Design of experiment to optimize the printing parameters on tensile properties of 3D printed ethylene vinyl acetate (EVA)

Extrusion 3D printing by virtue of its versatility and low cost, attracted boundless research interest over time. However, flexible polymers present challenges in conventional filament feed fused deposition modeling (FDM) and require unique extrusion strategies. Fused granulate fabrication (FGF), employing screw-driven extrusion printing, offers a solution where pellets can be directly extruded to create intricate geometries, especially for soft-elastomeric parts. In the present study, flexible ethylene vinyl acetate (EVA) was 3D printed by FGF technique and the effect of process parameters on ultimate tensile strength (UTS) and % elongation at break (EB) were studied. A full factorial design of experiment (DOE) was performed by selecting five control factors namely printing temperature, wall line count (WLC), infill density, and raster angles R₁y and R₂y to determine the relationship between control factors and output and to rank the effect of control factors. According to DOE, printing temperature, WLC and infill density have strong effects on UTS, whereas printing temperature and WLC strongly affect EB. The DOE also revealed significant interactions among the control factors to maximize UTS and EB. The maximum achieved values for UTS and EB are 14.2 ± 0.4 MPa and 492 ± 37%, respectively. Additionally, a transfer function was developed to accurately predict the tensile properties of 3D printed EVA, which aligned well with experimental results. Overall, this study provides valuable insights for researchers to predict the tensile behavior of flexible polymers for various applications with high precision.