Cutting device and method for cutting a plastic film

Abstract

The invention relates to a cutting device (6) for cutting a plastic film (5) into a plurality of film strips (7), comprising: a conveyor device (10) for conveying the plastic film (5) along a conveyor track (11); a cutting bar (12) having a plurality of cutting blades (14), arranged next to one another in a parallel arrangement, wherein the cutting blades (14) each have a cutting edge (15) passing through the conveyor track (11); a movement device (16) for moving the cutting blades (14) from a first to a second cutting position, in which first or second cutting points of the cutting edges (15) are arranged on the conveyor track (11); a guide comb (18) having a plurality of guide teeth (19) extending between the cutting blades (14) for laterally guiding the cutting blades (14), wherein the movement device (16) is designed to move the cutting blades (14) relative to the guide comb (18) in order to transfer the cutting edges (15) from the first to the second cutting position.

Description

[0001] Cutting device and method for cutting a plastic film

[0002] Cutting device for cutting a plastic film into a plurality of film strips, preferably for use in the stretched state as warp strips and weft strips for feeding to a weaving machine, in particular a circular weaving machine, comprising: a conveyor device for conveying the plastic film along a conveyor track, a cutting bar with a plurality of cutting blades, each having a cutting edge penetrating the conveyor track, a displacement device for displacing the cutting blades from a first to a second cutting position, in which first and second cutting points of the cutting edges are arranged on the conveyor track.

[0003] Furthermore, the invention relates to a device for producing film strips, preferably for use as warp strips and weft strips, comprising: an extrusion system for producing a plastic film, a cutting device for cutting the plastic film into a plurality of film strips, and a stretching system for stretching the film strips.

[0004] Finally, the invention relates to a method for cutting a plastic film into a plurality of film strips, comprising the steps of:

[0005] Conveying the plastic film along a conveyor track,

[0006] Arranging cutting blades of a cutting bar in a first cutting position in which first cutting points of cutting edges of the cutting blades are arranged on the conveyor track, cutting the plastic film into the plurality of film strips by means of the cutting blades in the first cutting position,

[0007] Moving the cutting blades from the first to a second cutting position, in which second cutting points of the cutting edges are arranged on the conveyor track,

[0008] Cutting the plastic film into the multitude of film strips using the cutting blades in the second cutting position.

[0009] Industrial fabrics made from HDPE (high-density polyethylene), PP (polypropylene) or polyester / PET tapes have long been processed into sacks in a wide variety of shapes. The exceptionally high mechanical strength of tape woven sacks is due to the process of stretching the tapes. This orientates the thread-like polymer molecules lengthwise along the tapes. Tape woven sacks are exposed to high levels of stress during filling, loading and reloading during transport. Tape woven sacks are used, for example, in the transport of animal feed, food and minerals. The tapes, which in their finished state are usually 0.8 to 6 mm wide, are produced by extruding a flat film which can be cooled, particularly in a water bath, and is first cut into film strips approximately 2 to 12 mm wide. The strips can then be passed through a hot air oven.In this process, the ribbons are stretched longitudinally in their warm-plastic state by a factor of approximately 1:4.5 to 1:6, then cooled, and finally wound onto spools. In the next production step, circular looms (cf., for example, EP 2 829 645 A1 or EP 3 662 100) weave the warp and weft ribbons wound onto the spools into a tubular circular fabric.

[0010] To cut the flat film into film strips, a cutting bar with flat blades is used in the state of the art. The cutting bar and the film are adjustable relative to one another, which means that the blades can be used over a length of around 10mm. This can delay wear on the blades. As the ribbon extrusion line is designed for continuous operation, the line must be shut down to change the blades. The resulting production downtime should be kept as short as possible. In practice, however, it has been shown that the sharp cutting action of the blades is only guaranteed for a short time before the blades cause the film strips to fray along their long edges. The consequences of this are a loss of stretch and strength in the ribbons, dust, and malfunctions on the circular weaving machine.

