• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.177-180
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• 1993

최근 항공,자동차산업을 필두로 해서 가전산업에 이르는 많은 민수산업에서 경량화를 목표로한 연질금속의 소형 가공물이 급격히 증가하고 있고, 특수조건을 겨냥한 세라믹과 복합소재와 같은 신소재의 개발 및 적용이 활빌히 일어나고 있다. 이와 같은 추세는 생산성 향상과 가공면의 고품위화를 동시에 만족하면서 진행되어야 하므로 고속,고능률 가공시스템이 필수적으로 요구된다. 본 연구에서는 베어링의 예압량,회전속도,열팽창이 베어링의 내.외륜 지름변화에 어떤 영향을 미치는지 분석하고 베어링 제조사에서 추천하는 조립공차가 고속주축의 작동조건에 어느정도 타당한지를 분석하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.282-282
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• 2003

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.105-111
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• 2013

The spindle is the main component in machine tools. The static and dynamic characteristics of the spindle directly affect the machining accuracy of workpieces. The characteristics of the spindle depend on the shaft size, bearing span, built-in motor location, and so on. Therefore, the appropriate selection of these parameters is important to improve the spindle characteristics. This paper presents the analysis of the static and dynamic characteristics and optimization design of a 40,000-rpm high-speed spindle. Statistical analysis for optimization and finite element analysis were performed. This study uses the response surface method to optimize the objective function and design factors. The targets are the natural frequency and displacement. The design factors are the shaft length, shaft diameter, bearing span, and motor location. The optimized design provides better results than the initial model, and these results are expected to improve the static and dynamic characteristics of the spindle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.215-219
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• 1995

요사이 공작기계는 고생산성을 위해 고속절삭과 강력 절삭이 가능하도록 설계되고, 고성능의 Controller를 부착하여 이송과 공구착탈에 필요한 비절삭 시간을 급격히 단축시켜 나가고 있다. 본 연구에서는 공작기계 주축 베어링의 비대칭 벌열의 원인과 발열형태를 이론적으로 예측하고, 실험에 의해 비대칭 발열과 냉각특성 을 운전조건 별로 확인하였다. 또한 비대칭 발열이 주축대의 열변형에 어떤 영향을 미치는지 알기 위해 유 한요소법에 의해 열변위 특성을 분석하였다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.5
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• pp.609-615
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• 2010

Angular contact ball bearings in a high speed spindles are under the extreme conditions, such as high temperature, big centrifugal force and thrust cutting forces. So, the assembly contacts between spindle shaft and inner ring bearings, bearing housing and outer ring of bearings are occasionally unstable at high speed revolution. Furthermore, the ball contact angle of a bearing, which influence stiffness and lifetime of bearings, are changed according to loads and rotational speed. To analyze internal forces of a bearing under high speed revolution, the ball contact are calculated using nonlinear equations in consideration of rotational speed, thrust loads and raceway form. Diameter increase of inner and outer ring by influence factors, such as internal forces to inner and outer ring, centrifugal force and temperature of inner and outer rings are calculated to establish stable state in bearing assembly in high speed spindle. Finally, contribution ratio of influence factor to assembly design tolerance of inner and outer rings are shown and the stable assembly design tolerance are proposed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.717-723
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• 2010

Radial stiffness of angular contact ball bearings are decreased remarkably at high speed revolution, because the inner and outer ball contact angle with races arc changed under the ball centrifugal forces at high speed. In the past, the optimizations of spindle units were done under the assumption of unchanged bearing stiffness for the whole speed range. But the bearing stiffness is changed and the dimension of optimum spindle is also changed with speed. In the design phase, only one model of many optimum spindle models with speed should be selected. As optimization criterion, the area of transfer function at spindle nose is proposed to estimate simply and accurately improvement of dynamic characteristics in spindle units. Finally, according to many analyses of diverse spindle models with decreased bearing stiffness, the spindle with shorter bearing span is better than longer bearing span from the viewpoint of dynamic characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.7-13
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• 2004

초정밀 공작기계의 기능은 초정밀 운동에 의해 대부분 지배된다. 이러한 운동을 생성하는 고정밀 베어링의 운동정밀도는 이미 나노미터 레벨에 도달하고 있으며, 이러한 운동정밀도를 나노미터 레벨의 정밀도로 측정하는 것(정밀나노계측)이 중요한 과제가 되고 있다. 예를 들어, 초정밀선반 등에 있어서, 공기베어링을 대표로 하는 높은 회전정밀도를 갖는 회전축(주축)이 사용되고 있으며, 따라서 이러한 고정밀 주축의 회전정밀도를 나노미터 레벨의 정밀도로 평가하는 기술은 매우 중요하다. (중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.142-145
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• 1993

유정압베어링은 공기베어링과같은 유막의 평균화 효과를 얻을 수 있어 구성부품의 형상오차보다 우수한 회전정도를 기대 할 수 있으며 상대적으로 높은 강성, 부하용량 및 우수한 감쇠특성을 보유하고 있으면서도 비접촉에 의한 무보수, 반영구적 인 수명등의 장점이 있어 정밀도와 강성이 함께 요구되는 연삭기를 중심으로 공작기계 분야에 활발히 응용되고 있다. 본 연구에서는 고정밀도가 요구되는 연삭기용 유정압주축을 시작하고 정특성, 회전특성, 열특성등을 실험적으로 해석함으로서 실용화에 필요한 제변수들의 영향을 정량적으로 얻고자 하였다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.685-691
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• 2011

The Bearing preload units are used for stable rotational movements of high speed spindles. The feeding mechanism of the preload unit is important to prevent overheat of bearings and to keep constant bearing load under thermal deformation of spindle unit. In this study, ball slide guide and ball bush as feeding mechanism of preload unit are selected. The maximum static friction force, radial stiffness and damping ratio of ball slide guide with ball load, ball number and ball size are widely investigated. In conclusion, the surface of ball slide guide must be heat treated to reduce static friction force. The number and size of ball are increased to control sensitive bearing preload force.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.140-147
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• 1996

Machining accuracy of machine tools spindles using the hydrostatic bearing, largely depends on the static stiffness and the thermal deformation of the spindle unit. In this paper, the modelling and static, thermal analysis of the hydrostatic spindles were performed for the relationship between the design variables like the bearing span, overhang, bearing stiffness and static stiffness at spindle. The goal of optimization is the mazimum, static stiffness at spindle nose with lower temperature rise in hydrostatic bearing. Temperature rise of hydrostatic bearing is minimized with the variables of spindle diameter and oil supply pressure. Finally, validity of the proposed algorithm is verified by improving the static, thermal performance of the existing hydrostatic spindles.