Uniform rate debinding for Si3N4 vat photopolymerization 3D printing green parts using a specific-stage stepwise heating process

Vat photopolymerization is regarded as one of the most promising 3D printing technologies to process ceramics. However, achieving crack-free debinding in ceramic green parts, particularly with larger volumes or cross-sectional areas, presents a great challenge and often represents the most time-consuming stage. Here we develop a specific-stage stepwise heating process based on the multi-component resin system decomposition and the weight loss characteristics to achieve the decomposition of resin with a uniform rate, thereby avoiding cracks due to the severe gas expansion and the increase of dramatic internal stress. A formula about the uniform rate decomposition of resin is established, enabling precise predictions regarding the residual resin weight at different stages during the debinding process. The validity of the specific-stage stepwise heating process is verified through the examination of Si3N4 vat photopolymerization 3D printing green parts, known for being challenging to debinding compared to other ceramic fillers. The crack-free debinding of Si3N4 printed green parts increases in sizes corresponding to the increasing T-value of the specific-stage stepwise heating process. This enables the selection of an appropriate T-value based on the printed green part's wall thickness, thereby enhancing debinding efficiency. Notably, setting the T-value to 1200 min can successfully debinding an 11 mm wall-thickness cube green parts without cracking. The specific-stage stepwise heating process is expected to be versatile across various resin and ceramic systems and plays a crucial role in the comprehensive exploitation of the design freedom offered by ceramic vat photopolymerization 3D printing.