This study investigates the integration of additive manufacturing (AM) with precision investment casting to optimize the production of thin-walled impellers. Three gating systems – top, side, and bottom injection – were designed and analyzed using numerical simulation to identify the optimal solution for minimizing casting defects.
1. Process Design and Numerical Simulation
The impeller structure features twisted blades with an average thickness of 2.0 mm, presenting significant challenges for molten metal filling and solidification. Key process parameters include:
| Parameter | Value |
|---|---|
| Alloy Type | ZL104 |
| Pouring Temperature | 750°C |
| Shell Preheating | 650°C |
| Filling Speed | 25 cm/s |
Numerical simulation using AnyCasting software revealed distinct solidification patterns:
$$ \frac{\partial T}{\partial t} = \alpha \nabla^2 T $$
Where $T$ represents temperature field and $\alpha$ denotes thermal diffusivity. The side-gating system demonstrated superior performance with:
- 38% less air entrainment compared to top-gating
- 24% reduction in shrinkage porosity vs bottom-gating
- Solidification time of 366.4 seconds
2. Additive Manufacturing Integration
The PLA patterns were fabricated using fused deposition modeling (FDM) with critical process controls:
| AM Parameter | Specification |
|---|---|
| Layer Thickness | 0.15 mm |
| Infill Density | 80% |
| Support Structure | Tree-type |
The ceramic shell formulation followed the ratio:
$$ W_{slurry} = 0.45W_{plaster} + 0.55W_{water} $$
Pattern removal was achieved through thermal decomposition at 750°C with controlled ramp rates:
$$ \frac{dT}{dt} = 5°C/min \quad (25-600°C) $$
3. Quality Validation
Final castings exhibited:
- Surface roughness Ra ≤ 6.3 μm
- Dimensional accuracy CT8-10
- Zero cold shut defects
The precision investment casting process reduced lead time by 68% compared to conventional methods, demonstrating significant advantages for complex thin-walled components. This hybrid approach combining AM and precision casting proves particularly effective for low-volume production of high-precision impellers.