Blow moulding

Process:   An extruded tube is pinched at one end and expanded with hot air to fill the cavity of a two part metal mould.  Once cooled the piece is removed from the mould and the pinch point is trimmed.

Introduced:   1881 for use with cellulose nitrate.

Plastics:   Commonly high density polyethylene and polyethylene terephthalate.

Marks:   A pinch line.

Tooling cost:   Relatively high.

Production volume:   High.

Uses:   Hollow articles, usually with openings of smaller diameter than the body, such as bottles or containers.