A coating die flow field simulation analysis method and system
By constructing a flow field simulation analysis method for coating die heads and optimizing coating parameters, the problem of uneven distribution of flow velocity and pressure during the coating process was solved, achieving stability and uniformity of coating quality and reducing optimization costs.
Patent Information
- Application Number
- CN202610796223.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-04
- Publication Date
- 2026-08-25
AI Technical Summary
During the slit extrusion coating process, the slurry flows in from the middle inlet of the die head, causing a difference in flow velocity between the center and the edge of the die cavity. This results in uneven flow velocity and pressure distribution at the die head outlet, leading to instability in the coating flow field, resulting in thickness fluctuations, streaks, and thick edge defects, which affect the coating quality.
By constructing a flow field simulation analysis method for coating die heads, monitoring the pressure difference and radial flow velocity signals at the outlet of the internal cavity of the model, optimizing the geometric parameters of the gasket and lip, adjusting the coating gap, flow rate, substrate velocity and vacuum/edge trimming parameters, constructing a stable process window, and achieving flow field uniformity.
It shortened the optimization cycle and cost input, significantly improved coating uniformity and edge quality, and reduced rectification costs.
Smart Images
Figure CN122634894A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method and system for simulating and analyzing the flow field of a coating die, belonging to the field of simulation technology for coating quality control systems. Background Technology
[0002] Slit extrusion coating is a coating preparation technology that uses a precision slit die to uniformly coat a fluid material onto a substrate surface to a predetermined thickness. This method offers advantages such as controllable thickness, clean boundaries, and environmental friendliness (closed-loop solvent recovery), and has been widely applied in lithium-ion battery electrodes, solid electrolytes, functional films (optical brightening films, separator films), flexible displays, organic photovoltaics, and sensors. To achieve stable coating quality, the system typically needs to operate within a "process window." However, in actual production, the following common problems still exist: During the coating process, because the slurry always flows in from the center inlet of the die, a difference in flow velocity between the center and edge of the die cavity occurs, causing uneven flow velocity and pressure distribution along the width direction at the die outlet, which easily leads to instability in the coating flow field. This manifests as defects such as thickness fluctuations, streaks, and "edge bead," which not only affect edge loss and yield but also induce stress concentration and warping during subsequent drying / calendering. When the slurry delivery system is mismatched with the mold design, pressure fluctuations are prone to occur in the mold head area, which may cause localized abnormal discharge and lateral thickness deviations, manifesting as periodic thickness streaks, intermittent discontinuities, and localized abnormal discharge. This affects the overall coating quality; therefore, suppressing uneven outlet flow rate and the formation of thick edges is crucial. Summary of the Invention
[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for simulating and analyzing the flow field of a coating die. By monitoring the pressure difference at the outlet of the internal cavity of the model and the radial flow velocity signal, it determines whether flow field turbulence and edge accumulation occur during coating. Furthermore, it optimizes the geometric parameters of the gasket and lip, and coordinates the adjustment of coating gap, flow rate, substrate velocity, and vacuum / edge finishing parameters to construct a stable process window. This reduces rectification costs, shortens the optimization cycle, and significantly improves coating uniformity and edge quality.
[0004] To achieve the above objectives / to solve the above technical problems, the present invention is implemented using the following technical solution: First aspect: A method for simulating and analyzing the flow field of a coating die head, the method comprising: A three-dimensional model of the coating quality control system is constructed. The three-dimensional model includes the fluid domain space inside the coating die, the slurry velocity inlet, the slurry pressure outlet, the slurry buffer zone, and the slurry leveling zone structure. The three-dimensional model is imported into fluid simulation software, and the fluid region is extracted through Boolean operations. The extracted fluid domain is then segmented and assigned regions. The simulation software includes a physical environment with steady-state solutions, laminar flow, and fluid volume models, and defines the dynamic viscosity, density, surface tension, and contact angle material properties of the slurry. The actual process parameters are obtained as boundary conditions and input into the simulation model. The slurry inlet is set as the mass flow rate inlet and the slurry outlet is set as the pressure outlet. The boundaries of the remaining slurry buffer zone and slurry leveling zone are set as walls. The fluid region is meshed and calculated to obtain the flow field results; the flow field results are post-processed to obtain the flow field simulation results, which include at least the pressure difference distribution and flow velocity distribution within the slurry cavity; Based on the velocity distribution of the flow field, determine whether the velocity difference between the center and the edge of the fluid domain exceeds a preset threshold. If it does, adjust the coating die structure or process parameters and re-simulate until the uniformity requirement is met.
[0005] In this technical solution, the pressure distribution inside the flow field cavity and the simulation results of the velocity distribution at the center and edge of the flow field are used to determine whether the pressure inside the cavity is uniformly distributed, whether the slurry flow rate is uniform, and whether there is a risk of thick edge defects and spot defects. This replaces the traditional method of optimizing the coating effect through experimental verification, shortens the optimization cycle and reduces the cost investment, thereby achieving cost reduction and efficiency improvement.
