Every technology has its limits. Injection molding is capable of doing almost incredible things, but when it comes to PET preforms, the signs are that its possibilities have almost been exhausted. There are limits to how thin you can make a preform wall before it becomes impossible—or at least economically unfeasible—to injection mold it.
Welcome to the XTREME world of PET preform injection-compression molding. As SIPA will demonstrate with its all-new XTREME machine, it is possible to produce preforms that are up to 10% lighter than even the lightest injection molded preform—but without losing any key properties. More weight can be shaved off the body and base of the preform than ever before. The new injection-compression technology takes the shackles off developers’ freedom to create new and unique designs.
Whereas just a short while ago, a preform with a length-to-wall thickness ratio (L/t) of much more than 50 was virtually unthinkable, SIPA’s XTREME technology makes an L/t ratio of 80 a reality. This is little short of amazing.
Injection-compression molding overcomes the issue of filling molds with very thin walls, by having the molds slightly open when injection starts, and then closing them as dosing finishes. This means lower injection pressure can be used, lower clamp force is needed (which has the additional benefit of extending mold life), and there is less stress on the melt--which means acetaldehyde (AA) levels are reduced, and resin intrinsic viscosity (IV) falls less.
XTREME IS THE ANSWER
With XTREME, it is now possible to produce preforms with bases thinner than ever before. In a conventional preform, the thickness of the base has more to do with enabling the mold cavity to fill than it has with bottle performance, but XTREME injection-compression removes that constraint. As a result, it is now possible to make a preform for a 500-mL bottle that weighs just six grams. The system is particularly well suited to production of preforms for bottles up to 1.5 L in volume, but can also be used for bottles up to 2.5 L.
The XTREME is also a high productivity system. The mold opening and closing is working on a cam, so cycle time is just a fraction of what it is on an injection molding machine.
On top of all that, the equipment uses lower temperatures and 10% less energy than an injection molding system with the same output—and it fits into much less space. A 72-cavity XTREME machine takes up just 34.5 m2, which is over 30m2 less than SIPA’s own XFORM. The XFORM is one of the most compact preform injection molding machines on the market.
FLEXIBLE, BUT NOT ONLY
The XTREME system is very simple to operate, it uses only pneumatic valves, and the mechanical layout has numerous similarities with rotary stretch-blow molding machines. No hydraulics are used, which is an extra bonus in terms of cleanliness. Pneumatic operation has a lower sensitivity to very short power interruptions and the overall quality of the electrical supply—a feature especially important for processors operating in developing countries.
The new system will also be very attractive to companies running a wide range of products, since it is very easy to change the lightweight mold blocks. In fact, the time it takes to change all the mold blocks, or stacks, on a 72-cavity XTREME machine is around 45 minutes, or one quarter of the time it takes to change a 72-cavity mold on a conventional injection molding machine.
The XTREME is more versatile, product changeover times are significantly reduced, and preform quality is higher. It is even possible to produce two different types of preform at the same time. Furthermore, 100% preform quality control is possible with an automatic opto-electronic system, which makes XTREME ideal for “lights out” operations that run with minimal manual intervention.
A REVOLUTIONARY ARCHITECTURE
The molds are mounted in blocks of three on a high-speed carousel fed by an extruder. The extruder rotates continuously, delivering melt to the dosing devices mounted directly under the preform molds, which are mounted vertically. There is no hot runner system in the conventional sense.
The pressure involved in the molding process is a fraction of the one used in injection molding, which has a significant effect on stress levels in the preform. This improves mechanical properties, as well as aesthetics.
The preform compression wheel continues to turn, and just before it completes a full circle, the molds open and the finished preforms are removed by a transfer star onto a preform cooler, where they remain until they are cool enough to be put into storage.
Of course, all of the significant advantages of the XTREME system would count for nothing if the system were not cost competitive. SIPA reckons that in use, the XTREME, with the savings it enables in weight, in energy consumption, in resin and additives, in costs of operation and maintenance, and in overall production efficiency, will have a very competitive total cost of ownership, TCO.
And this is just the beginning. XTREME provides a compelling set of advantages today, when it is being presented as a commercial proposition for the first time. But this is just the beginning of a new era that is bound to see those advantages increase as the technology is developed further.
All in all, XTREMELY interesting. Welcome to the new era of lightweighting.
Making Our Name for the Future
The XTREME ushers in a new standard for lightweighting. Its breakthrough injection-compression technology allows for much more gentle material treatment, and reduces preform weight by 10% compared to traditional injection systems—without the usual effects on bottle quality. With a cycle time of just 5s plus the lowest preform cost in the industry, the XTREME instantly expands the possibilities for PET bottle production design, flexibility, speed and efficiency.
We chose the name XTREME to express the outstanding opportunities we believe this technology brings to the PET bottle industry. We hope “XTREME” will always remind producers that:
· You have the ability to produce any number (‘X’) of preforms
· You can rely on this machine for top performance
· You can innovate beyond the usual industry limitations
· You can exceed expectations for productivity and efficiency
· You are prepared to handle any future ideas or challenges for creating preforms
· You can succeed with this machine even in very severe environmental conditions
A Partnership for PET Success
Choosing solutions like our XTREME gives producers access to a wealth of PET design, production and engineering knowledge all in one place. Customers can consult our experts for advice and solutions at any stage of the PET production process to keep costs down and productivity high.
