A laser cleaning and texturing method and apparatus suitable for thin metal sheets

Abstract

This invention discloses a laser cleaning and texturing method and apparatus suitable for thin metal sheets. The method includes the following steps: S1, performing preliminary mechanical polishing on the surface of a thin metal sheet continuously conveyed at a set linear speed. S2, using an infrared continuous laser beam to simultaneously irradiate the upper and lower surfaces of the pretreated thin metal sheet in an elliptical trajectory to remove residual rust and oil stains; wherein the infrared continuous laser beams irradiating the upper and lower surfaces of the thin metal sheet are staggered along the length of the thin metal sheet. S3, using an ultraviolet pulsed laser beam to scan and etch an array of micropits on the surface of the cleaned thin metal sheet to be composited, forming a uniform surface texturing morphology. This method integrates mechanical pretreatment, double-sided laser cleaning, and precise laser texturing, and achieves efficient, online, green, and controllable integrated cleaning and texturing of thin metal sheets based on online operating conditions.

Description

Technical Field

[0001] This invention relates to the field of metal laser processing technology, and specifically to a method and apparatus for laser cleaning and texturing of thin metal sheets in a steel / copper sheet composite production line. Background Technology

[0002] During the composite processing of steel / copper strips, rust or stains on the surface of both the steel strip and the copper strip can affect the performance of the steel / copper composite plate. For example, rust on the steel strip surface can prevent the steel / copper interface from bonding tightly, leading to delamination and peeling after lamination, significantly reducing the mechanical strength of the composite plate and failing to meet the requirements of subsequent machining and load-bearing. Oil stains on the copper strip surface can form interface impurities during the lamination process, affecting not only the bonding strength but also causing defects such as bubbles and pinholes on the surface of the composite plate, reducing the product qualification rate. If the surface of the steel / copper strip is not effectively roughened and is too smooth, it will further weaken the bonding force between the interfaces, causing interlayer slippage or even breakage during subsequent bending, stamping, and other processing. In addition, stains and rust can also affect the uniformity of heat conduction during the lamination process, resulting in uneven temperature distribution, which in turn affects the uniformity of the composite plate's structure and overall performance, increasing the cost of rework and scrapping, and shortening the service life of the composite plate, failing to meet the requirements of high precision and high performance.

[0003] Currently, the production process of steel / copper strip composites requires separate degreasing, polishing, and surface roughening processes, along with corresponding equipment (which is relatively large in size and footprint) and operators. These processes have the following drawbacks: First, chemical cleaning requires acidic or alkaline solutions, generating large amounts of waste liquid and causing serious environmental pollution; the treated surface is also prone to secondary oxidation. Second, mechanical polishing is inefficient, difficult to handle complex surfaces, and the polishing wheels wear out quickly, resulting in high material costs. Third, mechanical roughening methods (such as sandblasting and knurling) have poor control precision, easily damaging the substrate and making selective roughening difficult in specific areas. Fourth, the processes are scattered across different equipment, requiring multiple handling and temporary storage, resulting in large footprints, high labor costs, and inability to seamlessly integrate with high-speed continuous production lines. Therefore, there is an urgent need for an efficient, environmentally friendly, and easily integrated online pretreatment method. Summary of the Invention

[0004] To address the technical problems of existing steel / copper composite plate pretreatment methods, such as fragmented processes, low efficiency, severe pollution, poor texturing accuracy, and significant damage to the substrate, this invention provides a laser cleaning and texturing method and apparatus suitable for thin metal sheets. It integrates mechanical pretreatment, double-sided laser cleaning, and precise laser texturing, and uses online parameter matching to achieve efficient, online, green, and controllable integrated cleaning and texturing of thin metal sheets, significantly improving the interfacial bonding strength of the composite plate.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides a laser cleaning and texturing method suitable for thin metal sheets, comprising the following steps: S1. Mechanical grinding and polishing pretreatment: The surface of the metal sheet, which is continuously conveyed at a set linear speed, is subjected to preliminary mechanical polishing to remove large pieces of rust, heavy oil stains, and attached debris from the surface of the metal sheet.

