Abstract: 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 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-duty mechanical spindle system.

Key words: Constraint, Finite element modeling, Heavy-duty, Modal analysis, Spindle