Thermal Debinding of Ceramic-Filled Photopolymers

Abstract

Within the large variety of different additive manufacturing technologies stereolithography excels in high precision and surface quality. Using the Digital Light Processing (DLP) Technology a stereolithography-based system was developed, which is specifically designed for the processing of highly filled photopolymers.The powder-filled suspension enables the 3D-fabrication of a so called ceramic green part. In order to get a dense ceramic structure, subsequent thermal processing steps after the 3D-printing process are necessary. First, the polymer-ceramic composites heated up to 400°C. During this processing step, called debinding, the organic components are burned out. The resulting part, consisting of powder particles stabilized by physical interactions, is further heated to sinter the particles together, and the final, fully dense ceramic part is obtained.The debinding step is the most critical process. The used components have different evaporation or decomposition temperatures and behaviors. Thereby a reduction in weight and also in dimension occurs, which depends on the portion and composition of the organic components and especially on the temperature cycle. Furthermore, the physical characteristics of the ceramic powder, such as the particle size and the size distribution influence the debinding behavior. To measure the changes in weight and dimension a thermo-gravimetric (TGA) and a thermo-mechanical analysis (TMA) can be used. To avoid too high internal gas pressures inside the green parts a preferably constant gas evolution rate is seeked. Also the ‘surface-to-volume ratio’ affects the debinding characteristics. Therefore, optimized debinding cycles for specific geometries allow the crack-free debinding of parts with a wall thickness up to 20 mm.

3D Printing of Bioceramic Scaffolds—Barriers to the Clinical Translation: From Promise to Reality, and Future Perspectives

“…Therefore, the key parameter is to ensure uniform distribution of ceramic particles in the organic network until the entire 3D structure is built up [117]. The printed structure has to be calcined to remove the organic components (also called the debinding stage) and subsequently sintered at high temperatures to fuse the ceramic particles [118]. The main advantages of SL are versatility, freedom of design to create constructs with the scale of several microns to decimetre, and high dimensional accuracy.…”

Dense, Strong, and Precise Silicon Nitride-Based Ceramic Parts by Lithography-Based Ceramic Manufacturing

“…In contrast to oxide ceramics, nonoxide ceramics, such as silicon nitride and silicon carbide, need an inert atmosphere during sintering step in order to avoid oxidation. The interaction between ceramics particles at high temperatures induces densification via sintering and, consequently, fully dense ceramics are formed [28,29]. LCM has been demonstrated to be highly capable when it comes to the precision and mechanical properties of the fabricated parts and has already been successfully applied to fabricate complex-shaped ceramics from alumina, yttria-stabilized zirconia, tricalcium phosphate, mullite, silicon oxycarbide and magnesia [30][31][32][33][34][35].…”

The Development of SLA (Stereolithography) and DLP (Digital Light Processing) Technology in China

“…According to the requirements of the dentistry industry, Hangzhou Leyi New Material Technology, A high-tech enterprise specializing in the development, production, sale and service of 3D printing new materials, launched a special model material, and summed up a complete set of practical steps in the related process. The practical and powerful material research and development ability becomes an important part of Hangzhou Shining 3D' s initial solution for digital denture processing [10][11][12].…”