Abstract: 3D printing technology involves breaking down a three-dimensional digital model into several planar slices, then using a 3D printer to layer powdered, liquid, or filamentary bindable materials according to the slice pattern, ultimately building up a complete object. This article discusses the technical principles, steps, commonly used materials, key technologies, development, and recommendations for 3D printing. Compared with traditional manufacturing technologies, 3D printing technology has many advantages and is currently widely used in fields such as architecture and industrial design. This technology will bring about a significant transformation in the global manufacturing economy.
Keywords: 3D printing; three-dimensional digital model; planar slicing; superposition molding; model making
introduction
3D printing technology (Three Dimensions Printing Technology) is a type of rapid prototyping technology. It decomposes a three-dimensional digital model designed by a computer into several layers of planar slices, and then uses a 3D printer to stack powder, liquid or filament plastic, metal, ceramic or sand and other adhesive materials layer by layer according to the slice pattern, and finally builds up a complete object [1] . This technology integrates cutting-edge technical knowledge from many aspects such as digital modeling technology, information technology, electromechanical control technology, materials science and chemistry. It is a comprehensive application technology with high technical content. 3D printing technology can realize large-scale personalized production and can manufacture shapes that traditional production technology cannot produce. It can also achieve net-shape forming of the first piece, greatly reducing the amount of auxiliary processing in the later stage and avoiding data leakage and time span of outsourced processing. In addition, due to the significant reduction in the time of manufacturing preparation and data conversion, the cycle and cost of single-piece trial production and small-batch production are reduced, which is particularly suitable for the development of new products and the production of single-piece small-batch parts [2] . These advantages have made 3D printing a trend, and it is now widely used in many fields such as architecture, industrial design, jewelry, footwear, model making, automotive, aerospace, medical, education, and geographic information systems. This technology will bring about a major transformation in the global manufacturing economy, and it is also an important symbol of digital manufacturing in the Third Industrial Revolution. The 3D printing industry will become the next sunrise industry with broad prospects.
13D printing technology principles and steps
1.1 Principle
3D printing technology uses a computer-aided three-dimensional design model as a blueprint. Software discretizes and decomposes this model into several planar slices, which are then stacked layer by layer using a CNC forming system via laser beams, hot melt nozzles, etc., to create a solid product. The 3D printer is the core equipment in 3D printing; it is a complex mechatronic system integrating mechanics, control, and computer technology, mainly composed of subsystems such as a high-precision mechanical system, a CNC system, a jetting system, and a forming environment. In contrast to the "subtractive manufacturing" technology of traditional manufacturing, 3D printing follows an additive principle, that is, a "layer-by-layer" stacking principle. It eliminates the need for traditional tools, fixtures, and machine tools, enabling integrated design and manufacturing. This significantly reduces production costs and shortens processing cycles, improves the utilization rate of raw materials and energy, reduces environmental impact, and allows for the design and manufacture of complex structures with more uniform density in the finished product.
Figure 13D creates a structure that is difficult to achieve using ordinary methods.
1.2 Steps
The 3D printer assists designers in creating 3D digital models of products using computer modeling software. Based on these models, the printing process is automatically analyzed. After pressing the "print" button, the 3D printer can then print the product. The principle of 3D printing is the same as traditional printing, only the raw materials used are different. Traditional printing uses "ink," while the raw materials used for 3D printing must be liquefiable, powdered, or filamentous materials such as plastics, metals, ceramics, or sand, which can be recombined after printing and possess suitable physical and chemical properties.
Figure 2 3D printer
1.2.1 Three-dimensional design
The design process for 3D printing involves first creating a model using computer modeling software, then dividing the resulting 3D model into layer-by-layer sections, or slices, to guide the printer in printing layer by layer. 3D design software is the data source for 3D printing; the models required for 3D printing are created using this software. Domestic 3D design software includes CAD, ZW3D, and CAXA, among others. While there are many dedicated 3D printing software programs available, more intuitive, simple, and practical dedicated 3D printing software is still under development.
1.2.2 Slicing Process
Like laser forming technology, 3D printing uses layer processing and stacking to complete the printing of 3D solid objects. The printing process of each layer is divided into two steps [3] . First, the printer reads the cross-sectional information in the file and sprays a layer of special glue on the area to be formed. The glue droplets are very small and do not spread easily. Then, a layer of uniform powder is sprayed. The powder will quickly solidify and bond when it comes into contact with the glue, while the area without glue remains loose. In this way, with the alternation of a layer of glue and a layer of powder, the solid model will be "printed" and formed. After printing, the loose powder can be swept away to "scrape" out the model, and the remaining powder can be recycled.
