METHOD FOR CHANGING THE MATERIAL IN AN EXTRUSION DEVICE

Abstract

The present invention relates to a method for changing material in an extrusion device comprising at least two supply devices for supplying feedstock for an extruder, comprising the following steps: identifying a change request for changing material in an extrusion device, predetermining a production stability for a time after the material of at least one supply device has been changed, comparing the predetermined production stability to a threshold value of stability, changing the material in at least one supply device depending on the result of comparison.

Claims

1. A method for changing material in an extrusion device comprising at least two supply devices for supplying feedstock for an extruder, comprising the following steps: identifying a change request for changing material in an extrusion device, predetermining a production stability for a time after the material of at least one supply device has been changed, comparing the predetermined production stabilit to a threshold value of stability, changing the material in at least one supply device depending on the result of comparison.

2. The method according to claim 1, wherein for the step of predetermining the production stability, the impact on the production stability for the feedstock and a subsequent material are read out from a database.

3. The method according to claim 1, wherein for the step of predetermining the production stability, the correlation of the supply device to a corresponding layer of the film, which is to be produced, is considered.

4. The method according to claim 1, wherein the production stability for a multi-layer film is simulated supply device.

5. The method according to claim 1, wherein the steps of predetermining and of comparing are carried out for all supply devices, and an order of the supply devices for changing the material is subsequently provided.

6. The method according to claim 1, wherein the step of changing the material is carried out as long as at least one of at least one stable or stabilizing layer of a film results in the predetermination of a production stability above the threshold value of stability.

7. The method according to claim 1, wherein the actual production stability is monitored and recorded at least while or after changing the material in at least one supply device.

8. The method according to claim 1, wherein the steps of predetermining and of comparing are carried out for a manual proposal of an order.

9. The method according to claim 1, wherein at least one production parameter is adapted while changing the material for at least one supply device, depending on the result of comparison.

10. The method according to claim 1, wherein a rinsing time is additionally determined for each feedstock, which is to be changed, and is considered for the selection of the order of the supply devices.

11. The method according to claim 1, wherein the gradient of the production stability is predetermined for changing all of the material for all supply devices and is considered for changing the material.

12. The method according to claim 1, wherein the steps of predetermining and of comparing are repeated while changing the material.

13. The method according to claim 4, wherein at least two different orders of the supply devices are simulated when changing the material in terms of the production stability, which is to be expected.

14. The method according to claim 4, wherein all different orders of the supply devices are simulated when changing the material in terms of the production stability, which is to be expected.

15. The method according to claim 9, wherein at least one of the following production parameters is adapted while changing the material for at least one supply device, depending on the result of comparison: temperature of the extruders film thickness speed of the production extruder output blow-up ratio.

16. The method according to claim 1, wherein the steps of predetermining and of comparing are carried out continuously while changing the material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a first embodiment of an extrusion device according to the invention in the operating state,

[0037] FIG. 2 shows the embodiment of FIG. 1 during a lowering of the filling levels,

[0038] FIG. 3 shows the embodiment of FIGS. 1 and 2 with a filling level at changing filling level,

[0039] FIG. 4 shows the embodiments of FIGS. 1 to 3 with a fluctuating filling level, which is kept at changing filling level,

[0040] FIG. 5 shows the embodiment of FIGS. 1 to 4 during a cleaning situation,

[0041] FIG. 6 shows the embodiment of FIGS. 1 to 5 during the refilling with a subsequent material,

[0042] FIG. 7 shows an option of a course of the production stability,

[0043] FIG. 8 shows a further option of a course of a production stability,

[0044] FIG. 9 shows a further option of a course of a production stability and

[0045] FIG. 10 shows an alternative embodiment of an extrusion device.

DETAILED DESCRIPTION

[0046] FIGS. 1 to 6 illustrate an extrusion device 10 schematically, which is equipped with two supply devices 20. Each of these supply devices 20 is equipped with a feed container 26, a down pipe 24 and a weighing funnel 22. FIG. 1 shows the operating situation, wherein each supply device 20 is filled with a feedstock E up to a full operating filling level BF. In this state, the respective feedstock E is supplied to an extruder 30 via dosing screws 28 and is used for the production of the plastic film there. A method according to the invention is thereby carried out in a corresponding control device 40.

