A PVC film calendering apparatus and its multi-axis collaborative processing method

Abstract

The present application relates to the technical field of film calendering process control, and particularly relates to a PVC film calendering device and a multi-axis collaborative processing method thereof. The method comprises the following steps: obtaining the thickness of different scanning points on each roller shaft in the initial processing stage of the PVC film; obtaining the unevenness degree corresponding to the scanning points on each roller shaft in the initial processing stage according to the thickness distribution of the scanning points on each roller shaft at each scanning moment in the initial processing stage, and sequentially adjusting the rotating speed of each roller shaft in combination with the relative difference of the rotating speed of adjacent roller shafts; obtaining the improvement range of the uniformity of the PVC film after the adjustment of the rotating speed of the roller shafts according to the relative change of the unevenness degree corresponding to the scanning points on the roller shafts in the initial processing stage and the intermediate processing stage, and then judging whether to continue adjusting the rotating speed of each roller shaft until the preset condition is met; and processing the PVC film by using the adjusted rotating speed of the roller shafts. The present application ensures the production quality of the PVC film calendering product.

Description

Technical Field

[0001] This invention relates to the field of film calendering process control technology, specifically to a PVC film calendering apparatus and its multi-axis collaborative processing method. Background Technology

[0002] Calendering is widely used in the processing of thermoplastics. Through the gaps between the rollers in a calender, the thermoplastic is stretched under pressure to form a film or sheet. In plastics processing, calendering is mainly used to produce polyvinyl chloride (PVC) films and sheets. Calenders are classified primarily based on the number and arrangement of the rollers, including two-roll, three-roll, and four-roll calenders. Three-roll calenders are commonly used for sheet production, while four-roll calenders can produce thinner products and are typically used for calendering PVC coatings.

[0003] Existing PVC calenders use drilled heating (heat transfer oil or superheated water) for the inner cavity of the rollers to ensure uniform temperature along the entire roller length. However, because the ends of the rollers dissipate heat faster than the middle, their cooling rate is lower, resulting in a lower temperature at the ends and a transverse temperature gradient. This uneven temperature distribution on the roller surface leads to differences in melt viscosity, causing uneven thickness of the PVC film during calendering. Furthermore, since the roller heating power is fixed, meaning the actual heating temperature is constant, it is necessary to optimize the speed ratio between different roller stages to reduce the probability of uneven film thickness. When the speed ratio is too high, the melt adheres to the surface of the high-speed roller due to excessive shearing, causing localized accumulation and thickness fluctuations. When the speed ratio is too low, the melt's adhesion to the rollers is poor, and air is easily trapped in the roller gaps, forming bubbles, which also leads to disordered thickness distribution. Ultimately, this compromises the production quality of PVC film calendered products. Summary of the Invention

[0004] To address the problem that existing methods cannot guarantee the production quality of PVC film calendered products, the present invention aims to provide a PVC film calendering device and its multi-axis collaborative processing method, the specific technical solution of which is as follows:

[0005] In a first aspect, the present invention provides a multi-axis collaborative processing method for PVC film, the method comprising the following steps:

[0006] The thickness of PVC film at different scanning points on each roller during the initial processing stage was obtained.

[0007] Based on the thickness distribution of the scanning points on each roller at each scanning moment in the initial processing stage, the degree of non-uniformity corresponding to the scanning points on each roller in the initial processing stage is obtained; based on the degree of non-uniformity corresponding to the scanning points on each roller in the initial processing stage and the relative difference in rotation speed between adjacent rollers, the rotation speed of each roller is initially adjusted in sequence.

[0008] Based on the relative changes in the degree of non-uniformity corresponding to the scanning points on the rollers during the intermediate processing stage and the initial processing stage, the improvement in film uniformity after adjusting the roller speed is obtained. The intermediate processing stage is the stage after the initial adjustment of the roller speed. Considering the overall distribution of the improvement in film uniformity after adjusting the roller speed of all rollers, it is determined whether to continue adjusting the speed of each roller until the preset conditions are met. The adjusted roller speed is then used to process the PVC film.

[0009] Preferably, the step of obtaining the degree of non-uniformity corresponding to the scanning points on each roller in the initial processing stage based on the thickness distribution of the scanning points on each roller at each scanning moment in the initial processing stage includes:

[0010] For any moment in the initial processing stage:

[0011] In the scanning area on the roller to be analyzed at any given time, the scanning point on the line segment that passes through the center point of the scanning area and is perpendicular to the central axis of the roller is recorded as a candidate scanning point;

[0012] For any candidate scan point: the line segment in the scanning area that passes through the candidate scan point and is parallel to the central axis of the roller, and the scan points located on both sides of the candidate scan point are respectively recorded as the left scan point and the right scan point of the candidate scan point; based on the thickness difference between the left and right scan points and their next adjacent scan point, and the distance between the left and right scan points and the candidate scan point, the uniformity factor of the candidate scan point at any time is obtained;

[0013] Based on the overall distribution of the uniformity factor of all candidate scanning points at all times in the initial processing stage, the degree of non-uniformity corresponding to the scanning points on the roller to be analyzed in the initial processing stage is obtained.

