A method and equipment for stereoscopic visual coating of automotive decorative aluminum panels

Abstract

This invention relates to the field of automotive material processing technology, and more particularly to a method and equipment for three-dimensional visual coating of automotive decorative aluminum panels. The traditional process of "two baking steps"—printing the base color and then separately baking for surface drying, cooling, and then applying the next coating—is optimized into a "one-time baking and curing" process where the wet base color is directly overlaid. This eliminates the intermediate baking and cooling steps, reducing baking energy consumption by approximately 20% and increasing production efficiency by approximately 30%. The non-contact narrow-slit coating avoids physical scratching and disturbance to the wet base color pattern layer. Combined with a simultaneous curing process, the resulting finished product surface is free of defects such as pinholes, craters, and bubbles, increasing the product yield from 65% in the traditional process to over 85%. Through the difference in base color in different areas and the combination of overlay coatings, a three-dimensional visual effect is achieved after a single curing, presenting a transition between light and dark areas and a sense of spatial depth, which is impossible to achieve with traditional planar printing.

Description

Technical Field

[0001] This invention relates to the field of automotive material processing technology, and in particular to a method and equipment for three-dimensional visual coating of automotive decorative aluminum panels. Background Technology

[0002] With the upgrading of automobile consumption, users have increasingly higher requirements for the appearance quality of decorative parts. Automotive decorative aluminum panels not only need to have good weather resistance and scratch resistance, but also need to present rich visual layers and a high-end texture. Currently, the industry typically uses a process combining screen printing and slot-die coating to achieve aluminum panel surface decoration, namely: screen printing the base color on the aluminum panel → baking for surface drying → cooling → slot-die coating → baking and curing again.

[0003] However, the aforementioned existing processes have the following technical drawbacks:

[0004] Firstly, after the base color is printed, it needs to be baked and cooled separately. Then, after coating and layering, it needs to be cured and baked again. The whole process involves two baking processes, which consumes a lot of energy. In addition, the intermediate cooling process takes a long time, which seriously restricts the overall efficiency of the production line and cannot meet the requirements of the automotive industry for cycle time and cost in large-scale production.

[0005] Secondly, the base color ink is baked and dried before being applied in a narrow slit. The two layers only form a physical bond, lacking chemical bonding and interpenetration between the molecular chains, resulting in insufficient interlayer adhesion and a high risk of delamination and peeling during use. Simultaneously, the base color layer easily attracts dust during drying and cooling, or is scratched during transport, leading to a high rate of appearance defects such as pinholes, shrinkage cavities, and particles in the final product. The yield rate of products using traditional processes is only about 65%, resulting in serious resource waste.

[0006] Third, existing processes can only achieve uniform monochrome or simple planar pattern coating, and cannot form differentiated color, brightness and texture distribution in different areas of the aluminum plate surface, nor can they actively construct light and shadow changes and spatial transition effects. The product's appearance is not expressive enough and it is difficult to meet the decorative needs of high-end cars for three-dimensional visual effects.

[0007] To address the aforementioned issues, those skilled in the art have attempted to improve the appearance by increasing the number of coating layers or introducing complex post-processing steps, but these efforts have all resulted in increased process complexity, higher costs, and further reduced yield. To date, the industry lacks a comprehensive solution that can simultaneously achieve high efficiency, energy saving, high adhesion, high appearance yield, and a three-dimensional visual effect within a single production process. Summary of the Invention

[0008] In view of the above problems, this application provides a method and equipment for stereoscopic visual coating of automotive decorative aluminum panels to solve the technical problems involved in the background art.

[0009] To achieve the above objectives, in a first aspect, this application provides a method for applying a three-dimensional visual coating to automotive decorative aluminum panels, comprising the following steps:

[0010] Step 1: Print different colors or different brightness levels of base ink on different areas of the aluminum substrate surface to form a wet base pattern layer with regional visual differences.

[0011] Step 2: The wet base color pattern layer is conveyed to the narrow slit coating station without baking or surface drying, and the base color ink is kept in an uncured wet state during this process;

[0012] Step 3: Using a non-contact narrow-slit coating method, apply an overlay coating or protective coating on top of the wet base color pattern layer. During the coating process, the coating die head and the wet base color pattern layer remain in no physical contact.

[0013] Step 4: The coated aluminum plate is sent into a baking equipment for one-time heating and curing, so that the wet base color pattern layer and the overcoated coating or protective coating are cross-linked and cured at the same time to form an integrated layered structure.

[0014] Unlike existing technologies, the technical solution of this application optimizes the traditional "two-baking" process, which requires separate baking for surface drying and cooling before coating after base color printing, into a "one-baking and curing" process where the wet base color is directly overlaid. This eliminates the intermediate baking and cooling steps, reducing baking energy consumption by approximately 20% and increasing production efficiency by approximately 30%. During the simultaneous curing process of the wet base color ink and the overlay coating, molecular chains interpenetrate between the two layers, forming a strong, integrated bond. This significantly enhances coating adhesion and eliminates the risk of delamination caused by interlayer interface contamination or mismatched curing levels, as in traditional processes. Non-contact narrow-slit coating avoids physical scratching and disturbance to the wet base color pattern layer. Combined with the simultaneous curing process, the resulting finished product surface is free of defects such as pinholes, pores, and bubbles, increasing product yield from 65% in traditional processes to over 85%. Through the differences in base color in different areas and the combination of the overlay coating, a three-dimensional visual effect, impossible to achieve with traditional planar printing, is achieved after a single curing process, presenting a transition between light and dark areas and a sense of spatial depth.

[0015] In one embodiment of the present invention, in step one, the colors, brightness or brushed textures of the different regions are different, and the regional visual differences are formed by the color interlacing and light-dark transitions between the regions.

[0016] In one embodiment of the present invention, in step two, the conveying process is carried out in a closed dust-free channel, the temperature inside the channel is controlled at 23±2℃ and the relative humidity is 50±5%RH, and the conveying speed is synchronized with the speed of screen printing and narrow slit coating, the conveying speed being 0.5m / min~5m / min.

[0017] In one embodiment of the present invention, in step three, the non-contact narrow slit coating method uses a narrow slit coating machine, and the non-contact gap between the coating die head of the narrow slit coating machine and the surface of the aluminum substrate is 50μm~150μm, and the coating thickness deviation is controlled within ±1μm.

