Review
Materials, Application Status and Development Trends of Additive Manufacturing Technology
2020 Volume 61 Issue 7 Pages 1191-1199
Details
2020 Volume 61 Issue 7 Pages 1191-1199
As an emerging technology, additive manufacturing (also known as 3D printing) is developing rapidly in various fields, which is regarded as one of the important symbols of the third industrial revolution. Here, we introduce its development status, materials and application fields, then analyze its development trends and prospects, which can provide some predictable analysis of the future development direction of additive manufacturing.
Fig. 1 Endur material launched by Stratasys.
The core manufacturing idea of additive manufacturing (AM) technology originated in the late 1980s in United States.1,2) The American Society for Testing Material (ASTM) defines AM as a process of producing goods in a layer-by-layer superimposition way based on three-dimensional (3D) model data, which is contrary to the subtractive manufacturing technology. Usually, materials are superimposed layer-by-layer through computer control, then 3D models on the computer are converted into solid objects ultimately.3–5) Based on different classification principles and understandings, there are many appellations of AM technology, such as 3D printing, rapid prototyping manufacturing, entity free manufacturing, etc.
The traditional machining methods include subtractive manufacturing and equi-material manufacturing, but they often need to be preformed using mold and they are not good at processing workpieces with complex shapes.6–10) AM technology does not need mechanical processing and can directly generate shapes from 3D graphics data, thus it can greatly shorten the development cycle of products and reduce the production costs. Meanwhile, AM technology can produce complex shapes and can achieve product functions in the most optimized design way.11–16)
1.2 Manufacturing processes of AMAccording to the standard classification rules of ASTM and the forming principle of AM technology, the manufacturing processes of AM include vat photopolymerization, powder bed fusion, binder jetting, material jetting, sheet lamination, material extrusion, directed energy deposition, etc. Among them, the common techniques are as follows:
Stereo Lithography Apparatus (SLA) process uses liquid photosensitive resin as raw material, and solidifies layer by layer through computer controlled ultraviolet laser. It can automatically produce the prototype with high surface quality and dimensional accuracy and complex geometry.
Selective Laser Sintering (SLS) process often uses powder materials. Due to it does not completely melt powder, only sinter powder, SLS possesses fast manufacturing speed and high material utilization rate, and can be used in a wide range of materials.
Selective Laser Melting (SLM) process uses large laser energy and can melt metal powder directly, thus it can directly form metal parts with near complete density and good mechanical properties.
Electron Beam Melting (EBM) is a 3D solid part manufacturing method based on the principle of discrete stacking forming, which takes the electron beam with high energy density and high energy utilization as processing heat source to fully melt materials. Due to its ability to directly handle complex geometry, EBM is very suitable for direct production of complex parts in small batches.
Fused Deposition Modeling (FDM) is a rapid manufacturing technology that liquefies hot-melt materials by heating and jets solidification forming. FMD is a low-cost AM method, which uses relatively cheap materials and does not pose the risk of toxic gas and chemical pollution.
Laminated Object Manufacture (LOM) often takes paper and plastic film as raw materials, which can produce large and medium-sized prototype parts with good mechanical properties, the forming time is short and the service life of laser is long. LOM is suitable for conceptual modeling and functional testing parts of product design.
Ultrasonic AM is a new technology developed in recent years, which realizes the integration of ultrasonic forming and manufacturing. It uses ultrasonic wave to melt the metal layer pulled out by common metal sheets based on the traditional “ultrasonic welding” processing, thus completing 3D printing. This method realizes the bonding in real metallurgical sense, and can use a variety of metal materials such as aluminum, copper, stainless steel and titanium.
Three Dimensional Printing (3DP) uses the principle of ordinary printer to connect the printer with computer, loads the raw materials into the fuselage, accumulates the raw materials layer by layer through the computer control, and finally turns the blueprint on the computer into a real object.
