Inhibition module for the bow deformation of a biaxial stretching process and biaxial stretching apparatus

Abstract

The application discloses a restraining module for preventing arch deformation in a bidirectional stretching process and a bidirectional stretching device, and the restraining module comprises a fixed frame, a power source is installed on the fixed frame, the power source drives the arc surface of an arc roller to rotate, the arc roller can be adjusted to form different arc heights, two sets of expander rollers are arranged on the two sides of the fixed frame, the two sets of expander rollers are located downstream of the arc roller, the two sets of expander rollers have initial angles which are perpendicular to the length of the film, and the two sets of expander rollers can be unfolded and form different unfolding angles relative to the initial angles. The arc height of the arc roller is dynamically adjusted to change the travel of the film along the conveying direction when the film is stretched in the transverse direction, and the unfolding angle of the two sets of expander rollers is dynamically adjusted to generate a forward oblique pulling force on the film, which can effectively offset the arch deformation of the film, reduce the orientation anisotropy of the film at different positions, make the mechanical properties and thermal shrinkage rate of the film uniform, and improve the surface flatness and thickness uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of film processing, in particular to an inhibition module for arch deformation of a biaxial stretching process and a biaxial stretching device. BACKGROUND

[0002] The biaxial stretching process is the core process for preparing biaxial stretching plastic film. The biaxial stretching process mainly includes asynchronous stretching and synchronous stretching. However, no matter asynchronous stretching or synchronous stretching, after the film passes through the transverse stretching machine or the double stretching machine, due to the stretching force received by the clamping position on both sides of the film during transverse stretching, the stretching force is the resultant force of the transverse stretching force and the stretching force in the running direction of the equipment. The direction of the resultant force has a certain inclination with the transverse direction of the film, and is offset to one side along the movement direction of the film. Therefore, the stretching force received by the two sides and the middle region of the film is lagging, which causes the film to produce arch deformation. In particular, in the synchronous stretching, the arch deformation is more prominent.

[0003] As shown in Figure 1 The ink-coated cotton thread is straightened above the thick sheet before the inlet, parallel to the thick sheet, and the arch-shaped film is pulled in the middle of the cotton thread. A straight line is drawn, and after winding, the film is measured to measure the arch deformation d of the straight line. The arch deformation d is to draw a straight line on both sides of the arc, and measure the distance between the maximum bending position and the straight line.

[0004] After the film produces arch deformation, the mechanical strength (such as tensile strength, puncture resistance) is uneven, the heat shrinkage rate is inconsistent, the surface flatness is reduced, the thickness uniformity is decreased, and other defects. The traditional method is to compensate the deformation by adjusting the stretching temperature or speed, but it is limited by the narrow process window, which easily leads to film brittleness or uneven heat shrinkage, and lacks a dynamic adjustment mechanism to offset the deformation in real time. SUMMARY

[0005] The present application aims to provide an inhibition module for arch deformation of a biaxial stretching process to solve one or more technical problems existing in the prior art, and at least provide a beneficial choice or create conditions.

[0006] The inhibition module for arch deformation of a biaxial stretching process according to the first aspect embodiment of the present application takes the length direction of the film as the front-rear direction and the width direction of the film as the left-right direction, and is characterized in that it comprises:

[0007] A fixed frame is located at the outlet of the stretching machine, and the fixed frame is provided with a power source and an arc-shaped roller. The power source drives the arc surface of the arc-shaped roller to rotate, and the arc-shaped roller is used to receive the film coming out of the stretching machine. The two ends of the arc-shaped roller are arranged along the left-right direction and can relatively displace along the left-right direction, so as to adjust the arc-shaped roller to form different arc heights.

[0008] The two sets of expander roller groups are arranged on the two sides of the fixed frame, and are located downstream of the arc-shaped roller. The two sets of expander roller groups have initial angles perpendicular to the front-back direction, and can be expanded towards the conveying direction of the film and form different expansion angles relative to the initial angles. The arc height of the arc-shaped roller is dynamically adjusted to change the travel of the film in the conveying direction during transverse stretching, and the expansion angle of the expander roller group is dynamically adjusted to generate a forward oblique tension on the film

[0009] According to the embodiment of the application, the suppression module for the bow deformation of the biaxial stretching process has at least the following beneficial effects: compared with the prior art, the arc height of the arc-shaped roller is dynamically adjusted to change the travel of the film in the conveying direction during transverse stretching, and the expansion angle of the expander roller group is dynamically adjusted to generate a forward oblique tension on the film. The above improvements can effectively offset the bow deformation of the film, reduce the orientation anisotropy of the film at different positions, make the mechanical properties and thermal shrinkage rate of the film uniform, and improve the surface flatness and thickness uniformity.

[0010] According to some embodiments of the application, the arch height of the arc-shaped roller is the arch height of the arc-shaped roller, and the adjustment range of the arc height is 0-100 mm.

[0011] According to some embodiments of the application, the arc-shaped roller has a high-precision hard alloy arc surface with a roughness of ≤0.1 μm.

[0012] According to some embodiments of the application, the power source is a servo motor, and a tension sensor is arranged on the shaft seat of the arc-shaped roller, and the tension sensor is electrically connected to the servo motor.

[0013] According to some embodiments of the application, each expander roller group comprises an upper roller and a lower roller, and the upper roller and the lower roller are arranged in a spaced manner and jointly form an expander channel.

[0014] According to some embodiments of the application, one end of the expander roller group is rotatably connected to the fixed frame, and the other end of the expander roller group is arranged in an overhead manner.

[0015] According to some embodiments of the application, the expansion angle of the expander roller group is 0-30°, and the expander roller group is provided with a locking mechanism for maintaining the expansion angle.

[0016] According to some embodiments of the application, the fixed frame is further provided with an overexpansion roller, which is located downstream of the expander roller group and is used to increase the wrap angle of the film.

[0017] According to the second aspect of the embodiment of the application, the biaxial stretching device comprises:

[0018] The above-mentioned suppression module for the bow deformation in the biaxial stretching process;

[0019] The stretching machine is provided with a preheating zone, a stretching and retracting zone and a heat setting zone, the preheating zone is provided with an inlet, the heat setting zone is provided with an outlet, and the suppression module is connected to the outlet;

[0020] The traction machine is arranged downstream of the suppression module, and is used to provide a conveying traction force on the film.

[0021] The stretched film according to the third aspect of the present application is produced by the above-mentioned biaxial stretching equipment.

[0022] Additional aspects and advantages of the present application will be in part apparent and in part pointed out below. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above-mentioned and / or additional aspects and advantages of the present application will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, in which:

[0024] Figure 1 is a schematic diagram of the bow line generated in the biaxial stretching process;

[0025] Figure 2 is a top view of the suppression module provided by the embodiment of the present application;

[0026] Figure 3 is a front view of the suppression module provided by the embodiment of the present application;

[0027] Figure 4 is a structural schematic diagram of the arc-shaped roller provided by the embodiment of the present application;

[0028] Figure 5 is a structural schematic diagram of the expansion roller set provided by the embodiment of the present application;

[0029] Figure 6 is a top view of the stretching machine provided by the embodiment of the present application;

[0030] Figure 7 is a structural diagram of the stretching machine provided by the embodiment of the present application.

[0031] In the drawings: 100 - fixed frame, 200 - arc-shaped roller, 300 - expansion roller set, 400 - film, 110 - mounting plate, 500 - power source, 310 - upper roller, 320 - lower roller, 600 - excess roller, 10 - stretching machine, 20 - traction machine, 11 - preheating zone, 12 - stretching and retracting zone, 13 - heat setting zone, 14 - inlet, 15 - outlet. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0034] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0035] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0036] like Figure 2 and Figure 3 As shown, the module for suppressing arc-shaped deformation in a biaxial stretching process according to a first aspect embodiment of the present invention includes a fixed frame 100, an arc-shaped roller 200, and an expanding roller group 300. The fixed frame 100 is located at the outlet of the stretching machine 10. After the stretching machine 10 stretches the film 400, the film 400 is discharged from the discharge port 15 of the stretching machine 10. The fixed frame 100 is fixed in position and has two mounting plates 110 on both sides. The arc-shaped roller 200 is mounted on both mounting plates 110. A power source 500 is mounted on one of the mounting plates 110. In this embodiment, the power source 500 can be a servo motor. The main shaft of the servo motor drives the arc surface of the arc-shaped roller 200 to rotate. For ease of description, the length direction of the film 400 is taken as the front-back direction, and the width direction of the film 400 is taken as the left-right direction. The two mounting plates 110 are located on the left and right sides, respectively, and the two ends of the mandrel of the arc-shaped roller 200 are arranged along the left-right direction.

[0037] Specifically, the arc-shaped roller 200 is shaped as an arc, which gradually arches towards the middle position, and the shaft of the arc-shaped roller 200 is connected to the two side mounting plates 110 respectively, a plurality of bearings are arranged between the roller surface of the arc-shaped roller 200 and the shaft, the roller surface of the arc-shaped roller 200 is composed of a plurality of sleeve tubes, the roller surface of the arc-shaped roller 200 is kept relative rotation with the shaft through the bearings, and the servo motor drives the roller surface to rotate through a belt or other transmission mechanism. The shaft of the arc-shaped roller 200 is not a rigid body, but has a certain toughness, so that the two ends of the shaft of the arc-shaped roller 200 can relatively displace in the left-right direction, and the arc-shaped roller 200 is adjusted to form different arc heights by adjusting the screw rod.

[0038] As shown in Figure 4 , the arch height of the arc-shaped roller 200 is taken as the arc height H. When the film 400 is pulled out from the discharge port 15 of the stretching machine 10, the film 400 is immediately received by the arc-shaped roller 200, and the film 400 also presents a working condition of arching in the middle due to the shape and structure of the arc-shaped roller 200.

[0039] The arc-shaped roller 200 adopts a high-precision hard alloy roller surface, which can be optionally coated with a ceramic coating on the surface, and the surface roughness is less than or equal to 0.1 μm, so as to ensure that the contact surface with the film 400 has no scratches and the friction coefficient is stable. Moreover, the arc height of the arc-shaped roller 200 is adjustable in the range of 0 to 100 mm, so as to adapt to the film 400 with a thickness in the range of 8 μm to 50 μm. The arc height of the arc-shaped roller 200 can be manually controlled or electrically controlled by an electric drive device. In the present embodiment, since the arc height of the arc-shaped roller 200 does not need to be frequently adjusted during normal production, the arc height of the arc-shaped roller 200 is selected to be controlled in a manual manner.

[0040] In addition, a tension sensor (not shown in the figure) is arranged on the shaft seat of the arc-shaped roller 200, which is used to detect the tension of the film 400 when passing through the arc-shaped roller 200. The tension sensor is electrically connected with the servo motor. When the tension of the film 400 is detected to exceed the control value, the servo motor drives the roller surface of the arc-shaped roller 200 to adaptively adjust the speed, so as to keep the tension of the film 400 within the control value range.

[0041] Although the servo motor is not the only choice of the power source 500, considering the control accuracy and other factors, the power source 500 of the present application is preferably a servo motor.

[0042] As shown in Figure 3 and Figure 5As shown, two sets of expander roller groups 300 are provided, and the two sets of expander roller groups 300 are respectively installed on the two side mounting plates 110 of the fixed frame 100, and are arranged in pairs and located downstream of the arc-shaped roller 200. When the film 400 passes through the arc-shaped roller 200, the width edges thereof are received by the two sets of expander roller groups 300. One end of each set of expander roller groups 300 is rotatably connected to the corresponding mounting plate 110, and the other end of each set of expander roller groups 300 is arranged in the air, and each set of expander roller groups 300 has a relatively short length and only exerts force on the width edges of the film 400.

[0043] Specifically, each set of expander roller groups 300 includes an upper roller 310 and a lower roller 320, and the upper roller 310 and the lower roller 320 are arranged in a spaced manner and jointly form an expander channel for the film 400 to pass through. Each set of expander roller groups 300 has an initial angle perpendicular to the front-rear direction, and since one end of each set of expander roller groups 300 is rotatably connected to the corresponding mounting plate 110, each set of expander roller groups 300 can be unfolded towards the conveying direction of the film 400, and at this time, each set of expander roller groups 300 forms a different unfolding angle θ relative to the initial angle. In order to avoid each set of expander roller groups 300 being unfolded in the opposite direction of the conveying direction of the film 400, a limiting manner can be used to achieve this, and each set of expander roller groups 300 is provided with a locking mechanism (not shown in the figure) for maintaining the unfolding angle, so as to prevent each set of expander roller groups 300 from being unfolded to a larger angle under the conveying force of the film 400. The unfolding angle of each set of expander roller groups 300 can be manually controlled or electrically controlled by an electric drive device. In the present embodiment, since each set of expander roller groups 300 does not need to be frequently adjusted in the normal production, the unfolding angle of each set of expander roller groups 300 is selected to be controlled in a manual manner, and the unfolding angle of each set of expander roller groups 300 is 0-30°.

[0044] With the above structure, when the film 400 of the stretching machine 10 is discharged from the discharge port 15, the film 400 first contacts the arc-shaped roller 200 and is subjected to the force of the arc-shaped roller 200, and the travel of the film 400 in the conveying direction during transverse stretching is changed by dynamically adjusting the arc height of the arc-shaped roller 200. After the film 400 passes through the arc-shaped roller 200, the width edges thereof are affected by the two sets of expander roller groups 300, and the two sets of expander roller groups 300 can prevent the film 400 from being wrinkled due to uneven tension, guide the film 400 to be uniformly unfolded, and generate a diagonal forward tension on the film 400 by dynamically adjusting the unfolding angle of the two sets of expander roller groups 300. In combination with the dynamic adjustment of the arc-shaped roller 200 and the dynamic adjustment of the two sets of expander roller groups 300, the bow deformation of the film 400 is effectively offset, the orientation anisotropy of the film 400 at different positions is reduced, the mechanical properties and thermal shrinkage rate of the film 400 are uniform, and the surface flatness and thickness uniformity of the film 400 are improved.

[0045] Further, the two side mounting plates 110 of the fixing frame 100 are also provided with an overstretching roller 600, which is located downstream of the stretching roller group 300 and has a rotating axis arranged along the left-right direction. The overstretching roller 600 is used to increase the wrapping angle of the film 400, to ensure that the film 400 is in full contact with the arc-shaped roller 200, and to avoid slipping.

[0046] In actual application, the bow deformation d is measured multiple times at the film 400 discharge position, and the arc height H of the arc-shaped roller 200 is adjusted according to the test data. When the deformation rate η (calculated formula: η = d / L) ≤ 0.01, the corresponding parameters are recorded as the process reference value, wherein L is the transverse width of the film 400. The opening angle θ of the stretching roller group 300 is adjusted synchronously, and a 1° progressive adjustment method is adopted until the film 400 is flat and wrinkle-free after passing through the roller surface, and the standard process parameters of the formula are finally determined and recorded.

[0047] Under the conditions of different production speeds, different product thicknesses, and different transverse stretching ratios of the normally operating bidirectional stretching equipment, the arc height H of the arc-shaped roller 200 and the opening angle θ of the stretching roller group 300 are adjusted, and the bow deformation test method in the background art is used to make a comparative case test with the existing scheme, and the data results are shown in Tables I and II.

[0048]

[0049] Table I: Bow deformation d under different conditions

[0050] From Table I, it can be seen that the smaller the thickness of the film 400, the slower the production line speed, the larger the stretching ratio, and the larger the bow deformation d. By increasing the arc height H of the arc-shaped roller 200, the bow deformation d is significantly reduced.

[0051]

[0052]

[0053] Table II: Opening angle θ corresponding to the bow deformation d under different conditions

[0054] The performance of the film 400 produced by the film 400 with a thickness δ = 8 μm in Table I under different arc heights H of the arc-shaped roller 200 is analyzed, and the results are shown in Table III, wherein the tensile strength and thickness are in accordance with the GB / T 1040.3-2006 standard, and the shrinkage rate is in accordance with the GB / T 12027-2004 standard.

[0055]

[0056] Table III: Performance comparison of 8 μm film in different schemes

[0057] From the data in Table III, it can be seen that by reducing the bow deformation, the mechanical properties, thermal shrinkage, and thickness uniformity of the film 400 are all improved.

