Study of electrochemical discharge phenomena and its applications
Date Issued
2005
Date
2005
Author(s)
Peng, Wen-Yang
DOI
zh-TW
Abstract
The optical materials like Pyrex or quartz are more widely used due to the development of MEMS or bio-technology. The newly developed technology, electrochemical discharge machining(ECDM), may be a new procedure for machining these non-conductive brittle materials. But only if the spark mechanism or energy intensity problem is well-solved, will the new method be highly evaluated. This article aims at the erosion energy intensity and the derived material removal rate. The average current density is chosen as the spark density evaluation index. The power source parameters , the electrolyte supply arrangements and so on are investigated to derive the better spark release. For the horizontally-stretched wire electrode, the up-spray electrolyte supply could stabilize the gas film which enhanced the spark release. However the workpiece thickness is quite limited due to the drastic descending of the current density when the wire length is increased. The most inspiring observation of the current release is that the pulse current could be regulated by the power source parameters which means only the proper voltage-on time together with a good voltage-off time can realize tense spark release for a given wire length. For the cylindrical electrode tool with no larger than 2mm diameter, the electrode end area could attain the average current density above 0.11A/mm2. This implies that the electrode end area has more potential for machining application. More detail observations of the bubbles-to-film transformation process is implemented by the high speed photograph system. The gas film is formed at a sudden and the spark spot area is smaller and more evenly distributed when the voltage just reaches the “transition voltage” which symbolizes the stable spark phenomena is obtained. At higher voltage, the spark spot area is larger and more randomly occurred. With respect to the current pulse morphology, the current pulse is narrower and the peak value is smaller at lower voltage or smaller immersed area. The current pulse duration becomes longer and the peak is higher but there is less pulse occurrence within single voltage-on cycle time. This gives a new description of the continuous process concerning the gas film, the spark intensity and the current morphology at different voltage level.
These results tell how to decide the parameters in real hole machining process. To conquer the problem of gap maintenance at real machining, a slip-coupling is used to measure the utmost feed rate at certain eroded depth. A 1.9mm diameter hollow copper pipe is verified for stable machining ability to produce 36 holes on the 0.6mm thickness Pyrex wafer without electrode dressing and the hole diameter is satisfied. The cylindrical electrode is then used to thin the quartz wafer by the milling-like process. A locally-thinned wafer structure with minimum thickness of 50μm is successfully produced. This reveals another brand new application of the ECDM process.
Subjects
電化學放電加工
玻璃孔加工
石英加工
非導電硬脆材料加工
火花
氣泡
氣膜
臨界電壓
electrochemical dischage machining
optical wafer
quartz
spark
bubbles
gas film
current density
Type
thesis