[0011] Efforts have long been made to resolve these problems in order to ensure the most continuous operation of the ribbon extrusion line possible without interruption for knife bar changes and to maintain high strength and elongation values ​​of the ribbons.

[0012] In the prior art, two alternatives to the standard cutting bar have been proposed.

[0013] First, circular cutting bars were developed with rows of blades arranged at angular intervals around the circumference. After use, the currently used row of blades is replaced by the next, unused row of blades along the circumference by rotating the circular bar (see, for example, DE 31 37 826).

[0014] As a further alternative, it is known from EP 3 055 109 B1 to provide two parallel cutting bars which are exchanged for each other during the reduced production speed in a technically very complex process.

[0015] However, changing the blades is problematic with both alternatives to the standard cutting bar. If, for example, 250 blades are used on one bar, the precision of the two rows of blades would have to be exactly the same in terms of their lateral distance from one another to ensure that the new blades can be inserted into the exact cutting position when changing them. If the blades are not changed precisely, even a slight offset of the blades at reduced system speed can cut into the already cut ribbon. This can lead to tears in the film or the ribbon sheet. Another problem that remains unsolved is that the cutting sharpness of the blades is quickly lost and the available cutting length of the blades is very short.In order to reduce downtimes, the blades are often kept in the same position for too long in practice, resulting in large differences in cutting quality, which in turn lead to considerable differences in elongation and strength, which cause major problems during subsequent use in the circular loom.

[0016] Finally, DE 198 43 428 B4 describes a device for longitudinally cutting a plastic film into narrow film strips, using a knife bar on which a plurality of cutting blades are arranged side by side by means of spacers. The cutting blades are rotatably mounted to allow changing the cutting edge. This prior art does not solve the problems mentioned above. Only the replacement of the blades is somewhat simplified.

[0017] In contrast, the object of the invention is to alleviate or eliminate at least some of the problems of the prior art. The invention preferably aims to improve the cutting device mentioned above so that high-quality film strips can be produced with the longest possible operating times of the cutting device.

[0018] This object is achieved with a cutting device according to claim 1, a system for producing stretched film strips according to claim 10, and a method according to claim 11. Preferred embodiments are specified in the dependent claims.

[0019] According to the invention, the cutting device comprises a guide comb with a plurality of guide prongs extending between the cutting blades for lateral guidance of the cutting blades. The displacement device is designed to displace the cutting blades relative to the guide comb to transfer the cutting edges from the first to the second cutting position.

[0020] The precise lateral guidance of the cutting blades essentially prevents any deflection of the cutting blades in the transverse direction, i.e., in a direction parallel to the main plane of the plastic film and perpendicular to the direction of travel of the knife bar with the travel device. "Essentially" means that the cutting blades are arranged with a maximum play of preferably less than 0.05 mm, more preferably less than 0.02 mm, for example less than 0.06 mm, between the guide teeth of the guide comb in order to allow the cutting blades to be moved. The cutting blades are preferably arranged essentially parallel and equally spaced from one another in the transverse direction.

[0021] The design according to the invention offers particular advantages when the cutting device is used to produce film strips which, in the stretched state, are used as warp and weft strips in a weaving machine, in particular a circular weaving machine. The plastic film is produced as a film strip in an extrusion system which is designed for continuous operation and which must be shut down to change the cutting blades. The shifting device can be used to shift the cutting blades linearly and thus advance them in order to arrange an unused (or less heavily worn) cutting point on the conveyor track. The shifting device could easily be designed to use cutting blades with cutting edges of almost any length.In practice, however, the problem has been observed that the free ends of cutting blades clamped on one side begin to swing sideways, and this swing becomes more pronounced the further the cutting points are from the blade holder of the cutting beam. From a certain cutting length, the desired cutting widths of the film ribbons can no longer be precisely maintained across the entire film width. However, with the preferred use of the film ribbons in the stretched state as warp and weft ribbons for a circular loom, such width fluctuations are not tolerable because they would severely affect the fabric width and the fabric appearance. According to the invention, however, the shifting device is combined with the guide comb, with which the cutting blades are guided on their respective long sides. Advantageously, cutting blades can thus be used whose free, ieThe length available for cutting the plastic film is considerably greater than in the state of the art, without having to take the risk of fluctuations in the ribbon width.

