Film forming method and film forming device for improving melt marginal flow stability

Abstract

The invention discloses a film forming method for improving melt marginal flow stability. The film forming method comprises the following steps: detecting the thickness of a film body discharged from a flow channel of a die lip in each position perpendicular to a discharging direction; the deviation of the average thickness of the film body in the coverage range of each first ultrasonic oscillation assembly relative to the average thickness of all areas of the film body is obtained; and according to the deviation of the average thickness of the film body in the coverage range of each first ultrasonic oscillation assembly relative to the average thickness of all areas of the film body, the output power of each first ultrasonic oscillation assembly is adjusted, so that the thickness uniformity of the film body is improved. The thickness of the film body in each position perpendicular to the discharging direction is detected, and the output power of the first ultrasonic oscillation assembly is adjusted according to the thickness deviation. When the thickness of the film body in each area has deviation, the fluidity of the melt in the area can be changed by adjusting the power of the first ultrasonic oscillation assembly in the corresponding area, so that the thickness of each area of the film body tends to be consistent, and the overall quality of the film body is improved.

Description

Technical Field

[0001] The present application relates to the field of material film formation, and in particular to a film forming method and a film forming device for improving the marginal flow stability of a melt. Background Art

[0002] In the field of polyolefin film applications, the development of film-forming technology is becoming increasingly important as industrial production continues to increase the quality and performance requirements of plastic products. High-quality polyolefin films are widely used in numerous industries, including packaging, agriculture, and electronics, and their performance directly impacts the product's performance and market competitiveness. Excellent film-forming technology ensures that the film possesses appropriate thickness, strength, and good continuity, thereby meeting the diverse demands for polyolefin film in different fields. For example, in the food packaging industry, polyolefin film requires a certain strength to protect food, while also having a uniform thickness to ensure the packaging's sealing and aesthetics. In the agricultural sector, the quality of polyolefin film affects the growth environment and yield of crops. Therefore, continuously optimizing polyolefin film-forming technology is of great significance to promoting the development of related industries.

[0003] In previous polyolefin film production processes, the industry has employed a variety of conventional methods to address issues related to melt flow within the die lip flow channel. One common approach involves adding a low-molecular-weight lubricant, which forms a lubricating layer at the interface between the melt and the metal, thereby improving the melt's release properties and maintaining a stable marginal flow within the narrow gap. Another approach involves increasing the die lip temperature, which improves marginal flow stability and allows the melt to flow more smoothly through the die lip flow channel. However, these methods also have their limitations.

[0004] Existing polyolefin film-making technology has obvious defects. Although the addition of low-polymerization lubricants can improve the demoulding properties and marginal flow stability of the melt to a certain extent, it will partially reduce the viscosity of the melt, causing the melt to lack high viscoelasticity, resulting in the strain being unable to respond to stress in a timely manner. During molding, it is easily affected by the friction resistance of the die lip, which leads to molding defects such as lines and ribs, and also causes the mechanical properties of the product to deteriorate. Although increasing the die lip temperature can improve marginal flow stability, it will promote the occurrence of thermal degradation, reduce thermal stability, and require the additional addition of antioxidants, thermal stabilizers, etc., which increases the thermodynamic imbalance of the system. In addition, the viscous effect of the marginal flow will cause the slower-flowing inorganic powder particles in the melt to aggregate, reducing the gloss and mechanical properties of the product. At the same time, due to the different effects of the marginal flow viscosity effect at different positions, the thickness of the generated film will be uneven, affecting the overall quality of the film. Summary of the Invention

[0005] In order to solve the technical problems in the prior art, the present application provides a film forming method for improving the stability of the marginal flow of the melt.

