Plastic Film and Extrusion

Equipment for low, stable tension on thin, stretchable plastic films, for clean winding and for reliable edge detection on transparent material.

Plastic film travels in roll form from the moment it leaves the extrusion line. Winders at the end of blown or cast film lines wind the film onto cores, and those rolls are later unwound again on printing presses, laminators, slitters or bag and pouch machines. Plastic films are thin, stretchable and often transparent, which makes it all the more important how the roll is carried, at what tension it is unwound and how its edge is tracked.

Roll handling on plastics lines

Because film is elastic, excessive tension stretches it and changes its thickness and width; too little tension leaves a loose wind and lets layers slip inside the roll. On the winder, reducing tension in a controlled way as the roll grows helps prevent crushing of the inner layers and telescoping of the roll. During slitting, small variations in film gauge cause the cores on a single shaft to build up to different diameters.

Which equipment goes where?

Air shaft: Grips the core at the winder and the unwind. On lines with frequent roll changes, an aluminium air shaft makes handling easier.
Friction shaft: On a slitter rewind, it lets each core turn at its own speed, giving more even tension across the strips. See the friction shaft and friction rings.
Brake: On unwinds that need low, precise torque, a magnetic particle brake gives smooth resistance that is adjusted by current.
Tension control: A tension controller drives the brake or motor from load cell or dancer feedback, helping to prevent thin film from stretching or going slack.
Web guiding: A web guide controller can work with a colour, fork or ultrasonic sensor; on transparent film an ultrasonic sensor detects the edge more reliably.
Adapter: An aluminium adapter can be used to run cores of different diameters.

What to consider when selecting

Film type and gauge determine the required tension range and the brake type that suits it.
Static electricity and dust may call for extra checks on lug and core surfaces.
On a slitter rewind, the number of strips and the core widths influence the choice of friction shaft.
For transparent or printed film, decide on the web guide sensor type in advance.
Shaft journal and core dimensions should be checked against a drawing of the machine.

For size options see the technical dimensions page, or request a quote for your line through our contact page.