Currently, 3D printing technology is widely used in automotive manufacturing, aerospace and defense, consumer goods, electrical and electronic devices, biomedical applications, cultural and creative jewelry, construction engineering, and education, among many other fields. According to the global authority on 3D printing industry research, the “Wohlers Report 2020” (which separates aerospace and defense applications in its […]
Currently, 3D printing technology is widely used in automotive manufacturing, aerospace and defense, consumer goods, electrical and electronic devices, biomedical applications, cultural and creative jewelry, construction engineering, and education, among many other fields.
According to the global authority on 3D printing industry research, the “Wohlers Report 2020” (which separates aerospace and defense applications in its statistics), automotive manufacturing is the largest field of application for 3D printing technology, accounting for 16.4% of the usage. Consumer electronics and aerospace follow closely behind, at 15.4% and 14.7% respectively, as shown in Figure 1-16.
The research also indicates that prior to 2020, 3D printing was primarily used for model manufacturing, accounting for 24.6% of applications, mainly for design validation and functional testing during various product development processes, making it the largest market for 3D printing since its inception.
However, from 2020 onwards, the direct manufacturing of end-use products using 3D printing technology has increased to 30.9%, as shown in Figure 1-17, becoming the largest use of 3D printing technology. This demonstrates a significant evolution of 3D printing from rapid prototyping to direct end-product manufacturing.
Economist Carlota Perez suggests that each technology-driven industrial cycle revolution lasts about 60 years, with the first 30 years being the invention phase of the foundational technology, and the latter 30 years being the phase of accelerated technology application. Since the creation of 3D Systems, the first company to produce 3D printing equipment in the United States in 1986, the year 2021 marks the beginning of the latter 30 years.
Therefore, the application of 3D printing technology is expected to accelerate, unleashing greater application value and profoundly transforming related industries. This section will introduce typical applications of 3D printing technology in the fields of biomedicine, aerospace, and industrial production, and then discuss the limitations and risks of future applications of 3D printing.
Based on application scenarios, current uses of 3D printing in biomedicine primarily include preoperative planning models, surgical guides, implants, and medical auxiliary tools. Additionally, bioprinting for regenerative medicine and tissue-like organs represents the frontier of biomedical engineering research and is the main direction for future development and application of 3D printing in biomedicine.
Preoperative planning models involve converting a patient’s CT imaging data into a three-dimensional model using reconstruction technology and then materializing the model with 3D printing. These models enable three-dimensional visualization of pathology, addressing the challenges of understanding and evaluating two-dimensional sectional images.
They provide doctors with intuitive and precise information on the location of the disease, spatial anatomical structure, shape, and volume, aiding in the formulation of complex surgical plans, preoperative rehearsals, and postoperative outcome assessments, thereby significantly improving the accuracy and safety of surgeries.
The latest 3D printing technologies can now produce materials that combine soft and hard textures, facilitating surgical incisions and enhancing the tactile experience for surgeons. This also benefits the training and skill improvement of young medical professionals.
Patient History Summary: A 40-year-old female patient experienced persistent headaches for more than two months, accompanied by vision impairment. A brain tumor was detected upon examination, surrounded by intracranial arteries, suggesting surgery, albeit with high risk.
The hospital merged the patient’s CT and MRI images, as shown in Figure 1-18, and performed a three-dimensional reconstruction to accurately restore the patient’s intracranial situation, including the skull, arteries, veins, and tumor, as shown in Figure 1-19. Then, using Zhuhai Cenat New Technologies Co., Ltd.’s WJP model 3D printer, a full-color 3D print of the reconstructed cranial model was produced, as shown in Figure 1-20.
With the help of this 3D model, doctors were able to clearly observe the distribution of blood vessels around the tumor, which informed their intraoperative decisions. By identifying blood vessels enveloped by the tumor, surgeons could precisely excise the tumor while protecting critical vascular structures.
After an 11-hour surgery, the patient’s meningioma in the saddle area of the brain was successfully removed in segments, with the surrounding bilateral anterior cerebral arteries, middle arteries, and internal carotid arteries remaining intact. The surgery was a tremendous success.
Patient History Summary: A 56-year-old female patient was diagnosed with malignant liver tumor and cirrhosis. A normal human liver is about 1500 cm³, but the patient’s liver was only 765 cm³, with severe functional deficiencies. The hospital determined that a liver transplant was the only effective treatment, and after matching, her 21-year-old son was found to be a suitable donor.
It was crucial to precisely excise both the donor and recipient liver portions and to accurately anastomose the blood vessels and bile ducts, which required high surgical expertise. The hospital conducted a three-dimensional reconstruction based on preoperative CT data of the patient’s and her son’s livers, as shown in Figures 1-21(a) and 1-22(a), respectively.
