System for uniform deposition coating

Abstract

A system for powder coating is provided. The system includes a containment enclosure defining a proximal end and a distal end. The system includes a substrate including a surface to be coated with a powder coating. The substrate moves in a direction from the proximal end to the distal end of the containment enclosure. The system includes a first deposition unit disposed over the surface of the substrate. The first deposition unit is configured to deposit a first layer of the powder coating onto the substrate. The system includes a uniformity correction unit disposed over the surface of the substrate and disposed distally relative to the first deposition unit. The uniformity correction unit is configured to ensure uniformity in thickness and / or area mass loading of the powder coating on the substrate.

Description

SYSTEM FOR UNIFORM DEPOSITION COATINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of a co-pending, commonly assigned U.S. Provisional Patent Application No. 63 / 542,918, which was filed on October 6, 2023. The entire content of the foregoing provisional application is incorporated herein by reference.BACKGROUND

[0002] A variety of batteries are available in the industry for different uses. Lithium- ion (Li-ion) batteries have generally become the predominant type of battery used in portable consumer electronics and electric vehicles. Fabrication of Li-ion batteries involves numerous steps, each of which can affect the quality of the battery itself, as well as the cost involved in manufacturing the battery. A conventional manufacturing process generally includes formation of an electrode slurry having an active material, a conductive additive, and a binder, mixed in an organic solvent, and the electrode slurry is applied to a metal foil material. Once applied to the foil material, the solvent is dried out or evaporated while the active electrode mixture remains attached to the metal foil material surface. In some instances, the solvent may be toxic and can necessitate additional steps for handling / discarding that increase the overall cost of the manufacturing process. The cost of removing the solvent from the coated material on the metal foil therefore involves an additional step that also increases the overall cost of the manufacturing process.

[0003] An alternative manufacturing technique used in the industry is electrostatic deposition (ESD), which is a solvent-free manufacturing process for electrode coating for Li-ion batteries. See, e.g., B. Ludwig et al., Solvent-Free Manufacturing of Electrodes for Lithium-ion Batteries, Sci. Rep. 6, Article No. 23150, doi: 10.1038 / srep23150 (2016); M. Wang et al., The Influence of Polyvinylidene Fluoride (PVDF) Binder Properties on LiNio.33Coo.33Mno.33O2 (NMC) Electrodes Made by a Dry-Powder-Coating Process, J. Electrochem. Soc., Vol. 166, No. 10, A2151 (2019); H. Abe et al., Electrostatic Spray Deposition for Fabrication of Li-ion Batteries, Transactions of JWRI, Vol. 44, No. 2 (2015); and U.S. Patent No. 10,547,044). Rather than relying on a solvent mixture, the ESD process uses a dry powder of the active electrode mixture which is applied to the metal foil material. By removing the solvent from the mixture and the drying step from the manufacturing process, the overall process is simplified and becomes more economical, resulting in a viable alternative for large-scale manufacturing. In particular, the solvent-free electrode coating technology is an attractive alternative to traditional manufacturing since it can significantly reduce energy consumption in the manufacturing process and thus significantly reduces the manufacturing cost of batteries.

[0004] In a conventional continuous dry powder ESD coating system, a web (e.g., a grounded electrically conductive substrate) passes continuously through a coating chamber while the dry powder mixture is fluidized and pneumatically conveyed from a hopper to an electrostatic spray gun. The electrostatic spray gun electrostatically charges the powders using tribo-charging or corona charging and sprays the charged powders onto the web where they are deposited. Uniform coating of the web is important to achieve optimal operational performance of the resulting product. However, achieving high uniformities of mass loading distribution (i.e., powder coating on the web) can be difficult with ESD coating systems or any other dry deposition based coating systems, especially at high throughputs. The lack of uniform coating can be because of, e.g., inconsistencies in the air stream for distribution of the powder over the web, powder dispensing system inconsistencies, insufficient powder charging, combinations thereof, or the like. As such, conventional dry powder coating systems are unable to offer a high degree of controlled uniformity of the powder particles on the web, with uniformities varying at about + / - 5 % to 15% in mass variation. For optimal operation of the resulting product, a more uniform web coating is desired.

[0005] Typically, uniformities of + / -5-15% mass variation are considered the state of the art in dry powder coating applications. For manufacturing of precision coatings such as for Lithium-Ion battery electrodes, mass loading variations of + / -1.5% or better are required. To achieve this uniformity, a system which completes a series of operations is described.SUMMARY

[0006] Embodiments of the present disclosure provide an exemplary system for uniform coating of a continuously moving web using electrostatic deposition coating. The system includes a main powder deposition system that provides a first coating layer to the entire web (or substantially the entire web). The main powder deposition system can include any type of system / structure for depositing powder onto the web, e.g., electrostatic powder coating, dry powder brush coating, vibratory feeders, combinations thereof, or the like. If low areas in the first coating layer mass loadings or thickness are detected relativeto a target or threshold mass loading or thickness, the system includes a secondary deposition system that provides a second coating layer only in specific areas of the web that have the detected low areas (i.e., the second coating layer is not applied to the entire web and is selectively applied to specific areas that require additional coating). If the combined first and second coating layer thickness and / or mass loading is detected to meet the target or threshold mass loading and / or thickness, the web proceeds to a leveling system where the uniformity is further refined as needed. In some embodiments, multiple back-up or secondary deposition systems (e.g., uniformity correction deposition systems) and / or leveling systems can be incorporated into the overall system to continue detection and correction of low areas in the coating layer. A feedback control loop can be used with sensors detecting the thickness and / or mass loading of the coating layer and in communication with a controller configured to operate the secondary or back-up deposition system(s) for selective leveling of the coating. Such back-up or secondary deposition system(s) and / or leveling system(s) allow for a more precise coating thickness and mass loading uniformity to be achieved. In particular, the exemplary system achieves a web coating uniformity having mass variation of about + / - 1.5% or less.

