EDITOUR PETplanet Insider Vol. 26 No. 12/25 www.petpla.net 16 Everything done correctly and yet inclusions in the preform? by Alexander Büchler The material for the preform must be heated sustainably with the necessary energy. No more, but by no means less. Who hasn’t experienced it in preform production: you have set everything up correctly, you start up and there are inclusions in the preform. The search begins. Is it the material - it contains rPET - or the plasticisation? Or what exactly …? Editour Interview with ReduPET // June 16, 2025 We met: Stefan Bock, CEO The explanation is quite simple. In 90% of cases, it’s the dryer. All dryer manufacturers measure the temperature of the granulate at the feed throat to the injection moulding machine. However, they only measure the surface temperature. The temperature is not reached in the core of the granules. Practically like a soft-boiled egg. The right temperature outside, but not yet inside. This is where the retrofittable WAVE system from ReduPET comes in (WAVE: Waste Analysis and Visualization of Energy). Traditionally, air temperature and air volume (in m³) are measured. And as a control value, the external temperature of the granules. ReduPET is moving away from the hands-on approach and focussing on the energy required and contributed. The energy required by the granules to dry is defined by the incoming air energy, which is easily measurable. Here, the mass flow must be taken into account as kg/h in order to calculate the energy contained. As with all other systems provided, measuring air volume alone is not sufficient. And finally, the energy that flows out of the hopper again must be calculated from the temperature and mass/h. And energy flowing in minus energy flowing out equals the energy that has flowed into the granulate. Actually, trivial but ingenious. Not too little, not too much With this simple physical approach, ReduPET manages to optimise the heating of the granulate. Not too little (to avoid unmelts/bubbles in the preform) but also not too much (resulting in material degradation/ yellowing increased, loss of energy twice, due to the chiller). The three energy values plotted over a timeline show very nicely production interruptions in which the system regulates itself down and also starts up again if the heating is running at the right temperature but does not achieve the required mass of air (unmelts/bubbles) or if there is a leak somewhere in the system or a unit fails (e.g. feeder) - irregularities, energy loss - and also shows if the heating supplies too much (fast) energy into the material and the granulate is under heat for longer than necessary (increased energy consumption, increased degradation). Sponsors Who hasn’t done everything right and still there are bubbles and unmelts in the preform? An example is the curve of the WAVE control: The required energy (green) suddenly goes to zero when production is interrupted and immediately back to maximum when starting up again. The other curves follow suit so that the energy lost is minimised.
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