[0018] In one embodiment of the present invention, the non-contact narrow slit coating method is carried out in an airtight protective cavity, which is equipped with a positive pressure dust-free purification system to achieve an environmental cleanliness level of Class 10000.

[0019] In one embodiment of the present invention, the coating liquid used in the narrow-slit coating machine is supplied by a high-precision metering pump and is equipped with a solvent compensation device to adjust the viscosity of the coating liquid in real time to match the solvent system of the base color ink.

[0020] In one embodiment of the present invention, in step four, the baking equipment is a segmented hot air circulating oven, which is divided into a preheating section and a curing section along the aluminum plate conveying direction. The temperature of the preheating section is 120℃~150℃ and the processing time is 3min~5min. The temperature of the curing section is 160℃ and the processing time is 15min~20min.

[0021] In one embodiment of the present invention, in step two, the conveyor belt for conveying the aluminum plate substrate is made of antistatic, low-adsorption silicone material, and the surface roughness Ra of the conveyor belt is ≤0.8μm.

[0022] As one embodiment of the present invention, the screen printing speed, wet conveying speed, narrow slit coating speed, and baking temperature are all controlled in a closed loop by a central PLC control system throughout the entire process.

[0023] To achieve the above objectives, in a second aspect, this application provides a stereoscopic visual coating equipment for automotive decorative aluminum panels, comprising a feeding unit, a screen printing unit, a wet conveying unit, a narrow-slit coating unit, and a baking and curing unit arranged sequentially along the aluminum panel conveying direction;

[0024] The screen printing unit is located at the discharge end of the feeding unit and is used to print different colors or different brightness of base color inks on different areas of the aluminum plate substrate surface to form a wet base color pattern layer with regional visual differences.

[0025] The wet conveying unit is connected between the discharge end of the screen printing unit and the feed end of the narrow-slit coating unit. The wet conveying unit has a closed dust-free conveying channel for directly conveying the aluminum plate with the wet base color pattern layer to the narrow-slit coating unit without baking or surface drying, and keeping the base color ink in an uncured wet state during the process.

[0026] The narrow-slit coating unit has a non-contact narrow-slit coating die head, and the non-contact narrow-slit coating die head and the aluminum plate surface are provided with a coating gap without physical contact, which is used to apply an overlay coating or protective coating on the wet base color pattern layer.

[0027] The baking and curing unit is located at the discharge end of the narrow-slit coating unit. The baking and curing unit has a heating chamber for heating and curing the coated aluminum plate in one go, so that the wet base color pattern layer and the overcoated coating or protective coating are cross-linked and cured at the same time to form an integrated layered structure.

[0028] Unlike existing technologies, the technical solution of this application integrates the feeding, screen printing, wet conveying, narrow-slit coating, and baking / curing units sequentially along the conveying direction into a complete production line. Each unit has a clearly defined function and is tightly integrated, realizing the industrialization of a combined process of wet-to-wet screen printing, narrow-slit coating, and single-stage baking / curing. It eliminates the need for a separate intermediate baking oven and cooling section found in traditional processes, significantly reducing the overall length of the equipment and saving workshop space. This equipment can be upgraded from existing screen printing production lines by adding a narrow-slit coating unit and a wet conveying channel, without requiring the reconstruction of the entire production line, thus possessing significant industrial application value. The synergistic effect of the structural design and functional limitations of each unit enables the equipment to stably produce automotive decorative aluminum panels with a three-dimensional visual effect and excellent coating quality, maintaining a product yield consistently above 85%, combining aesthetics and practicality.

[0029] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of this application. Attached Figure Description

[0030] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of this application and other related content, and should not be considered as limitations on this application.

[0031] In the accompanying drawings of the instruction manual:

[0032] Figure 1This is a flowchart illustrating the steps of a stereoscopic visual coating method for automotive decorative aluminum panels according to an embodiment of this application.

[0033] Figure 2 This is a module block diagram of a stereoscopic visual coating device for automotive decorative aluminum panels according to an embodiment of this application;

[0034] The reference numerals used in the above figures are explained as follows:

[0035] 1. Feeding unit; 2. Screen printing unit; 3. Wet conveying unit; 4. Narrow slot coating unit; 5. Baking and curing unit. Detailed Implementation

[0036] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0037] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0038] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0039] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, X and / or Y means: X exists, Y exists, and X and Y exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0040] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0041] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0042] In this application, expressions such as "greater than", "less than", and "exceeding" are understood to exclude the stated number; expressions such as "above", "below", and "within" are understood to include the stated number. Furthermore, in the description of the embodiments of this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times", unless otherwise explicitly specified.

[0043] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0044] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0045] like Figure 1 As shown, this embodiment provides a method for applying a three-dimensional visual coating to automotive decorative aluminum panels, including the following steps:

[0046] Step 1: Print different colors or different brightness levels of base ink on different areas of the aluminum substrate surface to form a wet base pattern layer with regional visual differences.

[0047] In this embodiment, the aluminum substrate is selected from aluminum alloy sheets with a thickness of 0.5mm to 2.0mm (the material can be common grades such as 5052 and 6061). It undergoes pretreatment processes such as degreasing, washing, and passivation to ensure that the surface of the aluminum substrate is clean and has a certain surface roughness to facilitate coating adhesion.

[0048] Here, "different areas" refers to at least two independent spatial areas pre-divided on the surface of the aluminum substrate according to the visual design requirements of the product's decorative pattern. For example, for a car steering wheel emblem, the central pattern of the emblem can be divided into the first area, the outer border into the second area, and the background into the third area; for decorative strips, they can be divided into multiple gradient areas along the length or into three strip-shaped areas (inner, middle, and outer) along the width. The method of dividing the areas, their shape, and their area depend entirely on the design requirements of the target decorative effect and are not specifically limited.

[0049] The base color inks vary in color (hue) or lightness (brightness / grayscale). For example:

[0050] Different shades of the same color: dark gray and light gray, dark red and bright red;

[0051] Different hues: red and blue areas, gold and silver areas;

[0052] Different visual effects: solid color areas and metallic gloss areas, matte areas and highlight areas.

