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Metal 3D printing transforms traditional manufacturing methods

2018-01-13

Additive manufacturing has the technical features of rapid and free forming of the mold, full digital, high flexibility, etc. It can produce nearly infinitely complex geometric structures and can be applied to the manufacture of most types of materials. The rapid development of new products, personalized manufacturing, extremely complex structural parts that are difficult to deal with with traditional technologies, and optimized design significantly enhance product functionality are important applications for additive manufacturing




The Nineteenth National Congress report pointed out that we must speed up the building of manufacturing powers, accelerate the development of advanced manufacturing, and promote the deep integration of the Internet, big data, artificial intelligence and the real economy. We should promote high-end consumption, innovation, green, low-carbon, sharing economy, and modern supply chain. In areas such as human capital services, we will cultivate new growth points and create new momentum. This shows the direction for the development of China's science and technology enterprises.




As a result of the deep integration of the Internet and manufacturing, 3D printing technology is creating new possibilities for the transformation and upgrading of traditional manufacturing industries. International data company IDC predicts that in the next five years, the global 3D printing market will expand at a compound annual growth rate of 22.3%, reaching 289 billion US dollars in 2020.




Accurate manufacturing of complex parts




The American Society for Testing and Materials' Additive Manufacturing Technical Committee defines 3D printing as "using print heads, nozzles, or other printing techniques to make objects by material deposition." In recent years, 3D printing technology has developed rapidly.




3D printing generally refers to additive manufacturing using a low-cost, simple-to-use desktop-level device, ie, a mass-produced, universal version of additive manufacturing. So, what is additive manufacturing? Zuo Quanshan, Northern Regional Manager of Xi'an Plenty Additives Technology Co., Ltd., said that manufacturing by digitally adding materials is additive manufacturing. Correspondingly, the traditional mechanical processing method is "reducing material manufacturing" and the forging or casting method is "iso-material manufacturing."




“Additive manufacturing has the technical features of rapid and free forming of molds, full digitization, and high flexibility. It can produce nearly infinitely complex geometries and can be applied to the manufacture of most types of materials.” Zuo Quanshan said that the new products are fast. The extremely complicated structural parts that are difficult to cope with in the development, individualized manufacturing, and traditional technologies, and the optimized design significantly improve the product's functions are important application directions for additive manufacturing.




Although additive manufacturing technology has broad application prospects, it is still believed that 3D printing has a fatal disadvantage because of the presence of voids in the structure of the printed material. In this regard, Guo Chao, deputy director of the Additive Manufacturing Technology Research Institute of Tsinghua University Tianjin High-end Equipment Research Institute, explained the technology and the application level. Guo Chao said, "This phenomenon does exist, but not all materials will appear this phenomenon. Through the X-ray tomography detection, we found that the electron beam 3D printing density reached 99.96%, has been very high , close to full density."




Guo Chao said that electron beam 3D printing is actually a way of metal 3D printing. Guo Chao said that 3D printing is a revolutionary production method, and metal 3D printing is an important type of this "transformative production method."




"Metal 3D printing can be divided into two types: clad type and powder bed type." Guo Chao said, "The former has a high production efficiency and is usually suitable for printing large parts, but its accuracy is not high enough to be seen. There is a very obvious delamination phenomenon; the latter's greatest feature is accuracy, which can be used for the production of small and medium-sized parts and complex shapes.” From the point of view of the energy source, powder bed printing can be divided into laser and electron beam. "At present, the length of laser-printed parts is about one meter."




Get higher mechanical properties




With the gradual application of metal 3D printing technology to the industry, some corresponding mechanical performance problems have also triggered the thinking of academics and industry insiders. During the technical conception period, are common questions such as metal additive manufacturing techniques capable of achieving extremely high mechanical properties? Prototyping experts even asserted that the existing rapid prototyping technology won't have high performance parts and can only be used for prototyping. During the period of technological development, people will ask, how can casting materials achieve forging performance?




In fact, with the advancement of the application of metal 3D printing technology, the answers to these questions have gradually become clear. Zuo Quanshan said that the mechanical properties of metal additive manufacturing products mainly include three aspects: the composition is uniform, there is no macro-segregation from the powder forming to the solidification of the small molten pool; the material is dense, the solid/liquid interface is smooth, and sufficient feeding can be achieved. Small organization can achieve rapid solidification. From this we can see that "the principle of additive forming does not rule out the possibility of achieving very high mechanical properties, as long as the material properties of the forming point are high, and the point-to-point, track-to-track, and layer-to-layer bonding are good, adding metal to the material. Manufacturing technology can achieve extremely high mechanical properties."




