• Title/Summary/Keyword: Externally-pressurized air bearing

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An Effect on the Running Accuracy of the Perpendicularity Error in the Spindle System Supported with Externally-Pressurized Air Bearing (외부가압 공기 베어링 지지 스핀들 시스템에서 직각도 오차가 운전 정밀도에 미치는 영향)

  • 고정석;김경웅
    • Tribology and Lubricants
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    • v.15 no.3
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    • pp.257-264
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    • 1999
  • Recently as electronics and semi-conductor industry develop, ultra-precision machine tools that use air-spindle with externally pressurized air bearing appear in need of ultra-precision products which demand high precision property. Effects of air compressibility absorbs the vibration of shaft, this is called averaging effect, however, the higher running accuracy is demanded by degrees, the more important factor is machining errors that affect running accuracy of shaft. Actually, it would be very important in the view points of running accuracy to understand effects of machining errors on the running accuracy of the spindle system quantitatively to design and manufacture precision spindle system in the aspect that efficiency in manufacturing spindle system and performance in operation. So fu, there are some researches on the effects that machining error affect running accuracy. However, because these researches deal with one bearing of spindle system, these results aren't enough to explain how much machining errors affect running accuracy in the typical spindle system overall. In this study, we investigate the effects of the perpendicularity error of bearing and shaft on running accuracy of spindle system that consists of journal and thrust bearing theoretically, and suggest design guideline about shape tolerances.

Design of Air Turbine and Air Bearing for Dental Handpiece

  • Hwang, Pyung;Park, Sang-Shin;Sohn, Jeong-L.;Kwon, Seong-In;Kim, Do-Hyung;Kim, Woo-Seok
    • Tribology and Lubricants
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    • v.23 no.5
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    • pp.240-247
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    • 2007
  • The design process of the dental handpiece is described. The parameters of the high speed air turbine are estimated. The effect of supply hole on the stiffuess and damping of the air bearing for handpiece is studied numerically. The Reynolds equation is solved by using the divergence formulation and the perturbation method. The test rig is built and the test procedure is developed for the turbine rotational speed measurement by using Fourier transform of noise generated by the turbine during steady operation.

A Method of Accurate Position Control with a Pneumatic Cylinder Driving Apparatus

  • Jang Ji-Seong;Byun Jung-Hoan
    • Journal of Mechanical Science and Technology
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    • v.20 no.7
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    • pp.993-1001
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    • 2006
  • In this paper, a method of accurate position control using a pneumatic cylinder driving apparatus is presented. To overcome the effect of friction force and transmission line, low friction type cylinder applied externally pressurized air bearing structure is used and two control valves attached both side of the cylinder directly. To compensate nonlinear characteristics of control valves, linearized control input derived from the relation between control input and effective area of control valve, and dither signal are applied to the valve. The controller applied to the pneumatic cylinder driving apparatus is composed of a state feedback controller and a disturbance observer. Experimental results show that the effectiveness of the proposed method and position control error of $5{\mu}m$ accuracy could be obtained easily.

A Study on the Load Capacity Characteristics of the Externally Pressurized Air Lubricated Journal Bearings (외압을 받는 공기윤활 저어널 베어링의 부하특성에 관한 연구)

  • 김수태;조강래
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.2
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    • pp.231-240
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    • 1988
  • An investigation is carried out for the load capacity characteristics of the externally pressurized air lubricated journal bearings both theoretically and experimentally. Theoretical analysis is made using the incremental method and the finite element method, and the discharge coefficient is considered. The experiments are performed for five bearings which are produced according to the rows of supply holes and the presence of poket or step. The results are compared with the numerical results. The present numerical results are in better agreement with the available experimental results than any other earlier numerical results for the bearings having one row and two rows of supply holes with pocket. The present numerical and experimental results show that the bearing with step has larger load capacity than that without step and that the load capacity increases as the clearance ratio increases.

Influence of the environments on the movement precision of the guide table using externally pressurized porous air bearing (다공질 정압공기 베어링을 이용한 직진 테이블에 있어 주위환경이 움직임 정밀.정확도에 미치는 영향)

  • 한응교;허석환;노병옥
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.4
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    • pp.721-729
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    • 1988
  • Recently, the precision required by precision manufacturing and machinery related to electronics is within the domain of submicron that it is difficult to evaluate them by traditional measuring equipments and methods. Accordingly, precision of sub 0.1.mu.m super precise position-decision-apparatus and straight-guide air bearing have been researched and they are almost ready to be used. In utilizing straight-guide-table for super-precision-measurement which used externally pressurized porous air bearing as a way of externally pressurized air bearing, the high-precision-straight movement is the most crucial. In this study, the researcher conducted the experimental study with trial manufacture to see how the surrounding temperature and support condition influenced the selection and allocation of the machine composing element which is important to the high-precision-straight movement. The researcher finding showed that when the property of the rail part and support part of the semi-closed slider form is different, the heat generation of the working motor and surrounding temperature influence the high-precision-straight movement significantly and the researcher showed the influence of the condition of central load and eccentric load to the straight movement precision when the support stand of the straight-table was supported by numerical values.