A blow moulding machine makes hollow plastic parts such as bottles, cans, drums and tanks. A tube or preform of hot plastic is closed inside a mould and air is blown in, pressing the plastic against the mould walls. Extrusion blow moulding suits HDPE and PP containers; stretch blow moulding makes PET bottles from injection-moulded preforms.
Quick facts
- Main types
- Extrusion blow moulding, PET stretch blow moulding, injection blow moulding
- Materials
- HDPE, PP, PET, PVC
- Part size
- From a few ml to drums of over 200 litres
- Cavities
- One to many
- Air
- High-pressure compressed air (higher for PET)
- Typical parts
- Bottles, jerry cans, drums, tanks, ducts
Extrusion or stretch blow moulding?
| Extrusion blow | PET stretch blow | |
|---|---|---|
| Starts from | Hot tube (parison) from an extruder | Injection-moulded preform |
| Materials | HDPE, PP, PVC | PET |
| Typical products | Cans, drums, oil bottles, tanks | Water, soft drink and oil bottles |
| Handles | Yes, moulded in | Separate, if any |
Good to know
- Mould cost is lower than for injection moulds of the same size
- Wall thickness control (parison programming) decides weight and strength
- Trimming of flash is needed on extrusion-blown parts
- Leak testing is usual for containers
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Questions
- Is blow moulding the same as injection moulding?
- No. Injection moulding makes solid parts; blow moulding makes hollow parts by blowing air into hot plastic.
- Which plastic for chemical cans?
- HDPE is the usual choice for chemical and oil containers.
- Can one machine make different bottle sizes?
- Yes, by changing the mould, within the machine's size and clamp limits.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 29 October 2026.