3D printing technology and material production equipment
3D printing technology originated in the 1990s, because of its special layer-by-layer deposition forming principle, can quickly and integrated forming of complex structural parts, is regarded as a transformative technology in the field of manufacturing. 3D printing is known academically as Rapid Prototyping Manufacturing (RPM). The technical division of the Manufacturing process is called Additive Manufacturing (AM).
Principle of 3D printing
3D printing is a kind of rapid prototyping technology, it is a digital model file based on the use of powder metal or plastic and other adhesive materials, through the way of layer by layer printing to construct the object technology, its basic principle is the discrete-accumulation principle. The path, limitation and way of accumulation are obtained discretely, and the material is "superimposed" to form a three-dimensional entity through accumulation. Firstly, the 3D model is obtained in the CAD software system or the surface data of the part entity is measured by the measuring instrument and converted into the 3D model. Secondly, the CAD model is processed, and the CAD model is discretized along a certain direction (usually Z-direction), and the plane slices are stratified. Then the discrete stratification information is combined with the forming process parameter information to convert the numerical control code of the forming machine, and a 3D solid part is formed by the special CAM system to control the material regularly and accurately.
Metal 3D printing powder preparation
Due to the demanding requirements of metal 3D printing technology for metal powder materials, it is necessary to meet the conditions of good sphericity, narrow particle size distribution, low oxygen content, and high purity, so the production equipment of powder materials is also put forward higher requirements. There are mainly three kinds of metal 3D printing powder preparation technology: real air atomization powder equipment, plasma atomization powder equipment and radio frequency plasma nodulization equipment.
Among them, Hunan Tianji True Air atomizing powder production equipment adopts the core technology of efficient [tightly coupled supersonic gas atomizer], which improves the powder qualification rate, reduces air consumption, and reduces production costs. At the same time, it is equipped with an online oxygen content detection system to reduce oxygen increment, which is a sharp tool for 3D printing spherical powder production.
3D printing, also known as additive manufacturing, is an umbrella term that covers several distinct 3D printing processes. These technologies are worlds apart, but the key processes are the same. For example, all 3D printing starts with a digital model because the technology is digital in nature. A part or product is originally designed using computer aided design (CAD) software or an electronic file obtained from a digital part library. The design file is then broken down into slices or layers for 3D printing by special build preparation software, generating path instructions for the 3D printer to follow. Next you'll learn the differences between these technologies and the typical uses of each.
The types of additive manufacturing can be divided according to the products they produce or the types of materials they use, with the International Organization for Standards (ISO) classifying them into seven general types (but these seven 3D printing categories also struggle to cover the growing number of technology subtypes and hybrid technologies).
● Material extrusion
● Reduction polymerization
● Powder bed fusion
● Material injection
● Adhesive spray
● Directed energy deposition
● Sheet lamination
3D printing classification
Stereolithography (SLA), also known as stereolithography, is based on the principle of photopolymerization of liquid photosensitive resins, that is, the liquid material rapidly photopolymerizes under the irradiation of ultraviolet light of a specific wavelength and intensity, and the material transforms from liquid to solid. The liquid tank is filled with liquid photosensitive resin, and the laser beam can be scanned on the liquid surface under the action of the deflection mirror, and the liquid is cured where the light spot is scanned. When a layer of scanning is completed, the unilluminated area is still liquid resin. The lifting platform drives the platform down, and the formed layer is covered with a layer of resin, and the scraper flattens the liquid surface of the resin with large viscosity, and then scans the next layer. The newly cured layer is firmly stuck to the previous layer, and so on until the whole part is manufactured, and a three-dimensional solid model is obtained.
Layered solid manufacturing technology (LOM) is to form parts by laser cutting and bonding thin materials (such as paper coated on the back side), also known as laminated solid manufacturing. The process is to first glue the paper coated with hot melt glue through the heating roller pressure bonded together, at this time located above the laser according to the data obtained by the stratified CAD model, cut a layer of paper into the internal and external outline of the part, and then a new layer of paper is superimposed on the top, bonded together by the hot pressing device, the laser is cut again. This method is characterized by high forming rate and low cost.
Selective laser sintering (SLS) selectively heats fusible or non-metallic powders (such as paraffin, plastic, resin sand, nylon, etc.) layer by layer through a laser beam to reach the sintering temperature and sinter into shape. When the first layer of sintering is completed, the workbench lowers the height of the next layer, spreads the powder of the next layer, and then scans the second layer, the newly sintered layer is firmly bonded to the previous layer, and so on, and finally sintered three-dimensional entity corresponding to the CAD model.
The basic principle of FDM is to control the heating nozzle to move in XY plane and Z direction according to the information of cross-section profile. The wire material (such as plastic wire, paraffin wire, etc.) is sent to the nozzle by the wire supply mechanism, heated and melted in the nozzle, and then selectively coated on the work table, quickly cooled to form a layer of cross-section outline, layer upon layer superposition and finally become a rapid prototype. The principle of the molding process can be used to make wax molds for precision casting and female molds for casting. It is an effective way to develop micromechanical manufacturing.
Opportunities and challenges
At present, the 3D printing industry focuses on aerospace, automotive, medical equipment and other fields, and the scale is constantly expanding and the technical level is constantly improving. Relevant policy support, including a large amount of research and development investment, innovation grants and preferential policies, has promoted the development of the industry. At the same time, the 3D printing industry is experiencing many challenges, such as material, mechanical limitations, and costs. The additive manufacturing industry is at the intersection of innovation and economic transformation, and the future is full of challenges and opportunities.