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자성연마슬러리를 이용한 초미립 초경합금(WC-Co 18%)의 나노급 경면가공 특성
곽태수,Kwak, Tae-Soo 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.1
This study has been focused on an effective surface finishing method combining ELID (ELectrolytic In-process Dressing) and MAP (Magnetic Assisted Polishing) for the nano-precision mirror grinding of glass-lens molding mould. ELID grinding is an excellent technique for mirror grinding of various advanced metallic or nonmetallic materials. A polishing process is also required for elimination of scratches present on ELID grinded surfaces. MAP has been used as polishing method due to its high polishing efficiency and superior surface quality. It also presents some techniques for achieving the nanometer roughness of the hard material such as WC-Co, which are extensively used in precision tooling material.
유동방향과 밀도이방성 분석을 위한 세라믹 분말사출성형 해석
곽태수,서원선,Kwak, Tae-Soo,Seo, Won-Seon 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.3
This study has focused on manufacturing technique of powder injection molding of watch case made from zirconia powder. A series of computer simulation process was applied to prediction of the flow pattern in the inside of the mould to clarifying the change of sintering shrinkage depended on flow direction. The material properties of melted feedstock inclusive of the PVT graph and thermal viscosity flowage properties were measured for obtaining the input data in computer simulation. Also, molding experiment was conducted and the results of experiment showed that good agreement with simulation results for flow pattern and weld line location. On the other hand, gravity and inertia effect have an influence on velocity of melt front because of high density of ceramic powder particles in powder injection molding against the polymer injection molding process. In the experiment, the position of melt front was compared with upper gate and lower gate position. The gravity and inertia effect could be confirmed in the experimental results.
곽태수,Kwak, Tae-Soo 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.1
This study has been focused on properties of mirror surface grinding technology by ELID(Electrolytic In-process Dressing) for metal matrix ceramic composites using in high precision mirror for optics. The experimental studies have been carried out to get mirror surface by grinding for composites, Al-SiC, Al-graphite and Mg-SiC. Grinding process is carried out with varying abrasive mesh type, depth of cut and feed rate using diamond wheel. The machining result of the surface roughness and condition of ground surface, have been analyzed by use of surface roughness tester and SEM measurement system. ELID grinding technology could be applied successfully for the mirror-surface manufacturing processes in spite of ductility of metal matrix material. As the results of experiments, surface roughness of Al-SiC(45 wt%) has been the most superior in these experimental work-pieces as 0.021 ${\mu}m$ Ra.
곽태수(Tae-Soo Kwak),곽재섭(Jae-Seob Kwak) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.12
Ceramic particles as polishing abrasives are often used in a magnetic abrasive polishing process because they have strong wear resistance. Non-ferromagnetic ceramic abrasives should be mixed with ferromagnetic iron particles for controlling the mixture within a magnetic brush during the polishing process. This study describes the application of the ceramic particles for the magnetic abrasive polishing. The distribution of the magnetic abrasives attached on a tool varies with magnetic flux density and tool rotational speed. From the correlation between abrasive adhesion ratio in the tool and surface roughness produced on a workpiece, practical polishing conditions can be determined. A step-over for polishing a large sized workpiece is able to be selected by a S curve, and an ultrasonic vibration assisted MAP produces a better surface roughness and increases a polishing efficiency.
곽태수(Tae Soo Kwak),오오모리 히토시(Hitoshi Ohmori) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.6
This paper has been focused in developing of plastic lens with ultra-precision and low birefringence ability using by injection molding simulation tools. The simulation tools, 3D-Timom™ and Asu-Mold™ were applied to visualize indirectly the flow pattern of melted polymer enter the mould and the simulation results are verified as compared with the experimental results. Birefringence and polarized light generated in injection molding process was also calculated for each injection conditions and compared with .the pictures of experimented optical lens go through the polarized light plates device. A spherical radius of plastic optical lens transcribed from profile of mould core surface was measured to estimate the geometrical accuracy for the each injection conditions. It is confirmed that the simulation results about flow pattern and polarized light area coincided in experimental results. It is known that increasing in thickness shrinkage at center of lens, the spherical radius is larger from comparing the graph measured spherical radius and the thickness shrinkage at center of lens.
