PETpla.net Insider 10 / 2012

Vol.6 PET planet print PREFORM PRODUCTION 24 PET planet insider Vol. 13 No. 10/12 www.petpla.net The rapid guide to perfect preforms - part 33 Wall thickness variation 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. It has been written for the people on the floor of injection moulding companies to support their daily work in making the best preforms possible. The product of two industry experts, Rick Unter- lander and Ottmar Brandau, it gives concrete advice on 35 of the most common problems in preform manufacture, most illustrated by pic- tures. From high AA levels to wavy bodies pro- cessors can find help when they need it. Read chapter 33 of the guide. Symptom The range in preform wall thickness as measured around its circumference is above 0.15mm (0.006”). This is usually measured on the cylindrical body section of the preform near the end cap dome. Cause The mould core was not centered in the mould cavity during the moulding process. 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 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 Solutions 1. Check injection time isn’t too low (injection rate too fast to cause core deflection) and adjust if necessary. Injection rate should be about 10 – 12g/sec/cavity. 2. Check to ensure injection pressure isn’t too high, especially when peak- ing at the transition point. 3. Check to ensure hold (packing) pres- sure isn’t too high, especially near the beginning of hold time. 4. Check hardware for worn, dam- aged or failed components, specifi- cally the mould cores (bent), leader pins and bushings, mould level, core cooling tubes, neck ring tapers, cavity tapers, and lock ring tapers.. www.petpla.net PET planet print vol.6 The Rapid Guide to Perfect Preforms machine no./name Order y our co py no w! www.petpla .net | i nfo@hbmedia.net