Sand Casting
Black Sand Casting
Black Sand Casting entails pushing a shape into two parts of sand, that are then stacked and filled with liquid metal. This is usually done for iron (due to the carbon content), but also possibly steel, and even materials like aluminium and copper. The melting point of a material is no issue with this technique.
Best suited for: Parts that deal with high thermal loads, such as brake drums for cars.
- Relatively cheap
- Cheap mold, so suitable for smaller quantities
- Welding not possible due to carbon content
- Coarse surface (Ra 12.5+)
- Air entrapment due to fast cooling
- Relatively large tolerances compared to yellow sand casting (DCTG 10+)
Yellow Sand Casting
A sand mold is baked within a regular mold. This “cake shape” is then filled with liquid metal.
Best suited for: High quality materials, such as steel alloys, particularly in larger series. An example are the teeth of trenchers.
- Better tolerances than Black Sand Casting (DCTG 9-10)
- More complex shapes possible
- Less air entrapment
- Longwearing material
- Finer surface (Ra 12.5)
- More expensive than Black Sand (but still relatively cheap)
- High mold costs, so mostly used for high production quantity
Lost Foam Casting
Comparable to Black Sand Casting, but the hollow mold is not produced by pushing the shape into sand, but by putting a preformed polystyrene (tempex) shape in it. This tempex model melts off when the liquid metal is poured in. Polystyrene leaves a lot of carbon, making this method less suitable for the pouring of steel.
- Comparable advantages to Black Sand Casting
- More complex shapes possible compared to Black Sand Casting
- Comparable disadvantages to Black Sand Casting
- Unsuitable for steel
- Relatively high mold costs, so not a good choice for low quantities