The reconstructed livers were then printed at a 1:1 scale using Zhuhai Cenat New Technologies Co., Ltd.’s WJP model 3D printer, as shown in Figures 1-21(b) and 1-22(b), allowing for an accurate assessment of the lesion’s extent and the three-dimensional spatial relationship with adjacent organs and tissues, and to plan the surgical approach and incision locations.
The surgery was highly successful, and the mother’s life was extended thanks to her son’s liver.
Surgical guides, designed digitally and manufactured using 3D printing, are key tools for transferring preoperative plans to intraoperative execution. They can help avoid trauma to important blood vessels and nerves, reduce blood loss, and enhance surgical safety.
The materials commonly used for printing such products include high-polymer nylon and high-strength, resilient resins (e.g., osteotomy guides which need to withstand sawing during surgery), transparent resins with sufficient strength (e.g., dental implant guides), and standard resin or PLA materials for guides that do not require high strength (e.g., sacral neuro puncture guides and cerebral hemorrhage puncture guides).
3D printing technology can produce implants that are perfectly tailored to individual needs and can be successfully implanted in the body. These implants can be manufactured with controllable micro-pore sizes, which can reduce the Young’s modulus of the metal material, decrease stress, and promote bone integration, offering advantages unmatched by traditional implants.
The common material for such 3D-printed implants is titanium alloy powder, as shown in Figures 1-23 and 1-24. For implants that do not require excessive load-bearing and friction, such as intervertebral fusion devices, cranial bones, and small joints like the mandibular joint, researchers are exploring the use of new materials like PEEK (Figure 1-25) and magnesium alloys.
Patient History Summary: In 2014, a 12-year-old male was diagnosed with Ewing’s sarcoma with the cancerous lesion located in the atlas vertebra, as shown in Figure 1-26. The standard international treatment is to support the void left by the excised cancerous atlas with a titanium mesh cage, fixed in place using holes in the mesh combined with a titanium plate and screws at the front, to achieve spinal fusion and rebuild cervical stability.
However, the supporting force and contact area of the titanium mesh are limited, and its resistance to rotation and various bending forces is weak. The presence of “stress shielding” often causes the vertebrae adjacent to the mesh cage to collapse after surgery, making it difficult to maintain the intervertebral height. Additionally, the thickness of the titanium plate can cause swallowing difficulties for the patient.
Postoperatively, the patient would need to have pins inserted into the head and scapula, with a brace installed above and below to immobilize the head. During rest, the head cannot touch the bed, a condition that must be maintained for 3 to 4 months, and sometimes even up to six months, causing great pain to the patient.
The patient was treated by Professor Liu Zhongjun of the Orthopedics Department at Peking University Third Hospital (PUTH), and after two surgeries via both posterior and anterior cervical approaches, was fitted with the world’s first 3D printed custom atlas vertebra, as shown in Figure 1-27. This successful operation overcame the drawbacks of traditional treatment methods and saved the patient’s life.
Traditional medical auxiliary tools are often obtained through plaster casting and low-temperature thermoplastic molding. However, due to the water absorption and shrinkage characteristics of plaster, model deformation can occur, affecting the precision of the tool, and the production process is too dependent on the technician’s personal experience.
Customized, lightweight rehabilitation aids, manufactured using 3D printing technology based on body surface information obtained through optical 3D scanning and combined with patient CT and MRI data and computer-aided precise design, conform better to ergonomics. They can meet individual patient needs and i
mprove postoperative recovery or non-surgical rehabilitation orthotic effects, as shown in Figure 1-28, which displays various types of 3D printed medical auxiliary tools. The future development of 3D printed personalized medical auxiliary tools includes new types of prostheses, hearing and speech function compensatory aids, and novel disability life support systems such as exoskeleton robots.
The materials commonly used for printing these products include high-polymer nylon materials (such as various orthoses with excellent strength and resilience), TPU materials (such as various types of foot biomechanical compensators), and PLA or high-strength resin materials (such as some rehabilitation fixation supports that do not require excessive force).
Patient History Summary: In 2018, a 14-year-old female patient was diagnosed with spinal scoliosis, with a Cobb angle of 13° shown on the full-length spinal X-ray, and she did not receive appropriate treatment. A follow-up in January 2020 showed an increase in the Cobb angle to 27°. The patient sought treatment at the 3D Printing Center of Shanghai Ninth People’s Hospital affiliated with Shanghai Jiao Tong University School of Medicine.
She was fitted with a 3D printed scoliosis orthosis, and six months later, the patient’s spine had been completely corrected. The progression of the patient’s spinal scoliosis is shown in Figure 1-29.
