Research On The Effect Of Feeding System Preload On Dynamic Characteristics

Feeding system is an important part of CNC machine tools.Its dynamic characteristic has a great effect on machining accuracy and cutting efficiency of machine tools.Ball screw and rolling bearing are the key functional components of CNC machine tool feeding system.The preload of ball screw and rolling bearing largely determines the rigidity and positioning accuracy of ball screw system,and then affects the machining accuracy and efficiency of CNC machine tools.Based on dynamic characteristic test of feeding system and the electromechanical coupling simulation analysis,the influence of ball screw preload on the dynamic characteristic of feeding system is fully described.In this thesis,the influence of preload on the dynamic characteristic of feeding system is systematically studied with the method of simulation analysis and experiment.The main works are as follows:On the basis of summarizing the preload method of feeding system drive units,taking feeding system test rig as the research object,the influence of nut preload and bearing preload on the rigidity of transmission is studied through theoretic analysis.A quantized multi-index integrated evaluation method is proposed and the electromechanical coupling dynamic model of feeding system is established.The effectiveness of electromechanical coupling dynamic model is verified by simulation analysis and dynamic characteristic test.The influence of nut preload and bearing preload on the dynamic characteristic of feeding system is systematically studied on feeding system test rig through simulation analysis,and the best preload range of bearing and nut is obtained.The simulation results provide a theoretical basis for the assembly of feeding system and improvement of dynamic characteristic.Based on the above work,a high precision horizontal machining center is taken as an example,the electromechanical coupling dynamic model of feeding system is established based on the modal order reduction method.And the best preload range of nut and bearing is obtained through simulation analysis,which lays the foundation for the assembly and adjustment of the feed drive units.