[0053] The differences in ink types are not only reflected in the pigment composition (such as ordinary color paste pigments, metallic aluminum powder pigments, pearlescent pigments, etc.), but also in the resin matrix (such as thermosetting acrylic resin systems, polyester resin systems, etc.), as long as it can form a film under the subsequent curing conditions. The initial viscosity range of the base color ink is preferably 500 mPa·s to 3000 mPa·s (measured at 25°C), and the solid content is preferably 30 wt% to 60 wt% to ensure good ink penetration and leveling during screen printing, and to maintain a stable wet fluid state after printing.

[0054] The wet state refers to the state where the organic solvent or diluent inside the base color ink has not fully evaporated after printing, the resin components have not yet undergone cross-linking and curing reactions, and the ink as a whole presents a fluid / semi-fluid state that can flow or deform. When you lightly touch the protective film with your finger (without direct contact) or observe it through optical means, you can see that the ink surface still has a wet gloss and no surface drying or skinning phenomenon.

[0055] This regional visual difference forms the structural basis for achieving a three-dimensional visual effect. After applying overlay coatings to narrow seams, the background colors of different areas exhibit varying transmission, reflection, and interference effects due to the inherent color / brightness differences in the background layers. This results in a final product displaying alternating light and shadow, and dynamic visual layers. For example, a transparent overlay coating over a dark background area creates a sense of depth and weight, while a transparent overlay coating over a light / bright background area creates a sense of transparency and shimmer. The continuous overlay coating at the boundary between the two areas creates a natural gradient of light and shadow—an effect impossible to achieve with flat, monochrome painting.

[0056] Step 2: The wet base color pattern layer is transported to the narrow-slit coating station without baking or surface drying, and the base color ink is kept in an uncured wet state during this process;

[0057] In this embodiment, "no baking or surface drying" means that during the entire time interval from the completion of screen printing to the start of slot coating, no form of heat treatment (including but not limited to hot air baking, infrared radiation heating, ultraviolet light irradiation, etc.) is actively applied to the wet base color pattern layer, nor is the surface solvent evaporated to a surface-dry state through natural placement, forced ventilation, or other methods. In short, this step mandates that the base color pattern layer directly enter the slot coating process after printing, without any form of drying or curing treatment interspersed. This limitation is specifically reflected in the process sequence as follows: there is no baking section, no cooling section, and no buffer storage area between the output end of the screen printing unit and the input end of the wet conveying unit; the aluminum plate is immediately picked up by the conveyor belt and moved to the slot coating unit after leaving the printing table.

[0058] In actual production, the wet base coat during transportation can be non-destructively tested using an online infrared moisture meter or optical reflectometer. When the surface reflectance of the coating remains stable within a specified range and no curing characteristic peaks appear, it indicates that the coating is still in an uncured wet state. For those skilled in the art, a simple visual judgment can also be made: the wet coating surface has a moist glossy appearance; if a lint-free cotton swab is lightly touched on the coating surface (outside the visible area), colored ink will adhere to the swab, proving that the ink remains wet and uncured.

[0059] This step is one of the core features that distinguishes it from traditional processes. Traditional processes require a baking and surface drying step after printing because subsequent coating methods (such as roller coating or blade coating) are typically used, and if the base coat is wet, it will be damaged during the coating process. However, this embodiment uses a non-contact narrow-slit coating method, where the coating die has no physical contact with the base coat layer. This allows the base coat layer to remain wet, eliminating the intermediate baking step and creating the necessary conditions for subsequent synchronous curing to achieve interlayer molecular chain penetration.

[0060] Step 3: Using a non-contact narrow-slit coating method, apply an overlay coating or protective coating on top of the wet base color pattern layer. During the coating process, the coating die head and the wet base color pattern layer remain in no physical contact.

[0061] In this embodiment, the non-contact slit coating method specifically involves the coating liquid being extruded from the slit-shaped die outlet to form a continuous liquid film. Under conditions where there is no contact between the coating die and the substrate, the liquid film is transferred to the substrate surface through a preset coating gap. Its core features are: a controllable physical gap (50μm~150μm) exists between the coating die and the aluminum substrate surface, which is larger than the thickness of the wet base color pattern layer (5μm~20μm), thus ensuring complete non-contact between the die and the base color layer; the transfer of the coating liquid relies entirely on the gravity of the liquid film and the fluid spreading force, rather than on mechanical contact; and the coating accuracy does not depend on physical contact leveling of the substrate surface, but is achieved through precise control of the die gap, the feed flow rate, and the substrate movement speed.

[0062] It should be noted that the gap range of 50μm to 150μm is determined based on the following considerations: if the gap is less than 50μm, the safety clearance is insufficient, and the thickness tolerance of the aluminum plate itself and conveying vibration may cause the die head to accidentally contact the wet film; if the gap is greater than 150μm, the free fall of the liquid film from the die head outlet to the aluminum plate surface is too large, and the liquid film may experience uneven phenomena such as edge shrinkage, droplet splashing, or coating streaks during the fall, and the uniformity of the coating width edge is difficult to control. The coating thickness deviation of ±1μm is achieved through the coordinated control of a high-precision metering pump (flow accuracy ±0.1%) and a die head fine-tuning mechanism. This precision ensures that the thickness of the overprinted coating is consistent across the entire plate surface, avoiding local color differences or concentrated curing shrinkage stress caused by uneven thickness.

[0063] In actual production, multiple layers of coating can be applied sequentially on the wet base color pattern layer according to product design requirements (such as applying an overlay coating first, and then applying a protective coating). All layers are applied using a non-contact narrow-slit coating method, and each layer is kept in a wet-to-wet state until they are finally cured synchronously.

[0064] Step 4: The coated aluminum plate is sent into the baking equipment for one-time heating and curing, so that the wet base color pattern layer and the overcoated coating or protective coating cross-link and cure at the same time to form an integrated layered structure.

