Laser surface polishing of 3D printed polylactic acid (PLA) with different levels of absorption

Abstract

Fused deposition modeling (FDM) based 3D printed polymer parts have received extensive attention in the in-dustries. However, their high surface roughness due to the intrinsic layer deposition method limits the appli-cability, necessitating the printed parts' post-processing. Herein, we used colored (white, blue, and gray) 3D -printed polylactic acid (PLA) parts and investigated the color influence on the laser polishing process in detail. Interestingly, the level of laser absorption at an irradiated wavelength of 1060 nm differed in the order of PLA-gray > PLA-blue > PLA-white. Laser-polished PLA-white samples showed a negligible difference in the arithmetic average surface roughness (Ra) compared to the printed sample, corresponding to the low absorption level and melting behavior. On the other hand, the laser-polished PLA-blue sample exhibited a 96.4 % reduction in Ra value at a laser power of 15 W. The PLA-gray sample showed a 98.6 % reduction at 3 W. The Ra variation of the laser-polished samples confirmed a dramatic surface roughness improvement that could be made by con-trolling laser processing parameters and varying light absorption levels of the colored PLA substrates. Besides, PLA-blue and PLA-gray samples had different polishing conditions; Scanning electron microscope (SEM) images, thermal studies, and finite element model simulation results confirmed the polishing and melting behavior of the PLA samples. The comparative experimental results followed by statistical analysis also showed the significant effect of PLA color and laser parameters such as the power and scan speed. Through the advantages of the highly improved laser finishing results with optimal process parameters considering the different light absorption, this approach will broaden the application of efficient laser polishing of 3D printed materials.