INSTALLATION FOR PRODUCING A FILM WEB AND METHOD FOR OPERATING SUCH AN INSTALLATION

Abstract

An installation for producing a film web and a method for operating such an installation includes a control circuit having a controller, a sensor and an actuator integrated into the ongoing film production process. The sensor is set up to sense a flatness of the film web, and the sensor is data-connected to the controller, wherein the controller is data-connected to the actuator and the actuator is actuated by the controller in order to control film production on the basis of the flatness.

Claims

1. An installation for manufacturing a film web by means of a die from a plastic melt provided by an extruder and for winding up the film web to a film roll by means of a winder, the installation configured to guide the film web on its path along a machine direction from the die to the winder around a guide roller and finally to wind it up onto the film roll at the winder, the installation comprising a control circuit with a controller, a sensor and an actuator, wherein the sensor is adapted to determine a measure for the flatness of the film web, and the controller is adapted to actuate the actuator using the measure of the flatness in order to improve the flatness of the film web.

2. The installation according to claim 1, wherein the installation has a second control circuit with a sensor which is adapted to determine a measure of a deviation of the thickness profile, and with a controller adapted to actuate an actuator using the measure of the deviation of the thickness profile in order to improve the deviation of the thickness profile.

3. The installation according to claim 1, wherein the controller is data-connected to the actuator.

4. The installation according to claim 1, wherein the controller is connected to the actuator by motor current.

5. The installation according to claim 1, wherein the actuator is adapted to actuate a heating means or a longitudinal stretching unit in the path from the die to the winder.

6. The installation according to claim 1, wherein the sensor is adapted to detect a roll-off edge of the film web at the guide roller, the sensor being data-connected to the controller.

7. The installation according to claim 1, wherein the installation is embodied as a blown-film plant, with the die being a ring-shaped die and a lay-flat device and a take-off device being provided in the path from the ring-shaped die to the winder.

8. The installation according to claim 7, wherein the sensor is arranged in the path from the ring-shaped die to the winder externally to the lay-flat device.

9. The installation according to claim 8, wherein the sensor is arranged in the path from the ring-shaped die to the winder externally to the take-off device.

10. The installation according to claim 7, wherein a longitudinal stretching device is arranged in the path from the ring-shaped die to the winder between the take-off device and the sensor.

11. The installation according to claim 1, wherein the installation is embodied as a flat-film plant, wherein the die is a flat-film die and in the path from the flat-film die to the winder a chill roll is arranged first, the flat-film die extruding the film onto the chill roll.

12. The installation according to claim 1, wherein in the machine direction before the sensor, a charging device for applying an electrostatic charge between the film web and the guide roller is arranged so that with the charging device switched on during operation of the installation, the roll-off edge of the film web moves downward from the guide roller and varies in height.

13. The installation according to claim 1, wherein the guide roller is arranged at a ground station.

14. The installation according to claim 1, wherein the guide roller is the last guide roller before the winder in the machine direction.

15. A method for operating an installation for producing a film web by means of a die from a plastic melt provided by an extruder and for winding up the film web to a film roll on a winder, including the steps of adapting the installation to guide the film web on its path along a machine direction from the die to the winder around a guide roller and wind it up onto the film roll at the winder, the installation having a control circuit with a controller, a sensor and an actuator, wherein the sensor determines a measure for the flatness of the film web, and the controller actuates the actuator using the measure for the flatness so as to improve the flatness of the film web.

16. The method according to claim 15, wherein the sensor is adapted to detect a roll-off edge of the film web at the guide roller, wherein the controller receives data from the sensor via a data connection, the controller performs a comparison and, based on the results of the comparison, the controller actuates the actuator via a data connection in order to adjust a heating means or a longitudinal stretching unit in the path from the die to the winder.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0054] In the following, the disclosure will be explained in more detail by means of an example of embodiment with reference to the drawing wherein FIG. 1 schematically shows the structure of a blown-film plant.

DETAILED DESCRIPTION OF THE DRAWING

[0055] The blown-film plant 1 in FIG. 1 substantially comprises three extruders 2 feeding a blowing head 3 with plastic melt which has been produced in the extruders 2 from plastic granulate.

[0056] The blowing head 3 blows out a film tubing 5 in an extruding direction 4, in this case, vertically upward, from a ring-shaped die. After passing through a lay-flat device 6, the film tubing 5 passes through a take-off roller pair 7 (not shown in detail).

[0057] Then the film tubing 5 is transferred in two layers in the machine direction 9 up to a winder 10 as a laid-flat endless film web 8.

[0058] In the path from the take-off device, which is defined by the take-off roller pair 7, to the winder 10 the film web 8 first passes through a longitudinal stretching unit 11 according to the patent application WO 2014/023282 A1 by the present applicant.

[0059] Above that, the film web 8 passes through a reversing unit 12, and then through a path 13 leading downward towards the winder 10.

[0060] Close before the winder 10, in this case, at the penultimate guide roller 14 before the winder 10, an optically delimitated inspection space 15 is crossed.

[0061] The inspection space 15 contains, on the circulating face of the guide roller 14, a lamp 16 directed towards the guide roller 14.

[0062] The film web 8 passes around the guide roller 14, detaches itself from the surface of the guide roller 14 at a roll-off edge 17 (not shown in detail) and continues in the machine direction 9.

[0063] A camera 18, in this case, a CCD camera or a different type of camera which transmits digital images, is directed at the roll-off edge 17.

[0064] The image data of the camera 18 are transferred via a first data connection 19 to a controller in a central controlling unit 20. The controller compares the measured values of the camera 18 with predefined desired values or with the actual values determined previously, where deviations of the roll-off edge 17 from an ideal straight line are evaluated by the controller so that the controller can make deductions about elevations in the film.

[0065] As soon as the controller detects deviations, it actuates a temperature control actuator 22 and/or a mechanical control actuator 23 via a second data connection 21.

[0066] The longitudinal stretching unit 11 consequently alters the film web 8 mechanically. For this purpose, the thick spots in the film web 8, which were previously detected by the camera 18, are reduced or even completely eliminated. In case this should result in new thick spots, these will also be detected automatically by the camera 18 as a consequence of variations in the roll-off edge 17, will be recognized as such by the controller in the controlling unit and also reduced or eliminated by means of a controlling intervention via the second data connection 21.

[0067] By means of iteration, the plant can thus achieve an optimum production.

[0068] The time needed for iteration is only the duration needed for reaching a new steady state as well as the time for the passage along the machine direction 9 from the exit from the longitudinal stretching unit 11 to detachment from the guide roller 14.

[0069] Temperature and stretching rate, which are two particularly important settings for the film quality, can now be set automatically. Thus, all subjective criteria used in producing the film are no longer needed.