Abstract: In the process of tissue engineering scaffold fabrication using injecting 3D printing, the viscous fluid material is extruded out with a style of microfilament, which is deposited on a substrate layer by layer. The materials spread, pile up, remelt and solidify as a consequence of the couple effects of gravity, surface tension, viscous force and solidification drag force. Aiming at the above issues, the forming process of scaffold with homogeneously-sized space pores is studied with a CFD approach to research the pore forming mechanism. The results show that the viscous fluid is cooled mainly by the substrate, and heat transfers from the top to the bottom in the scaffold. The fluid’s temperature is lower and the solidification ratio is higher where it’s closer to the substrate. In this paper, under the conditions mentioned, the effect of solidification drag is greater than the viscous force and the surface tension. The viscous fluid spreads and solidifies subsequently when depositing on the substrate. The pores size decreases with the spreading time. With the scaffold layers rising, the overall trend of porosity decreases.

Key words: 3D printing, tissue engineering scaffold, pore forming mechanism, pore size, porosity