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고속 주축베어링의 볼 접촉각 변동을 고려한 주축 설계공차
이찬홍,Lee, Chan-Hong 한국생산제조학회 2010 한국생산제조학회지 Vol.25 No.5
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.
고속 회전시 베어링 강성강하를 고려한 주축 유니트의 최적화
이찬홍,Lee, Chan-Hong 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.1
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.
이찬홍(Chan Hong Lee),하태호(Tae Ho Ha),이재학(Jae Hak Lee) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.10
The FEM analysis of machine tools is the general analysis process to evaluate machine performance in the industry for a long time. Despite advances in FEM software, because of difficult simplicity of CAD drawing, little experience of joints stiffness modeling and troublesome manual contact area divide for bindings, the industry designers think the FEM analysis is still an area of FEM analysis expert. In this paper, the automation of modeling process with simplicity of drawing, modeling of joints and contact area divide is aimed at easy FEM analysis to enlarge utilization of a virtual machine tools. In order to verify the effects of modeling automation, a slant bed type model with tilting table is analyzed. The results show FEM modeling automation method only needed 45 minutes to complete the whole modeling process, while manual modeling method requires almost one month with 8200 calculations for coordinate transformations and stiffness data input.
고속 주축베어링의 볼 접촉각 변동을 고려한 주축 설계공차
이찬홍(Chan Hong Lee) 한국생산제조학회 2010 한국생산제조학회지 Vol.19 No.5
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 of 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 external loads and rotational speed. To analyze internal forces of a bearing under high speed revolution, the ball contact angles 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.
이찬홍(Chan Hong Lee),김양진(Yang Jin Kim) Korean Society for Precision Engineering 2011 한국정밀공학회지 Vol.28 No.8
In this paper, the capability index is introduced in order to improve the reliability of new concept machine tools and the method to improve the machine accuracy from the analysis of cutting process, statistical methodology and influence factors are proposed. In addition, the rib structure of bed and column in machine tools is analyzed by using the thermal impact method in order to analogize the rib pattern which has the small thermal deformation under thermal boundary condition. In the analysis of column rib structure, thermal boundary condition is separated to heat conduction and heat transfer to appropriate real boundary condition. Finally, performance chart of bed and column rib structure is provided for designer to estimate each rib pattern and select rib structure appropriating to thermal condition.