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Volume 30 (1996)
- Issue 65 Pages 1-
- Issue 64 Pages 2-
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Volume 30, Issue 65
Displaying 1-3 of 3 articles from this issue
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Yoshiyuki UNO, Akira OKADA, Hirohito NAKANISHI, Changning GUO, Yasuhir ...1996 Volume 30 Issue 65 Pages 1-8
Published: 1996
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSIn electrical discharge machining (EDM) process, the reduction of electrode wear is very important for high accuracy machining. It is reported that low electrode wear EDM can be achieved by the adhesions of workpiece material and heat resolved carbon from machining fluid to the electrode end surface, because of the protection effect of the latter which has large heat resistivity. Under a proper condition, even no electrode wear EDM is possible. Such adhesion phenomenon, however, is observed only on the condition that the pluse duration is relatively large. That is, it never occurs on the small pulse duration such as finishing condition. Therefore, no electrode wear EDM under finishing condition is impossible so far and the electrode wear in finishing EDM is practically allowed to be inevitable. It is reported that the heat resolved carbon from machining fluid adhering to the electrode end surface is turbostratic carbon. It has the chemical structure in which hexagonal lattice plane laminates irregularly, different from graphite structure. From these results, it is considered that no electrode wear EDM might be attained by using turbostratic carbon electrode under finishing condition.
In this study, EDM characteristics of a newly developed CVD-carbon electrode are experimentally investigated for higher performance EDM. Experimental analysis made it clear that low electrode wear EDM is possible by using CVD-carbon electrode even under finishing condition, since the heat resolved carbon from machining fluid has a stronger tendency to adhere to the end surface of CVD-carbon electrode than that of graphite one.View full abstractDownload PDF (10605K) -
Yoshiyuki UNO, Shin-ichiro KUBOTA, Seiichi YOKOMIZO, Akira OKADA, Hide ...1996 Volume 30 Issue 65 Pages 9-16
Published: 1996
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSMicro machining of brittle materials such as silicon or ceramics is difficult by traditional machining method, since stress generated at machining point causes cracks and fractures. EDM is performed by repetition of micro crater produced by a single discharge and machining force is very small. Therefore, EDM might be used for micro machining of single crystalline silicon. In this paper, EDM characteristics for fine boring of single crystalline silicon were experimentally investigated.
Main conclusions obtained in this study are as follows:
1) EDM can be carried out for single crystalline silicon whose specific resistance is less than about 10-2Ω·cm.
2) The removal rate for single crystalline silicon is 2-10 times as high as that of SUS304.
3) In deionized water, the removal rate with copper electrode is 5-10 times higher than that with tungsten electrode.
4) The adhesion of silicon to the electrode surface in the normal polarity EDM is remarkable as compared with that in the reversed one, which leads to lower removal rate under the same setting condition.
5) The shape of micro hole is better in kerosene type fluid, while the removal rate is 15 times lower than that in deionized water.View full abstractDownload PDF (8385K) -
Takayuki TANI, Yasushi FUKUZAWA, Naotake MOHRI, Nagao SAITO1996 Volume 30 Issue 65 Pages 17-23
Published: 1996
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSIn this paper, a new EDM of insulating ceramics with an assisting electrode and its machining characteristics are described. In this method, a metal plate or several metal mesh sheets is attached on the surface of sialon ceramics as an assisting electrode. The machining starts on the assisting electrode down to the insulating ceramics with kerosene as working fluid. The ceramics surf ace was covered with a black layer which consists of α-SiC and C, and this layer keeps electrical conductivity on the ceramics surface during the machining. When the tool electrode reaches at the boundary between the metal plate and the ceramics, the machining does not proceed for several minutes while the black layer forms on the ceramics surface. This period is named as transition time. The transition time and amount of adhesive black layer depend on the physical properties of assisting electrode such as melting point and thermal conductivity. Laminated several sheets of metal mesh as the assisting electrode improve machining rate and surface roughness much better than that with metal plate. The proposed method is available for machining a complex shape on sialon insulating ceramics.View full abstractDownload PDF (5848K)
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