[0014] The roller shaft to be analyzed is any roller shaft other than the first-stage roller shaft.

[0015] Preferably, the step of obtaining the uniformity factor of any candidate scan point at any given time based on the thickness difference between the left and right scan points and their adjacent next scan point, and the distance between the left and right scan points and any candidate scan point, includes:

[0016] The thickness difference between each left scan point and its next adjacent scan point is recorded as the thickness difference corresponding to each left scan point, and the thickness difference between each right scan point and its next adjacent scan point is recorded as the thickness difference corresponding to each right scan point.

[0017] Using the normalized result of the distance between the left scan point and any candidate scan point, the corresponding thickness difference is weighted, and the normalized value of the weighted result corresponding to all left scan points of any candidate scan point is recorded as the left feature value; using the normalized result of the distance between the right scan point and any candidate scan point, the corresponding thickness difference is weighted, and the normalized value of the weighted result corresponding to all right scan points of any candidate scan point is recorded as the right feature value;

[0018] The average of the left-side feature value and the right-side feature value is used as the uniformity factor of any candidate scan point at any time.

[0019] Preferably, the step of obtaining the degree of non-uniformity corresponding to the scan points on the roller to be analyzed in the initial processing stage based on the overall distribution of the uniformity factor of all candidate scan points at all times in the initial processing stage includes:

[0020] The average value of the uniformity factor of all candidate scan points at each time step in the initial processing stage is denoted as the first average value at each time step in the initial processing stage.

[0021] The average of the first average values ​​corresponding to all moments in the initial processing stage is determined as the degree of non-uniformity corresponding to the scanning points on the roller to be analyzed in the initial processing stage.

[0022] Preferably, the initial adjustment of the rotational speed of each roller shaft according to the degree of non-uniformity corresponding to the scanning points on each roller shaft in the initial processing stage and the relative difference in rotational speed between adjacent roller shafts includes:

[0023] For the second-stage roller, calculate the first difference between the constant 1 and the degree of non-uniformity corresponding to the scanning point on the second-stage roller in the initial processing stage. Multiply the first difference by the rotational speed of the second-stage roller in the initial processing stage as the adjusted rotational speed of the second-stage roller and perform initial adjustment.

[0024] Based on the initial adjustment speed of the second-stage roller and the required speed ratio between the third-stage roller and the second-stage roller at the target thickness of the thermal paper, determine the adjusted speed of the third-stage roller and perform an initial adjustment.

[0025] Based on the initial adjustment speed of the third-stage roller and the required speed ratio between the fourth-stage roller and the third-stage roller at the target thickness of the thermal paper, determine the adjusted speed of the fourth-stage roller and perform an initial adjustment.

[0026] The total number of rollers is 4.

[0027] Preferably, the step of obtaining the improvement in film uniformity after adjusting the roller speed based on the relative change in the degree of non-uniformity corresponding to the scanning points on the roller during the intermediate processing stage and the initial processing stage includes:

[0028] Calculate the first ratio between the degree of non-uniformity corresponding to each scanning point on the roller in the intermediate processing stage and the degree of non-uniformity corresponding to the scanning point on the same roller in the initial processing stage;

[0029] Based on the first ratio corresponding to each roller and the roller level number, the improvement in film uniformity after adjusting the rotation speed of each roller is obtained.

[0030] Preferably, obtaining the improvement in film uniformity after adjusting the rotational speed of each roller based on the first ratio corresponding to each roller and the roller grade number includes:

[0031] The product of the first ratio corresponding to each roller and the roller level number is used as the improvement in film uniformity after the roller speed is adjusted.

[0032] Preferably, the determination of whether to continue adjusting the speed of each roller until a preset condition is met, based on the overall distribution of the improvement in film uniformity after adjusting the speed of all rollers, includes:

[0033] The roller speed was adjusted multiple times;

[0034] For each speed adjustment, a function representing the overall improvement in film uniformity is determined based on the improvement in film uniformity after adjusting the speed of all rollers. The control quality is determined by considering the changes in the overall improvement function. If the control quality is greater than a preset control threshold, the adjustment of the speed of all rollers is stopped.

[0035] Preferably, determining the control optimality by comprehensively considering the changes in the overall improvement magnitude function includes:

[0036] For any adjustment, the control quality corresponding to the adjustment is obtained based on the function value of the overall improvement value function corresponding to the adjustment and the absolute value of the first derivative of the overall improvement value function corresponding to the adjustment. The function value is positively correlated with the control quality, and the absolute value is negatively correlated with the control quality.