[0007] In accordance with embodiments of the present disclosure, an exemplary system for uniform dry powder deposition coating (e.g., powder coating) of a web is provided. The system includes a containment enclosure defining a proximal end and a distal end. The system includes a substrate including a surface to be coated with a powder coating. The substrate moving in a direction from the proximal end to the distal end of the containment enclosure. The system includes a first deposition unit disposed over the surface of the substrate. The first deposition unit is configured to deposit a first layer of the powder coating onto the substrate. In some embodiments, the system includes a uniformity correction unit (e.g., a leveling unit, a second deposition unit, combinations thereof, or the like) disposed over the surface of the substrate and disposed distally relative to the first deposition unit. The uniformity correction unit is configured to ensure uniformity in thickness and / or area mass loading of the powder coating on the substrate. In some embodiments, the system includes a leveling unit disposed over the surface of the substrate and disposed distally relative to the first deposition unit. The leveling unit is configured to level the first layer of the powder coating on the substrate.

[0008] In some embodiments, the system can include a uniformity detection unit disposed over the surface of the substrate, and disposed distally relative to the firstdeposition unit and disposed proximally relative to the uniformity correction unit. The uniformity detection unit can measure at least one of (i) the thickness or (ii) the area mass loading of the first layer of the powder coating at each area of the substrate. The measured thickness or area mass loading (e.g., mass basis) of the first layer of the powder coating can be transmitted to a controller. The controller can be configured to compare the measured thickness or area mass loading of the first layer of the powder coating to a target thickness or a target area mass loading, respectively, to determine low areas of the powder coating on the substrate.

[0009] In some embodiments, the system can include a uniformity detection unit disposed over the surface of the substrate and configured to detect low areas of insufficient powder coating in the first layer of the powder coating as compared to target values for at least one of thickness or mass loading. The uniformity detection unit or a controller can detect a mass loading distribution of the substrate and can calculate a spatial map with coordinates for each of the detected low areas along the surface of the substrate for additional deposition of the powder coating.

[0010] In some embodiments, the uniformity correction unit can include a second deposition unit disposed over the surface of the substrate. The second deposition unit can be configured to selectively deposit a second layer of a powder coating onto the substrate in detected low areas of the first layer of the powder coating. The second layer of the powder coating is selectively deposited over the first layer of the powder coating. The second deposition unit can be disposed distally relative to the first deposition unit, and the uniformity correction unit can include leveling unit disposed distally relative to the second deposition unit.

[0011] In some embodiments, the system can include a uniformity detection unit disposed distally relative to the second deposition unit and the leveling unit. The uniformity detection unit can measure at least one of (i) thickness or (ii) area mass loading of a combination of the first layer and the second layer of the powder coating at each area of the substrate. A controller can compare the measured thickness or area mass loading of the combination of the first layer and the second layer of the powder coating to a target thickness or a target area mass loading, respectively, to determine if low areas of the powder coating exist on the substrate.

[0012] In some embodiments, the first deposition unit can include at least one ofnozzles, rollers, dispensing tubes, mechanical feeders, electrostatic powder feeders, vibratory feeders, electrostatic spray deposition, electrostatic fluidized bed deposition, combinations thereof, or the like. In some embodiments, the second deposition unit can include at least one of nozzles, rollers, dispensing tubes, mechanical feeders, electrostatic powder feeders, vibratory feeders, electrostatic spray deposition, a gravimetric or volumetric meter basis, vibratory dispersion systems, acoustic dispersion systems, combinations thereof, or the like.

[0013] In some embodiments, the second deposition unit can include modules aligned linearly in a perpendicular orientation relative to the direction of movement of the substrate, the modules capable of being independently actuated to selectively deposit the second layer of the powder coating onto the substrate. In some embodiments, the second deposition unit can include modules disposed in a staggered and offset orientation relative to the direction of movement of the substrate, the modules capable of being independently actuated to selectively deposit the second layer of the powder coating onto the substrate. In some embodiments the second deposition system can be on a gantry motion system to move the deposition process as needed to improve the uniformity. In some embodiments, the system can include an uncoated lane formation unit disposed over the surface of the substrate. In some embodiments, the system can include a surface modification unit disposed over the substrate distally located prior to the first deposition unit and configured to modify the surface of the substrate as to improve the subsequent deposition processes.

[0014] In some embodiments, the uniformity correction unit can include a leveling unit. The leveling unit can be configured to level the first layer of the powder coating on the substrate. In some embodiments, the leveling unit can be a non-contact leveling unit which levels the first layer of the powder coating without direct physical contact with the powder coating.

[0015] In accordance with embodiments of the present disclosure, an exemplary method of powder coating is provided. The method includes moving a substrate from a proximal end to a distal end of a containment enclosure, the substrate including a surface to be coated with a powder coating. The method includes depositing a first layer of the powder coating onto the substrate with a first deposition unit disposed over the surface of the substrate. In some embodiments, the system can include ensuring uniformity in thickness and / or area mass loading of the powder coating on the substrate with a uniformity correction unit disposed over the surface of the substrate. The uniformity correction unitis disposed distally relative to the first deposition unit. In some embodiments, the method can include leveling the first layer of the powder coating on the substrate with a leveling unit disposed over the surface of the substrate. The leveling unit is disposed distally relative to the first deposition unit.

[0016] In some embodiments, the method can include measuring at least one of (i) the thickness or (ii) the area mass loading (and / or a visual attribute such as color or surface patterns) of the first layer of the powder coating at each area of the substrate with a uniformity detection unit disposed between the first deposition unit and the uniformity correction unit. The measured thickness or the area mass loading can be compared to a target thickness or a target area mass loading, respectively, to identify low areas of the powder coating on the substrate. In some embodiments, the uniformity correction unit can include a second deposition unit, and the method can include selectively depositing a second layer of a powder coating onto the substrate in the identified low areas of the first layer of the powder coating with a second deposition unit. The second deposition unit can be disposed between the uniformity detection unit and the leveling unit.

