Exploring the Limits of Low-Cost Metal FFF: Sintering and Porosity Effects in 316L Stainless Steel Parts

Metal additive manufacturing based on Fused Filament Fabrication (FFF) of metal-filled polymers is emerging as a cost-effective alternative to conventional processes such as Metal Injection Molding (MIM), but its industrial relevance remains limited by challenges in densification and mechanical performance. This study presents an exploratory investigation of a low-cost FFF process using 316L stainless steel filament for industrial applications in railway maintenance. A Taguchi L8 design was employed as a screening approach to evaluate the influence of key printing parameters, followed by sintering using both internal and external configurations. The mechanical response depended strongly on sintering temperature: sintering at 1350 °C increased the ultimate tensile strength to 216–278 MPa and Young’s modulus to 63–109 GPa, while the apparent porosity remained between 12.6% and 16.9%. In the exploratory main-effects analysis of variance (ANOVA), none of the investigated printing parameters had a statistically significant effect on the measured responses (p > 0.05). For porosity at 1350 °C, nozzle diameter nevertheless showed the largest descriptive contribution (23.81%, F = 2.06, p = 0.2241). Overall, porosity introduced during the printing stage remained a major limitation of the process. Although the achieved properties remain below those of conventionally processed 316L, the process demonstrates potential for non-structural and cost-sensitive applications. Because each factor combination was tested once, the ANOVA and signal-to-noise (S/N) results are interpreted as exploratory screening and response ranking rather than confirmatory inference or independent evidence of robustness.