Plastics 101 : Manufactoring methods - Injection Molding and Blow molding

1. Plastic Manufacturing Methods:

1-1. Injection Molding:

• Process: molten plastic is pushed into a hollow mold, cooled, and popped out. 

• Final product: toys, bottle caps, phone cases, or LEGO bricks.

This process injects molten plastic into a mold under high pressure:

• Step 1: plastic pellets are fed into the machine.

• Step 2: the pellets are melted in a heating barrel.

• Step 3: molten plastic is injected under pressure into a closed mold.

• Step 4: after cooling off, the finished part is ejected.

The below diagram shows the whole process:

1-2. Blow Molding:

• Process: a plastic tube is inflated like a balloon inside a mold. 

• Final product: bottles, jugs, containers, or hollow toys.

This process creates hollow objects by inflating a plastic tube inside a mold:

• Step 1: plastic is melted in an extruder.

• Step 2: a hollow tube (parison) is formed through a die.

• Step 3: the parison is placed in a mold and air is blown in, expanding it towards the mold walls.

• Step 4: after cooling off, the hollow part is ejected.

The below diagram shows the whole process: