PETpla.net Insider 10 / 2018

MOULD MAKING PET planet Insider Vol. 19 No. 10/18 www.petpla.net 14 Keeping balance with ultra-high-cavitation hot runner systems 192 cavities evenly filled Mould making has always been a brew of engineering expertise and artistry. That is especially so in the world of PET preforms, where customers want something that can be turned into a product – the bottle – that combines beauty and strength. Can this observation be extended to hot runner systems? After all, hot runner design is very much a case of form following function and obtaining that functionality is very much in the hands of the engineers. Hot runner systems for preform moulds holding close to 200 cavi- ties are delicate to handle. At high speed, many cavities have to be filled identically, without excessive force. Underlining its engineering exper- tise, the Italian company Sipa has just conceived, designed, built and delivered a preform mould with 192 cavities to one of the world’s leading PET container makers, based in North America. Sipa’s XFlow melt distribution system, which is now available for use on GEN 3 (third generation) XForm 350 and 500 high-performance injec- tion moulding machines, incorporates an innovative hot runner manifold design that has been engineered to provide an excellent balance of melt distribution. As Sipa states, it exhibits the lowest pressure drop ever meas- ured. That is one reason why the maintenance interval can be extended, since wear and tear is reduced. An additional benefit, according to the company, is that any maintenance required is easy to carry out. A tooling and hot runners R&D team member from Sipa explains “XFlow technology, which is unique to Sipa, allows us to create very high- cavitation systems without having to compromise on balance, pressure losses, and the formation of acetal- dehyde due to polymer degradation. It goes without saying that XFlow can also be applied to moulds with more modest levels of cavitation with equally impressive results. XFlow is extremely efficient and it is scalable according to customer needs.” Everything in the melt flow Over the course of the last five years, Sipa has made great efforts in hot runner technology. The first gen- eration of their hot runners depended on a purely mechanical technology for balancing melt flow. Then in 2013, the company introduced a new generation of hot runners, which marked a turn- ing point in the approach to flow bal- ance. This is when XFlow first came onto the scene. The XFlow solution applies advanced concepts of polymer fluid dynamics to hot runner engineer- ing. By taking melt rheology aspects into account, it became possible to obtain balancing results quite beyond those of traditional systems, states Sipa, halving the imbalance in melt flow compared with the first generation. In a next step, third generation hot runner systems - introduced soon after the second generation – are claimed to incorporate a fur- ther evolved version of XFlow that benefits from a total overhaul of the cylinder units, valve guides and noz- zles. “When we design XFlow hot runner systems, we now take fully into consideration the rheological properties all along the many flow paths to the individual cavities,” says a Sipa team spokesperson. “This is really important, given that these days we are increasingly working on projects where preform walls are thinner than ever before. This means that it is critical for the hot runners to consume as little energy as pos- sible so that the injection unit can push the molten polymer as quickly and efficiently as possible into all the cavities.” And continues “Use of rheological rather than mechanical balancing translates into minimum energy demand and a very low pres- sure drop. XFlow can be applied to any application to provide the best solution for high-speed injec- tion of critical preforms. Without XFlow, such results are impossible to achieve.” www.sipa.it MOULD special