Working, Advantages, Disadvantages and Applications of Shell mould casting

Shell moulding casting

• Shell-mould casting is an expendable mould casting process.
• It requires the use of a metal pattern, oven, sand-resin mixture, dump box, and molten metal.
• It is used for small to medium parts that require high precision.
• Shell mould casting allows the use of both ferrous and non-ferrous metals, most commonly using cast iron.

The shell mould casting process consists of the six steps:

Pattern creation - A two-piece metal pattern is created in the shape of the desired part.

Mould creation –

• Each pattern half is heated to 175-370 °C.
• The heated pattern is clamped to a dump box, which contains a mixture of sand and a resin binder.
• The dump box is inverted, and it allowing sand-resin mixture to coat the pattern.
• The heated pattern which forms a shell around the pattern.
• The assembly is taken from the oven. The shell is separated from the pattern.

Mould assembly –

• The two shell halves are joined together and clamped.
• If any cores are required, they are inserted.
• The shell mould is then placed into a flask.

Pouring - The mould is clamped together while the molten metal is poured and it fills the mould cavity.

Cooling - After the mould has been filled, the molten metal is allowed to cool and solidify into the shape of the final casting.

Casting removal - After the molten metal has cooled, the mould can be broken and the casting removed. Trimming and cleaning processes are required to remove any excess metal and any sand from the mould.

Advantages

• The high productivity
• Low labor costs
• Good surface finish
•  This process has better dimensional accuracy
•  Very large parts and complex shapes can be produced

  Disadvantages

• High porosity possible
• Secondary machining often needed.

  Applications

    Cylinder heads, Connecting rods, Engine blocks and manifolds, Machine bases.