Characteristics Of The High-speed Lathe Motorized Spindle Based On The Thermal-structural Coupling Analysis

When the lathe motorized spindle operates, its thermal loss of motor and friction heat of bearings will increase the whole system temperature. The bearing system will induce thermal preload under the influence of temperature rise, resulting in increase the bearing preload. The bearing preload directly determines the bearing stiffness, bearing stiffness directly affects the natural frequency and dynamic response of the whole spindle system. The bearing centrifugal force can’t be ignored when the spindle works at high speed. Therefore, by deducing the equation between bearing temperature and thermally induced preload, the coupling model can be established between the lathe motorized spindle thermal characteristics and spindle dynamic. And we analyze dynamic characteristics of the motorized spindle affected by the thermal state.This paper first uses the finite element to analyze the thermal-structure characteristics of the motorized spindle as the ANSYS software for platform. Then pick up the inner ring, ball and outer ring temperature after the steady-state thermal analysis of the motorized spindle to calculate the thermally induced preload. At last, study the spindle dynamic characteristics under the combined effects of the thermally induced preload and the centrifugal force. The main research contents as follows:(1) The bearing friction heat and the heat loss of the motor are calculated. As well as the influences of the initial preload, the initial contact angle, the numbers of rolling body, viscosity of lubricant affect the bearing friction heat. The relationship between the heat transfer coefficient of correlate parts of the motorized spindle and the spindle speed are calculated. The finite element analysis is used to analyze the steady temperature field, transient temperature field and thermal deformation of the motorized spindle as the ANSYS software for platform. Two ways to improve the bearing temperature rise are analyzed.(2) A thermo-mechanical bearing model is proposed to calculate the thermally induced preload. The axial preload of hybrid ceramic angular contact ball bearings is studied and the radial stiffness of bearings is calculated. The influences of the bearing actual preload and radial stiffness are analyzed under the combined effects of the thermally induced preload with centrifugal force. The accurate3D spindle modeling is established at the thermal affects. Be different from the traditional analysis of dynamic characteristics, the spindle model and harmonic response characteristics under the combined effects of the thermally induced preload with the centrifugal force will be studied. The relationship between spindle dynamic stiffness and speed is analyzed. In order to provide theory dynamic characteristics, the maximum dynamic displacements of the front, middle and rear end of the lathe motorized spindle are studied.