The 3D Printing Center, based on the patient’s specific condition, captured the three-dimensional surface data of the patient’s body using a 3D body scanner (Figure 1-30) and combined it with X-ray data for computer-aided design, creating a fully customized scoliosis orthosis model. This was further materialized into a scoliosis orthosis through 3D printing, as shown in Figure 1-31.
The scoliosis orthosis, due to its fully personalized design and hollow structure, was breathable and lightweight, making it comfortable for the patient to wear for over 20 hours a day.
Internationally, research and exploration into low-cost, short-cycle, high-performance 3D printing manufacturing technology for difficult-to-machine, large, and complex metal components in aerospace has been ongoing. Companies such as Boeing, Lockheed Martin, Northrop Grumman, and institutions like the Los Alamos National Laboratory in the United States have invested over two decades of continuous R&D.
In China, teams led by academician Wang Huaming from Beihang University and Professor Huang Weidong from Northwestern Polytechnical University have also conducted decades of continuous R&D, achieving innovative research results.
For instance, Academician Wang’s team was the first in the world to break through key technologies in the laser forming process, equipment, and application of large titanium alloy load-bearing components for aircraft, addressing the problem of forming “large components” and producing the largest and most complex titanium alloy main load-bearing integral components in China’s aircraft equipment, with comprehensive mechanical properties reaching or exceeding those of forged parts.
3D printing technology, as a novel manufacturing technique, has distinct advantages in the field of aerospace with evident service benefits, mainly reflected in the following aspects:
For aerospace weapon equipment, weight reduction is an eternal research theme, as it not only increases the agility of flight equipment during flight but also increases payload capacity, saves fuel, and reduces flight costs.
The pursuit of extreme lightweighting and reliability in aerospace and military equipment makes the manufacturing of large complex integral structures and precision complex structural components particularly difficult, becoming one of the bottlenecks in the development of advanced aerospace and military equipment.
For example, new aircraft, spacecraft, and engines increasingly use integral structural components, leading to a continuous increase in the size and complexity of individual components. Additionally, there is a significant increase in the use of alloy materials such as titanium alloys, high-temperature alloys, and ultra-high-strength steels, which are very difficult to process using traditional hot working and mechanical machining.
The application of 3D technology can optimize complex component structures, allowing for lightweight design while ensuring performance, thus achieving weight reduction. Optimizing part structures can also lead to the most rational distribution of stress, reducing the risk of fatigue cracks and thereby increasing service life.
At the same time, it’s possible to control temperature through reasonably complex internal flow channel structures, achieving the optimal combination of structural design and material usage.
In the aerospace manufacturing field, many components produced using traditional manufacturing methods have low material utilization rates, generally not exceeding 10%, and sometimes only 2% to 5%. The significant waste of materials means that mechanical machining processes are complex and production cycles are long.
For difficult-to-machine parts, the machining cycle can be greatly increased, significantly extending the manufacturing cycle and thus increasing manufacturing costs. Metal 3D printing technology, as a near-net-shape technique, has high material utilization and manufacturing costs are not affected by the internal complexity of the parts.
Taking the manufacturing of the titanium alloy integrally bladed rotor for the JSF aircraft’s lift fan as an example, traditional “subtractive” manufacturing would start with a 1500 kg forged blank, and after traditional milling, the final part weighs 100 kg, resulting in a material utilization rate of only 6.67%, with a very long manufacturing cycle, as shown in Figure 1-32. However, if 3D printing technology is used, material savings of up to 80% can be achieved.
One of the most outstanding advantages of 3D printing technology is that it can directly manufacture physical parts from the 3D models designed by R&D personnel without the need for machining or any molds, significantly shortening the manufacturing process for high-performance, large-size structural components.
For example, in the manufacturing of the main windshield frame for China’s C919 large aircraft, as shown in Figure 1-33, Professor Wang Huaming’s team from Beihang University used independently developed metal 3D printing process technology. From receiving the part’s 3D model data to the delivery of the finished part for installation, it only took 40 days and cost 1.2 million yuan.
In contrast, ordering the part from abroad would take at least 2 years and the mold cost would be 13 million yuan. Similarly, for the central wing spar of the C919, which is over 3 meters long as shown in Figure 1-34, traditional manufacturing methods would require a super-tonnage press for forging, which is time-consuming, labor-intensive, and wastes raw materials.
Moreover, at the time, there was no equipment in China capable of producing such large structural components. If the part were to be ordered from abroad, the period from order to installation would take more than 2 years, severely hindering the aircraft’s R&D progress and affecting the domestic production rate of the large aircraft.
Professor Huang Weidong’s team from Northwestern Polytechnical University used independently developed metal 3D printing equipment and technology to manufacture the part in about a month. After passing performance tests by COMAC, it was successfully applied to the first prototype of China’s C919 large aircraft.
