Journal of The Japan Society of Electrical Machining Engineers
Online ISSN : 1881-0888
Print ISSN : 0387-754X
ISSN-L : 0387-754X
Volume 42, Issue 101
Displaying 1-3 of 3 articles from this issue
  • Akira OKADA, Ryuichi YASUDA, Yoshiyuki UNO
    2008 Volume 42 Issue 101 Pages 122-129
    Published: November 28, 2008
    Released on J-STAGE: February 27, 2009
    JOURNAL FREE ACCESS
    In deep-hole electrical discharge machining, the exclusion of debris is difficult, which leads to debris stagnation in the side gap. Thus, the wall of the machined hole becomes concave owing to secondary discharges in the side gap, even with the use of a linear-motor-driven EDM system with high-speed electrode jump. In this paper, the EDM of a deep hole using a flange-type electrode is proposed in order to prevent secondary discharges in the side gap and to improve shape accuracy. The EDM characteristics such as shape accuracy, removal rate and surface roughness are compared between the use of a flange-type electrode and that of a conventional straight electrode. The fluid flow and debris movement around the flange part of the electrode during the electrode jump are also discussed in view of the results of high-speed camera observation and CFD analysis. In addition, the effects of electrode shape on hole shape are investigated. Experimental results show that the concavity of machined holes can be easily improved using a flange-type electrode, even when using a conventional EDM with a ball screw drive. EDM performance becomes stable with the use of a flange-type electrode, and consequently removal rate improves.
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  • Atsutoshi HIRAO, Takayuki TANI, Hiromitsu GOTOH, Naotake MOHRI
    2008 Volume 42 Issue 101 Pages 130-136
    Published: November 28, 2008
    Released on J-STAGE: February 27, 2009
    JOURNAL FREE ACCESS
    In recent years, advances in technology have enabled the machining of nonconductive materials by electrical discharge machining (EDM). However, some machining characteristics still need to be improved for the wide industrial application of EDM. Among them are (i) surface roughness that is not good enough for finish machining, and (ii) the existence of a residual conductive layer on a material' s surface after machining that often requires a secondary process, that is, either shot peening or heat disposal process, for removal. In this research, in order to simplify the process for rough machining and finish machining, we designed a multifunctional machine that uses a feed wire as a tool for the forming process by wire EDM on the same machine, to ensure machining accuracy since the workpiece is not removed from the initial setup. The experimental setup includes a movable pulley with two wire guides at the center (WEDG), which is useful for the final finish processing without wire vibration. The Si3N4 material used as a workpiece was subjected to form machining, surface layer machining and abrasive machining before finish machining. We obtained a mirror surface using a wire with diamond particles as a tool.
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  • - Relationship between electrical conductive layer and machining characteristics -
    Hiromitsu GOTOH, Takayuki TANI, Naotake MOHRI
    2008 Volume 42 Issue 101 Pages 137-144
    Published: November 28, 2008
    Released on J-STAGE: February 27, 2009
    JOURNAL FREE ACCESS
    In recent years, ceramics materials have found increased use in industry. However, some of them are insulating ceramics that cannot be machined by conventional electrical discharge machining. In this study, we developed a special wire EDM machine for investigating the machining characteristics of insulating ceramics. The machining characteristics of Si3N4 insulating ceramics, especially surface roughness, are described. It was confirmed that long-pulse discharges are minimally generated under the second cutting conditions where small discharge craters are uniformly formed on the machined surface. The resulting surface roughness was improved down to 4μmRz. In addition, a unique process of machining with insulating ceramics, in which the threshold level becomes almost of the same as the voltage between the discharge and power supply positions, was observed.
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