What Is a 3D Rapid Prototype?

3D rapid prototyping technology is one of many rapid prototyping technologies. Rapid prototyping technology can be roughly divided into 7 categories, including three-dimensional printing, laminated solid manufacturing, selective laser sintering, fused deposition molding, three-dimensional welding, three-dimensional printing, and digital cumulative molding. Wait.

3D rapid prototyping

Right!

3D rapid prototyping technology is one of many rapid prototyping technologies. Rapid prototyping technology can be roughly divided into 7 categories, including three-dimensional printing, laminated solid manufacturing, selective laser sintering, fused deposition molding, three-dimensional welding, three-dimensional printing, and digital cumulative molding. Wait.

Chinese name

3D rapid prototyping

Classification

7 categories

"3D rapid prototyping technology" is not the same as 3D printing!

It is just one of many rapid prototyping technologies. Rapid prototyping technology can be roughly divided into 7 categories, including three-dimensional printing, laminated solid manufacturing, selective laser sintering, fused deposition molding, three-dimensional welding, three-dimensional printing, digital accumulation molding and so on.

AVIC's laser technology team has begun to invest in "3D laser rapid prototyping technology as early as around 2000 ^[1]

(1) A new research direction of "laser cladding multi-phase and multi-phase transition metal silicide high-temperature wear-resistant and corrosion-resistant multi-functional coatings" has been developed. Cr3Si / Cr2Ni3Si and other abrasion-resistant properties have been studied, and they also have "abnormal wear-load characteristics", There are more than 10 new systems of transition metal silicide multifunctional coating materials with properties such as "abnormal wear-temperature characteristics" and "non-stick metal characteristics". A series of research papers have been "special reports" in the international journal "Advanced Coatings & Surface Technology"

(2) Based on an in-depth study of the high-speed and supernormal tribological behavior of key frictional auxiliary components of high-thrust aeroengines at high temperature and high speed, a laser cladding ultra-high-carbon Cr-Ni- "C high-temperature self-lubricating special wear-resistant coating new material" was successfully applied to the high-temperature wear-resistant moving auxiliary parts of a key hot end of a new type of aero engine in China, and won the second prize of the "National Defense Science and Technology Award";

(3) Based on in-depth experimental and theoretical research on the preferred growth characteristics of non-contact laser melting metallurgical crystals of titanium alloys, the invention of "directionally grown columnar titanium alloy laser zone constrained smelting metallurgical material preparation and laser direct forming of complex parts such as engine blades, etc." Technology ", the high temperature endurance life of titanium alloy is increased by more than 10 times;

(4) Breakthrough in the key technologies of laser rapid prototyping and key process equipment for high-performance metal structures such as aircraft titanium alloys. The key structural components of the laser rapid prototyping BT20 titanium alloy fuselage have passed all ground evaluations of the components before the test flight and have passed the installation review. Actual installed application; organically integrates three advanced superalloy preparation technologies such as "ultra-alloy ultra-refining", "directional solidification", and "rapid solidification" with "laser rapid forming technology", and proposes "ultra-pure radial fine columnar crystals" The new idea of gradient structure high-performance superalloy turbine disk and its new technology of laser direct forming of near-net-shape parts have successfully produced ultra-pure radial fine columnar gradient structure high-performance superalloy turbine disks with a diameter of 450mm;

(5) Invented the "water-cooled copper mold laser melting furnace" and a new process of refractory, difficult-to-process, highly active metal material laser melting casting material preparation and direct forming of parts ", and successfully achieved refractory alloys such as W and refractory materials such as W / W5Si3 Laser-melting and metallurgical preparation and forming of metal-reinforced ultra-high temperature "in-situ" composites and their parts has found a new way for the preparation of refractory and difficult-to-machine high-performance alloy materials and the forming and manufacturing of complex parts;

(6) It was found that the smooth liquid-solid interface and step growth mechanism of the "high Jackson factor facet crystals" are highly insensitive to the cooling rate of the solidification and the subcooling of the interface. The increase in speed or interface supercooling, the facet crystal liquid / solid interface structure will change from smooth at the atomic scale to rough at the atomic scale, and the growth mechanism will change from lateral growth to continuous growth. A reasonable supplement.