Figure 3 3D printing process
1.2.3 Complete printing
The resolution of 3D printers is sufficient for most applications, but it can be quite rough on curved surfaces, like jagged edges in an image. To obtain higher resolution items, you can first print a slightly larger object with the current 3D printer and then lightly polish the surface to get a smooth "high resolution" item.
Figure 4: British engineers "print" unmanned aircraft.
Commonly used materials and key technologies in 23D printing
2.1 Commonly Used Materials in 3D Printing
2.1.1 Full-color gypsum materials
The material itself is gypsum-based powder, which is bonded together with an adhesive and embedded in an inkjet head. Products printed using this material are hard and slightly brittle, but it is the only material that can print in full color [4] . The printed samples are bright and lifelike.
2.1.2 Engineering Plastics
Engineering plastics are industrial plastics used as materials for industrial parts or casings. They are plastics with excellent strength, impact resistance, heat resistance, hardness, and aging resistance. There are three main types.
2.1.2.1 PC material
It is a true thermoplastic material, possessing all the properties of engineering plastics. It boasts high strength, high temperature resistance, impact resistance, and bending resistance, making it suitable for use as final components in the transportation and home appliance industries.
2.1.2.2 PC-ISO materials
It is a thermoplastic material that has passed medical and health certification and is widely used in the pharmaceutical and medical device industries. It can be used in professional fields such as surgical simulation, cranioplasty, and dentistry.
2.1.2.3 PC-ABS material
It is one of the most widely used thermoplastic engineering plastics, applied in the automotive, home appliance and communications industries.
2.1.3 Photosensitive resin
It consists of polymer monomers and prepolymers, with the addition of a photoinitiator (or photosensitizer). Under irradiation with ultraviolet light of a specific wavelength (250-300 nm), it immediately initiates a polymerization reaction and solidifies, typically in a liquid state. It is generally used to manufacture high-strength, high-temperature resistant, and waterproof materials. There are three main types.
2.1.3.1 Somos19120 material
It is made of pink material, a special material for casting. After molding, it directly replaces the wax mold prototype for precision casting, avoiding the risks of mold opening and greatly shortening the cycle. It features low ash residue and high precision.
2.1.3.2 Somos11122 material
It is a semi-transparent material, similar to ABS. After polishing, it can achieve a near-transparent artistic effect. This material is widely used in medical research, crafts, and industrial design.
2.1.3.3 SomosNext Materials
It is made of white material, a new PC-like material, with good toughness, better precision and surface quality, and the parts made from it have the most advanced combination of rigidity and toughness.
Other commonly used materials for 3D printing include nylon, metal, paraffin, rubber, and biomaterials.
2.2 Key Technologies of 3D Printing
2.2.1 SLA Stereolithography Technology
The principle of this technology is to focus light of a specific wavelength and intensity onto the surface of a photocurable material, thereby creating a pattern of a single layer of material. The material used is liquid photosensitive resin. Its advantages include fast forming speed, relatively high precision, and excellent surface finish. It is mainly used for manufacturing various molds and models.
2.2.2 FDM Volumetric Molding Technology
The principle is to melt filamentous material into a liquid through an extrusion head of a heater. A micro-nozzle moves in the xy-plane, coating the molten material onto the molded "work." After cooling, one layer of the graphic is complete. The materials used are filamentous materials (paraffin wax, metal, engineering plastics, low-melting-point alloy wire). Its advantages include simple use and maintenance, low cost, and high speed; complex prototypes can be formed in just a few hours. It is mainly used for plastic parts, wax models for casting, samples, or models.
2.2.3 LOM Layered Solid Manufacturing Technology
The principle is that the laser cutting system uses computer-generated cross-sectional contour data to laser-cut the inner and outer contours of a thin material coated with hot melt adhesive on the back into the workpiece. After cutting one layer, a feeding mechanism adds a new layer of paper, and an adhesive pressing device bonds the cut layers together. Materials used include paper, metal foil, plastic film, ceramic film, and fiber paper coated with heat-sensitive adhesive. Its advantages include reliable operation, good model support, low cost, and high efficiency. It is mainly used for the rapid manufacturing of new product prototypes, models, or casting molds.
2.2.43DP Three-Dimensional Powder Bonding Technology
The principle is to first lay a layer of powder, then use a nozzle to spray adhesive onto the area to be shaped, allowing the powder materials to bond and form the cross-section of the part. This process of laying powder, spraying, and bonding is repeated layer by layer to obtain the final workpiece. The materials used are powder materials, such as ceramic powder, metal powder, and plastic powder. Its advantages include fast forming speed, no need for a support structure, and the ability to output color printed products, which is currently difficult to achieve with other technologies. It is mainly used in professional fields.
