Method for Controlling a Nozzle Slot of a Discharge Nozzle for a Film Track of a Flat Film Machine

Abstract

The invention relates to a method for controlling a nozzle slot (112) of a discharge nozzle (110) for a film track (FB) of a flat film machine (100), comprising the following steps: acquiring an actual profile (IP) of the nozzle slot (112), detecting a thickness profile (DP) of the film track (FB), comparing the detected thickness profile (DP) of the film track (FB) with a preset profile (VP), determining a profile deviation (PA) as a result of the comparison, performing a controlling intervention to change the nozzle slot (112) based on the profile deviation (PA) and the actual profile (IP).

Claims

1-12. (canceled)

13. A method for controlling a nozzle slot of a discharge nozzle for a film track of a flat film machine, comprising the following steps: acquiring an actual profile of the nozzle slot, detecting a thickness profile of the film track, comparing the detected thickness profile of the film track with a preset profile, determining a profile deviation as a result of the comparison, performing a controlling intervention to change the nozzle slot based on the profile deviation and the actual profile.

14. The method according to claim 13, wherein the effect of the controlling intervention is stored together with the actual profile as a result profile for use as an actual profile for a subsequent controlling intervention.

15. The method according to claim 13, wherein the actual profile is at least partially acquired by a simulation of the nozzle slot.

16. The method according to claim 13, wherein a stretching ratio of the film track downstream of the discharge nozzle is additionally taken into account for the controlling intervention.

17. The method according to claim 16, wherein the stretching ratio is taken into account with regard to at least the stretching speed or the stretching acceleration.

18. The method according to claim 13, wherein the actual profile of the nozzle slot is at least partially acquired as an adjusting profile by adjusting means of the discharge nozzle.

19. The method according to claim 13, wherein the actual profile of the nozzle slot is at least partially acquired as an average value.

20. The method according to claim 13, wherein the chronological development of the actual profile is at least partially stored.

21. The method according to claim 13, wherein the controlling intervention additionally takes into account at least one product parameter of the film track.

22. The method according to claim 13, wherein a normalization step is carried out.

23. The method according to claim 13, wherein a normalization step is carried out as a normalizing controlling intervention.

24. A controlling device for controlling a nozzle slot of a discharge nozzle for a film track of a flat film machine, comprising an acquisition module for acquiring an actual profile of the nozzle slot, a detection module for detecting a thickness profile of the film track, a comparison module for comparing the detected thickness profile of the film track with a preset profile, a determination module for determining a profile deviation as a result of the comparison, further comprising an intervention module for performing a controlling intervention to change the nozzle slot based on the profile deviation and the actual profile.

25. The controlling device according to claim 24, wherein at least the acquisition module, the detection module, the comparison module, the determination module or the intervention module are designed for carrying out a method for controlling a nozzle slot of a discharge nozzle for a film track of a flat film machine, comprising the following steps: acquiring an actual profile of the nozzle slot, detecting a thickness profile of the film track, comparing the detected thickness profile of the film track with a preset profile, determining a profile deviation as a result of the comparison, performing a controlling intervention to change the nozzle slot based on the profile deviation and the actual profile.

Description

[0029] Further advantages, features and details of the invention will be apparent from the following description, in which embodiments of the invention are described in detail with reference to the figures. Thereby, the features mentioned in the claims and in the description may each be essential to the invention individually or in any combination. The figures schematically show:

[0030] FIG. 1 an embodiment of a controlling device according to the invention on a flat film machine,

[0031] FIG. 2 the embodiment of FIG. 1 in a schematic cross-section,

[0032] FIG. 3 a representation of a possible thickness profile,

[0033] FIG. 4 a representation of a possible actual profile of the nozzle slot,

[0034] FIG. 5 a representation of a profile deviation on a thickness profile,

[0035] FIG. 6 one possibility of an adjusting profile in the actual profile,

[0036] FIG. 7 the embodiment of FIG. 6 as a result profile,

[0037] FIG. 8 the embodiment of FIGS. 6 and 7 with a normalizing profile and

[0038] FIG. 9 a representation in top view for a stretching ratio of the film track.

[0039] FIGS. 1 and 2 schematically show a flat film machine 100, which is equipped with a plurality of adjusting means 120 along the transverse direction QR. These adjusting means 120 may, for example, be thermal bolts. These allow a nozzle lip of a discharge nozzle 110 to be acted upon mechanically in order to be able to vary the discharge thickness at a nozzle slot 112 accordingly. Material melt in the form of a film track FB is discharged along the production direction PR via this nozzle slot 112.

