Manufacturing Processes - Gravity Die Casting

Gravity Die Casting or Permanent Mould Casting

Machinery's Handbook, 28th Edition
Machinery's Handbook, 28th Edition

Machinery s Handbook provides mechanical and manufacturing engineers, designers, draftsmen, toolmakers, and machinists with a broad range material, from the very basic to the more advanced. It has always, and continues to provide industry fundamentals and standards while it moves into the 21st century with material reflecting technological advances and offering vast editorial improvements, making the 28th Edition the best tool...ever!

 

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.

Pros

  1. Good surface texture
  2. Equipment costs are relatively low
  3. No need for applied pressure, so mould designs tend to be quite simple
  4. Scrap metal can be recycled
  5. Quick set up times

Cons

  1. High percentage of scrap metal
  2. High occurrence of porosity, but this can be minimized by slower pouring
  3. 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

Gravity Die Casting - Courtesy of Wikipedia http://en.wikipedia.org/wiki/Casting_%28metalworking%29#Die_casting
Gravity Die Casting - Courtesy of Wikipedia http://en.wikipedia.org/wiki/Casting_%28metalworking%29#Die_casting

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Graity Die Casting - Your Comments 3 comments

Cayden Ryan profile image

Cayden Ryan 6 years ago from Strasburg

now what's the difference between gravity die casting and lost wax casting?

for example:

http://www.ppcpinc.com/lost_wax_casting.html


Technoman profile image

Technoman 6 years ago Author

If you look at investment casting (lost wax casting) you will be able to see the difference. In a nutshell for lost wax you create a shell around a wax pattern, then displace the wax with heat in a furnace then use the remaining pattern (investment) to create the casting by pouring in molten metal. With gravity die casting you use a permanent mould and produce the form in the mould material.


Cayden Ryan profile image

Cayden Ryan 6 years ago from Strasburg

Thanks for the clarity, I was asked the difference by a friend and coworker, yet I couldn't find the right words to describe the difference, thank you for helping solve that problem.

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