Thermal Behaviour in the Stereolithography Process for Al₂O₃ Ceramic Suspension

Abstract

In the process of ceramic stereolithography, the polymerization process of acrylate is exothermic, resulting in changes to temperature of the slurry, which may affect the quality of green parts. In this work, the heat source input in simulation is based on the in-situ measurement of conversion rate and calculated polymerization exotherm. The simulation results showed that the different structures underwent a 1~3°C maximum temperature rise. A thermal infrared detector was used to capture the in-situ temperature changes in entire exposure surface for several structures during the photopolymerization process. The experimental data validated the simulation results and showed that the temperature change and distribution area in the process were related to the exposure structure. The discontinuous structure and the increase of structural boundary length could accelerate the thermal diffusion, thus reducing the heat concentration in the center. Polymerization rate rose marginally with the incident light intensity until at the intensity of 20 milliwatts. Besides, intensity had little effect on the temperature gradient from the center to the boundary of the exposure area. It is inferred that the additional temperature rise after the peak temperature is an indicator of the occurring of secondary photopolymerization during multilayer exposure. And for the same input energy, reducing the exposure intensity and increasing the exposure time to some extent may help improve the degree of secondary photopolymerization. This work provided valuable guidance for the study of the photopolymerization process and structural design of ceramic stereolithography.

Fabrication of silica-based ceramic cores with internal lattice structures by stereolithography

“…In previous studies, different lattice configurations were designed and tested to obtain the optimized mechanical behaviors [27][28][29] . Furthermore, since heat is released during the polymerization of ceramic suspensions with volume shrinkage, it was also found that the accumulation of shrinkage exists as one of the main factors causing the deformation and cracking of the stereolithography-fabricated ceramic parts [30,31] . Therefore, by reducing the volume and therefore lowering the released heat, the lattice structure helps to reduce the shrinkage stress while maintaining the necessary mechanical strength.…”