PET Preform Production
PET preform presses are injection moulding machines specifically designed to produce PET preforms — the tube-shaped blanks that are subsequently stretch blow moulded into bottles. Preform production is a specialised process requiring precise temperature control, resin handling, and mould technology. Used preform presses represent significant capital equipment that can provide years of production when properly maintained.
Key Components of a Preform Press
- Injection unit — melts and injects PET resin into the mould cavities
- Clamping unit — holds the mould closed under high pressure during injection
- Mould (tool) — multi-cavity mould producing 16 to 144+ preforms per cycle
- Hot runner system — distributes molten PET from the injection unit to each mould cavity
- Cooling system — rapidly cools preforms to maintain clarity and dimensional accuracy
- Robot/take-out system — removes preforms from the mould and places them on a cooling conveyor
Critical Inspection Points
- Injection screw and barrel — check for wear, particularly on the screw flights and barrel bore
- Mould condition — inspect cavity surfaces, core pins, neck ring tooling, and hot runner nozzles
- Tie bar condition — check for wear, scoring, or flex that indicates structural stress
- Clamp tonnage — verify the machine delivers rated clamping force
- Cycle time — measure actual vs specified cycle time as an indicator of overall machine condition
- Resin drying system — PET requires precise moisture removal before processing
- Cooling water system — consistent cooling is critical for preform quality
Common Issues
Problems to Watch For
- Worn injection screws reducing plasticising efficiency and preform quality
- Mould cavity wear causing dimensional variations in preforms
- Hot runner system blockages or leaks increasing scrap rates
- Inadequate resin drying causing haze or AA (acetaldehyde) issues in preforms
- Control system obsolescence — older presses may use discontinued PLC platforms
Frequently asked questions
Should I make or buy PET preforms?
Making preforms in-house requires significant capital investment and technical expertise. It is economically justified at high volumes (typically above 50-100 million preforms per year). Smaller operations generally benefit from purchasing preforms from specialised manufacturers.
How many cavities should a preform mould have?
Mould cavity count depends on your production volume and preform weight. Common configurations range from 16 cavities for small operations to 96-144 cavities for high-volume production. Higher cavity counts reduce per-preform cost but increase mould and press investment.
What PET resin grades can used presses handle?
Most PET preform presses can process standard bottle-grade PET resin. Specialised resins (barrier PET, recycled PET blends) may require specific screw designs or processing parameter adjustments. Verify compatibility with your target resin before purchasing.