[0006] S2, Online Laser Cleaning: Using an infrared continuous laser beam (preferably 1064nm wavelength), the upper and lower surfaces of the pretreated metal sheet are simultaneously irradiated in an elliptical trajectory to remove residual rust and oil stains from the surface. Among them, the infrared continuous laser beams irradiating the upper and lower surfaces of the metal sheet are staggered along the length of the metal sheet; The process parameters for infrared continuous laser are as follows: laser power 120-200W, scanning speed 2000-4000mm / s, frequency 50-100kHz, and scanning line width greater than the width of the steel strip (preferably, the scanning line width is 2-5mm greater than the width of the steel strip to avoid positional deviations caused by accidental swaying of the steel strip during transmission, which may result in the scanning area not being covered; if it is too much greater, it will affect the processing efficiency). At the same time, the distance between the laser focus and the surface of the metal sheet is set using a positive defocusing method, with a defocusing range of +0.1mm to +0.3mm, to avoid excessive ablation of the substrate.

[0007] Under the control of the above parameters, the laser energy is selectively absorbed by the surface rust and oil layers, causing them to rapidly heat up, vaporize, or peel off, while the metal sheet substrate remains largely undamaged due to its high reflectivity and thermal conductivity. After cleaning, the rust and oil on the metal sheet surface are completely removed, revealing a uniform metallic luster and reducing surface roughness.

[0008] S3, Online Laser Hair Resurfacing: Using an ultraviolet pulsed laser beam, an array of micro-pits is etched on the surface of the cleaned metal sheet to be composited, forming a uniform surface roughening morphology.

[0009] Furthermore, in step S2, a beam of continuous infrared laser light is uniformly divided into two paths by a flying optical path, which are then irradiated onto the upper and lower surfaces of the metal sheet, respectively.

[0010] Specifically, an infrared continuous-wave laser (preferably with a wavelength of 1064nm) emits laser light that is split and shaped via a flying optical path. After passing through a beam-shaping module, the light is transmitted through a light-shielding tube to two laser cleaning heads located above and below the metal sheet. The two laser cleaning heads are positioned opposite each other, preferably staggered left and right to reduce the impact of heat accumulation. Each laser cleaning head integrates a 3D dynamic focusing scanning galvanometer, which irradiates the focused laser beam onto the upper and lower surfaces of the metal sheet in an elliptical trajectory. A non-polarizing beam splitter is used for beam splitting, with an overall 50:50 division, resulting in minimal power difference between the two split infrared laser beams.

[0011] Furthermore, since the normal heat-affected zone is only a few millimeters, in step S2, the misalignment distance between the infrared continuous laser beams irradiating the upper and lower surfaces of the metal sheet is ≥20mm.

[0012] Furthermore, in step S2, the infrared continuous laser is a nanosecond-level continuous laser and / or a picosecond-level continuous laser.

[0013] Experiments have verified that both picosecond and nanosecond continuous lasers with appropriate process parameters can effectively remove surface rust and stains. Nanosecond continuous laser treatment results in a more pronounced metallic luster. Picosecond laser cleaning improves surface roughness to some extent. After picosecond laser cleaning, the surface microhardness of the mold shows no significant difference; after nanosecond laser cleaning, the surface microhardness decreases slightly, which analysis indicates is due to surface remelting or thermal effects.

[0014] Therefore, preferably, the infrared continuous laser uses a combination of nanosecond-level continuous laser and picosecond-level pulsed laser.

[0015] Furthermore, in step S3, the ultraviolet pulsed laser is a nanosecond or picosecond pulsed laser with a wavelength of 355nm, and its process parameters are: laser power 50-100W, scanning speed 1000-3000mm / s, and frequency 10-100kHz.