Research Progress of Laser Rapid Prototyping Technology for Large Titanium Alloy Structures

Foreword

Titanium alloy has outstanding characteristics such as low density, high specific strength, high yield ratio, good corrosion resistance and high temperature mechanical properties. It is increasingly used in aviation, aerospace, petrochemical, shipbuilding and other industrial equipment, and is mainly used widely Large-scale key main load-bearing structural components of various aircraft reinforced frames, beams, joints and other aircraft. Taking aviation applications as an example, the titanium alloy used in the new-generation civil airliners (B-787, A-380) developed by Boeing and Airbus has been reduced % Increased to more than 9%. The amount of titanium alloy structural parts in the third-generation fighter increased from about 3% of F-16 to more than 15% of F / A18-ElF and Su-27. The fourth-generation fighter F-22 The amount of titanium alloy structural parts has accounted for 41% of the total weight of the fuselage structure. In fact, the amount of large overall titanium alloy structural parts has become one of the important indicators to measure the technological advancement of defense equipment such as aircraft. However, due to the nature of titanium alloys, the use of traditional technologies such as "forging + machining" to manufacture these large and complex titanium alloy key structural parts requires not only large-scale titanium alloy ingot melting and billeting, but also heavy hydraulic forging industries of 10,000 tons and above. Equipment, and many manufacturing processes and complex processes, requiring large-scale titanium alloy ingot vacuum melting, large-scale forging billet preparation, large-scale forging mold processing, etc., large spare parts machining, low material utilization (generally less than 5-10% ), The long CNC machining time, high manufacturing cost, and long production cycle severely restrict the wide application of large titanium alloy structural parts in advanced industry and national defense equipment. The low-cost, short-cycle forming manufacturing technology of large titanium alloy main bearing structural parts It is also one of the technological "bottlenecks" that restrict the development and production of China's aviation equipment!

Laser melting deposition "near-net-shape" manufacturing technology for high-performance metal structures, using the basic principles of rapid prototype manufacturing (RPM), using metal powder (or wire) as the raw material, and Melting and stacking layer by layer, the near-net-shape manufacturincl manufacturing of fully dense, high-performance, large and complex metal parts is directly completed in one step from the CAD model of the part, which is a digitization with "transformative" significance , Short-cycle, low-cost, advanced "near-net-shape" manufacturing new technology has broad application prospects in the development and production of defense equipment such as aviation and aerospace, and is in line with traditional manufacturing technologies (forging + mechanical processing, forging + welding, etc.) Ratio, has the following outstanding advantages:

(1) Integration of high-performance material preparation and "near-net-shape" manufacturing of complex parts, without the need for part blank preparation and forging die processing, and large-scale or super-large scale forging and casting industrial equipment and related supporting facilities

(2) The part has a unique rapid solidification structure with fine grains, uniform composition and dense structure, and has excellent comprehensive mechanical properties;

(3) The material utilization rate of parts is high (more than 5 times higher than that of forgings), the machining volume is small, and the CNC machining time is short;

(4) Low manufacturing cost and short production cycle;

(5) The process and equipment are simple, the procedures are few and short, with high flexibility and "supernormal" rapid response capabilities:

(6) Material preparation and direct "near-net-shape" of various refractory materials such as W, Mo, Nb, Ta and other highly active and high-performance metal material parts can be easily realized;

(7) According to the working conditions and performance requirements of the parts, the direct near-net-shape manufacturing of multi-material gradient composite high-performance metals can be realized by flexibly changing the chemical composition of local laser melting deposition materials;

(8) It has high flexibility and quick response ability to component design and batch changes.

The unique advantages of laser rapid prototyping technology provide a new way to overcome the shortcomings of the above-mentioned manufacturing technology of large titanium alloy structural parts. Because of the importance and wide practicality of laser rapid prototyping technology of titanium alloy structural parts for the development and production of advanced defense equipment, The United States and other western industrial and military powers attach great importance to it. The Department of Defense Advanced Planning Agency (DARPA) and the Office of the Navy (ONR) and other departments have implemented a series of special research programs since 1995 to rapidly laser-engineer titanium alloy structural parts. Technology has given priority support, and research and application have progressed rapidly.

Research Progress of Laser Rapid Prototyping Technology for Aircraft Titanium Alloy Structural Parts

So far, only the American AeroMet company abroad (MTS Company invested in 1998 with Penn State University and Johns Hopkins University to establish a high-tech company specializing in laser rapid prototyping of titanium alloy structural parts for aircraft. It has gone bankrupt in February), and realized the application of laser rapid prototyping titanium alloy structural parts in aircraft between 2002 and 2005. AeroMet is working closely with military aircraft manufacturers such as Boeinq, Lockheed-Martin and other military aircraft under the funding of the US Department of Defense's "Military and Civilian Technology Program", the US Air Force "Forging Program", and the US Army "Mante" Program. Research on laser rapid prototyping technology of titanium alloy complex structural parts of aircraft fuselage. In September 2000, the ground performance evaluation test of laser-formed titanium alloy full-scale aircraft wing structural parts was successfully completed. The fatigue strength and static strength of components have replaced traditional forging and Requirements for casting aircraft titanium alloy components.

