Research On Chatter Stability Of Six-Degree-of-Freedom Milling Robot

With the development of China’s intelligent manufacturing technology,the robot processing system,which the industrial robots especially six-degree-of-freedom(DOF)robots have been widely favored in sorting,spraying,drilling,milling,etc.Six-DOF robots have the advantages of high flexibility,large working space and low cost compared to traditional machine tools.However,the low stiffness characteristics caused by the multi-joint tandem structure of the robot make the robot prone to chatter during milling,which in turn affects the processing quality and efficiency of the workpiece,and even affects the service life of the robot and the electric spindle.In order to avoid the occurrence of chatter in robot milling,this paper,the mode simulation model of the ES165 D robot is established,and the dynamic characteristics of the robot in different poses are analyzed.The regenerative effect and the mode coupling effect are comprehensively considered,and the stable domain model of the robot milling chatter is established.The effect of milling parameters on the chatter stability of the robot is chatter studied and finally verified by experiments.The main research contents are as follows:(1)The kinematic model of the six-DOF robot is established.Through the analysis of the structure and working range of ES165 D robot,the D-H kinematics model is established.The forward and inverse kinematics equations of the robot are derived,and the Jacobian matrix of the robot is constructed.(2)The mode simulation model of the six-DOF robot is established,the dynamic characteristics of the robot in different poses are analyzed,and the acceleration frequency response function is obtained by harmonic response analysis,and the mode parameters are further identified.Finally,the accuracy of the established robot mode simulation model and simulation results is verified by hammer experiment.(3)Considering the regenerative effect,modal coupling effect and feed rate at the same time,a dynamic milling force model of the robot is established.Based on the milling force model and the mode parameters of the robot,the chatter stability domain model is established by using the full discrete method(FDM),and the stability lobe diagram(SLD)of the milling processing system is further obtained,which can realize the prediction of the stable milling processing area.Finally,whether to consider the influence of mode coupling effect on the chatter stability of robot milling is analyzed,and the experimental verification is carried out.(4)The influences of spindle speed,axial depth of cut,radial depth of cut and feed rate on the stability of robot milling were studied by using the combination of stability lobe diagram(SLD)prediction and experiment.The influence of feed rate on machining stability under two working conditions of low-immersion radial depth of cut and highimmersion radial depth of cut is discussed.The research results can help process personnel select reasonable milling parameters and suppress chatter during milling.