[0065] In this embodiment, one-time heat curing means that after the overcoating is completed, the aluminum plate carrying the double-layer wet film (wet base color pattern layer + wet overcoating / protective layer) completes the curing and cross-linking of all coatings in only one baking process (i.e., through the same heating stroke of the same baking equipment), without any cooling, secondary coating, or secondary baking steps in between. Simultaneous cross-linking curing means that during the same heating process, the resin components in the wet base color pattern layer and the overcoating layer (or protective layer) undergo a simultaneous chemical cross-linking reaction driven by temperature. The integrated layered structure means that after curing, the originally independent bottom layer (base color pattern layer) and top layer (overcoating / protective layer) form a transition region at the interface where molecular chains permeate and are chemically bonded. There is no longer a clearly distinguishable physical interface separation between the two layers, but rather a continuous cross-linked network structure with a concentration gradient. The formation mechanism of this integrated structure is as follows: During the heating and curing process, as the temperature rises and the solvent evaporates, the resin molecular chains at the interface of the two wet films diffuse into each other's regions due to the intensified thermal motion; after the temperature continues to rise to the curing temperature, the cross-linking reaction of the two layers is triggered simultaneously, and the molecular chains that have diffused into the interface region participate in the cross-linking reaction, firmly connecting the bottom layer and the top layer through chemical bonds (such as covalent bonds, hydrogen bonds, etc.), rather than relying solely on van der Waals forces for physical bonding.

[0066] Unlike existing technologies, the technical solution of this application optimizes the traditional "two-baking" process, which requires separate baking for surface drying and cooling before coating after base color printing, into a "one-baking and curing" process where the wet base color is directly overlaid. This eliminates the intermediate baking and cooling steps, reducing baking energy consumption by approximately 20% and increasing production efficiency by approximately 30%. During the simultaneous curing process of the wet base color ink and the overlay coating, molecular chains interpenetrate between the two layers, forming a strong, integrated bond. This significantly enhances coating adhesion and eliminates the risk of delamination caused by interlayer interface contamination or mismatched curing levels, as in traditional processes. Non-contact narrow-slit coating avoids physical scratching and disturbance to the wet base color pattern layer. Combined with the simultaneous curing process, the resulting finished product surface is free of defects such as pinholes, pores, and bubbles, increasing product yield from 65% in traditional processes to over 85%. Through the differences in base color in different areas and the combination of the overlay coating, a three-dimensional visual effect, impossible to achieve with traditional planar printing, is achieved after a single curing process, presenting a transition between light and dark areas and a sense of spatial depth.

[0067] As one implementation method of this embodiment, in step one, the colors, brightness or brushed textures of different areas are different, and regional visual differences are formed by the color interlacing and light-dark transition between different areas.

[0068] In this embodiment, the colors are different: this refers to using inks of different hues in different areas, such as red and blue areas, gold and silver areas, warm and cool areas, etc. Color difference is the most intuitive way to distinguish areas, creating visual impact through hue contrast. The brightness is also different: this refers to using inks of the same color family but with different brightness in different areas, such as dark gray and light gray areas, dark red and bright red areas, dark green and emerald green areas, etc. Differences in brightness do not change the hue, but create a sense of light and shadow through variations in brightness, resulting in a softer and more natural visual effect. Finally, the brushed texture is different: this refers to using brushed texture patterns of different directions, densities, or thicknesses in different areas. Differences in brushed texture can be achieved through the pattern design of the screen printing plate itself (i.e., the imitation brushed texture formed by the printing ink), or through a pre-treatment of the aluminum substrate surface with partitioned mechanical brushing before screen printing (i.e., physical brushing followed by printing and coloring). Different texture directions (e.g., the first area has horizontal brushed texture, and the second area has vertical brushed texture) or different densities (e.g., the first area has fine brushed texture, and the second area has coarse brushed texture) produce different reflection and scattering effects under light, further enhancing the visual distinction between areas.

[0069] Color alternation refers to the alternating arrangement of colors in different areas in space, creating visual rhythm and cadence. For example, along the length of a decorative strip, colors can be arranged alternately in a pattern of "dark color—light color—dark color—light color";

[0070] Light and dark transitions refer to a natural, continuous gradient formed by the layering of color overlays, rather than abrupt changes in color or brightness between adjacent areas. Specifically, when a transparent or semi-transparent overlay is evenly applied over a base color of varying brightness, the overlay exhibits different optical effects in the light and dark areas due to the inherent differences in brightness of the base color. At the boundary, the superposition of light transmission and reflection creates a natural gradient band, achieving a smooth light and dark transition without the need for additional gradient printing.

[0071] As described above, by setting different colors, brightness, or brushed textures in different areas of the aluminum plate surface, a clear visual distinction and contrast is formed between the areas. Then, by orderly superimposing and overlapping multi-colored coatings, the effect of light and shadow transition and light and shadow changes is actively constructed, so that the planar coating structure presents an almost three-dimensional sense of spatial depth, significantly improving the three-dimensionality, layering and visual expressiveness of the product appearance.

[0072] As one implementation method of this embodiment, in step two, the conveying process is carried out in a closed dust-free channel, the temperature in the channel is controlled at 23±2℃ and the relative humidity is 50±5%RH, and the conveying speed is synchronized with the speed of screen printing and narrow slit coating, with a conveying speed of 0.5m / min~5m / min.

[0073] In this embodiment, the sealed dust-free channel refers to a fully enclosed conveying channel connecting the output end of the screen printing unit and the inlet end of the slot coating unit. The channel shell is made of stainless steel or other smooth, airtight materials, and sealing strips are provided at each connection point. Air curtains or baffles are provided at the inlet and outlet to isolate the internal space of the channel from the external workshop environment. This structure prevents external dust, lint, and other contaminants from entering the channel and contacting the wet coating, while also preventing external airflow disturbances from affecting the stability of the ink solvent evaporation rate.

[0074] The temperature inside the channel is controlled at 23±2℃ (i.e., 21℃~25℃), and the relative humidity is controlled at 50±5%RH (i.e., 45%~55%RH). The determination of this temperature and humidity range is based on the following: 23℃ is the optimal temperature for maintaining the rheological properties of this type of solvent-based ink; if the temperature is too high, solvent evaporation accelerates, and if the temperature is too low, the ink viscosity increases and the fluidity decreases; 50%RH is the optimal solvent evaporation equilibrium humidity for this type of ink system; if the humidity is too low, the solvent evaporates too quickly and easily dries out, while if the humidity is too high, the solvent evaporates too slowly and moisture may mix into the ink system, affecting curing; ±2℃ and ±5%RH are the standard control precisions for industrial constant temperature and humidity equipment, and are technically and economically achievable.

