Surface tension powered build dimension control in laser additive manufacturing process
This research is aimed at providing insight into the process phenomena that determine the surface finish quality and dimensional accuracy of laser additive manufactured parts. It was found that melt pool fluid flow has a major effect on the sidewall dimensions of the final deposit. Thermocapillary gradient is the main driving force for melt pool flow, and the gradient can potentially be controlled by material composition. Thus, the effects of three characteristic thermocapillary gradients (positive, negative, mixed) on melt pool fluid flows and build geometry are investigated in this study. The work studied mechanisms responsible for sidewall nonuniformity and deposit bulge in detail. The results showed that the bulge in deposit width occurring at the start of the build is reduced by approximately 56 by deposition of material having mixed thermocapillary gradient as compared to the bulge resulting from deposition of material with a negative thermocapillary gradient. Also, melt pool temperature distributions are visualized during laser deposition of five layer single track builds. More accurate build geometry and reduced deposit sidewall bulge can be expected to lead to lower total cost of additive manufactured parts.