[0037] Secondly, the present invention provides a PVC film calendering apparatus for implementing the above-mentioned method. The apparatus includes a support structure and a housing, a first-stage roller, a second-stage roller, a third-stage roller, a fourth-stage roller, a heating module, a drive shaft, a laser thickness gauge, a data processing module, a central control panel, and a cooling conveying roller.

[0038] The present invention has at least the following beneficial effects:

[0039] This invention first analyzes the thickness distribution of scanning points on each roller at each scanning moment during the initial processing stage, and evaluates the degree of non-uniformity caused by temperature influence during the initial processing stage. This operation avoids the problem of uneven surface distribution due to heat dissipation at both ends of the rollers, and can improve the accuracy of subsequent speed control. Then, based on the relationship between speed and temperature influence, the speed of each roller is initially adjusted sequentially. According to the relative change in the degree of non-uniformity of the scanning points on the rollers during the intermediate processing stage and the initial processing stage after speed adjustment, the improvement of film uniformity after roller speed adjustment is evaluated. Based on the evaluation results, it is determined whether to continue adjusting the roller speed, so that the speed of each roller synchronously tends to the optimal speed. This achieves closed-loop multi-axis coordinated control of the entire calendering process, avoids the impact of excessively large or small speed ratio differences between adjacent rollers on the calendering quality of PVC film, and reduces the error impact of single control on the processing process, ensuring the production quality of PVC film calendered products. Attached Figure Description

[0040] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a mechanical structure diagram of a PVC film calendering apparatus provided in an embodiment of the present invention;

[0042] Figure 2 This is a structural diagram of the data processing module and central control panel in a PVC film calendering apparatus provided in an embodiment of the present invention;

[0043] Figure 3 This is a diagram showing the distribution of roller positions in a PVC film calendering apparatus provided in an embodiment of the present invention.

[0044] Figure 4 A flowchart of a multi-axis collaborative processing method for PVC film provided in an embodiment of the present invention;

[0045] Figure 5 This is a diagram showing the roller arrangement of a PVC film calendering apparatus provided in an embodiment of the present invention;

[0046] Among them, 1 is the support structure and outer shell; 2 is the first-stage roller; 3 is the second-stage roller; 4 is the third-stage roller; 5 is the fourth-stage roller; 6 is the heating module; 7 is the drive shaft; 8 is the laser thickness gauge; 9 is the data processing module and central control panel; and 10 is the cooling conveyor roller. Detailed Implementation

[0047] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, describes a PVC film calendering device and its multi-axis collaborative processing method according to the present invention.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] The following description, in conjunction with the accompanying drawings, details the specific scheme of a PVC film calendering device and its multi-axis collaborative processing method provided by the present invention.

[0050] An embodiment of a PVC film calendering apparatus:

[0051] This embodiment provides a PVC film calendering apparatus, which is as follows: Figure 1 , Figure 2 and Figure 3 As shown, the device includes a support structure and outer shell 1, a first-stage roller 2, a second-stage roller 3, a third-stage roller 4, a fourth-stage roller 5, a heating module 6, a drive shaft 7, a laser thickness gauge 8, a data processing module and a central control panel 9, and a cooling conveyor roller 10.

[0052] The PVC film calendering device provided in this embodiment has four rollers, namely, first-stage roller 2, second-stage roller 3, third-stage roller 4, and fourth-stage roller 5, and these four rollers are arranged in an inverted L-shape, as shown below. Figure 5 As shown. The inverted L-shaped four-roll calender achieves continuous calendering and molding of materials such as PVC through the staggered arrangement of the four rolls, combined with the synergistic effects of temperature, pressure, and rotational speed. Its core working principle can be divided into the following stages:

[0053] (1) Material plasticizing and conveying stage: The preheated material (such as PVC mixture) enters the gap between the first-stage roller 2 and the second-stage roller 3 through the feeding system. The inner cavity of the roller adopts a drilled heating structure (heat transfer oil or superheated water) to ensure uniform temperature, about 150-200℃, so that the material reaches the molten plasticizing state. During this process, it is necessary to ensure that the speed ratio between adjacent rollers meets the requirements to ensure that shear force is generated, so as to promote the uniform dispersion of the material and expel air bubbles. At the same time, the material will adhere to the roller with a faster speed. The speed ratio between adjacent rollers is usually 1.1:1 to 1.3:1, of which the speed of the second-stage roller 3 is higher than that of the first-stage roller 2.

[0054] (2) Thickness control and surface finishing stage: The gap between each roller shaft is precisely controlled (micron-level precision) by a motor-driven adjustment device to determine the final thickness of the product. Since the fourth roller shaft 5 is the discharge roller, it is usually a mirror roller with a surface roughness Ra≤0.01μm, giving the film a high gloss. The third roller shaft 4 has small deformation due to the balanced force, with vertical and horizontal forces canceling each other out. The fourth roller shaft 5 compensates for the calendering deformation through a central drum-shaped design (pre-bending) or shaft crossing technology (tilt ±1.5°) to ensure the uniformity of transverse thickness with an error ≤±0.005mm. At the same time, the inverted L-shaped arrangement allows the material to form a larger coating area on the surfaces of the third roller shaft 4 and the fourth roller shaft 5, prolonging the heat transfer time and improving the plasticizing effect.