[0022] In a preferred embodiment, the guide prongs of the guide comb are designed exclusively for lateral guidance of the cutting blades, but not for limiting deflection of the cutting blades in a direction perpendicular to the main plane of the plastic film. For this purpose, the cutting blades can be fixed on one side (i.e. only at one end, but not at the other end) in a blade holder of the cutting bar and thus blocked against movement in a direction perpendicular to the main plane of the plastic film. In this embodiment, the cutting blades protrude from the blade holder in the direction of the plastic film, with guide sections of the cutting blades each arranged between two guide prongs of the guide comb. In the first and second cutting positions, first and second sections of the cutting blades protrude from the guide comb towards the conveyor track to enable cutting of the plastic film.

[0023] Preferably, the guide comb is arranged stationary with respect to the displacement of the cutting bar. This means that the guide comb does not follow the displacement of the cutting bar with the displacement device. Thus, the cutting blades can be guided forward from the guide comb to varying distances, i.e., in the direction of the film conveyor path, by actuating the displacement device.

[0024] In a preferred embodiment, flat blades are provided as cutting blades, which are preferably arranged upright, i.e. the flat blades are arranged along planes that are perpendicular to the plastic film. The longitudinal axes of the elongated flat blades are preferably arranged at an angle to the plane of the plastic film, in particular at an angle of 30° to 60°, preferably 45°. The flat blades preferably each have at least one cutting edge on at least one of the opposite longitudinal edges, preferably on both opposite longitudinal edges. After the at least one cutting edge of one longitudinal edge has been used up, a change can be made to the at least one cutting edge on the other longitudinal side.Depending on the design, the longitudinal edge can be ground on one side to form exactly one cutting edge (like a carpet knife, also known as a Stanley knife) or the longitudinal edge can be double-edged (like a razor blade).

[0025] Depending on the design, the cutting bar can have at least 5, preferably at least 20, particularly preferably at least 70, in particular from 70 to 700, cutting blades. Accordingly, the guide comb preferably has at least 5, preferably at least 20, particularly preferably at least 70, in particular from 70 to 700, guide tines.

[0026] The preferred plastic film is a flat film or a film tube.

[0027] The plastic film preferably has a width of 500 millimeters (mm) to 2000 mm. The film strips preferably have a width of 0.8 to 15 mm. If the film strips are subsequently stretched for use as warp and weft tapes, the film strips preferably have a width of 1 to 6 mm in the stretched state.

[0028] The plastic film is preferably made of a plastic, preferably one of PP (polypropylene), PE (polyethylene), PES (polyethersulfone), PET (polyethylene terephthalate), polyolefin or a mixture thereof.

[0029] In order to be able to cut the plastic film immediately adjacent to the sections of the cutting blades guided by the guide comb, the guide comb is arranged in a preferred embodiment adjacent to the conveyor track along which the plastic film is conveyed. As a result, both the first cutting point in the first cutting position and the second cutting point in the second cutting position are arranged adjacent to the guide comb, with which guide sections of the cutting blades adjacent to the first and second cutting points are guided laterally and thus secured against lateral movement. Advantageously, the first and second cutting points of the cutting blades essentially do not swing laterally in the first and second cutting positions, thereby ensuring a constant ribbon width regardless of the tracking of the cutting blades.When transferring from the first to the second cutting position, the free ends of the cutting blades opposite the blade holder of the cutting bar are moved by a predetermined distance relative to the guide comb (i.e. relative to the guide comb). In this case, only the free lengths of the cutting blades protruding from the guide comb change. However, the conveyor track can run adjacent to the guide comb independently of the displacement of the cutting bar, so that cutting always takes place adjacent to the guide comb. As a result, the advance of the cutting bar has essentially no influence on the cutting quality. In a preferred embodiment, the guide comb has a guide surface, in particular a guide plane, for the plastic film formed by the end faces of the guide tines.