[0017] Any combination and / or permutation of embodiments is envisioned. Other objects and features will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the present disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To assist those of skill in the art in making and using the system for uniform powder deposition coating, reference is made to the accompanying figures, wherein:

[0019] FIG. 1 is a diagrammatic view of an exemplary system for uniform powder deposition coating in accordance with embodiments of the present disclosure.

[0020] FIG. 2 is a diagrammatic front view of a second deposition coating unit of an exemplary system for uniform powder deposition coating in accordance with embodiments of the present disclosure.

[0021] FIG. 3 is a diagrammatic top view of a second deposition coating unit of an exemplary system for uniform powder deposition coating having a staggered configuration in accordance with embodiments of the present disclosure.

[0022] FIG. 4 is a block diagram of an exemplary uniform powder deposition coating environment in accordance with embodiments of the present disclosure.DETAILED DESCRIPTION

[0023] FIG. 1 is a diagrammatic view of an exemplary system for uniform powder deposition coating (hereinafter “system 100”). The system 100 can be used to manufacture a coated substrate usable in, e.g., Li-ion batteries, solid state batteries, or the like. The system 100 can be incorporated into an containment enclosure 101 (e.g., a containment chamber) for deposition of the powder coating onto a substrate or web 102, e.g., a continuously moving substrate or web 102. The web 102 includes a top surface 104 on which the powder coating is applied. The powder coating includes at least a cathode material or an anode material, e.g., for rechargeable lithium batteries, or the like. In some embodiments, the bottom surface 106 of the web 102 can also receive the powder coating either concurrently with the top surface 104 or subsequent to the top surface 104 being coated. Rollers 108, 110 are positioned on opposite proximal and distal ends of the web 102 and suspend the web 102 as it passes through the containment enclosure 101. The rollers 108, 110 rotate in a combined manner to maintain the continuous movement of the web 102 through the containment enclosure 101 in a web direction 112. Although two rollers 108, 110 are illustrated, it should be understood that the system 100 can include a single roller, or multiple rollers.

[0024] The system 100 includes a first deposition unit 114 (e.g., a main or primary powder deposition system) positioned over the web 102 and a second deposition unit 116 (e.g., a secondary powder deposition system) positioned over the web 102, with the second deposition unit 116 disposed upstream of and spaced from the first deposition unit 114. As discussed herein, the combination of the first and second deposition units 114, 116 produce a powder coating on the web 102 with a high uniformity (i.e., a higher uniformity as compared to conventional ESD systems). In some embodiments, the first deposition unit 114 can be any one or combination of the following ESD systems using powder dispersion systems, e.g., nozzles, rollers, dispensing tubes, mechanical feeders, electrostatic powder feeders, vibration feeders, electrostatic spray deposition, combinations thereof, or the like, and in the case of electrostatic powder deposition any one or combination of the following charging mechanisms, e.g., corona discharge (positive or negative), tribo-charging, direct conduction charging, induction charging, dielectric barrier discharges, other non-thermalplasmas, or the like. In some embodiments, the second deposition unit 116 can be any one or combination of the following powder deposition systems using powder dispersion systems, e.g., nozzles, rollers, dispensing tubes, mechanical feeders, electrostatic powder feeders, or the like, or dispersion systems based on a gravimetric or volumetric meter basis, can include one or more vibratory and / or acoustic dispersion systems, and / or any one or combination of the following charging mechanisms, e.g., corona discharge (positive or negative), tribo-charging, direct conduction charging, induction charging, dielectric barrier discharges, other non-thermal plasmas, or the like. In some embodiments, the first and / or second deposition units 114, 116 can include one or more features of those disclosed in International Patent Application No. PCT / US23 / 26276, filed on June 27, 2023; U.S. Provisional Patent Application No. 63 / 430,478, filed on December 6, 2022; and U.S. Provisional Patent Application No. 63 / 449,475, filed on March 2, 2023, each of which is incorporated herein by reference.

[0025] In some embodiments, one or more of the operating parameters can be selected as described herein. Nozzle-based dispersion systems can be in the form of an array of nozzles with individual powder feeding mechanisms or distributed orifices on a distribution channel (e.g., tube, bar, or the like) with a single powder feeding manifold. For nozzlebased dispersion systems, powders can be dispensed into a pneumatic conveying line via a venturi type pick-up adaptor or directly from a fluidizing hopper. The powders can be dispensed continuously into the conveying line using twin mechanical feeders, such as twin-screw augers, vibratory tables, hoppers with valves, conveying belts, or the like, which are gravimetrically or volumetrically controlled to assure a repeatable and accurate mass flow rate of powder. The powders can be conveyed using compressed air in the range of about 20-140 psi which is dry of moisture and free of contaminates. The volumetric flow rate of the conveying air and the mass flow rate of the powder can be balanced to assure the powder stays in suspension during conveying and does not build up in the conveying lines. This is a function of the desired coated layer mass loading. A liner material of suitable selection based on the tribo-electrification series compared to the coating powder can be added to the conveying lines to tribo-charge the powders during conveying.

[0026] Roller-based dispensing and dispersion systems can be utilized by placing a hopper over the roller and continuously rotating the roller. The roller can include indents or voids on the surface to allow powder to fall in and be conveyed during rotation to a coating chamber. A perpendicularly oscillating brush or second roller can be used toremove the powder from the dispensing roller surface indents. In some embodiments, a cylindrical brush can rotate about an axis substantially parallel to the rotating roller on which powder is lodged, and the brush can be arranged to interfere with at least the powder and / or surface features upon which the powder is arranged to dispense the powder from the roller. This assembly forms a powder scattering system. Typically, the dispensing roller does not rotate faster than a 1 m / s tip velocity. In some embodiments, this roller-based dispensing system can be coupled with air to further disperse the powder to be effectively charged and coated (e.g., as is described in International Patent Application No. PCT / US24 / 18424, filed on March 4, 2024, which is incorporated herein by reference in its entirety).

