Longitudinal stretching device capable of adjusting stretching gap and stretching method

Abstract

The invention discloses a longitudinal stretching device capable of adjusting a stretching gap and a stretching method, and belongs to the field of film stretching. The longitudinal stretching device capable of adjusting the stretching gap sequentially comprises a main body frame, a movable frame, a lifting machine assembly and a stretching roller set from bottom to top. The lifting machine assembly comprises a mounting base, a lifting machine, a coupler, a connecting rod, a speed reducer, a motor and a linear guide rail. And the movable frame is driven by the elevator to do linear motion along the linear guide rail. The movable frames are arranged on the main body frame, the movable frames and the lifters are connected together through the linear guide rails, the lifters drive the movable frames to move along the linear guide rails, the movable frames on the left side and the right side can move synchronously, and the linear guide rails are obliquely installed on the main body frame and the movable frames; the moving frame can move up and down and left and right at the same time.

Description

Technical Field

[0001] The invention relates to the field of film stretching, and in particular to a longitudinal stretching device and a stretching method with adjustable stretching gap. Background Art

[0002] As the core equipment in the film manufacturing process, the longitudinal stretching machine has been widely used and continuously developed in the field of plastic processing in recent years. It has achieved a significant improvement in film performance by accurately controlling process parameters such as stretching speed, temperature and stretching ratio. During the longitudinal stretching process, the film is heated by the preheating roller, then longitudinally stretched by the stretching roller, and finally cooled and shaped on the cooling roller. The longitudinal stretching machine occupies a small area, has high speed control accuracy, and has an adjustable spacing between stretching rollers. The speed of each roller can be adjusted independently, and the whole machine can also be controlled synchronously, making the stretching process controllable.

[0003] For example, patent CN112026153A discloses a longitudinal film stretching machine, including a frame, on which a preheating station, a stretching station, and a shaping station are arranged in sequence, each station is provided with a plurality of working roller assemblies, the stretching roller assembly is provided with a rotating connection frame, and the stretching roller is driven up and down by a lifting mechanism, one of the stretching rollers can adjust the wrap angle between the film and the stretching roller, and the frame is also provided with a holding assembly for making the film fit. The structure described in the patent is complex, inconvenient for installation and maintenance, and the instability of the frame structure is easy to cause vibration of the roller assembly during operation.

[0004] In the existing longitudinal stretching machines, the driving method of the stretching roller group is mostly to install a group of reduction motors and universal couplings on each stretching roller, or to connect the stretching roller group to the reduction motor through a high-power motor, but this structure occupies a large space, has a complex structure, and is difficult to repair and maintain. At the same time, the position of the stretching roller group in the film longitudinal stretching machine is fixed and cannot be adjusted, which makes the longitudinal stretching machine unable to be adjusted according to the differences in film materials during use, limiting the flexibility of the longitudinal stretching machine.

[0005] In summary, the longitudinal stretching machine has a large structure during the film stretching process, is inconvenient to maintain or operate, is easy to damage, and the position of the roller groups in the stretching machine is fixed and cannot be adjusted at any time according to production needs, which is still an urgent problem to be solved. Summary of the invention

[0006] In view of the above problems, the present invention provides a longitudinal stretching device and stretching method with adjustable stretching gap. By setting a movable frame, the roller group is set as a movable roller group to meet the production process requirements of different films and facilitate installation and maintenance.

[0007] The present invention provides a longitudinal stretching device with adjustable stretching gap, which comprises a main frame, a moving frame, a lifting assembly and a stretching roller group from bottom to top; The mobile frame is installed on the main frame through a lifting assembly, and the stretching roller group is installed on the main frame and the mobile frame; The elevator assembly includes a mounting seat, an elevator, a coupling, a connecting rod, a reducer, a motor and a linear guide; The stretching roller group includes a fixed roller group and a movable roller group, the fixed roller group is installed on the main frame, and the movable roller group is installed on the movable frame; The mounting seat is mounted on the main frame, the lifter is mounted on the mounting seat, and the lifter is connected to the mobile frame to drive the mobile frame to move up and down; The linear guide rail connects the main frame and the moving frame. The moving frame moves in a straight line along the linear guide rail and is driven by the elevator. The linear guide rail is installed at an angle.

[0008] Furthermore, the angle between the side of the linear guide rail close to the main frame and the horizontal is 60-65°.

