This method is less common in practice but has a number of distinct advantages. In this case the parison is injection moulded onto a core using the normal moulding process equipment described earliler. However, before the moulding has a chance to solidify the mould opens and the core with the plastic parison on it is transferred to the blow mould. When this mould closes the core provides its secondary function of inflating the parison to fill the mould. The advantages of this method include the fact that no trimming is necessary since the mould completely surrounds the parison and this produce no flash. This also means that additional intricate detail can be produced in the bottle neck area. Finally, whereas extrusion blow moulding is limited to materials which have sufficient melt strength to sustain their own weight during parison formation, injection blow moulding can be used wiath almost all thermoplastics.

The main developments in blow moulding are in relation to improved heat transfer from the shaped parison, and a considerable amount of research has been devoted to cooling the inside of the moulding by injecting cold fluids. This has demonstrated that considerable improvements in the production rates can be achieved by these methods.