[0006] The present application provides a film forming method for improving the stability of the melt marginal flow, which adopts the following technical solution: A film forming method for improving the marginal flow stability of a melt, comprising: Detecting the thickness of the film discharged from the flow channel of the die lip at various positions perpendicular to the discharge direction, wherein a plurality of first ultrasonic oscillation components are evenly distributed on the die lip perpendicular to the discharge direction; Obtaining, based on the thickness of the film at various positions perpendicular to the discharge direction, a deviation of the average thickness of the film within the coverage area of ​​each first ultrasonic oscillation component relative to the average thickness of all regions of the film; According to the deviation of the average thickness of the film within the coverage area of ​​each first ultrasonic oscillation component relative to the average thickness of all areas of the film, the output power of each first ultrasonic oscillation component is adjusted to improve the uniformity of the film thickness.

[0007] In some embodiments, the step of obtaining the average thickness deviation within the coverage area of ​​each first ultrasonic oscillation component specifically includes: For each coverage area of ​​the first ultrasonic oscillation component, calculate the average thickness of all detection points in the area Wherein, i is a natural number greater than 0; Calculate the global average thickness of all regions of the membrane: Wherein, n is the total number of first ultrasonic oscillation components; Calculate the average thickness deviation within the coverage area of ​​each first ultrasonic oscillation component, specifically: Among them, e i is the average thickness deviation within the coverage area of ​​the i-th first ultrasonic oscillation component.

[0008] In some embodiments, in the step of adjusting the output power of each first ultrasonic oscillation component, a PID control algorithm is used to calculate the power adjustment amount ΔP i , the formula is: Among them, K p is the proportionality coefficient, K i is the integral coefficient, K d is the differential coefficient, Δt is the control period, e i，prev is the deviation value of the previous control cycle.

[0009] In some embodiments, an observation window is formed on the surface of the die lip, and a plurality of second ultrasonic oscillation components are evenly distributed on the die lip perpendicular to the discharge direction, and each of the second ultrasonic oscillation components is located in front of the observation window along the discharge direction; The film forming method for improving the marginal flow stability of the melt further comprises: Acquiring an image of the melt in the flow channel through the observation window, and detecting whether agglomerated particles exist in the melt and the positions of the agglomerated particles based on the image of the melt; According to the position of the agglomerated particles in the melt, the corresponding second ultrasonic vibration component is activated to break up the agglomerated particles in the melt.

[0010] In some embodiments, the step of detecting whether there are agglomerated particles in the melt and the location of the agglomerated particles based on the image of the melt specifically includes: The collected melt image is grayscaled, noise filtered, and binarized to extract the contour features of the particles in the melt. A threshold-based segmentation algorithm is used to calculate the area and roundness of each particle. If the area of ​​a particle exceeds the set area threshold or the roundness is lower than the set roundness threshold, it is determined to be an agglomerated particle. The positions of the detected agglomerated particles in the image are mapped to the two-dimensional coordinate system of the die lip to generate the coordinates of the agglomerated particles.

[0011] In some embodiments, the step of activating the corresponding second ultrasonic vibration component according to the position of the agglomerated particles in the melt to break up the agglomerated particles in the melt specifically includes: Establishing a corresponding relationship between the position of the second ultrasonic oscillation component on the die lip and the two-dimensional coordinate system; According to the coordinates of the agglomerated particles, the corresponding second ultrasonic oscillation component number is determined and a start instruction is generated; if the agglomerated particles span multiple component intervals, multiple adjacent second ultrasonic oscillation components are started simultaneously.

[0012] The present application also provides a film forming device for improving the stability of the melt marginal flow, comprising: a thickness detection module, for detecting the thickness of the film discharged from the flow channel of the die lip at various positions perpendicular to the discharge direction, wherein a plurality of first ultrasonic oscillation components are evenly distributed on the die lip perpendicular to the discharge direction; a thickness deviation calculation module for obtaining, based on the thickness of the film at each position perpendicular to the discharge direction, a deviation of the average thickness of the film within the coverage area of ​​each first ultrasonic oscillation component relative to the average thickness of all regions of the film; The power control module is used to adjust the output power of each first ultrasonic oscillation component according to the deviation of the average thickness of the film within the coverage area of ​​each first ultrasonic oscillation component relative to the average thickness of all areas of the film to improve the uniformity of the film thickness.