[0009] Furthermore, the linear guide rail is divided into a guide rail and a slider.

[0010] Furthermore, the main frame is a rectangular frame structure, and the main frame includes support plates and fixing rods on left and right sides.

[0011] Furthermore, the fixing rod spans between the left and right support plates, and both ends of the fixing rod are fixed to the left and right support plates of the main frame by bolts, and the left and right support plates are arranged in parallel and symmetrically.

[0012] Furthermore, height adjustment bolts are symmetrically installed at the four corners of the bottom of the main frame and inside and outside.

[0013] Furthermore, the height adjustment bolt is used to adjust the height of the main frame, the height adjustment bolt is a coarse thread structure, and is provided with a nut base, and the nut base is installed on the base plate.

[0014] Furthermore, the mobile frame is divided into left and right sides, and the support plates on the left and right sides of the main frame are symmetrically provided with grooves adapted to the size of the mobile frame, and the mobile frame is symmetrically nested in the support plates on the left and right sides of the main frame.

[0015] Furthermore, the movable frame is divided into an upper roller group part and a lower lifting part.

[0016] Furthermore, a mounting plate is protruding from one side of the lifting part, and the mounting plate is fixed to the sliding block by bolts.

[0017] Furthermore, supporting plates are symmetrically protruding from the outer walls of the supporting plates on both sides of the main frame, and are used to support and install the guide rails.

[0018] Furthermore, a limiting device is provided at the bottom of the lifting part to limit the collision or contact between the moving frame and the main frame.

[0019] Furthermore, the limiting device is installed on the lifting part, in the opposite direction to the sliding block.

[0020] Furthermore, the limiting device is a fixing bolt or a fixing plate.

[0021] Furthermore, the main frame and the roller group part of the movable frame are both provided with circular holes adapted to the diameter of the roller drive shaft, and the top of the circular hole is an open structure, forming a "semi-enclosed" slot for installing the roller.

[0022] Furthermore, the movable roller group is installed in the circular hole of the movable frame through bearings and bushings, and the fixed roller group is installed in the circular hole of the main frame through bearings and bushings. The outer rings of the transmission shaft bearings of the rollers in the movable roller group and the fixed roller group fit tightly with the circular hole walls, and the inner rings are firmly connected to the roller transmission shafts.

[0023] Furthermore, the rollers in the movable roller group and the fixed roller group are parallel and arranged alternately up and down.

[0024] Furthermore, oil receiving pans are symmetrically installed at the transmission shafts at both ends of the rollers of the movable roller group and the fixed roller group. The oil receiving pans are fixedly installed on the bearing seats at both ends of the rollers in the movable roller group and the fixed roller group by bolts, and are used to collect oil droplets when the rollers in the movable roller group and the fixed roller group are working.

[0025] Furthermore, the mounting seat is symmetrically mounted on the support plates on the left and right sides of the main frame, located below the mobile frame, and parallel to the bottom edge of the mobile frame.

[0026] Furthermore, the installation direction of the mounting seat on the movable frame is opposite to the installation direction of the guide rail.

[0027] Furthermore, a lift is installed on the mounting seat, and the lift is rigidly connected to the mounting seat by bolts. The interior of the lift is a worm gear and screw structure, which utilizes the worm gear meshing and screw nut transmission principle to convert the horizontal rotation output force of the motor into vertical lifting thrust.

[0028] Furthermore, the lift is fixedly connected to the movable frame and is arranged parallel to the linear guide rail.

[0029] Furthermore, the connecting rod spans across the main frame, and both ends are connected to the elevators. The elevators are at both ends of the main frame and synchronously drive the movable frame to move along the linear guide rail.

[0030] Furthermore, the coupling is installed at both ends of the connecting rod, and is located on one side of the inner wall of the support plates on the left and right sides.

[0031] Furthermore, the motor is installed outside the elevator on one side and is electrically connected to the elevator.

[0032] Furthermore, the reducer is installed between the motor and the elevator.

[0033] Furthermore, one side of the fixed roller group is a film inlet side, and the side of the movable roller group is a film outlet side.

[0034] Furthermore, the vertical distance between the centers of the fixed roller group and the rollers in the movable roller group is 50-100 mm, and the horizontal distance between the centers of the rollers is 150-300 mm.