[0030] To transfer from the first to the second cutting position, the cutting blades are preferably advanced, i.e., they are pushed further out of the guide comb. This design has the advantage that the cutting blades protrude only slightly from the guide comb at start-up, ensuring safe insertion into the plastic film. Advantageously, lateral swinging or even breakage of the cutting blades at start-up, i.e., when the cutting blades insert into the plastic film, is reliably prevented.

[0031] In a preferred embodiment, the cutting edges have a free length of at least 50 mm, preferably at least 70 mm, in particular at least 110 mm. The term "free length" is understood to mean that part of the cutting edges which is available for cutting the plastic film by actuating the displacement device. For example, cutting blades with a total length of 160 to 200 mm can be provided, with 70 to 90 mm being clamped in the cutting holders of the cutting bar, resulting in a free length of 70 to 130 mm. By changing the holding position of the cutting blades in the blade holder of the cutting bar, the previously clamped part of the cutting blades can also be used for cutting.

[0032] To ensure the cutting blades can be advanced automatically, particularly when the respective cutting points become worn, it is advantageous if the displacement device has a drive mechanism, preferably with a motor, for displacing the cutting bar with the cutting blades. To transfer from the first to the second cutting position, the cutting bar can be moved forward or backward by actuating the motor, thereby pushing the cutting blades further or closer out of the guide comb.

[0033] Preferably, "displacing" means an essentially exactly linear movement of the knife bar. Depending on the design, the knife bar can also be moved in the displacement direction in the first or second cutting position, in particular periodically moved in opposite directions, so that first or second sections of the cutting blades are provided as the first or second cutting points. Meanwhile, the conveyor track can run at the same distance from the guide comb. Furthermore, in the first or second cutting position, in addition to the longitudinal conveyance in the conveying direction, the plastic film can be moved in a direction running normal to the film plane, in particular periodically moved in opposite directions. During this time, the cutting bar can be arranged stationary.

[0034] In a particularly preferred embodiment, a device is provided for detecting the degree of wear of the first or cutting points of the cutting blades. When cutting the plastic film, the cutting blades wear down at the respective cutting point. In this embodiment, the degree of wear of the cutting blades at the respective cutting point is monitored, whereby it is possible to move the cutting blades from the first cutting position to the second cutting position by actuating the displacement device, so that the plastic film is no longer cut with the first cutting points, but with the second cutting points.

[0035] In order to be able to precisely determine the degree of wear during operation of the cutting device, the device is designed in a preferred embodiment to detect cutting resistance when cutting the plastic film with the cutting blades. A change in the cutting resistance changes the torque or moment acting on the blade holder of the cutting bar, which can be measured with a measuring element, for example a pressure measuring cell, in order to detect the degree of wear. When the cutting device is initialized, a maximum value for the permissible cutting resistance due to wear can be set. This maximum value is preferably determined as a function of at least one parameter selected from the respective film width, film thickness, film conveyor speed, and number of cut film strips. If the maximum value is exceeded, the cutting bar can be advanced accordingly.

[0036] In a preferred embodiment, the device for detecting the degree of wear of the cutting blades is connected to the displacement device via a control device, wherein the control device is designed to control the displacement device upon detection of a threshold value for the degree of wear, in particular upon exceeding a predetermined maximum value for the cutting resistance, such that the cutting blades are displaced from the first to the second cutting position. If the wear of the first cutting points exceeds the desired extent, the cutting bar is advanced, whereby the second cutting points are arranged on the conveyor track along which the plastic film is fed. The cutting blades can thus be automatically adjusted depending on the degree of wear in order to ensure the desired cutting quality.

[0037] Depending on the production process (film quality, thickness, speed, etc.), the cutting resistance increases over time due to wear on the cutting blades. Above a certain cutting resistance, the resulting reduced cutting quality can be automatically detected using the pressure measuring cell. To maintain the cutting quality, the cutting blades can be moved from the first to the second cutting position, preferably by at least 2 millimeters (mm), for example from 2 to 4 mm, in particular from 3 to 4 mm.

