3D Printing Technology in Metal Casting: Principles and Applications

The paper focuses on 3D printing in metal casting. It elaborates on its principles, e.g., SLS, SLM, EBSM/EBM. The technology offers design freedom, boosts efficiency, and cuts costs. Cases like Oscar statuettes prove its value. However, challenges in materials and accuracy exist. Future holds improved tech, wider application, and better integration with traditional casting.

The principle of 3D printing technology in metal casting

• Principle of Selective Laser Sintering (SLS) Technology : A layer of powder material (mostly metal powder) is pre-laid on the workbench. Under computer control, the solid part of the powder is sintered according to the interface contour information. During processing, the powder is first preheated to a temperature slightly lower than its melting point, and then the powder is flattened under the action of a scraping stick. Selectively sintered according to the layered cross-sectional information under computer control. After one layer is completed, the next layer is sintered. This cycle is repeated layer by layer until the three-dimensional part is formed. Finally, the unsintered powder is recovered into the powder cylinder and the formed part is taken out. For example, when manufacturing metal parts with complex internal structures, SLS technology can construct these complex structures by sintering metal powder.
• Principle of Laser Selective Melting (SLM) Technology : Using a high-energy laser beam to melt the metal alloy powder on the two-dimensional section of the three-dimensional model after slicing, printing any complex structure and metal parts with close to 100% density layer by layer from bottom to top. The process is to first design the three-dimensional model using CAD software and export it into a file format that can be recognized by slicing software; perform slicing operations on the three-dimensional model and add support and layering processing to obtain the cross-sectional contour data of the three-dimensional model; use path planning software to scan and process the contour data, and import the planned data into the SLM device. The industrial computer controls the laser beam to selectively melt the metal alloy powder layer by layer according to the scanning path of each layer of contour, and stacks it layer by layer to form a dense three-dimensional metal part entity. This technology has important applications in manufacturing some key metal components in the aerospace field, such as titanium alloy parts, because it can manufacture high-precision, high-strength parts.
• Principle of Electron Beam Selective Melting (EBSM/EBM) Technology First, the 3D CAD model of the part is sliced and layered, and the obtained discrete data is input into the forming system. Preheating is performed in the forming system, and then the electron beam melts the powder pre-laid on the workbench according to the CAD data of the part. After one layer of processing is completed, the workbench descends by one layer of thickness, and then the next layer of powder is laid and melted. At the same time, the new melting layer is fused with the previous layer. This process is repeated, layer by layer, and directly molded to produce 3D parts. This technology has the advantages of fast processing speed, high energy utilization rate, small vacuum pollution, small residual stress of components, and no reflection, especially suitable for direct molding of active, refractory, and brittle metal materials. For example, when manufacturing some special metal materials in the aerospace field, EBSM technology can play a good role.

The advantages of 3D printing technology in metal casting

• High design freedom
  • 3D printing can fully leverage the role of generative design and topology optimization. In the design stage, unnecessary parts are reduced through algorithms to achieve lightweight printed parts. Taking the aerospace field as an example, by manufacturing safety belt buckles with honeycomb notches through 3D printing, the weight of the aircraft can be reduced, thereby reducing the fuel cost of the aircraft. This design optimization is difficult to achieve in traditional casting processes because traditional casting is limited by factors such as molds, making it difficult to manufacture lightweight designed parts with complex internal structures or thin-walled structures.
  • It can manufacture very complex shapes, such as lattice structures, internal channels, etc. In some high-end manufacturing fields, metal parts that require special heat dissipation structures or fluid channels can be easily constructed with 3D printing. However, traditional casting processes often find it difficult to manufacture these complex shapes because they may be damaged or unable to be demolded during the demolding process.
• Component integration and efficiency improvement
  • Multiple parts can be integrated into a whole for printing. This has great advantages in reducing assembly steps and improving overall product performance. For example, when manufacturing some complex mechanical devices, traditional processes may require manufacturing multiple parts and then assembling them, while 3D printing can print the entire device at once, reducing the connection points between parts and improving product stability and reliability.
  • 3D printing has obvious efficiency advantages for small batch production or the manufacture of individual parts. Traditional casting requires the production of molds when manufacturing individual or small batch parts, which is more expensive and has a longer cycle. However, 3D printing does not require molds and can be directly manufactured according to the design model, greatly shortening the production cycle. Moreover, in small batch production, the cost is relatively lower than traditional casting.
• Save costs and materials
  • In the early stage of product manufacturing, the cost of mold manufacturing is saved because there is no need to make molds (especially for complex shaped parts). For some large or complex casting molds, the manufacturing cost may be very high, and 3D printing can avoid this part of the cost investment.
  • 3D printing is a way of adding materials layer by layer, which can reduce material waste compared to traditional casting processes. Traditional casting may require the removal of a large amount of excess materials when making complex shapes, while 3D printing only adds materials where needed, resulting in higher material utilization.

