In order to evaluate the geometrical quality of the samples, the roughness average (RA) and internal diameter (D i ) of the printed samples were determined using image processing techniques as reported in our previous work . The geometrical analysis includes samples with ∆W greater than or equal to -0.8, while samples with ∆W between -0.8 and -1 could not be analyzed. Figure shows the variation in internal diameter determined using the same approach as equation 5, and 0 indicates the exact diameter indicated in the CAD design was achieved. All materials exhibited a diameter reduction ranging from 2-15%. HPLA/NC samples showed less variation in D i possibly due to higher viscosity of the materials. However, it is important to note that most of the HPLA/NC samples failed to be printed and there is significantly less data for these samples resulting in narrow distribution in the box plot. In the instance of HPLA/GNP, which had less viscosity and more over-extrusion compared to HPLA/NC, D i significantly decreased due to over-extrusion of the material and the trend of ∆D i is negatively correlated with the ∆W trend. In case of LPLA/NC that had very low viscosity and slight-underextrusion, the D i found to be closer to the expected value with a variation in the samples due to 21 the under extruded samples. In case of LPLA/GNP, having the lowest viscosity and most significant over-extrusion, all of the samples had decreased D i due to the over-extrusion during printing. These results indicates a direct correlation between viscosity of the samples and ∆D i and a negative correlation between ∆D i and ∆W . RA is significantly higher in HPLA/NC samples, most likely due to under-extrusion, which resulted in unfilled structural gaps. However, when LPLA/GNP displayed significant overextrusion, the RA increased, most likely because to the uneven layers produced. These trends suggest that, while low viscosity or over-extrusion during printing can raise the roughness average by resulting in larger and irregular layers, high viscosity or underextrusion can also increase the roughness average by resulting in unfilled layers during printing. As a result, it is hard to deduce a direct correlation between RA with viscosity, and ∆W .