High-Pressure Die Casting Guide
High-pressure die casting (HPDC) injects molten metal into a steel die at high speed and pressure, producing complex near-net-shape parts with excellent surface finish and dimensional accuracy at high production rates.
The HPDC Process
- Die preparation: Die surfaces cleaned, lubricated with water-based release agent. Die temperature maintained at 180-280°C.
- Injection: Molten metal at 600-700°C (aluminum) injected at 0.5-10 m/s. Fill time: 20-100 milliseconds.
- Intensification: Pressure increased to 30-80 MPa and held for 5-20 seconds to feed shrinkage as metal solidifies.
- Ejection: Die opens, ejectors push part out. Cycle time: 30-120 seconds depending on part size.
Key Parameters
| Parameter | Aluminum | Zinc | Magnesium |
|---|---|---|---|
| Melt temperature | 660-720°C | 400-440°C | 640-680°C |
| Injection pressure | 30-80 MPa | 20-50 MPa | 30-70 MPa |
| Plunger speed | 2-8 m/s | 1-3 m/s | 3-6 m/s |
| Die temperature | 180-280°C | 100-180°C | 220-320°C |
| Solidification time | 5-30 sec | 2-15 sec | 3-20 sec |
Common Alloys
- Aluminum A380: Most common. Excellent castability, good strength (324 MPa UTS), corrosion resistant.
- Aluminum A383 (ADC12): Better die filling for complex thin walls. Preferred for automotive.
- Aluminum A360: Better corrosion resistance and elongation (5%). More difficult to cast.
- Zamak 3 (Zinc): Excellent dimensional stability. Long die life (500K-1M cycles).
- AZ91D (Magnesium): Lightest structural alloy (1.8 g/cm³). Good strength-to-weight ratio.
Design Guidelines
- Wall thickness: 1.5-4mm recommended (Al). Thinner <1mm possible with special venting
- Draft angle: 1-3° for internal walls, 0.5-2° for external walls
- Avoid sharp corners: R0.5mm minimum, R1.0mm preferred for structural sections
- Cored holes: Minimum 2mm diameter. Depth ≤ 4x diameter
- Add ribs for stiffness rather than increasing wall thickness (1:1 height-to-thickness ratio for ribs)
Common Defects
- Porosity: Gas entrapment during injection. Mitigated by vacuum assist and optimal gate/speed profile.
- Cold shut: Two flow fronts meet without fusing. Increase metal temperature or injection speed.
- Shrinkage: Insufficient intensification pressure. Apply higher final pressure and longer hold time.
- Flash: Die separation during injection. Check clamping force and die surface flatness.