• Title/Summary/Keyword: Air Bearing Surface

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Study on Improvement of Lubrication Characteristics for the Material of Compressor Friction Parts with Nano-oil (나노 오일을 이용한 압축기 습동부 재질의 윤활 특성 향상에 관한 연구)

  • Kim, Sung-Choon;Kim, Kyong-Min;Hwang, Yu-Jin;Park, Young-Do;Lee, Jae-Keun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.10
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    • pp.559-563
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    • 2009
  • Performance of refrigerant oil at the thrust-bearing and at the journal-bearing of a scroll compressor is a significant factor. This paper presents the friction and anti-wear characteristics of nano oil with a mixture of a refrigerant oil and carbon nano particles. The characteristics of friction and anti-wear using nano-oil is evaluated using the disk on disk tester for measuring friction surface temperature and the coefficient of friction. The average friction coefficient of nano-oil was reduced by 60% compared to raw oil under 600 N and 1,000 rpm. It is believed that the interaction of nano particles between surfaces can be improved the lubrication in the friction surfaces. Worn surfaces of frictional specimen were also investigated by the optical and atomic force microscopy. Conclusively, it is expected that wear and friction coefficient of compressor can be reduced by alignment applying nano-oil as refrigerant oil.

Feasibility Study on the New Structure of a Spindle Motor for Hard Disk Drive

  • Kim, Tae-Woo;Chang, Jung-Hwan
    • Journal of international Conference on Electrical Machines and Systems
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    • v.2 no.3
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    • pp.295-299
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    • 2013
  • This paper presents the new structure of a spindle motor for hard disk drive (HDD). It can produce axial force as well as torque without a pulling plate or a pulling magnet required for the normal operation of a hydrodynamic bearing in rotating-shaft structure. The proposed models have different air gap length along the axial direction by changing the thickness of permanent magnet (PM). One has a single slope and the other has double slopes on the surface of PM. For the design of the proposed models, variables are defined and its effects on the motor performances are investigated by 3-demensional finite element analysis (FEA). The equi-performance curves are investigated for the main characteristics of the spindle motor such as generated torque, axial force and torque ripple ratio. The validity of the proposed models is verified by the feasibility study and performance evaluation.

An Experimental Study on the Effect of Wear Particles on the Sliding Behavior of Silver-Coated Bearing Steels (은 박막이 코팅된 베어링강의 마찰거동에 미치는 마모입자의 영향에 대한 실험적 고찰)

  • 양승호;공호성;윤의성;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2000.11a
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    • pp.59-66
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    • 2000
  • An experimental study on the effect of silver particles on the sliding behavior of bearing steels was performed by using a ball-on-disk tribometer. Tests were carried out in ambient air, dry and vacuum. Disks of AISI 52100 were silver-coaled by a thermal evaporation method, and the effects of silver particle transfer on friction were firstly analyzed. In order to understand further the mechanism of silver particles transfer and its effect on friction and wear, pre-compressed silver particles were artificially introduced into the friction interface and the results were compared to those of silver-coated specimens. Results showed that the introduced silver particles produced transfer layers and resulted in low friction. It also showed that this low friction is closely related to the characteristic behavior of transfer layers. Shakedown and rachetting occurred at the friction interface and affected the friction and wear.

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Machining of Repetitive Micro Patterns using Oscillation Micro Milling (진동 마이크로 밀링을 이용한 미세 반복 패턴 가공 기술 연구)

  • Ro, Seung-Kook;Khim, Gyungho;Park, Jong-Kweon
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.5
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    • pp.381-387
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    • 2014
  • This paper introduces a system to machine micro-sized patterns effectively on surface based on micro-milling process using tools with simultaneous rotation and oscillation, oscillation micro milling. To review the effectiveness of proposed concept, we integrated a micro-spindle supported by active magnetic bearings with a precision 3-axis air bearing stage using double-wedge mechanism, and tested this oscillation milling. Two types of oscillation milling were tested, which are linear oscillation milling with a flat end mill and elliptical oscillation milling with a ball end mill with 0.3 mm of diameter. The spindle was rotating 110 krpm and workpiece was moving constant speed of 2~8 mm/sec during the oscillation milling. As the results, multiple oval shape dimples were generated in regular spacing, and the variation of elliptical motion made different shapes of patterns. The results showed that proposed oscillation milling can be successfully used for machining repeated micro-patterns.

