How Thin can you Cast with Rheocasting?

Much thinner than you’d expect!

In traditional high-pressure die casting (HPDC), wall thicknesses below 2 mm are considered exceptional and are rarely achieved. But Rheocasting changes the game entirely.

Why Conventional HPDC has its Limits

In HPDC, liquid metal is injected at high speed into a mould cavity. It splashes and spreads in all directions, easily reaching complex geometry. That’s great for many shapes, but not for everything.

Rheocasting works differently. The semi-solid metal slurry flows in a much more controlled, directional manner. Instead of spreading wildly, it tends to move straight ahead through the cavity. This means it might initially bypass perpendicular features, such as a rib extending sideways, and only fill them later, once its main flow path encounters resistance.

In conventional HPDC, the liquid metal can splash into thin ribs and quickly solidify. Rheocasting’s globular, laminar metal flow avoids many of those issues, provided air can escape. If venting is done right, even very tall and thin ribs can fill completely and defect-free.

How Alloy Choice Affects Castability

The alloy you choose also plays a significant role. Take a near-eutectic alloy like AlSi10MnMg. It offers good flowability, making it easier to fill narrow features. However, its relatively low thermal conductivity makes it less ideal for heat-sensitive applications.

Here’s why: In HPDC, the high silicon content and dendritic microstructure reduce the flow of electrons and with it, thermal performance. These materials often max out around 140 W/mK. That’s not enough for demanding applications like 5G antenna systems, which generate high heat loads and require top-tier conduction to avoid overheating.

When a heat sink can’t manage heat effectively, electronics suffer. Signal range drops, systems shut down, and the cost of network deployment rises. You could use an active cooling system to help, but that adds cost, complexity, and even attracts wildlife looking for shelter.

In Rheocasting, the castability is independent of the silicon content. As long as the alloy is rheocastable, which the AlSi10MnMg is not, the castability is equally good.

So, How Thin Can You Go?

It depends on the flow distance. With Rheocasting, 2 mm wall thickness for structural castings is routine. Heat sinks with walls as thin as 0.8 to 1.5 mm at the tips, using steeper draft angles, are also achievable. That’s a major weight advantage over conventional HPDC, which requires thicker walls and gentler angles.

Some parts, such as the radio filter in the picture, even achieve a wall thickness of 0.4 mm in the as-cast condition, requiring no machining. Even more impressive, the large adjacent bosses, over 10 mm thick, remain porosity-free.

The Rheocasting Advantage

Rheocasting provides full flexibility to adjust wall thickness precisely where needed, without compromising quality or strength. So, you no longer need to stick to the 3–4 mm standard solely to ensure metal flow. By optimising wall thickness:

• You save weight

• You reduce material costs

• You lower carbon emissions

All while maintaining or improving structural performance. To learn about how Rheocasting can transform your product portfolio, the Rheocasting Workshop is perfect for you.