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Mobile WebSiteFirst, the principle and characteristics of SLM technology
The laser selective melting (SLM) technique is a technique in which a high-energy laser beam is used to scan a pre-laminated metal powder according to a predetermined scanning path to completely melt it, and then solidified by cooling. The technical principle is shown in the figure below.
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 1 Schematic diagram of laser selection melting technology
SLM technology has the following characteristics:
1 The forming material is generally a kind of metal powder, mainly including stainless steel, nickel-based superalloy, titanium alloy, cobalt-chromium alloy, high-strength aluminum alloy and precious metal.
2 The laser beam is used to form the metal parts with the fine focus spot. The formed parts have high precision, and the surface is slightly polished and sandblasted to achieve the accuracy requirements.
3 The mechanical properties of the formed parts are good, and the general tensile properties can be super-casting, reaching the level of forgings.
4 The feed rate is slow, resulting in low forming efficiency. The size of the part is limited by the paving work box and is not suitable for manufacturing large integral parts.
Second, the development status of SLM technology
SLM technology is actually a laser additive manufacturing technology developed on the basis of selected area laser sintering (SLS) technology. However, in the SLS forming process, there is a problem of low powder joint strength. In order to solve this problem, the Fraunhofer Institute of Laser Technology in Germany proposed the concept of laser melting technology based on metal powder fusion in 1995, and in 1999. In the year, the first stainless steel powder-based SLM forming equipment was developed in Germany, and researchers in many countries have conducted extensive research on SLM technology.
At present, the research on SLM technology is mainly concentrated in Germany, the United States, Japan and other countries, mainly for the manufacturing and forming processes of SLM equipment. There are many companies specializing in the production of SLM equipment in the world, such as PHENIX and 3D SYSTEM in the US; EOS, CONCEPT and SLM SOULITION in Germany; MATSUUR and SODICK in Japan, all of which produce SLM equipment with superior performance, currently EOS of Germany The maximum processing volume of the EOSM400 SLM equipment produced can reach 400mm × 400mm × 400mm.
The research on SLM equipment in China is mainly concentrated in colleges and universities. Huazhong University of Science and Technology, Northwestern Polytechnical University and South China University of Technology have done a lot of research and research on the production and research of SLM equipment, and successfully applied it. Among them, Huayu University of Science and Technology Shi Yusheng team The research and application of the size laser selection sintering equipment won the second prize of the 2011 National Technology Invention. However, there are still gaps in domestic mature commercial equipment. At present, SLM equipment used in China is mainly based on foreign products, which will be a key direction for the development of SLM technology in China in the future.
Third, the use of SLM technology
Since the successful development of SLM technology, its lightweight parts construction features have been favored by major aviation and automobile companies. The following picture shows the cooperation between the famous aviation industry supplier Liebherr Airbus and the Chemnitz University of Technology in Germany. With the production of the hydraulic valve produced by EOS, the flight test of the Airbus A380 has been passed.
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 2 Valve body made by conventional method (left) and optimized metal 3D printed valve body (right)
The new additive manufacturing valve body is made of titanium alloy and has the same performance as a conventional valve, but with a 35% reduction in weight and fewer parts. It is possible to integrate 10 functional components into a new valve body without having to use a piping system with a large number of transverse holes. Compared to traditional milling processes, industrial 3D printing has lower complexity and high material utilization, minimizing the waste of titanium. Today, it takes about a day to build a valve body, and EOS's manufacturing time can be reduced by more than 75%. Lightweight 3D printed body and future 3D printed parts will also help reduce fuel consumption and reduce carbon dioxide and nitrogen oxide emissions.
At the same time, Morris Technologies, which was acquired by GE in the United States in 2012, used Morris' SLM equipment and process technology to manufacture jet engine-specific engine components. As shown in the following figure, GE explicitly added lasers. Manufacturing technology is recognized as a key technology to drive the development of future aero engines.
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 3 Engine impeller made by SLM technology
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 4 Fuel nozzles made by GE using SLM technology
At the same time, SLM technology also has important applications in the medical field. The University of Salamanca in Spain successfully produced titanium sternum and ribs using the Arcam SLM equipment developed by the Australian Science Association. As shown, it was successfully implanted in patients with thoracic cancer. in vivo.
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 5 Titanium alloy sternum and ribs made by SLM technology
Northwestern Polytechnical University, Huazhong University of Science and Technology and South China University of Technology are the scientific research units engaged in SLM technology research in China. They use SLM technology to manufacture a large number of metal parts with complex structures, as shown in the following figure.
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 6 Complex structural parts
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 7 Honeycomb porous metal parts
Machining metal is not only the turning and milling of the tongs in the machine tool, but also...
Figure 8 Stainless steel porous complex parts
At present, the materials used in laser additive manufacturing technology have covered titanium alloys, high-temperature alloys, iron-based alloys, aluminum alloys, refractory alloys, amorphous alloys, ceramics and gradient materials, and high-performance complex components and organisms in the aerospace industry. The manufacture of porous complex structures in the manufacturing field has significant advantages.
