SUCTION FORCE ANALYSIS FOR DIGITAL LIGHT PROCESSING-BASED PROJECTION STEREOLITHOGRAPHY

Digital light processing (DLP)-based projection stereolithography is one of the most important photo-polymerization based additive manufacturing technologies that has distinctive advantages such as high-resolution and fast printing speed. But the excessive suction force in the liquid resin film limits the further improvement of printing speed. The existing researches mainly focus on the improvement of the transparent window of the resin tank and the technological process while the mechanism of suction force is poorly understood. In this work, a multi-physical model coupled with resin flow, free radical polymerization and phase transition is established. The evolution process of the resin liquid film is studied under the combined action of mass transfer, photopolymerization, curing deposition and oxygen polymerization inhibition by numerical simulation. It is found that the solid-liquid interface presents a stable non-uniform wave attenuation morphology and the liquid film thickness is small and fluctuates sharply at the boundary which is completely different from the assumption of flat interface in previous research. The effects of elevating velocity, oxygen concentration distribution and UV intensity on the interface morphology and suction force are discussed. The results indicate that increasing the equilibrium concentration of oxygen and decreasing the UV intensity can effectively reduce the suction force while significantly affect the printing precision. We propose that adjusting the distribution of UV intensity can improve the inhomogeneity of the interface morphology and is an effective measure to reduce the suction force and increase the printing speed. This research has important reference significance for the study of different types of photo-polymerization based additive manufacturing technologies.