[0047] As preparation for changing the material, FIG. 2 shows how a lowering of the filling levels F of the feedstock E takes place. By further production without refilling into the supply devices 20, the filling level F now drops, until it reaches a changing filling level WF according to FIG. 3. So as not to fall below this changing filling level WF, provision is made for corresponding filling level sensors 42, so that a short refilling in the form of a refilling push takes place at the point in time according to FIG. 3, so that substantially a fluctuating holding of the filling level F at the level according to FIGS. 3 and 4 takes place.

[0048] FIG. 5 shows, how the feedstock E can be completely discharged downwards from the supply devices 20 at the time of actually changing the material. The catching can occur in a discharge container 60 as well as with the help of a returning device 70. For the discharging, here discharge openings 50 are provided, which are closed by means of a discharge closure 52. The corresponding arrangement of the discharge containers 60 is possible via a container interface 54. Last but not least, provision is made for an opening sensor 58, which can in particular be used in response to a cleaning step, which is to be carried out, with a cleaning device 80 comprising a plurality of cleaning means 82.

[0049] It is illustrated in FIG. 6, how a subsequent material EF can already be filled back into the feed containers 26 of the supply devices 20 at this point in time, so that the switchover between the feedstock F and the subsequent material EF can subsequently take place particularly quickly and with small mixing.

[0050] FIGS. 7 to 9 show options of a course of the production stability PS over time. FIG. 7 shows, how a transition is to be made to an average production stability PS on the very right by means of the dashed line. On the left, the situation in the case of application formula is shown, and the situation in the case of subsequent formula is shown on the right. In the case of this course, it can be seen that the production stability PS is always above the threshold for stability SG. It is illustrated by means of the two curved illustrations that unwanted gradient courses exist here, even though the threshold for stability SG is always exceeded. The dashed line, by means of which a linear transition between the individual production stabilities PS is provided with substantially consistent and constant gradients, is preferred.

[0051] FIG. 8 shows a situation, which is unwanted and which is avoided by predetermining the production stability PS. In the course at the transition between the two formulas, a decrease of the production stability PS below the threshold for stability SG is thus at hand here, so that this path is avoided for a change strategy.

[0052] FIG. 9 shows a substantially optimized change strategy, so that the production stability PS lies at a higher level for the majority of time of the change between the two formulas, than in the case of the application formula. The production stability PS decreases strongly only shortly prior to the end of changing the material and then remains on the level of the subsequent formula. The threshold for stability SG is also never fallen below here.

[0053] FIG. 10 shows an alternative embodiment of an extrusion device 10. With regard to the advantages described according to the invention, said extrusion device is based on the embodiment of FIG. 1, but differs in the refilling function. A so-called batch process is thus provided here for the refilling. The feed container 26 is equipped with separate volumes, so that each volume of the feed container 26 can be understood to be a supply device 20. Components in the form of the down pipe 24 and of the weighing funnel 22 arranged therebelow are thus common components of the different supply devices 20. Below the weighing funnel 22, a mixing funnel, in particular comprising a mixer drive, is provided which allows for a homogenization prior to entering the extruder.

[0054] The above discussion of the embodiments describes the present invention only in the context of examples. It goes without saying that individual features of the embodiments, if technically expedient, can be combined freely with one another, without leaving the scope of the present invention.

LIST OF REFERENCE NUMERALS

[0055] 10 extrusion device

[0056] 20 supply device

[0057] 22 weighing funnel

[0058] 23 funnel opening

[0059] 24 down pipe

[0060] 26 feed container

[0061] 28 dosing screw

[0062] 30 extruder

[0063] 32 emergency sensor

[0064] 40 control device

[0065] 42 filling level sensor

[0066] 50 discharge opening

[0067] 52 discharge closure

[0068] 54 container interface

[0069] 56 sensor device

[0070] 58 opening sensor

[0071] 60 discharge container

[0072] 62 discharge volume

[0073] 70 return device

[0074] 80 cleaning device

[0075] 82 cleaning means

[0076] 84 dust sensor

[0077] E feedstock

[0078] EF subsequent material

[0079] BF operating filling level

[0080] WF changing filling level

[0081] F filling level

[0082] PS production stability

[0083] SG threshold value of stability