• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.235-240
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• 2002

In micro-EBM, it is well blown that RC circuit is suitable for discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, if very low, continuous (or normal) arc discharge occurs, then increases electrode wear and reduces machining speed remarkably. In this paper, RC circuit with transistor is used to micro-EDM. Experimental results show that RC circuit with transistor can cut off continuous (or normal) arc discharge effectively if duty factor and switching period of transistor are set up optimally. Through experiments with varying charge resistance, it can be known that RC circuit with transistor has about two times faster machining speed than that of RC circuit. Especially, it has prominent rise-effect of machining speed in low unit discharge energy, so that a high-quality and high-speed micro-EDM can be realized through RC circuit with transistor.

• 한국정밀공학회지
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• 제21권12호
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• pp.44-51
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• 2004

In a micro-EDM, it is well known that an RC circuit is suitable as a discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, when the resistance is very low, continuous (or normal) arc discharge occurs, electrode wear increases and machining speed is reduced remarkably. In this paper, an RC circuit with transistors is used in a micro-EDM. Experimental results show that the RC circuit with transistors can cut off a continuous (o. normal) arc discharge effectively if the duty factor and switching period of the transistor are set up optimally. Through experiments with varying charge resistances, it is shown that the RC circuit with transistors has about two times faster machining speed than that of an RC circuit.

• 한국정밀공학회지
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• 제27권1호
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• pp.11-17
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• 2010

This study investigates the non-traditional manufacturing process of dry wire electrical discharge machining (EDM) in which liquid dielectric is replaced by a gaseous medium. Wire EDM experiments of thin workpieces were conducted both in wet and dry EDM conditions to examine the effects of spark cycle (T), spark on-time ($T_{on}$), thickness of work pieces, and work material on machining performance. The material removal rate (MRR) in the dry wire EDM case was much lower than that in the wet wire EDM case. In addition, the thickness of workpiece and work-material were found to be critical factors influencing the MRR for dry EDM process. The relative ratios of spark, arc and short circuit were also calculated and compared to examine the effectiveness of processes of dry and wet wire EDM.

• 한국정밀공학회지
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• 제20권9호
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• pp.109-117
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• 2003

With development of high advanced technologies and skills, micro machining techniques also are being more functional and smaller. Some of the recently developed micro machining technologies are micro drilling, micro EDM, WEDG, LBM, micro milling, micro UVM etc. In these micro machining techniques, Micro -EDM is generally used for machining micro holes, pockets, and micro structures in difficult-cut-materials. For machining micro structures, first of all, tool electrode should be fabricated by WEDG process. In micro-EDM, parameters such as peak current, pulse width, duration time are very important to fabricate the tool electrode and micro structures. Developed experimental equipments are composed of RLC circuit with PWM. In this paper, using developed micro EDM machine, the characteristics of micro electro discharge machining are investigated at micro holes, slot, and pocket machining etc. Also the trends of tool wear are investigated in case of hole and slot machining.

• International Journal of Precision Engineering and Manufacturing
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• 제6권2호
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• pp.5-11
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• 2005

Among the micro machining techniques, micro EDM is generally used for machining micro holes, pockets, and micro structures on difficult-cut-materials. Micro EDM parameters such as applied voltage, capacitance, peak current, pulse width, duration time are very important to fabricate the tool electrode and produce the micro structures. Developed micro EDM machine is composed of a 3-axis driving system and RC circuit equipped with pulse generator. In this paper, using micro EDM machine, the characteristics of micro EDM process are investigated and it is applied to micro holes, slots, and pockets machining. Through experiments, relations between machined surface and voltages and between MRR and feedrate are investigated. Also the trends of tool wear are investigated in case of hole and slot machining.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.623-628
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• 2011

마이크로 방전가공은 활용도가 높은 미세가공기술이지만 가공깊이가 증가하면 방전가공 시에 발생하는 가공부산물인 데브리(debris)로 인해 공구 전극과 공작물이 단락되어 방전의 진행이 힘들고 극심한 전극마모가 발생한다. 이를 극복하기 위하여 공구 전극이나 공작물에 진동을 부가하는 진동 플러싱 기술이 개발되었으나 기존의 진동 플러싱 연구는 피에조 액츄에이터를 적용하여 높은 진동수를 발생시키는 것에만 집중하였다. 본 연구에서는 경제적이면서도 유사한 효과를 얻을 수 있는 솔레노이드를 이용한 진동 플러싱을 제안한다. 솔레노이드를 이용한 진동 플러싱은 피에조 액츄에이터를 이용하는 것에 비해 큰 진폭을 얻을 수 있으며 진동수에 대해 독립적으로 설정하는 것이 용이하다. 가공 실험을 통해 솔레노이드를 이용하여 낮은 진동 주파수에서 큰 진폭으로 진동 플러싱하는 방법이 고주파진동 플러싱과 비교하여 경제적이며 충분한 적용효과를 발휘할 수 있음을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1277-1280
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• 2005

A high-aspect-ratio and high-resolution stainless steel shadow mask for organic thin-film transistors (OTFTs) circuit has been fabricated by a new method which combines photochemical machining, micro-electrical discharge machining (micro-EDM), and electrochemical etching (ECE). First, connection lines and source-drain holes are roughly machined by photochemical etching, and then the part of source and drain holes is finished by the combination of micro-EDM and ECE processes. Using this method a $100\;\mu{m}$ thick stainless steel (AISI 304) shadow mask for inverter can be fabricated with the channel length of $30\;\mu{m}\;and\;10\;\mu{m}\;respectively.\;The\;width\;of\;connection line\;is\;150\;\mu{m}$. The aspect ratio of the wall is about 5 and 15, respectively. Metal lines and source-drain electrodes of OTFTs were successfully deposited through the fabricated shadow mask.

• 산업기술연구
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• 제19권
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• pp.1-7
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• 1999

This is the pre-study to pile up the basic technique for the electro-discharge machining in the field of micro-drilling. The machined chips are flowed out from the machining area by the flow arisen from the high speed rotation of the electrode. The cylindrical shape electrode, whose diameter is 0.5mm, is clamped by the three point clamping type clamper and the clamper is attached at the front shaft of the high speed rotating DC motor. The current for machining is controlled by pulse width modulation technique and the machining conditions such as frequency and duty ratio are changed to find out the effect of the variables for machined results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.195-196
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• 2007

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2256-2261
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• 2017

Carbon nanotube (CNT) and alumina ($Al_2O_3$) are synthesized into hybrid composites, and an advanced electrical discharge machining (EDM) system is developed for the machining of hard and conductive materials. CNT nanoparticles are mixed with $Al_2O_3$ powder and the $Al_2O_3$/CNT slurry is sintered by spark plasma. The hardness and the electrical conductivity of the $Al_2O_3$/CNT hybrid composite were investigated. The electrical discharge is controlled by a capacitive ballast circuit. The capacitive ballast circuit is applied to the tungsten carbide and the $Al_2O_3$/CNT hybrid composite. The voltage-current waveforms and scanning electron microscope (SEM) images were measured to analyze the characteristics of the boring process. The developed EDM process can manufacture the ceramic based hybrid composites, thereby expecting the variety of applications.