I. Introduction
Laser Additive Manufacturing (LAM) belongs to the laser as the energy source of the additive manufacturing technology, can completely change the traditional processing mode of metal parts, mainly divided into the powder bed laying powder as the technical characteristics of the laser selective melting (SLM), synchronous powder feeding as the technical characteristics of the laser direct deposition (LDMD) [1]. Currently, the application of LAM technology in aviation, aerospace and medical fields is developing most rapidly [2~4]. This paper focuses on the development of LAM technology for metals, as the relevant fields are mainly related to the manufacture of metal structures.
As the performance and structural complexity of metal parts increase, the difficulty, cost, and cycle time of manufacturing using traditional processes such as casting and forging are rapidly increasing, and LAM technology, which is both technologically advanced and resource-economical, provides a new type of solution for the manufacturing of high-performance, complex structures: topology-optimized structures, dot-matrix structures, gradient material structures, and complex internal runner structures are no longer difficult, and structural-functional integration and lightweighting are no longer necessary. It is no longer difficult to realize topology-optimized structures, dot-matrix structures, gradient material structures, complex internal flow channel structures, etc. New types of structures such as structural-functional integration, lightweight, ultra-tough, extreme load-resistant, and ultra-heat-dissipating structures can be applied, and the corresponding structural efficiency has been greatly improved [1,4]. For example, General Electric (GE) SLM aircraft engine fuel nozzle, Beijing University of Aeronautics and Astronautics LDMD aircraft titanium alloy frame is a typical application case.
From the current development of metal LAM technology at home and abroad, the real direction of industrialization of the technology is still a minority, this is because the basic theory accumulation, key technology breakthroughs, engineering application technology maturity, technology research and development of the commercialization of the promotion of the LAM technology to varying degrees of constraints on the industrialization of LAM technology applications. At present, domestic and foreign research is mainly focused on the control of the study, focusing on porosity, cracks, tissue characteristics, anisotropy and other basic research [5~9]. There are fewer research reports on shape control, detection, product standards and other research in favor of product development, which also indicates that metal LAM is in the overall development stage of transition from technical research to industrial application.
In this paper, through literature, on-site and questionnaire surveys, we systematically sort out the development status and trend of research and application in the field of metal LAM, analyze the gaps between domestic and foreign countries, and between theoretical research and application needs, and put forward the core key technologies and bottleneck processes involved in the industrialization and application, with a view to promoting the development of the industrial application of metal LAM technology in China.
Second, metal laser additive manufacturing demand analysis
LAM is based on the number of die slicing, through the layer-by-layer stacking to achieve the metal parts of the near-net-shape manufacturing, especially suitable for complex shaped parts, gradient materials and properties of components, composite parts and difficult to process material parts manufacturing, in the direction of the aerospace industry and other advanced manufacturing is highly favored. Favorable. On the one hand, the related parts are complex and variable in shape, high material performance requirements, difficult to process and high cost; on the other hand, the new aircraft toward high performance, long life, high reliability, low cost direction, the use of complex, large-scale overall structure has become the design of the urgent need.
SLM formed parts of higher precision, but the size of the parts by the processing room limitations, so SLM is mainly used for small or medium-sized complex precision structure precision molding, the corresponding product structure of the functional attributes are generally greater than the load-bearing attributes. In order to meet the overall performance requirements, aero-engine fuel nozzles (with complex internal oil circuit, gas circuit and cavity), bearing housing, control housing, blades, aircraft hatch supports, hinges, auxiliary power module grill structure intake door, exhaust door, satellite bracket and other parts, need to carry out structural innovation design, become a suitable application of SLM technology.
LDMD shaped parts with good mechanical properties, but relatively low dimensional accuracy, mainly used for medium-sized or large-sized complex load-bearing structure of the manufacturing, the corresponding product structure of the load-bearing attributes are generally greater than the functional attributes. Aero-engine magazines, compressor/turbine blisks and other structures have complex shapes, and in order to improve performance, they even need to use heterogeneous or functionally gradient material structure. In order to balance mass reduction and load-carrying efficiency, load-carrying components such as aircraft joints, landing gears, load-bearing frames, pulley frames, and the lattice-structure load-bearing skeleton of high-speed aircraft wings/air rudders need to be optimized in terms of structural topology. The outstanding complexity and manufacturing difficulty of these structures have created a clear need for LDMD technology.
