In order to understand what happens in a foundry, it is important to first know what is casting process. Generally, the steps involved in the casting process are
7. Fettling and
The shape of the final casting depends upon the mould it’s poured into; therefore, moulds are meticulously shaped using a pattern – a metal replica or wood of the object that needs to be cast. Silica is the most common mould material; however, they can be from several materials based on the method employed and casting metal used.
A melting furnace gets charged with metal and is subject to heating above the melting point of the metal. The molten metal, once it reaches a particular pouring temperature, is tapped from the melting furnace via a spout into a steel pouring ladle that is refractory lined. Next, impurities or slag are removed by a process called skimming off the surface of the hot molten metal. The molten metal is then poured into a mould cavity with the ladle tipped for the purpose. One of the most potential damages to the foundry can occur because of charging, and the mistakes can often prove costly.
The mould is allowed to cool; it holds this metal in shape as it solidifies. The casting is broken out of the mould (or ejected) and cleaned. This is finished with the help of a process known as fettling that trims the excess metal out of the casting and caters to the precise dimensions to form the finished product.
Based on the casting specs, fettling can be simple and quick, or intricately detailed work. Then the finished castings are subject to thorough inspection by the foundry before shipping.
Foundries do not simply make raw castings; they comprise several operations that often integrate tool building, part design, machining, prototyping, assembly, machining and after–sales support.