[0013] In some embodiments, a plurality of first mounting holes communicating with the flow channel are formed on the surface of the die lip, and each of the first ultrasonic vibration components is embedded in a corresponding first mounting hole.

[0014] In some embodiments, the thickness detection module includes a linear motor and an ellipsometer. The linear motor is arranged above the discharge end of the die lip and is set perpendicular to the discharge direction. The ellipsometer is installed at the movable end of the linear motor.

[0015] In some embodiments, an observation window is formed on the surface of the die lip, and a plurality of second ultrasonic oscillation components are evenly distributed on the die lip perpendicular to the discharge direction, and each of the second ultrasonic oscillation components is located in front of the observation window along the discharge direction; The film forming device for improving the stability of the melt marginal flow also includes: an agglomerated particle detection module, configured to obtain an image of the melt in the flow channel through the observation window, and detect whether agglomerated particles exist in the melt and the location of the agglomerated particles based on the image of the melt; The agglomerated particle breaking-up control module is used to start the corresponding second ultrasonic oscillation component according to the position of the agglomerated particles in the melt to break up the agglomerated particles in the melt.

[0016] In summary, this application includes at least one of the following beneficial technical effects: 1. In traditional processes, adding low-polymerization lubricants can lead to molding defects such as lines and ribs during molding. Increasing the die lip temperature can promote thermal degradation and reduce thermal stability. This technical solution uses ultrasonic vibration to adjust the melt fluidity, avoiding these problems, improving the molding performance of the melt, and reducing molding defects. 2. In traditional processes, the viscous effect of marginal flow can lead to uneven film thickness. This technical solution detects the thickness of the film at various locations perpendicular to the discharge direction and, based on thickness deviations, uses a PID control algorithm to adjust the output power of the first ultrasonic oscillator. When the film thickness in each area deviates, adjusting the power of the first ultrasonic oscillator in the corresponding area can change the fluidity of the melt in that area, thereby making the thickness of each area of ​​the film more consistent, thereby improving the overall quality of the film. 3. In traditional processes, agglomerated particles in the melt can reduce the gloss and mechanical properties of the finished product. This technical solution utilizes an observation window and a second ultrasonic oscillator to promptly detect and break up agglomerated particles in the melt. To detect agglomerated particles, the collected melt image is processed, and a threshold-based segmentation algorithm is used to identify agglomerated particles. Their locations are mapped to the two-dimensional coordinate system of the die lip, and the corresponding second ultrasonic oscillator is activated to break them up. This prevents the agglomerated particles from affecting the performance of the finished product and improves its mechanical properties and gloss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic flow chart of a film forming method for improving the stability of melt marginal flow provided in one embodiment of the present application; Figure 2 1 is a schematic diagram of the three-dimensional structure of a film-forming device for improving the stability of the melt marginal flow provided by one embodiment of the present application; Figure 3 yes Figure 2 A top view of a film forming device for improving the stability of the melt marginal flow; Figure 4 yes Figure 3 Sectional view of mid-section AA; Figure 5 yes Figure 4 A partial enlarged view of the middle area B; Figure 6 yes Figure 2 Schematic diagram of the three-dimensional structure of the thickness detection module; Explanation of the accompanying symbols: 1. Die lip; 11. Flow channel; 12. Observation window; 2. Membrane body; 3. First ultrasonic oscillation component; 4. Second ultrasonic oscillation component; 5. Thickness detection module; 51. Linear motor; 52. Ellipsometer; 6. Agglomerated particle detection module; 61. Fill light; 62. Image collector. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The described embodiments are only possible technical implementations of the present invention, but are not limited thereto. Those skilled in the art can fully combine the embodiments of the present invention, and other embodiments obtained without creative work are also within the scope of protection of the present invention.

[0019] This application mainly adopts the arrangement of ultrasonic oscillation components on the die lip to adjust the power and break up the particles, thereby achieving the effect of improving the marginal flow stability of the melt and the uniformity of the film thickness. The following is a further detailed description of this application.

