The issue:

During the operation of cast film extrusion, a common issue arises when the heated film undergoes stretching towards the cold rollers, resulting in undesired shrinkage at the edges. This phenomenon, known as necking, contributes to an uneven thickness in the film. The extent of necking is influenced by both the polymer characteristics and the melt temperature. The final film, displaying non-uniform thickness, is deemed unacceptable due to its adverse impact on overall quality.

The remedy:

Electrostatic charges prevent necking in film extrusion by using static charging electrodes at the edges. The Valstat electrodes are placed at both ends of the film—as shown in the sketch. The electrostatic forces generated by these electrodes help to pin the edges of the film onto the chill roller. This controlled pinning minimises uneven stretching and shrinkage at the edges, resulting in a superior end product. Unlike traditional methods such as using compressed air nozzles, electrostatic charges provide an effective, quiet, and cost-efficient solution to prevent necking on cast film lines.

AxisValence offers a range of off-the-shelf and customised electrostatic control products like static eliminators, charging systems, static charge monitoring systems, for industrial applications. Contact us to know more.