[0035] Furthermore, the upper and lower movement limits of the movable frame are 80-90 mm, and the left and right movement limits are 40-50 mm.

[0036] Furthermore, each roller in the fixed roller group and the movable roller group is equipped with a transmission motor.

[0037] The present invention also provides a method for stretching a film using the longitudinal stretching device with adjustable stretching gap, comprising the following steps: Step 1, adjusting the elevator by a motor in the longitudinal stretching device with adjustable stretching gap, driving the movable frame to move to a preset position in the longitudinal stretching device with adjustable stretching gap; Step 2, stretching the film from the inlet side of the longitudinal stretching device with adjustable stretching gap to the longitudinal stretching device with adjustable stretching gap in an alternating manner, and winding it around the fixed roller group and the movable roller group in sequence; Step 3: repeatedly adjust the movable frame until the production requirements are met, and after the adjustment is completed, enter the next process section of the film.

[0038] Furthermore, the upper and lower movement limits of the movable frame in step 1 are 80-90 mm, and the left and right movement limits are 40-50 mm.

[0039] Furthermore, in the step 2, the rotational speed of the rollers in the fixed roller group is 0-250r / min, 0-250r / min and 0-850r / min from the side where the film enters; the rotational speed of the rollers in the movable roller group is 0-1100r / min, 0-1100r / min and 0-1100r / min from the side where the film enters.

[0040] Furthermore, in step 3, the film is stretched by 1-7 times.

[0041] Beneficial effects of the present invention: 1. The rollers of conventional longitudinal stretching devices are all fixed rollers, and the distance between the roller groups is not adjustable, so the stretching distance cannot be adjusted according to different production requirements. However, the present invention sets a mobile frame on the main frame, connects the mobile frame through a linear guide and an elevator, and drives the mobile frame to move along the linear guide by the elevator. The elevator and the linear guide are installed on both sides of the main frame, so that the mobile frames on the left and right sides can move synchronously to ensure the consistency during the film stretching process. The elevators on both sides are connected by a connecting rod, which also ensures the synchronous movement of the elevators on both sides. In addition, the linear guide in the present invention is obliquely installed on the main frame and the mobile frame, so that the mobile frame can simultaneously realize the movement in the up and down and left and right directions; 2. The present invention also installs height-adjustable bolts at the bottom of the main frame, so that the height of the device can be adjusted at any time. The present invention also installs a limit device at the bottom of the mobile frame to prevent the mobile frame from colliding with the main frame uncontrollably when the elevator is damaged. The present invention realizes the free movement of the roller group through a simple elevator and a linear guide rail, and stretches the film through the different rotation speeds between each roller group. The device in the present invention can adapt to films of different materials and different process requirements, has high stretching efficiency and high applicability, and is suitable for the production of stretching processes in various industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural schematic diagram of the longitudinal stretching device with adjustable stretching gap in the present invention; Figure 2 A side view of a belt roller group of the longitudinal stretching device with adjustable stretching gap in the present invention; Figure 3 It is a side view of the longitudinal stretching device with adjustable stretching gap without roller group described in the present invention; Figure 4 It is a schematic diagram of a movable frame of the longitudinal stretching device with adjustable stretching gap in the present invention; Figure 5 A side view of an elevator assembly of the longitudinal stretching device with adjustable stretching gap according to the present invention; Figure 6 A schematic diagram of an elevator assembly of the longitudinal stretching device with adjustable stretching gap according to the present invention; The names of the numbers in the figure are: 1. Main frame; 2. Mobile frame; 3. Mounting seat; 4. Lifter; 5. Coupling; 6. Connecting rod; 7. Reducer; 8. Motor; 9. Linear guide; 10. Fixed roller group; 11. Mobile roller group; 201. Roller group part; 202. Lifting part. DETAILED DESCRIPTION

[0043] The invention is described in detail below with reference to the embodiments: The invention provides a longitudinal stretching device and a stretching method with adjustable stretching gap, which greatly improves the adaptability to various films or process conditions through the arrangement of a stretchable roller group.

