This study focuses on optimizing the processing parameters for fabricating polylactic acid (PLA) composite samples reinforced with short micro carbon fibers using fused filament fabrication (FFF) 3D printing. The primary aim is to improve the impact strength and density of the printed composites by employing statistical optimization techniques. The Box–Behnken design was utilized to analyze the effects of three key parameters – nozzle diameter (0.4 mm, 0.6 mm, 0.8 mm), cooling fan speed (0%, 50%, 100%) and printing temperature (200°C, 210°C, 220°C) – on the mechanical properties of the PLA composites. Experimental evaluations were conducted to identify optimal parameter combinations and assess their influence on impact strength and density. The results demonstrated that increasing the cooling fan speed enhanced impact strength, while higher printing temperatures caused a decline in mechanical performance due to thermal degradation. Nozzle diameter had a significant impact on both impact strength and density, with specific optimal combinations of parameters yielding desirable outcomes. The optimal settings identified were a 0.4 mm nozzle diameter, 100% cooling fan speed and 200°C printing temperature, achieving an impact strength of 41.7 kJ/m2 and a density of 561.7 kg/m3. This research highlights the successful application of the Box–Behnken design for optimizing FFF-3D printing parameters in PLA-based composites. The findings contribute to the development of advanced PLA composite biomaterials with enhanced performance characteristics for biomedical applications.