[0020] Example 1 Please refer to Figures 1-6 The film forming method for improving the marginal flow stability of the melt provided in the embodiment of the present application includes: S1. Detect the thickness of the film body 2 discharged from the flow channel 11 of the die lip 1 at various positions perpendicular to the discharge direction, wherein a plurality of first ultrasonic oscillation components 3 are evenly distributed on the die lip 1 perpendicular to the discharge direction; in this embodiment, the first ultrasonic oscillation component 3 is arranged at a position 10 mm away from the outlet of the die lip 1, and the frequency of the ultrasonic wave emitted by the first ultrasonic oscillation component 3 is 20 to 50 kHz, and the first ultrasonic oscillation component 3 includes an ultrasonic generator and a transducer.

[0021] S2. Obtaining, based on the thickness of the film 2 at each position perpendicular to the discharge direction, the deviation of the average thickness of the film 2 within the coverage area of ​​each first ultrasonic oscillation component 3 relative to the average thickness of all regions of the film 2; S3. According to the deviation of the average thickness of the membrane 2 within the coverage area of ​​each first ultrasonic oscillation component 3 relative to the average thickness of all areas of the membrane 2, adjust the output power of each first ultrasonic oscillation component 3 to improve the thickness uniformity of the membrane 2.

[0022] The thickness of the film 2 discharged from the flow channel 11 of the die lip 1 at various locations perpendicular to the discharge direction is measured. Based on this thickness data, the deviation of the average thickness of the film 2 within the coverage area of ​​each first ultrasonic oscillation component 3 relative to the average thickness of all regions of the film 2 is calculated. Finally, the output power of the first ultrasonic oscillation component 3 is adjusted based on this deviation. This effectively improves the thickness uniformity of the film 2. When there is thickness deviation in each region of the film 2, adjusting the power of the first ultrasonic oscillation component 3 in the corresponding region can change the fluidity of the melt in that region, thereby making the thickness of each region of the film 2 more uniform.

[0023] Specifically, various suitable detection devices can be used to detect the thickness of the film 2. For example, optical detection equipment, such as the ellipsometer 52, can accurately measure the thickness of the film 2. Laser rangefinders can also be used to calculate the thickness of the film 2 by emitting laser light and receiving reflected light. These devices can be moved perpendicular to the discharge direction to measure the thickness of the film 2 at different locations.

[0024] To determine the average thickness deviation within the coverage area of ​​each first ultrasonic oscillator 3, first calculate the average thickness of all test points within the coverage area of ​​each first ultrasonic oscillator 3. Then, calculate the global average thickness of all regions of the membrane 2. Add the average thicknesses of the areas covered by each first ultrasonic oscillator 3 and divide by the total number of first ultrasonic oscillators 3 to obtain the global average thickness. Finally, subtract the global average thickness from the average thickness of the area covered by each first ultrasonic oscillator 3 to obtain the average thickness deviation within the coverage area of ​​that component.

[0025] Specifically, the step of obtaining the average thickness deviation within the coverage area of ​​each first ultrasonic oscillation component 3 includes: S21, for each coverage area of ​​the first ultrasonic oscillation component 3, calculate the average thickness of all detection points in the area Wherein, i is a natural number greater than 0; S22. Calculate the global average thickness of all regions of membrane 2: Wherein, n is the total number of the first ultrasonic oscillation components 3; S23, calculating the average thickness deviation within the coverage area of ​​each first ultrasonic oscillation component 3, specifically: Among them, e i is the average thickness deviation within the coverage area of ​​the i-th first ultrasonic oscillation component 3.

[0026] When adjusting the output power of each first ultrasonic oscillator 3, a PID control algorithm is used to calculate the power adjustment amount. The PID control algorithm comprehensively considers the three factors of proportion, integration, and differentiation. It calculates the power adjustment amount based on the current deviation, the integral of the deviation, and the rate of change of the deviation, making the adjustment more precise and stable.

[0027] Specifically, in the step of adjusting the output power of each first ultrasonic oscillating component 3, the power adjustment amount ΔP is calculated using a PID control algorithm. i , the formula is: Among them, K p is the proportionality coefficient, K i is the integral coefficient, K d is the differential coefficient, Δt is the control period, e i，prev is the deviation value of the previous control cycle.

