The Effect of Deposition Patterns on the Deformation of Substrates During Direct Laser Fabrication

The deformation of substrate caused by laser scanning pattern during direct laser fabrication (DLF) is ignored in spite of its importance to the final dimension accuracy. In this paper, in order to investigate the effect of deposition pattern on the deformation of substrate during DLF, eight laser scanning patterns are designed to build a cylinder on an asymmetrical IN718 arc substrate, respectively. Deformations of substrates along x, y, z-directions after DLF and heat treatment are compared and discussed. Meanwhile, the maximum displacement in z-direction of each substrate is calculated. Besides, a modified temperature gradient mechanism (TGM) is introduced to understand deformations of substrates under different laser scanning patterns. The results show that the deformation of substrate along z-direction is much larger than other two directions for all scanning patterns. The deformation of substrate strongly depends on x- and y-directional dimension of the substrate when a symmetrical build is fabricated. Compared with contour-offset scanning patterns, raster scanning patterns have distinct directional effect on deformations of substrates. Especially, the deformations of substrates caused by laser fabrication are permanent. In order to improve the fabrication efficiency, to and fro laser scan along the short dimension direction is preferred during DLF for generating the minimum deformation to substrate and reducing unnecessary movements of the working table.