Coating process for coated aluminum coil based on precise positioning

Abstract

The application discloses a coating process of a coated aluminum coil based on accurate positioning. The process comprises the following steps: pretreating the surface of the aluminum coil substrate; configuring parameters of a coating device according to specification parameters of the aluminum coil to be coated and target coating requirements, and conveying the aluminum coil to be coated to a coating area; coating paint on the surface of the aluminum coil to be coated by using a coating head; determining the flow and diffusion characteristics of the paint according to coating state data, and identifying a paint flow influencing area in combination with an aluminum coil running state; dynamically regulating the transverse position of the coating head, the feeding parameters and the coating parameters based on the flow influencing area; and baking and curing the coated aluminum coil and winding it. The application realizes high-consistency coated products with neat coating boundaries, uniform film thickness and flat plate shape by real-time sensing of the coating state and identification of the flow influencing area, and linkage regulation of the position of the coating head and the coating parameters to keep the actual coating boundary consistent with the target boundary.

Description

Technical Field

[0001] This invention relates to the field of coating technology for coated aluminum coils, and more particularly to a coating process for coated aluminum coils based on precise positioning. Background Technology

[0002] Coating aluminum coils is one of the core technologies in the field of composite material preparation, and its coating quality directly affects the appearance and service life of the finished product. During the coating process, the flow and diffusion behavior of the coating on the aluminum coil surface and the positional accuracy of the coating boundary are key factors determining the consistency of coating width, uniformity of film thickness, and edge neatness. Currently, some coating production lines have introduced machine vision technology to identify surface defects after coating and adjust parameters such as roller coating pressure and roller speed ratio accordingly. Taking the Chinese invention patent application with publication number CN118681765A as an example, this solution acquires images of aluminum coils after coating, identifies surface quality problems such as stripe defects and bubbles, and adjusts process parameters such as roller coating pressure and roller speed ratio based on the defect identification results. However, visual inspection is a "post-event" or "near real-time" method, which is difficult to perceive the dynamic flow and diffusion process of the coating and the boundary offset trend at the moment of coating. At the same time, this solution cannot quantitatively obtain multi-dimensional dynamic information such as lateral offset, tension fluctuation, and changes in coating rheological properties during the operation of the aluminum coil, and cannot spatially locate and target the affected area based on this information. This makes it difficult to effectively suppress core problems such as coating boundary misalignment, paint overflow, or undercoating. Summary of the Invention

[0003] Therefore, the present invention needs to provide a coating process for coated aluminum coils based on precise positioning to solve at least one of the above-mentioned technical problems.

[0004] To achieve the above objectives, a coating process for coated aluminum coils based on precise positioning includes: Obtain aluminum coil substrate and coating, pre-treat the surface of aluminum coil substrate to obtain aluminum coil to be coated; The coating equipment is configured with parameters according to the specifications of the aluminum coil to be coated and the target coating requirements, and the aluminum coil to be coated is transported to the coating area. The coating head is used to apply the coating to the surface of the aluminum coil to be coated, and the running status and coating status data of the aluminum coil are collected in real time. The coating state data is used to determine the coating casting and diffusion characteristics, and the coating casting influence area is identified in combination with the aluminum coil operating status. Based on the influence area of ​​the casting process, the lateral position of the coating head, the feeding parameters, and the coating parameters are dynamically adjusted to ensure that the actual coating boundary is consistent with the target coating boundary, thereby obtaining coated aluminum coils. The coated aluminum coil is baked and cured and then wound up.

[0005] This invention constructs a mechanism for determining coating diffusion characteristics based on the coupling analysis of fluid properties and spatial boundaries by real-time acquisition of aluminum coil running status and coating status data. This mechanism accurately identifies the coating diffusion influence area, breaking the traditional "black box" state where coating spreading behavior is invisible and boundary offset is uncontrollable, significantly improving the perception of the coating dynamic process and spatial positioning accuracy. Simultaneously, based on the diffusion influence area, multi-parameter collaborative dynamic control is performed on the lateral position of the coating head, pump flow rate, and coating roller speed, ensuring that the actual coating boundary and the target coating boundary remain consistent in real time, effectively avoiding overflow and undercoating defects. When the diffusion exceeds the safety threshold, it is rapidly suppressed by simultaneously reducing the pump flow rate and aluminum coil speed, enhancing the ability to cope with extreme conditions. Finally, baking curing and tension straightening to relieve stress ensure neat coating boundaries, uniform film thickness, and flat plate shape, greatly improving coating quality consistency and finished product yield. Attached Figure Description

[0006] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the coating process of the aluminum coil based on precise positioning according to the present invention. Figure 2 for Figure 1 A detailed flowchart illustrating the steps involved in determining the casting and diffusion characteristics of a coating based on coating state data. Figure 3 for Figure 1 A detailed flowchart illustrating the steps involved in identifying the area affected by paint flow. Detailed Implementation

[0007] The technical method of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0008] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor methods and / or microcontroller methods.

[0009] It should be understood that although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are used merely to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0010] To achieve the above objectives, please refer to Figure 1 This invention provides a coating process for coated aluminum coils based on precise positioning, comprising: Step S1: Obtain aluminum coil substrate and coating, pre-treat the surface of aluminum coil substrate to obtain aluminum coil to be coated; In this step, aluminum coil substrate and matching coating are obtained. The substrate surface is sequentially subjected to roll flattening, cleaning and degreasing, and chemical activation treatment to form a chemical conversion layer on the surface, thereby removing oxide scale and improving surface activity, resulting in the aluminum coil to be coated. During the roll flattening process, the flattening tension on the aluminum coil is controlled at 800 to 1500 N to keep the aluminum coil substrate flat and avoid excessive stretching that could damage the sheet shape. During the cleaning and degreasing process, a temperature of 50 to 60 degrees Celsius is used. A degreasing cleaning solution is used, with the spray pressure controlled at 0.3 to 0.5 MPa, to remove rolling oil and contaminants from the surface of the aluminum coil. After activation treatment, a chromium-free chemical conversion layer is formed, with the thickness of the chemical conversion layer controlled at 50 to 200 nm and the treatment time controlled at 3 to 5 seconds. Through chemical conversion layer treatment, the adhesion and corrosion resistance of the coating to the aluminum substrate are significantly improved, providing a uniform, clean, and highly active substrate for coating, reducing the risk of coating blistering or peeling, and ensuring the consistency of finished product quality.