[0058] As shown in Figure 2 , Figure 6 and Figure 7 , the bidirectional stretching equipment according to the second aspect embodiment of the present application comprises the suppression module for bow deformation in the bidirectional stretching process according to the first aspect embodiment of the present application described above, and further comprises a stretcher 10 and a traction machine 20, wherein the suppression module is connected between the stretcher 10 and the traction machine 20. The stretcher 10 can realize the stretching of the film 400 in the length direction and the width direction, i.e. the stretcher 10 can realize the bidirectional stretching of the film 400. The traction machine 20 provides traction for the conveying of the film 400.

[0059] Specifically, the stretcher 10 is provided with a preheating zone 11, a stretching and retracting zone 12, and a heat setting zone 13, the preheating zone 11 is provided with an inlet 14, and the heat setting zone 13 is provided with an outlet 15. The film 400 does not undergo any stretching in the preheating zone 11, when the film 400 enters the front position of the stretching and retracting zone 12, the film 400 sequentially undergoes the processes of transverse stretching + longitudinal invariance, transverse + longitudinal synchronous stretching; then, the film 400 enters the rear position of the stretching and retracting zone 12, the film 400 sequentially undergoes the processes of transverse retraction + longitudinal invariance, transverse retraction + longitudinal stretching, transverse invariance + longitudinal stretching; finally, the film 400 enters the heat setting zone 13, the film 400 sequentially undergoes the processes of transverse invariance + longitudinal invariance and transverse invariance + longitudinal retraction, and is finally output to the outlet 15 and received by the arc-shaped roller 200.

[0060] Since the bidirectional stretching equipment adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0061] The stretched film according to the third aspect embodiment of the present application is produced by the bidirectional stretching equipment according to the second aspect embodiment of the present application described above.

[0062] Since the stretched film adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0063] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application.

Claims

1. A module for suppressing bow deformation for a biaxial stretching process, taking the length direction of a film (400) as the front-rear direction and taking the width direction of the film (400) as the left-right direction, characterized by, The application relates to a stretching machine for realizing stretching of a film in a length direction and a width direction. The stretching machine comprises a fixed frame (100) located at an outlet of a stretching machine (10), wherein the stretching machine (10) is used for realizing stretching of a film (400) in a length direction and a width direction, the fixed frame (100) is provided with a power source (500) and an arc-shaped roller (200), the power source (500) drives the arc surface of the arc-shaped roller (200) to rotate, and the arc-shaped roller (200) is used for receiving the film (400) from the stretching machine (10); the two ends of the arc-shaped roller (200) are arranged along a left-right direction and can be relatively displaced along the left-right direction, so that the arc-shaped roller (200) is adjusted to form different arc heights. The stretching machine further comprises two sets of expansion roller groups (300), the two sets of expansion roller groups (300) are respectively arranged on the two sides of the fixed frame (100), the two sets of expansion roller groups (300) are located downstream of the arc-shaped roller (200), the two sets of expansion roller groups (300) have initial angles which are perpendicular to a front-rear direction, the two sets of expansion roller groups (300) can be expanded towards the conveying direction of the film (400) and form different expansion angles relative to the initial angles; the arc height of the arc-shaped roller (200) is dynamically adjusted to change the travel of the film (400) in the conveying direction during transverse stretching, and the expansion angle of the two sets of expansion roller groups (300) is dynamically adjusted to generate a forward oblique tensile force on the film (400).

2. The arch deformation suppression module for a two-way stretching process according to claim 1, characterized in that: The arc height is the arch height of the arc-shaped roller (200), and the adjustment range of the arc height is 10mm to 100mm.

3. The arch deformation suppression module for a two-way stretching process according to claim 1 or 2, characterized in that: The arc-shaped roller (200) has a high-precision hard alloy arc surface with a roughness of less than or equal to 0.1 microns.

4. The arch deformation suppression module for a two-way stretching process of claim 1, wherein: The power source (500) is a servo motor, a tension sensor is arranged on the shaft seat of the arc-shaped roller (200), and the tension sensor is electrically connected with the servo motor.

5. The arch deformation suppression module for a two-way stretching process of claim 1, wherein: Each of the two sets of expansion roller groups (300) comprises an upper roller (310) and a lower roller (320), the upper roller (310) and the lower roller (320) are arranged in a spaced mode and jointly form an expansion channel.

6. The arch deformation suppression module for a two-way stretching process according to claim 5, characterized in that: One end of each of the two sets of expansion roller groups (300) is rotationally connected to the fixed frame (100), and the other end of each of the two sets of expansion roller groups (300) is arranged in a suspended mode.

