Surface form error prediction in five-axis flank milling of thin-walled parts

The dimensional tolerance of flexible, thin-walled aerospace parts can be violated by the excessive static deflections during milling. This paper proposes a method to predict the dimensional surface form errors caused by deflections of both flexible workpiece and slender end-mill in five-axis flank milling of thin-walled parts. The end-mill is modeled as a cantilevered beam. The stiffness of the thin-walled part varies as the metal is removed and the tool-part contact location changes. The time varying stiffness of the thin-walled part is predicted by an efficient structural stiffness modification method that only needs the FE model of the initial workpiece and avoids re-meshing the part at each cutter location. The cutting forces are distributed over both the cutting tool and the part in the engagement zone, and the effect of deflections on the immersion is calculated. The effect of radial runout of the tool is considered in chip thickness, hence in the cutting force prediction. Finally, the cutter and the workpiece deflections are considered to predict the surface errors left on the finished part. The proposed method has been proven in five-axis blade milling experiments. •Dimensional form errors are predicted in five-axis flank milling of thin-walled parts.•Varying static stiffness of the flexible part is efficiently updated without re-meshing as the material is removed.•Effect of the combined tool and flexible part deflections on the cutter-workpiece engagement is considered.•The chip thickness is analytically calculated along the tool axis considering the five-axis process kinematics.•The proposed surface error prediction model is experimentally validated in five-axis flank milling of a sample blade.