PETpla.net Insider 01+02 / 2012

PREFORM PRODUCTION 10 PET planet insider Vol. 13 No. 01+02/12 www.petpla.net Netstal’s ‘LightBase’ process reduces weight while improving material distribution across PET bottles Ace of base Netstal has now introduced enhancements to its Calitec tech- nology that are aimed at increasing process efficiency and reducing material usage, leading to lighter weight containers. Presented under the brand of LightBase, the new developments introduce different base geometries for preforms, which improve the blow-out behaviour of bottle bases. Netstal says that these modified base geometries optimise preform surfaces for the subsequent heating process in the blowing machine so that they are better able to absorb the ther- mal energy from the UV lamps. The company claims that this enables the base to be heated to optimum tem- perature later in the blowing process and blown out to produce thinner walls. Improved material distribu- tion reduces the weight of the base and prevents build-up of material with consequent high level of crystal- lisation, which means that the base cannot crack as easily as in earlier methods. The process is claimed to deliver material savings accompanied by improved bottle strength. Netstal says that these developments enable the complete removal of unnecessary base material. Preblow for thinner walls Netstal’s patented ‘preblow’ pro- cess blows out the base area of the preform immediately after the injec- tion moulding process. It says that this enables adjustment of both the base outline and surface dimensions. Enlarging the base outline reduces wall thickness in the base, which makes it possible to heat the area in the subsequent blowing process more precisely and efficiently, as a larger surface with a lower wall thickness requires less heating from the UV lamps in the blowing machine. Cutting 1l juice bottles produced by the new process reveals a wall thickness curve without any material build-ups in the base area; the cut surface runs evenly over the sprue point. The weight of the bottom sec- tion on the test bottle, for which the preform was not designed, was 0.6g. Testing found that it is possible to achieve a weight reduction of more than 1g, relative to the preform. Lighter but stronger bottles The LightBase test bottle demon- strates other properties as a result of better material distribution. Over- all wall thickness can be increased, as shown in Fig. 4. Analysis of the LightBase bottle using 16 wall meas- urement points positioned axially on top of each other determined that the material taken from the base area Fig. 1: Depiction of the preblow process Light weighting SPECIAL