## 2 Materials and Methods
### Material Tests  
The mechanical performance of polymeric materials depends on the manufacturing conditions and may differ from the manufacturer's specified properties [34, 36]. Therefore, the preliminary tests characterized the mechanical performance of the polymeric materials employed in this experimental campaign, which involved PLA and LW-PLA materials from COLORFABB (Belfeld, The Netherlands). For comparison purposes, Table 2 presents the physical properties of the polymeric materials as specified by the manufacturer [37, 38]. In this table, \(E\) is the modulus of elasticity; \(f_{t}\) and \(\epsilon_{u}\) are the tensile strength and ultimate strain; \(T_{g}\) and \(T_{m}\) are the glass transition and melting temperatures; the \(x\) and \(y\) axes determine the filament deposition plane; and \(z\) is the vertical axis. The mechanical tests of both materials in this study employed cylinders with dimensions of \(\mathcal{O}22.6\times 40\) mm\({}^{2}\), fabricated with 98% infill. BAMBU STUDIO software (BAMBU LAB, Version 1.10.1.50, Shenzhen, China) was used to create the fabrication models. All the cylinders were printed using the P1S 3D printer (BAMBU LAB, Shenzhen, China), equipped with a 0.4 mm nozzle and a textured build plate. All samples were built with a layer height of 0.24 mm. The extrusion temperature of the PLA was set to 220 \({}^{\circ}\)C, with a flow rate (FR) of 98% and a volumetric print speed (VS) of 20 mm\({}^{3}\)/s. According to the technical datasheet for PLA and LW-PLA from COLORFABB (Belfeld, The Netherlands), \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multicolumn{2}{c}{\(E\) [GPa]} & \multicolumn{2}{c}{\(f_{t}\) [MPa]} & \multicolumn{2}{c}{\(\epsilon_{u}\) [\%]} & \multirow{2}{*}{\(T_{g}\) [\({}^{\circ}\)C]} & \multirow{2}{*}{\(T_{m}\) [\({}^{\circ}\)C]} \\ \cline{2-2} \cline{5-8}  & \(xy\) & \(z\) & \(xy\) & \(z\) & & \(xy\) & \(z\) & \\ \hline PLA & 3.30 & 3.35 & 70 & 71 & 3.5 & 3.5 & 55–60 & 150–160 \\ LW-PLA & 3.35 (0.86) \({}^{\star}\) & 43 (10) \({}^{\star}\) & 8.1 (12.8) \({}^{\star}\) & 55–60 & 150–160 \\ \hline \hline \end{tabular} \({}^{\star}\)The characteristics correspond to an FFF nozzle temperature of 200 \({}^{\circ}\)C or 250 \({}^{\circ}\)C; the latter values are presented in the brackets.  
\end{table} 
Table 2: Physical characteristics of polymeric materials [37, 38]. the optimal print bed temperature ranges from 50 \({}^{\circ}\)C to 60 \({}^{\circ}\)C [37; 38]. Therefore, this study used a print bed temperature of 55 \({}^{\circ}\)C to ensure proper bed adhesion while minimizing the risk of the sample debonding. The extruder temperature activates the LW-PLA foaming additive and controls the density of the fabricated material [13; 38]. Therefore, the selection of the maximum VS and FR parameters was based on a preliminary calibration program designed to maximize the weight reduction of LW-PLA while maintaining the dimensional stability. The initial calibration program involved four cylindrical specimens with a diameter of 22.6 mm and a height of 40 mm, printed with varying maximum VS values ranging from 5 mm\({}^{3}\)/s to 12 mm\({}^{3}\)/s and FR values from 53% to 98%. The fabrication results showed that the specimen printed at 5 mm\({}^{3}\)/s with a 53% FR had the lowest mass (6.7 g), compared to the heaviest specimen (11.5 g) produced at 12 mm\({}^{3}\)/s with a 98% FR, nearly doubling the weight reduction. An intermediate condition (12 mm\({}^{3}\)/s and 53% FR) yielded an 11.0 g specimen, indicating a limited influence of FR on the weight. Employing VS above 8 mm\({}^{3}\)/s caused significant increases in mass and decreases in foaming effects. These findings are consistent with results reported by [PERSON] and [PERSON] [13]. Based on these insights, the 5 mm\({}^{3}\)/s VS and 53% FR were chosen for the FFF of the LW-PLA components to maximize the weight reduction effect.