PETpla.net Insider 07+08 / 2011

Vol.6 PET planet print PREFORM PRODUCTION 14 PET planet insider Vol. 12 No. 07+08/11 www.petpla.net Parting Line Deformation The rapid guide to perfect preforms - part 22 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 proposi- tion 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 support their daily work in making the best preforms pos- sible. 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 22 of the guide. Symptom: A wavy or slightly wrinkled section near the neck insert/cavity parting line. Cause: The shrinkage rate on the exterior sur- face of the preform between the neck inserts and the cavity is significantly different. This is amplified when the preform remains on the core (out of the cavity) for a long time period. Table of Contents i........................ About the Authors ii.................................Introduction chapter 1.............................. AA Level High 2........................ Accordion Preform 3....................... Air hooks / Streaks 4............................... Black Specks 5...................................... Bubbles 6..................................Burn Marks 7...........................Colour Streaking ................................... /Peeling 8..................................Crystallinity 9.................................Drool Marks 10.......................................... Flash 11......................... Gate Depressions 12............................... Gate Peeling 13..................Gate Voids / Pin Holes 14......................... Internal Gate Sink 15................................Internal Sinks 16........................................ IV Loss Solutions: 1. Check water cooling temperature. This should be 7 – 10ºC (45 - 50ºF) for optimum cooling. 2. Check water cooling flow to mould and robot receptacles. This should be at the mould manufacturers rating (for a given preform size and cavitation). 3. Check that the cooling time is suffi- cient for the preform being moulded. This typically ranges from about 1 to 3sec depending upon the preform wall thickness. Add time if neces- sary to improve solidification and increase shrinkage for better release. 4. Ensure preforms are ejected from the cores and transferred into the robot cooling receptacles as soon as possi- ble. Minimize any delays and ensure robot entry speeds are maximized. 17............................ Long Gate Nub 18...............................Milky Preform 19............................ Moisture Marks 20................Neck Finish out of Round 21....................... Parting Line Crease 22.................Parting Line Deformation 23......................... Preform Yellowing 24.................................. Short Shots 25.......................................... Sinks 26......................................... Splay 27........................... Stretched Necks 28..................................... Stringing 29......................... Surface Blemishes 30......................... Thread Flow Lines 31...............TSS (Top Sealing Surface) ......................................... Sink 32.......................................Unmelts 33.................Wall Thickness Variation 34.................................Wavy Body 35.................................. Weld Lines