Since 2001, AeroMet has started to produce small batches of F / A-18E / F shipborne joint fighter / attack aircraft for Boeing. It supplies engine cabin thrust beams (Figure 1), wing turning folding joints, wing beams, ribbed wall panels. (Figure 2) and keel beam wall panels (Figure 3) and other wing titanium alloy non-main load-bearing structural members. In 2002, the technical standards for laser rapid prototyping Ti6A14V products were formulated. The company has begun in 2002 and declared bankruptcy in December 2005. Laser rapid prototyping Ti6A14V and other aircraft titanium alloy components have been manufactured in F-22, F / A18- ElF and other aircraft installed applications.

The American AeroMet company is the first unit in the world history to master the laser rapid prototyping technology of aircraft titanium alloy structural parts and successfully realize the installation application, but it is regrettable. Due to the inherent shortcomings of its laser rapid prototyping process, the laser rapid prototyping of titanium alloy components, such as Ti6A14V, even after subsequent hot isostatic pressing (HIP) or open die forging (Open Die Forging) processing, the fatigue performance of part materials is always significantly lower At the level of forgings (as shown in Figure 4), the laser rapid prototyping titanium alloy components cannot be applied to the aircraft's key main load-bearing structural components, which limits the application scope of laser rapid prototyping titanium alloy structural components in aircraft and eventually leads to Ae roMet announced bankruptcy in December 2005.

Domestic Research Progress of Laser Rapid Prototyping Technology for Aircraft Titanium Alloy Structural Parts

To date, only a few units, such as Beijing General Research Institute of Nonferrous Metals, Northwestern Polytechnical University, and Beijing University of Aeronautics and Astronautics, have carried out research on laser rapid prototyping technology for titanium alloys in China, but with the exception of Beihang, they have not yet been installed on aircraft.

Beijing University of Aeronautics and Astronautics' Laser Material Forming and Preparation Laboratory, under the key support of the National Natural Science Foundation of China's "Key" Project and the "Outstanding Youth Fund" Project, the National "973 Project" Special Topic, and the National "863 Project" Key Projects, etc. Combining closely with the production, academic research and other units of Shenyang Aircraft Design and Research Institute, Bai has been committed to the research of laser rapid prototyping technology, complete sets of process equipment and key technologies for engineering applications since 1998.

During the "Tenth Five-Year Plan" period, the company independently developed the first domestically-made "free plane contact / dynamic sealing / inert atmosphere protection" titanium alloy structural part laser rapid prototyping process equipment system with independent intellectual property rights. It breaks through the laser melting deposition manufacturing process and key technology of installed application of aircraft titanium alloy sub-bearing structural parts. Laser melting deposition manufactures TC4, TAl5, BT22, TC2 and other titanium alloys. Room temperature and high temperature tensile, high temperature lasting, high temperature creep, smooth fatigue. The mechanical properties such as Fatigue and El fatigue are significantly better than those of forgings. In 2005, laser rapid prototyping of various titanium alloy structures such as TAl5 and TC4 has been implemented in aircraft installations. The utilization rate of parts materials has increased by 5 times and the manufacturing cycle has been shortened. 2/3. Manufacturing costs have been reduced by more than 1/2.

During the "Eleventh Five-Year Plan" period, breakthroughs have been made in a series of core key technologies such as laser melting deposition manufacturing processes, complete sets of equipment, process control, long-term process stability, and component quality assurance for large main bearing titanium alloy structural components:

1. Developed a new laser rapid prototyping process for large integral titanium alloy main load-bearing structural parts, which solved the "technical problem" of laser rapid prototyping of large integral titanium alloy main load-bearing structural parts' deformation and cracking.

2. A new method for active control of the solidified microstructure and heat treatment microstructure of a large-scale integral titanium alloy main bearing component of a laser rapid prototyping aircraft is proposed and mastered.

3. Recognize the internal defect formation mechanism of laser rapid prototyping titanium alloy large-scale main load-bearing structural members and break through the key technologies of internal defects and quality control.