[0044] Example 1 This embodiment provides a longitudinal stretching device with adjustable stretching gap, which comprises a main frame 1, a moving frame 2, a lifting assembly and a stretching roller group from bottom to top; The mobile frame 2 is installed on the main frame 1 through a lifting assembly, and the stretching roller group is installed on the main frame 1 and the mobile frame 2; The elevator assembly includes a mounting seat 3, an elevator 4, a coupling 5, a connecting rod 6, a reducer 7, a motor 8 and a linear guide 9; The stretching roller group includes a fixed roller group 10 and a movable roller group 11, wherein the fixed roller group 10 is installed on the main frame 1, and the movable roller group 11 is installed on the movable frame 2; The mounting seat 3 is mounted on the main frame 1, the lifter 4 is mounted on the mounting seat 3, and the lifter 4 is connected to the mobile frame 2 to drive the mobile frame 2 to move up and down; The linear guide rail 9 connects the main frame 1 and the moving frame 2. The moving frame 2 moves linearly along the linear guide rail 9 and is driven by the elevator 4. The linear guide rail 9 is installed at an angle.

[0045] In this embodiment, the angle between the side of the linear guide rail 9 close to the main frame 1 and the horizontal is 63°. The inclined linear guide rail 9 can change the direction of force. When the mobile frame 2 moves along the linear guide rail 9 under the action of the elevator 4, the decomposition of the force makes it possible to have components in the direction perpendicular to the guide rail and in the horizontal direction. The component in the vertical direction helps to stably lift or lower the mobile frame 2, while the component in the horizontal direction can offset the lateral tension generated by the material during the stretching process, thereby avoiding position displacement of the stretching roller group due to the lateral force. Secondly, the setting of the inclination angle makes the device more reasonable in space utilization. Compared with the vertically or horizontally installed guide rails, this inclination angle can increase the moving stroke of the mobile frame 2 without increasing the footprint of the device, thereby expanding the adjustment range of the stretching gap and being able to adapt to the stretching requirements of more types of materials. The linear guide rail 9 is divided into a guide rail and a slider; The main frame 2 is a rectangular frame structure, and the main frame 1 includes support plates and fixing rods on the left and right sides; The fixing rod spans between the support plates on the left and right sides, and both ends of the fixing rod are fixed to the support plates on the left and right sides of the main frame by bolts, and the support plates on the left and right sides are arranged in parallel and symmetrically; The main frame 1 is symmetrically installed with height adjustment bolts at the four corners of the bottom and inside and outside. By adjusting the height adjustment bolts, the levelness of the main frame 1 can be accurately adjusted. In the initial stage of device installation, the ground may be uneven. The main frame 1 can be kept level by using the height adjustment bolts, which provides a good foundation for the subsequent lifting and lowering of the mobile frame 2 and the normal operation of the fixed roller group 10 and the mobile roller group 11. The height adjustment bolts are symmetrically installed at the inside and outside positions of the four corners of the bottom, which can provide more uniform support force; The height adjustment bolt is used to adjust the height of the main frame 1. The height adjustment bolt is a coarse thread structure and is provided with a nut base, which is mounted on the base plate. The mobile frame 2 is divided into left and right sides, and the support plates on the left and right sides of the main frame 1 are symmetrically provided with grooves adapted to the size of the mobile frame 2, and the mobile frame 2 is symmetrically nested on the support plates on the left and right sides of the main frame 1; The mobile frame 2 is divided into an upper roller group part 201 and a lower lifting part 202; A mounting plate is protruding from one side of the lifting part 202, and the mounting plate is fixed to the slider by bolts; The support plates on both sides of the main frame 1 are symmetrically protruded from the outer walls of the support plates, and are provided with supporting plates for supporting and installing the guide rails; A limiting device is also provided at the bottom of the lifting part 202, which is used to limit the collision or contact between the mobile frame 2 and the main frame 1. The limiting device can effectively prevent the mobile frame 2 from colliding with the main frame 1 due to the failure of the elevator 4 or program error during the lifting process of the mobile frame 2, thereby damaging the frame structure, affecting the accuracy of the stretching roller group, or affecting the stretching effect; The limiting device is installed on the lifting part 202, in the opposite direction to the sliding block; The limiting device is a fixing bolt; The main frame 1 and the roller group part 201 of the mobile frame 2 are both provided with round holes adapted to the diameter of the roller drive shaft, and the top of the round hole is an open structure, forming a "semi-enclosed" type slot for installing the roller. The "semi-enclosed" slot is convenient for installing the roller, and is simpler than the traditional completely closed or complex installation structure, greatly improving the installation efficiency and reducing the damage to the roller and the slot that may be caused during the installation process. At the same time, when the roller needs to be repaired, cleaned or replaced, the operator can easily contact the roller from above, and the close fit between the round hole and the roller drive shaft can effectively prevent the roller from moving in the horizontal direction, ensuring the stability of the position of the roller during the working process; The movable roller group 11 is installed in the circular hole of the movable frame 2 through a bearing and a sleeve, and the fixed roller group 10 is installed in the circular hole of the main frame 1 through a bearing and a sleeve. The outer rings of the transmission shaft bearings of the rollers in the movable roller group 11 and the fixed roller group 10 fit tightly with the circular hole wall, and the inner rings are firmly connected to the roller transmission shaft; The rollers in the movable roller group 11 and the fixed roller group 10 are arranged in parallel and alternately up and down; Oil receiving pans are symmetrically installed at the transmission shafts at both ends of the rollers of the movable roller group 11 and the fixed roller group 10. The oil receiving pans are fixedly installed on the bearing seats at both ends of the rollers of the movable roller group 11 and the fixed roller group 10 by bolts, and are used to receive oil drops when the rollers of the movable roller group 11 and the fixed roller group 10 are working; The mounting seat 3 is symmetrically mounted on the support plates on the left and right sides of the main frame 1, located below the mobile frame 2 and parallel to the bottom edge of the mobile frame 2. Since the lifter 4 and the linear guide rail 9 are arranged in parallel, precise control can be achieved when adjusting the stretching gap. The parallel structure helps to accurately determine the position of the mobile frame 2, thereby accurately adjusting the gap between the fixed roller group 10 and the mobile roller group 11. At the same time, the fixed connection between the lifter 4 and the mobile frame 2 can effectively transfer the force generated by the lifter 4 to the mobile frame 2. In the process of lifting or lowering the mobile frame 2, the force can be evenly distributed along the direction of the linear guide rail 9, reducing the generation of lateral force, which helps to protect the various components of the device, reduce the possibility of wear and damage, and also ensure the service life and reliability of the device; The installation direction of the mounting seat 3 on the mobile frame 2 is opposite to the installation direction of the guide rail; The mounting base 3 is provided with an elevator 4, which is rigidly connected to the mounting base 3 by bolts. The interior of the elevator 4 is a worm-screw structure, which utilizes the worm-screw meshing and screw-nut transmission principle to convert the horizontal rotation output force of the motor 8 into a vertical lifting thrust; The lift 4 is fixedly connected to the moving frame 2 and is arranged parallel to the linear guide rail 9; The connecting rod 6 spans across the main frame 1, and its two ends are connected to the elevator 4. The elevator 4 is at both ends of the main frame 1, synchronously driving the moving frame 2 to move along the linear guide rail 9; The coupling 5 is installed at both ends of the connecting rod 6, and is located on one side of the inner wall of the left and right support plates; The motor 8 is installed outside the lift 4 on one side and is electrically connected to the lift 4; The reducer 7 is installed between the motor 8 and the elevator 4 .

