Thermal properties of high speed motorized spindle and their effects

The thermal stability of high speed motorized spindles, which work as core components of high speed machine tools, plays an importants role in machining accuracy. To predict and control the thermal properties of motorized spindles under work condition and their effects on the dynamic characteristics effectively, a bearing thermo-mechanical dynamic model which takes preload methods and thermal responses into account is presented, and then friction loss and support stiffness of the bearing are analyzed. Meanwhile, the electromagnetic loss of built-in motor with actual input power is investigated with the use of electromagnetism. Based on the analyses of heat generation and heat convection boundary condition, a solution procedure is designed to analyze the comprehensive thermo-mechanical dynamic behaviors of the motorized spindle. An overall temperature rise test on a 120MD60Y6-type motorized spindle is carried out to acquire the temperature change law of the key parts. The good agreement between the theoretical results and the experimental data indicates that the proposed models are capable of accurately predicting thermo-mechanical properties of motorized spindles; the thermal displacement of bearing has different influences on support stiffness and natural frequency with various bearing configurations and work conditions respectively; the thermal properties of the system can be improved by selecting appropriate configuration, using proper lubricant oil flow and increasing cooling water flowrate. © 2013 Journal of Mechanical Engineering.