[0038] The first and second cutting positions are listed above only as minimum requirements for the displacement device. In a preferred embodiment, at least one further cutting position can be approached with the displacement device. In a preferred embodiment, the cutting bar is essentially continuously adjustable between a first and a second final cutting position.

[0039] A ribbon extrusion system according to the invention for producing film ribbons has a machine frame, a cutting device in one of the embodiments described above, and a pivoting device for pivoting the cutting device relative to the machine frame. With the aid of the pivoting device, the cutting device can be pivoted away from the plastic film in order to (temporarily) interrupt the cutting process. Accordingly, the cutting device can be pivoted towards the plastic film by means of the pivoting device so that the cutting edges of the cutting blades penetrate the conveyor track of the plastic film in order to start or continue the cutting process. When pivoted away from the plastic film, the blades can be changed.The device according to the invention for producing film tapes, preferably for use as warp tapes and weft tapes, has a cutting device in one of the embodiments described above.

[0040] A device according to the invention for producing a circular fabric comprises the above device for producing film tapes and a circular loom for weaving a circular fabric from the warp and weft tapes.

[0041] In the method according to the invention for cutting a plastic film into a plurality of film strips, the following step is carried out:

[0042] Moving the cutting blades relative to the guide comb, in particular pushing the cutting blades further out of the guide comb, whereby the cutting edges are transferred from the first to the second cutting position.

[0043] For the advantages of this embodiment, reference is made to the above explanations regarding the cutting device.

[0044] In a preferred embodiment, the following step is also carried out:

[0045] Recording, in particular continuous recording, of the degree of wear of the cutting blades, which is a measure of the sharpness of the cutting edges.

[0046] To determine the degree of wear of the cutting blades, the cutting resistance when cutting the plastic film with the cutting blades is preferably measured.

[0047] In a preferred embodiment, upon detection of a threshold value for the degree of wear, in particular upon exceeding a predetermined maximum value for the cutting resistance, the cutting blades are advanced from the first to the second cutting position, preferably by means of a motor. The invention is further explained below with reference to a preferred embodiment, which is illustrated in the drawings.

[0048] Fig. 1 shows a block diagram to illustrate the production of a circular fabric from warp and weft tapes, whereby a plastic film is produced using an extrusion system, the plastic film is cut into film tapes using a cutting device, the film tapes are stretched into the warp and weft tapes using a stretching system, and finally the circular fabric is woven from the warp and weft tapes using a circular weaving machine.

[0049] Fig. 2 shows an embodiment of the cutting device according to the invention, which for Fig. 1 schematically shows the production of a ribbon fabric 1, in particular a round fabric, from warp ribbons 2 and weft ribbons 3. A flat film, i.e. a plastic film 5, for example from PE-HD or PP, is produced using an extrusion system 4. A cutting device 6 cuts the plastic film 5 into strip-shaped film ribbons 7, which preferably each have a width of 2.5 to 14 millimeters. A stretching system 8 stretches the film ribbons 7, preferably by a factor of 5 to 7, to form the warp ribbons 2 and the weft ribbons 3. The stretching system 8 preferably comprises a hot-air oven in which the film strips 7 are stretched longitudinally in a warm-plastic state. After stretching, the warp and weft strips preferably have a width of 0.8 to 6 mm.The warp and weft tapes can then be wound onto spools (not shown). Finally, the circular fabric can be woven from the warp and weft tapes using a circular weaving machine 9.

