PETpla.net Insider 06 / 2011

Vol.6 PET planet print PREFORM PRODUCTION 10 PET planet insider Vol. 12 No. 06/11 www.petpla.net Parting Line Crease Part 21 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 21 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: A small radial fold appears in the preform body at the parting line between the neck insert and the cavity. Cause: The preform body is deformed during the initial mould open- ing sequence (core side separating from cavity side) due to the preform not releasing freely from the cavity. Solutions: 1. Check water cooling temperature. This should be 7 – 10ºC (45 - 50ºF) for optimum cooling. 2. Check water cooling flow to mould. This should be at the mould manufacturer’s rating (for a given preform size and cavitation). 3. 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 increase shrinkage for better release. 4. Check that the hold (packing) time isn’t excessive for the preform being moulded. Reduce as necessary to minimize swelling. 5. Check that the hold (packing) pressure isn’t too high to cause excessive swelling, especially in the last zone. Reduce as necessary. 6. Check that transition position is set to about 13% of shotsize + cushion. Lower values may result in overfilling. 7. Check all temperature readings and correct if necessary. PET resin should be melted at about 280ºC (536ºF) +/- 10ºC (18ºF).