Interlaminar bonding assessment in vertical-oriented filament material extrusion bending specimens

Abstract Fused filament fabrication (FFF) is the leading 3D printing material extrusion process renowned for its versatility, affordability and easy production of complex components. Despite its advantages, the bonding quality between layers depends heavily on processing parameters and filament material properties. Using an orthogonal experimental design, this study investigates the effects of three nozzle-dependent variables—flow rate, temperature and speed. Poly(lactic) acid (PLA) specimens, built vertically, were evaluated via 3-point bending tests to assess flexural strength and surface roughness. The results showed that speed had an insignificant effect, while optimal performance was achieved at a 100% flow rate and 227 °C nozzle temperature across speeds of 50–70 mm/s, yielding ~ 67 MPa flexural strength and ~ 13-μm surface roughness. A reduced second-order regression model effectively captured these relationships. By focusing on bonding-related parameters, this work advances the understanding of FFF process optimization for enhanced component properties.