Regarding the advantages and disadvantages of the properties of as-cast materials and forgings, Zuo Quanshan said, “Why is the performance of forgings better than that of castings in general? From a material point of view, the main causes of low casting performance are shrinkage, coarse structure, and impurities. Focus on the distribution and other factors, and the metal 3D printed laser three-dimensional forming parts have obvious characteristics of uniform composition, dense material, fine structure, uniform distribution of impurities, and make up the defects of the as-cast material.”




In addition, quality experts expressed concern about the performance of metal 3D printing components during the engineering application period, and pointed out how point-by-point manufacturing maintains overall performance consistency. Are the forming conditions for castings and forgings really the same? In this regard, Zuo Quanshan said that since the point-by-point forming of metal additive manufacturing provides conditions for point-by-point control, it is more likely to achieve a high degree of consistency in the molding conditions of the entire part. "Of course, the prerequisite for this high degree of consistency is a comprehensive and profound scientific understanding of the forming process of the components and the high control precision of the equipment." Zuo Quanshan added, "The prospect of obtaining higher mechanical properties is actually the development of additive manufacturing. Special alloy system."




The mechanical problem of 3D printing is also an important issue encountered by Guo Chao in the research process. "People who know about 3D printing, especially metal 3D printing, know that a particularly important consideration for 3D printing is to reduce stress and avoid distortion in the printing process." Guo Chao said, "The greater the temperature difference, the greater the stress. The current metal electron beam technology has a higher energy density and a powder bed temperature, and can be integrated with manufacturing and heat treatment, and is not particularly easily deformed or cracked in the printing process, and does not require the subsequent heat treatment of the metal material in the conventional manufacturing method. Process."




Solve traditional craft problems




At present, metal 3D printing technology is mainly used in aerospace, medical implants and other fields. Guo Chao said that in the aerospace field, laser 3D printing has many applications. "Because it can produce some lightweight, complex structures, and a "killer" application of electron beam, it is also a very classic application in the industry. It is the low-pressure turbine blade of the aero-engine.” The manufacturing cost of aviation titanium-aluminum alloy blades is close to that of precision casting, and the weight is 30% lighter. “It is foreseeable that in the next decade, the traditional process of the foundry industry will be replaced by 3D printing is unstoppable. The trend."




Zuo Quanshan introduced that the application of metal additive manufacturing technology in the aerospace field is embodied in four aspects: high-performance repair, extremely complex structural parts manufacturing, functional enhancement, and weight reduction. Taking AeroMet, Inc. as an example, the company used laser three-dimensional forming technology in metal additive manufacturing to shorten the inspection cycle of wing beams in F15 fighter jets to one week, and the replacement cycle of corrosion damage parts for F15 aircraft was significantly shortened. The Swiss Federal Institute of Technology in Lausanne, Switzerland uses laser stereolithography to repair single-crystal turbine blades. The laser repair time for damaged blades in single-crystal turbine blade repair is only 1 to 3 minutes per piece.




In recent years, medical implants have rapidly developed along the path from standardization to personalization. Guo Chao said, "At present, domestic and foreign markets are generally used implants are standardized, the next trend is to personalize, that is, each bone implant not only differ in size, shape and appearance are also different. Through tight integration with CT scanning technology, 3D electron beam printing can be customized to the bones of the patient. “The scanned results are quickly digitized to form the necessary restorations. Drawings can be sent directly to make solid components. Within 72 hours, the implant can reach doctors and perform surgery for patients.”




"The 3D-printed skeletal component has a very distinct feature: its surface is a special secondary grid structure, a bionic structure that mimics the human skeleton. After this structure is implanted in the human body, the bone can grow directly into the electrons. The beam printed components form a very good biological fixation. This is why the electron beam 3D printing is currently very popular in the medical industry." Guo Chao believes that "in just five to six years, 3D printing will be used in orthopedics applications." Rapidly cover the entire healthcare industry."




In the future, Guo Chao hopes that metal 3D printing technology will pay more attention to the autonomy of core components, including electron guns, matching power supplies, focusing scanning coils, and height coil driving. “3D printing is a systematic project and is a complete solution. It should focus on the autonomy of the core material process, from the powder material to the process parameter package to the roughness, density, chemical composition, and strength, fatigue, etc. 'Materials - parameters - performance' database. "In addition, Guo Chao said, "I hope '3D printing +' pay more attention to the direction of civilian use, which is an important trend in the future development of 3D printing."





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