This article aims to explore the integration of 3D printing and casting technologies. It details the background, application, and outlook of this integration, analyzing the advantages, disadvantages, and applications of various 3D printing techniques in combination with casting. Through practical application cases, it demonstrates the feasibility of rapid manufacturing complex parts by the combination of 3D printing and casting technologies, as well as the achievements in technology sharing, promotion, and innovation. Additionally, it discusses the current situation and future trends of the integrated application of industrial-level 3D printing and casting technologies, emphasizing its significance in promoting the development and transformation of the casting industry.
1. Introduction
3D printing, as a revolutionary technology, has brought about significant changes in the manufacturing field. In the context of the ever-growing demand for diverse castings, the limitations of traditional mold manufacturing techniques have become increasingly prominent. The introduction of 3D printing technology has brought revolutionary changes to the casting industry.
2. Background of 3D Printing and Casting Technology Integration
The 3D printing technology, as the most significant driving force for intelligent manufacturing, has not been widely applied on a large scale. The reasons are not the immaturity of the 3D printing technology itself, but rather the limitations of forming material types, and the high cost of directly printing metal finished products. Many 3D printing suppliers have been continuously improving printing equipment, software, and materials to reduce application costs while exploring new application areas. In industrial development, most products use metal materials, so 3D printing technology must achieve low-cost manufacturing of metal components to survive and develop. However, only a few suppliers have made breakthroughs so far. Due to factors such as price and materials, few military and civilian enterprises adopt this technology. According to incomplete statistics, there are nearly a thousand sets of various idle or semi-idle metal printers in China, resulting in a great waste. It has been proved that it is not realistic to use 3D direct printing for all metal components, thus 3D printing technology must seek new breakthroughs for healthy development.
3. Industrial-level 3D Printing and Casting Fusion Supporting Technologies
3.1 SLS Technology
Selective Laser Sintering (SLS) technology is a universal printing technology. In principle, it can prepare materials into powder, and then melt the powder or binder by selective heating to form the required intermediate parts. In the field of casting, the main printing materials include PS powder, wax powder, coated resin sand, and coated ceramics.
PS powder printing materials and processes are mature, with advantages such as small material shrinkage, small expansion coefficient, stable size under medium temperature conditions, and low material and printing costs. It is the best choice for various investment casting wax patterns. However, due to problems such as pressure differential shell expansion during demolding and the generation of a large amount of black uncarbonized matter during baking, which require professional casting knowledge and high environmental protection costs to solve, it has not been widely used. Currently, SLS technology is mainly used in silica sol investment casting and gypsum vacuum casting.
Wax powder printing materials and processes are not yet mature. Due to the strong water absorption of wax, printing deformation and cracking are very common, and printing parameters are difficult to control, and the material price is expensive. However, wax powder printing materials do not expand the shell and are environmentally friendly, especially with obvious advantages when used for thin-walled small parts. Currently, the use of SLS technology to make wax parts is relatively rare, and it is difficult to adopt in industrial products, and the printing of small wax parts can be replaced by other printing technologies.
Coated resin sand is sand grains coated with resin, which is bonded by heating to melt the resin. Although both it and 3DP technology are sand mold (core) forming technologies, SLS technology is a hot forming process, resulting in large deformation, high strength, low printing efficiency, and high cost. Due to its high strength, it is often used to make slender sand cores. However, due to high costs and a large amount of waste sand, it may be eliminated.
Coated ceramics are ceramic particles coated with resin, which is melted and bonded by heating, and then degreased and sintered. Ceramics have a wide range of applications. In the field of casting, they are mainly used for the internal cores of various complex components. The SLS printing ceramic process is complex and has poor deformation controllability, so it is difficult to promote on a large scale and is gradually being replaced by processes such as 3DP.
3.2 SLA Technology
Stereolithography Apparatus (SLA) technology has a wide variety of printing materials, and the printed parts have high precision and smooth surfaces, so it has long been favored by plastic product users. In casting, it is mainly used for silica sol investment casting, plastic molds, and silicone molds.
For silica sol investment casting, by combining its high precision and smooth surface advantages, thin-walled hollow structures are used in silica sol investment casting. However, due to its large gas evolution, poor 退让性 (not sure what this means, might need further clarification), and slightly higher price, it has not been widely promoted and applied.
Plastic molds have relatively high bonding strength, the printed molds are precise, and their wear resistance is better than that of wooden molds but lower than that of metal molds. They have a slightly higher cost and are suitable for small-batch rapid casting, and a few mold factories adopt them.
Silicone molds have high bonding accuracy and smooth surfaces. By printing SLA molds and then using a vacuum injection molding machine to turn them into silicone molds, they can be used for the manufacturing of wax parts for casting (such as complex and difficult-to-part statues and other components).
