Blow moulding a shape is a common industrial process. The example shown below is of the production of a plastic bottle. The plastics normally used in this process are: polythene,PVC and polypropylene.
The process is similar to injection moulding and extrusion.
1. The plastic is fed in granular form into a 'hopper' that stores it.

2. A large thread is turned by a motor which feeds the granules through a heated section.

3. In this heated section the granules melt and become a liquid and the liquid is fed into a mould.

4. Air is forced into the mould which forces the plastic to the sides, giving the shape of the bottle.

5.  The mould is then cooled and is removed.