In addition, the aircraft, the engine with some local camber, ear piece and other special structure of the load-bearing components, the use of forging process will be difficult to ensure that the local configuration and performance; large aircraft, titanium alloy load-bearing frame of large specifications has exceeded the upper limit of the processing capacity of the existing forging equipment. This has created a clear need for forging + additive manufacturing / additive connection composite manufacturing technology.
Third, foreign metal laser additive manufacturing development status
(a) the current state of the technology research
1. laser selective melting technology
related enterprises using vacuum induction gas atomization (VIGA), no crucible electrode induction melting gas atomization (EIGA), plasma rotary atomization (PREP), and plasma torch (PA) to prepare SLM powders, and have the ability to supply in bulk, occupying a major market in the world [10] .
The focus of the LAM process research is mainly on the regulation of organization and performance, and more studies have been completed on the SLM organization, defects, performance and their relationship with process parameters. For example, for stainless steel parts SLM, increase laser power, reduce the scanning speed are conducive to improve the densification [11]; high surface roughness and porosity will reduce the corrosion resistance of AlSi10Mg aluminum alloy SLM, while the formation of the oxide film can improve the corrosion resistance; AW7075 aluminum alloy SLM samples produced perpendicular to the direction of the incremental crack, and preheating the aluminum powder on crack control has no improvement, the internal cracking direction. The preheated aluminum powder has no effect on crack control, and the internal cracks result in a much lower fatigue life than the conventional process [7].
The energy density has a significant effect on the SLM organization and defects of Ti-6Al-4V titanium alloys [5,12,13]: low energy density results in a lamellar α+β-phase organization, which is prone to porosity and poor fusion; high energy density results in an acicular martensitic α′-organization, which promotes the aluminum bias and the formation of the α2- Ti3Al phase; the fatigue strength of Ti-6Al-4V alloys is lower than that of forged products, while the fatigue strength of Ti-6Al-4V alloys is much lower than that of forged products. 4V alloy fatigue strength is about 80% lower than that of forgings [6]; hot isostatic pressing reduces porosity and improves properties. For CMSX486 single crystal alloy SLM, low energy density reduces cracking and high energy density reduces porosity [8]. CM247LC alloy SLM longitudinal section is mainly composed of columnar γ grains, and the bias of Hf, Ta, W, and Ti increases the precipitates and residual stresses, which results in the internal cracking of the parts [14]. Microcracking in IN738LC high temperature alloy SLM is related to the enrichment and segregation of Zr at the grain boundaries [15]. The microcracks in IN738LC high temperature alloy SLM are related to Zr enrichment and segregation at grain boundaries [15]. Moderate addition of Re can refine the dendrites of IN718 alloy, but excessive Re is detrimental to the fatigue strength [14].SLM Hastelloy-X alloy is heat treated to form equiaxial crystals, the yield strength is reduced; the tensile strength is restored to the level of the deposition state by hot isostatic pressing and the elongation can be increased by 15% [16].
For metal LAM process, foreign countries have carried out more fine research. It is understood that the German equipment vendors for a new material SLM process development, it takes 6 to 8 months, adjusting the parameters of more than 70. Through topology optimization to achieve structural lightweight design is also the focus of SLM application research, foreign counterparts put forward a design-led manufacturing, functional priority and other new concepts. The development of special support design technology, so that the separation of parts and substrates without wire cutting, effectively shortening the cycle of pickup.
In addition, metal LAM standards research and development work has been synchronized with the development of technology applications. 2002, the United States issued the "annealed Ti-6Al-4V titanium alloy laser deposition products", followed by the subsequent promulgation of 19 related standards, covering the product annealing and hot isostatic pressure system, aging system, the manufacturing process of stress relieving annealing system and so on many aspects. The timely formation of standards for the industrial application of LAM technology plays a fundamental role in supporting.
2. Laser direct deposition technology
In 1995, the United States, Johns Hopkins University, Pennsylvania State University, MTS Systems **** with the development of high-power CO2 laser-based LDMD technology for large-size titanium alloy parts, the deposition rate of 1 ~ 2 kg / h, contributing to the application of LDMD parts in the aircraft [12].
LDMD technology research mainly includes forming process and organizational properties. Sandia National Laboratories and Los Alamos National Laboratory prepared LDMD formed parts, its mechanical properties close to or even exceed the traditional forging parts. Swiss Federal Institute of Technology in Lausanne studied the single crystal blade LDMD repair process stability, part accuracy, organization, mechanical properties and process parameters of the relationship between the formation of the repair technology has been applied to engineering.
Foreign scholars for Ti-6Al-4V alloy LDMD technology has carried out in-depth research, revealing the process parameters and additive manufacturing organization, mechanical properties of the link between the elucidation of the process adjustment and hot isostatic pressure on the organization, properties of the adjusting role of the [13,17~19]. LDMD technology for the control of the microstructure of the material to provide a greater degree of freedom: by adjusting the nickel base, high temperature alloy LDMD nuclei and the structure of the part to the core, the repair technology has been applied to engineering applications. High-temperature alloy LDMD nucleation and growth conditions to obtain the expected single-crystal and polycrystalline organization [9]; the National Aeronautics and Space Administration (NASA) developed a hybrid deposition of a variety of metals in the same structure of the LDMD technology, so that the performance of the part with the different parts of the change. German companies have integrated LAM technology with traditional cutting methods to produce complex shapes that are difficult to manufacture by traditional processes, with increased precision and improved surface roughness [11].
(2) equipment development
LAM technology to promote the application of the basis of cost-effective LAM equipment. SLM equipment development in Germany, France, Britain, Japan, Belgium and other countries, LDMD equipment development countries are mainly in the United States and Germany, etc.
1.
1. Laser selective melting equipment
Germany is the SLM technology and equipment research started the earliest countries, EOS company launched the SLM equipment has a certain technical advantage, the relevant equipment is used in the GE LEAP aero-engine fuel nozzles processing and manufacturing, through the monitoring of the additive manufacturing process to further improve the quality of manufactured products; Realizer GmbH's all-round design, parts stacking and manufacturing of parts. The all-round design and part stacking technology solutions of Realizer GmbH are unique; the equipment of Concept Laser is characterized by its large build size; and the laser technology and airflow management technology of SLM Solutions is in a leading position. 3D Systems (USA) has the technological advantage of specialized powder deposition systems that allow for the shaping of precise, detailed features. Renishaw PLC in the UK is characterized by its technology in terms of material flexibility and ease of replacement.
2. Laser direct deposition equipment
The United States EFESTO company has a technological advantage in large-size metal LAM, the development of LDMD equipment studio size of up to 1500 mm 1500 mm 2100 mm, the United States Optomec introduced LDMD equipment with 900 mm 1500 mm 900 mm studio space, equipped with 5-axis moving workpiece. Optomec's LDMD equipment has a 900 mm 1500 mm 900 mm studio space, configured with a 5-axis moving table, the maximum molding speed of 1.5 kg / h. German companies to provide integrated laser processing system is also the mainstream of LDMD equipment.
In recent years, additive and subtractive composite processing equipment has become a new hot spot in the market. Japan's DMG company launched a 2 kW laser, supplemented by 5-axis linkage CNC milling machine LDMD equipment, forming speed of 20 times higher than the ordinary powder machine, can be in the manufacturing process of milling the final part of the inaccessible parts. A related machine from Japan's Mazak is capable of 5-axis mill-turn machining for polygonal forgings or castings, rotary parts, and complex shaped parts.
(3) application
Titanium alloy LAM in the field of aviation has made important applications. The United States took the lead in the LDMD titanium alloy bearing parts for shipborne fighter aircraft; Carpenter Technology Corporation to use high-strength custom stainless steel additive manufacturing, the production of advanced aerospace gears; F-22 aircraft maintenance using SLM corrosion-resistant bracket, so that the maintenance time is significantly reduced. In the UK, LDMD technology has been successfully applied to the manufacture of monolithic frames for drones.
SLM technology has been widely used in the manufacture of complex parts of aircraft engines. The United States GE company took the lead in the application of SLM technology in the production of high-pressure compressor temperature sensor housing, the product has been approved by the U.S. Federal Aviation Administration (FAA), fitted with more than 400 GE90-40B aero-engine. GE LEAP series aero-engine fuel nozzles are also used in the production of SLM technology (in 2020 to have a production capacity of 44,000 / year). The same SLM technology is used to produce fuel nozzles for GE's LEAP series of aero-engines (44,000/year by 2020). Pratt & Whitney (USA) uses SLM to produce duct mirror sleeves for the PW1100G-JM aero-engine. Rollo (UK) used SLM to manufacture the titanium front bearing assembly (consisting of 48 wing guide vanes) for the Trent XWB-97 aero-engine.
