Multi-response Optimization of 3D Printing Parameters for Enhanced Mechanical Performance of Polylactic Acid Using Response Surface Methodology and Grey Relational Analysis

Fused filament fabrication (FFF) is a versatile technique used for the additive manufacturing of polymeric parts. It requires precise control of printing and structural parameters to produce parts with desired mechanical performance and low thermal expansion. No comprehensive study has addressed the simultaneous optimization of thermal and mechanical properties using optimum 3D printing parameters through grey relational analysis (GRA). The study investigated the effect of printing parameters including layer height (0.2 mm and 0.3 mm), layer orientation (0°, 45°/-45°, and 0°/90°), and infill density (40%, 50%, and 60%) for controlled thermo-mechanical properties. The printed parts were analyzed for tensile, flexural, and impact properties along with coefficient of thermal expansion. Response surface methodology (RSM) was used to analyze the results and identify the significant parameters and develop predictive models for each response. The analysis showed that increasing the infill density from 40-60% (at 0.2 mm layer height, 0° orientation) enhanced tensile strength 31.3% to 31.81 MPa and flexural strength 26% to 62.37 MPa and reduced coefficient of thermal expansion 13.6% to 58.13 × 10⁻⁶/K. Layer orientation 0° outperformed 45°/-45° (at 0.2 mm, 60% infill) with the tensile strength 59.8% and flexural strength 26.5% and reduced the coefficient of thermal expansion 8.5%. The layer orientation 45°/-45° has the greatest impact strength 10.38 kJ/m². Meanwhile, decreasing the layer height from 0.3 to 0.2 mm (at 0° orientation, 60% infill) enhances the tensile strength 4.3% and flexural strength 12.8% and reduces the coefficient of thermal expansion 12.4%. Grey relational analysis (GRA) was performed for the multi-response optimization, to get the combination of process parameters with optimum properties. The results showed highest grey rank (GR) for the sample with 0.2 mm layer height, 0° orientation, and 60% infill density. The outcomes of this study provide insights to produce application-specific components and engineer tailored properties for reliable use of additive manufactured components.