Study On Dynamic Characteristics For The Hybrid CNC Machine Tool With Controlled Joint Damping

The thesis originates from a basic application project of scientific and technological programme of Shenyang, whose name is "The new Research on the technique to improve the dynamical stiffness of CNC Machine Tools and inhibit the chatter of CNC machine Tools".Most of parallel robotized machine tools which have been manufactured by our country have the same problems of low dynamic stiffness and machining accuracy, which results from the phenomena including low contact stiffness, little damping, existence of gap in the joint such as spherical hinge and hook joint and so on. Therefore, improving joint stiffness is the basic approach to enhance the dynamic stiffness and machining accuracy of the kind of machine tools. The dynamic stiffness is different when the parallel machine tools exist in different positions in the working place and the dynamic stiffness and ability of anti vibration can be changed with the joint damping. Controlling the joint damping and stiffness can enhance the dynamic stiffness of parallel machine tools and increase their machining accuracy. Choosing the CNC machine tool (3-TPS (RRR)) as research object, established models for dynamics of low-mobility parallel mechanisms and made the theoretical research to determine the effect of joint damping in the whole working place and the variation range of damping values.The main work includs the following aspects:(1)27points were Choosed in the work place of machine tools, and the length of three rods was computed when the machine tools existed in each point according to the inverse kinematics solution of machine tools. Finally, relative geometric models were established in solidworks.(2) Relative geometric models in solidworks.were introduced into ADAMS.(3) It was added color, quality, all kinds of constraints and drivings in ADAMS, and the kinetics models of machine tools.were established.(4) The damping was Examined when the knifepoint of machine tools was between cutting and the work place to make the knifepoint at the least amplitudes, and the approximate range of damping in the joints of machine tools (3-TPS (RRR)) was determined.The effect of damping on the vibration of machine tools when milling was preceded and the coefficient of damping at the least amplitude of machine tools were determined through the vibration analysis of27points in the work place to provide the reference for the increase of machining accuracy and real-time control for vibration of machine tools.