[0011] Step S2: Configure the coating equipment parameters according to the specifications of the aluminum coil to be coated and the target coating requirements, and transport the aluminum coil to be coated to the coating area; In this step, based on the specifications of the aluminum coil to be coated, such as width and thickness, and coating requirements such as target film thickness and coating width, the coating head gap, initial pump flow rate, coating roller speed, and traction tension are preset and configured, and the aluminum coil is smoothly conveyed to the coating area. This achieves precise matching between equipment parameters and batch specifications, avoids initial coating deviations caused by generic settings, reduces waste in the first stage, and improves production preparation efficiency and batch changeover stability.

[0012] Step S3: Apply the coating to the surface of the aluminum coil to be coated using the coating head, and collect data on the running status and coating status of the aluminum coil in real time; In this step, a coating head is used to evenly coat the surface of the moving aluminum coil. Simultaneously, online sensors collect real-time data on the coil's running speed, lateral offset, tension, coating viscosity, pump flow rate, and coating roller speed, forming a multi-dimensional data set. The online viscometer used for coating viscosity detection has a measurement range of 10 to 1000. The lateral offset detection range is 50mm. Establish a comprehensive, real-time process awareness system to enable the system to promptly capture operational fluctuations and enhance process controllability.

[0013] Step S4: Determine the coating's casting and diffusion characteristics based on the coating status data, and identify the coating's casting influence area in conjunction with the aluminum coil's operating status; In this step, the initial casting tendency is calculated based on the coating viscosity and pump flow rate, then dynamically corrected using roller speed and aluminum coil speed. Finally, the actual casting diffusion characteristics are determined by combining the tension value. Simultaneously, the coating boundary is calibrated using the lateral offset method and compared with the casting diffusion boundary to identify the casting influence area. This achieves a quantitative characterization of the coating spreading behavior and spatial boundary deviation, accurately locates overflow or undercoated areas, provides clear spatial coordinates and directional basis, and avoids blind adjustments.

[0014] Step S5: Based on the casting influence area, dynamically adjust the lateral position of the coating head, the feeding parameters and the coating parameters to ensure that the actual coating boundary is consistent with the target coating boundary, and obtain the coated aluminum coil; In this step, based on the identified areas affected by the casting process, the lateral position of the coating head, the pump flow rate, and the coating roller speed are adjusted in a coordinated manner. When the casting boundary exceeds a safety threshold, the pump flow rate and the aluminum coil conveying speed are simultaneously reduced until the actual coating boundary returns to within the target boundary range. The safety threshold is set based on the effective width of the aluminum coil and the trimming allowance, controlling that the distance between the casting diffusion boundary on one side and the target coating boundary does not exceed 1.5 mm. When the casting diffusion boundary on either side is detected to exceed the above threshold, the pump flow rate and aluminum coil conveying speed are adjusted in a coordinated manner. Through multi-parameter coordinated control, boundary deviations are quickly and accurately eliminated, effectively suppressing casting expansion, ensuring consistency in coating width and film thickness, significantly improving finished product accuracy, and reducing material waste.

[0015] Step S6: Bake and cure the coated aluminum roll and then rewind it.

[0016] In this step, the coated aluminum coil is placed in an oven for gradient heating and curing, followed by rapid cooling in a cooling section. Then, it is stretched and bent through a tension leveler to eliminate internal stress, and finally, it is wound up. The curing process ensures the mechanical properties and weather resistance of the coating, while the tension leveling process effectively eliminates heat-induced deformation and winding stress, ensuring the flatness of the finished sheet.

[0017] In one embodiment, obtaining an aluminum coil substrate and a coating, and pretreating the surface of the aluminum coil substrate to obtain an aluminum coil to be coated includes: The aluminum coil substrate is unwound and conveyed, and then subjected to rolling flattening, cleaning and activation treatments in sequence. A chemical conversion layer is formed on the surface of the aluminum coil substrate to form an aluminum coil to be coated.

[0018] In this embodiment, the coiled aluminum substrate is mounted on an unwinding machine, unwound under constant tension, and sequentially conveyed through multiple sets of roller flattening devices. These flattening devices employ arc-shaped stretching rollers in conjunction with pinch rollers to apply lateral stretching and longitudinal flattening to the aluminum coil, effectively eliminating the curling stress and edge wavy wrinkles formed during the winding process, resulting in a flat and taut surface. The coil tension is monitored in real time during the flattening process to prevent excessive stretching and damage to the sheet shape.

[0019] The flattened aluminum coils are sequentially passed through an alkaline degreasing cleaning section, a secondary water washing section, and an acid pickling neutralization section. The alkaline degreasing section uses a combination of spraying and brushing to remove rolling oil, dust, and particulate contaminants adhering to the surface of the aluminum coils. The water washing section uses high-pressure spraying of deionized water for rinsing. The acid pickling section uses a dilute acid solution to neutralize residual alkali and slightly etch the oxide layer. Each cleaning section is equipped with a circulating filtration system and an automatic liquid level compensation device, and the cleaning temperature is controlled between 50 and 60 degrees Celsius to ensure stable cleaning results.

[0020] The cleaned aluminum coils are transported to an activation treatment tank, where they are sprayed or immersed in a chromium-free conversion treatment solution containing titanium or zirconium compounds. The treatment time is controlled between 3 and 5 seconds, causing micro-etching and chemical conversion reactions on the surface of the aluminum coils, generating a uniform chemical conversion layer with a thickness of 50 to 200 nanometers. After a final water wash and hot air drying, the pretreatment process is complete, yielding the aluminum coil to be coated. The concentration and pH value of the bath solution are monitored in real time during the treatment process to ensure the stability of the conversion layer quality.