[0006] Optionally, the construction of the three-dimensional model of the coating quality control system includes: Create an assembly model of the upper coating die, gasket structure, pressure strip, and lower coating die in 3D modeling software; The fluid domain space is made to be connected to the external environment only through the slurry velocity inlet and the slurry pressure outlet, while the remaining slurry buffer zone and slurry leveling zone are set as closed structures based on wall conditions.
[0007] In this technical solution, by establishing a complete assembly model including the upper coating die, gasket structure, pressure strip, and lower coating die, the actual flow space and confined boundaries of the slurry inside the coating die can be realistically reproduced, making the subsequent simulation results closer to the actual production state. At the same time, by limiting the fluid domain to only be connected to the outside world through the slurry inlet and slurry outlet, and the rest being a closed structure, calculation deviations caused by geometric gaps, non-realistic connected areas, or incorrect boundary settings can be avoided, thereby improving the accuracy and reliability of the flow field simulation model.
[0008] Optionally, the extraction of the fluid region via Boolean operations includes: Using the subtraction method, with the inner cavity structure of the coating die as the tool body, the solid part is subtracted from the cube or cylinder containing the die structure to obtain the fluid domain model of the coating quality control system; or the Boolean operation of the fluid region is directly completed in the 3D modeling software and imported into the simulation software.
[0009] In this technical solution, the actual flowable space of the slurry is extracted from the solid assembly model of the coating die head through Boolean subtraction operation. This can transform the complex solid structure of the die head into a fluid domain model suitable for fluid simulation, avoiding invalid calculations on the solid structure directly. At the same time, this method can accurately preserve key geometric features such as the inlet, buffer chamber, distribution channel, outlet, and gasket flow restriction area, so that the simulation model can reflect the influence of gasket structure, channel shape, and outlet distribution on the slurry flow rate and pressure distribution, thereby improving the efficiency of fluid domain extraction and the consistency of simulation preprocessing.
[0010] Optionally, the meshing of the fluid domain includes: using a polyhedral meshing method dominated by surface quadrilaterals; and performing mesh densification processing on the buffer cavity region of the coating die.
[0011] In this technical solution, a polyhedral mesh generation method with surface quadrilateral master control is adopted, which can take into account both the geometric adaptability and computational stability of complex mold head internal cavity structure and reduce the impact of local distorted mesh on the solution results. At the same time, the mesh is refined in the slurry buffer cavity, near the inlet and in local areas with large flow velocity changes, which can more accurately capture pressure gradient, velocity gradient and local backflow phenomenon, and improve the calculation accuracy of key indicators such as velocity difference and pressure difference between the central region and the edge region.
[0012] Optionally, determining the velocity difference between the center and edge of the fluid domain based on the flow field velocity distribution includes: extracting velocity distribution data at different pressure outlets; If the center velocity of the fluid domain is between 0.16 and 0.17 m / s and the edge velocity is less than 0.15 m / s, then the slurry velocity distribution is considered uneven. If the edge velocity is less than 0.13 m / s, it is determined that the slurry flow rate distribution is uneven, which poses a risk of thick edge defects during the coating process.
[0013] This technical solution extracts velocity distribution data at different pressure outlets and at the center and edge of the fluid domain, transforming coating quality issues from experience-based judgments into quantifiable velocity difference assessments. When the center velocity is significantly greater than the edge velocity, risks of uneven slurry distribution, insufficient edge feeding, or thick edge defects can be identified in advance, allowing potential defects to be discovered before actual trial production. This solution can visually display the flow trend of the slurry in the die cavity, the velocity difference between the center and edge regions, and the distribution status at different outlets, providing data support for gasket structure optimization and process parameter adjustment.
[0014] Optionally, optimizing the three-dimensional geometric model includes: Add auxiliary structures to the gasket structure to regulate fluid flow rate; By adjusting the gasket structure or process parameters, the difference between the center velocity and the edge velocity of the fluid domain can be reduced until the uniformity requirements are met.
[0015] In this technical solution, by adding an auxiliary structure to the gasket structure to adjust the slurry flow rate, the local distribution resistance of the slurry in the die head cavity can be changed, reducing the excessively high flow rate in the central area and improving the uniformity of material supply in the edge area, thereby reducing the difference between the center speed and the edge speed. Simultaneously, by repeatedly adjusting the gasket structure or process parameters through simulation, structural optimization can be completed without multiple machining of physical die heads and repeated machine tests, reducing trial-and-error costs and shortening the development cycle. Figure 6 The auxiliary flow adjustment structure on the gasket structure shown can be used to optimize the flow for problems such as thick edges, insufficient material at the edges, or uneven flow rate.