[0027] In some embodiments, deploying acoustics to the powder in-flight can assist with dispersing the powders more uniformly before depositing. In some embodiments, frequencies in the range of about 50-1000 Hz with intensities greater than about 30 dB can be applied to achieve a dispersion response, with the values selected based on the powder particle size and / or morphology. In some embodiments, exposure to acoustic waves can assist with breaking up agglomerates that may have formed in an upstream process. It should be understood that this method of breaking up agglomerates does not require physical, mechanical, solid-to-solid, or otherwise direct contact with the powder being dispensed and may constitute or result in a non-contact dispensing mechanism.

[0028] Powder charging using corona discharges can be achieved by applying a high voltage in the range of about 2-100 kV at currents typically below about 5 mA to a discharge electrode with discharge radiuses less than about 2 mm. A negative corona or positive corona can be utilized by setting the polarity of the potential applied to the discharge electrodes. In some embodiments, negative coronas can be used due to a lower corona onset electric field strength. In some embodiments, a positive corona can be used based on the powder particle chemical composition and morphology. The corona discharge electrodes can be deployed in a strategic manner to optimize particle charging and particle transport in the applied electric field. These charging electrodes can take a variety of forms, such as points, wires, meshes, plates, or any combination thereof. Some configurations are described in International Patent Application No. PCT / US23 / 26276, filed on June 27, 2023, and International Patent Application No. PCT / US24 / 18424, filed on March 4, 2024, both of which are incorporated herein by reference in their entirety.

[0029] Direct conduction charging can be utilized by applying a high voltage to aconductive surface in the range of about 2-100 kV with currents typically below about 5 mA for a single electrode. A high degree of surface contact between the powder particles and the charging surface is typically required to achieve efficient charging.

[0030] Controlling environmental conditions, such as humidity, temperature, pressure, atmospheric gas composition, contaminants, combinations thereof, or the like, can assist with maintaining process control and stability. In some embodiments, the humidity can be maintained to about +1-2% relative humidity at room temperature or better from the target. In some embodiments, a partial pressure of water vapor can be maintained to about +1-2% of a target value of a partial pressure of water vapor. In some embodiments, the temperature can be maintained within about + / -1.5°C or better from the target. In some embodiments, the environment pressure can be maintained to within about + / -0.05 inches of water column from target or better. In some embodiments, atmospheric gas composition can be maintained within about + / -1.5 wt% or target. In some embodiments, contaminates can be maintained to less than about 1000 ppm or better, and can be largely dependent on the final product requirement(s) and less about the process stability.

[0031] The first and second deposition units 114, 116 coat the web 102 with the powder such that the total amount of powder creates a coating having a target thickness (as measured from the surface of the web 102) and / or a target mass loading. In some embodiments, the mass loading on the web 102 can be measured using, e.g., beta particle sensors, X-ray sensors, Terahertz, infra-red, non-contact reflection, diffraction, spectroscopy, optical thickness measurement, acoustic transmission, combinations thereof, or the like. The first deposition unit 114 provides the first layer of coating of the powder on the web 102 intended to cover the entire or substantially entire web 102 with the powder, and the second deposition unit 116 provides coating with powder in specific areas of the web 102 that have detected low areas (relative to the target thickness and / or target mass loading). Therefore, the second deposition unit 116 does not apply powder to the entire web 102, and is selectively applied to specific areas of the web 102 that require additional coating. In some embodiments, the first deposition unit 114 coats about, 85-97% inclusive, 85-96% inclusive, 85-95% inclusive, 85-94% inclusive, 85-93% inclusive, 85-92% inclusive, 85-91% inclusive, 85-90% inclusive, 85-89% inclusive, 85-88% inclusive, 85- 87% inclusive, 85-86 inclusive, 86-97% inclusive, 87-97% inclusive, 88-97% inclusive, 89-97% inclusive, 90-97% inclusive, 91-97% inclusive, 92-97% inclusive, 93-97% inclusive, 94-97% inclusive, 95-97% inclusive, 96-97% inclusive, 85-95% inclusive, 85-90% inclusive, 90-95% inclusive, 90-97% inclusive, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or the like, of the target thickness and / or target mass.

[0032] The percentage of powder coating on the web 102 using the first deposition unit 114 can be accomplished by one type of deposition system, or can be accomplished using combinations of two or more deposition systems discussed herein. The first deposition unit 114 can use one or more sensors 118 to provide feedback to the first deposition unit 114 (and / or a main controller) regarding coating of the web 102 (e.g., a feedback loop). This feedback loop can utilize logic based controls and / or machine learning to optimize the control system’ s capability to produce a coating of high uniformity and quality. In some embodiments, the sensors 118 can include process monitoring tools, such as, e.g., particle spatial distribution using particle inference interferometry, laser sheet imaging (available from, e.g., LaVision of Germany), plasma and space charge distribution (using Langmuir probes, electrometers, or the like), voltage / current monitoring of the power supplies for the charging electrodes, carrier gas / powder static pressure and velocity (available from, e.g., TSI Inc. of USA), or the like.