Machining characteristics of STS 304 by micro-endmill (소경 엔드밀에 의한 STS 304의 가공특성)

  • Kim S.J.;Hahm S.D.;Kim H.C.;Kim K.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.1261-1264
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    • 2005
  • Recently, as researches and developments for milli-structure and micro machine are actively progressing, manufacturing technologies and skills for tiny small machine parts are getting more important. So, we have been trying to cut using high revolution air bearing spindle and micro-endmill, and studying for magnitude of cutting force, cutting force wave form and surface roughness. We figured out that in 60,000rpm is so slow that cutting is not perfact. Chatter occured to $2\mu{m}/rev\;at\;80,000rpm\;and\;4.4\mu{m}/rev$ at 100,000rpm. We confirmed that spindle run out increased surface roughness at high revolution.

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A High-speed Atomic Force Microscope for Precision Measurement of Microstructured Surfaces

  • Cui, Yuguo;Arai, Yoshikazu;Asai, Takemi;Ju, BinFeng;Gao, Wei
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.3
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    • pp.27-32
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    • 2008
  • This paper describes a contact atomic force microscope (AFM) that can be used for high-speed precision measurements of microstructured surfaces. The AFM is composed of an air-bearing X stage, an air-bearing spindle with the axis of rotation in the Z direction, and an AFM probe unit. The traversing distance and maximum speed of the X stage are 300 mm and 400 mm/s, respectively. The spindle has the ability to hold a sample in a vacuum chuck with a maximum diameter of 130 mm and has a maximum rotation speed of 300 rpm. The bandwidth of the AFM probe unit in an open loop control circuit is more than 40 kHz. To achieve precision measurements of microstructured surfaces with slopes, a scanning strategy combining constant height measurements with a slope compensation technique is proposed. In this scanning strategy, the Z direction PZT actuator of the AFM probe unit is employed to compensate for the slope of the sample surface while the microstructures are scanned by the AFM probe at a constant height. The precision of such a scanning strategy is demonstrated by obtaining profile measurements of a microstructure surface at a series of scanning speeds ranging from 0.1 to 20.0 mm/s.

Effects of Increasing Ambient Temperatures on the Static Load Performance and Surface Coating of a Gas Foil Thrust Bearing (외기 온도 증가가 가스 포일 스러스트 베어링의 하중지지 성능과 표면 코팅에 미치는 영향)

  • Hyunwoo Cho;Youngwoo Kim;Yongbum Kwon;Tae Ho Kim
    • Tribology and Lubricants
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    • v.40 no.3
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    • pp.103-110
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    • 2024
  • Gas foil thrust bearings (GFTBs) are oil-free self-acting hydrodynamic bearings that support axial loads with a low friction during airborne operation. They need solid lubricants to reduce dry-friction between the runner and top foil and minimize local wears on their surfaces during start-up and shutdown processes. In this study, we evaluate the lift-off speeds and load capacity performance of a GFTB with Polytetrafluoroethylene (PTFE) surface coating by measuring drag torques during a series of experimental tests at increasing ambient temperatures of 25, 75 and 110℃. An electric heat gun provides hot air to the test GFTB operating in the closed booth to increase the ambient temperature. Test results show that the increasing ambient temperature delays the lift-off speed and decreases the load capacity of the test GFTB. An early developed prediction tool well predicts the measured drag torques at 60 krpm. After all tests, post inspections of the surface coating of the top foil are conducted. Scanning electron microscope (SEM) images imply that abrasive wear and oxidation wear are dominant during the tests at 25℃ and 110℃, respectively. A quantitative energy dispersive spectroscopy (EDS) microanalysis reveals that the weight percentages of carbon, oxygen, and nitrogen decrease, while that of fluorine increases significantly during the highest-temperature tests. The study demonstrates that the increasing ambient temperature noticeably deteriorates the static performances and degrades the surface coating of the test GFTB.

Machining characteristics of micro end-mill using high revolution (고속회전을 이용한 마이크로 엔드밀의 가공특성)

  • Kim, Kisoo;Kim, Sangjin;Cho, Byoungmoo;Kim, Hyeungchul
    • 대한공업교육학회지
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    • v.31 no.2
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    • pp.350-363
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    • 2006
  • Recently, the micro end-milling processing is demanded the high-precise technique with good surface roughness and rapid time in milli-structure parts, micro machine parts and molding industry. The cutting conditions of micro end-milling has an effect on surface roughness of cutting surface. Therefore this study was carried out to cut stainless steel using high revolution air bearing spindle and micro end-mill and analyze the cutting condition to get the optimum surface roughness by design of experiment. From this study, surface roughness have an much effect according to priority on depth of cut, revolution of spindle and feed.