Assessment of material extrusion process parameters on the surface quality enhancement of 3D printed PLA specimens

Abstract This study investigates both pre-process and post-process treatments aimed at improving the surface quality of polylactic acid (PLA) parts produced via material extrusion, commonly known as fused deposition modelling (FDM). FDM inherently produces visible layer lines, resulting in rough surface finishes, particularly in applications like virtual surgical planning (VSP). To address these challenges, the research focuses on optimizing pre-process parameters and evaluating post-process treatments, including thermal annealing and chemical vapor treatments using ethyl acetate (EA) and isopropyl alcohol (IPA). In the pre-processing stage, various printing parameters, such as layer height, nozzle temperature, and outer wall speed, are adjusted to improve surface finish. A 0.1 mm layer height yields the lowest surface roughness (8.523 µm), though it requires longer production times. In contrast, a 0.2 mm layer height significantly reduces printing time (43 min) but results in a slightly higher surface roughness (10.246 µm). Mid-range parameters provide an effective balance between surface quality and production speed. Post-process treatments further enhance surface smoothness. Thermal annealing at 125 °C for up to 4 h significantly reduces surface roughness across all layer heights, eliminating visible layer lines, although dimensional shrinkage occurs. EA vapor treatment shows a marked reduction in roughness, especially for finer layers (0.1 mm), but requires a longer processing time of 83 min. IPA vapor treatment also improves surface finish but is less efficient compared to EA. In conclusion, thermal annealing is recommended for applications where speed is prioritized over dimensional accuracy, while EA vapor treatment is better suited for applications requiring high surface precision despite longer treatment times. Combining optimized pre-process parameters with effective post-process treatments significantly enhances the surface quality of FDM-printed parts.