PETpla.net Insider 11 / 2011

PREFORM PRODUCTION 15 PET planet insider Vol. 12 moulded. Increase as necessary to optimize part weight. 6. Check water cooling temperature. This should be 7 – 10ºC (45 – 50ºF) for optimum cooling. 7. Check water cooling flow to mould. This should be at the mould manufac- turers rating (for a given preform size and cavitation). 8. Check that the valve stems are open- ing properly. A partially open valve stem may restrict melt flow. 9. Check to ensure that the valve gate compressed air pressure is sufficient to open the valve stems properly. Typical pres- sures are in the range of 8 – 12bar (120 – 145psi). 10. Check that the valve gate open timing is adjusted properly. This is typically 0sec. Minimize to allow more time to open. 11. Check all temperature readings and adjust as necessary. PET resin should be melted at about 280ºC (536ºF) +/- 10ºC (18ºF). 12. Check that transition position is set to about 13% of shotsize + cush- ion. Higher values may result in under-filling. 13. Check that the decom- pression (pullback) time and position is not exces- sive. This should be set as low as possible to minimize the risk of melt backflow into the nozzle tips, yet enough to elimi- nate drooling into the cavity from excess melt pressure. Typical settings for valve gated moulds are: Time = 0 – 1sec; Distance = 0 – 10mm. Non-valve gated moulds may require higher values to minimize gate stringing. Are your standard PET preform molds making you as much money as they should? Ask how MPET with iFlow technology improves production and achieves greater quality results. Innovation doesn’t happen in isolation. It happens when blue-sky thinking meets down to earth know- how and exceptional supply chain execution. The sort of innovation that Mold-Masters is known for, now applied to PET tooling for industry-leading results. Introducing MPET – the new PET preform tooling solution designed for the standards of tomorrow. Mold-Masters and theMold-Masters logoare trademarks ofMold-Masters (2007) Limited. ©2011Mold-Masters (2007) Limited.All rights reserved. Think about it. moldmasters.com/thinkaboutit [email protected] 14. Ensure the mould neck insert and lock ring vents are clean. This will minimize gas entrapment at the neck finish. 15. Check to ensure that no moisture exists on the moulding surfaces, either from water leaks or condensation. This may obstruct normal melt flow and cause filling problems. The environmental dewpoint should be below the chilled water temperature to eliminate the risk of condensation. 16. Check hardware for worn, damaged or failed components, specifically the valve stems, valve stem seals, nozzle tips, shut-off nozzle plunger alignment, shooting pot motion, extruder screw check valve leakage (single-stage machine only), and clogged core / cavity cooling channels. www.petpla.net