For the last two years or so, SIPA has been incorporating the Cappello preform base design created by Milan company Concordia Development into its preform molds. This highly popular design, now used by several major brands around the world, makes it possible to reduce the overall weight of a PET bottle by around two percent.
As we said when we announced the news of the agreement with Concordia in SIPA Magazine back in 2012, customers can expect a very fast return on investment when implementing Cappello. We said this is because of the material savings that processors obtain by implementing the design, and because of the limited changes that need to be made to existing injection molds.
Minimal changes to the injection mold
Implementation of the Cappello design requires modification to the core and the gate insert, as well as to the cooling insert of the take-out tube—and nothing else. SIPA can modify existing molds that it has produced itself, as well as molds from third parties. (It can also incorporate the Cappello base design into new molds of course).
We want to provide some detail as to how the ROI comes so quickly. Let’s assume you have a 96-cavity mold for 21-g preforms for CSD bottles. If you are running your injection molding machine on an 11-second cycle, you should be making around 235 million preforms in a year. Normally, that would require around 4950 tonnes of PET. By implementing the Cappello design, you will save around 95 tonnes of PET.
Big savings in materials
At a current price of 1400 euros/tonne for PET, that’s a saving of some 130,000 euros. Based on the cost of converting your mold to the Cappello design, you will recoup your investment in no more than eight months.
The Cappello base design leads to better material distribution in the base of the finished bottle. It has a slightly more pointed profile that standard designs, providing material savings around the injection point, in an area where there is usually excess of amorphous material on a blown bottle.
Blow molding line almost unaltered
There are normally no changes required on the blowing process side—possibly fine tuning to the reheating process—and no changes at all to the stretch-blow molding hardware; the new preform tip still has the required mechanical resistance to the stretch rod during stretch-blow molding. The finished bottle has mechanical properties undistinguishable from bottles made with standard preforms. Indeed, in CSD applications, performance may be even better, especially in terms of stress cracking resistance.
The Cappello design has been proven to be suitable for carbonated applications from 0.33 liter to 3 liter, and for non-carbonated applications from 0.33 liter to 20 liter.