[0050] Fig. 2 shows a schematic example of the cutting device 6 for longitudinally cutting the plastic film 5 (shown transparent in Fig. 2 for the sake of clarity) into the film strips 7. The cutting device 6 has a conveyor device 10 (illustrated only with an arrow) for conveying the plastic film 5 along a conveyor track 11. As is known in the prior art, the conveyor device can have a roller arrangement (not shown). In addition, the cutting device 6 has a cutting bar 12 with a blade holder 13 in which a plurality of cutting blades 14 are held. The cutting blades 14 are arranged upright, parallel and preferably with the same transverse distances from one another.Each cutting blade 14 has a straight cutting edge 15 on the longitudinal edge facing the plastic film 5, which extends through the conveyor track 11 so that the cutting edge 15 can cut the plastic film 5 into the film strips 7. Furthermore, the cutting device 6 has a displacement device 16 for advancing the cutting blades 14 from a first cutting position to a second cutting position, in which first cutting points or second cutting points of the cutting edges 15 are arranged on the cutting plane 11. The displacement device 16 has a drive device 17, which effects the advance of the cutting bar 12. The drive device 17 is only symbolically represented in Fig. 2 by spindles with actuating disks. The blade holder 13 of the cutting bar 12 is mounted on the spindles.By rotating the actuating discs, in particular with a motor, the cutting bar 12 moves along the spindles, the longitudinal axes of which form the direction of displacement of the cutting bar 12.

[0051] According to the invention, the cutting device 6 has a guide comb 18 with a plurality of guide prongs 19, each of which projects between two cutting blades 14, so that the cutting blades 14 are guided laterally. By actuating the displacement device 16, the cutting blades 14 can be pushed out of the guide comb 18 to different distances in order to switch between the first and the second cutting position. The guide comb 18 is arranged adjacent to the conveyor track 11, which is in particular a conveyor plane, at which the cutting blades 14 meet the plastic film 5. The cutting edges 15 can have a usable length of at least 110 mm. As shown in Fig. 2 is illustrated schematically, the cutting device 6 can have a device 20 which is designed to determine a degree of wear of the first cutting points in the first cutting position or.of the second cutting points in the second cutting position. The device 20 can have at least one strain gauge 21 which is designed to detect a cutting resistance when cutting the plastic film 5 with the cutting blades 14. For this purpose, for example, a change in the torque can be measured which is applied to the blade holder (and the components firmly connected thereto) when cutting the plastic film 5. The device 20 for detecting the degree of wear of the cutting blades 14 is connected to the displacement device 16 via a control device 22 in such a way that when a threshold value for the degree of wear is detected, in particular when a predetermined maximum value for the cutting resistance is exceeded, the cutting blades 14 can be advanced from the first into the second cutting position.

[0052] As is schematically indicated in Fig. 2, the cutting device 6 can be part of a ribbon extrusion system in which the cutting device 6 can be pivoted about a pivot axis 24 relative to a machine frame (not shown) by means of a pivoting device 23. The pivoting device preferably has a pivot drive. Alternatively, the cutting device 6 can be pivoted manually by means of the pivoting device. With the pivoting device 23, the cutting device 6 can be pivoted towards the conveyor track 11 to start the cutting process or pivoted away from the conveyor track 11 to (temporarily) stop the cutting process. Before the cutting device 6 is pivoted towards the conveyor track 11, the cutting blades 14 are preferably moved into a first end position in which the cutting blades 14 protrude minimally from the guide comb 18.After immersion in the plastic film 5, the cutting blades 14 can be moved by means of the displacement device 16 into the desired cutting position, for example, into a cutting position stored before a machine stop. Reference numbers:.

[0053] 1 round fabric

[0054] 2 warp ribbons

[0055] 3 weft ribbons

[0056] 4 Extrusion line

[0057] 5 plastic film

[0058] 6 Cutting device

[0059] 7 foil ribbons

[0060] 8 Stretching system

[0061] 9 circular loom

[0062] 10 Conveyor system

[0063] 11 Conveyor track

[0064] 12 cutting bars

[0065] 13 Blade holder

[0066] 14 cutting blades

[0067] 15 cutting edges

[0068] 16 Shifting device

[0069] 17 Drive device

[0070] 18 Guide comb

[0071] 19 guide tines

[0072] 20 Device for recording the degree of wear

[0073] 21 strain gauges

[0074] 22 Control device

[0075] 23 Swivel device

[0076] 24 swivel axis

Claims

Claims:

