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Effect of carbon nano tube (CNT) particles in magnetic abrasive finishing of Mg alloy bars
Lida Heng,양균의,Rui Wang,김민수,문상돈 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.12
The Magnetic abrasive finishing (MAF) process is a surface finishing technique in which a magnetic field is used to controlabrasive particles during surface finishing of a material. Because smooth surfaces are required for general use, the magnetic abrasivefinishing process was developed for finishing surfaces. We studied the effect of CNT particles on the surface roughness of aworkpiece. Magnesium alloy bars were used as the cylindrical workpiece and were finished using an MAF process at high workpiecerevolution speeds of 1000, 5000, 10000 and 25000 rpm; diamond pastes with diameters of 0.5, 1, and 3 μm were used forcomparison. The best value for surface roughness was equivalent to treatment at 0.02 μm when 0.01 g of CNT particles wasmixed together with the unbonded magnetic abrasive at 25000 rpm for 20 seconds. CNT particles were applied to the finishingprocess to improve the surface roughness of the material, because they have many advantageous properties such as very highstrength, light weight, elasticity, and high thermal and air stability. CNT particles are particularly effective for the improvement ofMg alloy bar surface roughness in the MAF process.
자성연마입자의 종류에 따른 자기연마 가공특성에 관한 연구
행리다(Lida Heng),김정수(Jeong Su Kim),씨압 잔점난(Chanchamnan Sieb),문상돈(Sang Don Mun) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.6
자기연마법은 자장이라는 “Magnetic Field”의 작용을 정밀가공 및 마무리 가공에 적용한 것으로 이 기술이 적용되면 우수한 정밀가공 제품을 얻을 수 있다. 본 연구에서는 비결합된 자성연마 입자는 전해철분 (#200-㎛), 자성연마 입자(#320 ㎛, KX#620-㎛), 다이아몬드 입자(1-㎛), 연마액으로 구성되었다. 비결합된 자성연마 입자의 혼합물은 4.5 g의 전해철분 (Fe#200 ㎛), 6.5 g의 자성연마 입자 (KX#320 ㎛), 그리고 0.5 ml의 연마액으로 구성되었다. 자성연마 입자는 고경도 Al₂O₃와 자성재료인 Fe 분말을 일정 비율로 혼합하여 결합시킨 일체화한 특수한 분말이다. 실험 결과에 따르면 모든 조건에서 수평과 수직 부분의 표면 거칠기 (Ra) 값의 개선 정도가 달라짐을 확인할 수 있다. (KX#600 ㎛)의 (Fe/Al₂O₃) 입자를 이용하였을 때는 최적 가공시간 24 min 이내에서 수평 부분과 수직 부분의 표면 거칠기(Ra) 값이 각각 0.08 ㎛, 0.09 ㎛의 향상되었으며, (KX#320 ㎛)의 (Fe/Al₂O₃) 입자를 이용하였을 때는 표면 거칠기(Ra) 값이 각각 0.04 ㎛, 0.05 ㎛의 향상되었다. 1 ㎛의 다이아몬드(PCD) 입자를 투입한 조건에서 (KX#600 ㎛ + 1 ㎛)의 (Fe/Al₂O₃/PCD) 입자를 이용하였을 때는 표면 거칠기(Ra) 값이 각각 0.1 ㎛, 0.11 ㎛의 향상되었으며(KX#320 ㎛ + 1 ㎛)를 이용하였을 때는 표면 거칠기(Ra) 값이 각각 0.08 ㎛, 0.07 ㎛의 향상되었다. 이와 같이 (KX#320 ㎛)의 (Fe/Al₂O₃) 입자를 이용하였을 최적 가공시간에서 모든 표면 거칠기(Ra) 값이 0.05 ㎛ 이하로 초정밀 가공이 진행됨을 알 수 있다. [그림 본문 참조]
Rui Wang,Pyo Lim,Lida Heng,Min Soo Kim,Sang Don Mun 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.10
Magnetic abrasive machining (MAM) is a machining technique in which magnetic fields are used to control abrasive tools during the machining process of a material. Due to the development of engineering technologies, various properties such as surface accuracy, dimensional accuracy, and lightweight materials are required in current engineering applications. This study proposes the development of a new ultra-high-speed magnetic abrasive machining technique with the goal of improving the dimensional accuracy, surface accuracy and weight of a material. Moreover, to reduce machining time, this machining method was developed using an ultra-high-speed spindle, capable of rotating up to 80000 rpm. In this study, Ti-6Al-4V (Eli) bars were used as cylindrical workpieces and were machined via magnetic abrasive machining processes with an ultra-high-speed spindle. Results showed that improvements in the diameter and quantity of removed material were the highest at an operational speed of 80000 rpm, followed by 40000 rpm, 20000 rpm and 2000 rpm. The initial surface roughness of 0.21 µm Ra was improved to 0.04 µm Ra at 80000 rpm for 75 seconds. To evaluate the machining capabilities of the ultra-high-speed MAM process in terms of surface roughness, a descriptive statistical method was used. Precision weight data, laser scan micrometer data, roundness data, surface roughness data, and AFM images of the machined surface were recorded and studied.
Effect of temperature on the magnetic abrasive finishing process of Mg alloy bars
Rui Wang,박주현,Lida Heng,김용익,정진용,문상돈 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.5
Experiments were conducted to evaluate the effect of temperature during magnetic abrasive finishing of Mg alloy bars. A magnetic abrasive finishing process is an unconventional finishing technique that has been used to achieve high-quality surfaces with dimensional accuracy. In this study, a Mg alloy bar, which is widely used in automobiles, aircraft, IT, and the defense industry, was chosen as a cylindrical workpiece. The workpiece was then finished with a magnetic abrasive finishing process at three different temperatures, i.e., a cryogenic temperature, room temperature, and high temperature. In the cryogenic temperature condition, liquid nitrogen and argon gas were used as the cryogenic cooling gases in the finishing process; the results from this treatment were compared with those obtained at room temperature and high temperature conditions. At the room temperature condition, the finishing process of the cylindrical workpiece was performed at 24 °C. To carry out the high temperature condition, a hot air dryer was used to maintain a finishing temperature of 112 °C. The experimental results show that the room and cryogenic temperatures could yield excellent performance in terms of the surface roughness. However, in terms of the removal weight and change in diameter, the high temperature condition was found to be superior. In the present research, the improvements of the surface roughness (Ra) at room temperature (24 °C) and cryogenic temperature (-120 °C) conditions were 84.21 % and 55 %, respectively.