Ceramic AM is an emerging technology that directly or indirectly shapes ceramic powders or pastes by means of AM equipment. The traditional ceramic forming technology mainly includes grouting molding, pressing molding, etc. Ceramic AM can realize customized and rapid manufacturing of ceramics with complex structures, replace metal materials such as Ti alloy with bioceramics to realize the manufacture of biodegradable and regenerative implants, and manufacture high-performance ceramic functional parts.
Directed energy deposition (DED) is a kind of AM technology that laser generates molten pool in the deposited area and moves at high speed and materials are directly fed into the high temperature melted area in powder or filament shape and deposited layer by layer after melting. The workblank formed by DED relies on CNC machining to achieve the required precision.
1.3 Development status in major countriesThe United States was the origin country of AM technology. In 2012, the White House announced new measures to revive the American manufacturing with an investment of 700 million dollars. In the same year, the National Additive Manufacturing Innovation Institute (NAMII) was established, which united 14 universities, more than 40 enterprises, 11 non-profit organizations and professional associations. In 2015, the NAMII released a new technology roadmap of AM application research and development (R&D) project.17,18)
The British government regards AM technology as one of the 22 advanced technologies that need to be solved urgently to enhance national competitiveness and meet future challenges in the report “Prospects for High Value-added Manufacturing Technology in the Future”. Since 2011, British has continuously increased the R&D funds of AM technology, and vigorously built relevant research institutions and laboratories. According to statistics, Britain will invest 115 million pounds in AM R&D from September 2012 to September 2022.
Germany established the Direct Manufacturing Research Center (DMRC) in 2008, which mainly studies and promotes the AM application in lightweight structure of the aerospace field. Germany has been at the forefront of the world in the research and application of metal AM technology, and its enterprises account for 50% of the total market share in metal parts AM. The French Rapid Prototyping Association (AFPR) is dedicated to the standard research of AM technology. The main AM research enterprises include BeAM, IREPA LASER, Spartacus 3D, Poly-Shape, etc. In 2016, Poly-Shape cooperated with Thales Alenia Space produced the largest metal AM parts in Europe for satellite.
The AM technology in Japan mainly focuses on bionic organs, preoperative simulators, and high strength material display achievements of the medical field, which has been able to make non-structural organ tissues such as skin, and the important organs with complex structures and physiological functions such as heart will be the next goal.19)
Russia is a big country in laser technology industry. Due to the strong suitability between laser technology and AM technology, AM has developed rapidly with the assistance of laser technology. In 2014, Russia revised the policy documents of “Priority Development Direction of Scientific and Technological Equipment of Russian Federal” and “Synchronized Renewal Plan of Key Technologies Inventory of Russian Federal”, adding new manufacturing technology, AM technology, etc. In addition to making great efforts to develop manufacturing principle and technology, Russia also attaches great importance to cutting-edge application research in AM field, such as battery manufacturing, medical applications, organ printing, etc.
The development of AM technology in China began in the 1990’s. Policy documents such as “National Plan for Promoting the Development of Additive Manufacturing Industry” and “Action Plan for the Development of additive Manufacturing Industry” were successively formulated, which played a significant role in promoting the development of AM industry. At present, China has initially established a technical R&D system with universities as the main body, and AM technology has been applied in manufacturing and maintenance of aircraft compact components and large complex structural parts.20,21)
Materials are key to determine the application scope of AM. The basic properties of AM materials, for the metal laser sintering case, should be conducive to the rapid and accurate processing of prototype parts. The rapid prototyping parts should be close to the final requirements and meet certain requirements of strength, stiffness, moisture resistance and thermal stability, while be conducive to the subsequent treatment process.
Costs, material properties (such as mechanical properties, chemical stability), finished product details after post-treatment and application environments are all important factors that need to be considered in the selection of AM materials.
2.2 Classification according to chemical compositionAccording to the chemical composition, the classification of AM materials is shown in Table 1.22–30)
Due to possessing good mechanical strength and electrical conductivity, metal materials have wide application prospects in aerospace, industrial manufacturing, biomedicine and other fields.
