6 January 2016

What is sand Casting? | Working process | When it use |

Introduction of Sand Casting: 

Sand casting also called as sand moulded casting. It is a metal casting process by using sand as the mould material. In sand casting the metal is melted in the furnace and then poured into the cavity of a sand mould. Sand casting is used to produce a wide variety of metal components with complex geometries. Also, you can check out the advantages and disadvantages to know more about it. 

The basic procedure of sand casting:

  1. First of all, to create a mould, place a pattern in the sand.
  2. Incorporate sand and pattern into a gating device.
  3. Now, remove the pattern from the mould.
  4. Fill the cavity of the mould with molten metal.
  5. Let the metal cool.
  6. Break the mould free from the sand and remove the casting.

Working process of Sand Casting: 

The process cycle for sand casting consist of six stages:

1. Mould Making

In-mould making creates the mould for casting. a sand mould is formed by packing sand into the mould. The sand is packed around the pattern, which is a replica of the external shape of the casting. When the pattern is removed, the cavity that will form the casting remains. The lubrication used on the surface of the mould cavity. The use of lubrication improves the surface finish of the casting. It used based on the sand and molten metal temperature.

2. Clamping 

In clamping prepared for the molten metal to be poured then the mould halves closed and securely together.

3. Pouring 

After the mould has been clamped the molten metal poured into the mould. Pouring can be performed manually or automatically. Enough molten metal must be poured to fill the entire cavity. The filling time is very short in order to prevent early solidification of any one part of the metal.

4. Cooling

The molten metal that is poured into the mould will begin to cool and solidify once it enters the cavity. When the entire cavity is filled and the molten metal solidifies, the final shape of the casting is formed. The mould can not be opened until the cooling time has elapsed. The desired cooling time can be estimated based upon the wall thickness of the casting and the temperature of the metal. Most of the possible defects that can occur are a result of the solidification process. If some of the molten metal cools too quickly, the part may exhibit shrinkage, cracks, or incomplete sections. 

5. Removal

The sand mould can simply be broken, and the casting removed. This step, sometimes called shakeout, is typically performed by a vibrating machine that shakes the sand and casting out of the flask. Once removed, the casting will likely have some sand and oxide layers adhered to the surface. Shot blasting is sometimes used to remove any remaining sand, from internal surfaces, and reduce the surface roughness.

6. Trimming

During cooling, the material from the channels in the mould solidifies attached to the part. This excess material must be trimmed from the casting either manually via cutting or sawing or using a trimming press. The time required to trim the excess material can be estimated from the size of the casting's envelope. A larger casting will require a longer trimming time.

When sand casting is used:

  • Non-symmetrical parts
  • Large parts 
  • More liberal tolerance 
  • Components with internal structure 
  • Used for ferrous or non-ferrous alloys
  • Metals with a high melting temperature
  • Blowers or Impellers
  • Cams, bushing and bearing
  • Electronic components
  • Most hardware
  • Engine block
  • Gas or Oil tank
  • Medical and mining equipment
  • Screw, nuts and gears
  • Pistons and valve

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