Winding accuracy and alignment check on plastic film rolls

Need

On the end face of a clear film roll the layer boundaries are almost invisible; the roll rotates, vibrates and its diameter grows continuously. Edge wander starts as a few hundred microns per layer and becomes obvious only after the outer layers accumulate, when the roll is already scrap.

Solution approach

The profile sensor faces the end face; the laser line falls along the radius and reads the axial position of every layer group as a height, so roll rotation and diameter growth do not affect the result. The fork edge sensor follows the edge of the incoming film and shows the source of the drift early. A flat profile lets winding continue; when the step sum exceeds the tolerance the winder stops.

Process steps

1. 01

   Winding

   The film passes the idler roller and winds onto the roll on the cantilever shaft; the edge sensor follows the film edge.

2. 02

   Laser profile

   The laser line falls on the end face along the radius and the sensor reads the profile.

3. 03

   Edge profile

   The axial position of each layer is extracted; a flat end face gives a flat profile.

4. 04

   Drift watch

   As the film edge wanders, the outer layers shift forward and the profile becomes stepped.

5. 05

   Decide

   The total offset is compared with the tolerance limit; on a violation winding stops and the roll is changed.