Advantages: Very high volumes are produced. Little restriction on bottle design. Preforms can be sold as a completed item for a third party to blow Disadvantages: High capital cost. Floor space required is high. Only suits round bottles
In the single-stage process both preform manufacture and bottle blowing are performed in the same machine. The older 4 station method of Injection, Reheat, Stretch blow and Ejection is more costly than the 3 station machine which eliminates the reheat stage and uses latent heat in the preform thus saving costs of energy to reheat and 25% reduction in tooling. The process explained: Imagine the molecules are small round balls, when together they have large air gaps and small surface contact, by first stretching the molecules vertically then blowing to stretch horizontally the biaxial stretching makes the molecules a cross shape. These "crosses" fit together leaving little space as more surface are is contacted thus making the material less porous and increasing barrier strength against permeation. This process also increases the strength to be ideal for filling with carbonated drinks.
Advantages: Highly suitable for low volumes and short runs. As the preform is not released during the entire process the preform wall thickness can be shaped to allow even wall thickness when blowing rectangular and non round shapes.
Disadvantages: Restrictions on bottle design. Only a champagne base can be made for carbonated bottles.