[0040] With the aid of a detection module 30, a controlling device 10 is able to record a thickness profile DP locally or over the entire transverse direction QR for the film track FB. The detection module 30 can also be mounted movably in order to be able to record the thickness profile DP over as large a region of the film track FB as possible via a transverse displacement along the transverse direction QR. The acquired thickness profile DP can actually be acquired and further processed via the detection module 30.

[0041] By means of the acquisition module 20, it is possible to directly or indirectly acquire the actual profile of the nozzle slot. This can be a separate sensor mechanism spaced from the adjusting means 120, but also arranged on them. An acquisition module 30 can be used to acquire the thickness profile DP. Thus, it is possible to acquire two input values in the form of the actual profile IP and in the form of the thickness profile DP. Via a comparison module 40 and a determination module 50, comparisons with a preset profile VP can now lead to the profile deviation PA. Based on this profile deviation PA and with the aid of the actual profile IP, an intervention module 60 can now provide appropriate controlling interventions for the adjusting means 120. FIG. 2 shows a possible cross-section, which well represents the nozzle slot 112 with its thickness adjustment by the adjusting means 120.

[0042] FIG. 3 shows schematically how such a thickness profile DP can be designed in the transverse direction QR. Two edge sections are provided here with relatively large deviations and correspondingly relatively wide preset profiles VP. Decisive for the produced film track FB to be provided with high quality is the central so-called net region, which is provided with correspondingly narrow presets as preset profiles VP. A corresponding deviation is shown in detail, for example in FIG. 5. There, a thickness profile DP is found which exceeds a preset profile VP at one point. This is therefore a thick spot where the film track FP is too thick, which is reflected here by an increased profile deviation PA. This profile deviation PA can now be used qualitatively and quantitatively as the basis for the controlling intervention within the controlling device 10.

[0043] FIG. 4 shows how mechanical action by the adjusting means 120 and corresponding mechanical counter-pressure of the melt from the nozzle slot 112 results in a complex geometric elastic deformation of the discharge nozzle 110 as the actual profile IP. In this case, the individual forces cause a transverse correlation, i.e. the two adjusting means 120 influence each other side by side in the same way as the counter-forces in the melt distribution can influence each other transversely. The result is a very complex actual profile IP, as shown schematically in FIG. 4. In addition to the illustrated local changes of the actual profile IP, a global change is also conceivable.

[0044] While according to FIG. 4 such an actual profile IP is directly acquirable by measurement, simulation or other means, indirect possibilities can also provide the actual profile IP to a method according to the invention. FIGS. 6, 7 and 8 show here the possibility of using an adjusting profile SP of the adjusting means 120. For this purpose, position sensors, thermal sensors, but also the feedback of the controlling interventions can be used in an indirect way. FIG. 6 shows an actual profile IP, which is formed around a center line as an average value. The individual adjusting means 120 can now be assigned a controlling intervention based on this actual profile and based on a detected profile deviation PA, for example as shown in FIG. 5. This controlling intervention results in a movement for each or at least some of the adjusting means 21 as shown in their final position in FIG. 7. Thus, this is the result profile RP, which represents the result of the controlling intervention. This result profile RP can now be used as the actual profile IP for the next run of a controlling intervention according to a method according to the invention.

[0045] FIG. 8 now shows that after a plurality of runs of the method according to the invention, potentially potentiating sources of error can occur. For example, it is now possible to bring all the adjusting means 120 into a normalizing position according to the normalizing profile NP either on a digital basis or on a real basis in a normalizing step. Based on this normalization profile NP, this profile itself can only be used as the actual profile IP for the next run of the method according to the invention.

[0046] FIG. 9 also shows that the stretching ratio can also be relevant for the method according to the invention. It is thus possible that a so-called neck-in occurs, i.e. the film width of the film track FP decreases in the direction of the production direction PR and in relation to the transverse direction QR, if the film track FB is drawn off from the cooling roller at a correspondingly higher speed.

[0047] The foregoing explanation of the embodiments describes the present invention exclusively in the context of examples. Of course, individual features of the embodiments can be freely combined with each other, provided that this is technically reasonable, without leaving the scope of the present invention.

LIST OF REFERENCE SIGNS

[0048] 10 controlling device

[0049] 20 acquisition module

[0050] 30 detection module

[0051] 40 comparison module

[0052] 50 determination module

[0053] 60 intervention module

[0054] 100 flat film machine

[0055] 110 discharge nozzle

[0056] 112 nozzle slot

[0057] 120 adjusting means

[0058] FB film track

[0059] IP actual profile

[0060] RP result Profile

[0061] NP normalizing profile

[0062] SP adjusting profile

[0063] DP thickness profile

[0064] VP preset profile

[0065] PA profile deviation

[0066] QR transverse direction

[0067] PR production direction