[0016] Specifically, the laser beam is transmitted via optical fiber to a high-speed scanning galvanometer. The galvanometer controls the laser beam to rapidly scan and etch the steel strip in the area to be composited, forming multiple micro-pits. The ultraviolet laser has a short wavelength and high photon energy, and material removal is achieved through a cold processing mechanism with a very small heat-affected zone, which can avoid the formation of melts or thermal cracks at the edges of the micro-pits.

[0017] Experiments have shown that ultraviolet pulsed lasers, which use nanosecond-level pulsed lasers, are low in cost, have a large spot size, and achieve faster etching speeds.

[0018] Furthermore, in step S3, the diameter and depth of the array of micro-pits formed by scanning etching can be designed according to actual needs, specifically with a diameter of 50-200μm and a depth of 20-100μm.

[0019] This micron-scale lattice structure can significantly increase the physical contact area and interfacial friction during the composite of metal sheets, thereby significantly improving the interfacial bonding strength of the composite sheet and effectively preventing delamination, peeling and slippage defects.

[0020] Furthermore, the thickness of the metal sheet ranges from 1 to 6 mm, and the set linear velocity of the metal sheet is 1 to 3 m / min.

[0021] When the conveying speed of the metal sheet changes, the control system synchronously adjusts the laser scanning speed in step S2 according to a direct proportional relationship to maintain a constant laser energy input per unit area, thereby ensuring the consistency of the cleaning effect.

[0022] Furthermore, while steps S2 and S3 are being performed, a local negative pressure is created in the laser processing area and auxiliary gas is blown out to collect the generated dust in real time.

[0023] Furthermore, in step S1, polishing wheels arranged opposite each other are used to polish the upper and lower surfaces of the metal sheet simultaneously. The distance between the upper and lower polishing wheels is adjusted according to the thickness of the metal sheet. The dust generated during the polishing process is collected in real time through a closed cover and a negative pressure suction system to prevent environmental pollution.

[0024] Furthermore, it also includes step S4, where the roughened metal sheet is conveyed to the discharge station, where a soft brush gently removes the trace amounts of dust remaining on the surface, and a negative pressure suction system is used to remove the dust, ensuring that the surface of the output metal sheet is clean and can directly enter the next composite process.

[0025] In a second aspect, the present invention also provides an apparatus for implementing the above method, comprising a housing having a sealed processing cavity formed therein; The machine body shell is provided with a feeding grinding and polishing component, a laser cleaning component and a laser texturing component arranged sequentially from the feeding side to the discharging side; The laser cleaning assembly includes an infrared continuous laser, a flying optical path, an upper laser cleaning head, and a lower laser cleaning head. The laser emitted by the infrared continuous laser is split by the flying optical path and transmitted to the upper and lower laser cleaning heads respectively, so as to simultaneously perform laser cleaning on the upper and lower surfaces of the metal sheet. The upper and lower laser cleaning heads are arranged alternately from left to right. The top of the outer casing of the machine body is provided with a dust extraction port, and a top dust extraction fan is installed in the dust extraction port. The top dust extraction fan is connected to an external dust removal device through a dust extraction pipe.

[0026] The above technical solution is adopted: This application integrates the feeding and polishing assembly, laser cleaning assembly, and laser texturing assembly sequentially along the feeding to discharging direction into a sealed housing. The laser cleaning assembly utilizes an infrared continuous laser with a flying beam splitter, allowing the upper and lower laser cleaning heads to be staggered left and right, enabling simultaneous laser cleaning of both the upper and lower surfaces of the thin metal sheet. This staggered arrangement also reduces the impact of heat accumulation. The working principle is as follows: After the thin metal sheet enters from the feeding side, it first undergoes mechanical polishing to remove large areas of rust, then undergoes double-sided infrared continuous laser cleaning to remove residual dirt, and finally undergoes laser texturing to create a micro-pitted surface. The entire processing takes place within a sealed chamber, with top ventilation creating negative pressure to prevent dust leakage. This solution achieves high equipment integration, significantly reduces floor space, can be directly adapted to continuous production line operations, doubles efficiency with simultaneous double-sided cleaning, and ensures a green and environmentally friendly processing environment through a sealed negative pressure system.