[0028] Ultrasonic vibrations have a mechanical effect on the melt. When the output power of the first ultrasonic vibration component 3 is increased, the propagation of ultrasonic waves in the melt causes high-frequency vibrations in the melt molecules. This high-frequency vibration can partially break down the physical entanglements and weak interactions between the melt molecules, reducing the melt's apparent viscosity. In the flow channel 11 of the die lip 1, the melt's fluidity is enhanced, allowing more melt to pass through a specific area in the same amount of time. As the melt flow rate increases, more melt accumulates in this area during the film 2 molding process, resulting in an increase in the thickness of the film 2. Furthermore, a boundary layer forms at the interface between the die lip 1 and the melt. The effect of ultrasonic waves affects the properties of this boundary layer. Increasing the ultrasonic power can cause greater disturbances in the melt within the boundary layer, reducing its thickness. A reduction in boundary layer thickness means less friction between the melt and the wall of the die lip 1, allowing the melt to flow more freely. This makes it easier for the melt to accumulate in a specific area perpendicular to the discharge direction during flow, thereby increasing the thickness of the film 2 in this area.

[0029] If an observation window 12 is formed on the surface of the die lip 1 and a plurality of second ultrasonic oscillation components 4 are evenly distributed on the die lip 1 perpendicular to the discharge direction, in this embodiment, the frequency of the ultrasonic waves emitted by the second ultrasonic oscillation components 4 is 20 to 50 kHz, and each second ultrasonic oscillation component 4 is located in front of the observation window 12 along the discharge direction, the film forming method further includes obtaining an image of the melt in the flow channel 11 through the observation window 12, and detecting the presence and location of agglomerated particles in the melt based on the image of the melt, and then activating the corresponding second ultrasonic oscillation component 4 based on the location of the agglomerated particles in the melt to break up the agglomerated particles.

[0030] To detect agglomerated particles, the captured melt image undergoes grayscale processing, noise filtering, and binary segmentation to extract the contour features of the particles within the melt. A threshold-based segmentation algorithm calculates the area and roundness of each particle. If the particle's area exceeds the set area threshold or its roundness falls below the set roundness threshold, it is identified as an agglomerated particle. The positions of the detected agglomerated particles in the image are then mapped to the two-dimensional coordinate system of die lip 1 to generate the coordinates of the agglomerated particles.

[0031] When starting the corresponding second ultrasonic oscillation component 4, the corresponding second ultrasonic oscillation component 4 number is determined based on the pre-established correspondence between the position of the second ultrasonic oscillation component 4 on the die lip 1 and the two-dimensional coordinate system, as well as the coordinates of the agglomerated particles, and a start instruction is generated; if the agglomerated particles span multiple component intervals, multiple adjacent second ultrasonic oscillation components 4 are started simultaneously.

[0032] The operating principle of this embodiment is as follows: by detecting and analyzing the thickness of the film 2 and utilizing a PID control algorithm to adjust the output power of the first ultrasonic oscillator 3, the thickness of each region of the film 2 is made more uniform, thus avoiding uneven thickness caused by the marginal flow viscosity effect. Simultaneously, utilizing the observation window 12 and the second ultrasonic oscillator 4, agglomerated particles in the melt can be promptly detected and broken up, preventing particle aggregation from affecting the gloss and mechanical properties of the finished product. Compared to traditional film-forming methods, this significantly improves the molding quality and performance of the polyolefin film, reduces molding defects, and enhances the market competitiveness of the finished product.

[0033] Example 2 The film-forming device for improving the marginal flow stability of the melt provided in the embodiment of the present application includes a thickness detection module 5, a thickness deviation calculation module and a power control module. Among them, the thickness detection module 5 is connected to the thickness deviation calculation module, and the thickness deviation calculation module is connected to the power control module. The thickness detection module 5 detects the thickness of the film body 2 discharged from the flow channel 11 of the die lip 1 at each position perpendicular to the discharge direction. The thickness deviation calculation module obtains the deviation of the average thickness of the film body 2 within the coverage range of each first ultrasonic oscillation component 3 relative to the average thickness of all areas of the film body 2 based on these thickness data. The power control module then adjusts the output power of each first ultrasonic oscillation component 3 according to the deviation to improve the thickness uniformity of the film body 2. Such a combination of modules and work flow enables the entire film-forming device to automatically and efficiently adjust the thickness of the film body 2 and improve the film forming quality.

