3D printing technology is bringing infinite new possibilities to the transformation and upgrading of traditional manufacturing industries. In the next five years, the global 3D printing market will expand at a compound annual growth rate of 22.3%, reaching $28.9 billion in 2020.

Metal 3d printing
Metal 3d printing

Accurately manufacture complex parts

3D printing generally refers to additive manufacturing using low-cost, simple-function desktop-level equipment, that is, a mass-oriented, popular version of additive manufacturing. So, what is additive manufacturing? Manufacturing by adding materials digitally is known as additive manufacturing. Correspondingly, the traditional machining method is “subtractive manufacturing”, and the forging or casting method is “equivalent manufacturing”.

“Additive manufacturing has the technical characteristics of mold-free rapid free forming, full digitalization, and high flexibility. It can manufacture nearly infinitely complex geometric structures and can be applied to the manufacture of most types of materials.” Rapid development of new products and personalized manufacturing, Extremely complex structural parts that are difficult to deal with by traditional technologies, and optimized design to significantly improve product functions are important application directions of additive manufacturing.

Although additive manufacturing technology has broad application prospects, there are still people who believe that 3D printing has a fatal disadvantage because of the pores in the structure of the printed object. In this regard, “this phenomenon does exist, but not all materials will have this phenomenon. We found that the density of electron beam 3D printing has reached 99.96%, which is very high and close to full density.”

“Metal 3D printing can be divided into two types: cladding and powder bed.” The former has high production efficiency and is usually suitable for printing large parts, but its accuracy is not high enough, and very obvious delamination can be seen Phenomenon; the biggest feature of the latter is precision, which can be used for the production of small and medium parts and parts with complex shapes. “From the perspective of energy source, powder bed printing can be divided into laser and electron beam. “Currently, the length of parts printed by laser is about one meter. “

Get higher mechanical properties

With the gradual application of metal 3D printing technology to the industry, some corresponding mechanical properties have also aroused the thinking of academics and industry insiders. During the technical conception period, common questions such as whether metal additive manufacturing technology can achieve extremely high mechanical properties? The parts obtained by the existing rapid prototyping technology have low performance and can only be used for prototype manufacturing.

In fact, with the in-depth advancement of the application and transformation of metal 3D printing technology, the answers to these questions have gradually become clear. The mechanical properties of metal additive manufacturing products are mainly manifested in three aspects: uniform composition, basically no macrosegregation from powder forming to small molten pool solidification; dense material, smooth solid/liquid interface, which can achieve sufficient feeding; fine structure, which can achieve rapid solidification. From this, it can be seen that “the principle of additive forming does not rule out the possibility of achieving extremely 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 are well combined, metal additive The manufacturing technology can achieve extremely high mechanical properties.”

In view of the pros and cons of as-cast materials and forging properties, “Why is the performance of forgings generally better than that of castings? From the perspective of materials, the main reasons for the low performance of castings are shrinkage porosity, coarse structure, and concentrated distribution of impurities. However, the metal 3D printed laser three-dimensional forming parts have obvious characteristics of uniform composition, dense material, fine structure, and uniform distribution of impurities, which makes up for the defects of as-cast materials.”

In addition, expressed concern about the performance of metal 3D printed components in the engineering application period, and pointed out how to maintain the consistency of overall performance in point-by-point manufacturing. Are the forming conditions of castings and forgings really the same everywhere? In this regard, since the point-by-point forming of metal additive manufacturing provides the conditions for point-by-point control, it is more likely to achieve a high degree of consistency in the forming conditions of the entire part. “Of course, the premise of this high degree of consistency is a comprehensive and profound scientific understanding of the forming process of the components and the high control accuracy of the equipment. “The prospect of obtaining higher mechanical properties is actually the development of special alloy systems for additive manufacturing. “

The mechanical problem of 3D printing is also an important problem encountered in the research process. “Those who understand 3D printing, especially metal 3D printing, know that a particularly important consideration in 3D printing is to reduce stress and avoid deformation during printing.” “The greater the temperature difference, the greater the stress. The current metal electronics Beam technology has higher energy density and powder bed temperature, which can realize the integration of manufacturing and heat treatment, and it is not easy to deform or crack during the printing process, and does not require the subsequent heat treatment of metal materials in traditional manufacturing methods.”

Solve traditional craft problems

At present, metal 3D printing technology is mainly used in aerospace, medical implants, and other fields. In the aerospace field, laser 3D printing has many applications, “because it can manufacture some lightweight and complex structures, and a ‘killer’ application of electron beams is also a very classic application in the industry at present, that is, aero-engines The manufacturing cost of aviation titanium-aluminum alloy blades is close to that of precision casting, and the weight is 30% lighter.

The application of metal additive manufacturing technology in the aerospace field is reflected in four aspects: high-performance repair, extremely complex structural parts manufacturing, functional enhancement, and weight reduction. The use of the laser three-dimensional forming technology in metal additive manufacturing shortens the maintenance cycle of the wing spar in the F15 fighter jet to 1 week, and the replacement cycle of the corrosion-damaged parts of the F15 aircraft is greatly shortened. Using the laser three-dimensional forming technology to repair the single crystal turbine blade, the laser repair time of the damaged blade in the repair of the single crystal turbine blade is only 1~3 minutes/piece.

In recent years, medical implants have developed rapidly along a trajectory from standardization to personalization. “At present, standardized implants are still commonly used in the domestic and foreign markets. The next trend is personalization, that is, each bone implant is not only different in size, but also in shape and appearance.” Scanning technology is tightly integrated, and 3D electron beam printing can tailor bones to the specific conditions of the patient. “The scanned results can quickly form the required restoration through digital methods. After sending the drawings, the solid components can be made directly. Within 72 hours, the implant can reach the doctor’s hand and perform surgery on the patient.”

“A very obvious feature of the 3D printed skeletal components is the special secondary grid-like structure on the surface, which is a bionic structure that simulates the bones of the human body. After this structure is implanted into the human body, the bones can grow directly to the electrons. In the beam-printed components, a very good biological fixation is formed. This is why the application of electron beam 3D printing in the medical industry is very popular.” Guo Chao believes, “In just five to six years, the application of 3D printing in orthopedics will be greatly improved. Quickly cover the entire medical 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, supporting power supplies, focusing scanning coils, and height coil drives. “3D printing is a systematic project and a complete set of solutions. It is necessary to focus on the autonomy of core material processes, from powder materials to process parameter packages to roughness, density, chemical composition, strength, fatigue, and other properties. ‘Material-parameter-performance’ database.” In addition, Guo Chao said, “I hope that ‘3D printing +’ will focus on the direction of more civilian use, which is also an important trend in the future development of 3D printing.”

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