[0016] Optionally, the step of meshing the fluid region and performing calculations to obtain the flow field results includes: The finite volume method is used to discretize the fluid computational domain, dividing the fluid domain inside the coating die into several control volumes. The continuity equation and momentum equation of the slurry flow are solved on each control volume. For the non-Newtonian properties of the slurry, a non-Newtonian viscosity model is used to describe the relationship between shear rate and viscosity. During the solution process, the velocity field and pressure field are iteratively updated through a pressure-velocity coupling algorithm until the residual, outlet flow rate are balanced or the velocity / pressure monitoring values meet the convergence requirements. Set the corresponding iterative control parameters in the steady-state solver, and set the maximum number of iterations, residual or monitoring quantity convergence criteria in the stopping criteria; when the residual, outlet flow balance or velocity / pressure monitoring value meets the preset conditions, the flow field results are obtained.
[0017] In this technical solution, the finite volume method is used to discretize the fluid computational domain, ensuring the conservation of mass and momentum within each control volume. This results in good physical consistency of the calculated pressure and velocity fields within the coating die cavity. For the non-Newtonian characteristics of the slurry, a non-Newtonian viscosity model is used to describe the relationship between shear rate and viscosity, more realistically reflecting the flow state of the battery slurry in different channels and shear regions. The velocity and pressure fields are updated using a pressure-velocity coupled iterative algorithm, and convergence is determined by combining residuals, outlet flow balance, or velocity / pressure monitoring data, improving the stability and reliability of the solution process. This solution allows simulation calculations to move beyond relying solely on empirical parameters, obtaining quantifiable flow field results based on fluid control equations and iterative solution processes.
[0018] Optionally, setting the slurry inlet as a mass flow inlet includes: Set the slurry inlet to be connected to the external environment, with a relative pressure of zero; The mass flow rate from the actual process parameters is used as the input condition for the inlet.
[0019] In this technical solution, the mass flow rate in the actual production or design process is used as the inlet boundary condition, which enables the simulation model to be consistent with the actual material supply state of the production line, thereby improving the guiding value of the simulation results for the actual coating process. At the same time, setting the inlet relative pressure to zero and the outlet to a pressure outlet can form pressure boundary conditions that conform to the actual material supply and discharge process, which is convenient for analyzing the pressure loss of the slurry in the die cavity, the outlet distribution state, and the flow uniformity between different outlets.
[0020] Optionally, there are multiple slurry pressure outlets, and pressure difference diagrams and velocity distribution diagrams are plotted at each outlet in post-processing to determine the uniformity of slurry distribution.
[0021] In this technical solution, by setting multiple slurry pressure outlets and extracting the pressure and velocity distribution at each outlet, the slurry distribution along the width of the coating die can be evaluated in zones, avoiding the problem of uneven local discharge that is masked by judging solely based on the overall average flow rate. By drawing pressure difference diagrams and velocity distribution diagrams at each outlet, it is possible to intuitively determine whether there are significant pressure differences or velocity differences between the center outlet, edge outlets, and adjacent outlets, thereby identifying coating defects such as streaks, local material shortages, and thick edges in advance, and providing a basis for subsequent adjustments to the gasket structure, inlet flow rate, or outlet structure.
[0022] Second aspect: A flow field simulation and analysis system for a coating die head, the system comprising: The model building module is used to build a three-dimensional model of the coating quality control system. The three-dimensional model includes the fluid domain space inside the coating die, the slurry velocity inlet, the slurry pressure outlet, the slurry buffer area, and the slurry leveling area structure. The extraction module is used to import the three-dimensional model into the fluid simulation software, extract the fluid region through Boolean operations, and divide and allocate the extracted fluid domain. The environment setup module is used to set up a physical environment in the simulation software that includes steady-state solutions, laminar flow and fluid volume models, and to define the dynamic viscosity, density, surface tension and contact angle material properties of the slurry. The data acquisition module is used to obtain actual process parameters as boundary conditions, input them into the simulation model, set the slurry inlet as the mass flow rate inlet, set the slurry outlet as the pressure outlet, and set the boundaries of the remaining slurry buffer zone and slurry leveling zone as the wall surface. The mesh generation module is used to mesh the fluid region and perform calculations to obtain the flow field results; the flow field results are post-processed to obtain the flow field simulation results, which include at least the pressure difference distribution and flow velocity distribution within the slurry cavity; The judgment module is used to determine whether the velocity difference between the center and the edge of the fluid domain exceeds a preset threshold based on the velocity distribution of the flow field. If it does, the coating die head structure or process parameters are adjusted and the simulation is repeated until the uniformity requirement is met.
[0023] In this technical solution, the pressure distribution inside the flow field cavity and the simulation results of the velocity distribution at the center and edge of the flow field are used to determine whether the pressure inside the cavity is uniformly distributed, whether the slurry flow rate is uniform, and whether there is a risk of thick edge defects and spot defects. This replaces the traditional method of optimizing the coating effect through experimental verification, shortens the optimization cycle and reduces the cost investment, thereby achieving cost reduction and efficiency improvement.