[0075] The conveying speed ranges from 0.5 m / min to 5 m / min, and is synchronized with the screen printing speed and the narrow-slit coating speed. The lower limit of 0.5 m / min ensures that production efficiency is not too low, while the upper limit of 5 m / min ensures that the wet ink has sufficient residence time during conveying and sufficient leveling time under the coating die. Speed ​​synchronization is achieved through a central PLC control system, ensuring that no workpiece accumulation or pulling occurs between units.

[0076] As described above, the sealed, dust-free channel, combined with a constant temperature and humidity environment of 23±2℃ and 50±5%RH, ensures a stable solvent evaporation rate for the wet base color ink during transport, preventing surface drying defects such as pinholes, craters, and other appearance defects caused by temperature and humidity fluctuations. The sealed structure effectively isolates external dust, preventing dust adsorption on the wet coating surface and causing particulate defects. The conveying speed is synchronized with the screen printing and narrow-slit coating speeds within the range of 0.5~5m / min, enabling continuous production line operation and avoiding workpiece accumulation, transport interruptions, or uneven coating thickness caused by speed mismatch.

[0077] As one implementation method of this embodiment, in step three, the non-contact narrow slit coating method uses a narrow slit coating machine. The non-contact gap between the coating die head of the narrow slit coating machine and the surface of the aluminum substrate is 50μm~150μm, and the coating thickness deviation is controlled within ±1μm.

[0078] In this embodiment, the non-contact gap refers to the vertical distance between the lower end face of the coating die and the upper surface of the aluminum substrate (i.e., the surface of the aluminum plate below the wet base color pattern layer, with the aluminum plate as the measurement reference). Since the thickness of the wet base color pattern layer is typically 5μm to 20μm, the actual net clearance between the lower end face of the die and the surface of the wet film is 30μm to 145μm, ensuring that the die and the wet film do not have physical contact under any operating conditions. The determination of this gap range is based on the following: Below 50μm, due to the thickness tolerance of the aluminum plate itself (typically ±0.02mm) and mechanical vibration during transport (amplitude typically less than 10μm), there is a risk of accidental contact between the die and the aluminum plate or wet film. Furthermore, an excessively small gap can obstruct the flow of the coating liquid within a confined space, resulting in coating streaks. Above 150μm, the free fall of the liquid film from the die outlet to the aluminum plate surface is too large, making it prone to edge shrinkage, droplet splashing, or uneven coating width during descent. Moreover, the stability of the liquid film is difficult to guarantee during wide-width coating. The 50μm~150μm range has been experimentally verified as the optimal range that balances safety and coating quality.

[0079] A coating thickness deviation of ±1μm means that the difference between the maximum and minimum wet film thickness of the overprinted coating or protective coating across the entire surface of the aluminum plate does not exceed 2μm (i.e., the deviation relative to the target thickness is within ±1μm). This accuracy is achieved through the coordinated control of a high-precision metering pump (feed flow accuracy ±0.1%) and a die fine-tuning mechanism (adjustment accuracy at the micrometer level).

[0080] In actual production, non-contact gaps can be detected in real time online using laser displacement sensors. These sensors are installed on both sides of the coating die head, measuring the distance from the lower end face of the die head to the surface of the aluminum plate, with a detection accuracy of ±1μm. When the detected gap value deviates from the set range, the die head fine-tuning mechanism automatically performs vertical lifting compensation adjustment. Coating thickness can be detected using an online optical thickness gauge or a beta-ray thickness gauge. The online thickness gauge scans and measures the wet film thickness immediately after coating, and the detection results are fed back to the feeding system and the die head fine-tuning mechanism, forming a closed-loop control system.

[0081] As described above, controlling the distance between the coating die and the aluminum plate within 50μm~150μm ensures that there is absolutely no physical contact between the die and the wet base color pattern layer during the coating process, fundamentally eliminating the damage to the uncured wet ink pattern caused by contact coating. The coating thickness deviation is controlled within ±1μm, achieving precision coating with a film thickness deviation of <5%, ensuring uniform thickness of the overlay coating and avoiding color differences and concentrated stress from curing shrinkage caused by uneven thickness. This micron-level gap combined with high-precision control allows this process to be applied to the precision coating of various automotive aluminum plates (such as steering wheel emblems, trim strips, wheel covers, etc.).

[0082] As one implementation method of this embodiment, the non-contact narrow slit coating method is carried out in an airtight protective cavity, which is equipped with a positive pressure dust-free purification system to achieve an environmental cleanliness level of Class 10000.

[0083] In this embodiment, the airtight protective chamber refers to the entire narrow-slit coating machine and its coating work area enclosed within a sealed shell or chamber. This chamber is made of transparent materials (such as tempered glass or polycarbonate) or stainless steel plates. All joints within the chamber are equipped with sealing structures, and air curtain seals or labyrinth seals are installed at the inlet and outlet to ensure isolation between the internal space of the chamber and the external workshop environment. The function of the airtight protective chamber is to create a clean coating environment unaffected by external dust, lint, or personnel movement. The positive pressure cleanroom system includes a fan and a high-efficiency particulate air (HEPA or ULPA) filter. The fan draws in outside air, filters it through the HEPA filter, and then delivers it into the airtight protective chamber, creating a positive pressure by making the internal air pressure slightly higher than the external environment (typically 10 Pa to 30 Pa higher than the external atmospheric pressure). The positive pressure ensures that unfiltered external air does not seep into the chamber through gaps. The air cleanliness inside the filtered chamber reaches Class 10000 (equivalent to ISO 7 in ISO 14644-1, meaning that the number of particles ≥0.5μm in each cubic meter of air does not exceed 352,000), effectively controlling the risk of external dust particles falling onto the wet coating surface during the coating process and ensuring the appearance quality of the coating.

[0084] During narrow-slot coating, the coating liquid is completely exposed as it reaches and levels the aluminum plate surface after being extruded from the die. This makes it highly susceptible to adsorbing suspended particles from the air. Once these particles fall into the coating and solidify, they form raised particle defects, severely impacting the appearance yield. Class 10,000 cleanliness ensures that the particle concentration in a unit volume of air is controlled at an extremely low level. Combined with positive pressure protection, this eliminates particle defects at the source, providing a crucial guarantee for high yield (≥85%).

