6 Main Differences between Injection and Blow Molding

Blow and injection molding are processes used to manufacture plastic parts. Injection molding is used to manufacture solid parts, whereas blow molding produces hollow parts.Thermoplastic materials are used in both the processes.

Main Differences between Injection and Blow Molding

The following are the major differences between the processes used for plastic product manufacturing:

S.N.	Injection Molding	Blow Molding
1	Used to manufacture solid parts	Used to manufacture hollow parts
2	Thermoplastic material is injected into a mold	A thermoplastic sheet is pushed into a mold using high speed air
3	Thickness of part is pre-determined and is dependent on the construction of the mold	Thickness of part is dependent on the amount the material stretches. Hence, thickness will differ from place to place
4	Time spent making the mold – 90% of total manufacturing time	Time spent making the mold – 50% of total manufacturing time
5	During the manufacturing process, no air is allowed inside the mold.	This process depends on air to form the product
6	Manufacturing Process: During the injection molding process, the raw material is injected into a mold. The plastic is allowed to cool down and set in a particular shape. Once the part has been formed, it is extracted from the mold.	Manufacturing Process: A mold that is split open from the middle is used for blow molding. A plastic mold is closed on a preform or parison (depending on the type of blow molding process used). Air is then blown into the mold, which causes the preform or parison to inflate and touch the walls of the mold. Once the plastic cools and takes the right shape, the mold is opened.

Injection molding and blow molding are used to fabricate plastic products with different physical properties. The process befitting your product and application should be selected accordingly.