Controlling Surface Finish of Material Extrusion Metal Parts through Optimized Post Treatment Parameters

Material Extrusion (MEX) technology, a cost-effective 3D printing method for the fabrication of complex metal parts, has received considerable interest because it allows parts to be made through multiple steps such as printing, debinding and sintering in a simpler, safer and more cost-effective way than other technologies. However, controlling and predicting surface roughness, crucial for functional parts, remains an open challenge. This is due to the layer-by-layer deposition method that generate a poor-quality surface compromising the performance and limiting the potential applications. In this context, post-treatments aim to modify the characteristics of the as-sintered parts to achieve desired functionalities in terms of mechanical strength, surface finish and functional properties. In the present work, surface mechanical treatments such as compressed air shot-blasting and sand-blasting have been applied on 316L parts realized by MEX. Post process parameters as the size and the shape of the media and the treatment pressure and treatment time were studied using the Design of Experiment approach. The roughness and surface morphology were then analysed as outputs and used as drivers to provide a better knowledge of the effects of surface post treatment process on MEX metal parts. After post treatment, the minimum roughness achieved along the lateral faces was in a range of 4.37-4.85 mu m, respectively - 69.5 and - 62.4% compared to the as-sintered condition, and on the top face 2.44-3.14 mu m, respectively - 55.6% and - 46.7% compared to the as-sintered condition. Furthermore, the combination of an angular shape media, a coarse size media and a high value of pressure (4 bar) changed dramatically the layer-wise surface texture of the samples due to the material removal and consequently weight loss in a range of 2.0-2.5%.