[0046] The fixed roller group 10 side is the film inlet side, and the movable roller group 11 side is the film outlet side; The vertical distance between the centers of the rollers in the fixed roller group 10 and the movable roller group 11 is 65 mm, and the horizontal distance between the centers of the rollers is 200 mm; The upper and lower movement limit of the mobile frame 2 is 89 mm, and the left and right movement limit is 45 mm; Each roller in the fixed roller group 10 and the movable roller group 11 is equipped with a transmission motor.

[0047] This embodiment also provides a method for stretching a film using the longitudinal stretching device with adjustable stretching gap, comprising the following steps: Step 1, adjusting the lifter 4 by the motor 8 in the longitudinal stretching device with adjustable stretching gap, driving the movable frame 2 to move to a preset position in the longitudinal stretching device with adjustable stretching gap; Step 2: stretch the film from the inlet side of the longitudinal stretching device with adjustable stretching gap to the longitudinal stretching device with adjustable stretching gap in an alternating manner, and wind it around the fixed roller group 10 and the movable roller group 11 in sequence, wherein the rotation speed of the rollers in the fixed roller group 10 is 212 r / min, 215 r / min and 227 r / min in sequence from the film entry side; the rotation speed of the rollers in the movable roller group 11 is 868 r / min, 1000 r / min and 1060 r / min in sequence from the film entry side; Step 3, repeatedly adjusting the movable frame 2 until the production requirements are met, and after the adjustment is completed, entering the next process section of the film, the film is stretched 5 times.