[0085] As described above, the airtight protective chamber, combined with the positive pressure dust-free purification system, enables the environmental cleanliness of the coating area to reach Class 10000, effectively controlling the concentration of airborne particulate matter during the coating process, reducing the risk of particulate defects caused by dust falling into the wet coating, and ensuring the appearance quality of the coating.

[0086] As one embodiment of this invention, the coating liquid used in the narrow slot coating machine is supplied by a high-precision metering pump and is equipped with a solvent compensation device to adjust the viscosity of the coating liquid in real time to match the solvent system of the base color ink.

[0087] In this embodiment, the high-precision metering pump is a device used to precisely control the flow rate of the coating liquid from the storage tank to the coating die. It can be a piston metering pump, gear metering pump, or screw metering pump. The solvent compensation device includes an online viscometer, a solvent storage tank, a mixer, and an automatic control valve. The online viscometer is installed in the supply pipeline to detect the viscosity of the coating liquid in real time. When the viscosity is detected to have increased due to solvent evaporation and exceeded the preset allowable deviation range, the control system automatically opens the valve of the solvent storage tank, adding an appropriate amount of solvent (the same as or compatible with the base color ink) to the mixer. After being thoroughly mixed in the mixer, the solution is then fed into the coating die, causing the viscosity of the coating liquid to return to near the target value in real time.

[0088] The core function of the solvent compensation device is to adjust the viscosity of the coating liquid in real time to match the solvent system of the base color ink. Matching means that the solvent composition in the coating liquid and the solvent composition in the base color ink are as consistent as possible or similar (at least have good miscibility) so that the interfacial tension is matched when the two come into contact.

[0089] When a wet overcoating solution is applied over a wet base color ink layer, the two wet films come into contact at the interface. If the solvent systems of the two layers are incompatible (e.g., one is a polar solvent system and the other is a non-polar solvent system), a surface tension gradient will form at the interface, triggering the Marangoni convection effect. This can lead to pinholes (coating shrinkage exposing the base layer), micro-pits (small circular defects), or bubbles (cavitation formed by internal gas expansion) on the coating surface. These defects are less common in traditional pre-baking coating processes because the base color layer has already surface-dried and the solvent has evaporated, eliminating the need for a wet-on-wet interface. However, in wet-on-wet processes, solvent compatibility becomes a key factor in determining interface quality. Adjusting the viscosity of the coating solution in real time using a solvent compensation device essentially maintains a stable ratio of solvent components in the coating solution, ensuring good miscibility and interfacial tension matching between the coating solution and the base color ink's solvent system.

[0090] As described above, a high-precision metering pump (flow accuracy ±0.1%) and a solvent compensation device adjust the viscosity of the coating liquid in real time, ensuring high compatibility with the solvent system of the base color ink. This avoids interface defects such as pinholes, craters, and bubbles caused by differences in solvent tension when the two layers of wet ink come into contact. The high-precision metering pump ensures a constant coating amount, eliminating uneven coating thickness caused by fluctuations in the material supply.

[0091] As one implementation of this embodiment, in step four, the baking equipment is a segmented hot air circulating oven, which is divided into a preheating section and a curing section along the aluminum plate conveying direction. The temperature of the preheating section is 120℃~150℃ and the processing time is 3min~5min. The temperature of the curing section is 160℃ and the processing time is 15min~20min.

[0092] In this embodiment, the segmented hot air circulating oven refers to a baking equipment divided into two or more independent temperature zones along the aluminum plate conveying direction. Each temperature zone is equipped with an independent heater and circulating fan, and different temperatures can be set. Hot air circulation means that the heated air is driven by the circulating fan to circulate repeatedly inside the oven, forming a uniform temperature field and avoiding local overheating or uneven baking. Preheating section: temperature is 120℃~150℃, processing time is 3min~5min. The preheating section temperature is lower than the curing start temperature of the ink system (usually around 150℃). At this temperature, the solvent evaporates but the resin has not yet undergone significant cross-linking. The processing time corresponds to the total time the aluminum plate passes through the preheating section (= preheating section length / conveyor speed). The range of 3min~5min ensures that the solvent has sufficient time to fully evaporate (especially since the total solvent content of the double-layer wet film is high), while avoiding excessive time that would cause the coating to be overheated and prematurely cured. Curing section: temperature is 160℃, processing time is 15min~20min. The curing section temperature is set to the optimal cross-linking temperature of the selected ink system (such as amino acrylic system). 160℃ is a commonly used curing temperature for this type of system in industrial baking. DSC (Differential Scanning Calorimetry) testing has proven that the crosslinking reaction rate is moderate and the conversion rate is high at this temperature. A processing time of 15min~20min ensures that the crosslinking reaction is fully carried out (conversion rate ≥95%), while avoiding coating embrittlement or yellowing caused by excessive crosslinking.

[0093] It should be noted that: if the preheating temperature is too low or the time is too short, the solvent will not fully evaporate before entering the curing stage. At high temperatures, the residual solvent will rapidly vaporize, generating internal pressure and leading to bubble defects. If the preheating temperature is too high or the time is too long, the coating may begin to cross-link during the preheating stage, resulting in insufficient penetration of the molecular chains at the interface between the overlay layer and the base layer, affecting the formation of the integrated structure. If the curing temperature is below 160℃ or the time is less than 15 minutes, the cross-linking will be insufficient, and the coating's hardness, adhesion, and chemical resistance will not meet the standards. If the curing temperature is above 160℃ or the time is more than 20 minutes, it may cause the coating to yellow or become over-crosslinked and brittle, while also increasing energy consumption and becoming uneconomical. The combination of preheating parameters of 120℃~150℃ and 3min~5min with curing parameters of 160℃ and 15min~20min constitutes the optimal baking curve for solvent-based thermosetting coating systems.

[0094] As described above, the preheating stage (120~150℃, 3~5min) ensures that the two wet coating layers are heated evenly and the solvent evaporates fully, avoiding the formation of bubbles due to solvent residue caused by rapid high-temperature heating. The curing stage (160℃, 15~20min) allows the two ink layers to complete the cross-linking and curing reaction simultaneously in the same thermal field, forming an integrated laminated structure. Precise segmented temperature control balances curing efficiency and coating quality, ensuring that the cured coating has both high hardness and scratch resistance, while maintaining good flexibility and adhesion, meeting the stringent requirements of automotive trim parts for weather resistance and chemical resistance.

