Size effects on geometrical accuracy for additive manufacturing of Ti-6Al-4V ELI parts

A comprehensive investigation of the size and geometry dependency of the dimensional accuracy of direct metal laser sintering (DMLS) for Ti-6Al-4V ELI is presented. For features such as walls, squares, tubes, and rods with different sizes, the percent error significantly increases with decreasing the feature size. The polynomial function a t^-b is suggested to describe this size dependency of the dimensional error where a and b are parameters depending on the geometry, material, and DMLS process parameters. This function is used to successfully predict the dimensional error in DMLS of two spinal cages. Therefore, these functions can be used to account for these errors in DMLS by design change or by adjusting DMLS scaling factors. Furthermore, the inconsistency of the DMLS-manufactured dimensions within the feature is shown to be in the same range of the dimensional inconsistency for features located at different positions on the build platform, implying that the location of the feature on the build platform has a negligible effect on the dimensional accuracy. Finally, it is shown that the error in the position accuracy of DMLS-manufactured features is negligible when the size dependency of the dimensional features is considered in the measurements.