[0055] (3) Detachment and cooling shaping stage: The drawn film is pulled to the cooling roller group by the detachment roller at a speed slightly higher than the fourth roller 5. It is quickly shaped by water cooling or air cooling to prevent deformation or adhesion at high temperature.

[0056] An example of a multi-axis collaborative processing method for PVC film:

[0057] This embodiment proposes a multi-axis collaborative processing method for PVC film, such as... Figure 4 As shown, a multi-axis collaborative processing method for PVC film in this embodiment includes the following steps:

[0058] Step S1: Obtain the thickness of the PVC film at different scanning points on each roller during the initial processing stage.

[0059] During the processing of PVC film using the PVC film calendering device provided in the above embodiments, a high-precision encoder is installed at the end of each roller of the four-roll calender of the PVC film calendering device to monitor the roller spacing and rotation speed in real time. At the same time, a laser thickness gauge is installed on the side of each calender to monitor the thickness of the PVC film at different positions in real time.

[0060] In this embodiment, firstly, the initial rotational speeds of the four rollers of the PVC film calendering device are set, and the PVC film is calendered in the initial processing stage at these initial speeds. A laser thickness gauge is used to monitor the thickness of each scanning point within the scanning area. In this embodiment, the thickness data acquisition frequency is set to once every 0.1 seconds, meaning the thickness of all scanning points within the scanning area is acquired every 0.1 seconds. In specific applications, the implementer can adjust this setting according to specific circumstances. In this embodiment, the duration of the initial processing stage is 10 minutes. In specific applications, the implementer can adjust this setting according to specific circumstances. The initial rotational speed is set based on experience and the target thickness of the product obtained after calendering, and will not be elaborated further here.

[0061] Thus, this embodiment has obtained the thickness of each scanning point on the scanning area of ​​the roller at each moment during the initial processing stage of the PVC film. All the collected thickness data and the rotation speed data of the roller are transmitted to the control terminal via the Internet of Things for subsequent analysis and processing.

[0062] Step S2: Based on the thickness distribution of the scanning points on each roller at each scanning moment in the initial processing stage, obtain the degree of non-uniformity corresponding to the scanning points on each roller in the initial processing stage; based on the degree of non-uniformity corresponding to the scanning points on each roller in the initial processing stage and the relative difference in rotation speed between adjacent rollers, perform initial adjustment of the rotation speed of each roller in sequence.

[0063] Existing PVC calenders use drilled heating (heat transfer oil or superheated water) for the inner cavity of the rollers to ensure uniform temperature along the entire roller length. However, because the ends of the rollers dissipate heat faster than the middle, their cooling rate is lower, resulting in a lower temperature at the ends and creating a transverse temperature gradient. This uneven temperature distribution on the roller surface leads to differences in melt viscosity, resulting in uneven thickness of the PVC film during calendering. Therefore, this embodiment first evaluates the performance of temperature-induced non-uniformity characteristics based on the collected thickness data.

[0064] Specifically, for any moment in the initial processing stage:

[0065] Any roller shaft other than the first-stage roller shaft is designated as the roller shaft to be analyzed.

[0066] In the scanning area on the roller to be analyzed at that moment, the scanning point on the line segment that passes through the center point of the scanning area and is perpendicular to the central axis of the roller is recorded as the candidate scanning point, that is, multiple candidate scanning points are obtained.

[0067] For any candidate scan point: the line segment passing through the scan point and parallel to the central axis of the roller in the scanning area, and the scan points located on both sides of the candidate scan point are respectively recorded as the left scan point and the right scan point of the candidate scan point. The greater the thickness fluctuation between the candidate scan point and the left scan point as the distance increases, the greater the degree of non-uniformity caused by temperature influence. Therefore, in this embodiment, the uniformity factor of the candidate scan point at that moment is obtained based on the thickness difference between the left and right scan points and their next adjacent scan point, and the distance between the left and right scan points and the candidate scan point. Specifically, the absolute value of the thickness difference between each left scan point and its next adjacent scan point is calculated. This absolute value reflects the thickness difference between each left scan point and its next adjacent scan point. This absolute value is recorded as the thickness difference corresponding to each left scan point. Using the normalized result of the distance between the left scan point and the candidate scan point, the corresponding thickness differences are weighted, and the normalized value of the weighted result corresponding to all left scan points of the candidate scan point is recorded as the left feature value.