In the 1980s and 1990s, using traditional manufacturing methods, it would take at least 10-20 years to develop a new generation of fighter jets, such as the J-10 fighter, which took nearly 10 years to develop. With the application of 3D printing technology, China introduced the carrier-based J-15 fighter in just 3 years, directly entering the third-generation carrier-based fighter matrix.
Undoubtedly, 3D printing technology is creating a “Chinese speed” in the development of the Air Force.
The repair and maintenance of damaged components in aerospace equipment have always been a significant issue. The use of Laser Engineered Net Shaping (LENS) 3D printing technology for part repair introduces a new method of maintenance for aerospace equipment. For example, in the case of high-performance integrated turbine blades, if one blade is damaged, the entire turbine rotor faces scrapping, with a direct economic loss worth millions.
Currently, based on the layer-by-layer printing characteristic of LENS, the damaged blade can be considered a special substrate. By performing laser cladding deposition on the locally damaged area, the part can be restored to its original appearance, meeting or even exceeding the performance requirements of the original material.
Moreover, due to the controllability of the 3D printing process, the negative impacts of the repair are very limited. For defense forces, this means that effective solutions can be provided on-site without the need for a spare parts warehouse, significantly improving part repair efficiency and reducing maintenance costs.
In the future, 3D printing technology may be deployed at the forefront of the battlefield, realizing direct printing of parts on the battlefield and eliminating the intermediate steps of manufacturing, distribution, and storage.
Currently, the U.S. Navy has initiated the “Print the Fleet” project, developing a series of procedures for part printing, qualification, and delivery, and evaluating various 3D printing technologies and materials for military use to achieve the goal of manufacturing aircraft parts on naval vessels at sea.
In the future, 3D printing technology may also be deployed in space stations to realize direct 3D printing of parts in space. In August 2014, NASA transported a 3D printer capable of operating in a vacuum environment to the International Space Station, where astronauts not only printed test pieces but also functional structural components.
China also conducted its first in-orbit 3D printing experiment in May 2020 and was the first in the world to achieve space 3D printing of continuous carbon fiber-reinforced composite materials, as shown in Figure 1-35.
Below are three cases of 3D printing applications in the aerospace field in China.
On May 15, 2021, at 07:18, the “Tianwen-1” lander and orbiter separated, successfully soft-landing on the surface of Mars, as shown in Figure 1-36. Subsequently, the “Zhurong” Mars rover successfully sent back telemetry signals. The 7500N variable thrust engine used for the Mars landing was the 2.0 version of the engine used for lunar landings.
The improved “Tianwen-1” 2.0 version 7500N variable thrust engine had the same performance and thrust as the previous Chang’e lunar project’s 7500N engine but was only one-third the weight and volume, with a more optimized and compact structure, as shown in Figure 1-37.
For this, the engine’s docking flange frame was 3D printed in one piece for the first time, avoiding deformation caused by removing large excess material from solid bars or forgings, and also effectively reducing weight.
On May 8, 2020, at 13:49, the return capsule of China’s new generation manned spacecraft test vehicle, developed by the China Aerospace Science and Technology Corporation Space Technology Research Institute, successfully landed in the designated area at Dongfeng landing site.
The successful completion of the test vehicle’s flight mission marked a prototype for China’s new generation manned spacecraft and significant breakthroughs in a batch of new technologies in fields such as cabin structure, materials, and control systems.
One of the important technological breakthroughs was the design and 3D forming of an integrated titanium alloy frame with a diameter of 4m, achieving goals such as weight reduction, cycle shortening, and cost reduction. The successful return of the new generation manned spacecraft test vehicle also marked the successful test of the integral 3D printing technology for oversized key structural components.
Figure 1-38 shows the landing situation of the return capsule of the new generation manned spacecraft test vehicle and its oversized integrated titanium alloy frame obtained through 3D printing.
On May 21, 2018, the Chang’e-4 relay satellite “Queqiao” was successfully launched at the Xichang Satellite Launch Center. Its working orbit in deep space will help humanity further unveil the mysteries of the far side of the moon. With limited launch capabilities, the weight index of “Queqiao” was extremely strict. The skew reaction wheel bracket, one of the heavier components on the satellite, was designed for weight reduction.
Topology optimization was performed using Altair’s Inspire software, changing the design philosophy from “designing the product structure first and then checking the product performance” to “determining the product performance first and then obtaining the final product structure through topology optimization,” achieving a lightweight design.
Further, using aluminum alloy 3D printing, the integral manufacturing was carried out, achieving lightweight manufacturing. Figure 1-39 shows the printed product of the skew reaction wheel bracket for the “Queqiao” relay satellite and its assembly on the satellite.