[0048] In this embodiment, the thickness of the film before being stretched by the longitudinal stretching device with adjustable stretching gap is 2 mm, and the thickness after being stretched is 0.4 mm.

[0049] Based on the above, it can be seen that the longitudinal stretching device with adjustable stretching gap of the present invention has a wide range of applications, low cost and extremely high market prospects.

[0050] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A longitudinal stretching device with adjustable stretching gap, characterized in that: The longitudinal stretching device with adjustable stretching gap comprises, from bottom to top, a main frame (1), a moving frame (2), an elevator assembly and a stretching roller group; The movable frame (2) is mounted on the main frame (1) via a lifting assembly, and the stretching roller group is mounted on the main frame (1) and the movable frame (2); The elevator assembly comprises a mounting seat (3), an elevator (4), a coupling (5), a connecting rod (6), a reducer (7), a motor (8) and a linear guide rail (9); The stretching roller group comprises a fixed roller group (10) and a movable roller group (11), wherein the fixed roller group (10) is mounted on the main frame (1), and the movable roller group (11) is mounted on the movable frame (2); The mounting seat (3) is mounted on the main frame (1), the lift (4) is mounted on the mounting seat (3), and the lift (4) is connected to the mobile frame (2) to drive the mobile frame (2) to move up and down; The linear guide rail (9) connects the main frame (1) and the movable frame (2); the movable frame (2) moves linearly along the linear guide rail (9) through the lift (4); and the linear guide rail (9) is installed at an angle.

2. The longitudinal stretching device with adjustable stretching gap according to claim 1, characterized in that: The angle between the side of the linear guide rail (9) close to the main frame (1) and the horizontal is 60-65 degrees.

3. The longitudinal stretching device with adjustable stretching gap according to claim 1, characterized in that: Height adjustment bolts are symmetrically installed at the four corners of the bottom and inside and outside of the main frame (1).

4. The longitudinal stretching device with adjustable stretching gap according to claim 1, characterized in that: The mobile frame (2) is divided into a left and a right side, and the support plates on the left and right sides of the main frame (1) are symmetrically provided with grooves adapted to the size of the mobile frame (2), and the mobile frame (2) is symmetrically nested in the support plates on the left and right sides of the main frame (1).

5. The longitudinal stretching device with adjustable stretching gap according to claim 1, characterized in that: The movable frame (2) is divided into an upper roller group part (201) and a lower lifting part (202).

6. The longitudinal stretching device with adjustable stretching gap according to claim 5, characterized in that: A limiting device is also provided at the bottom of the lifting portion (202) for limiting the collision or contact between the movable frame (2) and the main frame (1).

7. The longitudinal stretching device with adjustable stretching gap according to claim 5, characterized in that: The main frame (1) and the roller group part (201) of the movable frame (2) are both provided with circular holes adapted to the diameter of the roller drive shaft, and the top of the circular hole is an open structure, forming a "semi-enclosed" slot for installing the roller.

8. The longitudinal stretching device with adjustable stretching gap according to claim 1, characterized in that: The mounting seat (3) is symmetrically mounted on the support plates on the left and right sides of the main frame (1), located below the mobile frame (2), and parallel to the bottom edge of the mobile frame (2).

9. The longitudinal stretching device with adjustable stretching gap according to claim 1, characterized in that: The lift (4) is fixedly connected to the movable frame (2) and is arranged parallel to the linear guide rail (9).

10. A method for stretching a film using a longitudinal stretching device with adjustable stretching gap according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: adjusting the lifter (4) by means of a motor (8) in the longitudinal stretching device with an adjustable stretching gap, thereby driving the movable frame (2) to move to a preset position in the longitudinal stretching device with an adjustable stretching gap; Step 2, stretching the film from the inlet side of the longitudinal stretching device with adjustable stretching gap to the longitudinal stretching device with adjustable stretching gap in an alternating manner, and winding it around the fixed roller group (10) and the movable roller group (11) in sequence; Step 3: repeatedly adjusting the movable frame (2) until the production requirements are met, and after the adjustment is completed, entering the next process section of the film.

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