| With the rapid development of science and technology,ultra-precision machining technology has become one of the important indicators to measure a country's comprehensive strength.Ultra-precision machine tool is one of the most important equipments in ultra-precision machining technology.The spindle of ultra-precision machine tool is directly involved in the machining process,and its rotary precision will directly affect the precision of the machined workpiece.Ultra-precision spindle system is a complex system integrating mechanical structure,servo control system and static pressure system.The stability of each component will affect the dynamic characteristics of the spindle.In this paper,various components of the spindle system of the three-axis ultra-precision machine tools are studied,and the vibration caused by the ultra-precision spindle system itself and the influence of external vibration sources on the spindle are discussed,which provides a certain reference for solving the problem of vibration source identification.First of all,this paper studies the influence of motor on spindle movement in ultra-precision air-floating spindle system,and makes clear the influence of rotor eccentricity of motor on workpiece machining surface.Taking the permanent magnet synchronous motor used in the air-bearing spindle system of ultra-precision machine tools as the research object,the theoretical modeling and simulation research on the unbalanced magnetic pulling force of the motor under eccentric state are carried out,and the variation rule of the unbalanced magnetic pulling force of the motor with eccentric rate is obtained.Establishing a prediction model of workpiece surface three-dimensional topography under the influence of motor eccentricity;The correctness of the model is verified by the experimental method of machining end plane,and the influence law of motor eccentricity on machining morphology is needed to be obtained.Secondly,the ultra-precision aerostatic spindle component is a complex system,so this paper obtains the influence of the bearing capacity and stiffness of aerostatic bearing on the spindle system by establishing the rotor dynamics system model and applying simulation.Furthermore,the finite element simulation of the motor components is carried out,the harmonic frequency of the motor is obtained by Fourier transform of the radial magnetic density of the motor,and the natural frequency of the spindle is obtained by modal simulation of the spindle.Through the comparison of the two frequencies,the resonance of the two frequencies due to the similarity can be avoided.Using the spindle rotation vibration test experiment,the influence of the motor on the spindle vibration is further verified,and the influence rule of the vibration caused by motor on the spindle system vibration is needed to be obtained.Finally,in addition to the vibration caused by the internal components of the spindle system of ultra-precision machine tools,this paper studies the influence of external vibration sources on the workpiece machining morphology when the spindle system is vibrated.The cutting motion equation is established,and the influence law of workpiece surface topography under external vibration is obtained by MATLAB software.Fourier transform is carried out on the diameter direction of the topography by changing the rotation speed of the spindle to obtain the spectrum space of the topography,thus attempting to roughly identify the vibration source;The correctness of the above theory is needed to be verified by the end plane cutting experiment of active vibration. |
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