Post-processing status of ceramic manufacturing
With the rapid progress of "Made in China 2025", the ceramic manufacturing industry has also undergone profound changes and is transforming in the direction of "intelligence and digitalization". After years of development, 3D printing technology has played an increasingly important role in the production process of ceramics, and ceramic printing technology based on various schemes has made great progress. However, due to the particularity of ceramic materials, they cannot be sintered directly like metals in the process of 3D printing. The general manufacturing process is 3D printing, followed by post-processing degreasing and sintering. The following lists and analyzes the status quo of the post-processing market for ceramic 3D printing.
With the rapid development of material technology, computer-aided design (CAD), computer-aided manufacturing (CAM), and other application technologies, ceramic 3D printing technology is also constantly improving. However, based on the particularity of ceramic materials, with the current scientific and technological means, ceramic parts manufactured by PDM, SLA, or other methods should be defined as "ceramic bodies". Ceramic 3D printing technology actually replaces ceramics in the ceramic process. In the traditional "forming process", after the "forming process", processes such as "degreasing" and "sintering" are still required. Only after the "sintering process" is completed, the ceramic powder particles can be densified to meet the performance requirements.
In the ceramic 3D printing process, taking the current typical alumina printing material as an example, photosensitive resin is added to the ceramic slurry as a curing medium and is cured by laser irradiation with a specific wavelength and power, thereby realizing the 3D printing (molding) process of ceramics.
Photosensitive resin as an additive accounts for more than 25% by mass and 45-50% of the volume in the entire printing material. After testing, the shrinkage rate of 3D printing ceramic parts is generally about 20% or higher. However, the mass ratio after molding by traditional molding processes such as injection molding and pressing is generally about 3%, and the shrinkage rate is generally about 10% (taking alumina as an example). Excessive shrinkage makes higher requirements for dimensional control and characterization of ceramic cost. Therefore, corresponding changes need to be made in the post-treatment process of 3D printing ceramic products.
At present, since ceramic 3D printing technology is still in research and development, small-scale trial production, and special industrial applications, there is no large-scale production situation. Therefore, the end-users of ceramic 3D printers generally support experimental small electric heating furnaces as ceramic post-processing thermal equipment. Most of these devices are designed and manufactured using traditional ceramic preparation techniques, with simple structures, and may not have the ability to collect and analyze data; most post-process implementers are mainly focused on material research and development. For ceramic 3D printing technology, ceramic sintering technology Waiting is not proficient. Judging from the current market feedback, the "barrel effect" of ceramic 3D printing is stuck in the post-processing process. With the use of high additives, the large shrinkage rate directly leads to cracking, uneven structural strength, and discoloration. In terms of post-processing issues, this has also led to the delay in the entry of ceramic 3D printing technology into mass production.
It can be seen the importance of inert atmosphere protection sintering in the post-processing process of ceramic 3D printing. After testing, we found that if the traditional sintering process is used to sinter ceramic 3D printed parts, no matter how slow the heating rate is, the product will have more or less cracks, and cracks can be observed throughout the whole body under the electron microscope.
After using inert gas protection, the current controllable temperature rise rate is about 0.8~1 degrees per minute, and an air/inert atmosphere is required. In the later stage, the overall sintering speed will be gradually increased, and the integrated degreasing and sintering atmosphere furnace will be used as the special production equipment for ceramic 3D printing parts to minimize the processing time and reduce the complexity of the operation.
A plan for the status quo
In the post-processing process, the removal of organic grease is particularly important. Incomplete degreasing will directly lead to problems such as product cracking, dyeing, and strength damage. For this, degreasing equipment with vacuum capabilities will be used to reduce the oxidation of organic matter in the traditional degreasing process. The reaction was changed to a thermal cracking reaction, using an inert gas to create a protective atmosphere in the chamber during the degreasing process. And use testing equipment to monitor temperature, pressure, oxygen content, etc. in real-time, and finally form an analysis report to fix the degreasing process of the same type of products.
In view of the current situation of the ceramic 3D printing post-processing market, on the basis of ceramic 3D printing capabilities, a service system integrating degreasing, sintering, data recording, data analysis, and testing of high-fat ceramic green bodies has been established to provide ceramics 3D printing end customers and material developers provide integrated degreasing, sintering process, surface grinding, process verification, and other services after printing, so as to promote the realization of the mass production process of ceramic 3D printing.