As a typical representative technology in the manufacturing field of the third industrial revolution, the development of 3D printing has always attracted widespread attention from all walks of life. Metal high-performance additive manufacturing technology (metal 3D printing technology) is regarded by industry experts as a difficult and high-standard development branch in the field of 3D printing, and plays a pivotal role in industrial manufacturing. Antarctic Bear has also been paying attention to the development of metal 3D printing. Nowadays, industrial manufacturing companies around the world are vigorously researching and developing metal additive manufacturing technology, especially aerospace manufacturing companies, even spending a lot of financial and material resources to increase research and development efforts to ensure their technological leadership.
Against the background of the U.S. manufacturing return strategy and German Industry 4.0, the international environment also provides 3D printing with indispensable nutrition for its growth. Whether it is the newly established National Additive Manufacturing Center in the United States or the British Technology Strategy Committee, aerospace is the primary application area for additive manufacturing technology. In October 2012, Lu Yongxiang, former president of the Chinese Academy of Sciences and vice chairman of the National People's Congress, made it clear that China's 3D technology will also be first applied in the aerospace field.
As the bright pearl in the crown of the industry, the aerospace manufacturing field integrates all the high-tech technologies of a country, and it is the back-up guarantee field where the national strategic plan can be implemented and the political situation can be displayed. As a brand-new manufacturing technology, metal 3D technology has outstanding application advantages in the aerospace field and obvious service benefits. It is mainly reflected in the following aspects:
(1) Shorten the research and development cycle of new aerospace equipment
Aerospace technology is a symbol of national defense strength and a manifestation of national politics. The competition among countries in the world is extremely fierce. Therefore, all countries want to try to develop newer weapons and equipment at a faster speed to make themselves invincible in the field of national defense. Metal 3D printing technology greatly shortens the manufacturing process of high-performance metal parts, especially high-performance large structural parts. There is no need to develop molds used in the manufacturing process of parts, which will greatly shorten the product development and manufacturing cycle.
Li Daguang, a professor of the Department of Military Logistics and Military Science and Technology Equipment, National Defense University, said that in the 1980s and 1990s, it would take at least 10-20 years to develop a new generation of fighter jets. The most prominent advantage of 3D printing technology is that it does not require machining or any molds, parts of any shape can be directly generated from computer graphics data, so if 3D printing technology and other information technologies are used, a new fighter jet can be developed in at least three years. Coupled with the high flexibility, high performance and flexible manufacturing characteristics of the technology, as well as the free rapid prototyping of complex parts, metal 3D printing will shine in the aerospace field and provide strong technical support for the manufacture of defense equipment.
The central flange part on the domestic large aircraft C919 is a typical application of metal 3D printing technology in the aviation field. This structural part is more than 3 meters long, and it is the longest aerospace structural part produced by metal 3D printing in the world. If the traditional manufacturing method is used, this part needs to be forged by a super-large-tonnage press, which is not only time-consuming and labor-intensive, but also wastes raw materials. At present, there is no equipment in China that can produce such large-scale structural parts.
Therefore, in order to ensure the development process and safety of the aircraft, we must order this part from abroad, and the life cycle from ordering to installation is as long as more than 2 years, which seriously hinders the progress of aircraft research and development. The central flange strip printed by metal 3D printing technology took about one month to develop, and its structural strength reached or even exceeded the standard for forgings, which fully complied with aviation standards. The use of metal 3D printing technology has greatly shortened the development of my country's large aircraft, allowing the development work to proceed smoothly.
(2) Improve the utilization rate of materials, save expensive strategic materials, and reduce manufacturing costs
And this is just a microcosm of the application of metal 3D printing technology in the aerospace field.
Most of the aerospace manufacturing fields are using expensive strategic materials, such as difficult-to-process metal materials such as titanium alloys and nickel-based superalloys. The utilization rate of materials in traditional manufacturing methods is very low, generally no more than 10%, or even only 2%-5%. The huge waste of materials also means that the machining procedures are complicated and the production time period is long. If it is a technical part that is difficult to process, the processing cycle will be greatly increased, and the manufacturing cycle will be significantly extended, resulting in an increase in manufacturing costs.
Metal 3D printing technology, as a near-net-shaping technology, can be put into use with only a small amount of follow-up processing, and the utilization rate of materials has reached 60%, sometimes even reaching more than 90%. This not only reduces manufacturing costs and saves raw materials, but also conforms to the sustainable development strategy proposed by the country.
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At a symposium held by the Chinese Academy of Sciences in 2014, Professor Wang Huaming of Beihang University once said that China can now print out the glass window frame of the C919 aircraft cockpit in only 55 days. Wang Huaming also said that a European aircraft manufacturing company said that it would take at least 2 years for them to produce the same thing, and it would cost 2 million US dollars to make the mold alone. However, China's use of 3D printing technology not only shortens the production cycle, improves efficiency, but also saves raw materials, which greatly reduces production costs.
