Precision investment casting, a specialized casting method, has become indispensable for manufacturing complex components in aerospace and industrial gas turbine applications due to its ability to produce near-net-shape parts with exceptional dimensional accuracy. This study explores the synergistic combination of fused deposition modeling (FDM) additive manufacturing and numerical simulation to optimize the casting process for aluminum alloy impellers.
1. Process Design Methodology
The impeller geometry with 104 mm base diameter and 2.5 mm blade thickness necessitated three distinct gating system configurations:
| Gating System | Advantages | Challenges |
|---|---|---|
| Top-gating | Simplified mold design | Turbulent flow, gas entrapment |
| Side-gating | Moderate filling control | Asymmetric solidification |
| Bottom-gating | Sequential solidification | Extended cycle time |
The thermal behavior during solidification can be modeled using Fourier’s law:
$$ \frac{\partial T}{\partial t} = \alpha \left( \frac{\partial^2 T}{\partial x^2} + \frac{\partial^2 T}{\partial y^2} + \frac{\partial^2 T}{\partial z^2} \right) $$
where \( \alpha \) represents thermal diffusivity and \( T \) denotes temperature distribution.
2. Numerical Simulation and Optimization
AnyCasting simulations revealed critical process insights:
| Parameter | Value |
|---|---|
| Pouring Temperature | 750°C |
| Mold Preheat | 650°C |
| Filling Velocity | 25 cm/s |
| Solidification Time | 15-18 s |
The defect prediction model incorporated Niyama criterion:
$$ NY = \frac{G}{\sqrt{\dot{T}}} $$
where \( G \) is temperature gradient and \( \dot{T} \) represents cooling rate.
3. Additive Manufacturing Integration
FDM-printed PLA patterns demonstrated:
- ±0.15 mm dimensional accuracy
- 1.2-1.8 g/cm³ pattern density
- 85-120°C heat deflection temperature
The ceramic shell formulation achieved optimal properties:
$$ \eta_{slurry} = \mu_0 \left(1 + \frac{\phi}{\phi_m}\right)^{2.5} $$
where \( \eta_{slurry} \) is slurry viscosity, \( \mu_0 \) base viscosity, and \( \phi \) solid loading.
4. Experimental Validation
Final casting quality metrics:
| Parameter | Result |
|---|---|
| Surface Roughness (Ra) | 6.3-12.5 μm |
| Dimensional Tolerance | CT7-CT8 |
| Mechanical Properties | UTS: 310 MPa, Elongation: 4.2% |
The process demonstrated 38% reduction in lead time compared to conventional wax pattern methods while maintaining <0.2% porosity levels in critical blade sections.
5. Conclusion
This research establishes a framework for integrating additive manufacturing with precision investment casting, particularly effective for thin-walled (t < 3 mm) complex geometries. The methodology reduces pattern production time by 65% while achieving equivalent casting quality to traditional processes, validating its potential for high-value component manufacturing.