[0021] Roller flattening eliminates the inherent curling memory and localized deformation of the aluminum coil, forming a geometrically stable planar substrate. This ensures uniformity in processing results across all stages, preventing cleaning dead zones or uneven activation due to poor sheet shape, thus reducing coating defects at the source. Multi-stage chemical cleaning thoroughly removes grease, dirt, and the natural oxide layer from the aluminum coil surface, achieving a highly clean surface. This significantly improves the film quality and adhesion of the chemical conversion layer, while preventing contaminants from precipitating during activation or coating, ensuring long-term corrosion resistance and aesthetic purity. The chemical conversion layer not only resists short-term corrosion but also forms a porous anchoring structure at the microscopic level, creating a dual bond of chemical bonding and physical interlocking with the coating. This significantly improves coating adhesion and enhances the salt spray resistance of the coated aluminum coil.

[0022] In one embodiment, the coating status data includes one or more of the following: coating viscosity, coating head pump flow rate, coating roller speed, aluminum coil conveying speed, aluminum coil tension, and aluminum coil lateral offset.

[0023] In this embodiment, an online rotational viscometer or vibratory viscosity sensor is installed in series in the coating supply pipeline to monitor the dynamic viscosity value of the coating in real time during the conveying process. The sensor signal is converted into a standard analog or digital quantity by a transmitter and transmitted to the control system. The sampling frequency is no less than 1 time / second to capture the instantaneous changes in viscosity with temperature or batch fluctuations. A high-precision electromagnetic flow meter or mass flow meter is installed at the outlet of the feed pump at the coating head to measure the actual pumped output of the coating in real time. The flow signal is compared with the pump drive frequency feedback value to verify whether there is a deviation between the pumping command and the actual output, ensuring that the flow data is true and reliable. A rotary encoder is installed on the drive motor shaft of the coating roller to collect the actual rotation speed of the coating roller in real time and feed the rotation speed signal back to the control system. The encoder resolution is no less than 1024 pulses / revolution, which can accurately reflect the instantaneous change of the roller surface linear speed and is used for speed matching calculation with the aluminum coil conveying speed. A speed encoder or laser speed sensor is installed on the aluminum coil traction roller or drive roller to collect the longitudinal running speed of the aluminum coil in real time. To address slippage, a non-contact laser velocimeter is used to cross-verify with the encoder signal, ensuring the authenticity and redundancy reliability of the speed data. Tension detection elements are installed on floating rollers or tension sensor rollers along the aluminum coil's running path to collect the longitudinal tension value of the aluminum coil in real time. The tension signal participates in the closed-loop speed regulation of the unwinding and rewinding machines, and is also correlated with the lateral offset of the aluminum coil to determine whether tension fluctuations cause deviation. Edge correction sensors, such as ultrasonic or photoelectric edge detection sensors, are installed on the aluminum coil inlet side and in front of the coating head to detect the lateral positional offset of the aluminum coil edge in real time and transmit it to the control system as a digital signal, serving as an important input variable for lateral position tracking of the coating head.

[0024] Real-time viscosity data acquisition enables the system to predict coating spreading trends, avoiding uneven film thickness or uncontrolled casting due to viscosity fluctuations. Pump flow rate directly determines the total coating material supply; real-time monitoring can promptly detect flow drift caused by pump wear, pipe blockage, or leaks, ensuring the coating head output matches the target setting and preventing overflow due to overfeeding or missed coating due to underfeeding. The coating roller speed directly affects the shear force and transfer amount of the coating material. Real-time speed data is used to correct the casting diffusion characteristic calculations and serves as execution feedback for adjusting the target coating roller speed, ensuring precise roller speed adjustment and achieving a dynamic balance between coating transfer amount and coating speed. The aluminum coil conveyor speed determines the substrate's residence time at the coating station, a necessary parameter for calculating actual coating consumption and casting displacement. It also provides execution feedback for speed-linked control, ensuring the closed-loop control accuracy of speed adjustment. Real-time tension data is not only used for substrate tension correction in casting diffusion characteristic calculations but also provides early warning of lateral offset risks caused by abnormal tension, providing indirect judgment for adjusting the coating head's lateral position. Real-time acquisition of lateral offset allows the system to dynamically track the actual movement of the aluminum coil, ensuring that the coating head follows the lateral position synchronously and avoiding coating boundary offset caused by aluminum coil deviation.

[0025] In one embodiment, reference Figure 2 The determination of the coating's casting and diffusion characteristics based on coating state data includes: Step S411: Determine the initial casting state of the coating based on the coating viscosity and the pump flow rate of the coating head; Step S412: Correct the initial casting state according to the coating roller speed and aluminum coil conveying speed; Step S413: Based on the corrected initial casting state, determine the casting and diffusion characteristics of the coating in combination with the aluminum coil tension.

[0026] In this embodiment, the real-time collected coating viscosity value and coating head pump flow rate value are substituted into a pre-established initial casting model to calculate the initial casting state parameters of the coating. This model is constructed based on the constitutive equations of Newtonian or non-Newtonian fluids in fluid mechanics, using the theoretical spreading area or spreading rate of the coating after transfer from the coating head to the aluminum coil surface per unit time as a characterization index, forming an uncorrected baseline casting tendency value. The model coefficients are obtained through prior experimental calibration and are pre-stored in the control system's database.

