Improving Oval PET bottles: Higher Quality with Preferential Heating from KHS

Special bottle shapes make high demands of many stretch blow molders during production. The preferential heating system (PH) developed by the KHS Group now enables bottlers to achieve perfect bottle quality even with extremely oval bottles in an energy-saving, safe and reliable process. The systems provider now also offers this option for its successful InnoPET Blomax Series IV.

Regarding the energy-efficient manufacture of PET bottles the InnoPET Blomax Series IV stretch blow molder is one of the most powerful on the market. With preferential heating fillers of oval bottles benefit from a manufacturing process which KHS has been successfully applying in older series of stretch blow molders since the 1990s.

Homecare and personal care products in focus

In transferring the technology to the latest series of KHS stretch blow molders all the benefits over previous machines are retained. These include the much 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 molder,” explains Marco Böhnke, product manager at KHS Corpoplast. “This means that the areas of the bottle which come into contact with the blow mold 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 also 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 molding 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 realize 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 very 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.