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1

An experimental study on the determination of optimal lubrication conditions in a high-speed spindle

Park S.-J., Hwang Y.-K, Lee C.-M

Journal of Machine Engineering

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2009

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Vol. 9, No. 2

106--113

EN

The heat generation inside spindles becomes a major factor that limits the allowable maximum rotational speed in machine tools and decreases the cutting quality. It is necessary to accurately estimate the temperature distribution in spindles caused by the heat generation in bearings and its heat transfer characteristics in order to perform the high-speed and high-precision in high-speed spindles. In addition, an accurate correction process is required according to the results of the estimation through investigating the thermal deformation error. A commercial program, MINITAB, was used to establish an experiment plan that analyzes the heat generation characteristics of the spindle system according to the operation and lubrication conditions of the spindle. Also, the change in the outer ring temperature of bearings was measured according to the experimental plan. After establishing a response surface model using the results of the experiment, the estimation equation of the quadratic polynomial model was proposed for determining the optimal lubrication condition. A verification experiment was applied to verify the accuracy of the experimental equation determined by the estimated regression model and the experimental value used in the estimation of the regression model.

2

A study on the optimal design of air pockets in an air bearing applied tilting index table

Lee M.-J, Lee C.-M

Journal of Machine Engineering

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2009

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Vol. 9, No. 2

114--123

EN

The tilting index table has attached to CNC machining center with 3axes, it can be improvement of its performance and its machining efficiency. The tilting index table is a key unit in order to manufacture some non-rotational and 3-dimensional parts, using the conventional machining center. The tilting index table is directly connected to a processing object. Regarding the increase in the deflection of the table, it directly affects processing objects and increases errors and that makes impossible to obtain desired processing precision. Thus, this study performed the shape optimization of air pockets in order to minimize the deflection presented in the existing table. In the numerical optimizing method for implementing optimal design, the general full factorial design and response surface method in the design of experiments were used. A finite element analysis was used for computational experiments in which the finite element analysis was performed by using the ANSYS Workbench, which is a type of commercial FEM tool. In addition, the analysis of the results was performed by using the commercial program, Minitab 15. The results show that the optimum design results is better than those of the initial design.

3

Development of a high-speed air bearing spindle

Ha Y.-H., Lee D.-W., Hwang Y.-K., Lee C.-M.

Journal of Machine Engineering

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2008

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Vol. 8, No. 4

25--31

EN

This paper investigates an air spindle with both radial and thrust air bearings of newly developing one-directional porous materials. At present, orifice type and porous type are adopted for thrust air bearings. Orifice type thrust air bearing is fabricated by machining several micro-holes on a bearing pad bearing, permeability significantly affected by particle size and machining conditions is an important factor of performance, but it is hard to c porosities is suggested. It has many micro-porosities through axial direction, so stable and plenty of air can be supplied to the thrust bearing pad. A radial air bearing also can be substituted by a radial direction porous bearing as the same reason. In case of driving parts, built-in motor type is widely applied. But it needs additional cooling parts to drop heat from a motor. So application of an air turbine drive with light-weight shaft is suggested and additionally it will reduce fabricating cost.