[0027] The real-time collected data on the coating roller speed and aluminum coil conveying speed are incorporated into the correction process. The speed ratio is calculated to obtain the linear speed ratio, which serves as a correction coefficient for the initial casting state. When the linear speed ratio is greater than 1, the linear speed of the coating roller surface is higher than the aluminum coil running speed. The coating material carried on the roller surface is subjected to positive shear and accelerated extrusion, increasing the casting tendency. When the linear speed ratio is less than or equal to 1, the coating transfer tends to be smoother, and the casting tendency weakens. The initial casting state is then corrected linearly or nonlinearly based on the linear speed ratio to obtain the first corrected casting state.

[0028] The real-time collected aluminum coil tension is used as a secondary correction factor to further adjust the first-correction casting state, ultimately determining the casting and diffusion characteristics of the coating. Aluminum coil tension affects the microscopic tensile deformation and tension of the aluminum coil surface, altering the spreading and wetting conditions of the coating droplets on the substrate surface. When the tension increases, the aluminum coil surface becomes smoother and denser, the coating spreading resistance increases slightly, and the casting and diffusion range converges accordingly; conversely, the casting range expands slightly when the tension decreases. A slight weighted correction is applied to the first-correction casting state based on the tension value, outputting the final casting and diffusion characteristic value.

[0029] Viscosity and pump flow rate are the two most direct factors determining the spreading behavior of coatings after discharge. Viscosity reflects the internal frictional resistance of the coating, while flow rate reflects the amount of material supplied per unit time. By coupling these two factors through a model, the basic spreading trend of the coating at the moment of transfer from the coating head can be quickly quantified, avoiding subjective biases caused by directly relying on empirical values. The speed matching relationship between the coating roller and the aluminum coil directly affects the shear rate and transfer efficiency of the coating in the transfer gap. Introducing the speed ratio between the two for correction can incorporate the influence of mechanical motion variables on coating spreading behavior into the quantitative system, making the calculation of casting characteristics closer to actual coating conditions and improving the accuracy of casting diffusion characteristic prediction. Aluminum coil tension is a mechanical factor affecting the geometry and surface energy state of the substrate. Although it is not a direct fluid parameter, it cannot be ignored in continuous high-speed coating. Using aluminum coil tension as the final correction factor can compensate for the influence of substrate state that cannot be covered by simply relying on fluid and motion parameters, making the final determined casting diffusion characteristics more comprehensive.

[0030] In one embodiment, reference Figure 3 The identification of the area affected by coating flow includes: Step S421: Calibrate the reference coating boundary of the aluminum coil to be coated according to the lateral offset of the aluminum coil; Step S422: Determine the actual casting and diffusion boundary of the coating based on its casting and diffusion characteristics; Step S423: Identify the casting influence area based on the reference coating boundary and the actual casting diffusion boundary.

[0031] In this embodiment, based on the real-time acquired lateral offset of the aluminum coil, combined with the pre-set target coating width and the actual width of the aluminum coil, the theoretical coating boundary lines on the left and right sides are dynamically determined in the width direction of the aluminum coil. Specifically, taking the actual running center line of the aluminum coil as a reference, it is offset to the left and right by half of the target coating width, and then the lateral offset is superimposed for position compensation to obtain the left reference boundary line and the right reference boundary line. The area between the two is the target coating area.

[0032] By combining the casting diffusion characteristic value with the actual lateral working position of the coating head and the width of the coating head outlet, the actual left and right boundary positions of the coating after spreading on the aluminum coil surface are calculated. Based on the theoretical coating width of the coating head, according to the spreading rate and range represented by the casting diffusion characteristic value, the corresponding diffusion compensation amounts are extrapolated along the left and right sides respectively to obtain the actual left casting diffusion boundary and the actual right casting diffusion boundary.

[0033] The reference coating boundary and the actual flow diffusion boundary are spatially superimposed and compared to calculate the difference regions on the left and right sides. When the difference region is greater than 0, it indicates that the actual flow boundary exceeds the reference boundary, and this exceeding area is the flow-affected area; when the difference region is less than 0, it indicates that the actual flow boundary does not reach the reference boundary, and this insufficient area is the undercoated area; when the difference region is equal to 0, it indicates that the boundaries coincide and there is no flow effect. Based on the sign and size of the difference region, the control system outputs characteristic information such as the lateral position, width, and severity of the flow-affected area.

[0034] During high-speed operation, aluminum coils inevitably experience lateral swaying. If a fixed mechanical position is used as the boundary reference, the actual coating position will deviate from the target area due to the coil's swaying. By introducing real-time lateral offset to dynamically calibrate the reference boundary, the target coating area remains relatively fixed relative to the actual position of the aluminum coil, eliminating the systematic positioning error caused by coil misalignment. After being transferred to the aluminum coil surface, the coating does not remain stationary at the coating head projection position but exhibits a certain degree of spreading and flow. This spreading behavior is quantified through the characteristics of the coating diffusion, converting the fluid dynamics into a measurable spatial boundary offset, making the actual coating boundary calculable. Through spatial overlay comparison, the coating diffusion effect is visually mapped to a specific coordinate region, accurately locating the position and magnitude of coating deviations, eliminating reliance on operator subjective judgment for control. Simultaneously, it distinguishes between two different types of deviations: overflow and undercoating, significantly improving the targeting and efficiency of control.

[0035] Furthermore, in another embodiment, after identifying the area affected by the casting effect, the method further includes: Record the left and right difference region values ​​at multiple consecutive sampling times to construct a time series sequence of difference regions; Calculate the rate of change and acceleration of the time series in the region of difference; When the rate of change is positive and the acceleration continues to increase, it is determined that the area affected by the spill is expanding rapidly, and an early warning signal is output and a control pre-action is triggered. When the rate of change is negative and the acceleration converges to 0, it is determined that the area affected by the flow is naturally fading, and the current parameters are maintained.

[0036] In this embodiment, after identifying the area affected by the casting effect, the control system further introduces time-varying characteristic analysis of the difference area.

[0037] Specifically, after identifying the areas affected by the flow, the control system does not directly enter the control phase. Instead, it first establishes a time-series monitoring window for the difference regions. Values ​​of the left and right difference regions are continuously collected and recorded at a fixed sampling period for multiple consecutive sampling times, constructing time-series sequences for the left and right difference regions, respectively.

