The Chatter Stability In Marble Milling With Robotic

With the continuous improvement of living standards,the demand for stone carving products is increasing.China's stone carving products are mainly made by workers holding semi-automatic tools.Low processing efficiency,poor processing environment,serious pollution lead to the lack of labor force.Using robotic for the machining of stone carving products has become the main development trend of green and efficient process.However,the surface vibration and abnormal damage of tool caused by the chatter hindered the popularization and application of the robot stone carving processing.In this paper,the problem of regenerative chatter in the process of robotic milling marble is studied.The milling forces with the change of the machining parameters have been measured with the force measuring system.It is found that the influence degree of different process parameters on the milling force in different directions is different.The milling force coefficient is obtained by calculation.Using single point excitation single point pickup method,the change of modal parameters of different machining positions is measured,and it is found that the natural frequency of tool in x direction is always lower than that in y direction,and the change trend of damping ratio and modal stiffness is opposite.The identification of modal parameters of robotic milling system is completed.The robotic milling system is simplified into a two-DOF vibration system,the model of robotic milling chatter is established by using Zeroth Oder Approximation;the influence of the system stability is analyzed with the modal parameters,process parameters and machining positions.It is found that the natural frequency has litter effect on the stability of the system;the stability of the system increases with the increase of damping ratio or modal stiffness;the stability of the system decreases with radial depth or the tangential cutting force coefficient or the cutting force coefficient ratio(K_r)increase;the system stability of different machining positions is affected by the combination of all modal parameters.Three-dimensional chatter stability lobes diagram under different working conditions are plotted,and the results are important for the marble machining with robotic.