1998 Fiscal Year Final Research Report Summary
Development of Ultra-high-precision Micromachining System using Dry EDM
| Project/Area Number |
09555038
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
機械工作・生産工学
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| Research Institution | Tokyo University of Agriculture & Technology |
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Principal Investigator |
KUNIEDA Masanori Tokyo University of Agriculture & Technology Department of Mechanical Systems Engineering Associate Professor, 工学部, 助教授 (90178012)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Yuhji Sodick Co., Ltd.Research and Devepolment Division Chief Director, 研究開発本部, 部長
YOSHIDA Masahiro Tokyo University of Agriculture & Technology Department of Mechanical Systems En, 工学部, 教務職員 (80220680)
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| Project Period (FY) |
1997 – 1998
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| Keywords | electrical discharge machining / micromachining / dry EDM / material removal rate / tool electrode wear / oxygen gas / piezoelectric actuator / residual stress |
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| Research Abstract |
This research aims to develop an ultra-high-precision micromachining system using dry electrical discharge machining (dry EDM). In dry EDM, with the help of a high-pressure gas flow supplied through a thin-walled pipe electrode, the molten workpiece material can be removed and flushed out of the working gap without being reattached to the electrode surfaces. One of the greatest advantages of this technique is that the tool electrode wear ratio is almost zero for any pulse duration. Furthermore, the process reaction force is negligibly small and the residual stress generated on the surface machined is quite low compared with the conventional EDM using oil as the dielectric liquid. As a result, the dry EDM is expected to be one of the most promising techniques for micromachining.
However, the material removal rate is considerably lower than that of the conventional EDM, because the probability of short circuiting during successive pulse discharge ranges up to ninety five percent due to th
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e extremely narrow working gap. Hence, to lower the probability of short circuiting, first a high frequency response piezoelectric actuator was installed on the working table and driven by a servo control which operates together with the original servo-feed mechanism of the Z-axis of the EDM machine. Secondly, the open voltage was raised to obtain a longer gap distance to prevent short circuiting. Experimental results show that both measures are effective to obtain a dramatic increase in the material removal rate.
To scale down the size which can be achieved using the dry EDM, usage of the pipe electrode should be eliminated, because there is a limitation in the minimum diameter of the pipe electrode. Hence, the dry EDM using solid electrode was tried by means of supplying oxygen gas jet to the discharge gap from a nozzle which is positioned outside the gap. The minimum diameter of rods machined by WEDG in oxygen gas was 5 mu m, and the distortion of the obtained rod 15 mu m in diameter and 200 mu m in length was much smaller than that obtained in a dielectric liquid. Furthermore, the ratio of tool electrode wear in the dry-micro-EDM was found to be significantly low compared with that obtained with the conventional micro-EDM in liquid. Less
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