2.2.5 SLS Selective Laser Sintering Technology
The principle is to first lay a layer of powder material, then selectively sinter it using a controlled laser beam, raising the powder material's temperature to its melting point. The sintered portion solidifies to form a pattern. This process of laying powder and sintering is repeated until the entire model is formed. The materials used are metallic powder materials (Ni-based alloy mixed with copper powder, Ti, Fe, Cu powder, etc.). The characteristics are high precision and relatively high strength of the finished product, with its main advantage being in the production of metallic finished products. It is primarily used in high-end manufacturing fields.
Development and Recommendations for 33D Printing Technology
3.1 Development
3D printing technology can be traced back to 1984. The world’s first 3D printer was born in 1986. It has only recently attracted attention and developed commercial applications. The US government has identified artificial intelligence, 3D printing and robotics as the three pillars for revitalizing US manufacturing. Among them, 3D printing is the first industry to receive government support. China’s Ministry of Industry and Information Technology is also organizing research and development of a 3D printing technology roadmap, a medium- and long-term development strategy, 3D printing technology specifications and standards, as well as special fiscal and tax policies for the development of the 3D printing industry. At present, after more than ten years of efforts, the research team of Shi Yusheng of Huazhong University of Science and Technology has developed the world’s largest “3D printer”. The maximum length and width of the parts that this “3D printer” can process are 1.2 meters. At the same time, the civilian 3D printer market is also rapidly rising, and the number of 3D printer manufacturers is also increasing [5] .
At present, 3D printing technology is mainly used in industrial enterprises for new product design, trial production and rapid printing; personalized product design and rapid printing manufacturing; model making; medical industry; construction industry; automobile manufacturing industry; aerospace; food industry; education and scientific research; military and other industries [6] . In the long run, the scope of application of this technology will be beyond imagination, and it will eventually bring about a disruptive change to people's production and lifestyle. However, due to factors such as materials, cost, printing speed and manufacturing precision, this technology cannot completely replace the traditional subtractive manufacturing method and achieve large-scale industrial production. For a considerable period of time in the future, the two production methods will coexist and complement each other.
3.2 Recommendations
To accelerate the development of 3D printing technology, the government can take measures such as providing active support and guidance through fiscal and financial policies, establishing industry associations, encouraging research and development, and strengthening education and training to further promote the socialization of 3D printing.
3.2.1 Develop a digital manufacturing plan to promote the priority development of the 3D industry.
It is recommended that 3D printing technology be positioned as a key and common technology for productive service industries, cultural and creative industries, industrial design, advanced manufacturing, e-commerce, and manufacturing informatization engineering, and that this industry be included in the priority development industry and product catalog. In terms of fiscal and tax policies, enterprises should be encouraged to invest in, research and develop, produce, and apply 3D printing, and the import and export of 3D printing equipment should be supported.
3.2.2 Strengthen the construction of industry alliances and associations to promote the coordinated development of the 3D industry.
Actively guide industrial design enterprises, 3D digitization technology providers, 3D printer and material R&D enterprises and institutions, and 3D printing service application providers to form industry alliances. Utilize relevant academic societies and associations to strengthen discussions and exchanges, and jointly promote 3D printing technology R&D and industry standard setting. Promote the construction of market platforms for 3D printing technology development, including 3D printing e-commerce platforms, 3D printing data security and intellectual property protection mechanisms, and 3D printing and related project investment and financing mechanisms, to promote the sustainable development of the industry.
3.2.3 Increase technological support and improve the level of 3D printing technology.
A special fund will be established to focus on promoting research and development in key technologies such as digital technology, software control, printing devices, and materials technology. In supporting research and development, it is important to establish a fair and impartial performance evaluation system and encourage various research entities to explore different technological paths. Support for industry-academia-research collaboration in 3D printing will be strengthened, with particular policy support provided to companies implementing industrialization in areas such as market sales and social promotion.
3.2.4 Strengthen education and training to promote the socialization of 3D printing.
Integrate 3D printing technology into the development of relevant disciplines and cultivate 3D printing professionals. Utilize industry associations, expos, forums, and other organizational forms to provide training in 3D printing technology and its related applications. Demonstrate, promote, and popularize 3D printing technology in public institutions such as science and technology museums, cultural and art centers, and youth activity centers. Develop 3D printing service centers to promote the application of 3D printing technology and accumulate application experience for the development of the 3D printing industry.
References
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