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12.03.2018 Knife rotor minimises dust content of PVC pellets

Coperion, Stuttgart, Germany, has introduced a new type of knife rotor which makes it possible to produce extremely low-dust PVC pellets for cable manufacture. This innovation forms the central component of the company’s EGR eccentric pelletising systems. Rotating directly on the die plate of the EGR, and fitted with pelletizer knives that have also been optimised, the rotor (patent pending) permits particularly smooth and gentle cutting of temperature- and shear-sensitive plastics. This greatly improves the quality and further processability of the pellets produced as compared to the types previously available. Coperion will be presenting the new knife rotor for the first time at Wire 2018, Düsseldorf, 16-20 April.
Coperion specified a special metal alloy and design for the production of both the new rotor and the knives mounted on it. As a result of these technical improvements, the knives remain in particularly even contact with the die plate during operation. The result is very high cutting quality that forms the basis for achieving the desired substantial reduction of the proportion of fines in the pellets.
As a general rule, the occurrence of such fines essentially depends on the PVC recipe used and the knife arm speed required to attain a particular pellet length. In practice it is possible to reduce the quantity of fines by adjusting the knife rotor, but not avoid them altogether. The consequences of these fines becoming detached during pneumatic conveying of the pellets is both increased waste and severe contamination of the conveying pipes and the cooler. By contrast, Coperion's new knife rotor/knife combination, makes it possible to reduce the proportion of fines almost down to the detection limit across the whole spectrum of throughput rates and cutting speeds tested. 
Coperion’s Kombiplast KP two-stage processing system, equipped with EGR eccentric pelletizer and the new knife rotor, for production of enhanced quality PVC pellets
In contrast to the output of conventional knife rotors (left), the new EGR unit clearly minimises pellet dust content

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