According to the statistical analysis of about 190 conference reports and journals related to AM by Swiss Federal Laboratories for Materials Science and Technology (EMPA) in 2015, the most commonly used materials, as shown in Table 2, are Ti alloy (Ti–6Al–4V), followed by high temperature alloy, stainless steel and Al alloy.
Stainless steel is the cheapest metal printing material, which possesses various smooth and frosted surfaces and is often used for 3D printing of jewelry, functional components and small carvings.31) High temperature alloy has become the main AM materials for aviation industry applications due to its high strength, stable chemical properties, difficult forming and the high cost of traditional processing technology.32)
The mechanical properties of Ti alloy parts manufactured by AM technology are superior to that manufactured by forging process.33) Ti metal powder possesses broad application prospects in automotive, aerospace and national defense industries, which can be used to print automotive parts such as impellers and turbochargers. With the superior properties of light weight and high strength, Mg–Al alloy has also become the preferred candidate material of major manufacturers in AM technology.34) Ga is mainly used as the liquid metal alloy AM material, which possesses metal conductivity, nontoxicity and nonvolatile.35) In the ornament AM material field, the gold, sterling silver and brass are commonly used.
(2) Polymer materialsABS material is the preferred engineering plastic for melting deposition molding process, which is mainly prefabricated into silk and powder for use at present. Its application scope covers almost all daily necessities, engineering supplies and some mechanical supplies.
The application fields of PC engineering plastic include glass assembly industry, automobile industry, electronics, electrical industry, industrial machinery parts, office equipments, medical and health care, leisure and protective equipments, etc. PC laminates are widely used in bank, embassy, public places, protective windows, lighting equipments, industrial safety baffles and bullet-proof glass, etc.
PA material can be directly used to manufacture equipment parts, the PA carbon fiber composite plastic resin parts manufactured by AM technology possess high toughness and can be used for mechanical tools instead of metal.
PPSF material possesses the highest strength, the best heat resistance and the highest corrosion resistance among all thermoplastic materials, which can be used for AM to produce high load-bearing products and become the preferred material to replace metal and ceramic.
PEEK is an ideal artificial bone substitute material which is suitable for long-term implanting into the human body (e.g. as the dental implant material). AM technology based on melting deposition molding principle can be used to fabricate bionic artificial bone combined with PEEK material.
The products printed using EP material possess quite good elasticity, which are easy to recover after deformation, such as 3D printed shoes, mobile phone shells, 3D printed clothes, etc.
Endur is a brand new AM material launched by Stratasys company, which is an advanced imitated polypropylene material (see Fig. 1). Endur can be used to print moving parts, bite and mesh parts, small boxes and containers, which possess good surface quality, good dimensional stability and they are not easy to shrink.
Endur material launched by Stratasys.
Oxford Performance Materials (OPM) company launched two kinds of AM materials for aerospace and industrial manufacturing markets: OXFAB-N and OXFAB-ESD. OXFAB-N is an unmodified poly(ether-ketone-ketone) (PEKK) material, which is suitable for manufacturing microwave antenna (radome) or other special electrical applications due to its low microwave dielectric constant. OXFAB-ESD is a carbonized PEKK material with high strength and low quality mechanical properties. Filarilentarno company of Russian launched a series of flexible and transparent 3D printing materials called “PrototyperSoft”, which are made of rigid rubber polymers such as styrene, butadiene and styrene.
Adaptive 3D company also launched a kind of shape memory polymer, which is hard and transparent at room temperature. When heated, it becomes very soft and easy to bend. Once cooled, it changes back to its original shape. It can be used in automobile manufacturing, footwear industry, aerospace, etc.
PLA is probably the best raw material for AM at first, which is an environment-friendly plastic and can be used in the research of tissue engineering scaffolds.
PETG has low shrinkage and low temperature, and there is almost no odor in the printing process, which makes it possess a broader development and application prospect in AM field.
PCL has low melting point which does not need high printing temperature, so it can save energy. In the medicine field, PCL can be used to print heart stents, etc.