[0038] The control system performs numerical difference calculations on the time series to determine the changes in the left and right difference region values ​​at each time point relative to the previous time point. This allows for the calculation of the change rates of the left and right difference regions. Furthermore, the change rates are again differentiated to obtain the accelerations of the left and right difference regions. The change rate reflects the speed at which the area affected by the flow spread expands or shrinks, while the acceleration reflects the increasing or decreasing trend of this change rate itself. Together, they constitute the time-varying characteristic parameter set of the difference region.

[0039] The control system matches the calculated set of time-varying characteristic parameters with preset multi-level early warning thresholds and executes a graded prediction strategy. When the rate of change is positive and the acceleration continues to increase, it indicates that the coating influence area is expanding at an increasingly faster rate, and the system determines that the current coating state is rapidly becoming unstable. At this time, the control system outputs a secondary early warning signal in advance before the coating boundary exceeds the limit and triggers pre-regulation actions, including increasing the coating roller speed to the intermediate value at a lower rate and slightly reducing the pump flow rate in advance, so that the system begins to adjust in a safe direction before the coating boundary reaches the critical state, effectively counteracting the upcoming trend of increased coating. When the rate of change is positive but the acceleration approaches zero or begins to decrease, it indicates that the coating influence area is still expanding but the speed has slowed down, and the system determines that the expansion trend is decaying. At this time, only a primary early warning signal is output for the operator's reference, and automatic regulation is not triggered to avoid over-adjustment. When the rate of change is negative and the acceleration converges to zero, it indicates that the coating influence area is naturally receding at a stable rate, and the system determines that the current coating state is stabilizing, maintaining all current parameters without any adjustment to avoid unnecessary disturbances.

[0040] The system synchronously uses time-varying characteristic parameters to extrapolate short-term trends, estimating the predicted value of the area affected by the flow after several sampling periods based on the current rate of change and acceleration. This predicted value is then compared with a safety threshold. If the predicted value will exceed the threshold within the next 2 seconds, the system triggers a control action in advance; if the predicted value remains below the threshold, the system maintains monitoring status.

[0041] Building upon static spatial positioning, the system incorporates time-varying characteristic analysis of different regions, enabling it to perceive dynamic trends. This allows it to predict the direction of coating state changes in advance from the expansion speed and acceleration trend of the coating boundary, avoiding passive waiting for deviations to accumulate to an uncontrollable level before making significant adjustments. This significantly shortens the control response delay and reduces the risk of overshoot. Simultaneously, through a hierarchical prediction strategy and trend extrapolation, differentiated responses are achieved, making control behavior more precise, smooth, and energy-efficient, thus comprehensively improving the intelligence level of the coating system and the stability of the production process.

[0042] In one embodiment, dynamic control includes adjusting one or more of the following: adjusting the lateral position of the coating head, adjusting the pump flow rate of the coating head, adjusting the rotation speed of the coating roller, and adjusting the running speed of the aluminum coil.

[0043] In this embodiment, when the identified casting-affected area exhibits a unilateral offset characteristic—that is, the difference between the left and right sides is significantly greater than that on the other side—it indicates a positional deviation between the actual coating centerline and the aluminum coil centerline. In this case, lateral position adjustment of the coating head is prioritized. The control system calculates the required lateral movement amount and direction of the coating head based on the difference between the left and right sides of the difference area, and drives the servo motor to move the entire coating head along the width of the aluminum coil until the difference values ​​on the left and right sides tend to balance and the absolute values ​​are controlled within the allowable deviation range. During the movement, the real-time changes in the lateral offset of the aluminum coil are monitored simultaneously, forming a position tracking closed loop.

[0044] When the identified areas of influence from the coating flow show a symmetrical excess on both sides—that is, both the left and right difference areas are positive and approximately equal—it indicates that the total amount of material supplied is too large relative to the current coating speed. The control system determines a pump flow correction coefficient based on the viscosity trend of the coating material and adjusts the drive frequency of the feed pump via a frequency converter. This changes the amount of coating output per unit time from the coating head, causing the actual coating flow boundaries on both sides to converge inward synchronously until the boundaries coincide with the reference boundary or return to within a safe threshold range.

[0045] When the coating spreads too widely in the affected area but the total feed volume is basically normal, it indicates that the coating is subjected to excessive shear force and carries too much during the transfer process. The control system calculates the target rotational speed of the coating roller based on the coating viscosity trend and the current coating diffusion characteristics. It then adjusts the roller speed to this target value via a frequency converter. By changing the speed ratio between the roller surface linear velocity and the aluminum coil speed, the positive shear extrusion effect on the coating in the transfer gap is reduced, thus narrowing the coating diffusion range to the target area.

[0046] When the extent of the coating's influence on the coating's boundary increases cumulatively with the length of the aluminum coil, it indicates that the dynamic response time of the coating's flow at the current coating speed is insufficient. The control system adjusts the speed of the traction drive motor to appropriately reduce the conveying speed of the aluminum coil, extending the coating's spreading and balancing time in the contact area between the coating head and the aluminum coil. This allows the coating to have more sufficient conditions to complete spreading within a limited range, while also reserving a response window for the coordinated control of pump flow rate and roller speed.

