Distortion discrepancy of large-scale components in electron beam melting processes

Abstract

Amongst many factors that hinder the industry from adopting additive manufacturing technology, dimensional printing error and thermal distortion are crucial, especially for large-scale components (length > 100 mm). Although residual stress in an electron-beam melting (EBM) printed part is relatively low, part distortion cannot be neglected in quality control and post-processing. To investigate distortion rules of EBM parts along the X and Y direction of the build plate, a series of L shape beams, with a length of 130 mm in both X and Y, were designed, printed, and characterized. Both 3D scanning and multi-functional coordinate-measuring machine (CMM) were used to measure designed hexagonal marks with a 10 mm interval along part gauge length. The dimensional error between designed and printed parts was calculated and analyzed. Results showed that the beams shrank orthotopically in terms of X and Y directions in discrepant rules. In the X direction, total shrinkage was around 0.7 %, accumulating with a stable increment. While in the Y direction, the shrinkage was indistinctive without apparent accumulation. We observed a slight wall thickness effect on shrinkage non-uniform accumulation in the X direction. Thin wall structures (T = 1 mm and 2.5 mm) distorted more at the beginning 40 mm of the part length from the origin point than the rest to the rear end. On the other hand, thick wall (T = 10 mm) distorted more at the rear end.