Numerical Simulation and Experimental Study of the Extrusion Process in 3D Printing for High-Viscosity and High-Solid-Content Multicomponent Energetic Materials

A combined approach of numerical simulation and experimental validation was employed to investigate the phenomena of screw adhesion and nozzle clogging, which occur frequently during the material conveying and extrusion process of high-viscosity, high-solid-content multi-component energetic materials in 3D printing. Firstly, conical and cylindrical screws were designed. Through simulation calculations of the energetic material extrusion process, the variation patterns of internal pressure and shear rate within the screw were analyzed, providing guidance for the design of the printing equipment. Secondly, a Z-shaped stirring paddle kneading device and a dual-nozzle printing equipment featuring horizontally and vertically arranged two-stage screws were designed. Through extrusion experiments with PBX slurry, the optimal matching relationship between the kneading rate and the extrusion rates of the horizontal and vertical screws was obtained. Finally, 3D printing of complex-shaped PBX charges using high-viscosity energetic materials was successfully accomplished. This confirms the further optimization of the 3D printing equipment in terms of safety control, precision control, and adaptability to complex structures under extreme operating conditions. The results indicate that: the cylindrical screw outperforms the conical screw, and with a screw clearance of 3mm, it represents the optimal design solution. During the kneading process, a screw rotational speed of 25 rpm was used. After kneading for 3 hours, the slurry exhibited good uniformity, with a solid content of approximately 70% and relatively small deviation. During the extrusion process, a horizontal screw speed of 10 rpm and a vertical screw speed of 12 rpm satisfied the "hungry-type" conveying condition, where the horizontal screw speed is slightly lower than the vertical screw speed. This enabled continuous and stable filament formation of the slurry.