Since 2012, LAM technology has been used in the manufacture of space vehicles, with NASA using LAM to manufacture the bent joints of the RS-25 rocket engine, reducing the number of parts, welds, and machining processes by approximately 60% compared to traditional methods, and reducing the total number of parts by 80% for the Hydrogen Oxygen Rocket Engine by using a monolithic design and manufacturing approach. France Thales Group used SLM technology to manufacture the measurement and control antenna support parts (aluminum alloy) for Koreasat5A and Koreasat7 communication satellites, reducing the mass by about 22% and saving about 30%.
The popularization and application of LAM technology has accelerated the structural topology optimization and point structure design of aerospace vehicles. The aluminum alloy mounting bracket for the telemetry/remote control antenna of the Eurostar E3000 satellite platform of European Astrium Company reduces the mass by about 35% and improves the structural rigidity by about 40% by adopting LAM for the overall manufacturing. Cobra Aero Company of the United States and Renishaw PLC of the United Kingdom have cooperated to complete the LAM manufacturing of the whole part of the engine with complex dot matrix structure. In addition, additive and subtractive composite processing technology is beginning to move towards application. Virgin Orbit used additive and subtractive material hybrid machine tools to manufacture and finish rocket engine combustion chamber parts, completing 24 engine test runs in 2019.
(D) Development experience and inspiration
Looking back at the development process of metal LAM technology in the international arena, it is important experience to take industrial development to pull technology research and equipment development, and to improve market competitiveness through industry chain integration. Application enterprises are concerned about the manufacturing quality and production cost of their own products, as the main body of technology development and the biggest beneficiary, by its integration of materials, processes, equipment, verification, standards research and personnel training, can be more efficient to promote the development of LAM industry. For example, the U.S. GE LAM industry application in the world's leading position, mainly due to industry chain integration strategy, the acquisition of manufacturing quality control companies and additive manufacturing equipment companies to strengthen the integrity of the LAM industry chain; product manufacturing utilizes more than 300 industrial-grade manufacturing equipment throughout the world. Foreign companies focus on LAM product manufacturing personnel training, such as GE has an additive manufacturing training center, configured with specialized equipment, can train hundreds of engineers each year.
Fourth, the domestic development of metal laser additive manufacturing status and gap analysis
(a) the development of the status quo
1. metal LAM technology
Domestic around the LDMD organization, defects, stress and deformation control, etc. to complete the more research work. [11,13,14]. Beijing University of Aeronautics and Astronautics (BUAA) has developed key technologies for LDMD internal defects and quality control of titanium alloy large structural parts [20]. Northwestern Polytechnical University has completed the LDMD manufacturing of oversized titanium alloy rims for airplanes, and the forming accuracy and deformation control have reached a high level. Shenyang University of Aeronautics and Astronautics put forward zonal scanning molding method, effectively controlling the deformation and cracking of parts in the LDMD process. Ltd. has broken through the TC11, TA15/Ti2AlNb heterogeneous material interface quality control and integration of complex shape control problems of the leaf disk and air intake channel, the product passed the test examination.
Domestic SLM technology for the direction of focusing on the shape and size, surface roughness precision control and other research. Xi'an Jiaotong University applies LAM to the manufacturing of hollow turbine blades, aerospace propellers, automotive parts, etc. [11].
China Aerospace Development Beijing Institute of Aeronautical Materials has completed a comprehensive study of LAM technology: LDMD manufactured nickel-based bi-alloy turbine blades through the over-turning test assessment, additive repair of IL-76 aircraft landing gear to obtain a batch of applications; the development of the LAM ultrasonic scanning and evaluation system, the establishment of the detection standards and comparison test blocks, evaluation and non-destructive testing technology results applied to aircraft pulley frame, frame and other installed parts batch application. The results of evaluation and NDT technology are applied to the batch inspection of aircraft pulley racks, frames and other installed parts.
In terms of SLM powder, domestic products basically meet the requirements of the molding process. Institute of Metals, Chinese Academy of Sciences broke through the SLM with ultra-fine titanium alloy and high temperature alloy powder clean preparation technology, performance to the level of imported products. Xi'an Ouzhong Materials Technology Co., Ltd. developed titanium alloy and high-temperature alloy powder products to obtain engineering applications.