Liquid photosensitive resin has become the preferred material for high-precision 3D printed products due to its excellent liquid fluidity and instantaneous photo-curing characteristics. Photosensitive resin also possesses fast curing speed, excellent surface drying, low odor and low irritant ingredients characteristics, which is very suitable for personal desktop 3D printing system and the printed products have smooth appearance and can present transparent or translucent frosted state. Polymer gel possesses good intelligence, the sodium alginate, cellulose, animal and plant glue, peptone, and polyacrylic acid used for AM can form special mesh polymer gel products after polymerizing under certain temperatures and initiator, cross linking agent actions.
(3) Composite materialsAmong composite materials based on thermoplastic resin, reinforced materials mainly consist of chopped fiber and continuous fiber. For instance, Arevo laboratory in silicon valley printed high-strength carbon fiber reinforced composites, of which the comprehensive properties can be set strictly by precisely controlling the orientation of carbon fiber and optimizing the specific mechanical, electrical and thermal properties. American scientists also printed ultra-light and ultra-thin supercapacitors using graphene composites.
The thermosetting composite materials only realize 3D printing of chopped fiber reinforced composite material in the laboratory. The AM research on ceramic matrix composite materials and metal matrix composite materials has also made some achievements. For instance, Tethon 3D company launched a kind of material named “Castalite”, which is a composite material of ceramic and resin. With excellent heat resistance and shock resistance, Castalite material can print ceramic molds and can be used to cast metal parts after firing, which is suitable for SLA and digital light processing (DLP) 3D printers.
(4) Inorganic nonmetallic materialsCeramic is the main inorganic non-metallic materials used in AM field. Aluminum silicate ceramic powder which is waterproof, heat-resistant, recyclable and nontoxic can be used as ideal home decoration material to print cookware, tableware (cup, bowl, plate, egg cup and cup mat), candlestick, ceramic tile, vase, artwork, etc.
Products printed using composite gypsum powder (full-color sandstone) possess obvious surface texture and special visual effects, which are widely used to make models, portraits, building models and other indoor exhibits.
Blue wax and red wax can be used in investment casting of standard investment casting materials and casting process, such as the paraffin model casting technology of making jewelry, clothing, medical equipments, mechanical parts, sculptures, replicas and collectibles, etc.
(5) Biological materialsBiological cells need to be cultured into cell mediators in the laboratory to produce substitutes similar to fresh meat, using water-based sol as binder and combining with special sugar molecules to make bio-ink, then they are sprayed on biopaper under the control of computer.
As to artificial bone powder, an acid agent can be sprayed on the film made of artificial bone powder by using similar inkjet printing technology to make the film harder, and the artificial bone powder can be transformed into precise skeletal tissue, which realizes the combination of AM and medicine, tissue engineering.
(6) Other materialsOther printing materials, including color gypsum, cement, rock, paper, even sugar and salt, are currently used in a small amount of research, such as using color gypsum to print animation dolls, using sugar to print food, using concrete to print buildings and using wood or paper to print furniture, etc.
2.3 Classification according to physical statesAccording to physical states, AM materials can be divided into liquid, powdery, filiform and sheet/plate states, etc., and the corresponding manufacturing technologies that they adapt to are shown in Table 3.36–42)
Photosensitive resin is the typical representative of liquid materials. In addition, the liquid dissolved by plastic resin in solvent beforehand, gel polymer, monomer that can be polymerized quickly and two kinds of liquids that can be polymerized (e.g. polyurethane) are all currently being tried liquid AM materials.
(2) Powdery materialsThe plastic with high melting temperature, thermal sensitivity, poor thermal fluidity and thermosetting characteristics usually needs to be pulverized by machine and spray drying. In order to ensure good sphericity and fluidity and achieve high sintering accuracy, the polymer materials need to be processed into spherical powder materials with an average particle size between 10∼250 µm, which possess good fluidity and high apparent density. For example, plastic can be made into polymer microspheres used for AM materials by technical means such as vapor deposition.
