| High-speed machining technology is one of the core technologies for the development of the manufacturing industry,and is the key technology that China needs to break through from a large manufacturing country to a strong manufacturing country.High-speed CNC machine tool is an important carrier of high-speed cutting technology application.High-speed electric spindle is the core functional components to make the machine tool run smoothly and reliably with a high speed.In order to improve the processing quality and efficiency of the parts,improve the spindle stiffness,improve its dynamic and static is the urgent need to solve the problem.In this thesis,we analyze and optimize the factors affecting the rigidity of lathe electric spindle,and propose methods and measures to improve the rigidity of electric spindle,which has certain guiding significance to improve the spindle rigidity and overall performance.Firstly,the structural characteristics and key function design methods of the lathe electric spindle are analyzed,including the design of drive function,analysis of support characteristics,design of lubrication and cooling system,design of dynamic balance and design of key parameters of the spindle with multi-parameter coordination.The influence of bearing support characteristics on the rigidity of the electric spindle is analyzed.Secondly,based on the lathe electric spindle model,a spindle-rotor-bearing finite element analysis model is established to calculate and analyze the static stiffness,solve the maximum deformation of the spindle,and compare with the theoretical calculation results.Verifying the accuracy of the finite element model the parameters affecting the spindle static stiffness are also studied and analyzed and optimized to improve the spindle stiffness and the spindle static characteristics.The dynamics model of the electric spindle is established using the transfer matrix method.Matlab was used to program the solution,and the first six orders of the spindle inherent frequency and vibration pattern were compared with the modal analysis and harmonic response analysis of the finite element method to verify the credibility of the dynamic model.At the same time,the key parameters that affect the spindle’s inherent frequency are analyzed and optimized to improve the dynamic characteristics of the spindle.The influence of bearing preload on the spindle stiffness,inherent frequency and its own service life is comprehensively analyzed to determine the optimal preload range.By modeling the temperature field of the electric spindle,the thermal load and heat transfer coefficient of the spindle obtained from the analysis are used as the boundary conditions,and the temperature distribution of the spindle is solved,and the radial and axial stiffness of the spindle is obtained by the thermal-structural coupling model.The change of water supply conditions on the temperature distribution of the spindle and the change law of the stiffness with the structural temperature field are also analyzed to reduce the thermal deformation of the spindle and improve the stiffness.Finally,based on the bearing support span obtained from the previous analysis has a great influence on the spindle stiffness,a parametric model for the optimization of the electric spindle stiffness is established,and the support span of the electric spindle bearing and the motor rotor position are optimized based on the MOGA multi-objective genetic algorithm respectively,considering the actual assembly situation.The optimized electric spindle static stiffness is improved and the results meet the design requirements by using the first-order inherent frequency for calibration. |
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