[0034] Specifically, the thickness detection module 5 includes a linear motor 51 and an ellipsometer 52. The linear motor 51 is arranged above the discharge end of the die lip 1 and is set perpendicular to the discharge direction. The ellipsometer 52 is installed at the movable end of the linear motor 51. The linear motor 51 can drive the ellipsometer 52 to move perpendicular to the discharge direction, thereby realizing the detection of the thickness of different positions of the film body 2. The ellipsometer 52 determines the thickness of the film body 2 by measuring the change in the polarization state of light after reflection from the surface of the film body 2, and has the advantages of high precision and non-contact. Of course, the thickness detection module 5 can also use other devices, such as a laser displacement sensor, which calculates the distance by emitting a laser and measuring the time from the laser being emitted to the laser being reflected back by the film body 2, thereby obtaining the thickness of the film body 2.

[0035] The surface of the die lip 1 is provided with a plurality of first mounting holes that communicate with the flow channel 11. Each first ultrasonic oscillator 3 is embedded in a corresponding first mounting hole. This mounting arrangement allows the first ultrasonic oscillator 3 to better contact the melt, transferring ultrasonic energy to the melt and improving the melt's fluidity and stability.

[0036] If an observation window 12 is formed on the surface of the die lip 1, a number of second ultrasonic oscillation components 4 are evenly distributed on the die lip 1 perpendicular to the discharge direction, and along the discharge direction, each second ultrasonic oscillation component 4 is located in front of the observation window 12. The film forming device also includes a cluster particle detection module 6 and an cluster particle breakup control module. The cluster particle detection module 6 obtains an image of the melt in the flow channel 11 through the observation window 12, and detects whether there are cluster particles in the melt and the position of the cluster particles based on the image of the melt. The cluster particle breakup control module starts the corresponding second ultrasonic oscillation component 4 according to the position of the cluster particles in the melt to break up the cluster particles in the melt.

[0037] The agglomerated particle detection module 6 includes a fill light 61 and an image collector 62. Two observation windows 12 are positioned opposite each other on the upper and lower surfaces of the die lip 1. The fill light 61 is positioned below the lower observation window 12, while the image collector 62 is positioned above the upper observation window 12. The fill light 61 provides sufficient light for image acquisition, enabling the image collector 62 to clearly capture images of the melt. The image collector 62 can be a high-speed camera, which can quickly and accurately capture images of the melt.

[0038] The surface of the die lip 1 is provided with a plurality of second mounting holes connected to the flow channel 11, and each second ultrasonic oscillation component 4 is embedded in the corresponding second mounting hole. The second ultrasonic oscillation component 4 is located on the rear side of the first ultrasonic oscillation component 3. In this way, after the agglomerated particles are broken up, they can be further dispersed by the first ultrasonic oscillation component 3.

[0039] The implementation principle of this embodiment is as follows: through the coordinated work of various modules, the film-forming device can monitor the thickness of the film body 2 and the agglomerated particles in the melt in real time and make timely adjustments. The thickness detection module 5 accurately obtains the thickness data of the film body 2, the thickness deviation calculation module analyzes the deviation, and the power control module adjusts the power of the first ultrasonic oscillation component 3 to make the thickness of the film body 2 more uniform. The agglomerated particle detection module 6 and the agglomerated particle dispersion control module can promptly detect and process the agglomerated particles in the melt to ensure the quality of the product. The entire film-forming device realizes the automation and intelligent control of the polyolefin film-making process, improves production efficiency and product quality, and reduces production costs.