7. The arch deformation suppression module for a two-way stretching process according to claim 6, characterized in that: The expansion angle of each of the two sets of expansion roller groups (300) is 6 to 30 degrees, and each of the two sets of expansion roller groups (300) is provided with a locking mechanism for maintaining the expansion angle.

8. The arch deformation suppression module for a two-way stretching process of claim 1, wherein: The fixed frame (100) is further provided with an overstretching roller (600), the overstretching roller (600) is located downstream of the two sets of expansion roller groups (300), and the overstretching roller (600) is used for increasing the wrap angle of the film (400).

9. A bidirectional stretching apparatus characterized by, The application relates to a stretching machine for realizing stretching of a film in a length direction and a width direction. The stretching machine comprises a fixed frame (100) located at an outlet of a stretching machine (10), wherein the stretching machine (10) is used for realizing stretching of a film (400) in a length direction and a width direction, the fixed frame (100) is provided with a power source (500) and an arc-shaped roller (200), the power source (500) drives the arc surface of the arc-shaped roller (200) to rotate, and the arc-shaped roller (200) is used for receiving the film (400) from the stretching machine (10); the two ends of the arc-shaped roller (200) are arranged along a left-right direction and can be relatively displaced along the left-right direction, so that the arc-shaped roller (200) is adjusted to form different arc heights. The stretching machine further comprises two sets of expansion roller groups (300), the two sets of expansion roller groups (300) are respectively arranged on the two sides of the fixed frame (100), the two sets of expansion roller groups (300) are located downstream of the arc-shaped roller (200), the two sets of expansion roller groups (300) have initial angles which are perpendicular to a front-rear direction, the two sets of expansion roller groups (300) can be expanded towards the conveying direction of the film (400) and form different expansion angles relative to the initial angles; the arc height of the arc-shaped roller (200) is dynamically adjusted to change the travel of the film (400) in the conveying direction during transverse stretching, and the expansion angle of the two sets of expansion roller groups (300) is dynamically adjusted to generate a forward oblique tensile force on the film (400). The arc height is the arch height of the arc-shaped roller (200), and the adjustment range of the arc height is 10mm to 100mm. The arc-shaped roller (200) has a high-precision hard alloy arc surface with a roughness of less than or equal to 0.1 microns. The power source (500) is a servo motor, a tension sensor is arranged on the shaft seat of the arc-shaped roller (200), and the tension sensor is electrically connected with the servo motor. Each of the two sets of expansion roller groups (300) comprises an upper roller (310) and a lower roller (320), the upper roller (310) and the lower roller (320) are arranged in a spaced mode and jointly form an expansion channel. One end of each of the two sets of expansion roller groups (300) is rotationally connected to the fixed frame (100), and the other end of each of the two sets of expansion roller groups (300) is arranged in a suspended mode. The expansion angle of each of the two sets of expansion roller groups (300) is 6 to 30 degrees, and each of the two sets of expansion roller groups (300) is provided with a locking mechanism for maintaining the expansion angle. The fixed frame (100) is further provided with an overstretching roller (600), the overstretching roller (600) is located downstream of the two sets of expansion roller groups (300), and the overstretching roller (600) is used for increasing the wrap angle of the film (400). The application relates to a stretching machine for realizing stretching of a film in a length direction and a width direction. The stretching machine comprises a fixed frame (100) located at an outlet of a stretching machine (10), wherein the stretching machine (10) is used for realizing stretching of a film (400) in a length direction and a width direction, the fixed frame (100) is provided with a power source (500) and an arc-shaped roller (200), the power source (500) drives the arc surface of the arc-shaped roller (200) to rotate, and the arc-shaped roller (200) is used for receiving the film (400) from the stretching machine (10); the two ends of the arc-shaped roller (200) are arranged along a left-right direction and can be relatively displaced along the left-right direction, so that the arc-shaped roller (200) is adjusted to form different arc heights. A traction machine (20) is provided downstream of the suppression module, the traction machine (20) being configured to provide a transport traction force to the film (400).

10. A stretched film, characterized by, The stretched film is produced by the bidirectional stretching apparatus of claim 9.

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