Permanent Mold Casting

Permanent mold casting is the pouring of liquid metal into durable metal molds. A single mold can be used for many thousands of pours, so unlike sand molds it does not have to be made anew each time. The metal solidifies in it quickly, giving castings a fine structure, repeatable dimensions and a smooth surface.

The Permanent Mold Casting Process

1. Mold preparation – cleaning, applying a protective coating and heating the mold to operating temperature.
2. Core setting – metal or sand cores that form the holes and interior of the casting.
3. Pouring – liquid alloy at a controlled temperature flows through the gating system under its own weight.
4. Solidification – the metal mold extracts heat rapidly; the gating system and risers are designed so that the casting solidifies directionally and is free of shrinkage cavities.
5. Opening the mold and removing the casting – the mold is immediately ready for the next cycle.
6. Finishing – cutting off the gating system and risers, grinding, inspection and, where needed, CNC machining, heat treatment and painting.

You will find a detailed, practical description of each stage in the guide permanent mold casting step by step.

Permanent Mold Casting Variants

• Gravity – the classic method: metal flows into the mold under its own weight.
• With a sand-metal mold – combining a permanent mold with cores or inserts made of molding sand makes it possible to produce complex interiors and promotes directional solidification.
• Low-pressure – the metal fills the mold from the bottom, pushed up by low gas pressure.
• With vacuum assist – negative pressure in the mold helps fill thin sections.
• For vibrating molds – vibration of the permanent mold improves mold filling and the casting structure.

All variants serve the same purpose: better mold filling and fewer defects. In our foundry we use gravity casting on permanent mold machines running in an automatic cycle.

Permanent molds and material and energy consumption

Replacing a single-use sand mold with a durable permanent mold reduces the consumption of molding sands and binders, and therefore also the waste and emissions associated with preparing them. In repeat production, it also lowers the energy used per casting.

Permanent mold casting parameters at our foundry

• casting weight: 0.1 to 50 kg,
• permanent mold machines: up to 1400 × 1200 × 750 mm,
• alloys: most often EN AC-42000 (AlSi7Mg) and EN AC-51300 (AlMg5),
• we make the permanent molds and core boxes in our own pattern shop.

See also: aluminum permanent mold castings – parameters and applications, permanent mold casting – our offer i casting molds.