate in the concurrent machining. The machining time and accuracy were the same in the both cases.
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  • Shinya IMAI, Shinya HAYAKAWA, Fumihiro ITOIGAWA, Takashi NAKAMURA
    2014 Volume 48 Issue 117 Pages 22-27
    Published: 2014
    Released on J-STAGE: July 11, 2014
    JOURNAL FREE ACCESS
      In this study, we observed the bubble coalescence in the electrical discharge machining (EDM) process to investigate the effect of bubble behavior on machining phenomena such as machining stability. A parallel flat gap space composed of a copper rod electrode of 20mm diameter and a transparent plastic plate in which three iron wires of 1mm diameter were inserted was used for the experiment. A series of pulse discharges was ignited in EDM oil and the behavior of bubbles generated in the parallel flat gap space was observed using a high-speed video camera through the transparent plastic plate. It was found that the generated bubbles coalesce with each other during the machining process, and the coalesced large bubble is easily ejected from the edge of the machining surface. It was also found that the jumping motion of the tool electrode promotes the coalescence of the bubbles and the ejection of the coalesced large bubble, which increase the machining stability of the EDM process.
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