Development of a pellet extruder for blending different materials and study on the properties of eco-friendly flame retardant materials printed using a large-scale 3D printer

This study aims to design and fabricate a pellet extruder capable of blending different materials for the application of flame-retardant building materials in 3D printing and to evaluate the properties of eco-friendly flame-retardant materials printed using a large-scale 3D printer. The main content of the research is as follows: To ensure the printing stability of the large 3D printer, the deflection amount of the axis due to the weight of the pellet extruder was verified through structural analysis. This made it possible to achieve stable printing even on a large bed (1000 mm × 1000 mm). Next, a pellet extruder capable of blending different materials was developed to quickly collect initial mixing ratios and temperature data, and specimen printing was conducted using this extruder. The flame-retardant performance and mechanical properties of the printed flame-retardant material were evaluated, and PLA specimens mixed with calcium carbonate at various ratios from 5 to 20% were produced to conduct flame-retardant performance tests and tensile tests according to UL-94 standards. As a result, it was found that the flame-retardant performance improved as the calcium carbonate content increased, and the optimal mixing ratio was derived. Finally, to verify the printing stability of the extruder and large 3D printer, a honeycomb composite structure was printed continuously for 1 h and 30 min, and it was confirmed that continuous printing was possible with a maximum error of 1 mm. The proposed development systems satisfy both stable printing of large composite structures and excellent flame-retardant performance, confirming the potential for use as eco-friendly building material prints.