Thermal Mechanical Dynamic Characteristic Research Of High Speed Motorized Spindle

High-speed and high-precision are the main development trend of modern manufacturing industry.As the core components of machine tools,high-speed and high-precision motorized spindle determine the overall development level of machine tools.The dynamic characteristics of the motorized spindle has an significant effect on the working accuracy,surface quality and the production efficiency of machine tool.When the motorized spindle is running at high speed,the deformation of the bearing parts caused by centrifugal force,gyroscopic moment and temperature rise not only affects the machining accuracy,service life and capacity of the motorized spindle,but also limits the development of the motorized spindle to a higher speed.In this thesis,combined with the modified quasi-static model of bearing,the spindle dynamic model is established when considering the deformation of bearing and spindle caused by thermal effect and high-speed effect,which is studied by using mathematical modeling,MATLAB programming,numerical analysis.The thermaldynamic characteristic parameters of bearing are analyzed,and dynamic behavior of spindle-bearing system under the influence of thermal-mechanical coupling is studied as well.The main contents are as follows:1.The finite element model of motorized spindle unit is established.According to the structure and size of the motorized spindle,the entity model of the motorized spindle system is established.At the same time,according to the heat generation equation and the heat convection of each component in the system,combined with the boundary conditions of the motorized spindle unit,the temperature field of the system is simulated by the finite element analysis software.The temperature rise values of spindle and bearing components are obtained and verified by experiment test.At last the thermal deformation is calculated.2.A modified quasi-statics model of angular contact ball bearings is established.Based on the analysis and calculation of the thermal balance temperature rise of the motorized spindle and the thermal deformation of the spindle bearing,according to the classical Jones bearing model,considering the radial deformation of the inner ring of the bearing caused by centrifugal force and the thermal deformation of the bearing components caused by the temperature rise,a modified quasi-statics model of bearing is proposed.In this model,the contact load,contact deformation and contact angle between the bearing roller and the inner and outer raceway under various loads arecalculated.The influence of preload on the dynamic characteristic parameters of motorized spindle bearing is studied,and the dynamic supporting stiffness of bearing is obtained when various kinds of deformation are taken into account.3.The dynamic calculation method of spindle-bearing system under thermalmechanical coupling effects are presented.Considering the influence of centrifugal force and gyroscopic moment on bearing stiffness and dynamic characteristics of spindle-bearing system,and the influence of thermal effect on spindle and bearing,based on Timoshenko beam theory and the modified model of bearing and rotating shaft,the dynamic model of spindle-bearing system under thermal-mechanical coupling effects is established.The influence of thermal deformation and stiffness of motorized spindle bearing on the natural frequency and critical speed of spindle-bearing system are analyzed.At last,the factors affecting the natural frequency and the dynamic response of spindle-bearing system are also discussed,which provides theoretical basis and data support for the design and structural optimization of motorized spindle.