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Volume 43 (2009)
- Issue 104 Pages 163-
- Issue 103 Pages 74-
- Issue 102 Pages 1-
Volume 43, Issue 104
Displaying 1-4 of 4 articles from this issue
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- Analysis of micro-EDM process with deionized water -Takeshi MASAKI, Tsunemoto KURIYAGAWA2009 Volume 43 Issue 104 Pages 163-171
Published: November 30, 2009
Released on J-STAGE: January 27, 2010
JOURNAL FREE ACCESSThe micro-EDM process with deionized water as a dielectric fluid is used for nozzle production because of its high speed and low tool wear benefits. However, this process causes the formation of defects due to the electrolysis corrosion and processing limitation of applicable materials. It was considered that the electrolysis corrosion is induced by the ion produced as a result of the electro-discharge process. The process mechanism is considered in line with the theory indicating that electrolysis occurs in the deionized water when a high voltage is applied. Oxygen and H+ are formed at the anode surface during electrolysis, the carbon in the anode is oxidized, and part of the metal is corroded. For tungsten carbide, the corrosion is severe. A pulse shorter than 40ns can inhibit electrolysis and allow a highly precise micro-EDM to use deionized water with tungsten carbide. The tool wear ratio is 0.025% by volume and the processing speeds that are 150 times higher than those under the same conditions using oil as a dielectric fluid are verified. In addition, the mechanism of the electrolysis corrosion in stainless steel and the capability of the improved surface quality to control the generated electrolysis are explained.View full abstractDownload PDF (1830K) -
Kai EGASHIRA, Yo OTAKE, Maki SHIOTA, Hiromitsu UENO2009 Volume 43 Issue 104 Pages 172-178
Published: November 30, 2009
Released on J-STAGE: January 27, 2010
JOURNAL FREE ACCESSIt is difficult to miniaturize tools for chamfering and deburring the back sides of micro-through holes.Therefore, chamfering and deburring by EDM were attempted using tool electrodes with the middle part thinner than the other parts. The tungsten tool electrodes were fabricated by wire electrodischarge grinding, and the back sides of micro-through holes drilled in copper and brass sheets were processed. As a result, chamfering was successfully carried out on the back sides of a microhole with a diameter of 60 μm, a deep hole with an aspect ratio of 5 and a noncircular hole. Furthermore, the chamfering of the front and back sides of a hole using a single tool electrode, round chamfering, deburring and counterboring were possible by adjusting the tool electrode shape. In deburring, the burr was removed with hardly any removal of the edge of the hole.View full abstractDownload PDF (3488K) -
- Effects of wire surface unevenness on wire EDM characteristics -Akira OKADA, Toshiyuki YAMAUCHI, Masayuki HIGASHI, Toshiaki SHIMIZU, Y ...2009 Volume 43 Issue 104 Pages 179-186
Published: November 30, 2009
Released on J-STAGE: January 27, 2010
JOURNAL FREE ACCESSThe purpose of this study is to develop a new type of coated wire electrode for fine wire EDM. Piano wire with a very high tensile strength is coated with an electrically conductive brass layer to achieve high-speed and high-precision wire EDM. In our previous papers, using a thin wire of 50μm diameter, the thickness and quality of the brass coating layer were optimized and the effect of the tensile strength of the piano wire used as the core wire was discussed. In this report, the effect of unevenness of the brass wire electrode surface was experimentally investigated. As a result, it was found that by using wire with relatively large surface unevenness, the machining rate increased because of the high discharge frequency. Also, a more uniform distribution of the discharge location was confirmed by high-speed observation of the working gap during the process. In addition, the electrostatic field in the gap between the wire electrode and workpiece surface was analyzed and the reason for the high machining rate for the wire with relatively large surface unevenness was discussed from the viewpoint of the distribution of electric intensity distribution on the wire surface.View full abstractDownload PDF (3714K) -
Takayuki TANI, Hiromitsu GOTOH, Ju-Kyoung LEE, Naotake MOHRI2009 Volume 43 Issue 104 Pages 187-193
Published: November 30, 2009
Released on J-STAGE: January 27, 2010
JOURNAL FREE ACCESSIn this study, we demonstrate a new method of micro-pin electrode formation by scanning EDM. A micro-pin electrode is fabricated by scanning EDM, in which the tool electrode approaches the side of the working plate in the horizontal plane. The rotating electrode is moved through the inside of the working plate, and then, a micro-pin WC-Co electrode is formed with a diameter of about 40μm. However, with this method, it is difficult to control the electrode diameter owing to occasional wear. To control the electrode diameter, we set two electrically isolated plates in position, and the movement of the electrode is controlled to keep the electrode in the center of the clearance by measuring currents in the isolated plates. As the results, the machined diameter closely corresponds to the desired diameter, and then, the 300μm diameter of the WC-Co tool electrode of 1.5mm length was changed to a 50μm diameter in 3 min of machining under twin power supply conditions.View full abstractDownload PDF (1056K)
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