Kinaguiden is a precision aluminium die casting company based in Stockholm, Sweden, specialising in custom mould design, HPDC, re-engineering, and global logistics.
Aluminium can be cast using several different processes, and the choice between them significantly affects tooling cost, production speed, part quality, and minimum order quantity. The two most common methods for industrial aluminium components are high-pressure die casting (HPDC) and gravity casting (also called permanent mould casting). Understanding when to use each can save both time and money.
What Is High-Pressure Die Casting (HPDC)?
In high-pressure die casting, molten aluminium is injected into a hardened steel mould at pressures typically between 700 and 1,000 bar. The metal fills the mould in milliseconds, then solidifies under pressure. The mould opens, the part is ejected, and the cycle repeats.
HPDC is the fastest aluminium casting process and produces parts with the finest surface detail, tightest dimensional tolerances, and thinnest achievable wall sections. It is ideal for high-volume production.
What Is Gravity Casting?
In gravity casting (permanent mould casting), molten aluminium is poured into a metal mould and fills it under gravity alone — no external pressure is applied. The slower fill speed means the metal can be more carefully controlled, which results in lower porosity and better mechanical properties in some applications. Gravity casting moulds are typically made from softer tool steel or cast iron and are less expensive to produce than HPDC tooling.
Key Differences at a Glance
| Factor | HPDC | Gravity Casting |
|---|---|---|
| Tooling cost | Higher (hardened H13 steel) | Lower |
| Cycle time | Very fast (seconds) | Slower (minutes) |
| Min. wall thickness | 0.8–1.5 mm | 3–4 mm |
| Dimensional tolerance | ±0.1 mm | ±0.3–0.5 mm |
| Surface finish | Excellent (Ra 1.6–3.2) | Good (Ra 3.2–6.3) |
| Mechanical properties | Good | Better (heat-treatable) |
| Best volume | 500+ pieces | 10–500 pieces |
| Part complexity | Excellent | Moderate |
When to Choose HPDC
- Production volumes above 500 pieces per year
- Thin walls (below 3 mm) or complex internal geometry
- Tight dimensional tolerances required
- High surface quality for visible or anodized parts
- Parts with integrated bosses, ribs, threads, and inserts
- EMI enclosures, heat sinks, automotive structural parts
When to Choose Gravity Casting
- Low production volumes (10–500 pieces) where tooling cost is critical
- Parts that require heat treatment for higher mechanical strength
- Thick-walled structural parts where porosity must be minimised
- Prototypes or short-run production before committing to HPDC tooling
The Break-Even Point
The classic question is: at what volume does HPDC tooling pay for itself compared to gravity casting? As a rough guide, HPDC becomes more cost-effective than gravity casting at annual volumes of approximately 300–500 pieces, depending on part size and complexity. Above that volume, the lower unit cost of HPDC more than compensates for its higher tooling investment.
Not sure which process is right for your part? Send us your drawing or sample and we'll advise on the most cost-effective manufacturing approach for your volume and requirements — including whether HPDC or an alternative process is the better fit.