[0047] Adjusting the lateral position of the coating head allows for overall spatial translation of the coating area, quickly eliminating one-sided overflow or undercoating without altering process parameters such as paint output and coating speed. This avoids introducing new film thickness fluctuations due to adjustments in feed parameters, making it particularly suitable for scenarios involving aluminum coil misalignment or initial misalignment leading to boundary deviations. Adjusting the pump flow rate directly affects the feed source, controlling the total paint supply. It provides rapid and synchronous suppression of uniform overflow on both sides while maintaining symmetry in the coating width direction, preventing uneven film cross-sections caused by unilateral adjustments. Adjusting the coating roller speed alters the paint transfer shear conditions, optimizing paint spreading behavior without changing the total feed volume. This is particularly suitable for casting and diffusion scenarios where viscosity decreases, leading to increased fluidity, effectively avoiding insufficient film thickness caused by simply reducing the flow rate. Adjusting the running speed of aluminum coils intervenes in the flow and diffusion of coatings from a time perspective. By extending the coating duration, the coating is transferred and spread under more stable kinetic conditions. This method complements and buffers other control measures, and is especially suitable for dynamic flow suppression during high-speed coating. It also provides speed reduction coordination for multi-parameter linkage control, thereby improving the stability and fault tolerance of the overall control system.

[0048] In one embodiment, adjusting the coating head pump flow rate specifically involves: The pump flow correction factor for the coating head is determined based on the variation trend of the coating viscosity. Adjust the pump flow rate of the coating head according to the pump flow rate correction factor.

[0049] In this embodiment, the control system continuously receives real-time data from the online viscosity sensor, establishes a viscosity-time curve, and calculates the deviation and rate of change of the viscosity at the current moment relative to the previous moment or relative to the initial set value. When the deviation is positive, it indicates that the coating viscosity increases, the fluidity decreases, and the tendency to spread is weakened. According to the preset viscosity-flow correction mapping table, the corresponding pump flow correction coefficient k (k<1) is calculated, meaning that the pump flow needs to be appropriately reduced to avoid excessive material supply leading to an excessively thick film. When the deviation is negative, it indicates that the coating viscosity decreases, the fluidity increases, and the tendency to spread is intensified. The corresponding correction coefficient k (k>1) is calculated, meaning that the pump flow needs to be appropriately increased to compensate for the film thickness reduction caused by spreading and diffusion. The correction coefficient k is determined by piecewise linear interpolation or a nonlinear fitting formula based on experimental calibration to ensure that the coefficient changes continuously and smoothly with the viscosity deviation.

[0050] The calculated pumping flow correction factor is superimposed on the current pumping flow setpoint to obtain the actual pumping flow command value. This command value is sent to the variable frequency drive of the feed pump via analog or digital communication, adjusting the motor speed to change the pump's output displacement, thus synchronizing the actual pumping flow. During the adjustment process, the flow meter feedback value and the command value are continuously compared. If the deviation exceeds the allowable range, a second fine-tuning is performed until the feedback value matches the command value. When the coating viscosity returns to a normal level, the correction factor gradually returns to 1.0, and the pumping flow synchronously recovers to the initial setpoint.

[0051] If the pump flow rate is operated solely according to the initial set value without considering viscosity fluctuations, the actual coating thickness will decrease due to flow diffusion when the viscosity decreases, and insufficient flowability will lead to orange peel or missed coating when the viscosity increases. By dynamically determining the correction coefficient using both viscosity deviation and rate of change, real-time adaptation of the feed rate to the coating fluid characteristics is achieved, compensating for the impact of viscosity fluctuations on coating quality from the source. The correction coefficient is converted into specific flow commands and executed in a closed loop, ensuring that theoretical calculations are accurately translated into actual actions, avoiding execution deviations caused by open-loop adjustments. Simultaneously, a secondary fine-tuning mechanism is retained to compensate for the impact of hardware factors such as pump wear and changes in pipeline resistance on flow accuracy.

[0052] In one embodiment, adjusting the coating roller speed specifically involves: The target rotation speed of the coating roller is determined based on the viscosity variation trend and the casting diffusion characteristics of the coating, and the rotation speed of the coating roller is adjusted to the target rotation speed to reduce the coating casting range.

[0053] In this embodiment, the control system synchronously reads the real-time value of the current coating viscosity, the viscosity change rate, and the casting diffusion characteristic value, and inputs these three values ​​into a pre-constructed speed optimization model. This model is based on the mapping relationship between the coating roller speed and the casting diffusion range within different viscosity ranges. When the viscosity decreases and the casting diffusion characteristic value exceeds the preset range, the model calculates a target speed value higher than the current speed. The aim is to increase the shear rate and inertial force experienced by the coating during the transfer process by increasing the roller speed, thereby accelerating the detachment efficiency of the coating from the roller surface to the aluminum coil surface, reducing the residence time of the coating in the gap between the roller surface and the aluminum coil, and thus reducing the tendency of the coating to spread to both sides due to gravity or capillary action.

[0054] The calculated target rotational speed is sent as a speed command to the frequency converter of the coating roller drive motor. The rotational speed of the coating roller is steadily increased by adjusting the motor's power supply frequency until the actual rotational speed feedback value matches the target value. During the adjustment process, a PID control algorithm is used to set a reasonable acceleration slope to prevent sudden changes in rotational speed from causing paint splashing or abrupt changes in coating gap pressure. Once the actual rotational speed reaches the target value, the system continues to monitor the changing trend of the casting diffusion characteristic value. If the casting diffusion characteristic value gradually converges to the preset range, the current rotational speed is maintained; if the casting diffusion characteristic value still does not converge, a second fine-tuning is performed based on the deviation until the casting diffusion range narrows to the target area.

[0055] Coupling viscosity change trends with casting diffusion characteristics as a dual basis for determining the target rotation speed is more scientific than simply relying on experience-based roller adjustment. A decrease in viscosity indicates increased flowability, while the casting diffusion characteristic value directly quantifies the degree of spreading. Combining these two factors allows for precise calculation of the required rotation speed increment, avoiding excessive transfer or thinning of the film due to blindly raising the roller. This enables precise intervention through speed control, actively suppressing the escalating trend of casting diffusion from a shear dynamics perspective. Closed-loop speed regulation ensures accurate execution of the target rotation speed, avoiding deviations caused by open-loop adjustment or mechanical lag. A smooth acceleration strategy prevents sudden changes in rotation speed from impacting the stability of the coating gap, ensuring no secondary fluctuations in coating quality during adjustment. Simultaneously, a mechanism for tracking the adjustment effect is introduced, allowing for secondary fine-tuning based on the actual response of the casting diffusion characteristics, ensuring that the control ultimately achieves the predetermined goal.

