Design against distortion for additive manufacturing

Abstract

This paper presents the methodology and findings of a novel piece of research with the purpose of understanding and mitigating distortion caused by the combined processes of additive manufacturing (AM) and post machining to final specifications. The research work started with the AM building of a stainless steel 316L industrial impeller that was then machined by removing around 0.5mm from certain surfaces of the impeller's blades and hub. Distortion and residual stresses were experimentally measured. The manufacture of the impeller by AM and then machining was numerically simulated by applying the finite element (FE) method. Distortion and residual stresses were simulated and validated. The FE distortion was then used in a numerical procedure to reverse distortion directions in order to produce a new impeller with mitigated distortion. The results have shown that distortions in the new impeller, on average, have reduced to less than 50% of the original non-compensated values.

On Residual Stress Development, Prevention, and Compensation in Metal Additive Manufacturing

“…In work by Yaghi et al [101], a method for mitigating distortion in AM parts was presented. Two stainless-steel 316 impellers of 48.6 mm in height, with the largest diameter being 109 mm, were manufactured via a laser powder bed fusion AM process and then machined to the final geometry, as shown in Figure 28.…”

“…The predicted distortions were applied to the finite element model in the negative direction, and the surface mesh was re-mapped, resulting in a predistorted CAD model for printing. Using the distortion compensation method, the part distortion was reduced from 200 μm to less than 100 μm [101]. It is important to note that the distortion prevention techniques in which the CAD geometry is altered, such that the distortion during manufacture results in an accurate geometry, as seen in References [98][99][100][101], only enables dimensional accuracy; the RSs still remain in the parts.…”

“…Using the distortion compensation method, the part distortion was reduced from 200 μm to less than 100 μm [101]. It is important to note that the distortion prevention techniques in which the CAD geometry is altered, such that the distortion during manufacture results in an accurate geometry, as seen in References [98][99][100][101], only enables dimensional accuracy; the RSs still remain in the parts. While the final geometry of the part is correct, the fatigue life and structural integrity of the part might still be In work by Yaghi et al [101], a method for mitigating distortion in AM parts was presented.…”

“…It is important to note that the distortion prevention techniques in which the CAD geometry is altered, such that the distortion during manufacture results in an accurate geometry, as seen in References [98][99][100][101], only enables dimensional accuracy; the RSs still remain in the parts. While the final geometry of the part is correct, the fatigue life and structural integrity of the part might still be In work by Yaghi et al [101], a method for mitigating distortion in AM parts was presented. Two stainless-steel 316 impellers of 48.6 mm in height, with the largest diameter being 109 mm, were manufactured via a laser powder bed fusion AM process and then machined to the final geometry, as shown in Figure 28.…”

“…The predicted distortions were applied to the finite element model in the negative direction, and the surface mesh was re-mapped, resulting in a pre-distorted CAD model for printing. Using the distortion compensation method, the part distortion was reduced from 200 µm to less than 100 µm [101]. affected [10].…”