[0068] The thickness difference between each right scan point and its next adjacent scan point is taken as the thickness difference corresponding to each right scan point. The thickness difference is weighted using the normalized result of the distance between the right scan point and the candidate scan point. The normalized value of the weighted result corresponding to all right scan points of the candidate scan point is recorded as the right feature value. The mean of the left feature value and the right feature value is taken as the uniformity factor of the candidate scan point at that time.

[0069] In this embodiment, the specific calculation formula for the left-side feature value is given, which is expressed as follows:

[0070]

[0071] Among them, w i,t Let J represent the left-side feature value of the i-th candidate scan point at time t in the initial processing stage, and let J represent the number of left-side scan points of the i-th candidate scan point. j ΔH represents the normalized distance between the i-th candidate scan point and its j-th left-hand scan point. j This represents the thickness difference corresponding to the j-th left-hand scan point of the i-th candidate scan point, and norm() represents the normalization function.

[0072] It should be noted that there are many methods for normalizing distance. Implementers can choose the existing normalization method according to the specific situation to make the normalization result of the distance take the value of (0, 1). This represents the weighted result corresponding to all left scan points of the i-th candidate scan point. The left-side feature value of the i-th candidate scan point at time t in the initial processing stage is used to characterize the degree of non-uniformity of the scan points to the left of the i-th candidate scan point caused by temperature influence.

[0073] By analogy with the calculation method of the left-side feature value, the right-side feature value of the i-th candidate scan point at time t in the initial processing stage can be obtained. The calculation formula of the right-side feature value will not be elaborated in this embodiment. The right-side feature value of the i-th candidate scan point at time t in the initial processing stage is used to characterize the degree of non-uniformity of the scan point to the right of the i-th candidate scan point caused by temperature influence.

[0074] The larger the left-side eigenvalue of the i-th candidate scan point at time t in the initial processing stage, the greater the degree of non-uniformity caused by temperature influence on the scan points to the left of the i-th candidate scan point at time t in the initial processing stage; similarly, the larger the right-side eigenvalue of the i-th candidate scan point at time t in the initial processing stage, the greater the degree of non-uniformity caused by temperature influence on the scan points to the right of the i-th candidate scan point at time t in the initial processing stage. The average of the uniformity factors of all candidate scan points at each time in the initial processing stage is denoted as the first average value corresponding to each time in the initial processing stage. The average of the first average values ​​corresponding to all times in the initial processing stage is taken as the degree of non-uniformity corresponding to the scan points on the roller to be analyzed in the initial processing stage. The greater the degree of non-uniformity, the greater the need for feedback control of the roller to be analyzed.

[0075] Using the above method, the degree of non-uniformity corresponding to the scanning points on each roller in the initial processing stage can be obtained.

[0076] Since the actual thickness uniformity of PVC film is not only related to the heating temperature, the speed difference between adjacent rollers also significantly affects the film thickness uniformity; the difference in linear speed between adjacent rollers creates a speed gradient in the roller gap. For PVC film, shearing action can break the molecular chain entanglement, promote plasticization, and induce the molecular chains to orient along the calendering direction, i.e., the calendering effect. Therefore, in this embodiment, the roller speed is initially adjusted based on the degree of non-uniformity corresponding to the scanning points on each roller during the initial processing stage and the relative difference in rotational speed between adjacent rollers.

[0077] During the adjustment process, the rotational speed of the first-stage roller 2 remains constant, while the rotational speeds of the second-stage roller 3, the third-stage roller 4, and the fourth-stage roller 5 are adjusted.

[0078] First, for the second-stage roller 3, calculate the difference between the constant 1 and the degree of non-uniformity corresponding to the scanning point on the second-stage roller 3 in the initial processing stage. Record this difference as the first difference. Use the product of the first difference and the rotational speed of the second-stage roller 3 in the initial processing stage as the adjusted rotational speed of the second-stage roller 3, and perform an initial adjustment on the rotational speed of the second-stage roller 3.

[0079] Then, based on the initially adjusted rotational speed of the second-stage roller 3 and the required rotational speed ratio between the third-stage roller 4 and the second-stage roller 3 at the target thickness of the thermal paper, the adjusted rotational speed of the third-stage roller 4 is determined, and its rotational speed is initially adjusted. Next, based on the initially adjusted rotational speed of the third-stage roller 4 and the required rotational speed ratio between the fourth-stage roller 5 and the third-stage roller 4 at the target thickness of the thermal paper, the adjusted rotational speed of the fourth-stage roller 5 is determined, and its rotational speed is initially adjusted. The required rotational speed ratio between adjacent rollers at the target thickness of the thermal paper is shown in Table 1.

[0080] Table 1

[0081]

[0082] In Table 1, v1 represents the rotational speed of the first-stage roller 2, v2 represents the rotational speed of the second-stage roller 3, v3 represents the rotational speed of the third-stage roller 4, and v4 represents the rotational speed of the fourth-stage roller 5.

