PETpla.net Insider 04 / 2015

PREFORM PRODUCTION 38 PET planet insider Vol. 16 No. 04/15 www.petpla.net Injection tooling, part 19 Practical Guide to Injection Molding of Preforms PETplanet Insider is publishing extracts from successive chapters of Ottmar Brandau’s “Bottles, Preforms and Clo- sures”, which was published by hbmedia. A newly revised version is reissued under the Elsevier imprint. Over the years, certain standards have developed that most reputable toolmakers adhere to. The standards include the choice of materials, their hardness, minimum wall thickness sections in cores and cavities, and the design of venting channels. Here is a quick overview of what most “good” tools should feature to guarantee trouble-free operation:  Hardness of neck inserts of ~54 HRc  Hardness of cores and cavities of ~50 HRc  Core wall thickness of 3 ± 0.02 mm  All tooling plates made from stainless steel with a hardness of ~30 HRc  Fully balanced hot runner with plate hardness of ~45 HRc  Bubbler tubes (the pipes inside the injection cores) made from stain- less steel  There are of course a great many differences between the tools of different manufacturers, but if these standards are met, there is a much greater chance that the tool will not fail in production. There are other differences as well that users should be aware of (Figs 3.21 and 3.22): Figure 3.21 Spiral water cooling chan- nels have become more popular over the years. (Picture courtesy of MHT-AG). Figure 3.22 Cavity with cascading-style cooling.