[0095] As one implementation method of this embodiment, in step two, the conveyor belt for conveying the aluminum plate substrate is made of antistatic, low-adsorption silicone material, and the surface roughness Ra of the conveyor belt is ≤0.8μm.

[0096] In this embodiment, the conveyor belt has antistatic properties and a volume resistivity typically ≤10. 6 Ω·cm. The antistatic function is achieved by adding conductive fillers (such as carbon black, carbon nanotubes, or metal oxides) to the silicone material or by using antistatic agents. The purpose of antistatic is to prevent the accumulation of static electricity due to friction during conveyor belt operation. Static electricity can attract dust particles from the air and discharge at the edges of the aluminum plate, potentially leading to dust adsorption or electrical breakdown defects at the edges of wet ink. Silicone material has excellent anti-adsorption properties for organic substances like inks. When a small amount of ink is accidentally contaminated on the reverse side of the aluminum substrate, or when wet ink slightly overflows at the edges of the aluminum plate, low adsorption ensures that the ink will not be adsorbed by the conveyor belt and transferred to subsequent workpieces, causing secondary contamination. Low adsorption is mainly achieved through the chemical inertness (low surface energy) and smooth surface of the silicone itself. Ra (arithmetic mean roughness) ≤ 0.8 μm indicates that the bearing surface of the conveyor belt is very smooth. This roughness level ensures that the back of the aluminum substrate does not develop scratches due to friction during conveying. At the same time, the smooth surface also reduces the accumulation and transfer of dust on the belt surface.

[0097] As described above, the antistatic silicone material prevents electrostatic adsorption of dust from causing secondary pollution to the wet coating; its low adsorption properties prevent the belt from sticking to or transferring with the wet ink; and its ultra-smooth surface with Ra≤0.8μm ensures that the back and edges of the aluminum plate are not scratched or imprinted during the conveying process, thus fully guaranteeing the appearance quality of the workpiece.

[0098] As one implementation method of this embodiment, the screen printing speed, wet conveying speed, narrow slit coating speed, and baking temperature are all controlled in a closed loop by a central PLC control system throughout the entire process.

[0099] In this embodiment, a PLC (Programmable Logic Controller) is a commonly used control device in the field of industrial automation. It contains a central processing unit, input / output module, communication module and power supply module. It can receive signals from various sensors (temperature sensor, speed sensor, position sensor, pressure sensor, etc.), and after logic operation and PID (proportional-integral-derivative) adjustment, send control commands to various actuators (motor driver, heater controller, valve actuator, etc.).

[0100] Linkage refers to the interrelation of control parameters according to a preset mathematical model, rather than independent adjustment. For example, when the screen printing speed increases due to changes in the material feeding speed, the conveyor speed, narrow-slit coating speed, and baking conveyor speed increase proportionally to ensure consistent workpiece flow across processes, preventing accumulation or gaps. Closed-loop refers to a control system employing a negative feedback adjustment mechanism: setting a target value → detecting the actual value → calculating the deviation → outputting the adjustment amount → executing the adjustment → re-detecting, forming an automatic cycle that ensures the actual value always tracks the target value.

[0101] The screen printing speed (affects printing cycle time and ink layer thickness), wet conveying speed (affects conveying time and environmental exposure duration), slot coating speed (affects coating thickness and uniformity), and baking temperature (affects curing effect) are the four most significant variables affecting the final product quality throughout the entire process.

[0102] Taking the closed-loop control of baking temperature as an example, its working principle is explained as follows: The operator sets the target temperature of the curing section to 160℃ through the human-machine interface; the thermocouple temperature sensor in the curing section detects the actual temperature in real time and transmits it to the PLC; the PLC compares the actual temperature with the target temperature (160℃) and calculates the deviation value; if the actual temperature is lower than 160℃, the PLC increases the output power of the heater; if it is higher than 160℃, the PLC reduces the heater power or starts the cooling fan; after adjustment, the temperature is detected again, and the above process is repeated until the actual temperature stabilizes within the allowable deviation range (±1℃) of the target temperature.

[0103] As described above, the central PLC control system monitors and adjusts key parameters such as conveying speed, temperature, pressure, and coating gap of each unit in real time throughout the entire process, realizing fully automated continuous production, greatly reducing the frequency of manual intervention, avoiding human error, ensuring high consistency of product quality between batches, and fully adapting to the needs of large-scale mass production in the automotive industry.

[0104] like Figure 2 As shown, this embodiment also provides a stereoscopic visual coating equipment for automotive decorative aluminum panels, including a feeding unit 1, a screen printing unit 2, a wet conveying unit 3, a narrow slit coating unit 4, and a baking and curing unit 5 arranged sequentially along the aluminum panel conveying direction;

[0105] The screen printing unit 2 is located at the discharge end of the feeding unit 1 and is used to print different colors or different brightness of base color inks on different areas of the aluminum plate substrate to form a wet base color pattern layer with regional visual differences.

[0106] The wet conveying unit 3 is connected between the discharge end of the screen printing unit 2 and the feed end of the narrow-slit coating unit 4. The wet conveying unit 3 has a closed dust-free conveying channel, which is used to directly convey the aluminum plate with the wet base color pattern layer to the narrow-slit coating unit without baking or surface drying, and keep the base color ink in an uncured wet state during the process.

[0107] The narrow-slit coating unit 4 has a non-contact narrow-slit coating die head. The non-contact narrow-slit coating die head and the aluminum plate surface are provided with a coating gap that does not have physical contact, which is used to apply an overlay coating or protective coating on top of the wet base color pattern layer.

[0108] The baking and curing unit 5 is located at the discharge end of the narrow slit coating unit 4. The baking and curing unit 5 has a heating chamber for heating and curing the coated aluminum plate in one go, so that the wet base color pattern layer and the overcoated coating or protective coating are cross-linked and cured at the same time to form an integrated laminated structure.

