Permanent mold castings are the need of hour because of their cost effectiveness. Since you can cast it into any shape it has become first choice for parts being made with sand castings.
In this method a metal casting die is used along with sand cores. It is done like this – the metal mold is preheated before production to increase its temperature to usable level. The mold built of two halves is closed Molten metal is then filled in. after it solidifies due to cooling the mold is opened and casting ejected. The mold is closed again filled with special sand and process repeated.
Permanent mold castings though not as flexible as sand castings, help in reducing cost to a great extent in mass production.
In another method of permanent mold castings, instead of using gravity to help in pouring metal into the mold a low pressure of upto 1 atmosphere of gas is put on molten metal. This gas pressure ensures that the mold is filled completely with metal and there is no gap. It leads to making good quality castings at a low price.
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