The influence of build orientation on the flatness error in artifact produced by direct metal laser sintering (DMLS) process

Additive Manufacturing (AM) involves a set of production processes in which a layer-based material deposition approach to build parts is applied. These technologies are now extensively used in the industry in many cases as the main manufacturing process for making components with high shape complexity. The dimensional and geometric accuracy of the parts manufactured by means of AM are mostly determined by the specific type of additive process employed and the related process parameters. The part orientation in the build space is an important process parameter that has an influence on the stair-step effect and on the need of support structures and the subsequent post-processing refinements. In addition, the position of the part in the build volume may have an influence on the shape. These factors concur to the surface finish and to the dimensional and shape accuracy. In this paper, the flatness error on several surfaces, built on a test artefact ad hoc conceived, has been measured by means of a CMM-based setup in order to quantify the variation of the error in relation to: The orientation of the surfaces with respect to the platform, and the position of the part in the build volume of the AM machine. The test part has been produced by Direct Metal Laser Sintering (DMLS) process using the EOS Stainless Steel GP1. The test artifact has been designed with five flat surfaces at different angles with respect to the building platform. Two specimens were built in the same DMLS session with different position and alignment. The influence of the surface slope on the flatness error has been investigated. Flatness, 3D Roughness and orientation errors (parallelism, inclination, perpendicularity) have been measured and compared between both specimens.