Manufacturing Processes - Gravity Die Casting
Gravity Die Casting or Permanent Mould Casting
Gravity Die Casting
Gravity die casting is a simple casting process which utilises reusable metallic moulds. The process is primarily used for simple shapes with some basic coring possible. It is mostly suited to casting light alloys but can also be used for steel and cast irons.
The two halves of the mould are sprayed with a coating (usually silicate based) and then put together using locating pins to align the two halves and clamped. The mould is heated using gas burners prior to pouring the molten metal. The mould will typically have a runner for pouring and a riser to allow the molten metal to run through, the filling process is normally aided by spraying the mould with lubricants just prior to pouring.
The coating serves two purposes:
- to act as a release agent that prevents the molten metal adhering to the metal die
- to prevent premature solidification of the molten metal
Once poured the mould is allowed to cool before being opened to release the casting. Further machining will be necessary to remove any excess material and heat treatment may be required dependent on component use.
- Good surface texture
- Equipment costs are relatively low
- No need for applied pressure, so mould designs tend to be quite simple
- Scrap metal can be recycled
- Quick set up times
- High percentage of scrap metal
- High occurrence of porosity, but this can be minimized by slower pouring
- Only good for simple 3D shapes, cannot be used for complex shapes
There are new coatings becoming available for gravity die casting that are much longer lasting than the silicate based coatings and that prevent the need for constant retouching up and extend the useful life of the moulds.
Gravity Die Casting Machine
Gravity Die Casting or Permanent Mould Casting
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