2. Metal LAM equipment
Domestic LDMD and SLM equipment R & D capability is relatively strong, and has gained a certain share of market applications. Xi'an Platinum Laser Forming Technology Co., Ltd. has independently developed a series of SLM equipment, laser high-performance repair series of equipment. Nanjing Zhongke Yuchen Laser Technology Co., Ltd. has developed core devices such as automatic zoom coaxial powder feeding nozzle, long-range powder feeder and high-efficiency inert gas circulation purification box, forming a series of metal LDMD equipment. In addition, Beijing Eagle 3D Technology Co., Ltd. has made good progress in the small-scale production of industrial-grade and small metal SLM equipment, and Shanghai Aerospace Equipment Manufacturing General Factory Co., Ltd. has made good progress in the development of standard and large-format SLM equipment and robotic LDMD equipment.
3. Metal LAM applications
LDMD is mainly used in the manufacturing of load-bearing structures. Beijing University of Aeronautics and Astronautics manufacturing the main bearing frame, the main landing gear and other components to obtain aerospace vehicles, gas turbine engines and other equipment applications. Shenyang Aircraft Design and Research Institute of Aviation Industry promotes the maturity of LDMD technology through engineering application verification, and realizes the application of 8 kinds of metal materials and 10 kinds of structural parts in aircraft. The First Aircraft Design and Research Institute of Aviation Industry has realized the application of LDMD parts for the outer main flap pulley frame and tail rudder support arm of large aircraft. Beijing Institute of Mechanical and Electrical Engineering has realized the LDMD manufacturing and application of large-size thin-walled skeleton segment structure.
SLM is mainly used in the manufacture of complex shaped parts. In the field of aviation, China Academy of Aeronautical Manufacturing Technology has realized the SLM products installed application; Chengdu Aircraft Design Institute of Aviation Industry in the aircraft used SLM auxiliary powerhouse grille structure intake / exhaust door; Helicopter Design Institute of Aviation Industry in the ventilation grille structure, rain sealing structure, intake multi-chamber structure, etc. to achieve the SLM parts installed application. In the aerospace field, the SLM products of Shanghai Aerospace Equipment Manufacturing General Factory (SAEMGF), such as storage tank intermittent bracket, space radiator, and guidance device, etc., have been installed and applied; the SLM products of Beijing Starflight Electromechanical Equipment Co. Ltd. has applied SLM to manufacture large-size thin-walled titanium alloy dot-matrix sandwich structural parts (heat-collecting window frames), which meets the strict technical requirements of deep space exploration vehicles.
In addition, Xi'an Platinum Laser Forming Technology Co., Ltd. uses SLM technology to provide more than 8,000 parts per year for the aerospace industry; and Huazhong University of Science and Technology has manufactured gradient material molds with shaped cooling channels through additive and subtractive composite machining, which has gained more industry applications.
(2) Gaps
1. Gaps in metal LAM material design and preparation technology
The domestic LAM special material design theory and methodology system is still weak, and the design of special materials is small and scattered. Domestic research on material genome technology and its use to improve the performance of specialized LAM materials is relatively weak.
In terms of powder preparation, the domestic vacuum argon atomization powder technology is relatively mature, the preparation of stainless steel, nickel-based alloy powder performance basically meet the molding process requirements. But in titanium alloys, aluminum alloys, ultra-fine powder preparation there is not a small gap, the main problem is that the powder sphericality is poor, low yield of fine powder, can not meet the SLM forming requirements, so that the practical application of the still rely on imports.
2. Metal LAM equipment design and manufacturing technology gap
China and the United States, Germany and other LAM technology powerhouse gap is mainly in the process equipment. Domestic applications of SLM equipment rely more on German imports, while large-size engineering applications of SLM equipment mainly rely on imports. Domestic enterprises in the laser, galvanometer and other core components of the lack of self-research capabilities, domestic equipment, processing size, stability, processing accuracy needs to be improved, about the powder flow, molten pool state and other process monitoring and molding of the domestic control software is not perfect.
3. Insufficient research on metal LAM process
With the continuous improvement of the performance of turbine engines, aircraft and other important equipment materials, the material processability has declined. Domestic LAM process research on aviation backbone materials is insufficient, failed to form stress deformation, crack control and other effective methods, the problem of internal organizational defects in the parts has not yet been cured, the mechanical properties of the parts uniform consistency, batch stability is not good. In addition, the LAM process for advanced aero-engine and high-speed vehicle structural materials with ultra-high temperature is even more lacking.
