Abstract
This paper is presented the method that the machine tools spindle preload of fixed position type could be estimated at axial natural frequency even while it is rotating. The establishment of the method of estimating the preload value during the rotation from the axial natural frequency, which has the close relation to the preload value, is tried. First, the preload value is estimated by using the estimated value of bearing temperature during the rotation. Next, the axial natural frequency is estimated by using the preload value. The experiment value shows almost equal to the estimated value. This proves that both analysis and experiment method are suitable.
