Transient thermal properties investigation for precision bearing-spindle system considering fixed-position preload and lubricant viscosity-temperature effect

Estimating the thermal properties of the precision bearing-spindle system is essential for machine tool operating accuracy and service life. To predict transient temperature field and related heat behavior exactly, an improved thermal network model for the spindle system considering fixed-position preload and lubricant viscosity-temperature effect was proposed. Firstly, the thrust load-axial displacement relationship of angular contact ball bearing was deduced, as well as the difference of bearing inner/outer ring thermal displacement in condition of Double O configuration, and the structural deformation for the spindle system subject to thermal-mechanical effect. Then, the bearing heat generation via the local approach and thermal resistances were calculated, and heat balance equations were derived and solved. Finally, the transient model coupled with heat generation/transfer and structural deformation in service was constructed, and the temperature field and related heat behaviors were obtained. Moreover, the results of theoretical model were compared with those of experiment test, indicating that the bearing temperature rise and spindle end deformation were in good agreement. Meanwhile, the bearing temperature rise, bearing and spindle deformation, and actual preload force were discussed, which had a nonlinear relationship and a positive correlation trend with rotation speed and initial preload. In addition, the assembly status might change with the variation of rotation speed.