Study of Distortion on Milled Thin-Wall Aluminum Parts Influenced by Initial Residual Stress and Toolpath Strategy

Abstract Monolithic aluminium alloy parts are highly required in aeronautical industry, but they show significant geometrical distortion after the machining process. This work investigated the distortion attributed by the initial residual stress of raw material and the machining induced residual stress during the milling process, as well as explored the effects of the machining toolpath strategy. Single-/multi-pocket parts were milled from 7050-T7451 aluminium blocks with different initial residual stress, and an element deletion method was developed for numerical study to simulate different sequences of material removal. It was revealed that the toolpath parallel to the long side of block caused more distortion on the side surfaces of final part. The value of distortion was positively correlated to the magnitude of initial residual stress of raw material. The simulation results indicated that the distortion attributed by machining induced residual stress accounted for about 15% of final distortion. The finding promotes the design optimization of machining monolithic parts by minimizing distortion, thereby benefitting the application of large monolithic parts in industry.