Multi-pass adaptive tool path generation for flank milling of thin-walled workpieces based on the deflection constraints

Abstract

In multi-pass flank milling of thin-walled workpieces, deflections of both the workpiece and tool caused by the cutting force jeopardize the geometrical accuracy of the machined part, which is particularly problematic when cutting hard materials, such as titanium super-alloy used for blades on jet engines, as the due cutting force will be exceedingly large. Traditionally, to mitigate the deflection, machining parameters such as feed rate and depth-of-cut are set as constants and selected extremely conservatively, thus severely prolonging the total machining time. In this paper, aiming at reducing the total machining time while refraining the deflection of both the tool and in-process workpiece, we present a new multi-pass tool path generation method for flank milling of thin-walled workpieces at semi-finish and finish machining stages. In our method, both the feed rate and depth-of-cut are allowed to vary in each pass, and they are simultaneously maximized while subject to the given limits on the deflections of both the tool and in-process workpiece as well as the kinematical limits of the machine tool itself. A practical semi-greedy algorithm is then proposed to solve the formulated global optimization problem which includes both the finite element analysis for calculating the workpiece deflection and the meshing operation. Both computer simulation and physical cutting experiments are performed to demonstrate that a substantial saving (over 20%) in total machining time could be realized by the proposed method.