(3) Filiform materialsIn order to make thermoplastic materials melt rapidly and transport evenly in AM, plastic materials usually need to be prefabricated into monofilaments, which can also compound with other materials to improve their performance according to the product requirements. When filiform polymers are used in AM, it is required that the filaments possess good roundness, bending strength, compressive strength and tensile strength so that there is no wire breakage occurs under the action of traction and driving force, while ensuring uniform and stable feeding.
Ti and Ti alloys which possess high specific strength, good heat resistance, corrosion resistance and biocompatibility are ideal AM materials in aerospace field, including pure Ti, Ti6A14V (TC4) and Ti6A17Nb. Ni alloys with high strength, anti-oxidation and corrosion resistance at 650∼1000°C are also excellent materials. In addition, Al alloys, Cu alloys, ceramic materials and composite materials are also suitable materials.43,44)
In recent years, relevant researchers have printed not only parts of aircraft, missiles, satellites and manned spacecraft, but also parts or finished products of engine, UAV and microsatellite using AM technology.45–48) AM has also been used to customize personalized aircraft interiors, such as seat handrail, luggage rack lock, electronic flight bag bracket, etc. In this process, AM played unique technological advantages, such as optimizing the structure of components, reducing weight, saving expensive strategic materials, etc. For instance, National Aeronautics and Space Administration (NASA) produced the first 3D printed Invar alloy lightweight structure, and developed a new type of copper-based alloy material named “GRCop-42” with high strength and high conductivity, then printed rocket propulsion components using SLM device. The “Pujiang-1” satellite launched in China also used AM technology, with its antenna support printed using Ti alloy material. Rocket Lab’s first battery-powered rocket named “Electron” launched in New Zealand possesses strong launch capability. Main parts of the engine of Electron are all 3D printed parts, which use EBM technology and carbon composites.
In addition to being used to produce key components of aircraft with complex structure, AM has also gradually extended human production and manufacturing activities to outer space. For instance, astronauts aboard the U.S. space station printed a socket wrench, comparing digital model files transmitted by ground crews via e-mail. The European Space Agency (ESA) and Lithoz company printed fake moon dust into screws and gears for future use on the moon. Russian medical company named “INVITRO” printed organs and tissues using its 3D bio-printer in space for the first time. NASA also plans to 3D print houses on the moon. With the gradual improvement of zero gravity AM equipment, the future space station will be transformed from “laboratory” to “mechanical factory”. The space station can be self-repaired and constructed by waste materials recycling and raw materials launched from the earth surface, using solar or nuclear power, thus significantly reducing construction costs and construction cycle.49,50)
3.2 Biomedical fieldAM materials used in biomedical field include implant metals (e.g. stainless steel, Ti–Al alloy, CoCr alloy, Mg alloy), engineering plastics (e.g. PA, ABS), photosensitive resins (e.g. EP, AA), polymer gels (e.g. cellulose, polyacrylic acid), etc.51–54) Biocompatible materials are mainly non-metallic materials, including medical polymer materials and bioceramic materials, which are used for bone substitutes, bioengineering scaffolds, etc.55,56) Among them, biodegradable polymer materials include PLA, PCL, polyglycolic acid (PGA), and poly(lactic-co-glycolic acid) (PLGA). Non-biodegradable polymers include polyaryletherketone (PEAK), polyvinyl alcohol, ultrahigh molecular weight polyethylene, and their composites with nanometer hydroxyapatite. Bioceramic materials mainly include calcium phosphate, biphasic calcium phosphate and calcium silicate/β-tricalcium phosphate.
