Electrostatic discharge on the rewinder of a blown film extrusion line
How does blown film extrusion work?
A blown film is a film made of a thermoplastic material, which is produced with the help of a special blown film extrusion line. The way it works is that molten plastic is blown out of a ring-shaped nozzle with the help of air. The solidified tube is collapsed at a height of 10-20 meters by a pair of rollers. At the end of the line, the film is cut lengthwise and usually wound separately on two winders. Typical machine speeds are around 10-20 m/min. These continuous films are mainly used for packaging of food, medical products or in the pharmaceutical sector.
During the winding of blown films, problems arise due to electrostatic charges.
The blown films are usually made of a high-resistance polyethylene which becomes electrostatically charged through contact and separation with other machine parts. The electrostatic charge very often amounts to several thousand volts at the winder, so that dangerous discharges to persons can occur. Persons can be injured by direct contact with the winder, but accidents due to startle reactions also occur time and again. In addition to the danger to persons, highly charged film winders attract dust, dirt and insects from the immediate vicinity. This is a particular problem for films used in the food, pharmaceutical or medical sectors. The electrostatic charges on the rewinder must therefore be removed. The two rewinders were equipped with 2 pcs ionSTAR RX3 and 2 pcs blueBAR directly after the corona treatment. The maximum distance between the ionSTAR RX3 electrode and the foil was 800 mm. The charge on the foil was 5 – 10 kV, which did not yet meet the requirements.
Our solution
The highly charged plastic wrap is reliably discharged with unique ionization bars. The bars can be installed at a large distance from the winding surface.
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The following Eltex products have been installed and tested on site by our experts. If you would like to learn more or have any questions, please do not hesitate to contact us.
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Protocol/device description files of the fieldbus interfaces for integration into the machine control: Information fieldbus integration
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