Laser Beam Polishing of PA12 Parts Manufactured by Powder Bed Fusion

Abstract

Abstract Purpose Multi Jet Fusion™ (MJF) is a powder bed fusion technology that fuses material locally with infrared radiation. Fabricated parts show high mechanical strength, low porosity and good dimensional accuracy, even for challenging geometries. They do, however, have a distinctive grainy surface with a roughness of Ra > 5 μm limiting possible applications. A fairly recent technology for the smoothing and polishing of polymer surfaces is the surface re-melting by laser beam polishing (LBP). The objective of this study is to characterize the LBP-process of MJF-manufactured Nylon PA12 parts and evaluate it in relation to state-of-the-art finishing methods. Methods PA12 samples produced using the Multi Jet Fusion™ process are laser beam polished with a 30 W CO2-laser system. A numerical model is applied in order to estimate the effects of different processing parameters and laser scanning strategies. Calculated temperature progressions are validated experimentally with thermographic measurements. The laser beam polished surfaces are subsequently characterised by surface topography, tensile strength, surface energy and hardness. Results A re-melting and concurrent smoothing of PA12 surfaces was demonstrated for a number of different processing strategies. The use of a line-focus resulted in the best combination of processing speed, flexibility and surface quality with a reduction in roughness of up to 91%. Conclusion Laser beam polishing is applicable to parts manufactured by Multi Jet Fusion™. Depending on the case of application, it can be preferable to conventional post-processing strategies for fusing residual powder and improving tribological properties.