PETpla.net Insider 12 / 2019

PREFORM PRODUCTION PET planet Insider Vol. 20 No. 12/19 www.petpla.net 32 Very high cavitation tooling Raising the standards Sipa is a well-known producer of PET preform injection moulding systems with very high outputs. The Italian company designs and produces moulds and hot runner systems that fit in Sipa machines and machinery of other major producers. The company recently con- ceived, designed, built and delivered a preform mould hot runner system with 192 cavities for one of the world’s leading PET container makers, based in North America. Creating a hot runner system that consistently and reliably enables such large numbers of cavities to be filled identically, at high speed, without excessive force, is a serious design and engineering challenge. Key to Sipa’s successful range of high-cavity machines is its Xflow melt distribution system, which is now available for use on GEN3 and GEN4 (third and fourth generation) XForm 250, 350 and 500 high-performance injection moulding machines. Improved melt distribution Xflow incorporates a hot runner manifold design that provides industry- leading levels of balance of melt distri- bution, along with the lowest pressure drop ever measured, states Sipa. The maintenance interval – five million cycles – is able to be so long because the system’s performance characteris- tics impose very low levels of wear and tear and Xflow is designed so that maintenance is easy to carry out, when it is required. This technology enables Sipa to create very high-cavitation systems without having to compromise on bal- ance, pressure losses or the formation of acetaldehyde due to polymer deg- radation. Xflow can also be applied to moulds with more modest levels of cavi- tation, with similar benefits to operators. Advanced concepts in polymer rheology Sipa introduced Xflow technology in its hot runner systems for over five years in 2013. The company says that the solution applies the most advanced concepts of polymer fluid dynamics to hot runner engineer- ing. By taking melt rheology aspects into account, it can obtain balancing results beyond the capability of tradi- tional systems. When it first arrived on the market, Xflow halved the imbal- ance in melt flow compared with Sipa’s first generation of hot runners. Taking account of PET’s rheologi- cal properties all along the many flow paths to the individual cavities is criti- cal, because PET preform walls have become so thin. Hot runners’ energy consumption has to be minimised, so that the injection unit can push the molten polymer as quickly and effi- ciently as possible into all the cavities. “Use of rheological balanc- ing translates into minimum energy demand and a very low pressure drop,” says Andrea Cavalet – Global Engineering Manager Injection Moulds & Hot Runners. “Xflow can be applied to any application, to provide the best solution for high-speed injec- tion of critical preforms.” Breaking down mould design barriers Sipa says that it is using its advanced expertise in hot runners is about more than just getting higher and higher cavity numbers; it is also creating new preform moulds that exploit the potential of existing injec- tion moulding machines well beyond current limits. Its GEN4 hot runner design con- cept overcomes traditional limitations on cavity layouts. Most PET preform moulds have standard configurations of 72, 96, 128 or 144 cavities. Preform producers can now use moulds with non-standard cavity layouts to sub- stantially raise output, without putting extra stress on their machines. World’s first 180-cavity preform mould The concept allowed Sipa to engi- neer and manufacture the first 180- cavity preform tooling in the world. It runs on a regular 500 t press, which would usually be able to run with moulds with no more than 144 cavi- ties. Sipa’s technology has provided its customer the potential to raise pro- ductivity by 25 per cent. “It’s not the biggest preform mould in the world but the filling characteris- tics are excellent,” says Cavalet. “The customer isn’t gaining quantity at the price of quality; there are no penalties in cycle time or weight distribution.” Maximising machine potential Sipa says that it achieved this improvement without compromising mould robustness. Features like the SmartLock stack design, which deliv- ers improved component life; XGuid- ance, which is designed to guaran- PREFORM Special