STABILITY LIMITS OF HIGH SPEED MILLING SYSTEM CONSIDERING TIME-VARYING STIFFNESS AND GYROSCOPIC EFFECTS

摘要

High-speed milling (HSM) of thin-walled workpieces is widely used in the manufacturing of airframe components. The prediction of stable milling region plays an important role in the machining process. However, the prediction of its stable milling faces more difficulties as HSM is characterized with time-varying, nonlinear, multi-field coupling. In this paper, a dynamics model of HSM system was set up considering the influence of gyroscopic moment due to high rotating speed of spindle-tool and time-varying stiffness due to high material removal rate of workpiece. A method was proposed by transforming time-varying stiffness system into fixed-step time invariant one. The dynamic characteristics and chatter stability of time-varying high speed milling were predicted and the influence of time-varying stiffness of workpiece on system stability was analyzed. Then the stability lobes diagrams (SLD) considering the above two effects was elaborated and a 3D SLD considering the stiffness as the third coordinate is proposed. The results shows that the gyroscopic effects due to high rotating speed and timevarying workpiece stiffness during the milling process have non-ignorable impact on the stability limitation, which must be considered for predicting stability limit in the high speed milling.