[0024] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention uses flow field results to determine whether the flow trend meets expectations, whether there is turbulence or dead zones in the slurry flow, and uses the pressure distribution results inside the flow field cavity and the simulation results of the velocity distribution at the center and edge of the flow field to determine whether the pressure inside the cavity is uniformly distributed, whether the slurry flow velocity is uniform, and whether there is a risk of thick edge defects and spot defects. It replaces the traditional method of optimizing the coating effect through experimental verification, shortens the optimization cycle and reduces the cost investment, and achieves cost reduction and efficiency improvement. Attached Figure Description
[0025] Figure 1 The diagram shown is a schematic representation of the method flow of the present invention. Figure 2 The diagram shown is a schematic diagram of the usage state of the present invention. Figure 3 The diagram shown is a schematic representation of the mesh used for the fluid domain structure division in this invention. Figure 4 The diagram shown is a schematic of the pressure difference inside the coating die cavity of the present invention; Figure 5 The diagram shows the velocity distribution at four different pressure outlets of this invention. Figure 6 The diagram shown is a schematic of the coating head structure of the present invention. Detailed Implementation
[0026] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.
[0027] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.
[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0029] Example 1
[0030] like Figure 1 As shown, a flow field simulation analysis method for a coating die head is disclosed, the method comprising: Step 1: Construct a three-dimensional model of the coating quality control system. The three-dimensional model includes the fluid domain space inside the coating die, the slurry velocity inlet, the slurry pressure outlet, the slurry buffer zone, and the slurry leveling zone structure. Step 2: Import the three-dimensional model into the fluid simulation software, extract the fluid region through Boolean operations, and divide and allocate the extracted fluid domain. Step 3: Set up a physical environment in the simulation software that includes steady-state solution, laminar flow and fluid volume model, and define the dynamic viscosity, density, surface tension and contact angle material properties of the slurry; Step 4: Obtain the actual process parameters as boundary conditions, input them into the simulation model, set the slurry inlet as the mass flow rate inlet, set the slurry outlet as the pressure outlet, and set the boundaries of the remaining slurry buffer zone and slurry leveling zone as the wall. Step 5: Mesh the fluid region and perform calculations to obtain the flow field results; perform post-processing on the flow field results to obtain the flow field simulation results, which include at least the pressure difference distribution and flow velocity distribution within the slurry cavity; Step 6: Based on the flow field velocity distribution, determine whether the velocity difference between the center and edge of the fluid domain exceeds a preset threshold. If it does, adjust the coating die structure or process parameters and re-perform the simulation until the uniformity requirement is met.
[0031] The above embodiments are further elaborated as follows: Step 1: In any 3D modeling software, such as SolidWorks or Catia, establish a 3D model of the coating quality control system. The coating quality control system includes: a fluid domain space within the coating die head cavity; 1. a slurry velocity inlet; 2. a slurry pressure outlet; 3. a slurry buffer zone; and 4. a slurry leveling zone within the coating die head structure. Only the slurry velocity inlet and slurry pressure outlet are connected to the external environment within the fluid domain space. The coating quality control system may have multiple slurry pressure outlets. Figure 2 In this example of the invention, 1 represents the upper coating die, 2 represents the gasket structure, 3 represents the pressure strip, and 4 represents the lower coating die. The three-dimensional model of the coating quality control system is converted into a common format of three-dimensional software, such as Parasolid or Step format. Step 2: Open the STAR-CCM+ software, create a new 3D simulation model, select parallel processing on the local host and enter the number of computation processes, and import the 3D model of the coating quality control system in the general format into the simulation model. Step 3: Geometric model processing. A fluid region model of the coating quality control system is established within STAR-CCM+, encompassing the three-dimensional model of the coating quality control system. Boolean subtraction is used to obtain the fluid region model of the coating quality control system. In the three-dimensional modeling stage, a solid assembly model of the coating die assembly is first established. This assembly includes the upper die, lower die, gasket structure, pressure strip, and other flow-limiting structures. Subsequently, based on the actual flow path of the slurry inside the coating die, an auxiliary entity is established to enclose the flow space, or the inner cavity space of the die is directly selected as the area to be extracted. Using the solid structure of the coating die as the tool, Boolean subtraction is performed on the auxiliary entity to subtract the volume occupied by the solid structures such as the upper die, lower die, gasket, and pressure strip, resulting in a fluid domain model containing only the flowable space of the slurry. The fluid domain model includes the slurry inlet, buffer chamber, distribution chamber, flow channel, outlet, and local flow-limiting areas corresponding to the gasket structure. Next, the fluid domain model is imported into the fluid simulation software, and its region is segmented, its boundaries are named, and its mesh is generated; or the fluid region model of the coating quality control system is obtained directly in the 3D modeling software through Boolean operations and imported into STAR-CCM+; the obtained fluid region 3D model components are segmented according to blocks to segment mass flow inlet, pressure outlet 1, pressure outlet 2, pressure outlet 3, pressure outlet 4, and various wall regions, and the segmented 