Milling Stability Of Thin-walled Structure

Due to the effect of low stiffness value and variation, high order dynamic characteristics, the thin-walled parts in high speed milling is prone to cause chatter, causing poor surface quality and inferior processing efficiency. This paper mainly focus on the following research for thin-walled milling stability:Considering the time-variant stiffness along feed position and the multimodal coupling effect, a variable stiffness dynamic equation is created based on the traditional lumped parameter model. Thus the analytical method in frequency domain cannot cover the effect of nonlinear factors, the direct integration in time domain and the Poincare section are applied to judge the stability. Based on this method, a 3-D stability diagram is established about spindle speed, feed position and adoc(axial depth of cut). And the leading area of different mode is measured on the two dimensional plane consisted of spindle speed and feed position. Besides that, the instability mechanism is analyzed with the full-discretization method.The milling experiment is carried for double clamped thin-walled beam to validated the theory. The experiment result shows that with the change of tool feed position, workpiece surface morphology is completely different. Vibrations resulted form periodic milling force and regenerative effect cause completely different surface appearance, which is in agreement with theory analysis results.The finite element analysis in discrete point is applied in thin-walled pocket to extract the modal parameters. Then the stiffness function is derived through curve fitting. Based on these, a 3-D stability diagram is built, and the stability influence resulting from regenerative effect and feed position is discussed.