Chapter 11 - Mitigation of Distortion in Large Additive Manufacturing Parts

Abstract

Distortion mitigation techniques for large parts constructed by Additive Manufacturing (AM) processes are investigated. Unwanted distortion accumulated during deposition is a common problem encountered in AM processes. The proposed strategies include depositing equal material on each side of a substrate to balance the bending moment about the neutral axis of the workpiece and applying heat to straighten the substrate. Small finite element (FE) models are used to predict the effectiveness of the mitigation strategies in order to reduce computation time and to avoid costly experiments. The strategy of adding sacrificial material is shown to be most effective and is then applied to the manufacture of a large electron beam deposited part consisting of several thousand deposition passes. The deposition strategy is shown to reduce the maximum longitudinal bending distortion in the large AM part by 91%. The small FE models accurately predict the distortion mitigation achieved from the manufacture of the large part. Experimental observations made here, as well as FE model results, suggest that the order in which the balancing material is added significantly affects the success of the proposed distortion mitigation strategy.