The increasing need for lightweight, personalized, and sustainable orthopedic braces has motivated the development of bamboo fiber (BF)-reinforced polylactic acid (PLA) composites. In this study, BF/PLA composites were prepared by melt blending. The effects of polybutylene adipate terephthalate (PBAT) toughener, BF content, and a silane coupling agent on the mechanical properties were evaluated, along with their suitability for 3D printing foot braces. The results showed that at a PLA/PBAT mass ratio of 85/15 and a bamboo fiber content of 10 wt.%, the impact strength of the composite reached 7.7 kJ/m². Silane treatment of BF further improved the impact strength, with a maximum value of 11.3 kJ/m² achieved at a silane/BF mass ratio of 2/98. The optimized composite exhibited good printability across nozzle temperatures of 190–210 °C. Printing speed significantly influenced the process; a speed of 35 mm/s enabled successful fabrication of the foot brace, whereas higher or lower speeds led to model collapse due to overheating or cracking caused by insufficient interlayer adhesion. This study successfully developed a bamboo fiber-reinforced PLA composite suitable for 3D printing of orthopedic braces and identified the optimal 3D printing process parameters.

Conventional knee orthoses (KOs) are fabricated from petroleum-based plastics and are difficult to recycle, while filament-based fused deposition modeling is limited by low deposition efficiency and weak interlayer strength for large load-bearing devices. Herein, the authors reported fused granular fabrication (FGF) of lightweight, biodegradable KOs from poly(lactic acid)/poly(butylene adipate-co-terephthalate)/bamboo fiber (PLA/PBAT/BF) composites. Composites with 2, 6, and 10 wt.% BF were melt-compounded using zinc acetate as a transesterification catalyst and directly granule-printed. Rheological and morphological analyses revealed that increasing BF loading raised melt viscosity and elasticity, albeit with local fiber aggregation. Tensile strength decreased from 37.0 to 26.0 MPa with fiber addition, whereas notched impact strength improved from 7.2 to 11.6 kJ/m², attributed to fiber pull-out, interfacial debonding, and matrix plastic deformation. A demonstration KO weighing only 243 g was printed. Printability depended strongly on nozzle temperature and speed: at 40 mm/s, all BF loadings failed, whereas 10 wt.% BF achieved defect-free printing at 220 °C and 30 mm/s. An optimal processing window of 10 wt.% BF, 190–220 °C, and 30 mm/s yielded tough, lightweight, biodegradable, custom-fit orthoses, demonstrating promising potential for rehabilitation applications.