[0033] The system 100 includes a uniformity detection unit 120 disposed over the web 102. The uniformity detection unit 120 is positioned between the first deposition unit 114 and the second deposition unit 116. After the first powder coating is formed on the web 102 by the first deposition unit 114, the uniformity detection unit 120 measures and analyzes the thickness and / or mass loading of the powder coating on the web 102 relative to a target thickness and / or target mass loading. In particular, the uniformity detection unit 120 measures and analyzes the powder coating on the web 102 to determine if there are low or high areas in the powder coating as compared to a target thickness, and / or to determine if there are lighter or heavier points in the powder coating as compared to a target mass loading. Such detection by the uniformity detection unit 120 can be performed using one or a combination of sensors, e.g., optical (confocal laser, triangulation laser, X-ray, IR, vision, or the like), beta particle, thermal, Terahertz, non-contact reflection, diffraction, spectroscopy, optical thickness measurement, or the like, which are typically mounted on a traversing rail and / or a stationary fixture (e.g., Termo Fischer Scientific Inc. of USA).

[0034] Using these sensors, the uniformity detection unit 120 identifies the variation in thickness and / or mass loading along the web 102 surface, and associates coordinates with the specific detected areas of variation (e.g., using the x and y axes along a spatialmap). The coordinates are used as setpoints to be used by the second deposition unit 116 for correcting any detected variations from the target values. The master controller can correlate and associate time information for reaching each specific setpoint on the web 102 surface, such that the second deposition unit 116 can trigger at the appropriate time and location with the appropriate amount of powder to reach the detected variations at the specific coordinates. The second deposition unit 116 is calibrated so that the conveyance and flight time of the powder is accounted for accurately to assure the deposition feature of the second deposition unit 116 reaches the specific coordinates to precisely correct the detected low area(s) in the powder coating. The calibration procedure can utilize, e.g., empirical data, PID loops, statistical association via machine learning algorithms such as regressions, nearest neighbors, random tree forests, or the like in combination or individually. The master controller can also continuously calibrate during continuous processing to account for changes in process conditions using the same methods described. Based on the coordinates, the second deposition unit 116 can strategically fill in the low thickness and / or mass loading areas detected by the uniformity detection unit 120.

[0035] In operation, if the uniformity detection unit 120 detects low thickness and / or low mass loading of the powder coating in specific areas on the web 102, the system 100 controller can operate the second deposition unit 116 to accurately and precisely coat the web 102 in the identified low areas with a second powder coating layer to achieve as close to the target thickness and / or mass loading as possible. If the uniformity detection unit 120 does not identify any low thickness and / or lower mass loading areas, the system 100 can skip operation of the second deposition unit 116 (such that no additional or supplementary powder is provided by the second deposition unit 1 16) and can proceed to a leveling unit 122 for leveling of the powder coating. If the uniformity detection unit 120 does not identify any low thickness and / or low mass loading areas, but does identify high thickness and / or high mass areas (higher than target thickness and / or mass), the system 100 can skip operation of the second deposition unit 116 (such that no additional or supplementary powder is provided by the second deposition unit 116) and can proceed to a leveling unit 122 for le veling of the powder coating. In such instance, the leveling unit 122 reduces the high areas of powder coating to reach the target thickness and / or mass loading. Thus, the system 100 can operate with the second deposition unit 116 being independently (and optionally controlled) relative to the first deposition unit 114. In some embodiments, the second deposition unit 116 and the leveling unit 122 can be collectively referred to as auniformity unit or a uniformity correction unit, such that either can be used to ensure the uniformity in the thickness of the powder coating layer on the web 102.

[0036] As discussed above, the second deposition unit 116 is configured to selectively and strategically provide powder coating to areas identified by the uniformity detection unit 120 as having low thickness and / or mass loading areas. Based on the numerical value of the variation detected by the uniformity detection unit 120 at each specific location on the web 102, the second deposition unit 116 is controlled to deposit a precise amount of powder to reach the target thickness and / or mass loading at the previously identified low areas. The second deposition unit 116 therefore provides a precise secondary layer of powder coating that is not applied to the entire surface of the web 102, and corrects any deficiencies or low areas previously identified as necessitating additional powder coating.

[0037] The combination of the first, second deposition units, and leveling systems 114, 116 therefore ensures that the target thickness and / or mass of the powder coating is achieved (+ / - 1.5% or better from the target value). As discussed above, the second deposition unit 116 can include similar components or different components (as compared to the first deposition unit 114). In some embodiments, these components can be in the form of an array of deposition modules configured to be individually controlled by the system 100 to provide the required accuracy and resolution of the coating variations. In some embodiments, the array of deposition modules can be in a linear configuration, a staggered configuration, an alternating configuration, or the like. In some embodiments, the configuration of the deposition modules can be selected based on spatial clearances, and can include one or a combination of the deposition module arrays.

[0038] If no low areas are detected by the uniformity detection unit 120 or if the second deposition unit 116 has completed the step of a supplementary powder coating in selected areas to ensure a uniform powder coating on the web 102, the web 102 proceeds to the leveling unit 122. The leveling unit 122 is disposed upstream of the second deposition unit 116. The leveling unit 122 is configured to spread, level or plane the deposited layer(s) of the powder coating to achieve a highly uniform powder layer on the web 102 surface. In some embodiments, the leveling unit 122 can use one or more of, e.g., electromagnetic forces, such as electro-planning, which utilize alternating electromagnetic fields of controllable signal types (frequency, magnitude, and signal profile), non-thermal plasma exposure, mechanical devices (such as precision leveling planes or rollers), acoustic exposure (e.g., acoustic base frequencies), vibratory methods, combinations thereof, or thelike, to achieve the level powder coating.

[0039] In some embodiments, the leveling unit 122 can include ultrasonic actuators for, e.g., vibrating in a direction parallel to a vector defining a plane of the powder layer, vibrating in a direction perpendicular to a vector defining a plane of the powder layer, coupled to a rotating roller, combinations thereof, or the like. In some embodiments, the leveling unit 122 can include doctor blades, e.g., arranged transverse to the web motion direction, arranged transverse to the web motion and vibrating (vibrating transverse to the web motion direction, vibrating into and out of the plane of the web, vibrating in a circular motion, vibrating in a “figure 8” motion, or the like), vibrating in an ultrasonic manner, combinations thereof, or the like. In some embodiments, these leveling methods may be roughly bifurcated into contact methods (where physical contact occurs between the leveling unit and the powder) and non-contact methods (where actuation takes place across an air gap between an amount of powder and a device performing leveling within a leveling unit).