4.Breakthrough the key technology of the organization and internal quality control of the large-scale main bearing component of laser rapid prototyping titanium alloy. The comprehensive mechanical properties of the large-scale bearing component of laser rapid prototyping titanium alloy reach and exceed the titanium alloy die forgings. Among them, the gap The fatigue limit exceeds 40% of the titanium alloy die forgings, and the high temperature endurance life is more than 400% higher than that of the die forgings.

5. Successful laser rapid prototyping has produced a variety of key structural components of titanium alloy with a single weight of more than 110kq (partial physical photos are shown in Figure 5) and the main bearing structure of large-scale integrated titanium alloy aircraft with the largest size in China so far.

China's titanium alloy 3D printing comes later

China s titanium alloy laser forming technology started late, and it was not until 3 years that the United States declassified its research and development plan that it began investing in research. In the early days, it basically followed the study of the United States and set up laboratories in many universities and research institutes across the country to conduct research. Among them, the AVIC laser technology team has achieved the most remarkable achievements.

As early as around 2000, the AVIC laser technology team has begun to invest in the research and development of "3D laser welding rapid prototyping technology". With the continuous support of the state, especially military funds, after several years of research and development, the "inert gas protection system", "Dispersion of thermal stress", "defect control", "lattice growth control" and many other world technical problems, producing products with complex structure, size up to 4m, and performance meeting the requirements of the main bearing structure, have commercial application value . China's large-scale load-bearing parts manufactured by China's titanium alloy 3D printers already have the technology and capabilities to use laser to form complex titanium alloy components of more than 12 square meters, and have invested in the prototype and product manufacturing of a number of domestic aviation research projects. Become the only country in the world that has mastered the manufacture and installation of large-scale main bearing components of laser-formed titanium alloys.

90% material and cost savings

After solving the problems of material deformation and defect control, the titanium alloy structural parts produced in China quickly became a unique advantage of China Aviation Research and Development. Because of its light weight and high strength, titanium alloy components have a wide range of applications in the aviation field. The proportion of titanium alloy components on advanced fighter aircraft has exceeded 20%.

Traditional titanium alloy parts manufacturing mainly relies on casting and forging. Among them, cast parts are easy to manufacture in large sizes, but they are heavy and cannot be processed into fine shapes. Although the precision of forging cutting is good, the main bearing component of the US F-22 fighter is a large cast titanium alloy frame. However, the waste of parts manufacturing is serious, and 95% of the raw materials will be cut off as waste, and the size of the forged titanium alloy is strictly limited: 30,000 tons of large hydraulic press can only forge parts not exceeding 0.8 square meters, even the world's largest 8 For a 10,000-ton hydraulic press, the size of the forged parts must not exceed 4.5 square meters. Moreover, neither of these technologies can produce complex titanium alloy components, and welding will encounter terrible titanium alloy corrosion. The F-22's fuselage bulkhead is machined from titanium alloy forgings

Laser titanium alloy forming technology completely solves this series of problems. Thanks to the superposition technology, it saves 90% of very expensive raw materials. In addition, it does not need to manufacture special molds. The original material cost is 1 to 2 times the processing cost, which only requires 10% of the original. Machining a complex structure of 1 ton weight of titanium alloy, roughly estimated that the cost of traditional technology is about 25 million yuan, while the cost of laser 3D welding rapid prototyping technology is only about 1.3 million yuan, which is only 5% of the traditional process.

More importantly, many complex titanium alloy structures can be integrally formed by 3D printing, which not only saves man-hours, but also greatly improves the material strength. If the titanium alloy forging of F-22 is manufactured using Chinese 3D printing technology, the weight can be reduced by up to 40% when the strength is comparable.

In the field of aviation, China's laser titanium alloy forming technology has been widely used.

F22

In the design and development of the next generation fighters of AVIC Chengfei and Shenfei, laser titanium alloy forming technology has been widely used. Through this technology, the two fifth-generation fighters F-20 and F-31, which are being developed, use a titanium alloy main structure, which successfully reduces the structural weight of the aircraft and increases the weight-to-weight ratio of the fighter. Relying on laser titanium alloy forming, the cost is low With its fast speed, Shen Fei successively assembled multiple fighters such as J-15, J-16, and J-31 within a year and conducted test flights. The rapid manufacturing of the J-16 prototype has largely benefited from the low cost and convenience of 3D printing of titanium alloys. With laser titanium alloy forming technology, China has for the first time been in the forefront of the world's advanced level in the field of aviation materials science. And laid a solid foundation for the development of China's aviation industry.