Stretch blow moulding procedure, stretch blow moulding, injection stretch blow moulding
Stretch blow moulding or injection stretch blow moulding is a procedure from manufacturing technology for the manufacture of hollow containers made from thermoplastic plastics, and is suitable for the economical manufacture of PET bottles.
Unlike extrusion blow moulding, the hollow container is not manufactured using a thermoplastic tube that is pulled lengthways. The hollow containers are stretched in the longitudinal direction and also at the circumference, based on the biaxial alignment of the macro-molecules in the plastic. The packages are characterised by having a sprue on the base of the container.
The procedure is usually in two stages. Firstly the preforms are brought to a suitable processing temperature. In the second step, the actual stretch blow moulding, the preform is transferred to the water-cooled blow mould, which is then closed. The preform is stretched lengthways using a horizontal bar, which is introduced from above, and then given its final shape using pressure.
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