SIPA has engineering expertise that few can match in the design and manufacture of PET preform injection molding systems with very high outputs. It applies that expertise not only to injection molding machines but also to the molds and hot runner systems that fit in them. As an illustration of this prowess, SIPA has conceived, designed, built and delivered a preform mold 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 so many cavities to be filled identically, at high speed, without excessive force, is a task that extremely few companies are capable of handling. SIPA can do it, thanks largely to its Xflow melt distribution system, which is now available for use on GEN3 and GEN4 (third and fourth generation) XFORM 350 and 500 high-performance injection molding machines.
MUCH IMPROVED MELT DISTRIBUTION
Xflow incorporates an innovative hot runner manifold design that provides the best balance of melt distribution in the industry. In fact, it exhibits the lowest pressure drop ever measured. That is one reason why the maintenance interval – five million cycles – is so long since wear and tear are considerably reduced. Furthermore, any maintenance that is required is easy to carry out.
This technology, unique to SIPA, allows the company to create very high-cavitation systems without having to compromise on balance, pressure losses, and the formation of acetaldehyde due to polymer degradation. Xflow can also be applied to molds with more modest levels of cavitation with equally impressive results.
ADVANCED CONCEPTS IN POLYMER RHEOLOGY
SIPA has been implementing Xflow technology in its hot runner systems for over five years. Its introduction in 2013 marked a decisive turning point in the approach to flow balance in hot runner systems. The Xflow solution applies the most advanced concepts of polymer fluid dynamics to hot runner engineering. By taking melt rheology aspects into account, it is possible to obtain balancing results quite beyond those of traditional systems. When it came onto the market, Xflow halved the imbalance in melt flow compared with SIPA’s first generation of hot runners.
When designing Xflow hot runner systems, SIPA engineers take full account of PET’s rheological properties all along the many flow paths to the individual cavities. This is critical, given how thin PET preform walls now are. Hot runners have to consume as little energy as possible so that the injection unit can push the molten polymer as quickly and efficiently as possible into all the cavities.
“Xflow is, without doubt, the best solution in this respect,” says Andrea Cavalet – Global Engineering Manager Injection Molds & Hot Runners. “Use of rheological balancing translates into minimum energy demand and a very low-pressure drop. Xflow can be applied to any application to provide the best solution for high-speed injection of critical preforms.”
BREAKING DOWN MOLD DESIGN BARRIERS
SIPA is using its advanced expertise in hot runners to create new preform molds that exploit the potential of existing injection molding machines well beyond current limits. But it’s more than just getting the most cavities in a mold.
SIPA’s GEN4 hot runner design concept overcomes traditional limitations on cavity lay-outs. Most PET preform molds have standard configurations, with 72, 96, 128 or 144 cavities. But now, preform producers can use molds with non-standard cavity layouts to substantially raise the output of their machines without putting extra stress on them.
WORLD’S FIRST 180-CAVITY PREFORM MOLD
Indeed, the concept allowed SIPA to engineer and manufacture the first 180-cavity preform tooling in the world. This mold runs on a regular 500-tonne press. A machine of that size would normally be able to run with molds having no more than 144 cavities, so SIPA has provided its customer with the potential to raise productivity by a massive 25 percent.
“It’s not the biggest preform mold in the world, but the filling characteristics are excellent, so the customer isn’t gaining quantity at the price of quality,” says Cavalet. “There are no penalties to pay in terms of cycle time and weight distribution.”
MAXIMIZING MACHINE POTENTIAL
SIPA achieved this improvement without making any compromises on mold robustness: in fact, thanks to features like the SmartLock™ stack design (which delivers excellent component life), XGuidance™ (which guarantees perfect mold alignment) and its superior LongLife™ treatment, the expected life of this mold exceeds industry standards.
“We are using open and available technology that can be mounted not only on SIPA XFORM GEN3 and GEN4 500-tonne production systems but also on other compatible platforms on the market, as long as they do not incorporate special protective software,” says Cavalet.