[0027] Furthermore, the laser texturing component includes a pulsed laser and a scanning galvanometer, wherein the laser emitted by the pulsed laser is focused by the scanning galvanometer onto the surface of the metal sheet to be composited.

[0028] The laser emitted by the ultraviolet pulsed fiber laser is focused and irradiated onto the cleaned side surface of the steel strip by a scanning galvanometer, creating micro-pits and forming a roughening effect, which can improve the bonding effect of the board interface in subsequent processes.

[0029] In practical applications, both the laser cleaning head and the ultraviolet pulsed fiber laser are equipped with 3D dynamic focusing scanning galvanometers. The processing area can cover the width of conventional metal thin plates (steel and copper thin plates). The dynamic focusing can adapt to the height difference on the surface of the thin plate and the slight fluctuations generated during material transmission. The spot size is fine and controllable, and it can accurately complete large-area cleaning and micro-scale dot matrix etching and texturing. The spot size after focusing by the galvanometer of the laser cleaning head and the galvanometer of the laser texturing are 0.5mm and 0.05mm, respectively.

[0030] Furthermore, the scanning galvanometers of the upper laser cleaning head, the lower laser cleaning head, and the laser texturing component are respectively mounted to the inner wall of the machine body via motion modules. Driven by the corresponding motion modules, the scanning galvanometers of the upper laser cleaning head, the lower laser cleaning head, and the laser texturing component move in the X-axis (lateral translation along the length of the metal sheet) and the Z-axis (vertical adjustment). This allows for adaptation to steel strips of different thicknesses and rapid switching between production specifications.

[0031] Furthermore, a first air blowing assembly, a second air blowing assembly, and a third air blowing assembly are respectively provided near the scanning galvanometer of the upper laser cleaning head, the lower laser cleaning head, and the laser texturing assembly for directionally blowing away the dust generated during processing.

[0032] Compressed air is blown out toward each laser processing area through the nozzles of the first, second, and third air blowing components, respectively, to blow away the stripped oxide dust from the processing position. This keeps the processing area clean, prevents secondary dust pollution, and improves the overall dust removal efficiency in conjunction with the dust extraction system.

[0033] Furthermore, the outer casing of the machine body is also provided with a first side dust extraction component and a second side dust extraction component. The first side dust extraction component, the first air blowing component, and the second air blowing component are respectively located on the left and right sides of the upper laser cleaning head. The first side dust extraction component is used to extract the dust blown out by the first air blowing component and the second air blowing component. The second side dust extraction component and the third air blowing component are respectively located on the left and right sides of the scanning galvanometer of the laser texturing component. The second side dust extraction component is used to extract the dust blown out by the third air blowing component.

[0034] To address the issue of dust dispersion that can still occur with top-mounted dust extraction and air blowing alone, a first and a second side-mounted dust extraction assembly were added. The first side-mounted dust extraction assembly, along with the first and second air blowing assemblies, is located on the left and right sides of the upper laser cleaning head, respectively, forming a counter-current airflow. The second side-mounted dust extraction assembly and the third air blowing assembly are located on the left and right sides of the scanning galvanometer of the laser texturing assembly, respectively. The air blowing assembly laterally directs the dust towards the opposite side-mounted dust extraction assembly, minimizing the path of dust from generation to collection and preventing dust dispersion within the cavity. This structure significantly improves the directional dust collection rate, reduces dust accumulation inside the equipment, and decreases maintenance frequency.

[0035] Furthermore, the first air blowing assembly, the second air blowing assembly, and the third air blowing assembly are located between the scanning galvanometer of the lower laser cleaning head and the laser texturing assembly.

[0036] To avoid airflow interference between multiple air blowing components, the air blowing components of the cleaning station and the fabrication station are spatially staggered, so that each station can blow independently and the airflow will not collide with each other, thus ensuring the blowing effect of each station.

