• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1281-1284
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• 2005

In the micro electrochemical machining (ECM), unfavorable oxide/passive layer formation and overall corrosion of electrodes must be prevented. Generally, the stainless steel electrode corrodes, passivates or dissolves in the electrochemical cell according to the electrode potential. Therefore, the electrode must maintain stable potential. The stable electrode potentials of tool and workpiece were determined with the potentiodynamic polarization test and verified experimentally from the point of machining stability and machined surface quality.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.585-588
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• 2005

The dissolution characteristic of metal shows the different tendency according to the applied electrical potential, the kind of electrolyte and pH value, etc. In the micro electrochemical machining (ECM), unfavorable oxide/passive layer formation and overall corrosion of electrodes must be prevented. The anodic polarization curve of nickel has distinct three dissolution regions, i.e. two active regions and the transpassive dissolution region. In this paper, the stable electrode potentials of workpiece and tool were determined in sulfuric acid and hydrochloric acid solution, respectively. In each solution, different machining property was shown and possible electrochemical reactions were discussed. On the basis of this experiment, the methodology to obtain the proper electrode potential was suggested.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.918-921
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• 2002

Some investigators who have tried to achieve the highly smooth surface finish using electrochemical processes have reported that high current density produced lustrous surfaces while the opposite conditions produced a passive layer and had a tendency to produce a black surface. However, processing at a low current density may produce a non-lustrous surface but the improvement of dimensional accuracy of the surface is significant. The surface with pulse process was a bit more lustrous than with continuous current but the black passive layer still could be found at grooved surface. There are two ways to achieve highly smooth surface finish. One is brushing it with a brush the other is electrochemical machining (ECM) with high current. The former method is the most common polishing practice, but not only may the surface obtained differ from operator to operator, but precision smooth surface on micro grooves are difficult to obtain. The latter one recently has been used to produce a highly smooth surface after EDM process. However, the material removal rate in ECM with high current is relatively high. Hence the original shape of the micro grooves, which was formed by electrochemical micro-machining (EMM) process, may be destroyed. In this study, an electrochemical polishing process using pulse current is adopted as a possible alternative process when micro grooves formed by EMM process should be polished. Mirror-like micro grooves with lustrous and smooth surface can be produced electrochemically with pulse current because the voltage and current used can be lower than the case of continuous current. This study will discuss the accurate control of physical and electrical conditions so as to achieve mirror-like micro grooves with lustrous and smooth surface without destroying the original shape of micro grooves.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.159-164
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• 2005

For increasing productivity of micro electrochemical machining (MECM), the application of multiple electrodes was introduced. The electrodes were fabricated by reverse electrical discharge machining (REDM). By REDM micro electrodes with various shapes can be machined easily. According to capacitance and applied voltage, machining characteristics of reverse EDM were investigated and the optimal conditions for stable machining were suggested. By using multiple electrodes and a channel-shape electrode, holes and channels were machined on stainless steel by ECM.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.551-557
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• 2009

A development of smart materials is becoming a prominent issue on present industries. A smart material, included in functions, is needed for micro fabrication. A shape memory alloy(SMA) in a smart material is best known material. Ni-Ti alloy, composed of nikel and titanium is one of the best shape memory alloy(SMA). Nitinol SMA is used for a lot of high tech industry such as aero space, medical device, micro actuator, sensor system. However, Ni-Ti SMA is difficult to process to make a shape and fabrications as traditional machining process. Because nitinol SMA, that is contained nikel content more than titanium content, has similar physical characteristics of titanium. In this paper, the characteristics of ECM grooving process for nitinol SMA are investigated by experiments. The experiments in this study are progressed for power, gap distance and machining time. The characteristics are found each part. Fine shape in work piece can be found on conditions; current 6A, duty factor 50%, gap distance 15%, gap distance $15{\mu}m$, machining time 10min.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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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.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.142-144
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• 2014

전해가공(ECM)과 방전가공(EDM) 공정은 독특한 출력이 가능한 두 가지 이점이 있다. 방전가공과 전해가공은 보다 효과적이면서 거대하고, 미세한 나노 특성과 재료 가공의 정확한 3차원 복잡 형상 가공의 대안을 제공해준다. 본고에서는 학술적이고 산업적인 연구와 응용에 있어서 기예를 반영한 전해가공과 방전가공 공정의 기술적인 진전을 간략히 기술하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.81.2-81.2
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• 2012

To fabricate a metal mold for injection molding, hot-embossing and imprinting process, mechanical machining, electro discharge machining (EDM), electrochemical machining (ECM), laser process and wet etching ($FeCl_3$ process) have been widely used. However it is hard to get precise structure with these processes. Electrochemical etching has been also employed to fabricate a micro structure in metal mold. A through mask electrochemical micro machining (TMEMM) is one of the electrochemical etching processes which can obtain finely precise structure. In this process, many parameters such as current density, process time, temperature of electrolyte and distance between electrodes should be controlled. Therefore, it is difficult to predict the result because it has low reliability and reproducibility. To improve it, we investigated this process numerically and experimentally. To search the relation between processing parameters and the results, we used finite element simulation and the commercial finite element method (FEM) software ANSYS was used to analyze the electric field. In this study, it was supposed that the anodic dissolution process is predicted depending on the current density which is one of major parameters with finite element method. In experiment, we used stainless steel (SS304) substrate with various sized square and circular array patterns as an anode and copper (Cu) plate as a cathode. A mixture of $H_2SO_4$, $H_3PO_4$ and DIW was used as an electrolyte. After electrochemical etching process, we compared the results of experiment and simulation. As a result, we got the current distribution in the electrolyte and line profile of current density of the patterns from simulation. And etching profile and surface morphologies were characterized by 3D-profiler(${\mu}$-surf, Nanofocus, Germany) and FE-SEM(S-4800, Hitachi, Japan) measurement. From comparison of these data, it was confirmed that current distribution and line profile of the patterns from simulation are similar to surface morphology and etching profile of the sample from the process, respectively. Then we concluded that current density is more concentrated at the edge of pattern and the depth of etched area is proportional to current density.