3D printing technology is also called Additive Manufacturing (AM) or Rapid Protoyping (RP). It is a material printer using digital technology, based on digital model files, using powdered metal or plastic, etc. Adhesive material with tackiness, and finally the technology of solidifying and bonding 3D models to construct objects by layer-by-layer printing or layer-by-layer printing. As a moldless molding technology involving multiple disciplines such as CAD modeling, machinery, lasers and materials, it can theoretically realize the commercialization of any item. This technology was once regarded as one of the important signs of the third industrial revolution. In reality, the foundation of 3D printing technology operation is the establishment of 3D models. The commonly used modeling software is Maya and 3dsmax, and the designed 3D models need to be converted into the stl file format of 3D printer molding technology.
Application of 3D printing technology in ceramic industry
Traditional ceramic molding methods including dry molding, plastic molding and grouting molding, etc., require the use of pre-made molds to prepare ceramic products with a certain shape and strength, which takes a long time and high cost. Compared with traditional manufacturing technology, 3D printing technology has the advantages of high efficiency, fast manufacturing, moldlessness, and complexity. Ceramic products need to be processed through raw material powder processing, green body preparation and molding, solid product sintering and final There are four main links in processing, of which the one-step process of product forming takes the longest time and the most expensive. In order to enable advanced ceramic manufacturers to save raw materials, shorten product processing cycles, reduce manufacturing costs, and mass-produce products in the production process, moldless ceramic molding manufacturing technologies relying on 3D printing came into being.
Realization of ceramic material 3D printing technology depends on two systems. One is the computer software system, which is used to design the structure and graphics and convert it into a universal code language; the other is the operating system that receives instructions, which is used to output Print the final product.
The basic process is roughly as follows: ① Establish a three-dimensional CAD model (computer aided design, computer-aided design). ② Based on the principle of discrete-superposition, slice it to obtain many separated planes. ③ Transfer to the molding system. ④Use CAM (computer aided manufacturing, computer aided manufacturing) to print out the complete prototype of the parts layer by layer. In reality, not all the designed 3D models can be successfully printed. Because ceramic 3D printing molding technology is different from traditional 3D printing technology, the establishment of ceramic 3D models should be continuously optimized according to the requirements of actual samples.
Common ceramic 3D printing technology molding processes are as follows:
①Fused deposition of ceramics (FDC)
Compared with the traditional fused deposition molding, the characteristic of ceramic fused deposition molding technology is that the ceramic powder is incorporated into the organic binder, and the amorphous binder is added, and the composite material is placed in the extruder after a little It is melted at a temperature higher than its melting point, and a ceramic green body is prepared by computer control, then after degreasing, it is fired into parts under suitable high temperature conditions.
Scope of application: The ceramic material suitable for this process must have certain mechanical and thermal properties; the designed 3D model is generally a porous form with high porosity and tubular support.
Disadvantages: Because this technology needs to be heated before cooling and forming, this requires that the 3D model should not be designed to be too small, and the interior should not be too dense, because the printing layer is still at a high temperature when the current printing layer has been printed. If it is not completely cooled, printing in this state will cause a secondary melting phenomenon, which will easily lead to the deformation of the 3D printing preparation and the production failure.
② Stereolithography apparatus (SLA)
Also known as three-dimensional printing molding technology, it is the earliest developed rapid prototyping technology, and it is also one of the most in-depth research, the most mature technology, and the most widely used rapid prototyping technology. The main mechanism is to use a photosensitive liquid resin that can be cured quickly under ultraviolet light as a raw material, and selectively irradiate a layer of liquid through ultraviolet light, and finally form a partly cured part.
Advantages: The method has a fast forming speed, a high degree of automation, can form any complex shape, high dimensional accuracy, and excellent surface quality. Using this technology, nano-sized ceramic parts can be prepared, as well as complex, high-precision fine workpiece rapid prototyping .
Disadvantages: The parts are easy to bend and deform and need support. Furthermore, photosensitive resins and ultraviolet light sources are required in the molding of products, but photosensitive resins may contain toxic organic substances, which may easily cause environmental pollution during subsequent processing and treatment, and therefore need to be protected from light. The cured parts of liquid resin are brittle and easy to break.
③Selective laser sintering (SLS)
It is also called selective laser sintering process. The basic principle is similar to the three-dimensional printing technology, which is to replace the binder with a laser beam, and use the laser beam to scan the surface of the powder point by point along the path designed by the computer. Heating, causing the particles to melt themselves or produce a good bond under the action of the adhesive on both sides. The powder of the new layer is added after the laser scanning powder of the previous layer is bonded, and the three-dimensional structure of the new layer is formed again after the laser scanning. In this way, after repeating the layer-by-layer laser scanning, high-temperature melting and local bonding operations in accordance with the above process cycle, three-dimensional parts with different regional structures can be finally obtained.
Advantages: It can directly prepare plastics, metals or ceramics without the need for support. The materials are widely selected and the molding accuracy is high. Complex components can be manufactured without the need to increase the base support. The material utilization rate is high.
Disadvantages: due to the introduction of laser during the molding process, the powder needs to be preheated and cooled, so the molding cycle is longer, and the subsequent processing process is also more complicated. At the same time, because the raw material powder used needs to be able to be bonded under the action of laser and completely fired at high temperature, the product types that this technology can prepare are limited. –
④Three-dimensional printing technology (three-dimensional printing, 3DP)
This technology was originally proposed by the staff of the Massachusetts Institute of Technology based on the principle of "layer printing, layer-by-layer stacking", which is a new technology developed for the development of high-performance ceramics in recent years. The process of applying this technology to ceramic material molding is: first divide the three-dimensional structure of the designed product into multiple discrete structural units, and then under the control of computer instructions, selectively spray the binder onto the surface of the ceramic powder After the powder is bonded, the final molded three-dimensional member can be obtained.
Application: At present, 3DP technology has been applied in bioceramics and functional ceramics. For example, this technology has successfully prepared high-precision Al2O3-ZrO2 functional stepped ceramic materials and high-strength human gypsum bones.
⑤Ink jet printing (IJP)
This technology is developed based on the principle of inkjet printers and combined with the concept of 3D printing. The technological process is as follows: first, ceramic powder is mixed with various additives and organic substances to make ceramic slurry, also known as "ceramic ink", and then this slurry is gradually sprayed on the carrier according to computer instructions by an inkjet printer, thereby Form a ceramic green body with the original design shape and size. This technology has two key points: one is the quality of ceramic ink, which not only requires high powder content, but also has strict requirements for dispersion, anti-settling, viscosity, and drying rate; second, the control of the printer, the three-dimensional model of the component is transferred To print the control code, and then use the program to drive the printer action.
Advantages: The molding mechanism is relatively simple, and the cost of the print head is low. If the problem of ceramic ink is solved, the technology can be industrialized.
Disadvantages: Inkjet printing also has certain limitations. For example, because the size of the ink droplets limits the maximum height of the printed dots, it is difficult to prepare three-dimensional components with different heights in the Z axis direction at the same time. Ceramic products with internal porous structure.