Abstract: This paper investigates the application of 3D printing technology in rapid investment casting, which enables the direct manufacture of complex and high-precision castings through digital modeling. This method reduces the cost of new product development and shortens the production cycle. Taking a small impeller as an example, it demonstrates the innovative application of the 3D printing stereolithography apparatus (SLA) process in investment casting, solving problems encountered in traditional precision casting techniques. This not only optimizes traditional casting processes but also promotes the widespread application of 3D printing technology in various fields, bringing revolutionary changes to the manufacturing industry and fostering high-quality development in the casting industry.
Keywords: 3D printing; investment casting; rapid manufacturing; high-quality development
1. Introduction
With the rapid development of technology, 3D printing has gradually integrated into various aspects of our lives. In the industrial field, it has initiated a new production revolution. Investment casting, also known as lost-wax casting, is a precision casting technique that uses wax molds as the modeling material. It has high precision and surface smoothness but is characterized by long mold-making cycles, high costs, and specific requirements for mold materials. 3D printing, which constructs objects by layering materials, can significantly shorten mold-making cycles, reduce costs, and produce complex shapes difficult to achieve with traditional methods. Therefore, the application of 3D printing in investment casting injects new vitality into traditional processes.
2. Materials Used in Investment Casting and 3D Printing
Table 1: Common Materials for Wax Molds in Investment Casting
| Material Type | Main Components | Melting Point Range (°C) |
|---|---|---|
| Wax-based | Paraffin wax, stearic acid, etc. | 60-70 |
| Resin-based | Natural resin | 70-120 |
| High-temp | Rosin, beeswax, polystyrene, etc. | >120 |
| Medium-temp (Rosin-based) | Rosin, wax materials, etc. | 90-110 |
| Medium-temp (Wax-based) | Paraffin wax, other additives | 80-100 |
Table 2: Melting Points of Common Materials for 3D Printing
| Material | Melting Point Range (°C) |
|---|---|
| ABS | 210-240 |
| PLA | 170-220 |
| PETG | 220-250 |
| TPU | 190-230 |
| Photosensitive resin | 60-90 |
| Nylon | 235-270 |
Considering that wax molds melt during the dewaxing process, requiring a low melting point, the use of 3D-printed products as substitutes for wax molds is feasible due to the low melting points of common 3D printing materials.
3. 3D Printing Process in Rapid Investment Casting
3D printing technology can replace two parts of traditional casting processes: mold pressing and wax mold manufacturing. The process flow of combining 3D printing with investment casting.
4. Case Study: Small Impeller Manufacturing
A small impeller (with a bottom diameter of 100 mm, a top diameter of 26 mm, and a side width of 45 mm) is used to demonstrate the application of SLA 3D printing in rapid investment casting.
(1) Digital Modeling
Using modeling software or reverse engineering/3D scanning to generate a digital model, convert it to an STL file, slice it, and generate Gcode. Ensure the model is professional and scientific, considering the integration of 3D printing and investment casting.
(2) Printing the Model
Photosensitive resin (melting point of 70 °C) is selected as the 3D printing material. The 3D model is imported into the slicing software of the SLA machine, and the model is sliced into layers. The resin is uniformly coated on the bottom plate, and UV light is used to cure the resin layer by layer. Final surface finishing (e.g., sanding, polishing) is done to achieve the desired shape and surface quality.
(3) Shell Making
Coat the model with facing and backing slurries, dip it in refractory sand, and let it dry and harden at specific temperatures and humidity. Repeat the coating, sanding, and drying steps 5-6 times to ensure sufficient strength and refractoriness of the shell.
(4) Dewaxing, Firing, and Pouring
Soak the prepared shell in hot water (85-95 °C) to melt and remove the SLA-printed model, obtaining a castable mold. Fire the mold at about 900 °C for 1-2 hours to remove moisture, residuals, and impurities. Pour molten metal into the mold after compacting with dry sand to prevent deformation and cracking.
Table 3: Measured Dimensions of the Casting
| Theoretical Dimension (mm) | Measured Dimension (mm) |
|---|---|
| Bottom Diameter: 100 | Bottom Diameter: 99.80 |
| Top Diameter: 26 | Top Diameter: 26.12 |
| Side Width: 45 | Side Width: 45.23 |
The casting dimensions closely match the theoretical dimensions, demonstrating high precision and good integration of rapid investment casting with 3D printing.
5. Advantages of 3D Printing in Rapid Investment Casting
Table 4: Comparison of Advantages of 3D Printing Process and Traditional Process
| Advantage | Description |
|---|---|
| Fast molding speed | Traditional wax molds take an average of 5 days, while 3D printing can complete them in 1-2 days. |
| High precision | Precision can reach 0.5 mm or even higher. |
| Strong customization | Can meet over 90% of personalized design requirements. |
| High material utilization | Material utilization can reach above 80%, while traditional methods are about 50%. |
(1) Cost Savings
The combined process of 3D printing and rapid investment casting enhances product development efficiency and eliminates tooling and labor costs.
(2) Simplified Process Flow
The complex processes of traditional manufacturing are reduced, enabling the completion of previously difficult or low-quality tasks.
(3) Industrial Application
With the advancement of 3D printing technology and its industrial application, efficiency increases, manufacturing costs decrease, making mass production feasible.
(4) Improved Production Efficiency and Manufacturing Flexibility
The combined technology addresses issues of low production efficiency and flexibility, significantly improving both.
6. Conclusion and Outlook
(1) The SLA 3D printing process can be tightly integrated with rapid investment casting. Photosensitive resin products can replace traditional wax molds in investment casting, achieving high-precision castings with satisfactory appearance quality.
(2) 3D printing is visual, controllable, intuitive, and highly operable, well-suited for rapid development and prototyping of small-batch new products.
Despite rapid development and widespread application, 3D printing faces challenges such as high equipment costs, the need for professional operation, material limitations, and cost-effectiveness in large-scale production. Researchers must actively address these issues.