3.3 3DP Technology
Three-dimensional Printing (3DP) technology has evolved from planar printing technology. The difference is that 3DP sprays resin and other binders through the inkjet head. The main difficulty of this printing technology lies in the lifespan of the inkjet head. Due to the strong corrosiveness of the binder, the inkjet head is prone to corrosion and clogging. Currently, no inkjet head specifically for 3DP printing has been developed, and most use Fuji inkjet heads borrowed from planar printing, resulting in relatively high prices due to limited usage. In casting, it is mainly used for sand molds, sand cores, foam plastics, and ceramics.
3DP printing is the most mature technology for producing sand molds and sand cores. Sand molds and sand cores belong to the cold forming process, which can print any complex shape without considering the parting issue. The printed sand molds and sand cores have good air permeability and can be directly used for sand casting, or used as sand cores for metal molds. It is also a suitable method for rapidly manufacturing complex conformal chill irons.
Foam plastics are manufactured by bonding foam plastic powder through binders. The printed parts are used for investment casting wax patterns and lost foam casting. This printing method has advantages such as fast printing speed, low softening temperature, no shell expansion, large printing size, and small gas evolution compared to SLS printing, but it has a high price and a slow promotion speed.
Ceramics are made by spraying binders on ceramic powder and then performing degreasing and sintering. Ceramics have a wide range of applications. In the field of casting, they are mainly used for the internal cores of various complex components. The 3DP printing ceramic process is complex, with relatively less current applications but broad prospects.
3.4 SLM Technology
Selective Laser Melting (SLM) technology is a method of directly printing metals. In the field of casting, it can be used for complex molds with runners or heating, as well as components for inlay casting of complex structural parts (such as complex inner cavities and slender oil channels).
The production of complex inner cavity structures and slender oil channel parts is very difficult, mainly due to the manufacturing and cleaning of sand molds and sand cores. The method of overall printing with an offset of 1-3mm for complex inner cavity structures and slender oil channels and then inlay casting well solves the problems of inner cavity cleaning and defects.
4. Application Cases
4.1 Molds
Figures 1 to 4 show the molds made using SLS and SLM technologies. For example, Figure 1 shows a sand casting outer mold printed using SLS technology with nylon, and Figure 2 shows a sand casting core box mold printed using SLS technology with PS powder and then impregnated with resin. Figures 3 and 4 show plastic pressing molds with complex cooling channels directly printed using SLM technology with heat-resistant steel powder materials.
4.2 Investment Casting Wax Patterns
Figures 5 and 6 show the wax parts made using SLS and SLA technologies. Figure 5 shows an investment casting PS powder wax pattern printed using SLS technology, and Figure 6 shows an investment casting photosensitive resin wax pattern printed using SLA technology.
4.3 Lost Foam Casting Patterns
Figures 7 and 8 show the EPS foams made using 3DP technology.
4.4 Sand Mold Printing
Figures 9 to 11 show the sand molds and sand cores made using SLS and 3DP technologies.
5. Current Situation of Industrial-level 3D Printing and Casting Technology Integration
Currently, 3D printing technology has successfully integrated with various casting methods such as sand gravity casting, sand low-pressure casting, metal mold casting, investment casting, and lost foam casting. Industry-related enterprises are exploring its integration with various casting methods such as vacuum pressure casting, differential pressure casting, gypsum mold casting, and the combination of sand mold and gypsum mold. This technology can be used for the rapid production of castings such as aluminum alloys, cast steel, cast iron, cast titanium, and nickel-based alloys.
Many enterprises have now abandoned the traditional mold method for obtaining casting blanks and instead choose the mature 3D printing plus casting method to complete the production of casting blanks, which is fast, low-cost, and has obvious quality advantages, resulting in a strong sense of dependence among enterprises. Utilizing the characteristic that 3D printing manufacturing is not related to the complexity of parts, the original design concept of giving priority to manufacturing has been transformed, effectively improving the functionality of parts, and making the structure of parts more refined and reasonable. Figures 12 to 15 show the castings produced using industrial-level 3D printing technology.
6. Future Outlook
In summary, the integration of 3D printing and casting has broken through the bottleneck of only using molds before casting, solving the problems of high costs and long casting cycles. It has accelerated the development of the casting industry, making complex processes simpler, and promoting revolutionary changes in traditional casting technologies, providing possibilities for the rapid development of personalized innovation factories and the upgrading of the manufacturing industry. The integration of 3D printing and casting has been widely applied in technology-intensive industries such as automobiles, aerospace, and weapons, and is continuously extending to other industries. Its successful application will promote the rapid development of the manufacturing industry.
With the continuous progress of materials science and the maturing of technology, we have reasons to believe that this integration will lead the manufacturing industry towards a more intelligent, efficient, and sustainable future. In the future, more enterprises may adopt this technology to improve production efficiency, product quality, and market competitiveness.