[0109] In this embodiment, the equipment consists of five units arranged sequentially along the aluminum plate conveying direction. The spatial relationship between the units is as follows: the feeding unit is located at the front end, serving as the input port for the aluminum plate substrate; the screen printing unit is connected to the discharge end of the feeding unit and completes the base color printing; the wet conveying unit connects the screen printing unit and the narrow-slit coating unit, acting as a bridge; the narrow-slit coating unit is located after the discharge end of the wet conveying unit and completes the overlay coating; the baking and curing unit is located after the discharge end of the narrow-slit coating unit and completes the final curing. The sequential arrangement along the aluminum plate conveying direction indicates that the spatial arrangement of the units is consistent with the process flow of the aluminum plate, and there is no functional interruption between the units (such as the absence of independent baking and drying sections or cooling sections).

[0110] Unlike existing technologies, the technical solution of this application integrates the feeding, screen printing, wet conveying, narrow-slit coating, and baking / curing units sequentially along the conveying direction into a complete production line. Each unit has a clearly defined function and is tightly integrated, realizing the industrialization of a combined process of wet-to-wet screen printing, narrow-slit coating, and single-stage baking / curing. It eliminates the need for a separate intermediate baking oven and cooling section found in traditional processes, significantly reducing the overall length of the equipment and saving workshop space. This equipment can be upgraded from existing screen printing production lines by adding a narrow-slit coating unit and a wet conveying channel, without requiring the reconstruction of the entire production line, thus possessing significant industrial application value. The synergistic effect of the structural design and functional limitations of each unit enables the equipment to stably produce automotive decorative aluminum panels with a three-dimensional visual effect and excellent coating quality, maintaining a product yield consistently above 85%, combining aesthetics and practicality.

[0111] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for applying a three-dimensional visual coating to automotive decorative aluminum panels, characterized in that, Includes the following steps: Step 1: Print different colors or different brightness levels of base ink on different areas of the aluminum substrate surface to form a wet base pattern layer with regional visual differences. Step 2: The wet base color pattern layer is conveyed to the narrow slit coating station without baking or surface drying, and the base color ink is kept in an uncured wet state during this process; Step 3: Using a non-contact narrow-slit coating method, apply an overlay coating or protective coating on top of the wet base color pattern layer. During the coating process, the coating die head and the wet base color pattern layer remain in no physical contact. Step 4: The coated aluminum plate is sent into a baking equipment for one-time heating and curing, so that the wet base color pattern layer and the overcoated coating or protective coating are cross-linked and cured at the same time to form an integrated layered structure.

2. The method for applying a three-dimensional visual coating to automotive decorative aluminum panels according to claim 1, characterized in that, In step one, the colors, brightness, or brushed textures of the different areas are different, and the regional visual differences are formed by the interlacing of colors and the transition of light and dark between the areas.

3. The method for applying a three-dimensional visual coating to automotive decorative aluminum panels according to claim 1, characterized in that, In step two, the conveying process is carried out in a closed, dust-free channel, with the temperature inside the channel controlled at 23±2℃ and the relative humidity at 50±5%RH. The conveying speed is synchronized with the speed of screen printing and narrow-slit coating, and the conveying speed is 0.5m / min to 5m / min.

4. The method for applying a three-dimensional visual coating to automotive decorative aluminum panels according to claim 1, characterized in that, In step three, the non-contact narrow slit coating method uses a narrow slit coating machine. The non-contact gap between the coating die head of the narrow slit coating machine and the surface of the aluminum substrate is 50μm~150μm, and the coating thickness deviation is controlled within ±1μm.

5. The method for applying a three-dimensional visual coating to automotive decorative aluminum panels according to claim 4, characterized in that, The non-contact narrow-slit coating method is carried out in an airtight protective chamber, which is equipped with a positive pressure dust-free purification system to ensure that the environmental cleanliness reaches Class 10000.

6. The method for applying a three-dimensional visual coating to automotive decorative aluminum panels according to claim 4, characterized in that, The coating liquid used in the narrow slot coating machine is supplied by a high-precision metering pump and is equipped with a solvent compensation device to adjust the viscosity of the coating liquid in real time to match the solvent system of the base color ink.

7. The method for applying a three-dimensional visual coating to automotive decorative aluminum panels according to claim 1, characterized in that, In step four, the baking equipment is a segmented hot air circulating oven, which is divided into a preheating section and a curing section along the aluminum plate conveying direction. The temperature of the preheating section is 120℃~150℃ and the processing time is 3min~5min. The temperature of the curing section is 160℃ and the processing time is 15min~20min.

8. The method for applying a three-dimensional visual coating to automotive decorative aluminum panels according to claim 1, characterized in that, In step two, the conveyor belt for conveying the aluminum plate substrate is made of anti-static, low-adsorption silicone material, and the surface roughness Ra of the conveyor belt is ≤0.8μm.

9. The method for stereoscopic visual coating of automotive decorative aluminum panels according to any one of claims 1 to 8, characterized in that, Throughout the entire process, the screen printing speed, wet conveying speed, narrow-slit coating speed, and baking temperature are all controlled in a closed-loop manner through a central PLC control system.

10. A stereoscopic visual coating equipment for automotive decorative aluminum panels, characterized in that, It includes a feeding unit, a screen printing unit, a wet conveying unit, a narrow-slot coating unit, and a baking and curing unit arranged sequentially along the aluminum plate conveying direction; The screen printing unit is located at the discharge end of the feeding unit and is used to print different colors or different brightness of base color inks on different areas of the aluminum plate substrate surface to form a wet base color pattern layer with regional visual differences. The wet conveying unit is connected between the discharge end of the screen printing unit and the feed end of the narrow-slit coating unit. The wet conveying unit has a closed dust-free conveying channel for directly conveying the aluminum plate with the wet base color pattern layer to the narrow-slit coating unit without baking or surface drying, and keeping the base color ink in an uncured wet state during the process. The narrow-slit coating unit has a non-contact narrow-slit coating die head, and the non-contact narrow-slit coating die head and the aluminum plate surface are provided with a coating gap without physical contact, which is used to apply an overlay coating or protective coating on the wet base color pattern layer. The baking and curing unit is located at the discharge end of the narrow-slit coating unit. The baking and curing unit has a heating chamber for heating and curing the coated aluminum plate in one go, so that the wet base color pattern layer and the overcoated coating or protective coating are cross-linked and cured at the same time to form an integrated layered structure.

Images