Initially, 3D printing technology in industrial production was primarily utilized for prototyping during product development, verifying design, structure, and assembly testing. For example, before mass production of a new product, it is necessary to evaluate the product to identify any design issues promptly.
It can simulate the real operating conditions of the product for assembly, interference checks, functional testing, and manufacturability and assembly inspections. Additionally, it can be used for mold making, where 3D printing technology creates master molds for vacuum casting and investment casting pieces, injection molds, etc.
These are then combined with traditional manufacturing processes to produce molds for mass production. After more than 30 years of development, 3D printing technology is now widely used in the industrial field for direct manufacturing of end parts, including direct printing of some molds. It can also print conformal cooling injection molds, which have significant advantages over traditional injection molds.
Traditional product development and validation generally involve CNC machining, which has limitations in processing complex products with hollow, hollowed-out, high-precision, thin-walled, or irregular structures. Even if CNC can process some of these, the cost is very high, making it more suitable for structurally simple, thick, and heavy parts.
3D printing offers advantages such as fast processing speed, one-time molding, and cost not being affected by product complexity. It is now widely used across various industries for design validation, assembly verification, and small batch testing during product development. Common 3D printing materials used for product development and validation include photopolymer resins and high-polymer nylon materials.
Photopolymer resin materials produce parts with smooth surfaces but lower strength, while high-polymer nylon materials are suitable for products requiring higher strength and toughness. Figure 1-40 shows images of some 3D printing product development and validation cases.
With traditional machining methods, plastic molds generally use straight-through cooling channels, which are ineffective for cooling thin-walled or deep-cavity parts, as shown in Figure 1-41(a). With metal 3D printing technology, molds with conformal cooling channels can be directly printed, as shown in Figure 1-41(b), ensuring there are no blind spots in mold cooling.
Conformal cooling injection molds have the following clear advantages:
① They can effectively improve cooling efficiency, reduce cooling time, and increase injection production efficiency, generally improving by 20% to 40%.
② They improve cooling uniformity, reducing product warping and deformation and stabilizing dimensions, thereby enhancing product quality.
A customer’s generic panel plastic part was manufactured using a metal 3D printed conformal cooling core. The mold cycle time was reduced from 55 seconds to 43 seconds, and the output increased from 1300 pieces per day to 1670 pieces per day, improving production efficiency by 28%. The part’s daily revenue was originally 39,000 yuan, which increased to 50,100 yuan after using 3D printing.
After deducting the costs of injection materials, depreciation, and power, the daily profit increased by 2,100 yuan. One set of such molds (operating for 180 days a year) can bring an additional profit of 2,100 x 180 = 378,000 yuan. With ten sets, the profit can increase by 3.78 million yuan, showing very good returns, as shown in Table 1-1.
Table 1-1: Production Comparison Before and After Using Metal 3D Printing to Manufacture Conformal Cooling Cores
| Comparison Item | Traditional | 3D Printing | Note |
| Production Cycle (seconds) | 55 | 43 | |
| Output (pieces/day) | 1300 | 1670 | Based on 20 hours of production per day |
| Unit Price (yuan) | 30 | 30 | |
| Revenue (yuan/day) | 39,000 | 50,100 | Profit increase of 2,100 yuan/day |
A customer’s split air conditioner fan blade, as shown in Figure 1-42(a), originally had a beryllium copper core in the middle part of its mold, as shown in Figure 1-42(b). Beryllium copper material has fast heat conduction and good cooling effects, but it is not wear-resistant and has a lifespan that is one-quarter that of steel parts, requiring replacement after approximately 30,000 pieces, increasing the workload for mold maintenance.
Later, a 3D printed mold steel core was adopted, as shown in Figure 1-42(c), which, due to the design of a reasonable conformal cooling water passage, can produce more than 120,000 pieces and also improves the efficiency of injection molding production. The mold has a total of 66 sets; after one year, all were replaced with 3D printed mold steel cores, resulting in a total cost saving of over 300,000 yuan, as shown in Table 1-2.
Table 1-2: Use cost comparison table for mold beryllium copper core parts and 3D printed core parts.
| Type | Service Life | Unit Price (yuan) | Annual Output of Fan Blades (10,000 pieces) | Number of Replacements | Axle Cost (yuan) | Machinist Cost (yuan) | Tuning Cost (yuan) | Cumulative Cost (yuan) |
| Beryllium Copper Parts | 30,000 pieces | 400 | 2,200 | 768 | 768 x 400 = 307,200 | 768 x 200 = 153,600 | 768 x 150 = 115,200 | 576,000 |
| 3D Printed Parts | 120,000 pieces | 480 | 2,200 | 192 | 192 x 480 = 92,160 | 192 x 200 = 38,400 | 192 x 150 = 28,800 | 159,360 |
Investment casting, also known as precision casting, often uses wax material to create the disposable patterns, hence it is commonly known as “lost wax casting.” Wax patterns for investment casting are frequently manufactured using 3D printing.