[0083] After determining the adjusted rotational speed of the second-stage roller 3, the rotational speed of the third-stage roller 4 can be calculated based on the required rotational speed ratio between the third-stage roller 4 and the second-stage roller 3 at the target thickness of the thermal paper. After calculating the rotational speed of the third-stage roller 4, the rotational speed of the fourth-stage roller 5 can be calculated based on the required rotational speed ratio between the fourth-stage roller 5 and the third-stage roller 4 at the target thickness of the thermal paper.

[0084] It should be noted that if the calculated rotational speed of each roller is not within the specified rotational speed range, and if the calculated rotational speed is greater than the upper limit of the specified rotational speed range, then the upper limit of the rotational speed range will be used as the rotational speed of the corresponding roller and adjusted accordingly; if the calculated rotational speed is less than the lower limit of the specified rotational speed range, then the lower limit of the rotational speed range will be used as the rotational speed of the corresponding roller and adjusted accordingly.

[0085] Thus, the rotational speed of each roller was initially adjusted using the above method.

[0086] Step S3: Based on the relative changes in the degree of non-uniformity corresponding to the scanning points on the rollers during the intermediate processing stage and the initial processing stage, obtain the improvement in film uniformity after adjusting the roller speed. The intermediate processing stage is the stage after the initial adjustment of the roller speed. Considering the overall distribution of the improvement in film uniformity after adjusting the roller speed of all rollers, determine whether to continue adjusting the speed of each roller until the preset conditions are met. Use the adjusted roller speed to process the PVC film.

[0087] After the initial adjustment of the roller speed, the subsequent rolling process is carried out using the adjusted speed, which is the intermediate processing stage. In this embodiment, the intermediate processing stage lasts for 5 minutes. In specific applications, the implementer can set the duration according to the specific circumstances.

[0088] By analogy with the calculation method of the degree of non-uniformity corresponding to the scanning points on the roller in the initial processing stage in step S2, the degree of non-uniformity corresponding to the scanning points on each roller in the intermediate processing stage is calculated. Since the calculation process of the degree of non-uniformity corresponding to the scanning points on the roller in the initial processing stage has been explained in detail in step S2, the degree of non-uniformity corresponding to the scanning points on each roller in the intermediate processing stage will not be explained in detail here.

[0089] After the film is rolled, it needs to be cooled by other cooling rollers. At this time, a laser thickness gauge is installed at the final output end to determine the final film quality. Theoretically, the further back the roller is in the rolling process, the closer the actual uniformity and quality of the film it reflects will be to the final product quality, that is, the higher the accuracy of the adjustment requirements obtained earlier.

[0090] For each roller, the ratio of the degree of non-uniformity corresponding to the scan point on that roller during the intermediate processing stage to the degree of non-uniformity corresponding to the scan point on that roller during the initial processing stage is calculated, and this ratio is recorded as the first ratio for that roller. The later the roller's level number, the higher the reference weight of the thickness data collected on the roller. Therefore, the product of the first ratio for that roller and the roller's level number is used as the improvement in film uniformity after adjusting the roller's speed. Using the above method, the improvement in film uniformity after adjusting the speed of each roller can be calculated.

[0091] During the process of adjusting the speed according to the adjustment requirements of each roller, as the speed gradually approaches the optimal speed, the improvement rate of film uniformity slows down. At the same time, there is a non-linear relationship between the speed ratio between adjacent rollers and uniformity. Therefore, the overall improvement in uniformity after the coordinated adjustment of the rotation speed of each roller should be as large as possible. If the rate of change of the overall improvement in uniformity of all rollers is 0 after a certain adjustment, it means that the optimal speed has been reached. When the rate of change of improvement is negative, it means that the film uniformity has decreased.

[0092] In this embodiment, the roller speed will be adjusted multiple times. After each adjustment, the improvement in film uniformity after the adjustment of the roller speed will be calculated using the above method. It should be noted that each adjustment here is an adjustment of the speed of the second-stage roller 3, the third-stage roller 4, and the fourth-stage roller 5.

[0093] For any given speed adjustment, the improvement in film uniformity after all roller speed adjustments is accumulated, and the resulting function is determined as the overall improvement value function. Based on the function value of the overall improvement value function corresponding to that adjustment and the absolute value of the first derivative of the overall improvement value function corresponding to that adjustment, the control quality corresponding to that adjustment is obtained. The function value is positively correlated with the control quality, and the absolute value is negatively correlated with the control quality. A positive correlation indicates that the dependent variable increases as the independent variable increases, and decreases as the independent variable decreases; this can be an additive or multiplicative relationship, determined by the actual application. A negative correlation indicates that the dependent variable decreases as the independent variable increases, and increases as the independent variable decreases; this can be a subtractive or divisive relationship, determined by the actual application. In this embodiment, a specific method for calculating the control superiority corresponding to the adjustment is given. The sum of the absolute values ​​of the first derivative of the function representing the overall increase in magnitude corresponding to the adjustment is calculated. The normalized result of the ratio between the function value of the overall increase in magnitude corresponding to the adjustment and this sum is used as the control superiority corresponding to the adjustment. The preset adjustment parameter is introduced in the calculation of control superiority in this embodiment to prevent the denominator from being 0. In this embodiment, the preset adjustment parameter is 0.01. In specific applications, the implementer can set it according to the specific situation. If the control superiority is greater than the preset control threshold, the adjustment of the rotational speed of all rollers is stopped; if the control superiority is less than or equal to the preset control threshold, the adjustment of the roller rotational speed continues. In this embodiment, the preset control threshold is 0.95. In specific applications, the implementer can set it according to the specific situation.