3D model components are assigned to the region; Step 4: Physical model selection. Create a new physical continuum in the continuum and select physical models such as "3D", "Gas", "Separated Flow", "Steady State", "Laminar Flow", and "Fluid Volume". Step 5: Select material properties. In the material selection, select the material properties of the fluid domain slurry and set the dynamic viscosity, density, surface tension, and contact angle of the slurry, etc. Step 6: Obtain actual / design process parameters. The process parameters are the pressure inside the coating die cavity or the flow rate at the pressure outlet. Usually, the stable average value of the online monitoring flow rate, flow rate or pressure measuring instrument on the equipment is taken. In this invention, mass flow rate is used as the input condition for the fluid domain inlet of the coating die head. Step 7: Input the process parameters as boundary conditions into the simulation model. In the laminar flow physical field, set the mass flow rate inlet of the slurry to an inlet with zero pressure. The inlet with zero pressure means that the slurry inlet is connected to the external environment and the relative pressure is zero. Set the slurry outlet to a pressure outlet and set the rest to wall surfaces. Step 8: Mesh generation. After the mesh is generated, check that there are no problems and proceed to the next step. If an error occurs, you need to modify the erroneous mesh and repair the mesh before proceeding to the next step. Figure 3The meshes used in this invention are all polyhedral meshes controlled by surface quadrilaterals, with appropriate mesh refinement applied to the buffer cavity area of the coating die head. Step 9, Solver settings: In the solver steady state, input the required time steps, and in the stopping criteria, set the simulation stopping criteria, such as stopping time, number of iterations, etc. Step 10: Simulation calculation, run the simulation, and perform post-processing after the calculation is completed. Create a new streamline display. The simulation results of the flow field can show the flow of the slurry in the coating quality control system. The flow field results can be used to preliminarily judge whether the structure is reasonable. Create a scalar scene, select the fluid domain structure for the component, and draw the pressure difference diagram of the slurry fluid domain in the slurry cavity. The pressure difference diagram can be used to judge whether the pressure difference of the slurry center and edge regions meets the requirements. Figure 4 This is a pressure differential diagram within the coating die cavity, including the pressure differential at the slurry inlet, the pressure differential between the center and edge of the fluid domain, and the pressure differential at different slurry outlets. Figure 5 The diagram shows the velocity distribution at four different pressure outlets. Generally, if the difference between the center velocity and the edge velocity of the fluid domain is greater than 0.01 m / s, the slurry velocity distribution is considered uneven. If the difference is greater than 0.03 m / s, thick-edge defects are likely to occur during coating. This can be addressed by adjusting the coating die shim structure or process parameters. Figure 6 As shown, a triangular structure is added to the gasket structure to reduce the central flow velocity and decrease the difference between the central and edge velocities of the fluid domain, thereby achieving the requirement of uniform velocity distribution in the fluid domain. Step 11: Generate a simulation report.
[0032] The above embodiments can be used to optimize design schemes and modify the structure of the coating die pad. By analyzing the flow field results, it can be determined whether the flow trend meets expectations, whether there is turbulence or dead zones in the slurry flow, and by analyzing the pressure distribution within the flow field cavity and the simulation results of the velocity distribution at the center and edges of the flow field, it can be determined whether the internal pressure of the cavity is uniform, whether the slurry flow velocity is uniform, and whether there is a risk of thick-edge defects and spot defects. This approach replaces the traditional method of optimizing coating effects through experimental verification, shortening the optimization cycle and reducing costs, thus achieving cost reduction and efficiency improvement.
[0033] In this embodiment, the construction of the three-dimensional model of the coating quality control system specifically includes: Create an assembly model of the upper coating die, gasket structure, pressure strip, and lower coating die in 3D modeling software; Ensure that the fluid domain space is connected to the external environment only through the slurry velocity inlet and the slurry pressure outlet, and set the remaining slurry buffer area and slurry leveling area as a closed structure based on wall conditions.
[0034] The coating quality control system includes a coating die structure comprising: a fluid domain space within the coating die cavity, a slurry velocity inlet, a slurry pressure outlet, a slurry buffer zone, and a slurry leveling zone. The fluid domain space is only connected to the external environment via the slurry velocity inlet and the slurry pressure outlet. A fluid region model of the coating quality control system is constructed from a three-dimensional model of the coating die cavity through modeling and Boolean operations. Actual or designed process parameters are obtained to build a simulation model, including: inlet slurry velocity / pressure values, fluid material properties, and basic dimensions of the coating die cavity. Based on the constructed simulation model, the flow field, cavity pressure distribution results, and center and edge velocity distribution simulation results of the coating quality control system are obtained. When the differences between the cavity pressure distribution results and the center and edge velocity distribution simulation results and the expected values exceed a set threshold, the three-dimensional model of the coating quality control system or the actual / designed process parameters of the gasket are optimized, and the above steps are repeated. When the optimized simulation model is within the expected range for the cavity pressure distribution results and the center and edge velocity distribution simulation results, it is output as the final result.
