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MR Polishing과 EP 복합공정에 의한 SUS 304의 표면품위 거동에 관한 연구
하석재(S.J.Ha),이정원(J.W. Lee),홍광표(K.P. Hong),조용규(Y.K.Cho),김동우(D.W. Kim),조명우(M.W. Cho) 한국소성가공학회 2011 금형가공 심포지엄 Vol.2011 No.9
Recently, the magnetorheological (MR) polishing process has been examined as a new ultra-precision polishing technology for mirror surface generation in many applications, such as aspheric lenses, biochips, micro parts, etc. The MR fluids, used for the polishing, consist of DI water based carbonyl iron (CI), nonmagnetic polishing micro abrasive, and required amount of stabilizers. In the process, mixed fluids were supplied into the gap between a rotating wheel (with electromagnetic field) and the workpiece. Then, the micro abrasives contained in the fluids perform material removal action from the workpiece. Such material removal mechanism in the MR polishing is considered as a process governed by the Bingham flow in the contact zone. In this study, generated surface integrities of SUS 304 using MR polishing process was investigated through a series of experiments. And electro-polishing(EP) process was adopted to reduce the micro-scratch after the MR polishing. The morphology of the generated surface is also observed by scanning electron microscope(SEM).
Micro End-milling과 MR fluid Jet Polishing을 이용한 도광판 마이크로채널 제작
이정원(J. W. Lee),하석재(S. J. Ha),홍광표(K. P. Hong),조용규(Y. K. Cho),조명우(M. W. Cho),제태진(T. J. Je) 한국소성가공학회 2012 금형가공 심포지엄 Vol.2012 No.9
Micro parts can be shown its difference of performance according to the surface integrity of final products. Micro burrs which are taking place from micro cutting should remove for the improvement of surface integrity. To resolve this problem, studies for micro deburring have performed actively. Nickel and Brass are commercially used as the LGP (light guide plate) mold materials of three-dimensional optical device for mobile display due to its corrosion and chemical resistance. In this study, micro endmilling process was carried out to generate the burrs, and then the burr height was measured by using microscope. MR jet deburring process was performed onto the edges of nickel and brass by MR jet polishing method which can control the process from the viscosity control of cohesive MR fluid under the applied magnetic field. The jet angle (0°, 30°) and deburring time (1min, 3min, 5min) were chosen as process parameters. Burr height was investigated to draw a conclusion. It was obtained that the deburring result at 0° was better than that of 30°. Finally, all of burrs were eliminated at 0° after 5min.
Si₃N₄-BN계 가공성 세라믹스의 마이크로 그루브 가공특성에 관한 연구
김동우(D-W Kim),조명우(M-W Cho),조원승(W-S Cho),이응숙(E-S Lee) 한국생산제조학회 2005 한국공작기계학회 추계학술대회논문집 Vol.2005 No.-
In this study, the analysis of micro groove machining characteristics of Si₃N₄-hBN composites are performed to optimum micro machining conditions for related applications. As a first step, material properties of the Si₃N₄-hBN composites are invested. Then, a set of micro groove machining experiments are performed to investigate the micro groove machining characteristics with variable h-BN contents and different conditions.
마이크로 크기 노즐을 가지는 MR Fluid Jet Polishing을 이용한 마이크로 금형 채널의 디버링
홍광표(K. W. Hong),이정원(J. W. Lee),하석재(S. J. Ha),조용규(Y. K. Cho),조명우(M. W. Cho),제태진(T. J. J.) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
Micro-burrs are resulting from micro-cutting on the surface. So it is expected to remove them completely and many studies have been performed for deburring. In this study, micro-end-milling was carried out on nickel materials commercially used for optical and display devices. After this micro-machining, the burr heights were measured with a non contact 3D profiler and microscope. Then, deburring was done on the machined edges using the MR fluid jet polishing system according to jet angle and time. Finally, burrs were completely eliminated after 5 min and jet angle 30° of MR fluid jet polishing.
MR polishing에 의한 광경화성수지 성형용 글래스 몰드의 투과율 및 표면품위 향상
이정원(J. W. Lee),김동우(D. W. Kim),조명우(M. W. Cho) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
In general, Light-hardening polymer was used UV nanoimprint technology. A light-hardening polymer was had the problem of poor hardness, durability. In order to overcome the problem of polymer, inter change optical glass. However glass is very manufacture and a lowering of standars transmittance. In order to glass recover was necessary polishing process. The process is magnetorheological fluids polishing. MR polishing has been developed as a new precision finishing technique to obtain a fine surface. Hence, Magnetorheological fluids has been used for micro polishing to get micro parts. This polishing process guarantees high polishing quality by controlling the fluid density electrically. The applied material in experiments is fused silica glass. Fused silica glass is widely used in the optical field because of high degree of purity. For MR polishing experiments, MR fluid was composed with DI-water, carbonyl iron and nano slurry ceria. The wheel speed and electric current were chosen as the variables of analyzing the characteristics of MR polishing process. Outstanding surface roughness of Ra=1.58nm was obtained on the fused silica glass specimen. And originally glass transmittance was recover on the fused silica glass.
MR fluid Jet Polishing 시스템을 이용한 금형코어재료 연마특성에 관한 연구
이정원(J. W. Lee),하석재(S. J. Ha),홍광표(K. P. Hong),조용규(Y. G. Cho),여인규(I. G. Yeo),조명우(M. W. Cho),제태진(T. J. Je) 한국소성가공학회 2012 금형가공 심포지엄 Vol.2012 No.9
Ultra-precision polishing method by using MR fluid was come into the spotlight for the polishing of metal and optical materials. MR jet polishing process can be controlled by changing the viscosity of MR fluid according to imposed magnetic field. The used MR fluid for MR jet polishing process is composed with the mixture of CI particles, DI water, Na₂CO₃, and glycerin. The results can be obtained from the polishing parameters, such as polishing time, magnetic field, stand-off distance, pressure, etc. In this paper, MR jet polishing was applied to polish the nickel and brass surface with the corrosion and chemical resistance. Nickel and Brass mold materials have been used to fabricate the BLU (back light unit) for three-dimensional optical device in mobile display industries. The polishing results were investigated with the polishing time changing. In case of the MR jet polishing, ferromagnetic materials can be able to interrupt due to the cohesive MR fluid more than non-ferromagnetic materials during MR jet polishing. As the results, the surface roughness of brass (Ra=1.82㎚) was better than the one of nickel (Ra=2.24㎚) after 20min.