[0056] In one embodiment, when the actual casting diffusion boundary exceeds a preset safe coating threshold, the coating head pump flow rate and aluminum coil conveying speed are reduced simultaneously until the actual casting diffusion boundary is reduced to within the preset safe coating threshold.

[0057] In this embodiment, the control system compares the actual casting diffusion boundary with a preset safety coating threshold boundary in real time. The safety coating threshold is set based on the effective width of the aluminum coil, the allowance for trimming, and the mechanical limits of the equipment, representing the maximum limit boundary that allows casting diffusion. When the left or right side of the actual casting diffusion boundary exceeds the threshold, the system determines that the current casting diffusion state has reached a dangerous level and triggers the emergency control procedure. Simultaneously, the excess amount is recorded as the basis for calculating subsequent control adjustments.

[0058] Upon triggering the emergency control procedure, the control system simultaneously sends speed reduction commands to the feed pump inverter and traction drive motor, achieving a synchronous reduction in the coating head pump flow rate and aluminum coil conveying speed. The reduction in pump flow rate and aluminum coil speed is determined by a control allocation algorithm based on the excess amount. The larger the excess, the greater the proportional reduction in both, but the aluminum coil speed is prioritized for reduction to extend the casting equilibrium time, with the pump flow rate reduction matched accordingly to maintain a relatively stable film thickness. During the control process, the real-time changes in the actual casting diffusion boundary are continuously monitored. Once the boundary begins to shrink and converge towards the threshold, the reduction rate is immediately reduced to prevent over-adjustment.

[0059] The system continuously tracks the positional changes of the actual coating diffusion boundary. Once both the left and right boundaries have receded within the safe coating threshold and remained stable for more than the set time, the emergency control operation is deemed successful. Subsequently, the control system gradually restores the aluminum coil conveying speed and pumping flow rate to the pre-control level or adjusts them to a new steady-state value at a slow rate. At the same time, it closely monitors the boundary change trend. Once it is confirmed that the threshold overshoot will not be triggered again, control is returned to the regular control module, and the normal coating production process is restored.

[0060] By setting a safe coating threshold and comparing it in real time, this judgment mechanism divides the degree of casting diffusion into a three-level state space. When conventional control methods fail to effectively curb the aggravation of casting, the threshold exceeding the limit judgment provides the system with a clear level switching signal, ensuring that extreme working conditions can be identified in a timely manner and trigger stronger intervention measures, avoiding casting runaway leading to material sticking to the aluminum coil edges, equipment contamination, or batch scrapping. Simultaneously reducing the pump flow rate and aluminum coil speed creates a superimposed inhibition effect, which has a stronger casting inhibition capability than adjusting either parameter alone. Reducing the pump flow rate reduces the total amount of material supplied per unit time, while reducing the aluminum coil speed extends the coating spreading equilibrium time. The two work together to quickly pull the casting boundary back within the safe threshold. At the same time, by dynamically monitoring boundary changes and adjusting the reduction rate in a timely manner, it effectively prevents over-adjustment from causing insufficient film thickness or excessive loss of production capacity, balancing the effectiveness of emergency handling and the agility of production recovery.

[0061] In one embodiment, baking, curing, and winding the coated aluminum coil includes: After the coated aluminum coil is conveyed to the oven for baking and curing, it is rapidly cooled and stress is eliminated by a tension leveler to complete the winding.

[0062] In this embodiment, the coated aluminum coil, after dynamic control and with the coating boundary meeting the standard, is smoothly introduced into a multi-stage hot air circulating oven via transition traction rollers. The oven is divided into a preheating section, a curing section, and a precooling section along the direction of aluminum coil travel. The temperature of each section is independently controllable, with the preheating section temperature controlled at 120°C. The temperature of the curing section is controlled at 230 to 260 degrees Celsius. The temperature of the precooling section is controlled at 80°C. This process ensures the coating sequentially completes the heating and stabilization, resin cross-linking and curing, and initial cooling stages. Temperatures are set for each stage based on the curing window of the coating resin, allowing the aluminum coil to sequentially complete solvent evaporation, resin melting and cross-linking, and complete curing during its journey, achieving the specified hardness, adhesion, and weather resistance. A plate thermometer is installed at the oven outlet to monitor the aluminum coil's exit temperature in real time, ensuring sufficient curing without overheating.

[0063] The high-temperature coated aluminum coils, after exiting the drying oven, are immediately sent to a forced air cooling section or a water-cooled jacket cooling section. High-pressure cold air or circulating cooling water is used to uniformly and rapidly cool the upper and lower surfaces of the aluminum coils, quickly reducing the temperature to 50°C. The cooling section is equipped with multiple independently adjustable air nozzles or water-cooling rollers to adjust the cooling intensity according to the thickness of the aluminum coil and the traveling speed, ensuring a uniform and controllable cooling rate and avoiding uneven cooling that could lead to differences in coating shrinkage stress or warping of the aluminum coil.

[0064] The rapidly cooled coated aluminum coil is fed into a tension leveler. Multiple sets of bending and straightening rollers, arranged in an alternating pattern, apply repeated bending and slight stretching to the coil, allowing it to release internal stresses caused by thermal expansion and contraction and curling during elasto-plastic deformation. The elongation rate is controlled between 0.3% and 1.0%. Tension and the insertion depth of the bending rollers are adjusted in real time according to the coil's thickness and width to ensure a flat, smooth sheet shape and eliminate waviness and warping after straightening.

