Simulation and analysis of material stacking and migration induced by extrusion behavior in 3D printed concrete

The process of 3D printing concrete using various nozzle configurations will change the shape of the printing strip. However, the fundamental causes behind this impact are still unclear. This study adopts a new perspective and uses computational fluid dynamics (CFD) numerical simulations to analyze the extrusion process under different extrusion angles and nozzle rotation radii from the perspective of differences in the extrusion path of concrete materials. A new material migration analysis model based on the force induced mechanism of material extrusion has been established. By utilizing the deformation of strip cross-sections during experimental and simulation processes and analyzing the migration process of internal concrete materials under different nozzle extrusion angles and printing rotation radii, a quantitative relationship between material extrusion path differences, material migration amounts, and structural deformation variables was determined. In addition, by analyzing the changes in material extrusion pressure and speed during the simulation process, it was found that reducing the material path would increase the constraint of the surrounding structure on the extruded material, leading to an increase in internal pressure and a decrease in internal velocity, thereby further inducing material migration. This indicates that the differences in printing paths caused by different printing extrusion processes of the nozzle are the fundamental factors affecting the structural changes of the printing strip. This study provides a more detailed analysis model and theoretical basis for understanding the material migration process of 3D printed concrete during material extrusion，thereby providing technical guidance for subsequent optimization of multi-layer structure printing. • Established a new material migration analysis model based on the force induced mechanism of material extrusion. • The difference in materials printing paths caused by different printing extrusion processes of the nozzle is the fundamental factor affecting the structural changes of the printing strip. • The behavior changes of material extrusion during 3D printing process were studied using CFD numerical simulation. • The shape of the strip interface was extracted and differentiated analysis was conducted for different cross-sectional shapes.