Impact of machine factors on the surface quality of parts fabricated via powder bed fusion

Abstract

In the growing additive manufacturing industry, there is increasing demand for improved as-built surface quality of parts fabricated by the powder bed fusion (PBF) process, particularly in the aerospace, medical, and tooling industrial sectors. The surface finish of PBF parts is often suboptimal due to the inherent layer-by-layer fabrication process. Depending on the material used, the average surface roughness (Ra) of PBF components typically ranges from 5 to 50 μm. To address this issue, various strategies have been investigated, including optimizing printing process parameters, refining support designs, and upgrading laser hardware. In this study, we investigated the machine factors on the as-built surface quality of parts in the PBF process. Fully dense as-built 1.2709 tool steel parts were produced with a relative density of 99.9% using platform pre-heating. Without heat treatment, the as-built part exhibited an ultimate tensile strength of 1,135 ± 75 MPa, yield strength of 915 ± 120 MPa, and an elongation of 12 ± 3%. Vickers hardness was measured at 339 ± 35. Surface measurements were performed on parts placed across the substrate plate, with the Ra of as-built vertical walls averaging 22.6 ± 11.9 mm. Results showed that the surface quality of as-built 1.2709 tool steel parts, with a layer thickness of 30 μm, was significantly affected by their distance from the inert gas outlet and the laser center. This study demonstrates that the as-built surface quality of PBF parts can be controlled through more effective build job preparation without changing key processing parameters.

Keywords

Additive manufacturing / 3D printing / Powder bed fusion / Selective laser melting / Surface quality / Tool steel

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