EDITOUR PETplanet Insider Vol. 26 No. 10/25 www.petpla.net 14 Material savings from neck to base by Alexander Büchler The injection moulding process requires a hot/liquid core as the plastic part cools in the mould until it solidifies completely. Otherwise, the material that has already been injected would shrink due to cooling and sink marks would be visible. The preform developer must therefore ensure that - starting from the injection point to the last point at the top of the neck - the flow paths become continuously thinner so that the preform can solidify backwards from the neck and the shrinkage is compensated via the hot core. Editour Interview with ReduPET // June 16, 2025 We met: Stefan Bock, CEO In the stretch blow moulding process, however, one doesn’t need this kind of material distribution, here an optimum (weight-saving) material distribution would be as follows: a stable neck area, thin walls and an even thinner preform base. If you were to inject the preform the other way round (from the neck area to the base), the material distribution in the preform would come pretty close to the requirements of stretch blow moulding. I have not yet seen a corresponding mould. With its preform compression moulding XTREME, SIPA is the only company to optimise material distribution in the preform for the stretch blow moulding process. This is not possible in conventional injection moulding due to the hot core required by the system as described above. ReduPET has taken up the challenge and continues to mould the floor area in the aftercooling station to the outside. This distributes the material better and makes the floor area much thinner. As the process takes place outside the mould, the technology has no influence on the cycle time. This is of course particularly impressive with 20L canisters (see PDG article on page 10) where 25% material could be saved from 485g to 370g. The owners of the patents ReduPET and CPS (Creative Packaging Solution) intervenes more in the preform geometry with their Neck-Lite technology. The initial consideration is the same: the preform needs its hot core right up to the tip. In addition to the unnecessary accumulation of material in the floor area, there is also an unnecessary accumulation of material on the neck between the shoulder and the neck ring. The wall thickness there is necessary to completely fill out the neck finish. The idea now is that the necessary wall thickness is only at least minimum five positions around the neck, sufficiently to have the hot core up to the tip and to remove material in between. Visually, the neck now looks as if it has bars. The stretch blow-moulding machine manufacturers have reservations as to whether the “bars” - which now lie exactly in the preform and bottle holders - will not interfere with the high-speed systems. Mohamad Rias from Oman is using the new geometry from SIPA and Krones systems for the first time. The new neck geometry could be driven at the same speed without changing the holders. The water preform’s weight could be reduced by 0.15 g per preform using Neck-Lite. That results in a savings of 75 t/a of PET for 500 million preforms. www.redupet.swiss Sponsors to date The picture clearly shows the bars in the Neck-Lite geometry on the preform neck. Neck and base of most bottles on supermarket shelves are still showing an obvious optimisation potential of up to 8%. Neck-Lite acts directly in the mould and has no influence on the system. An especially developed geometry below the transport ring allows thinnest wall sections while the thread is fully formed.
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