7. Company Examples
7.1 Shared Equipment Company
Shared Equipment Company has made significant achievements in the field of 3D printing and casting technology integration. They have overcome many technical difficulties and have been actively exploring and innovating in this area. For example, they have developed a 3D printing sand core top cold iron fixing method, which can improve the quality and production efficiency of castings. This patent involves a series of steps, including presetting cavities in the sand core during the sand core manufacturing stage, assembling magnets, applying casting glue, fixing the cold iron, and removing the magnets. By this method, the stability of the cold iron fixation is enhanced, and the overall quality of the casting is ensured. Moreover, the operation is simple and efficient.
7.2 Voxeljet
Voxeljet provides 3D sand mold printing technology, which can quickly and precisely manufacture molds. Their technology does not require traditional hard molds for sand mold manufacturing, enabling the rapid production of complex castings. It allows for previously unimaginable designs, such as non-uniform parting lines, optimized gating and pouring system designs, integrated sand molds, conformal vents, and local weight reduction. CAD data is the basis for 3D printing. The model CAD data is uploaded to the 3D printing equipment, and a software slices the model into thin layers, each representing a cross-section of the model. Then, the printing process begins. The used materials are common casting materials, including various silica sands with particle sizes of 140-250 microns, as well as various binders. Voxeljet offers three 3D printers with different build volumes to meet the needs of customers for printing large sand molds or batch sand molds and cores.
7.3 Icewheel Intelligent Machinery Company
This company is a subsidiary of Icewheel Environmental Technology Co., Ltd. They take advanced 3D printing manufacturing technology as the foothold and adopt an intelligent, digital, professional, and green manufacturing approach. By using 3DDP technology to make complex sand molds, they achieve high quality consistency and rapid delivery of complex sand molds and castings. With the adoption of advanced 3D printing equipment, robots, and fully automatic pouring machines, they realize the intelligence of the entire process. Currently, the company has achieved an annual production capacity of 5,000 tons of high-end castings through 3D printing technology, with a per capita capacity of more than 100 tons per year, becoming a 3D printing casting factory with a relatively high level of full-process intelligence worldwide.
7.4 Lixinsheng New Materials Technology Co., Ltd.
Lixinsheng focuses on the research and innovation of new wear-resistant materials. They have adopted industrial-level 3D printing equipment and innovated new processes such as 3D printing + metal mold, iron mold coated sand, and liquid die forging. These new processes can significantly improve the comprehensive performance of castings, save a large amount of casting sand, reduce the environmental pressure, and improve the metal liquid utilization rate. For example, in an actual application, they were able to eliminate the wood assembly and processing process of typical wood mold equipment by using a hybrid platform, reducing the delivery time by more than 60% and the total cost while maintaining the pattern size quality.
7.5 Guangan Ouyi
Guangan Ouyi has independently developed a production-type flagship product – Longyuan Forming 3DP sand mold printing equipment AFS-J1600Pro. This equipment has a forming cylinder size of 1600 × 800 × 600mm, adopts the latest generation of high-stability and low-noise high-speed vibrating powder spreading technology and 2-Pass high-precision printing technology, and cooperates with high-performance forming processes and intelligent algorithm technologies to achieve a printing speed of 15 seconds per layer and a printing accuracy of up to ±0.3mm. The tensile strength of the printed sand mold can reach up to 2.5MPa, the gas evolution is 8-11ml/g, and the surface roughness is ≤Ra25. The equipment adopts a modular design, which is convenient and flexible for maintenance, with low maintenance costs. It is equipped with an intelligent system, making the operation more simple, and can achieve one-click printing, and also has a printing early warning prompt function. It can also realize real-time monitoring, recording, and traceability of the entire processing process through intelligent systems such as visual monitoring. For different casting application requirements such as aluminum casting, cast iron, cast steel, and cast magnesium, it provides open-source sand material process solutions, supporting a rich variety of sand material systems and high-performance binders, curing agents, and cleaning agents to optimize the use cost for users.
8. Conclusion
The integration of 3D printing and casting technologies is a revolutionary development in the manufacturing industry. It combines the advantages of 3D printing’s flexibility and complexity with the traditional casting process, opening up new possibilities for the production of complex parts. Through the analysis of various related technologies, application cases, and the current situation of industrial-level integration, as well as the introduction of several representative companies, it can be seen that this technology has brought significant changes and improvements to the casting industry.
However, there are still some challenges and problems in the development and application of this technology. For example, the performance and stability of 3D printing equipment need to be further improved, and the types and properties of suitable materials also need to be continuously expanded and enhanced. In addition, the training and cultivation of professionals with cross-disciplinary knowledge and practical experience are also crucial to ensure the smooth implementation and optimization of this technology.
Looking forward to the future, with the continuous progress of technology and the continuous expansion of application scenarios, the integration of 3D printing and casting technologies will continue to develop and mature. It is expected to bring more efficient, precise, and personalized manufacturing solutions, promoting the further transformation and upgrading of the manufacturing industry. At the same time, the close cooperation and innovation between enterprises, research institutions, and the government will also play an important role in promoting the development and application of this technology. Only by continuous exploration and innovation can we better utilize the potential of this technology and create more value for the manufacturing industry.