[0094] It should be noted that in this embodiment, the total number of speed adjustments is set to 20. If, after 20 adjustments, the corresponding control performance is still less than or equal to the preset control threshold, the entire device needs to be overhauled to prevent the production of a large number of substandard products. In practical applications, the implementer can set the total number of speed adjustments according to the specific circumstances.

[0095] After the rotational speed of the rollers is adjusted, the adjusted roller speed is used to perform subsequent calendering processing on the PVC film, thus achieving closed-loop multi-axis coordinated control.

[0096] This embodiment first analyzes the thickness distribution of scanning points on each roller at each scanning moment in the initial processing stage, and evaluates the degree of non-uniformity caused by temperature influence in the initial processing stage. This operation avoids the problem of uneven surface distribution caused by heat dissipation at both ends of the roller, and can improve the accuracy of subsequent speed control. Then, based on the relationship between speed and temperature influence, the speed of each roller is initially adjusted in sequence. Then, based on the relative change of the degree of non-uniformity of the scanning points on the roller in the intermediate processing stage and the initial processing stage after speed adjustment, the improvement of film uniformity after roller speed adjustment is evaluated. Based on the evaluation results, it is determined whether to continue to adjust the roller speed, so that the speed of each roller synchronously approaches the optimal speed. This realizes closed-loop multi-axis coordinated control of the entire calendering process, avoids the impact of excessively large or small speed ratio differences between adjacent rollers on the calendering quality of PVC film, and reduces the error impact of single control on the processing process, ensuring the production quality of PVC film calendered products.

[0097] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of multi-axial synergistic processing of PVC films, characterized in that, The method comprises the following steps: Obtaining the thickness of different scanning points on each roller shaft in the initial processing stage of the PVC film; According to the thickness distribution of the scanning points on each roller shaft at each scanning moment in the initial processing stage, the unevenness degree corresponding to the scanning points on each roller shaft in the initial processing stage is obtained; and the rotation speed of each roller shaft is adjusted in sequence according to the unevenness degree corresponding to the scanning points on each roller shaft in the initial processing stage and the relative difference between the rotation speeds of adjacent roller shafts; According to the relative change of the unevenness degree corresponding to the scanning points on the roller shafts in the initial processing stage and the intermediate processing stage, the improvement amplitude of the film uniformity after the adjustment of the rotation speed of the roller shafts is obtained; the intermediate processing stage is the stage after the initial adjustment of the rotation speed of the roller shafts; the overall distribution of the improvement amplitude of the film uniformity after the adjustment of the rotation speed of all the roller shafts is comprehensively considered to determine whether to continue adjusting the rotation speed of each roller shaft until the preset condition is met; and the PVC film is processed by using the adjusted rotation speed of the roller shafts.

2. A multi-axial synergic process for the production of PVC films according to claim 1, characterized in that, According to the thickness distribution of the scanning points on each roller shaft at each scanning moment in the initial processing stage, the unevenness degree corresponding to the scanning points on each roller shaft in the initial processing stage is obtained, which comprises: For any moment in the initial processing stage: In the scanning area on the roller shaft to be analyzed at the moment, the scanning points on the line segment passing through the center point of the scanning area and perpendicular to the central axis of the roller shaft are recorded as candidate scanning points; For any candidate scanning point: the scanning points on the line segment passing through the candidate scanning point and parallel to the central axis of the roller shaft and located on the two sides of the candidate scanning point are recorded as the left scanning point of the candidate scanning point and the right scanning point of the candidate scanning point, respectively; and the uniformity factor of the candidate scanning point at the moment is obtained according to the thickness difference between the left scanning point and the right scanning point and the next scanning point adjacent thereto and the distance between the left scanning point and the right scanning point and the candidate scanning point; According to the overall distribution of the uniformity factors of all the candidate scanning points at all the moments in the initial processing stage, the unevenness degree corresponding to the scanning points on the roller shaft to be analyzed in the initial processing stage is obtained; The roller shaft to be analyzed is any roller shaft except the first-stage roller shaft.