[0040] The beneficial effects of this application include: (1) In traditional processes, the addition of low-polymerization lubricants can lead to molding defects such as lines and ribs during molding. Increasing the die lip temperature will promote thermal degradation and reduce thermal stability. This technical solution adjusts the melt fluidity through ultrasonic vibration, avoiding these problems, improving the molding performance of the melt, and reducing molding defects. (2) In traditional processes, the viscous effect of marginal flow can lead to uneven thickness of the film 2. This technical solution detects the thickness of the film 2 at various positions perpendicular to the discharge direction and uses a PID control algorithm to adjust the output power of the first ultrasonic oscillation component 3 based on the thickness deviation. When there is a deviation in the thickness of the film 2 in each area, adjusting the power of the first ultrasonic oscillation component 3 in the corresponding area can change the fluidity of the melt in that area, thereby making the thickness of each area of ​​the film 2 tend to be consistent, thereby improving the overall quality of the film 2; (3) In traditional processes, agglomerated particles in the melt can reduce the gloss and mechanical properties of the product. This technical solution utilizes the observation window 12 and the second ultrasonic oscillation component 4 to promptly detect and break up agglomerated particles in the melt. When detecting agglomerated particles, the collected melt image is processed, and a threshold-based segmentation algorithm is used to determine the agglomerated particles. The agglomerated particles are mapped to the two-dimensional coordinate system of the die lip 1, and the corresponding second ultrasonic oscillation component 4 is activated to break them up. This prevents the agglomerated particles from affecting the performance of the product and improves the mechanical properties and gloss of the product.

[0041] The specific implementation methods of the present application described above do not constitute a limitation on the scope of protection of the present application. Any other corresponding changes and modifications made based on the technical concept of the present application should be included in the scope of protection of the present application.

Claims

1. A film forming method for improving the marginal flow stability of a melt, characterized in that: include: Detecting the thickness of a film (2) discharged from a flow channel (11) of a die lip (1) at various positions perpendicular to the discharge direction, wherein a plurality of first ultrasonic oscillation components (3) are uniformly distributed on the die lip (1) perpendicular to the discharge direction; Obtaining, based on the thickness of the film (2) at various positions perpendicular to the discharge direction, the deviation of the average thickness of the film (2) within the coverage area of ​​each of the first ultrasonic oscillation components (3) relative to the average thickness of all regions of the film (2); According to the deviation of the average thickness of the membrane body (2) within the coverage area of ​​each first ultrasonic oscillation component (3) relative to the average thickness of all areas of the membrane body (2), the output power of each first ultrasonic oscillation component (3) is adjusted to improve the thickness uniformity of the membrane body (2).

2. The film forming method for improving the marginal flow stability of the melt according to claim 1, characterized in that: The step of obtaining the average thickness deviation within the coverage area of ​​each first ultrasonic oscillation component (3) specifically includes: For each coverage area of ​​the first ultrasonic oscillation component (3), calculate the average thickness of all detection points in the area Wherein, i is a natural number greater than 0; Calculate the global average thickness of all regions of the membrane (2): Wherein, n is the total number of the first ultrasonic oscillation components (3); The average thickness deviation within the coverage area of ​​each first ultrasonic oscillation component (3) is calculated as follows: Among them, e i is the average thickness deviation within the coverage area of ​​the i-th first ultrasonic oscillation component (3).

3. The film forming method for improving the marginal flow stability of the melt according to claim 2, characterized in that: In the step of adjusting the output power of each first ultrasonic oscillation component (3), a PID control algorithm is used to calculate the power adjustment amount ΔP i , the formula is: Among them, K p is the proportionality coefficient, K i is the integral coefficient, K d is the differential coefficient, Δt is the control period, e i，prev is the deviation value of the previous control cycle.

4. The film forming method for improving the marginal flow stability of the melt according to claim 1, characterized in that: An observation window (12) is formed on the surface of the die lip (1), and a plurality of second ultrasonic oscillation components (4) are evenly distributed on the die lip (1) perpendicular to the discharge direction. Along the discharge direction, each of the second ultrasonic oscillation components (4) is located in front of the observation window (12); The film forming method for improving the marginal flow stability of the melt further comprises: Acquiring an image of the melt in the flow channel (11) through the observation window (12), and detecting whether agglomerated particles exist in the melt and the positions of the agglomerated particles based on the image of the melt; According to the position of the agglomerated particles in the melt, the corresponding second ultrasonic vibration component (4) is activated to break up the agglomerated particles in the melt.