1. Cutting device (6) for cutting a plastic film (5) into a plurality of film strips (7), preferably for Use in the stretched state as warp tapes (2) and weft tapes (3) for feeding to a weaving machine, in particular a circular weaving machine, comprising: a conveyor device (10) for conveying the plastic film (5) along a conveyor track (11), a cutting bar (12) with a plurality of cutting blades (14), each having a cutting edge (15) passing through the conveyor track (11), a displacement device (16) for displacing the cutting blades (14) from a first to a second cutting position, in which the first or second cutting position is arranged.second cutting points of the cutting edges (15) are arranged on the conveyor track (11), characterized by a guide comb (18) with a plurality of guide tines (19) projecting between the cutting blades (14) for laterally guiding the cutting blades (14), wherein the displacement device (16) is designed to displace the cutting blades (14) relative to the guide comb (18) in order to transfer the cutting edges (15) from the first to the second cutting position.

2. Cutting device (6) according to claim 1, characterized in that the guide comb (18) is arranged adjacent to the conveyor track (11).

3. Cutting device (6) according to claim 1 or 2, characterized in that the guide comb (18) is arranged stationary with respect to the displacement of the cutting blades (14).

4. Cutting device (6) according to one of claims 1 to 3, characterized in that the cutting edges (15) have a free length of at least 50 mm, preferably at least 70 mm, in particular at least 90 mm.

5. Cutting device (6) according to one of claims 1 to 4, characterized in that the displacement device (16) has a motor for displacing the cutting bar (12) with the cutting blades (14).

6. Cutting device (6) according to one of claims 1 to 5, characterized by: a device (20) for detecting a degree of wear of the first or cutting points of the cutting blades (14).

7. Cutting device (6) according to claim 6, characterized in that the device (20) is designed to detect a cutting resistance when cutting the plastic film (5) with the cutting blades (14).

8. Cutting device (6) according to claim 6 or 7, characterized in that the device (20) for detecting the degree of wear of the cutting blades (14) is connected to the displacement device (16) via a control device (22), wherein the control device (22) is designed to control the displacement device (16) upon detection of a threshold value for the degree of wear, in particular upon exceeding a predetermined maximum value for the cutting resistance, in such a way that the cutting blades (14) are displaced from the first to the second cutting position.

9. Ribbon extrusion system, comprising: a machine frame, a cutting device (6) according to one of claims 1 to 8 and a pivoting device (23) for pivoting the cutting device (6).

10. Device for producing film tapes (7), preferably for use as warp tapes (2) and weft tapes ( 3 ) , comprising : an extrusion system (4) for producing a plastic film (5), a cutting device (6) according to one of claims 1 to 8 for cutting the plastic film (5) into a plurality of film strips (7), and a stretching system (8) for stretching the film strips (7).

11. Method for cutting a plastic film (5) into a plurality of film strips (7), comprising the steps: Conveying the plastic film (5) along a conveyor track (11), Arranging cutting blades (14) of a cutting bar (12) in a first cutting position in which first cutting points of cutting edges (15) of the cutting blades (14) are arranged on the conveyor track (11), Cutting the plastic film (5) into the plurality of film strips (7) by means of the cutting blades (14) in the first cutting position, Advancing the cutting blades (14) from the first to a second cutting position, in which second cutting points of the cutting edges (15) are arranged on the conveyor track (11), cutting the plastic film (5) into the plurality of film strips (7) by means of the cutting blades (14) in the second cutting position, characterized by guiding the cutting blades (14) with guide teeth (19) of a guide comb (18) projecting between the cutting blades (14) in the first cutting position, Displacing the cutting blades (14) relative to the guide comb (18), in particular advancing the cutting blades (14) further out of the guide comb (18), wherein the cutting edges (15) are transferred from the first to the second cutting position.

12. Method according to claim 11, characterized by: Detecting the degree of wear of the cutting blades (14) .

13. Method according to claim 12, characterized in that in order to detect the degree of wear of the cutting blades (14), a cutting resistance when cutting the plastic film (5) with the cutting blades (14) is detected.

14. Method according to claim 12 or 13, characterized in that when a threshold value for the degree of wear is detected, in particular when a predetermined maximum value for the cutting resistance is exceeded, the cutting blades (14) are advanced from the first to the second cutting position.

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