Research On Vibration Characteristics Of NC Machine Tool Servo-system

The structure of NC Machine Tool is more complicated as high accuracy requirements. The problem of machine vibration causes serious concern. Machine vibration affects machining quality and cutting speed, furthermore, it makes a shorter life of tool and machine. Therefore, this paper foci on the study of vibration characteristics of the NC machine tool servo-system.First, Permanent Magnet Synchronous Motor is analyzed with the finite element software.The magnetic fields with no load and load are calculated and compared. The wave figures of radial flux density, tangential flux density, radial force density and tangential force density varied with position are gotten. Rotor of rotation is controlled by the program for a better research on the changes of motor magnetic field. The wave figures of radial flux density, tangential flux density, radial force density and tangential force density varied with time was drawn. Then the changing regulations of transient magnetic field were derived. Motor torque ripple resulted from motor tangential flux density, so the motor torque ripple and the torque waveform figure are got basing on the analysis of magnetic field of motor. On this basis, an effective method of suppressing motor torque ripple is proposed. The motor torque ripple is reduced by changing the parameters of motor stator slots The Optimal parameters are obtained from multiple results comparison. The calculation and analysis provide the basic design reference for the permanent magnet synchronous motor.Secondly, cutting vibration of machine tool is calculated. According on the generating mechanism of cutting vibration, the limits of cutting width are calculated by analytical method in different speed. It provides references for actual machining. Natural frequencies are extracted through modal analysis of cutter system with the finite element software. The cutting system deformation is also analyzed.Finally, the influence of stiffness and deformation of ball lead screw system on the vibration characteristics of NC machine is explored. The stiffness of ball lead screw system is calculated according to the calculation formula. The ball lead screw deformation results from cutting force and motor torque ripple. The figures of the screw deformation changing in one cycle are drawn by transient dynamic analysis with the finite element software, which shows more directly the ball lead screw deformation.