• 한국정밀공학회지
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• 제25권3호
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• pp.134-140
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• 2008

Micro electrochemical machining (ECM) is conducted on stainless steel 304 using non-toxic electrolyte of citric acid. Electrochemical dissolution region is minimized by applying a few hundred second duration pulses between the tungsten SPM tip and the work material. ECM characteristics according to citric acid concentration, feeding velocity and electric conditions such as pulse amplitude, pulse frequency, and offset voltage are investigated through a series of experiments. Micro holes of $60{\mu}m$ in diameter with the depth of $50{\mu}m$ and $90{\mu}m$ in diameter with the depth of $100{\mu}m$ are perforated. Square and circular micro cavities are also manufactured by electrochemical milling. This research can contribute to the development of safe and environmentally friendly micro ECM process.

• 한국정밀공학회지
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• 제28권2호
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• pp.251-256
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• 2011

The radial overcut in micro electrochemical machining was investigated. The prediction of overcut is important not only for the machining accuracy but also for the shape control of micro structures. In micro ECM, machining gap or overcut depends on electrolyte, pulse voltage, pulse duration and dissolution time etc. Understanding of electrochemical dissolution rate is necessary for the overcut prediction. In this paper, the radial overcut of micro electrochemical machining according to pulse duration and dissolution time was simulated using electrochemical principles and also experimentally estimated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.239-244
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• 2002

In this study, we developed the manufacturing technology of micro-hole and micro-shaft for micro punching system using micro electrical discharge machining and micro electro chemical machining. Micro punching dies of tungsten carbide with $55\;{\mu}m\;and\;110\;{\mu}m$ diameter and $250\;{\mu}m$ depth were made by micro electrical discharge machining. The form accuracy and surface roughness of die hole were pretty good and it was shown that the punched hole quality was fine. WC micro-shaft with $30\;{\mu}m$ diameter was made by the multistep micro electro chemical machining. The developed technologies can be effectively used in precision manufacturing of micro punching die and mass production of micro-shaft.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.1075-1079
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• 1995

It is difficult to machine microparts, such as microshaft and microholes, by conventional machining. Such micropart can be easily machined by EDM because it's machining force is very low. In micro-EDM, the precise electrode movement and discharge energy control are important. Therefore, high precision motion stage and EDM device with high performance is necessary. In this research, a new EDM machine was developed and microshaft and microhole, with various shape and size, was machined.

• 한국정밀공학회지
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• 제26권4호
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• pp.134-140
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• 2009

The feasibility of electrochemical drilling and milling on stainless steel are investigated using tungsten microelectrode with $10{\mu}m$ in diameter. For the development of environmentally friendly and safe electrochemical process, citric acid solution is used as electrolyte. A few hundred nanoseconds duration pulses are applied between the microelectrode and work material for dissolution localization. Tool fracture by Joule heating, micro welding, capillary phenomenon, tool wandering by the generated bubbles are observed and their effects on micro ECM are discussed. Occasionally, complex textures including micro pitting corrosion marks appeared on the hole inner surface. Metal growth is also observed under the weak electric conditions and it hinders further dissolutions for workpiece penetration. By adjusting appropriate pulse and chemical conditions, micro holes of $37{\mu}m$ in diameter with $100{\mu}m$ in depth and 26Jim in diameter with $50{\mu}m$ in depth are drilled on stainless steel 304. Also, micro grooves with $18{\mu}m$ width and complex micro hand pattern are machined by electrochemical milling.

• 한국정밀공학회지
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• 제22권4호
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• pp.52-59
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• 2005

When a micro hole is machined by EDM with a cylindrical electrode, the hole diameter is different at the inlet and the outlet of the micro hole. The taper shape of the micro hole is caused by not only wear of the electrode but the eroded particles. The eroded particles cause secondary discharge during machining the micro hole. As a result, the diameter of the inlet becomes larger than that of the outlet. In this paper, a new method is proposed to reduce the difference in diameter between the inlet and the outlet of the hole. Observed was that the feed depth and machining time affect the formation of taper shape On this experimental basis, ultrasonic vibration was applied to reduce machining time, and capacitance was changed during machining to use the difference in discharging energy of different capacitances. Using the proposed method, a straight micro-hole was fabricated.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.37-42
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• 1997

This paper describes result of experiment of parameters affecting the micro hole drilling time, kind of assisting gas and it's pressure. The result reveals that parameter value of 0.08J, 20Hz, dwell time of 300 microseconds can be a good machining condition to make micro hole diameter range of 50-70${\mu}{\textrm}{m}$, Assistant gas such air, O2, Ar, N2 was adapted. Assistant gas of air makes heat affected zone enlarge due to burning of material, also it makes hole irregular and damage because of refusion stick to caused by chemical reaction with Al2O3 ceramic material. O2(99.9%) has good characteristic to get good drilling and smooth surface on pressure of 0.2kgf/$\textrm{cm}^2$, but it is expensive. Ar, N2 makes material burn and crack severely and proved to be an appropriate but, Ar was better than N2.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1202-1205
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• 2005

Micro hole is one of basic elements for micro device or micro parts. By micro ECM, micro holes less than $50\mu{m}$ in diameter can be machined easily. Machining characteristics of micro ECM were investigated according to machining conditions such as electrolyte concentration and pulse conditions. From the investigation, optimal machining conditions were suggested for micro ECM of stainless steel. For the micro machining with high resolution, the change of machining gap should be predicted. By using electrochemical principle equations, the change of machining gap was simulated.

• 한국기계가공학회지
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• 제14권3호
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• pp.105-111
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• 2015

Ultrasonic machining (USM) does not involve heating or any electrochemical effects, and subsequently causes low surface damage, has small residual stress, and does not rely on the conductivity of the workpiece. These characteristics are suitable for the machining of brittle materials, such as glass or ceramics. However, USM for brittle materials generates cracks on the workpiece while machining, especially at the hole exit with a small diameter. In this study, wax coating was used to deposit wax on the back side of the workpiece to decrease the occurrence of cracks at the exit holes in USM, and it was finally removed with a cleaning process. The experimental results show that this technique is beneficial for restricting the occurrence of cracks in glass or ceramics.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.329-333
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• 2003

In micro hole punching process the burr occurs inevitably, but the burr must be minimized in order to improve the quality and accuracy of the product. In this study, magnetic field assisted polishing technique is applied to remove the burr which exists in nozzles for ink-jet printer head and proved to be a feasible for deburring by experiment. The deburring characteristics of sheet metals was investigated changing with polishing time. After the deburring, the burr size has remarkably reduced and roundness of the hole also has improved.