ELID 연삭 모니터링 시스템의 개발과 구조 세라믹스 적용 사례
곽태수(Tae-Soo Kwak),김경년(Gyung-Nyun Kim),곽인실(Ihn-Sil Kwak) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.12
This study has focused on development of ELID monitoring system and its application to ELID grinding of structural ceramics. ELID monitoring system was consisted of grinding equipment, ELID power supply, grinding wheel, electrode and monitoring program. It can give a real time data to check spindle grinding resistance, wheel revolution, dressing current and voltage in ELID grinding process. The performance of developed system was evaluated by applying to grinding of structural ceramics, silicon carbide and alumina. As the results of experiments, monitored data for spindle resistance and ELID dressing current was useful to check steady-state ELID grinding process. From the comparison of spindle resistance between ELID grinding and conventional grinding process according to change of depth of cut, it could be confirmed that the spindle resistance in ELID grinding was lower than conventional grinding process.
곽태수(Tae-soo Kwak),한태성(Tae-sung Han),정명원(Myung-won Jung),김윤지(Yunji Kim),우에하라 요시히로(Yosihiro Uehara),오오모리 히토시(Hitoshi Ohmori) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.12
This study has been focused on application of ELID lapping process for mirror-surface machining of sapphire wafer. Sapphire wafer is a superior material with optic properties of high performance as light transmission, thermal conductivity, hardness and so on. High effective surface machining technology is necessary to use sapphire as various usages. The interval ELID lapping process has been set up for lapping of the sapphire material. According to the ELID lapping experimental results, it shows that 12.5 kg of load for lapping is most pertinent to ELID lapping. the surface of sapphire can be eliminated by metal bonded wheel with micron abrasives and the surface roughness of 60 nmRa can be gotten using grinding wheel of 2,000 mesh in 4.5 um, depth of cut. In this study, the chemical experiments after ELID grinding also has been conducted to check chemical reaction between workpiece and grinding wheel on ELID grinding process. It shows that the chemical reaction has not happened as the results of the chemical experiments.
곽태수(Tae-Soo Kwak),남우철(Woo-Chul Nam),김유영(Yoo-Young Kim),김경년(Kyung-Nyun Kim),이용철(Yong-chul Lee) 한국기계가공학회 2009 한국기계가공학회 춘추계학술대회 논문집 Vol.2009 No.6
This study has been focused on properties of mirror surface grinding technology by ELID(ELectrolytic In-process Dressing) for structural ceramics using in high precision structural parts on semi conductor manufacturing processes. ELID grinding is an excellent technique for mirror grinding of various advanced metallic or nonmetallic materials as hard to machining materials. The experimental studies have been carried out to get mirror surface for grinding of structural ceramics, SiC, Al₂O₃ and AlN. Grinding process of the ceramics is carried out with varying mesh type, depth of cut and feed rate using diamond wheel. The machining result of the surface roughness and condition of ground surface, have been analyzed by use of surface roughness tester, SEM and three dimensional surface profiler measurement system.
플라스틱 광학렌즈 사출성형에 있어서 수축 변형량 예측을 위한 사출성형 조건 탐색에 관한 연구
곽태수(Tae Soo Kwak),오오모리히토시(Hitoshi Ohmori),배원병(Won Byong Bae) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.2
In the injection molding of plastic optical lenses, the molding conditions have critical effects on the quality of the molded lenses. Since there are many molding parameters involved in injection molding process, determination of the molding conditions for lens molding is very important in order to precisely control the surface contours of an optical lens. Therefore this paper presents the application of neural network in suggesting the optimized molding conditions for improving the quality of molded parts based on data of FE Analysis carried out through CAE software, Timon-3D. Suggested model in this paper, which serves to learn from the data of FE Analysis and induce the values for optimized molding conditions, has been implemented for searching the molding conditions without void and with minimized thickness shrinkage at lens center of injection molding optical lens. As the result of this study, we have confirmed that void creation at the inside of lens is primarily determined by mold temperature and thickness shrinkage at center of lens is primarily determined by the parameters such as holding pressure and mold temperature.