Dynamic Modeling Of Metal Turning Process And Its Dynamic Characteristic Analysis

Chatter and dynamic characteristic of machine tools are main factors that affect the surface quality of metal-cutting workpiece, and the cutting chatter is more easily to occur when slender shaft is been turning on account of its large length-diameter ratio, weak support stiffness and so on. Therefore, establishing accurate model of the slender shaft’s turning process to research effect of critical factors on vibration amplitude and analysis the dynamic characteristic of machine tool have been the hot issues among related scholars. So far, the existing dynamic model cannot reflect the true cutting force and cannot be applied to the slender shaft; the dynamic characteristic simulation results of machine tools are inaccurate due to neglecting the joints’ influence. In allusion to the above problems, this paper established the dynamic model of the slender shaft’s turning process based on transverse and longitudinal vibration theory respectively, researched the influence of cutting parameters and slender shfat’s size on vibration response by simulation in MATLAB, conducted an experiment to verify the correctness of simulation results; built a finite model of a milling machine considering its key joints’ stiffness parameters, and carried out related modal analysis, harmonic response analysis and experiment research. The main research contents of this paper are as following:(1)This research established the transverse dynamic model of the slender shaft’s turning process. A dynamic model of the slender shaft’s turning process was built based on transverse vibration theory, and the shaft’s vibration response aroused by cutting force was obtained according to the vibration model. The influence of cutting parameters and shaft’s size on vibration response was researched by simulation in MATLAB software. A three-level orthogonal experiment was conducted with cutting depth, feed speed and rotate speed selected as variables to analyze their effect on cutting force. The simulation and experiment results reveal the transverse dynamic characteristic of the slender shaft’s turning process.(2)This research established the longitudinal dynamic model of the slender shaft’s turning process. The longitudinal dynamic equations of the slender shaft’s turning process was built based on longitudinal vibration theory, and the shaft’s vibration response aroused by cutting force was obtained according to the vibration equations. The influence of cutting point and shaft’s quality on dynamic characteristic of the cutting system was researched through theoretical modal analysis in ANSYS.(3)This research built a finite element modal of a CNC milling machine considering its key joints’ parameters and conducted its dynamic characteristic analysis. With a three-axis CNC milling machine determined as research object, dynamic modeling method of its feed drive system was discussed, fixed and rolling joints’ stiffness parameters were calculated. A finite element model of the CNC milling machine was established, the correctness of the FE model and the stiffness calculation method of rolling joints were verified by the comparison of theoretical and experimental modal analysis of machine workbench. Under the two modeling methods of joints that taking stiffness parameters into consideration and connecting joints rigidly, theoretical modal analysis of workbench, spindle system and milling machine were implemented separately, harmonic response analysis of spindle system and workbench were conducted, and the results were analyzed and discussed.