The investment casting production process for a piece of jewelry proceeds through the various steps shown in Figure 1-43: (a) 3D design model of the product; (b) the wax pattern is printed using a 3D wax printer; (c) the wax support is dissolved; (d) the finished wax model is obtained; (e) a wax tree is created; (f) the wax tree is placed into a metal mold; (g) gypsum is poured to form the gypsum mold and vacuum is applied; (h) the gypsum mold is baked at high temperatures to burn out the wax, obtaining a gypsum negative mold; (i) metal is melted; (j) the metal is cast into the gypsum mold and the gypsum is dissolved in water; (k) the semi-finished product is washed in hydrochloric acid and dried; (l) the metal jewelry tree is dismembered; (m) grinding and polishing are performed; (n) the final jewelry product is obtained.
(a) 3D Design Model of the Product
(b) Wax Pattern Printed by 3D Wax Printer (White Part is Support Material)
(c) Dissolving Wax Supports
(d) Obtaining Finished Wax Pattern
(e) Creating Wax Tree
(f) Placing Wax Tree into Metal Mold
(g) Pouring Gypsum to Form Gypsum Mold and Applying Vacuum
(h) High-Temperature Baking in Oven to Burn Out Wax and Obtain Gypsum Negative Mold
(i) Metal Melting
(j) Metal Casting into Gypsum Mold and Dissolving Gypsum with Water
(k) Washing Semi-finished Product with Hydrochloric Acid and Drying
(l) Dismantling Metal Jewelry Tree
(m) Grinding and Polishing
(n) Obtaining Final Jewelry Product
Sand casting involves creating molds and cores from casting sand (commonly silica sand) and a binder to produce metal castings. This traditional process typically requires manual or semi-manual creation of wooden patterns for the sand molds and cores.
However, with 3D printing technology, sand molds and cores can be printed directly from design data, significantly improving the efficiency of mold creation, shortening production cycles, reducing manufacturing costs, and offering higher precision compared to traditional sand casting. It also allows for the casting of parts with thin walls and complex internal structures.
A thin-walled clutch housing was produced through sand casting, with dimensions of 465mm × 390mm × 175mm and a weight of 7.6kg, divided into upper and lower parts. Germany’s Voxeljet company used high-quality GS09 sand to 3D print the sand mold with extremely thin walls, as shown in Figure 1-44(a). The part was then cast using G-AlSi8Cu3 alloy, as depicted in Figures 1-44(b) and (c).
The entire manufacturing process took less than 5 days, and the produced clutch housing had the same performance as parts later mass-produced after passing testing, thus providing a significant time and cost advantage for the customer.
The intake manifold, located between the throttle body and the engine’s intake valves, is called a manifold because the air divides after entering through the throttle. The manifold must distribute the air-fuel mixture or clean air as evenly as possible to each cylinder, which means the lengths of the gas passages within the manifold should be as equal as possible.
To reduce gas flow resistance and increase intake, the inner walls of the intake manifold should be smooth. Racing car intake manifolds have many interference areas, posing challenges for sand casting and subsequent machining. To meet the precise requirements of complexity, Voxeljet divided the intake manifold model into four parts for 3D printing of the sand molds, avoiding deformation issues during assembly.
The manifold dimensions were 854mm × 606mm × 212mm, the total sand mold weighed approximately 208kg, as shown in Figure 1-45(a), and the printing time was 15 hours. The cast aluminum alloy intake manifold weighed about 40.8kg, as shown in Figure 1-45(b).
Silicone molding is a process that uses a prototype part to create a silicone mold under vacuum, into which liquid resin is poured to replicate the original part. These replicas have performance close to injection molded products and can be color-customized to meet client requirements.
The materials are poured using vacuum or low-pressure pouring methods, with vacuum pouring mainly used for producing small to medium-sized parts, such as consumer electronics casings, while low-pressure pouring is used mainly for large parts, like car bumpers.
Traditionally, prototype parts for silicone molds were created using CNC machining, whereas 3D printed prototypes for silicone molds are typically made rapidly using photopolymer resin materials through the SLA process. Each silicone mold can produce about 10-20 pieces, with an accuracy of ±0.2mm/100mm, a minimum casting thickness of 0.5mm, optimal at 1.5-5mm, and a maximum casting size of about 2 meters.
The process flow is as follows:
① Prototype Creation: A prototype is produced based on the product’s 3D data using 3D printing.
