Thermal deformation caused by temperature rise have an influence on the dynamic performance of a motorized spindle. In turn, the change in the dynamic performance will affect the temperature rise and thermal deformation of the system. However, the latter was rarely focused on in the previous literature. Therefore, a thermal network model of motorized spindle is enhanced by considering the thermal-mechanical coupling effect. Then, an iterative method is presented to solve the coupled equations, and a temperature test rig of the motorized spindle is set up to verify the proposed model. The relative error between the predicted and experimental results at two test points decreases by 9.56% and 3.44% after considering the thermal-mechanical coupling effect. The comparison with the experimental results shows that the proposed model with thermal-mechanical coupling effect can obtain a more accurate temperature field than the previous model. Key words: Motorized spindle; Thermal network model; Thermal-mechanical coupling; Temperature field IntroductionMotorized spindle is a core functional component of computer numerical control (CNC). High transmission accuracy is implemented by the spindle system because the spindle is driven by the motor directly. However, the thermal deformation of the spindle system, caused by uneven temperature rise, reduces machining precision and reliability of a motorized spindle [1]. Temperature affects not only the execution accuracy of the mechanical system [2], but also the machining accuracy of the machine tool [3]. To compensate for the error induced by the thermal deformation, an accurate temperature field prediction model of the motorized spindle is essentially studied.The temperature rise of the spindle system usually focuses on thermal characteristics. To date, considerable efforts have been dedicated on the thermal characteristics of the spindle system. As the bases of calculation for the temperature in the spindle system, a thermal-dynamic model of bearings was established by Palmgren [4] and the frictional heat of bearings was calculated by Jones [5]. Thereafter, the thermal characteristics of the spindle system have attracted increasing attention. The temperature in the spindle system was determined through the finite difference model (FDM) by Harris [6], but the thermal deformation of the spindle system was not included in their model. Later, a thermal characteristic model with thermal deformation was developed [7]. The finite element method (FEM) was also used to predict the temperature field of the spindle system [8][9][10].Recently, motorized spindles as a core part of CNC have been concerned. A finite difference model with heat transfer mechanism of motorized spindle was proposed by Bossmanns [11], and the temperature at several locations matched the measured values. Chen et al. [12] developed a thermal error model of motorized spindle and found that spindle temperature has the characteristics of time-varying, nonlinearity, and strong dependence on rotation speed. Affected by...

Thermal deformation caused by temperature rise have an influence on the dynamic performance of a motorized spindle. In turn, the change in the dynamic performance will affect the temperature rise and thermal deformation of the system. However, the latter was rarely focused on in the previous literature. Therefore, a thermal network model of motorized spindle is enhanced by considering the thermal–mechanical coupling effect. Then, an iterative method is presented to solve the coupled equations, and a temperature test rig of the motorized spindle is set up to verify the proposed model. The relative error between the predicted and experimental results at two test points decreases by 9.56% and 3.44% after considering the thermal–mechanical coupling effect. The comparison with the experimental results shows that the proposed model with thermal–mechanical coupling effect can obtain a more accurate temperature field than the previous model.