• 소성∙가공
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• 제14권3호
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• pp.251-256
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• 2005

3-D micro structures and micro tools were fabricated using Micro Electrical Discharge Machining (MEDM). To make micro structures, micro electrical discharge milling process was applied. During micro electrical discharge milling, electrode (tool) worn in the both axial and radial direction. To compensate tool wear which has significant influence on machining accuracy, machining path overlapping was proposed. Machining characteristics of micro electrical discharge milling was investigated in considering of depth of cut and capacitance of discharge circuit. Micro complex shaped tools were also fabricated using REDM (reverse electrical discharge machining). Sacrificial electrodes were machined through electrical discharge milling process and were used as electrode to make micro tools. Using this process several micro tools shape of 'ㄷ', 'ㅁ' and 'o' were fabricated. With these complex shaped tools, micro machining was successfully applied repeatedly.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제3회 금형가공 심포지엄
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• pp.255-259
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• 2004

3-D micro structures and micro tools are fabricated using MEDM (Micro Electric Discharge Machining). To make micro structures, micro electro discharge milling process is applied. During micro electro discharge milling, electrode (tool) wears both axial and radial direction. To compensate tool wear which influences significantly machining accuracy, overlap machining path is proposed. Machining characteristics of micro electro discharge milling is investigated in considering of depth of cut and capacitance of discharge circuit. Micro complex shaped tools are fabricated using REDM (reverse electro discharge machining). Sacrificial electrode is machined through electro discharge milling process and is used as electrode to make micro tools. Using this process several micro tools shape of 'ㄷ', 'ㅁ' and 'o' are fabricated. With these complex shaped tools, micro machining is successfully applied repeatedly.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.1080-1084
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• 2001

In manufacturing a micro die with half spherical cavity by MEDM, it is necessary to prepare an electrode with the same shape. This paper suggests a simple method to manufacture a half spherical electrode based on tool wear. The tool wears more rapidly at the edge of a cylindrical electrode. In order to make a half spherical micro electrode, cylindrical electrode was fed into the workpiece by the distance of its radius. The d/R(depth/Radius) value varied with respect to capacitance and electrode diameter. The smaller the size of electrode was, the closer the electrode tip geometry approached to a half sphere.

• 한국정밀공학회지
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• 제22권7호
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• pp.47-53
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• 2005

Microholes with high aspect ratio are required in microstructures. Among various methods for producing the microhole, micro electrical discharge machining (MEDM) is very effective and useful process. But, it is difficult to machine the high aspect ratio holes below $100\;{\mu}m$ in diameter because machining condition becomes unstable due to bad removal of debris at deep hole. In this paper, ultrasonic vibration is applied to MEDM work fluid to make a high aspect ratio micro hole. It is shown that the vibration is effective in circulating the debris and increasing the machining rate. As a result, produced was a micro hole with $92\;{\mu}m$ entrance diameter, $81\;{\mu}m$ exit diameter and aspect ratio 23.

• 한국대기환경학회지
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• 제26권3호
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• pp.298-304
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• 2010

In order to calculate the aerosol bulk densities of $PM_{1.0}$ and $PM_{10}$, aerosol mass and number concentrations were measured for the period of December 2008~April 2009. $PM_{1.0}$ and $PM_{10}$ mass concentrations were measured using a cascade impactor (Micro-Orifice Uniform Deposit Impactor, MOUDI) while their volume concentrations were calculated based on number concentrations from an environmental dust monitor (EDM). Normal aerosol size distribution fitting functions were retrieved for number size distribution since aerosols < $2.5{\mu}m$ were measured from the EDM. Strong correlation was found between $PM_{1.0}$ mass and volume concentrations obtained with a $R^2$ of 0.95. The calculated average bulk densities of $PM_{1.0}$ and $PM_{10}$ were $1.97{\pm}0.33g/cm^3$ and $2.15{\pm}0.18g/cm^3$, respectively.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.60-63
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• 2009

Manufacturing technologies of micro spur gear and micro mold by micro PIM were studied with stainless steel feedstock. For molding of gears, micro mold with gear cavity of 1.2 mm in diameter was produced by wire EDM. The proper injection pressure was selected to 70bar by observation and measuring of shapes and shrinkage of gears before/after sintering. For fabrication of micro mold, a tiny polymer gear was produced by injection into the mold. Then, 316L feedstock was again injected/compressed on the polymer gear and debinded together with polymer gear followed by sintering. As a result, another metal mold with gear cavity reduced to about 20% was fabricated and through repetition of this process chain, micro gear mold with cavity about below 800 um was finally obtained. In reduction of size by injection/compression molding, height of gear tooth was shrunk more and the effort for decrease of roughness of micro cavity were carried out ultrasonic polishing and as a result, the roughness in cavity decreased from 3-4 um to about 200 nm.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.490-493
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• 2004

There is great difficulty in machine below 10 micrometers by conventional machining methods, such as micro-EDM. However, ultra micro machining using focused ion beam(FIB) is able to machine to 50 nanometers. Bie ＆ moulds techniques are better than one-to-one machining techniques in regards to production costs in the mass production of ultra size structures. Also, it is advantageous to machine die ＆ moulds to the 10 micrometers level by FIB technique rather than other techniques. It is difficult to machine the three dimensional machining, such as micro lens, using FIB system because of their machining characteristics. In this paper, three dimensional machining techniques were properly introduced, and also experiments showed effectiveness of their techniques.

• Design & Manufacturing
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• 제2권5호
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• pp.39-42
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• 2008

The Paper discussed the effects of working electric current and pulse when using super hardend alloy drill as corona electrode. The discharge effect can be obtained very precisely in the ranges of 1A - 2A in working current. $12{\mu}s-14{\mu}s$ in dis charge pulse on time width and $8{\mu}s-10{\mu}s$ in discharge pulse off time.

• 한국추진공학회지
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• 제11권6호
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• pp.42-49
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• 2007

본 연구에서는 마이크로 추진장치의 개발을 위한 기초연구로 마이크로 노즐의 유동 특성을 분석하였다. 냉가스 추진원리를 이용하였으며, 추진 장치의 노즐 목 직경이 1.0, 0.5, 0.25 mm 인 마이크로 노즐을 방전가공을 이용하여 제작하였다. 판스프링과 스트레인 게이지를 이용한 추력측정장치를 이용하여 추력을 측정하였으며, 대기압 환경과 진공환경에서 마이크로 노즐의 유동특성을 분석하였다. 추진제는 아르곤과 질소를 사용하였으며, 실험 결과를 CFD 결과와 비교하였다. 연구 결과 노즐의 소형화로 인해 점성과 배압에 의한 유동손실이 발생함을 확인할 수 있었다.

• 한국정밀공학회지
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• 제23권6호
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• pp.52-56
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• 2006

Punching tools like an electrodes are made by milling or etching or EDM. These methods had time consuming, low efficiency and air pollution. So, we have developed a shearing device which counter punching method for burrless cutting of micro wire. Using the straightened SUS304 wire with $200{\mu}m$ diameter, we confirmed the tendency of the shear plane for punch tools. It was impossible to completely remove the bun in the shearing process. In order to minimize the burr size and fine shear plane, we have accomplished the various experiment conditions such as the U-groove, the effect of the counter punch, shear angle and clearance. The results of the experiments show that indentation, slip plane and bent shape were related to the shear angle and clearance.