Study of variation in machining induced distortion between different cutting tool manufacturers

Residual stress inherent to stock material is known to cause distortion in large monolithic components. However, as the aspect ratio (height or length to thickness ratio) becomes larger, the effect of machining-induced residual stress (MIRS) becomes prominent. This is especially applicable to aerospace components that often consists of monolithic thin walled geometries machined from large stock plates. Even after years of research, part distortion in the aerospace industry is still considered a challenging problem to tackle. In this study, end mills of the same diameter but procured from different manufacturers are employed to machine thin aluminum plates of 250 microns thickness. The flatness deviation in the final machined part is measured using a structured light 3D scanner. These deviations are attributed to the MIRS generated during milling, with negligible influence of material inherent residual stress, given the thin geometry. Finite element technique is employed to quanitfy the MIRS and compare the effects of various end mills. Significant variation in MIRS, manifested as variation in flatness deviation in the machined plate is hypothesized, and contributes to uncertainties in machining-induced distortion prediction and difficulties in development of distortion mitigation strategies.