[0040] Different types of leveling units having different operating parameters can be used effectively in the exemplary system. In some embodiments, the leveling unit 122 can be in the form of an electro-planning system, as described in U.S. No. 11,607,846, issued on March 21 , 2023 , which is incorporated herein by reference. The electro-planning system can be an effective non-contact means to level a powder bed to improve the uniformity of the distribution of the powder coated layer. In such embodiments, the leveling unit first charges the powders and then exposes them to an alternating electromagnetic field to move the powders in an oscillation motion to settle plane the powders. When incorporated into an electrostatic powder coating system, the residual charge on the powders from deposition can increase the response rate of the powders to the alternating electric field and can improve the planning efficiency. In some embodiments, voltages can be in the range of about 500 V-50 kV applied at a distance of about 0.5 mm-25 mm from the powder coated layer. If the powder coated layer is of a material that has a charge decay on the order of less than 5 seconds, then a continuous application of an electric field to the deposited layer via an electrode displaced above the coated layer can maintain the original charge of the deposited layer and reduce the charging work required of the electro-planning system.

[0041] In embodiments having a leveling unit in the form of acoustic exposure, the operational settings can be substantially similar to those discussed earlier herein. The acoustic wave generator (also known as a sonotrode) can be placed above or below the webwithin about 0 mm- 200 mm. In some embodiments, the acoustic wave generator can be placed at an angle in reference to the web to achieve specific uniformity corrections. An acoustic wave generator may be considered a non-contact means of leveling.

[0042] The one or more leveling mechanisms used in the leveling unit 122 of the system 100 can be arranged across the web 102 width (e.g., perpendicular to the web direction 112 and linearly disposed relative to the web direction 112), in a staggered array down-web (e.g., offset from each other along the web direction 112), combinations thereof, or the like. In some embodiments, the arrangement of the leveling unit 122 components can be selected based on space constraints over the web 102. In some embodiments, the leveling unit 122 can include one or more features described in, e.g., U.S. Patent Publication No. 2020 / 0144591 and / or U.S. Patent No. 10,547,044, each of which is incorporated herein by reference.

[0043] After the leveling step, the web 102 proceeds to a second uniformity detection unit 124 to measure the thickness and / or mass of the leveled powder coating on the web 102 relative to the target thickness and / or mass. The uniformity detection unit 124 can be substantially similar in structure and operation as the uniformity detection unit 120. The uniformity detection unit 124 ensures that the target thickness and / or mass has been achieved after both the first deposition unit 114 (and the second deposition unit 116, if needed), and the leveling system has been implemented. The uniformity detection unit 124 considers a thickness and / or mass within the target accuracy of the target thickness and / or mass loading as having met the uniformity requirements and goals of the system 100. If the uniformity quality target(s) are achieved, the web 102 proceeds to typical steps of heating, compression, and lamination.

[0044] In some embodiments, if the uniformity quality target(s) are not achieved, the system 100 can include a supplementary deposition unit (not shown) substantially similar in structure and operation to the second deposition unit 116 to further fill in any low points or variations in the powder coating, as well as a supplementary leveling unit substantially similar to the leveling unit 122, and a supplementary uniformity detection unit substantially similar to the uniformity detection unit 124. Iterations of these units can therefore be used multiple times (if permitted by size and / or space constraints), to bring the powder coating thickness into conformance with the target accuracy requirement. In some embodiments, if the uniformity quality target(s) are not achieved, the coated layer of powder can be removed before further processing steps, and the coated layer can be reclaimed for reuse.

[0045] The operation of the system 100 therefore first involves the first deposition unit 114. The sensor(s) 118 of the unit 114 can record, e.g., in-situ / in-flight spatial particle distribution measurements, in-situ plasma and space-charge characteristic measurements, in-line voltage / current of charging power supplied, in-situ carrier gas characteristic measurements (such as static pressure and velocity), combinations thereof, or the like. The uniformity detection unit 102 can measure the thickness and / or mass-loading of the electrostatically deposited layer after the first deposition unit 114. The in-situ spatial particle distribution measurements and thickness / mass basis measurements of the deposited layer can be numerically processed by a controller or processing device to create a crossweb map of the actual mass loading and thickness as a function of the down-web position (i.e., coordinates along the web 102). The location at the web 102 can be determined based on timing to reach the specific location, and the timing is used as the leading value in controlling operation of the second deposition unit 116 for release of additional powder coating.

[0046] A control algorithm can compare the distribution of the deposited layer to target setpoints and identifies the low mass loading and / or thickness locations, and the degree to which the distribution is off from the target values. The control algorithm transmits these process setpoints to the second deposition unit 116 to control the amount of additional powder coating applied to the web 102. The second deposition unit 116 synchronizes with a control system the location of the low areas with the web 102 positioning such that the second deposition unit 116 actuates release of the powder coating at the proper time to accurately deposit powder into the low points or regions. After deposition of additional powder coating, the web 102 travels to a leveling unit 122 which continuously levels the entire deposited layer(s) to achieve the target mass / thickness uniformity distribution. The uniformity detection unit 124 can be used to measure an additional thickness / mass-loading of the leveled coatings to ensure quality control. In some embodiments, the system 100 can include additional second deposition units and leveling units to iteratively fill in any remaining low points in the coating before proceeding to final processing steps of the web 102.