② Silicone Mold Creation: After the prototype is made, a mold frame is constructed, the prototype is fixed in place, and ‘sprues’ and vent holes are created. The sprue is the inlet for material, also known as the ‘gate’. The size and shape of the sprue should be designed based on the material’s flow properties and the part’s size.
Liquid silicone, vacuum-degassed, is poured into the mold to cover the product completely. The mold is then baked to accelerate the silicone’s curing, and after 8 hours, the silicone mold is cut open to create two halves, the prototype is removed, and the silicone mold creation is complete.
③ Vacuum Casting: After closing the silicone mold, it is placed in a vacuum casting machine, where the air is evacuated or a low-pressure environment is created, and then the material is injected.
After filling, the material is cured for 30-60 minutes at a constant temperature of 60-70°C, then demolded. If necessary, a secondary curing is performed for 2-3 hours at 70-80°C. After the material has cured, the mold is removed, opened, and the replicated product is obtained. This cycle is repeated to produce small batches of replicas.
Silicone molding technology is faster, less costly, and has shorter production cycles compared to injection mold technology, significantly reducing development expenses and R&D timelines.
It is commonly used in the development and design of automotive parts, producing small batches of plastic parts for performance testing and road trials, such as air conditioner housings, bumpers, air ducts, encapsulated vents, intake manifolds, center consoles, and dashboards. Figure 1-46 shows two examples of silicone molds and replicated parts made using 3D printed prototypes.
3D printing technology is increasingly used for the direct manufacturing of end-use parts or products in various fields such as aerospace, military, medical, automotive, home appliances, and consumer electronics. In the automotive manufacturing sector, researchers and companies continually experiment with direct manufacturing of parts and even entire vehicles using 3D printing.
For example, Ford Motor Company operates nearly 100 various 3D printers across more than 30 factories worldwide and has been investing in this technology for decades. Ford uses 3D printing not only for development and verification but also for the production of final parts and tools.
Other automotive giants like Mercedes, BMW, Audi, Volkswagen, Toyota, Cadillac, Tesla, Ferrari, Lamborghini, and Porsche also extensively apply 3D printing in their vehicle development and manufacturing.
Lightweighting is a global automotive industry trend, and the pursuit of lighter vehicles will become more extreme in the future. Automotive lightweighting aims to significantly reduce the vehicle’s curb weight while ensuring strength and safety, improving power and range, reducing fuel consumption, lowering exhaust pollution, and even enhancing vehicle handling and safety.
Metal 3D printed automotive parts are 40-80% lighter than traditional parts, which can reduce CO2 emissions by 16.97g/km. Some lightweight parts feature complex internal lattice structures that reduce weight while enhancing performance.
Lightweighting encompasses material, design, and process aspects, such as using high-strength steel, titanium alloys, and aluminum alloys; optimizing structure, integrated and topology designs; and employing advanced manufacturing processes to improve part performance and achieve greater weight reduction.
As 3D printing technology evolves, an increasing number of automotive parts can be directly manufactured and used, and 3D printing is poised to trigger a new wave of upgrades in the automotive manufacturing industry.
The BMW Group has consistently been a pioneer in the automotive industry’s adoption of 3D printing technology. The BMW i8 Roadster utilizes 3D printing technology to produce a metal convertible top bracket, which is used directly in mass production, as shown in Figure 1-47(a).
This 3D printed metal bracket connects the convertible top cover to the spring hinge, facilitating the folding and unfolding of the roof without the need for additional noise-dampening measures, such as rubber dampers or stronger (and heavier) springs and drive units. The bracket is required to lift, push, and pull the entire weight of the roof and needs a complex geometry that is impossible to achieve through casting.
The final design produced a lightweight, lattice structure using metal 3D printing technology, optimizing support for the roof while minimizing displacement to prevent the cover from collapsing during opening, as shown in Figure 1-47(b). This 3D printed bracket won the 2018 Altair Enlighten Award, recognizing significant advances in lightweight technology, and garnered considerable attention for its innovative design at the award ceremony.
Another end-use 3D printed part used directly in the BMW i8 Roadster is the window guide rail, as shown in Figure 1-48. Thanks to nylon 3D printing, the guide rail was developed and moved into mass production in just five days, capable of producing over 100 window guide rails within 24 hours. The part is installed inside the doors of the BMW i8 Roadster, allowing the windows to operate smoothly.
BMW’s publicly available production information indicates that the weight of the BMW i8 Roadster was reduced by 44% in 2018. The company has produced over one million parts using 3D printing to date. In 2018 alone, BMW Group’s 3D printing production center output exceeded 200,000 parts, a 42% increase compared to the previous year.
The Bugatti Chiron is capable of accelerating from 0 to 400 km/h in just 42 seconds, pushing the limits of physics, and Bugatti’s success stems from continual optimization of their systems and successful application of new materials and processes. Among these, the new Chiron’s brakes are the most powerful in the world, with eight and six pistons in the front and rear calipers, respectively.
