Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 47, Issue 116
Displaying 1-3 of 3 articles from this issue
Paper
  • Tomohiko ICHIKAWA, Wataru NATSU
    Article type: Paper
    2013 Volume 47 Issue 116 Pages 155-162
    Published: 2013
    Released on J-STAGE: March 28, 2014
    JOURNAL FREE ACCESS
      Micro-EDM has its potential in the manufacture of micro tools and parts. However, the machining speed is low owing to short circuit and abnormal discharge, because of the difficulty in removing debris from the narrow gap-width. In particular, hole drilling becomes impossible under ultrasmall discharge energy conditions, such as the low open voltage and stray capacitance in the RC discharge circuit. In this study, the effect of applying ultrasonic vibration to the machining fluid in micro-EDM was experimentally investigated, in order to realize a higher machining speed in the deep hole drilling process. Furthermore, the effects of vibration on the machining characteristics of micro-hole drilling under the ultrasmall discharge energy condition were investigated. It was found that a significant increase in machining speed was realized by applying ultrasonic vibration to the machining fluid. Also, with the application of vibration to the machining fluid, micro-hole drilling with ultrasmall discharge energy became possible. Additionally, experimental results show that the lateral gap-width between the tool electrode and the workpiece, as well as and the tool wear ratio, became smaller.
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  • Atsutoshi HIRAO, Takayuki TANI, Ju-Kyoung Lee, Naotake MOHRI, Nagao SA ...
    Article type: Paper
    2013 Volume 47 Issue 116 Pages 163-168
    Published: 2013
    Released on J-STAGE: March 28, 2014
    JOURNAL FREE ACCESS
      In this study, we propose a new micropin forming method in which the forming plate can be stationary while the rotating electrode moves towards the forming plate. As the processing area in this method is large, a higher removal rate is possible compared with the WEDG micropin forming method. Forming by this method is easily accomplished for the micropins of less than 50 μm under a low electrical discharge conditions. In this study, we aimed to obtain the desired electrode diameter by means of scanning electric discharge machining. The electrode diameter decreased rapidly with increasing machining time, and it was difficult to control the micropin diameter by controlling only the machining time. Therefore, we conducted micropin forming by controlling the indicator scanning distance during machining. The results are strongly dependent on the ratio of consumption of the forming plate and the electrode. We investigated the relationship between the electrode diameter and the scanning distance referring to the experimental values and the theoretical ratio based on the consumption theory. Micropin diameters of up to 150 μm were obtained. The experimental values were found to be in good agreement with the theoretical values. Since the wear ratio was changed owing to the miniaturization of the electrode, there is a difference between the theoretical and experimental values.
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  • Katsushi FURUTANI, Hiroyuki SHINTANI, Yasuo MURASE, Shuichi ARAKAWA
    Article type: Paper
    2013 Volume 47 Issue 116 Pages 169-176
    Published: 2013
    Released on J-STAGE: March 28, 2014
    JOURNAL FREE ACCESS
      In this paper, we deal with the performance of electrochemical discharge machining (ECDM) with multiple electrodes. ECDM has been used to machine grooves and holes on insulated materials such as glass. However, many cracks are often observed around a machined hole because of the accumulation of discharge heat. While some holes were being 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 performance of ECDM was compared with those of multiple electrodes connected electrically in parallel (equi-potential power) and of a single electrode. Then hole shapes were observed. The hole entrance was round because of the divided power. In the cases of equi-potential power and a single electrode, cracks were frequently generated around the hole entrance by heat expansion. The cracks were the origins of protrusions by erosion. Eventually, long protrusions were formed. Because bubbles collapse during pulse intervals because of the divided power, the hole diameter was not enlarged.
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