[0037] Furthermore, the feeding and polishing assembly includes a first housing, which is installed inside the outer shell of the machine body on the feeding side. Inside the first housing, there are upper and lower polishing wheels arranged opposite each other with adjustable spacing. The metal sheet passes between the upper and lower polishing wheels. The upper and lower polishing wheels are respectively driven and connected to a grinding wheel motor. The grinding wheel motor is installed on the inner wall of the first housing. The side wall of the first housing has an outlet for the metal sheet to pass through.

[0038] Specifically, two grinding wheel motors are mounted on the inner wall of the first housing. Their spacing can be adjusted via bolts, thereby controlling the distance between the upper and lower grinding wheels (to accommodate metal sheets of different thicknesses). The metal sheet passes between the two rotating grinding wheels, quickly removing large areas of rust. The entire grinding and polishing process takes place within the enclosed first housing, which is also connected to a dust extraction pipe to promptly remove dust. This improvement achieves flexible adaptation to different thicknesses, high grinding and polishing efficiency, and controls dust pollution at its source.

[0039] Furthermore, a discharge assembly is provided inside the outer casing of the machine body near the discharge side. The discharge assembly includes a second housing, which is installed on the discharge side of the outer casing of the machine body. An inlet is provided on the side of the second housing away from the discharge side of the outer casing of the machine body. Brushes are respectively provided at the top and bottom of the inlet of the first housing and the outlet of the second housing.

[0040] As the metal sheet continues forward after being processed by the upper and lower grinding wheels, it passes through the hard brush at the discharge port of the first housing. This brush removes large pieces of grinding dust remaining on the metal sheet, which are then sucked away by the dust extraction pipe connected to the first housing. After laser cleaning and roughening, the metal sheet passes through the soft brush at the inlet of the second housing, where residual dust is brushed off and then sucked away by negative pressure through the dust extraction pipe connected to the second housing.

[0041] Furthermore, the first housing and the second housing are respectively connected to dust extraction pipes.

[0042] Furthermore, the machine body shell has a feed tray for winding and loading thin metal sheets on the feed side and the discharge side, respectively.

[0043] The feed tray on the inlet side is used to hold the wound metal sheets to be processed, and the metal sheets are continuously unwound and fed to the machine. After the metal sheets undergo grinding, polishing, cleaning, and roughening processes online, they are rewound by the discharge tray on the outlet side, forming an integrated "unwinding-processing-rewinding" operation process. This allows the equipment to be directly adapted to production lines without the need for additional handling or intermediate storage, making it particularly suitable for large-scale continuous automated production.

[0044] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention is the first to organically integrate three processes—mechanical rough grinding, infrared continuous laser fine cleaning, and ultraviolet pulsed laser texturing—into a single production line, achieving one-step online pretreatment of composite plates. In particular, the use of beam splitting technology to achieve simultaneous cleaning of both the upper and lower surfaces doubles the efficiency compared to the existing single-sided, multi-stage processing method, significantly improving production efficiency. Moreover, the infrared continuous laser beams irradiating the upper and lower surfaces of the metal sheet are arranged in a staggered manner to reduce the impact of heat accumulation.

[0045] (2) Based on a large number of process verification experiments, the infrared continuous laser parameters selected in this invention can effectively remove rust while controlling the surface roughness within a reasonable range. Microhardness testing showed that the surface hardness after laser cleaning was not substantially different from the original hardness of the substrate, proving that the thermal effect of this invention is negligible and will not damage the mechanical properties of the metal sheet.

[0046] (3) The present invention uses ultraviolet nanosecond or picosecond laser for texturing. Due to its cold processing characteristics, it can form micro-pits with regular shape and precise controllable size, and the heat-affected zone is extremely small.

[0047] (4) The present invention requires no chemical reagents throughout the process, generates only a small amount of solid dust, and achieves directional collection through a closed dust removal system combining blowing and extraction. There is no waste liquid discharge or dust overflow, making it a green and environmentally friendly pretreatment method.

