Sand Casting and CO2 Process

We at Essen Aluminium manufacture sand castings by the conventional floor molding and bench molding methods of producing castings using either loose patterns which is still very widely practiced in the copper-base alloy casting industry and they have the very big advantage that for small quantities of castings the pattern costs are the cheapest. Hence, a very versatile process in terms of low quality and minimum manufacturing cost.

Sand Casting and CO2 Process

Advantages of Sand Casting Include:

  • Low tooling costs
  • Largest casting sizes achievable
  • Very low gas porosity is possible
  • General versatility of the process is good

Limitations Include:

  • Low casting rate
  • 3-5mm minimum wall thickness
  • Poor linear tolerance (e.g. 4mm/m)
  • Rough surface finish
  • Coarser grain size than gravity die casting

CO2 Casting

often known as match plate molding, very widely used for the smaller and medium sized castings. In fact, it is probably true to say that the biggest tonnage of castings is produced by this method. Our modern molding machines enable a very high rate of production to be achieved, and also with accurately made metal patterns considerably greater dimensional accuracy of the castings is obtained.

This process is used for making moulds and cores. Instead of using sand bonded with natural clay, sodium silicate is mixed with silica sand and this is converted during gassing with CO2 to a form of silica which acts as the binder for the sand grains. The CO2 process enables existing pattern equipment to be employed and it has the advantage that greater accuracy can be achieved because the mould may be gassed, and thereby partially hardened before the pattern is withdrawn from the mould, reducing the amount of rap required to withdraw the pattern.

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