PET preform mould acceptance checklist: what to check before shipment
The cheapest time to find a problem with a preform mould is before it leaves the maker's factory. Once it is on a ship, every fix costs weeks. Use this checklist for the factory acceptance test, whether you attend in person, by video or through your representative.
Agree the acceptance criteria first
Write the criteria into the order: preform drawing and tolerances, target cycle time, the machine the trial runs on and how many shots will be checked. Acceptance then means comparing results with numbers both sides signed, not arguing about opinions.
Preforms: check every cavity
- Weight of each cavity against the drawing tolerance. On our 64 cavity project the tolerance was 14 g ±0.2 g.
- Neck finish dimensions: thread, support ring and sealing surface, measured with gauges for the finish.
- Overall length and body diameter.
- Wall thickness around the circumference, which shows whether the core is centred.
- Visual checks: gate stringing or white crystallinity, haze, bubbles, black specks and short shots.
Keep a full shot with cavity numbers marked. If one cavity is out, you know exactly which core, cavity or nozzle to look at.
The trial run
- Run at the agreed cycle time until the process is stable, not just a few shots.
- Record the main settings: melt temperature, hot runner zone temperatures, injection and holding pressure, cooling water temperature.
- Get a video of the mould running on the machine.
Hot runner and cooling
- Every heater zone reaches and holds its set temperature.
- On a needle-valve system, every valve pin opens and closes.
- Every cooling circuit has flow and there are no water leaks.
Documents and spare parts
- Mould assembly drawings and the cooling water diagram.
- Hot runner wiring diagram with zone numbers.
- Trial report with settings and measurement results.
- Spare parts list, with recommended wear parts such as heaters, thermocouples and seals.
- Maintenance points for your team.
Packing for sea freight
Moulding surfaces should be cleaned and protected against rust, cooling channels drained and blown dry, and the mould fixed in a strong wooden case. A sea voyage in humid air can do real damage to an unprotected mould.