3. A multi-axial synergic process for the production of PVC films according to claim 2, characterized by the fact that, The uniformity factor of the candidate scanning point at the moment is obtained according to the thickness difference between the left scanning point and the right scanning point and the next scanning point adjacent thereto and the distance between the left scanning point and the right scanning point and the candidate scanning point, which comprises: The thickness difference between each left scanning point and the next scanning point adjacent thereto is recorded as the thickness difference corresponding to each left scanning point, and the thickness difference between each right scanning point and the next scanning point adjacent thereto is recorded as the thickness difference corresponding to each right scanning point. The normalized result of the distance between the left scanning point and the any candidate scanning point is used to weight the corresponding thickness difference, and the normalized value of the weighted result corresponding to all left scanning points of the any candidate scanning point is recorded as a left characteristic value; The average of the left characteristic value and the right characteristic value is used as a uniformity factor of the any candidate scanning point at the any time.

4. The multi-axial synergic process for PVC film according to claim 2, characterized in that, The overall distribution of the uniformity factors of all candidate scanning points at all times in the initial processing stage is used to obtain the uneven performance degree of the scanning points on the analyzed roller shaft in the initial processing stage, including: The average value of the uniformity factors of all candidate scanning points at each time in the initial processing stage is recorded as a first average value corresponding to each time in the initial processing stage, respectively. The average value of the first average values corresponding to all times in the initial processing stage is determined as the uneven performance degree of the scanning points on the analyzed roller shaft in the initial processing stage.

5. A method of multi-axial synergistic processing of PVC film as claimed in claim 1 wherein, The rotational speeds of the rollers are sequentially preliminarily adjusted according to the uneven performance degrees of the scanning points on the rollers in the initial processing stage and the relative difference between the rotational speeds of adjacent rollers, including: For the second-level roller, a first difference value between a constant 1 and the uneven performance degree of the scanning points on the second-level roller in the initial processing stage is calculated, and the product of the first difference value and the rotational speed of the second-level roller in the initial processing stage is used as the adjusted rotational speed of the second-level roller and is preliminarily adjusted; The adjusted rotational speed of the third-level roller is determined and preliminarily adjusted according to the adjusted rotational speed of the second-level roller, the requirement of the rotational speed ratio between the third-level roller and the second-level roller corresponding to the target thickness of the thermal paper; The adjusted rotational speed of the fourth-level roller is determined and preliminarily adjusted according to the adjusted rotational speed of the third-level roller, the requirement of the rotational speed ratio between the fourth-level roller and the third-level roller corresponding to the target thickness of the thermal paper; The total number of the rollers is 4.

6. A multi-axial synergic process for the production of PVC films according to claim 1, characterized by the fact that, The improvement amplitude of the film uniformity after the adjustment of the rotational speeds of the rollers is obtained according to the relative change of the uneven performance degrees of the scanning points on the rollers in the intermediate processing stage and the initial processing stage, including: A first ratio value between the uneven performance degree of the scanning points on each roller in the intermediate processing stage and the uneven performance degree of the scanning points on the same roller in the initial processing stage is calculated; The improvement amplitude of the film uniformity after the adjustment of the rotational speed of each roller is obtained according to the first ratio value corresponding to each roller and the level serial number of the roller.

7. A multi-axial synergic process for the production of PVC films according to claim 6, characterized by the fact that, The improvement amplitude of the film uniformity after the adjustment of the rotational speed of each roller is obtained according to the first ratio value corresponding to each roller and the level serial number of the roller, including: The product of the first ratio value corresponding to each roller and the level serial number of the roller is used as the improvement amplitude of the film uniformity after the adjustment of the rotational speed of each roller, respectively.

8. A multi-axial synergic process for the production of PVC films according to claim 1, characterized by the fact that, The overall distribution of the film uniformity improvement range after adjusting the rotation speed of all the roller shafts is comprehensively considered to determine whether to continue adjusting the rotation speed of each roller shaft until a preset condition is met, including: Adjusting the rotation speed of the roller shafts multiple times; For each rotation speed adjustment, a total improvement value function is determined according to the film uniformity improvement range after adjusting the rotation speed of all the roller shafts, and a control degree is determined according to the change of the total improvement value function; if the control degree is greater than a preset control threshold, the adjustment of the rotation speed of all the roller shafts is stopped.

9. A multi-axial synergic process for the production of PVC films according to claim 8, characterized by the fact that, The control degree is determined according to the change of the total improvement value function, including: For any adjustment, a control degree corresponding to the adjustment is obtained according to a function value of a total improvement value function corresponding to the adjustment and an absolute value of a first derivative value of the total improvement value function corresponding to the adjustment, the function value and the control degree are in a positive correlation, and the absolute value and the control degree are in a negative correlation.

10. A PVC film calendering device for carrying out the method of claim 1, characterized in that The device comprises a support structure and a shell, a first-stage roller shaft, a second-stage roller shaft, a third-stage roller shaft, a fourth-stage roller shaft, a heating module, a driving shaft, a laser thickness gauge, a data processing module, a central control panel, and a cooling conveying roller.

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