Improving surface quality of SLA 3D printed parts via controlled dip-coating

Abstract

3D printing is useful for rapid prototyping, and is quickly becoming an option to aid in mass manufacturing, whether to make low-volume molds for injection molding and thermoforming or to make unique fixtures. 3D printing via stereo lithographic apparatus (SLA) builds parts by curing photopolymer resins layer by layer. SLA 3D printing is often chosen for its relatively high quality surface finish. However, the average surface roughness of SLA 3D printed parts is in the range of 0.4 to 2 [mu], which is relatively rough compared to that of polishing/finishing processes, typically 0.1 to 0.4 gm. Therefore, the objective of this research is to determine whether controlled dipcoating can be used to improve surface quality of SLA 3D printed parts. Contact profilometer data was collected for SLA 3D printed parts that were dip-coated with varying withdrawal speeds (1 mm/s, 5 mm/s, 0.1 mm/s), printed with different resolutions (0.05 mm, 0.1 mm, 0.2 mm), and angled (0, 15, 30, 45, 60, 75 degrees from vertical). The results suggest that dip-coating is an effective means of improving surface quality, achieving 0.3 to 0.5 micron range of surface roughness. However, validating the effect of withdrawal speed and print resolution as well as how print orientation and geometry can be optimized with dip-coating require further study. The results showed that, in general, dip-coating with faster withdrawal speeds tended to give lower surface roughness, and printing at 0.2 mm resolution gave greatest improvement in surface quality, achieving approximately the same surface quality as the dip-coated 0.05 mm resolution parts. Dip-coating appears to increase surface waviness due to the drainage effect of the dip-coating dominating over the layer by layer print periodicity.