AM technology is highly compatible with the biomedical industry, which has initially formed a full range of AM products and applications from implants, medical devices, surgical planning, anatomy teaching, pharmacy, and blood vessel to tissues and organs. The advantages of AM in medical device manufacturing are mainly reflected in shortening the development cycle of medical device, realizing the personalized customization and reducing medical costs, etc.57–59)
AM technology has become mature in the human body hard objects printing. Various artificial limbs, dentures, implanted bones, 3D thoracic cavity, and 3D skull have been applied in reality. Organ or cell printing is still in the exploration stage due to the complex structure and high technical requirements. Although some organs and tissues have been successfully printed (e.g. blood vessel, liver, kidney, heart), there is still a long way to go to maintain long-term activity and use for practical application.60,61)
3.3 Industrial information fieldAM can directly print parts, melt mould and wax mould, etc. Nowadays, AM tooling covers a series of tool applications from assembly guides in manufacturing workshops to test and inspecting fixtures on measuring devices.
The application of AM technology in the automobile industry which mainly focuses on experimental model and functional prototype manufacturing in the R&D link at present runs through the whole life cycle of automobile, including R&D, production and use. In the future, the application of AM will expand to the production and use links with larger market space, and the application in final parts production, automotive maintenance and automotive refitting will gradually improve.62–64)
In recent years, in order to meet the increasing demand of multi-functional radio communication system, AM has also been applied to print RF microwave/millimeter wave devices.65) These printed devices were molded directly without any later assembly or adjustment, thus showing better flexibility in their structural design. In the manufacturing process, one method is to print metal powder directly by laser sintering or melting technology, another method is to print non-conductive materials (e.g. resin) and then coat the entire surface with copper for metallization. Due to using low-density and non-metallic materials, the printed devices possess lighter quality.
3.4 Architecture fieldIn architecture field, 3D printed houses have very realistic application scenarios.66–68) For example, AM technology can quickly provide shelter for homeless and poor people, as well as for victims from natural disasters such as earthquakes, tsunamis and hurricanes, etc. In the context of housing shortage and the promotion of green and environment-friendly building concept, building with the help of AM will become a major trend in the future, and some enterprises have started to make positive attempts.
In addition, AM can also print bridges and relic buildings, etc. At present, the world’s first 3D printed steel bridge has been completed and will be installed on a canal in Amsterdam this year. China has also built the first 3D printed resin landscape bridge and relic buildings such as Yungang Grottoes. The buildings printed can meet the requirements of building materials, and the strength and fastness of which are in line with the national construction industry standards.
3.5 Education fieldThe development of AM technology and educational application complement each other. On the one hand, AM enables students experience more intuitive and perceptual cognitive learning mode, which can improve teaching effects when increasing their learning fun. On the other hand, students can also improve their hands-on practical ability in the process from design to printing. The application of AM in education field consists of three categories: curriculum development and training, teaching practice and application, scientific research and innovation, following the progressive level of “cognition-practice-innovation”.
The application and promotion of AM technology in the education field are mainly promoted by the cooperation of state, schools and enterprises.69–72) At the national level, the governments such as United States have placed the AM technology in a strategic position to formulate national development strategy planning. At the school level, some universities, primary and secondary schools have improved students’ awareness of AM technology and cultivated their technical practical abilities by offering courses and training, setting up interest groups, organizing innovative competitions, etc. Some subjects also apply AM to the production of teaching aids to make classroom learning more intuitive, vivid and interesting. At the enterprise level, on the one hand, enterprises such as 3D systems and Stratasys have promoted educational application by donating 3D printers, on the other hand, they also have begun to develop and launch school-oriented AM equipments, relevant courses and textbooks, etc.
3.6 Consumer products fieldAt present, some artists and designers have begun to use AM to produce musical instruments with unique style. In the future, AM will bring more creative and practical musical instruments in addition to flute, panpipe, whistle, and mouth flute, etc.
In recent years, in order to meet the health needs of different groups and create novel and interesting personalized selling points, many kinds of food such as pizza, pasta, cake, chocolate, candy, coffee, and cocktail have been printed, and the food lovers are increasingly embracing 3D printed foods.
With the continuous maturity of technology, AM has also begun to be applied in the field of clothing, shoes and hats, and 3D printed running shoes and cheongsam have also begun to appear in various shows.
