Numerical simulation of thermo-fluid coupling in non-Newtonian polymer melts for fused deposition modeling

The optimization of fused deposition modeling (FDM) traditionally relies on empirical trials, resulting in high cost and limited precision in process control. To overcome these limitations, this study proposes a novel multi-physics numerical model coupling non-Newtonian melt flow dynamics and heat transfer processes. This model employs the Cross-Arrhenius constitutive equation to capture the polymer’s shear-thinning and temperature-dependent viscosity behavior. Simulations reveal that layer height and cooling conditions strongly affect interlayer bonding through internal thermal gradients. A moderate layer height (0.5 mm) yields an optimal deposition morphology by balancing rapid cooling and polymer diffusion, maximizing interlayer bond strength while minimizing residual thermal stress. In contrast, very low (0.25 mm) or high (0.75 mm) layers result in insufficient bonding or large temperature gradients that induce warping. Insulated cooling significantly reduces thermal gradients at moderate layer heights, enhancing interlayer fusion, but is ineffective at extreme heights. The shear-thinning effect of ABS is quantified by a viscosity drop from several thousand Pa·s to 565 Pa·s under high nozzle shear rates (100 ~ 300 s⁻¹), facilitating smooth extrusion. These findings identify optimal deposition conditions and provide quantitative guidance for improving FDM print uniformity and mechanical performance.