Improvement of Surface Finish for Additive Manufactured Parts - A Comparison Study of Six Post Processing Techniques

Abstract

The surface finish of additively manufactured parts is often poor mainly due to the “stair-stepping” effect of the manufacturing process which is mostly influenced by the layer thickness, build orientation and the inclination angle of the surface on the part. For form, fit or functional purposes, the surface finish of additive manufactured parts must often be enhanced. The aim of this research is to compare the surface finish of additively manufactured polymeric parts when post-processing techniques are applied. The test pieces were additively manufactured in nylon polyamide 12 (PA12), Alumide® and Acrylonitrile Butadiene Styrene (ABS) materials. The Laser Sintering (LS) process was used to manufacture the nylon and Alumide® test pieces while Material Extrusion (MEX) was used for the ABS test pieces. Six post processing techniques, namely tumbling, shot peening, Computer Numerical Control (CNC) machining, spray-painting, undercoat and hand finishing and chemical dissolving of surface of the test pieces were applied to the test pieces. Despite being the most time-consuming technique and producing poor consistency in dimensional accuracy, the hand finishing method resulted in the lowest surface roughness with improvements of up to 97.6%, 96% and 98.3% for nylon, Alumide® and ABS test pieces, respectively compared to the originally manufactured parts. Although CNC machining has the potential to improve the surface finish of a single face, the technique was found to be not efficient for improvement of surface roughness of a complex part with various inclination angles.