Types of Patterns & Moulds

Use of a mould, either permanent or temporary, is a must for every casting process. A mould is nothing but a 'negative' of the desired shape of the component. As the mould is filled by molten metal, it forms the 'positive' shape of the desired component after solidification. Processes differ in the number of stages that are required to produce the final casting. Die casting is considered to be the easiest technique as it requires less number of stages to form complete casting. A permanent mould is used in die casting to produce the final casting. Other processes, like sand mould and shell casting, use a expendable (temporary) mould. These expendable moulds are made by using a permanent pattern or die. The temporary moulds used in Investment casting and lost foam casting techniques are generally build around a temporary pattern. In order to make them reusable, patterns are generally made using a permanent mould or die. The following table represents a summary of the patterns and moulds typically used in various kind of casting processes.

 

Die casting	Sand casting	Shell casting	Investment Casting and lost foam casting
Permanent Die-ve shape	Permanent pattern +ve shape	Permanent pattern +ve shape	Permanent die(optional) -ve shape
			Temporary pattern +ve shape
	Temporary mould -ve shape	Temporary mould -ve shape	Temporary mould -ve shape
Final Casting +ve shape	Final Casting +ve shape	Final Casting +ve shape	Final Casting +ve shape
Types of Patterns and Moulds Used in the Major Casting Techniques