Risers:
Riser Design : A riser or a feeder head is a passage of sand made in the cope to permit the molten metal to rise above the highest point in the casting after the mould cavity is filled up. Risers serve a dual function. They compensate for solidification shrinkage which is a very common casting defect and are a heaf source so that they freeze last and promote directional solidification.
Types of Risers : There are two types risers :Top or open risers and side or blind risers.
Riser shape and Size : The metal in the riser should remain in the molten state for a longer time than in the mould cavity.
It means a heaf looses in riser should therefore be kept to a minimum. It means a riser most freeze more slowly than the casting. Those there shape should be such as to give volume-to-surface-area ratio a maximum value. This ratio is maximum for a sphere. Therefore this is the ideal shape of a riser.
As regards the height of the riser, it must be fall enough to ensure that any pipe formed in it does not penetrate the casting.
Melting Furnaces for Ferrous Metals : Various types of melting furnaces are used in different foundary shops, depending upon the quality of metal to be melted of a time and the nature of work that is carried out in the shop. Converters, open hearth and electric furnaces for melting iron and steel are the example of some melting furnaces.