[0035] In this embodiment, the extraction of the fluid region through Boolean operations specifically includes: Using a subtraction method, with the internal structure of the coating die as the tool, the solid portion is subtracted from the cube or cylinder containing the die structure to obtain the fluid domain model of the coating quality control system. In the 3D modeling stage, a solid assembly model of the coating die components is first established, including the upper die, lower die, gasket structure, pressure strip, and other flow-limiting structures. Then, based on the actual flow path of the slurry inside the coating die, an auxiliary entity is established to enclose the flow space, or the internal cavity space of the die is directly selected as the region to be extracted. Using the solid structure of the coating die as the tool, a Boolean subtraction operation is performed on the auxiliary entity to subtract the volume occupied by the solid structures such as the upper die, lower die, gasket, and pressure strip, resulting in a fluid domain model containing only the flowable space of the slurry. This fluid domain model includes the slurry inlet, buffer chamber, distribution chamber, flow channel, outlet, and the local flow-limiting region corresponding to the gasket structure. Finally, the fluid domain model is imported into fluid simulation software, and its regions are segmented, boundaries are named, and meshes are generated. Alternatively, Boolean operations on the fluid region can be performed directly in 3D modeling software and then imported into simulation software.
[0036] In this embodiment, the meshing of the fluid domain specifically includes: using a polyhedral meshing method controlled by a surface quadrilateral; and performing mesh densification processing on the buffer cavity region of the coating die.
[0037] In this technical solution, a polyhedral mesh generation method with surface quadrilateral master control is adopted, which can take into account both the geometric adaptability and computational stability of complex mold head internal cavity structure and reduce the impact of local distorted mesh on the solution results. At the same time, the mesh is refined in the slurry buffer cavity, near the inlet and in local areas with large flow velocity changes, which can more accurately capture pressure gradient, velocity gradient and local backflow phenomenon, and improve the calculation accuracy of key indicators such as velocity difference and pressure difference between the central region and the edge region.
[0038] In this embodiment, the specific process of determining the velocity difference between the center and edge of the fluid domain based on the flow field velocity distribution includes: extracting velocity distribution data at different pressure outlets; If the center velocity of the fluid domain is between 0.16 and 0.17 m / s and the edge velocity is less than 0.15 m / s, the slurry velocity distribution is considered uneven. If the edge velocity is less than 0.13 m / s, the slurry velocity distribution is considered uneven, which indicates that thick edge defects are likely to occur during the coating process.
[0039] Generally, if the difference between the center velocity and the edge velocity of the fluid domain is greater than 0.01 m / s, it is considered that the slurry flow velocity distribution is uneven. If the difference is greater than 0.03 m / s, it is considered that thick edge defects are prone to occur during the coating process. This can be addressed by adjusting the structure of the coating die pad or adjusting the process parameters, such as... Figure 6 As shown, a triangular structure is added to the gasket structure to reduce the central flow velocity and decrease the difference between the center velocity and the edge velocity of the fluid domain, thereby achieving the requirement of uniform velocity distribution in the fluid domain.
[0040] In this embodiment, the process of meshing the fluid region and performing calculations to obtain the flow field results includes: The finite volume method is used to discretize the fluid computational domain, dividing the fluid domain inside the coating die into several control volumes. The continuity equation and momentum equation of the slurry flow are solved on each control volume. For the non-Newtonian properties of the slurry, a non-Newtonian viscosity model is used to describe the relationship between shear rate and viscosity. During the solution process, the velocity field and pressure field are iteratively updated through a pressure-velocity coupling algorithm until the residual, outlet flow rate are balanced or the velocity / pressure monitoring values meet the convergence requirements. Set the corresponding iterative control parameters in the steady-state solver, and set the maximum number of iterations, residual or monitoring quantity convergence criteria in the stopping criteria; when the residual, outlet flow balance or velocity / pressure monitoring value meet the preset conditions, the flow field results are obtained; Further explanation: This model uses the Finite Volume Method (FVM) to discretize the fluid computation domain, dividing the fluid domain inside the coating die into several control volumes, and solving the continuity equation and momentum equation of the slurry flow on each control volume.
[0041] For the non-Newtonian characteristics of the slurry, a non-Newtonian viscosity model is used to describe the relationship between shear rate and viscosity. During the solution process, the velocity field and pressure field are iteratively updated through a pressure-velocity coupling algorithm until the residual, outlet flow rate balance, or velocity / pressure monitoring values meet the convergence requirements. The governing equations for incompressible laminar non-Newtonian fluids are solved, with the continuity equation being ∇·u = 0 and the momentum equation being ρ(u·∇)u = -∇p + ∇·[μ(γ̇)(∇u+∇uᵀ)]. The slurry viscosity is modeled using the Carreau-Yasuda non-Newtonian model: μ=μ∞ + (μ0-μ∞)[1+(λγ̇)ᵃ]^((n-1) / a).
