Green sand moulding

Green sand moulding 

A green sand mould is composed of a mixture of sand (silica sand SiO2), clay (act as binder), and water. The word green is associated with the condition of wetness or freshness and because the mould is left in the damp condition, hence the name “green sand mould”. This type of mould is the cheapest and has the advantage that used sand is readily reclaimed. But the mould being in the damp condition, is weak and cannot be stored for a longer period. Hence such moulds are used for small and medium sized casting.

1. Open-sand method
2. Bedded-in-method
3. Turn-over method

Open-sand Method

It is simplest form of green sand moulding, particularly suitable for solid patterns. For convenience in working and pouring, the entire mould is made in the foundry floor or in a bed of sand above floor level. Moulding box is not necessary and the upper surface of the mould is open to air. After proper levelling the pattern is pressed in the sand bed for making mould. Pouring basin is made at one end of the mould, and the overflow channel cut at the exact height from the bottom face of the mould for giving necessary thickness.

Bedded-in method
In this method, the pattern is hammered down or pressed to bed it into the sand of the foundry floor or in a drag filled partially with sand to form the mould cavity. The sand should be rammed close to the pattern sand; a cope is placed over the pattern. The cope is rammed up, runners and risers are cut and the cope box is lifted. Now the pattern is withdrawn, the surfaces of drag and cope replaced in its correct position for completing the mould.

Turn-over method

One pattern-halfis placed with its flat side on a moulding board, a drag is rammed and rolled over. The other pattern half and a cope box are placed in position. After ramming the cope is lifted off and the two pattern halves shaken and withdrawn. Now the cope is replaced on the drag for assembling the mould.