多约束状态下重载机械式主轴有限元建模及模态分析

重载机械式主轴是重型数控(Computer numerical control,CNC)机床摆角铣头的关键功能部件,具有大功率、大扭矩特点,用于加工大型复杂曲面零件。其有限元建模及模态分析的准确性是主轴进一步动力学分析的基础。基于Timoshenko梁理论建立重载机械式主轴的运动方程,采用有限元法得到主轴的矩阵形式的动力学方程;在有限元软件中分别以实体单元和梁单元对主轴进行有限元建模,对轴承以Combin14弹簧单元建模,并以自由模态和实际工况约束条件下进行重载机械式主轴的模态分析;根据轴承型号计算轴承的径向刚度,作为重载主轴模态分析中弹簧单元的刚度参数;进行主轴锤击模态试验,验证重载机械式主轴多约束状态下模态分析建模及仿真结果的正确性。研究表明,把主轴考虑为Timoshenko梁单元和Beam188梁单元进行主轴有限元建模和模态分析时,结果更为准确,弹簧约束梁方式更符合实际情况。研究结果为重载机械主轴系统的进一步优化设计和精度控制提供依据。

Finite Element Modeling and Modal Analysis of Heavy-duty Mechanical Spindle under Multiple Constraints

The heavy-duty mechanical spindle is a key functional component of the milling head of heavy computer numerical control(CNC) machine tool,which is used for processing the large and complex parts with free-form surface.The spindle has the characteristics of high torque and high power.The accuracy of finite element modeling and modal analysis of the spindle is are the basis of further dynamic analysis of spindle.The kinetic equation of heavy-duty mechanical spindle is established based on Timoshenko beam theory,and dynamic equations of spindle in matrix form are gained by finite element method.Spindle is meshed by solid element and beam element respectively in finite element software,and bearing is meshed by Combin14 spring element.The modal analysis of heavy-duty mechanical spindle is performed in the boundary of free and actual constraints.Radial stiffness of bearing is calculated based on bearing type,which is the stiffness parameter of spring element in spindle modal analysis.Modal experiment of spindle by hammer exciting is performed,and experiment results agree well with the simulated results of spindle under multiple constraints.The research results show that the Timoshenko beam and Beam188 are more accurate and the case of beam constrained by spring is according with the reality for the heavy-duty spindle modeling.The results provide basis for further optimization design and precision control of heavy-load duty mechanical spindle system.