PETpla.net Insider 05 / 2011

Vol.6 PET planet print PREFORM PRODUCTION 18 PET planet insider Vol. 12 No. 05/11 www.petpla.net Neck Finish out of Round Part 20 of the “Rapid Guide to Perfect Preforms” * *by Rick Unterlander and Ottmar Brandau Troubleshooting guides have suffered in the past from being locked away in offices and not being available to the people that actually need them. Considering the high cost of machine and tools high scrap rates can be a costly prop- osition eating away at already tight margins. PETplanet’s “Rapid Guide to Perfect Preforms” takes a different approach. Bound in laminated paper that is easy to clean off, the small format of the book of 108mm by 151mm (4.25” by 6”) allows easy storage in back pockets or tool boxes. It has been written for the people on the floor of injection moulding companies to sup- port their daily work in making the best pre- forms possible. The product of two industry experts, Rick Unterlander and Ottmar Brandau, it gives concrete advice on 35 of the most common problems in preform manufacture, most illustrated by pictures. From high AA levels to wavy bodies processors can find help when they need it. Read chapter 20 of the guide. fax: +49 (0) 6221-65108-28 info@hbmedia.net www.petpla.net Order your copy now! PET planet print vol.6 The Rapid Guide to Perfect Preforms machine no./name Symptom: The range in neck finish ID as measured around its internal cir- cumference is above 0.25mm (0.010”). Cause: Poor formation or external deformation of the neck finish. Solutions: 1. Check water cooling temperature. This should be 7 – 10ºC (45 – 50ºF) for optimum cooling. 2. Check water cooling flow to mould, especially the neck inserts and cores. This should be at the mould manufacturers rating (for a given preform size and cavitation). 3. Check to ensure hold (packing) pressure isn’t too low, espe- cially near the beginning of hold time. Adjust higher if neces- sary to fully fill out the preform. 4. Check that the hold (packing) time isn’t too little for the pre- form being moulded. Increase as necessary to optimize part weight. 5. Check that the cooling time is sufficient for the preform being moulded. This typically ranges from about 1 to 3sec depending upon the preform wall thickness. Add time if nec- essary to improve solidification. 6. Maximize the cooling time of the robot. This should not be increased beyond the cycle time of the machine. 7. Check all temperature readings and adjust as necessary. PET resin should be melted at about 280ºC (536ºF) +/- 10ºC (18ºF).