[0042] During the solution process, the corresponding iterative control parameters are set in the steady-state solver, and the maximum number of iterations, residual, or monitoring quantity convergence criteria are set in the stopping criteria. When the residual, outlet flow balance, or velocity / pressure monitoring value meets the preset conditions, the flow field results are output. The Maximum Steps are set to 250, and the results are exported through the velocity field, pressure field, XY Plot, and XYZ internal tables for post-processing analysis.
[0043] Post-processing includes: creating a new streamline display; the simulation results of the flow field can reveal the flow of slurry within the coating quality control system, allowing for a preliminary assessment of the structure's rationality; creating a scalar scene; selecting a fluid domain structure for the component; and plotting a pressure differential map of the slurry fluid domain within the slurry cavity. This pressure differential map helps determine if the pressure differential in the slurry center and edge regions meets requirements. The streamline display is used for qualitative observation of the flow path and backflow / retention zone. The scalar scene is used for quantitative display of the velocity field, pressure field, and slurry volume fraction field. XY plots or exported tables are used to extract velocity and pressure data from different outlets or lateral positions. Internal flow field post-processing includes creating a velocity field scalar scene, a pressure field scalar scene, XY plots, planar sections, threshold sections, and an XYZ internal table, and exporting it as Velocity.csv. External flow field post-processing includes isosurfaces, XY plots, and a Volume Fraction of Slurry scalar scene.
[0044] In this embodiment, setting the slurry inlet as a mass flow inlet specifically includes: Set the slurry inlet to be connected to the external environment, with a relative pressure of zero; Use the mass flow rate from the actual process parameters as the input condition for the inlet; The slurry pressure outlets are multiple, and pressure difference diagrams and velocity distribution diagrams are plotted at each outlet during post-processing. The pressure difference diagrams are used to determine whether the pressure difference in the center and edge regions of the slurry meets the requirements.
[0045] In this technical solution, by setting multiple slurry pressure outlets and extracting the pressure and velocity distribution at each outlet, the slurry distribution along the width of the coating die can be evaluated in zones, avoiding the problem of uneven local discharge that is masked by judging solely based on the overall average flow rate. By drawing pressure difference diagrams and velocity distribution diagrams at each outlet, it is possible to intuitively determine whether there are significant pressure differences or velocity differences between the center outlet, edge outlets, and adjacent outlets, thereby identifying coating defects such as streaks, local material shortages, and thick edges in advance, and providing a basis for subsequent adjustments to the gasket structure, inlet flow rate, or outlet structure.
[0046] Example 2
[0047] A flow field simulation and analysis system for coating dies is disclosed, the system comprising: The model building module is used to build a three-dimensional model of the coating quality control system. The three-dimensional model includes the fluid domain space inside the coating die, the slurry velocity inlet, the slurry pressure outlet, the slurry buffer area, and the slurry leveling area structure. The extraction module is used to import the three-dimensional model into the fluid simulation software, extract the fluid region through Boolean operations, and divide and allocate the extracted fluid domain. The environment setup module is used to set up a physical environment in the simulation software that includes steady-state solutions, laminar flow and fluid volume models, and to define the dynamic viscosity, density, surface tension and contact angle material properties of the slurry. The data acquisition module is used to obtain actual process parameters as boundary conditions, input them into the simulation model, set the slurry inlet as the mass flow rate inlet, set the slurry outlet as the pressure outlet, and set the boundaries of the remaining slurry buffer zone and slurry leveling zone as the wall surface. The mesh generation module is used to mesh the fluid region and perform calculations to obtain the flow field results; the flow field results are post-processed to obtain the flow field simulation results, which include at least the pressure difference distribution and flow velocity distribution within the slurry cavity; The judgment module is used to determine whether the velocity difference between the center and the edge of the fluid domain exceeds a preset threshold based on the velocity distribution of the flow field. If it does, the coating die head structure or process parameters are adjusted and the simulation is repeated until the uniformity requirement is met.
[0048] In summary, this invention uses flow field results to determine whether the flow trend meets expectations, whether there is turbulence or dead zones in the slurry flow, and uses simulation results of pressure distribution within the flow field cavity and velocity distribution at the center and edges of the flow field to determine whether the internal pressure of the cavity is uniform, whether the slurry flow velocity is uniform, and whether there is a risk of thick edge defects and spot defects. It replaces the traditional method of optimizing the coating effect through experimental verification, shortens the optimization cycle and reduces costs, thus achieving cost reduction and efficiency improvement.
[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for simulating and analyzing the flow field of a coating die, characterized in that, The method includes: A three-dimensional model of the coating quality control system is constructed. The three-dimensional model includes the fluid domain space inside the coating die, the slurry velocity inlet, the slurry pressure outlet, the slurry buffer zone, and the slurry leveling zone structure. The three-dimensional model is imported into fluid simulation software, and the fluid region is extracted through Boolean operations. The extracted fluid domain is then segmented and assigned regions. The simulation software includes a physical environment with steady-state solutions, laminar flow, and fluid volume models, and defines the dynamic viscosity, density, surface tension, and contact angle material properties of the slurry. The actual process parameters are obtained as boundary conditions and input into the simulation model. The slurry inlet is set as the mass flow rate inlet and the slurry outlet is set as the pressure outlet. The boundaries of the remaining slurry buffer zone and slurry leveling zone are set as walls. The fluid region is meshed and calculated to obtain the flow field results; the flow field results are post-processed to obtain the flow field simulation results, which include at least the pressure difference distribution and flow velocity distribution within the slurry cavity; Based on the flow field velocity distribution, determine whether the velocity difference between the center and edge of the fluid domain exceeds a preset threshold. If it does, adjust the coating die structure or process parameters and re-simulate until the uniformity requirement is met.
2. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, The three-dimensional model for constructing the coating quality control system includes: Create an assembly model of the upper coating die, gasket structure, pressure strip, and lower coating die in 3D modeling software; The fluid domain space is made to be connected to the external environment only through the slurry velocity inlet and the slurry pressure outlet, while the remaining slurry buffer zone and slurry leveling zone are set as closed structures based on wall conditions.
3. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, The extraction of the fluid region via Boolean operations includes: Using the subtraction method, with the inner cavity structure of the coating die as the tool body, the solid part is subtracted from the cube or cylinder containing the die structure to obtain the fluid domain model of the coating quality control system; or the Boolean operation of the fluid region is directly completed in the 3D modeling software and imported into the simulation software.
4. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, The process of meshing the fluid domain includes: using a polyhedral meshing method dominated by surface quadrilaterals; and performing mesh densification processing on the buffer cavity region of the coating die.
5. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, The method of determining the velocity difference between the center and edge of the fluid domain based on the flow field velocity distribution includes: Extract velocity distribution data at different pressure outlets; If the center velocity of the fluid domain is between 0.16 and 0.17 m / s and the edge velocity is less than 0.15 m / s, the slurry velocity distribution is considered uneven. If the edge velocity is less than 0.13 m / s, it is determined that the slurry flow rate distribution is uneven, which poses a risk of thick edge defects during the coating process.
6. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, The optimization of the three-dimensional geometric model includes: Add auxiliary structures to the gasket structure to regulate fluid flow rate; By adjusting the gasket structure or process parameters, the difference between the center velocity and the edge velocity of the fluid domain can be reduced until the uniformity requirements are met.
7. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, The process of meshing the fluid region and performing calculations to obtain the flow field results includes: The finite volume method is used to discretize the fluid computational domain, dividing the fluid domain inside the coating die into several control volumes. The continuity equation and momentum equation of the slurry flow are solved on each control volume. For the non-Newtonian properties of slurry, a non-Newtonian viscosity model is used to describe the relationship between shear rate and viscosity; During the solution process, the velocity field and pressure field are iteratively updated through a pressure-velocity coupling algorithm until the residual, outlet flow balance, or velocity / pressure monitoring quantity meets the convergence requirements. Set the corresponding iteration control parameters in the steady-state solver, and set the maximum number of iterations, residual or monitoring quantity convergence criteria in the stopping criteria; When the residual, outlet flow balance, or velocity / pressure monitoring value meets the preset conditions, the flow field results are obtained.
8. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, Setting the slurry inlet as a mass flow inlet includes: Set the slurry inlet to be connected to the external environment, with a relative pressure of zero; The mass flow rate from the actual process parameters is used as the input condition for the inlet.
9. The flow field simulation analysis method for coating die head according to claim 1, characterized in that, The slurry pressure outlets are multiple, and pressure difference diagrams and velocity distribution diagrams are plotted at each outlet during post-processing to determine the uniformity of slurry distribution.
10. A flow field simulation and analysis system for a coating die, characterized in that, The system includes: The model building module is used to build a three-dimensional model of the coating quality control system. The three-dimensional model includes the fluid domain space inside the coating die, the slurry velocity inlet, the slurry pressure outlet, the slurry buffer area, and the slurry leveling area structure. The extraction module is used to import the three-dimensional model into the fluid simulation software, extract the fluid region through Boolean operations, and divide and allocate the extracted fluid domain. The environment setup module is used to set up a physical environment in the simulation software that includes steady-state solutions, laminar flow and fluid volume models, and to define the dynamic viscosity, density, surface tension and contact angle material properties of the slurry. The data acquisition module is used to obtain actual process parameters as boundary conditions, input them into the simulation model, set the slurry inlet as the mass flow rate inlet, set the slurry outlet as the pressure outlet, and set the boundaries of the remaining slurry buffer zone and slurry leveling zone as the wall surface. The mesh generation module is used to mesh the fluid region and perform calculations to obtain the flow field results; the flow field results are post-processed to obtain the flow field simulation results, which include at least the pressure difference distribution and flow velocity distribution within the slurry cavity; The judgment module is used to determine whether the velocity difference between the center and the edge of the fluid domain exceeds a preset threshold based on the velocity distribution of the flow field. If it does, the coating die head structure or process parameters are adjusted and the simulation is repeated until the uniformity requirement is met.