| Ball screw feed system as an important part of NC machine tool, it is good or not directly affects the dynamic characteristics of machine tools and machining of the use of performance and quality. Therefore, research dynamic characteristics of feed drive systems, reveal its kinetic parameters on the influence law of the movement stability of the feed system and put forward effective measures to improve the feeding system stability,and to improve the efficiency of NC machine tools and machining accuracy has important significance.This thesis based on the horizontal machining center as the research object, through the ball screw feed system of parametric modeling, studies the influence of feed system dynamic kinetic parameters; to explore identification method of system dynamics parameters through the test data of the working process of feed system; get measures to improve system dynamic performance; finished the following research work.(1) Based on Timoshenko beam theory and the distributed mass method, use the Lagrange equation, establish the NC machine tool feed system dynamics model,The screw is regarded as a lateral, longitudinal and torsional deformation of five degrees of freedom of flexible body we put the screw nut pair and the integration of the screw and the bearing as the group spring damper unit, Show lead screw nut pair and screw combined with bearing preloaded parameters effect the dynamics of the system.(2) Using Ansys Workbench software established the 3D model of ball screw feed system. Through the feed system of modal harmony response analysis, to study the influence of the position of the workbench, screw axial pre-tightening force, bearing pre-tightening force, feed force to the stability of the system vibration. Studying the change of workbench position effect the axial vibration of the system, the analysis results show that the workbench in the middle of the screw position had the greatest influence on the stability of the system vibration; analysis of different axial pre-tightening force on the influence of screw, the results show that increasing the screw pre-tightening force can reduce the axial vibration amplitude of the feed system; By changing the bearing pre-tightening force, we found that increasing the bearing pre-tightening force can improve the system stability of axial vibration. Finally, we analyzed the feed force effect the axial vibration of the system, found that the feed force is bigger, the greater the impact on system stability.(3) Through the secondary development of Siemens 840D system, collect the motor speed, workbench position, servo motor torque current in the working process of the NC machine tool feed system, and put forward the real-time data is used to calculate the workbench movement parameters and driving force of the method. Comprehensive the above theoretical analysis, established the workbench movement calculus equations of motion, put forward movement mechanics parameter identification method. Deal with the experimental data, obtained the workbench in the process of movement velocity and acceleration curve, along with the change of time curve is fluctuating. Analyzes the cause of workbench speed fluctuation is the influence of friction damping and axial stiffness Analyzed the influence of feed rate on the workbench movement stability, the results show that with the increase of feed speed, the more stable the movement of the workbench. Using least squares estimation method, and Matlab software programming, identify workbench movement differential equation system of the axial stiffness and damping. Analysis results show that the workbench from the extreme left screw direction to the middle position, the rigidity and damping is reduced, damping of the workbench show the change of the friction Combined with the result of simulation, advances some measures for improving the stability of the system movement. |
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