In order to meet consumers’ personalized and customized consumption demands, many eyeglasses manufacturers have begun to adopt AM technology. At the same time, 3D printed glasses also have great development space in helping patients with eye diseases to restore vision health.
Whether racing car, humanoid doll or transformer toy, AM can restore the original appearance of design object to the greatest extent. The tightness degree of the tiny parts such as threadlet and screw spike is more in line with the standards, and the quality can also be effectively guaranteed.
With the rapid development of cosmetic industry, some famous cosmetic enterprises with innovative ability and breakthrough spirit have begun to develop cosmetic products such as 3D printed perfume, skin, and facial mask, etc.
The R&D and breakthrough of AM materials are the basis for promotion and application of AM technology, and also the fundamental guarantee to satisfy printing. Strengthening the R&D of materials, forming a complete printing material system and breaking through printing materials are the key to the future development of AM technology.73–78)
At present, the market applications of AM in aerospace, automobile, medical health and other fields have made positive progress, some fields have already passed the break-even point of large-scale application, and the large-scale industrialization is ready for development. If AM achieves breakthroughs in some fields, it will bring the explosive growth of industry.
(1) In view of the current market situation, polymer materials are the mainstream in the manufacturing of consumer products. Nearly all the 3D printed products in daily life are made of ABS, PLA, nylon and photopolymer materials. From the view of market demand and the most long-term development in the future, the market’s desire for products made of metal materials is very urgent. Especially in the application of aerospace and national defense, automobile, and medical industries, there is great space for development. However, the AM technology using metal as raw material is usually expensive, thus developing new preparation methods of metal materials to reduce the overall cost of AM is the key factor of its market application.
(2) With the development of AM technology, the production quality and efficiency of aerospace equipments such as aircraft will be further improved. AM technology can not only greatly reduce the production costs, but also break through the limitations of traditional manufacturing technology on complex shapes. AM brings a revolutionary change in the concept of production and processing, and plays an important role in promoting the development of global aerospace field. However, the difficulties of printing materials, simulation design, process and quality control in the overall application of AM in aerospace field are still need to be solved urgently.
(3) The innovation of manufacturing industry using AM technology can save time and labor, as well improve the production efficiency. In the production of prototype products, AM has obvious rapid manufacturing advantages. In product manufacturing, AM abandons cumbersome and complex materials, which is of great significance to protect environment, reduce resources waste and realize sustainable development. Digitalization and intellectualization are the future development directions of industrial manufacturing. In the future, there will be more innovation fusion in the industrial design field.
(4) At present, the application in the education field of AM is at the expected value expansion stage of technology development, which is expected to be commercialized in the next few years. In the long run, the integrated solution that can provide hardware, software, course training and interactive platform for AM is the development direction in this field.
(5) The application of AM in the consumer products industry mainly focuses on product design and development. AM can produce high complexity products quickly in small batches, in virtue of this advantage, the product development cycle can be shortened and the design cost can be reduced, which is of great significance to the consumer products industry. With the development of AM technology and the improvement of personalized demand, AM will be more used in direct manufacturing.
AM technology possesses many advantages, such as short manufacturing cycle, simple operation, high material utilization rate and low design and manufacture cost, etc. It can effectively remedy the shortcomings of traditional subtractive manufacturing technology, and possesses unique advantages in many application fields.79)
There are strong demands for AM in aerospace, manufacturing, medical equipment and other fields, and the application client shows a rapid expansion trend. The application of AM technology has developed from simple conceptual model and functional prototyping to the direct manufacturing of functional components. In the biomedical field, AM products will gradually change from non-living printing to living printing. AM can shorten the supply chain by reducing the production and assembly of parts. With the development of AM technology, digital inventory, local real-time production and decentralized manufacturing mode are gradually emerging, the personalized demand continues to release, and human society will usher in the era of mass customization.80,81)
This research work was financially supported by the National Science and Technology Library Project (2019XM27). The author expresses sincere thanks to the financial supporter.
