Spindle axial thermal growth modeling and compensation on CNC turning machines

Many studies indicate that thermal errors induced by spindle account for about 50–80 % of the total thermal errors of a machine tool due to the continuous rotation of the spindle during machining. The drawbacks of the commonly used axial thermal growth compensation methods for spindles were studied. In the present work, a robust axial thermal growth model for the spindle, based on the temperature variation, is proposed. Considering the exponential trend of the axial thermal growth of the spindle, the suggested model is based on an exponential formula. The results show that the steady value of axial thermal growth is changing with the spindle rotating speed. Therefore, the real-time steady value of axial thermal growth was predicted using the velocity and acceleration of temperature variation in the key point of the spindle. Additionally, the identification method for the parameters in the suggested model was also presented. The environmental temperature variation error (ETVE) and error induced by spindle rotation (EIBSR) were investigated using a CNC turning machine. The results recorded on the two turning machines indicated that high accuracy and strong robustness can be achieved with the suggested model, even when the rotating speed of the spindle changes randomly.