5. The film forming method for improving the marginal flow stability of the melt according to claim 4, characterized in that: The step of detecting whether agglomerated particles exist in the melt and the positions of the agglomerated particles according to the image of the melt specifically includes: The collected melt image is grayscaled, noise filtered, and binarized to extract the contour features of the particles in the melt. A threshold-based segmentation algorithm is used to calculate the area and roundness of each particle. If the area of ​​a particle exceeds the set area threshold or the roundness is lower than the set roundness threshold, it is determined to be an agglomerated particle. The positions of the detected agglomerated particles in the image are mapped to the two-dimensional coordinate system of the die lip (1) to generate the coordinates of the agglomerated particles.

6. The film forming method for improving the marginal flow stability of the melt according to claim 5, characterized in that: The step of starting the corresponding second ultrasonic vibration component (4) according to the position of the agglomerated particles in the melt to break up the agglomerated particles in the melt specifically includes: Establishing a corresponding relationship between the position of the second ultrasonic oscillation component (4) on the die lip (1) and the two-dimensional coordinate system; According to the coordinates of the agglomerated particles, the corresponding second ultrasonic oscillation component (4) number is determined, and a start instruction is generated; if the agglomerated particles span multiple component intervals, multiple adjacent second ultrasonic oscillation components (4) are started simultaneously.

7. A film forming device for improving the stability of melt marginal flow, characterized in that: include: A thickness detection module (5) is used to detect the thickness of the film (2) discharged from the flow channel (11) of the die lip (1) at various positions perpendicular to the discharge direction, wherein a plurality of first ultrasonic oscillation components (3) are uniformly distributed on the die lip (1) perpendicular to the discharge direction; a thickness deviation calculation module for obtaining, based on the thickness of the film body (2) at various positions perpendicular to the discharge direction, a deviation of the average thickness of the film body (2) within the coverage area of ​​each of the first ultrasonic oscillation components (3) relative to the average thickness of all regions of the film body (2); A power control module is used to adjust the output power of each first ultrasonic oscillation component (3) based on the deviation of the average thickness of the membrane body (2) within the coverage area of ​​each first ultrasonic oscillation component (3) relative to the average thickness of all areas of the membrane body (2), so as to improve the thickness uniformity of the membrane body (2).

8. The film forming device for improving the marginal flow stability of the melt according to claim 7, characterized in that: The surface of the die lip (1) is provided with a plurality of first mounting holes connected to the flow channel (11), and each of the first ultrasonic vibration components (3) is embedded in the corresponding first mounting hole.

9. The film forming device for improving the marginal flow stability of the melt according to claim 7, characterized in that: The thickness detection module (5) comprises a linear motor (51) and an ellipsometer (52), wherein the linear motor (51) is arranged above the discharge end of the die lip (1) and is arranged perpendicular to the discharge direction, and the ellipsometer (52) is installed at the movable end of the linear motor (51).

10. The film forming device for improving the marginal flow stability of melt according to claim 7, characterized in that: An observation window (12) is formed on the surface of the die lip (1), and a plurality of second ultrasonic oscillation components (4) are evenly distributed on the die lip (1) perpendicular to the discharge direction. Along the discharge direction, each of the second ultrasonic oscillation components (4) is located in front of the observation window (12); The film forming device for improving the stability of the melt marginal flow also includes: an agglomerated particle detection module (6) for acquiring an image of the melt in the flow channel (11) through the observation window (12), and detecting whether agglomerated particles exist in the melt and the location of the agglomerated particles based on the image of the melt; The agglomerated particle breaking-up control module is used to start the corresponding second ultrasonic oscillation component (4) according to the position of the agglomerated particles in the melt, so as to break up the agglomerated particles in the melt.

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