4. Product dimensional accuracy and surface roughness do not meet the technical requirements
LDMD aircraft structural parts are generally left with machining allowance, dimensional accuracy and surface roughness is not necessarily a key constraint. However, turbine engine parts are mostly complex structural parts with internal runners and cavities, and the dimensional accuracy of the corresponding SLM formations is about 0.1 mm, and the surface roughness Ra is about 6.3, which is still a gap with precision castings. Related products are also facing the problem of insufficient research on molding, internal surface processing and other technologies.
5. Lack of guiding standards for metal LAM
At this stage, China's LAM industry is facing a **** problem is the lack of quality control standards, so that in the design of metal LAM products, materials, processes, testing, organizational performance, dimensional accuracy and other aspects of the lack of acceptance basis. As the application of parts based on non-destructive testing, mechanical properties, metallurgical mapping and other basic data, due to the lack of collation of the product standard development difficulties, industrialization and promotion of insufficient protection.
V. Analysis of key technologies for metal laser additive manufacturing in China
1. The design and manufacture of core devices such as laser processing head
To carry out the research and development of core devices with independent intellectual property rights, focusing on the improvement of the processor, memory, industrial controllers, high-precision sensors, digital / analog converter and other basic devices. Quality performance, the development of process equipment, core devices, the design and manufacture of key components; research and development of high-beam quality lasers and beam shaping systems, high-power laser scanning mirrors, dynamic focusing mirrors and other precision optics, high-precision nozzle processing head and other core components.
2. Scanning strategy, parameter planning and online monitoring
Breakthrough in data design, data processing, process library, process analysis and intelligent planning of the process, online detection and monitoring system, forming process adaptive intelligent control and other aspects of the software technology, to build the core support software system of LAM with independent intellectual property rights.
3. LAM Material Design Optimization Based on Material Genome
Develop high-throughput technology models for specialized materials far from the equilibrium conditions, and develop multi-scale simulation algorithms suitable for high-throughput calculations. Research on the preparation technology of powder materials with controllable microregions of composition and organization, and establish a material gene database through high-throughput experiments. Through the synergy of high-throughput computing, experiments, and database, rapidly develop LAM-specific materials with excellent performance.
4. Typical structure of backbone materials LAM control and shape control
For a number of key materials and typical parts, to carry out LAM control, shape control **** key technologies, parts engineering application research. Master the factors affecting the final quality of parts manufacturing process and measures to address the formation of engineering available LAM technology system, involving raw material control, process equipment, molding process, heat treatment, machining, surface treatment, non-destructive testing and verification tests. Emphasis on the uniformity and batch stability of LAM parts to meet the needs of the actual application of engineering.
Six, conclusion
In order to catch up in metal LAM technology and its engineering applications, the development of China's LAM should follow the "technology - product - industry" objective law, consolidate the organization and control properties, and improve the quality of the product. In order to catch up with the development of metal LAM technology and its engineering applications, the development of LAM in China should follow the objective law of "technology-product-industry", consolidate the foundation of organizational performance control technology, make up for the shortcomings of the core equipment in hardware/software research and development and integration, strengthen the quality control of products, standards and validation, and steadily push forward the industrial application.
(1) Compact laser additive manufacturing research foundation, play the technical exploration of universities and research institutes and research capabilities. By the industrial sector or application units led by the product LAM process development and performance verification, in line with the principle of first easy and then difficult, from conventional metals to intermetallic compounds, niobium - silicon ultra-high-temperature alloys and other advanced materials to expand the direction.
(2) orderly promotion of engineering application research. First in the aviation, aerospace field to select representative products to carry out LAM quality control, standards and verification work, as soon as possible to achieve mass production and engineering applications; and then gradually to the structural complexity, harsh working conditions, poor processing of high-value products to expand, in the nuclear industry, weapons, automotive, electric power equipment, and other advanced manufacturing areas to promote the application.
(3) Solid research and development of quality control standards for LAM products. Accumulation of non-destructive testing of defects related to LAM, mechanical properties, metallurgical mapping, fatigue life and other basic data to determine the material, process, non-destructive testing, organization and mechanical properties, dimensional accuracy, surface roughness, and other aspects of the acceptance of the basis for the development of China's LAM product technology standards.
(4) Combined with the actual needs of industry, set up LAM-related majors in colleges and universities, vocational and technical colleges, and cultivate professional technology and skilled personnel for enterprises. Set up LAM training centers in the advantageous technology enterprises to provide special training for designers, technicians and equipment operators in many industries in China, so as to provide intellectual support for the development of LAM industry.