[0065] After stress relief, the coated aluminum coil is conveyed to the winding machine by a traction device and tightly wound into a roll under constant tension control. The winding tension is set in a decreasing manner, with the initial core stage tension controlled at 1200N, gradually decreasing to 600N at the full roll stage as the roll diameter increases, to prevent excessive pressure on the inner ring, which could cause coating damage or core wrinkling. During the winding process, the coating appearance quality is monitored simultaneously, and a label is affixed to the end of the roll to indicate key information such as batch, specifications, and film thickness, completing the finished product warehousing.

[0066] The multi-stage temperature zone design avoids the pinhole or bubble defects caused by rapid solvent evaporation in a single high-temperature zone, while ensuring that the resin crosslinking degree meets process requirements, giving the coating excellent mechanical strength and chemical corrosion resistance. Rapid cooling prevents residual heat from causing slow coating flow or thermal aging after complete coating curing, and rapidly reduces the temperature of the aluminum coil substrate for subsequent straightening, effectively avoiding heat-induced defects such as orange peel, whitening, or adhesion degradation on the coating surface during cooling. After baking and rapid cooling, the aluminum coil inevitably accumulates internal thermal stress and uneven plastic deformation. If not eliminated, this will lead to sheet shape defects such as wavy edges, camber, or arching during subsequent storage or user processing. The straightening machine actively releases internal stress through bending and stretching, restoring the interfacial stress between the coating and the aluminum substrate to a new equilibrium, significantly improving the sheet shape quality of the finished product. The decreasing winding tension strategy effectively avoids coating marks or adhesion damage caused by excessive inner layer pressure when using large-diameter coils, ensuring consistent quality across the entire coil, both inner and outer rings. In conjunction with appearance monitoring and labeling traceability, the finished rolls are made traceable throughout the entire process from production to use.

[0067] Therefore, the embodiments should be considered as exemplary and non-limiting in all respects, and the scope of the invention is not limited by the foregoing description. Thus, all changes falling within the meaning and scope of the equivalents of the application are intended to be included within the scope of the invention.

[0068] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A coating process for coated aluminum coils based on precise positioning, characterized in that, include: Obtain aluminum coil substrate and coating, pre-treat the surface of aluminum coil substrate to obtain aluminum coil to be coated; The coating equipment is configured with parameters according to the specifications of the aluminum coil to be coated and the target coating requirements, and the aluminum coil to be coated is transported to the coating area. The coating head is used to apply the coating to the surface of the aluminum coil to be coated, and the running status and coating status data of the aluminum coil are collected in real time. The coating state data is used to determine the coating casting and diffusion characteristics, and the coating casting influence area is identified in combination with the aluminum coil operating status. Based on the influence area of ​​the casting process, the lateral position of the coating head, the feeding parameters, and the coating parameters are dynamically adjusted to ensure that the actual coating boundary is consistent with the target coating boundary, thereby obtaining coated aluminum coils. The coated aluminum coil is baked and cured, and then wound up.

2. The coating process for aluminum coils based on precise positioning according to claim 1, characterized in that, The process of obtaining the aluminum coil substrate and coating, and pre-treating the surface of the aluminum coil substrate to obtain the aluminum coil to be coated includes: The aluminum coil substrate is unwound and conveyed, and then subjected to rolling flattening, cleaning and activation treatments in sequence. A chemical conversion layer is formed on the surface of the aluminum coil substrate to form an aluminum coil to be coated.

3. The coating process for aluminum coils based on precise positioning according to claim 1, characterized in that, The coating status data includes one or more of the following: coating viscosity, coating head pump flow rate, coating roller speed, aluminum coil conveying speed, aluminum coil tension, and aluminum coil lateral offset.

4. The coating process for aluminum coils based on precise positioning according to claim 3, characterized in that, The determination of the coating's casting and diffusion characteristics based on coating state data includes: The initial casting state of the coating is determined based on the coating viscosity and the pump flow rate of the coating head; The initial casting state is corrected based on the coating roller speed and the aluminum coil conveying speed. Based on the corrected initial casting state, the casting and diffusion characteristics of the coating were determined in combination with the aluminum coil tension.

5. The coating process for aluminum coils based on precise positioning according to claim 3, characterized in that, The identified areas affected by coating flow include: The reference coating boundary of the aluminum coil to be coated is determined based on the lateral offset of the aluminum coil. Determine the actual casting diffusion boundary of the coating based on its casting diffusion characteristics; Identify the casting-affected area based on the reference coating boundary and the actual casting diffusion boundary.

6. The coating process for aluminum coils based on precise positioning according to any one of claims 1 to 5, characterized in that, The dynamic control includes adjusting one or more of the following: adjusting the lateral position of the coating head, adjusting the pump flow rate of the coating head, adjusting the rotation speed of the coating roller, and adjusting the running speed of the aluminum coil.

7. The coating process for aluminum coils based on precise positioning according to claim 6, characterized in that, The adjustment of the coating head pump flow rate specifically refers to: The pump flow correction factor for the coating head is determined based on the variation trend of the coating viscosity. Adjust the pump flow rate of the coating head according to the pump flow rate correction factor.

8. The coating process for aluminum coils based on precise positioning according to claim 6, characterized in that, The adjustment of the coating roller speed is specifically as follows: The target rotation speed of the coating roller is determined based on the viscosity variation trend and the casting diffusion characteristics of the coating, and the rotation speed of the coating roller is adjusted to the target rotation speed to reduce the coating casting range.

9. The coating process for aluminum coils based on precise positioning according to claim 6, characterized in that, When the actual casting diffusion boundary exceeds the preset safe coating threshold, the pump flow rate of the coating head and the conveying speed of the aluminum coil are reduced simultaneously until the actual casting diffusion boundary is reduced to within the preset safe coating threshold.

10. The coating process for coated aluminum coils based on precise positioning according to any one of claims 1 to 9, characterized in that, The process of baking, curing, and winding the coated aluminum coil includes: After the coated aluminum coil is conveyed to the oven for baking and curing, it is rapidly cooled and stress is eliminated by a tension leveler to complete the winding.

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