The case of 3D printing technology in metal casting

• The production of Oscar statuettes
  • The Oscar statuettes have been awarded since 1929, and their production has undergone a transformation in craftsmanship. Starting in 2015, PolichTallix, the company responsible for producing the statuettes, adopted 3D printing technology. First, the designer scanned the early statues from 1929 and the statues from 2015 in 3D, and then designed the digital model based on this, collecting elements and using ZBrush modeling software to establish a data model on the computer. Then, the new design was printed into a 3D model using resin wax by a 3D Systems printer, and then cast with wax. Afterwards, a ceramic material shell was coated on each wax statue, which was then cured and burned at 1600 degrees Fahrenheit. This case demonstrates the application of 3D printing technology in the field of art casting. By using 3D printing, the characteristics of the original design can be accurately restored. Compared with traditional casting processes, the production cycle of complex shaped statues is shorter and more efficient.
• Application of metal 3D printing in parts machining
  • In the field of machining, Renishaw demonstrated the machining of 3D printed parts through a metal 3D printed microwave guide rod case. This microwave guide rod is designed for telecommunications satellites, and the main performance requirements for this part are lightweight and improved microwave propagation efficiency, as well as reducing the space requirements for satellite payloads. The 3D printed guide rod is an integrated part, which is half the weight compared to the guide rod made by traditional design ideas and manufacturing methods (assembled from several parts). When machining this 3D printed part, there are challenges such as whether the stiffness of the part is sufficient to meet the load borne during the machining process and how to align it on the machine tool (because 3D printed parts may have certain deformation during the printing process and lack clear benchmarks). Through a series of solutions, such as establishing expected cutting forces, simulating cutting forces, initial cutting tests, adjusting the design of the 3D printed part, and reconsidering the clamping method of the part (designing a customized fixture for the 3D printed part and directly manufacturing it with 3D printing equipment), the finishing of the part is finally completed. This case reflects the advantages of 3D printing in manufacturing complex structural parts, as well as the challenges and solutions faced when combined with machining.

The challenges of 3D printing technology in metal casting

• Material aspects
  • Material Performance : Research on 3D printing materials for non-ferrous metals still needs to be further explored. Different metal casting application scenarios have different requirements for material performance. For example, the aerospace field may require high-strength, high-temperature-resistant, and fatigue-resistant metal materials, and current 3D printing materials may not fully meet these complex performance requirements. For example, some high-strength titanium alloy materials may have problems such as uneven microstructure during the 3D printing process, which affects the final performance of the parts.
  • Material cost : The cost of 3D printing metal materials is relatively high. At present, aluminum alloy costs about 20,000 yuan per kilogram, which makes the cost competitiveness of 3D printing in large-scale production insufficient. The high material cost limits the widespread application of 3D printing technology in some cost-sensitive metal casting fields, such as some large-scale production of civilian metal products industry, which may prefer traditional casting processes due to cost factors.
• Printing accuracy and quality
  • Despite the continuous progress of 3D printing technology, there are still problems with printing accuracy. When manufacturing some high-precision metal parts, such as tiny metal parts in precision instruments, it may not be possible to achieve the accuracy of traditional precision casting processes. Some factors in the printing process, such as powder particle size and laser energy stability, will affect printing accuracy.
  • The consistency of the quality of printed parts is also a challenge. Quality differences may occur between different batches of printing or different 3D printing equipment, which is a problem that needs to be solved for the metal casting industry that requires strict quality control. For example, in industries such as automobile manufacturing, the quality consistency of metal parts is highly required.
• Cost control and efficiency
  • The high cost of equipment is an important issue faced by 3D printing technology in the field of metal casting. For example, some high-end metal 3D printing equipment, such as those using laser selective melting (SLM) technology, have high component costs, which requires companies to invest a lot of money when introducing 3D printing technology. For some small and medium-sized enterprises, this high equipment investment is a big threshold.
  • The printing speed is relatively slow, especially when manufacturing large metal parts. This limits the application of 3D printing technology in large-scale production, as low production efficiency leads to increased costs. Compared with traditional casting processes, traditional casting can quickly mass-produce metal parts through molds, while 3D printing requires layer-by-layer stacking of materials, which takes longer.

The future development of 3D printing technology in metal casting

• Technological improvement and innovation
  • Accuracy improvement : With the continuous development of technology, the accuracy of 3D printing will continue to improve. In the future, it is expected that by improving the optical system of printing equipment and optimizing the particle size distribution of powder materials, 3D printing can manufacture higher precision parts in the field of metal casting, meeting the demand for high-precision metal parts in fields such as microelectronics and precision machinery.
  • Speed Improvement : Developing new printing technologies or improving existing printing processes to increase the speed of 3D printing. For example, developing new laser scanning strategies or adopting multi-beam of light printing technology can significantly improve printing speed without reducing printing quality, thereby enhancing its competitiveness in large-scale production.
  • Material Innovation : Continuously develop new metal printing materials or improve the performance of existing materials. In the future, metal materials with better mechanical properties, higher corrosion resistance, better thermal stability and other special properties may appear to meet the requirements of different industries for metal casting parts. For example, the marine engineering field may require metal materials with good seawater corrosion resistance.
• Application Area Expansion
  • In-depth application in more industries : Currently, 3D printing has been applied in metal casting in aerospace, automotive, medical and other fields, but there is still a lot of room for expansion in other industries. For example, in the construction industry, 3D printing can be used to manufacture some metal building components with special structures or decorations; in the energy industry, some complex-shaped metal parts can be printed for power generation equipment or oil extraction equipment, etc.
  • Wide application of personalized customization : With the increase of people’s demand for personalized products, the personalized customization advantages of 3D printing technology in the field of metal casting will be more fully played. For example, customized jewelry, personalized high-end mechanical watch parts, etc., 3D printing can quickly manufacture corresponding metal products according to customers’ unique needs.
• Integration with traditional casting techniques
  • In the future, 3D printing technology may be better integrated with traditional casting processes. For example, in the manufacturing of casting molds, 3D printing can quickly produce some complex-shaped mold prototypes, and then mass-produce them through traditional casting processes; or in the repair of parts in traditional casting, 3D printing technology can be used to accurately repair damaged parts, combining the advantages of the two processes to improve the overall efficiency and quality of metal casting.