Abstract: This paper investigates the impeller investment casting process utilizing FDM 3D printing additive manufacturing technology and numerical simulation software. Various gating systems, including bottom-casting, top-casting, and side-casting, were designed. Numerical simulation analysis was conducted using AnyCasting software to determine the optimal gating scheme. Qualified castings were produced through the combination of additive manufacturing techniques and investment casting processes. The results demonstrate that AnyCasting software can accurately predict investment casting defects, and the integration of investment casting with additive manufacturing yields excellent castings. This research addresses casting defects arising from cumbersome impeller mold manufacturing processes.

1. Introduction
Investment casting, a special type of casting within the casting molding industry, is typically used to produce precise and complex components, playing a crucial role in aviation and industrial gas turbine fields. This process involves several steps: creating a wax pattern, injecting it with ceramic slurry and hardening, melting the wax to obtain a mold, drying and preheating the mold to near the molten metal’s temperature before pouring, letting the metal solidify, breaking the mold, cutting the gating system, and finally grinding to obtain the final casting.
Table 1: Main Steps in Investment Casting Process
Step Number | Process Description |
---|---|
1 | Create a wax pattern |
2 | Inject ceramic slurry and harden |
3 | Melt the wax to obtain a mold |
4 | Dry and preheat the mold |
5 | Pour molten metal into the mold |
6 | Let the metal solidify |
7 | Break the mold and cut the gating system |
8 | Grind to obtain the final casting |
By integrating additive manufacturing with investment casting, 3D-printed models replace traditional wax patterns as molds. Shells are directly made on these models, and after high-temperature firing to remove the 3D-printed models, pouring and forming of the castings can commence. This technology significantly shortens the part development cycle and reduces production costs.
2. Impeller Structure and Design
The impeller has a bottom diameter of 104 mm, a top diameter of 25 mm, and a side width of 49 mm. The blade wall thickness is determined to be 2.5 mm, considering the complexity of the casting shape and curved blades, which results in a complicated mold cavity interior. This complexity can lead to unstable metal pouring, affecting the surface quality and precision of the impeller casting.
3. Gating System Design and Simulation Analysis
Three gating system schemes—top-casting, side-casting, and bottom-casting—were designed based on the impeller structure and casting design principles.
Table 2: Designed Gating System Schemes
Gating System | Description |
---|---|
Top-casting | Metal enters from the top |
Side-casting | Metal enters from the side |
Bottom-casting | Metal enters from the bottom |
Numerical simulation analysis was performed using AnyCasting software. The top-casting simulation revealed turbulent flow and potential gas entrapment, leading to shrinkage defects at the bottom. The side-casting simulation showed stable filling but potential defects at the runner and blade interfaces due to fast filling. The bottom-casting simulation demonstrated sequential solidification and minimal defects on the blade surface.
Table 3: Simulation Results Summary
Gating System | Filling Stability | Defect Location |
---|---|---|
Top-casting | Unstable | Bottom of casting |
Side-casting | Stable | Runner and blade interface |
Bottom-casting | Stable | Runner corner |
4. Investment Casting Experiment
Based on the simulation results, the bottom-casting system was selected. The impeller mold was printed using FDM 3D printing technology. Investment casting was then performed, involving mixing plaster and water, coating the mold, drying, heating to vaporize the PLA material, pouring molten aluminum alloy, cooling, and removing the casting.
5. Results and Discussion
The resulting impeller casting exhibited no welding marks, pores, or shrinkage defects, with just a layer of oxide skin on the surface. After sanding, a clean impeller casting was obtained.
6. Conclusion
This study successfully produced aluminum alloy impeller castings using 3D-printed molds and the investment casting process. The results demonstrate that investment casting can be effectively combined with additive manufacturing to produce high-quality castings, addressing casting defects associated with traditional mold manufacturing processes.