[0047] FIG. 2 provides a diagrammatic front view of one embodiment of an exemplary second deposition unit 200 which can be incorporated into the system 100. The second deposition unit 200 includes an array of modules 202 positioned across the width of the web 102 (e.g., perpendicularly oriented relative to the width direction 112). In someembodiments, the modules 202 can be positioned linearly across the web 102. In some embodiments, the modules 202 can be positioned in a staggered manner across the web 102 with some modules 202 gradually positioned further along the web direction 112. In some embodiments, the modules 202 can be positioned in an alternating manner across the web 102 with their positions alternating along the web direction 112.

[0048] The web 102 includes a first powder coating layer 204 provided by the first deposition unit 114. Although some areas 206 of the coating layer 204 have a thickness and / or mass that meets the target thickness and / or mass the coating layer 204 can include different levels of low locations 208, 210 (e.g., areas), as well as different levels of high locations 212 (e.g., areas). As such, variations in the coating layer 204 can exist, and the second deposition unit 200 is configured to correct such variations to ensure a uniform coating surface.

[0049] The modules 202 are each independently actuated to provide a predetermined amount of powder to the respective low locations 208, 210. Based on the detected thickness and / or mass at the low areas 208, 210, the system 100 can include a correlation for the amount of powder needed to reach the target thickness (and / or mass). As such, the web 102 can be continuously moved and the controller actuates the respective modules 202 such that powder 214, 216 can be applied to the low locations 208, 210 by the appropriate module 202. As illustrated in FIG. 2, the low location 210 receives more powder 216 than the low location 208 (which receives powder 214) to ensure both low locations 208, 210 reach the target thickness and / or mass after passage under the second deposition unit 200. The high point 212 can remain unchanged while passing under the second deposition unit 200, and is reduced when the web 102 passes through the leveling unit 122.

[0050] FIG. 3 provides a diagrammatic top view of one embodiment of an exemplary second deposition unit 300 which can be incorporated into the system 100. The second deposition unit 300 includes an array of modules 302 positioned across the width of the web 102 in a staggered manner. In particular, the modules 302 extend generally in a direction perpendicular to the web direction 112. However, each adjacent module 302 is positioned offset and upstream of the previous module. In some embodiments, the adjacent offset modules 302 can overlap each other by, e.g., 5-30% inclusive, 5-29% inclusive, 5-28% inclusive, 5-27% inclusive, 5-26% inclusive, 5-25% inclusive, 5-24% inclusive, 5-23% inclusive, 5-22% inclusive, 5-21% inclusive, 5-20% inclusive, 5-19% inclusive, 5-18% inclusive, 5-17% inclusive, 5-16% inclusive, 5-15% inclusive, 5-14% inclusive, 5-13% inclusive, 5-12% inclusive, 5-11% inclusive, 5-10% inclusive, 5-9% inclusive, 5-8% inclusive, 5-7% inclusive, 5-6% inclusive, 6-30% inclusive, 7-30% inclusive, 8-30% inclusive, 9-30% inclusive, 10-30% inclusive, 11-30% inclusive, 12-30% inclusive, 13- 30% inclusive, 14-30% inclusive, 15-30% inclusive, 16-30% inclusive, 17-30% inclusive, 18-30% inclusive, 19-30% inclusive, 20-30% inclusive, 21-30% inclusive, 22-30% inclusive, 23-30% inclusive, 24-30% inclusive, 25-30% inclusive, 26-30% inclusive, 27- 30% inclusive, 28-30% inclusive, 29-30% inclusive, 10-25% inclusive, 15-25% inclusive, 5%, 6%, 7%, 8%, 9%, 10%, 11 %, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or the like.

[0051] The modules 302 of the second deposition unit 300 can have the same intended operation as the modules 202 of the second deposition unit 200, i.e., selectively fill low areas of the first layer of powder coating 304 on the web 102 identified by the uniformity detection unit 120. Thus, each module 302 can operate independently (or in a combined manner) to selectively fill low areas on the web 102 based on measurements from the uniformity detection unit 120 and instructions from the control algorithm processing within a controller. In some embodiments, the modules 302 can stagger in an alternating manner, e.g., a back and forth pattern along the web direction 112.

[0052] FIG. 4 is a block diagram of an exemplary system for uniform electrostatic deposition coating environment 400 in accordance with exemplary embodiments of the present disclosure. The environment 400 includes multiple components / units that communicate with each other via a communication platform (serial, I / Os, or the like) or network, e.g., any network over which information can be transmitted between components / units communicatively coupled to the network. For example, the communication network can be the Internet, Intranet, virtual private network (VPN), wide area network (WAN), local area network (LAN), and the like. In some embodiments, the communication network can be part of a cloud environment.

[0053] The environment 400 includes a master control system 402 (e.g., a master controller) that receives and transmits data for control of operation of the units of the system 100. For example, the control system 402 can receive measurement data regarding low locations of the first layer of power coating, including the variation from the target coating values and the position of the low locations. The control system 402 can, in turn, analyze such data to determine the amount of additional powder coating needed at each of the low locations, and transmits instructions with such determination to the second deposition unit.

[0054] As illustrated in FIG. 4, the master control system 402 is communicatively connected to the first deposition unit 404, the uniformity detection unit 406, the leveling unit 408, and the second deposition unit 410. Data can be transmitted between each of the respective units and the control system 402 via the communication platform, e.g., network environment 400. The environment 400 can include one or more sensors 412 incorporated into the first deposition unit 404. The sensors 412 can also be incorporated into any other unit of the system 100, or can be positioned between the units. The sensors 412 can measure data relating to in-flight particle spatial variation 414, uniformity detection for thickness and / or mass basis 416, mass loading map calculation 418 with associated software and / or algorithms, combinations thereof, or the like.

