Improving oval PET bottles
Special bottle shapes make high demands of many stretch blow moulders during production. The preferential heating system (PH) developed by the KHS Group enables bottlers to achieve perfect bottle quality with oval bottles in an energy-saving, safe and reliable process. The systems provider offers this option for its InnoPET Blomax Series IV.
Homecare and personal care products in focus
In transferring the technology to the latest series of KHS stretch blow moulders all the benefits over previous machines are retained. These include the lower use of energy and the simpler design. Especially when processing items such as cleaning agents, laundry detergents or personal care products, which are very often filled into oval PET bottles, this process has many advantages.
“Without preferential heating the preform is heated evenly in the stretch blow moulder,” explains Marco Böhnke, product manager at KHS Corpoplast. “This means that the areas of the bottle which come into contact with the blow mould first cool down before the others.” As a result, the PVC hardens at these points so that the material is distributed unevenly in the ensuing bottle. The walls are thicker in these places. It is no longer possible to obtain as even a distribution of materials as possible and thus optimum stability and bottle quality in the ongoing stretch blow moulding process. If, as is the case with preferential heating, a preform is heated selectively according to its later bottle shape, this undesired effect is compensated for.
Special heater segment for a selective heating profile
Preferential heating is made possible by a special heater section at the end of the heating segment. Here, the system first rotates the PET preforms through the heater to obtain a basic heating profile. In the downstream PH section rotation is stopped, giving the preform its selective heating profile. The new heater box specially developed for this application plays a big role here, transferring the required heating energy to the preform through two opposite heater levels.
“We’re generally improving quality, especially the material distribution and stability of the bottle,” says Böhnke. Another effect of preferential heating is that “Thanks to this intelligent technology we can realise material savings of up to several grams per bottle.” This means that bottlers no longer have to use heavy preforms in order to achieve the same stability with an uneven distribution of materials without the PH process and can thus save on resources. The machine permits fast changeovers to round bottles, too, which gives converters in particular great flexibility. Preferential heating can not only be used in every new InnoPET Blomax Series IV as an option; it can also be retrofitted into existing systems.
