Research On The Dynamic Behavior Of The Spindle-column System Based On The Characteristics Of Key Joints

The chatter produced during the cutting process will seriously affect the surface quality of the parts,tool's lifetime and reduce the working efficiency of the machine tool.Therefore,the machining center should possess good vibration resistance,especially for the advanced manufacturing equipment,like precision horizontal machining center.The spindle-column system is the output end of the dynamic behavior of the precision horizontal machining center,and its dynamic flexibility of the front of the spindle is the key determinant of the vibration resistance,so it can truly reflect the dynamic characteristics of the whole machine.Based on this background,a complete dynamic behavior study is carried out for the spindle-column system of a precision horizontal machining center with principle of structural dynamics and dynamic characteristics of key joints.This research is also combined numerical calculation with physical experiment,and utilize modal flexibility theory.The main research work is as follows.1.Spring element is utilized to simulate characteristic of joints and then a dynamic model of spindle-column system based on the characteristics of key joint is established,including:bolt joints,bearing joints,linear guide joints and 3D model of spindle-column system.2.Using the finite element method,the calculation of the eigenvalue and dynamic response of the spindle-column system is performed and then natural frequency,modal shape,excitation frequency and dynamic response are analyzed.The global stiffness matrix of the system and the modal shapes of each mode are output for the modal flexibility calculation.3.The spatial differentiation characteristics of dynamic characteristics for the spindle-column system is studied,which is about the positions of spindle and spindle box.It shows the relative rate of change for each natural frequency with the positions of spindle and spindle box is less.The amplitude of dynamic flexibility varies in part with the positions of spindle and spindle box.4.Hammering test on the front end of the spindle is conducted,and the experiment results are compared with the results of dynamic response calculations.Most of the errors between experiment and calculation are about 10%,indicating that the dynamic modeling of spindle-column system is relatively accurate.5.Considering that the damping of the joint is difficult to calculate,therefore,the modal flexibility theory which is independent of damping,is used to identify weak mode of the spindle-column system.The results show that weak modes with large modal flexibility are No.2,No.4,No.9,No.12,No.13,No.14,No.21,No.26 and No.27.An orthogonal test optimization method based on joint stiffness distribution is presented to optimize weak modes,but the optimization effect is not effective,and the method needs to be improved.The research results can provide a general method for optimizing the key joint parameters of machine tools and make research approach about improving machine tools' vibration resistance clear.Meanwhile,it can also provide theoretical and engineering support for the optimization of high-speed cutting process parameters.