[0055] As discussed above, the loading map for low points detected in the web coating can be based on the detection performed by the uniformity detection unit. In some embodiments, the system 100 can incorporate machine learning to optimize detection of low points in the first powder coating layer. For example, the controller can receive historical data regarding previously detected low points on the web. The historical data can indicate specific areas that have a high probability of having low points of powder coating. The historical data can include the coordinates or setpoints of such low points, and the system 100 can monitor these setpoints based on the higher probability to ensure low points detected accurately.

[0056] While exemplary embodiments have been described herein, it is expressly noted that these embodiments should not be construed as limiting, but rather that additions and modifications to what is expressly described herein also are included within the scope of the invention. Moreover, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations are not made express herein, without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. A system for powder coating, the system comprising: a containment enclosure defining a proximal end and a distal end; a substrate including a surface to be coated with a powder coating, the substrate moving in a direction from the proximal end to the distal end of the containment enclosure; a first deposition unit disposed over the surface of the substrate, wherein the first deposition unit is configured to deposit a first layer of the powder coating onto the substrate; and a uniformity correction unit disposed over the surface of the substrate and disposed distally relative to the first deposition unit, wherein the uniformity correction unit is configured to ensure uniformity in area mass loading and / or thickness of the powder coating on the substrate.

2. The system of claim 1 , comprising a uniformity detection unit disposed over the surface of the substrate, and disposed distally relative to the first deposition unit and disposed proximally relative to the uniformity correction unit.

3. The system of claim 2, wherein the uniformity detection unit measures at least one of (i) the thickness or (ii) the area mass loading of the first layer of the powder coating at each area of the substrate.

4. The system of claim 3, wherein the measured thickness or the area mass loading of the first layer of the powder coating is transmitted to a controller, wherein the controller is configured to compare the measured thickness or area mass loading of the first layer of the powder coating to a target thickness or a target area mass loading, respectively, to determine low areas of the powder coating on the substrate.

5. The system of claim 1, comprising a uniformity detection unit disposed over the surface of the substrate and configured to detect low areas of insufficient powder coating in the first layer of the powder coating as compared to target values for at least one of thickness or mass loading.

6. The system of claim 5, wherein the uniformity detection unit or a controllerdetects a mass loading distribution of the substrate and calculates a spatial map with coordinates for each of the detected low areas along the surface of the substrate for additional deposition of the powder coating.

7. The system of claim 1, wherein the uniformity correction unit comprises a second deposition unit disposed over the surface of the substrate.

8. The system of claim 7, wherein the second deposition unit is configured to selectively deposit a second layer of a powder coating onto the substrate in detected low areas of the first layer of the powder coating.

9. The system of claim 8, wherein the second layer of the powder coating is selectively deposited over the first layer of the powder coating.

10. The system of claim 8, wherein the second deposition unit is disposed distally relative to the first deposition unit, and the uniformity correction unit comprises a leveling unit disposed distally relative to the second deposition unit.

11. The system of claim 8, comprising a uniformity detection unit disposed distally relative to the second deposition unit.

12. The system of claim 11, wherein the uniformity detection unit measures at least one of (i) the thickness or (ii) the area mass loading of a combination of the first layer and the second layer of the powder coating at each area of the substrate.

13. The system of claim 13, wherein a controller compares the measured thickness or area mass loading of the combination of the first layer and the second layer of the powder coating to a target thickness or a target area mass loading, respectively, to determine if low areas of the powder coating exist on the substrate.

14. The system of claim 1, wherein the first deposition unit includes at least one of nozzles, rollers, dispensing tubes, mechanical feeders, or electrostatic powder feeders.

15. The system of claim 8, wherein the second deposition unit includes at least one of nozzles, rollers, dispensing tubes, mechanical feeders, electrostatic powder feeders, a gravimetric or volumetric meter basis, vibratory dispersion systems, oracoustic dispersion systems.

16. The system of claim 8, wherein the second deposition unit includes modules aligned linearly in a perpendicular orientation relative to the direction of movement of the substrate, the modules capable of being independently actuated to selectively deposit the second layer of the powder coating onto the substrate.

17. The system of claim 8, wherein the second deposition unit includes modules disposed in a staggered and offset orientation relative to the direction of movement of the substrate, the modules capable of being independently actuated to selectively deposit the second layer of the powder coating onto the substrate.

18. The system of claim 1, comprising an uncoated lane formation unit disposed over the surface of the substrate.

19. The system of claim 1, comprising a surface modification unit disposed over the substrate distally located prior to the first deposition unit and configured to modify the surface of the substrate as to improve the subsequent deposition processes.

20. The system of claim 1 , wherein the uniformity correction unit comprises a leveling unit, and wherein the leveling unit is configured to level the first layer of the powder coating on the substrate.

21. The system of claim 20, wherein the leveling unit is a non-contact leveling unit which levels the first layer of the powder coating without direct physical contact with the powder coating.

22. A method of powder coating, comprising: moving a substrate from a proximal end to a distal end of a containment enclosure, the substrate including a surface to be coated with a powder coating; depositing a first layer of the powder coating onto the substrate with a first deposition unit disposed over the surface of the substrate; and ensuring uniformity in a thickness and / or area mass loading of the powder coating on the substrate with a uniformity correction unit disposed over the surface of the substrate, wherein the uniformity correction unit is disposed distally relative to the first deposition unit.

23. The method of claim 22, comprising measuring at least one of (i) the thickness or(ii) the area mass loading of the first layer of the powder coating at each area of the substrate with a uniformity detection unit disposed between the first deposition unit and the uniformity correction unit, wherein the measured thickness or the area mass loading is compared to a target thickness or a target area mass loading, respectively, to identify low areas of the powder coating on the substrate.

24. The method of claim 22, wherein the uniformity correction unit comprises a second deposition unit, and the method comprises selectively depositing a second layer of a powder coating onto the substrate in the identified low areas of the first layer of the powder coating with the second deposition unit, wherein the second deposition unit is disposed distally relative to the uniformity detection unit.

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