(3) Optimize the structure of parts, reduce weight, reduce stress concentration, and increase service life
For aerospace weapons and equipment, weight reduction is an eternal theme. It can not only increase the flexibility of flight equipment during flight, but also increase load capacity, save fuel and reduce flight cost. However, the traditional manufacturing method has already maximized the weight reduction of parts, and it is unrealistic to further exert the spare capacity.
However, the application of 3D technology can optimize the structure of complex parts. Under the premise of ensuring performance, the complex structure can be transformed and redesigned into a simple structure, thereby reducing weight. Moreover, by optimizing the structure of the parts, the stress of the parts can be presented in the most rational distribution, reducing the risk of fatigue cracks, thereby increasing the service life. Realize temperature control through reasonable and complex inner flow channel structure, so as to optimize the design and use of DLP materials(liqcreate wax castable and liqcreate premium model), or realize arbitrary free molding of different parts through the compounding of materials, so as to meet the use standards.
The landing gear of a fighter plane is a key part that bears high load and high impact, which requires parts with high strength and high impact resistance. The landing gear manufactured by 3D technology on the American F16 fighter plane not only meets the use standards, but also has an average life span of 2.5 times that of the original.
(4) Repair and forming of parts
In addition to the use of metal 3D printing technology in production and manufacturing, its application value in the repair of metal high-performance parts is by no means lower than its manufacturing itself. As far as the current situation is concerned, the potential of metal 3D printing technology in repair shaping is even higher than its manufacturing itself.
Take the high-performance integral turbine blisk parts as an example. When a certain blade on the disk is damaged, the entire turbine blisk will be scrapped, and the direct economic loss is worth more than one million. Compared with the past, this kind of loss may be irreparable and heartbreaking, but based on the characteristics of 3D printing layer-by-layer manufacturing, we only need to regard the damaged blade as a special substrate, and perform laser three-dimensional forming on the damaged part , the shape of the part can be restored, and the performance meets the requirements of use, even higher than that of the base material. Due to the controllability of the 3D printing process, the negative impact of its repair is very limited.
In fact, 3D printed parts are easier to repair and match better. Compared with other manufacturing technologies, in the 3D repair process, due to the gap between the manufacturing process and repair parameters, it is difficult to maintain the consistency of the repair area and the substrate in terms of tissue, composition and performance. But this problem does not exist when repairing 3D formed parts. The repair process can be regarded as a continuation of the additive manufacturing process, and the repair area and the substrate can achieve an optimal match. This realizes a virtuous circle in the part manufacturing process, low cost manufacturing + low cost repair = high economic benefit.
(5) Cooperate with traditional manufacturing technology and complement each other
Traditional manufacturing technology is suitable for the production of large-volume shaped products, while 3D printing technology is more suitable for the manufacture of personalized or refined structural products. Combining 3D printing technology and traditional manufacturing technology, each draws on its strengths, gives full play to its respective advantages, and makes manufacturing technology more powerful.
For example, for parts that require high-quality performance on the surface but average performance in the center, traditional manufacturing techniques can be used to produce central-shaped parts, and then laser stereoforming technology can be used to directly form surface parts on these central parts. In this way, parts with high surface performance and general center requirements are produced, which saves the complexity of the process and reduces the production process. This complementary combination has important practical application value in production and parts manufacturing.
Furthermore, for components with a simple external structure but a complex internal structure, when the traditional manufacturing technology is used to manufacture the internal complex structure, the process is cumbersome and the subsequent processing procedures are complicated, which results in production costs and prolongs the production cycle. The external use of traditional manufacturing technology and the internal use of 3D printing technology are directly close to net shape, so that only a small number of follow-up processes can complete the product manufacturing. This shortens the production cycle, reduces costs, and enables the perfect matching of traditional technology and new technology to achieve interoperability and complementarity.
As the primary application field of 3D printing technology, aerospace has obvious technical advantages, but this does not mean that metal 3D printing is omnipotent. In actual production, there are still many problems to be solved in its technical application. For example, at present, 3D printing cannot adapt to mass production, cannot meet high-precision requirements, and cannot achieve high-efficiency manufacturing. Moreover, a key factor restricting the development of 3D printing is the high cost of its equipment, and most civilian fields cannot afford such high equipment manufacturing costs. However, with the continuous development of material technology, computer technology and laser technology, manufacturing costs will continue to decrease to meet the manufacturing industry's ability to bear production costs. At that time, 3D printing will shine its light in the manufacturing field.