Previously, the brake calipers for the Bugatti Chiron were made from high-strength aluminum alloy, weighing 4.9 kg. The new calipers have been structurally optimized based on biomimicry principles and are 3D printed from aerospace-grade titanium alloy, weighing just 2.9 kg, a 40% reduction in weight, as shown in Figure 1-49.
The development of the new calipers was incredibly fast, taking just three months from the initial concept to the first printed component. The most time-consuming part was simulating and optimizing the strength and stiffness of the new design, followed by simulating the printing process to ensure smooth completion.
The caliper measures 41 cm in length, 21 cm in width, and 13.6 cm in height, printed using a four-laser melting system, and took 45 hours to print. After printing, the part and base plate were heat treated at 700°C in an annealing furnace and allowed to cool with the furnace to eliminate residual stresses and ensure dimensional stability, a process that took 10 hours.
The part was then removed via wire-cutting, supports were eliminated, and the part was ground and polished using a combination of physical and chemical methods to improve fatigue strength and increase long-term durability during the vehicle’s later use. Finally, thread machining (to connect the pistons) was completed on a milling machine, requiring 11 hours.
While 3D printing technology has demonstrated strong application advantages during its proliferation, it also faces numerous limitations and risks. Only by clearly understanding, solving, or avoiding these issues can 3D printing fully leverage its advantages and continue to expand its application scope and domains.
Most 3D printers currently exhibit the following prominent issues: First, the size of the equipment is small, typically with printing dimensions concentrated around 400mm×400mm×40mm, and few exceed 1000mm. Second, the efficiency is relatively low, with long part printing times and high costs. Third, surface roughness and dimensional accuracy are not yet ideal.
For example, precision casting can achieve surface roughness better than Ra3.2μm, and even below Ra1.6μm, while the best level for laser 3D printed metal parts is currently around Ra6.4μm, generally above Ra10μm, and for electron beam powder bed 3D printing, surface roughness is Ra20-30μm.
Fourth, the materials are limited; each 3D printing process type is restricted to a very limited number or types of materials, unable to meet some fields’ requirements.
Table 1-3 provides the main SLM equipment manufacturers and their parameters, both domestic and international.
| Company/School | Typical Equipment Models | Laser Type | Power/W | Build Envelope/mm | Beam Diameter/μm |
| EOS | M280 | Fiber | 200/400 | 250×250×325 | 100~500 |
| Renishaw | AM250 | Fiber | 200/400 | 250×250×300 | 70~200 |
| Concept | M2 cusing | Fiber | 200/400 | 250×250×280 | 50~200 |
| SLM Solutions | SLM 500HL | Fiber | 200/500 | 280×280×350 | 70~200 |
| South China University of Technology | Dmetal-240 | Semiconductor | 200 | 240×240×250 | 70~150 |
| Huazhong University of Science and Technology | HRPM-1 | YAG | 150 | 250×250×400 | Approximately 150 |
Workers who operate metal 3D printers or engage in post-processing typically come into contact with metal powders that are less than 100 microns in size. These fine particles can easily enter the lungs or mucous membranes, causing respiratory or neurological damage. It is essential to wear protective clothing and gas masks to mitigate these risks.
Furthermore, metal 3D printing often requires inert gases such as argon or nitrogen to prevent oxidation during processing. If these inert gases leak, they pose a severe risk, being undetectable by the human body, and can be inhaled unbeknownst to the victim. The air we breathe contains 21% oxygen; a drop below 19.5% due to a leak can cause oxygen deprivation and harm.
This is particularly likely in enclosed spaces, so users of metal 3D printers must be aware of this potential danger and take preventive measures.
In metal 3D printing workshops, airborne powders of metals like titanium, aluminum, and magnesium can become concentrated and, if they encounter an ignition source, can burn or even explode. The finer the powder, the more susceptible it is to combustion. Therefore, the storage, processing, and post-processing of metal powders must avoid ignition sources and static electricity.
Additionally, powder spillage can pose environmental risks. In 2014, the Occupational Safety and Health Administration (OSHA) in the United States cited a safety incident where a metal 3D printing facility failed to equip proper firefighting gear, leading to an operator being burned. Although the fire resulted from improper equipment handling, the incident still serves as an important safety reminder.
While 3D printing technology drives technological progress and offers convenience, it also introduces risks in various applications that deserve close attention.
For instance, 3D-printed firearms can pose risks to personal safety and public order; 3D-printed drugs can pose risks to drug control and health; 3D-printed goods can infringe on trademarks, copyright, and intellectual property rights, and even 3D printing may pose risks to personal information security, property safety, and ethical norms.
As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.
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