Injection stretch blow moulding
Robust, high clarity packaging popular in many market sectors
Centred on our Madrox site in Poland, the addition of injection stretch blow moulding (ISBM) technology was largely prompted by growing customer demand for lightweight, glass clear containers.
This process also guarantees consistently accurate neck finish profiles. The majority of our output is in the form of screw threaded bottles, but we can also produce preforms for conversion by our customers.
This process has two main variants – single-stage and two-stage. In both variants the plastic is first injection moulded into a preform, which defines the neck finish of the final bottle. The single stage process involves producing a preform and stretch blowing the bottle in the same machine.
These preforms are heated over their glass transition temperature, then blown using high pressure air into bottles using special blow moulds. At the same time the preform is stretched with a core rod to enhance its rigidity. Robinson offers both single-stage and two-stage options, predominantly using PET material but also PP where appropriate.
The key advantages of ISBM are:
- Flexibility to make smaller runs
- Preform wall thickness can be varied to allow blowing of rectangular and non-round shapes
- Good O2 and CO2 barrier properties for PET bottles
- Reduced weight containers
- Dimensionally accurate neck finishes
- High breakage resistance