[0048] (5) The feeding grinding and polishing component, the double-sided laser cleaning component and the laser texturing component of the present invention are sequentially integrated into a sealed machine shell along the feeding to discharging direction to form an integrated processing unit. It is directly compatible with the production line, with continuous process, high equipment integration, high degree of automation, improved processing efficiency, and the equipment is green and environmentally friendly.

[0049] Using a polishing wheel as a pretreatment tool enables the initial removal of large areas of rust and dirt, offering advantages such as high speed and efficiency. A continuous laser is used for both laser cleaning and polishing. An infrared continuous laser, combined with flying beam splitting technology, evenly divides a single laser beam into two paths, transmitting them to the upper and lower laser cleaning heads respectively. These heads are staggered left and right, enabling simultaneous laser cleaning of both the upper and lower surfaces of the steel strip. This staggered arrangement also reduces the impact of heat accumulation. A pulsed laser is used as a texturing tool to precisely texturize the areas of the steel strip that need to be bonded to the copper strip surface. This enhances the physical contact area and friction between the steel and copper interfaces, improving the bonding strength and effectively preventing defects such as delamination, peeling, and slippage after bonding. Precise texturing also avoids over-processing of non-bonded areas, reducing material loss and energy waste, and ensuring the overall flatness of the steel strip surface.

[0050] A top-mounted dust extraction fan is installed on the top of the machine casing, while air blowing and side dust extraction components are located near the laser processing area. Dust extraction pipes are connected inside the feeding and polishing components and the discharging components, forming a multi-level, three-dimensional dust removal structure. During processing, the air blowing and side dust extraction components create opposing airflows, and the top-mounted dust extraction fan maintains negative pressure throughout the cavity, ensuring the shortest and most thorough path for dust from generation to collection. This achieves fully enclosed dust removal throughout the entire process, meeting green manufacturing requirements. Attached Figure Description

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0052] Figure 1 The images show macroscopic views and magnified macroscopic details of the steel strip before and after laser cleaning in Example 1. Figure 2 Macroscopic images of Example 1 (infrared nanosecond laser) and Comparative Example 2 (infrared picosecond laser) after laser cleaning; Figure 3 The average microhardness diagrams are shown after conventional sandpaper polishing, and after laser cleaning in Example 1 (infrared nanosecond laser) and Comparative Example 2 (infrared picosecond laser). Figure 4 This is a schematic diagram of the internal structure of the laser cleaning and texturing device in this invention. Figure 1 ; Figure 5 This is a schematic diagram of the internal structure of the laser cleaning and texturing device in this invention. Figure 2 ; Figure 6 This is a schematic diagram of the internal structure of the feeding grinding and polishing assembly in this invention; The specific reference numerals in the attached figures are as follows: 1. Steel strip tray; 2. Machine casing; 3. Electrical cabinet. Feeding and polishing assembly 4, polishing wheel 401, feed inlet dust extraction pipe 402, grinding wheel motor 403, discharge outlet 404. Laser cleaning assembly 5, infrared continuous laser 501, flying optical path 502, light shield 503, lower laser cleaning head 504, upper laser cleaning head 505. Laser texturing component 6, ultraviolet pulsed fiber laser 601, Discharge assembly 7, inlet 701, outlet dust extraction pipe 702, First air blowing assembly 8, second air blowing assembly 9, third air blowing assembly 10, first side dust extraction assembly 11, second side dust extraction assembly 12, top dust extraction fan 13, top dust extraction fan pipe 14. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1 A laser cleaning and texturing method for steel strips includes the following steps: S1. Mechanical grinding and polishing pretreatment: The steel strip (2mm thick and 50mm wide) is continuously unwound from the steel strip reel at a linear speed of 2m / min. The upper and lower surfaces of the steel strip are polished simultaneously using grinding and polishing wheels arranged opposite each other. The distance between the upper and lower grinding and polishing wheels is adjusted according to the thickness of the steel strip. The dust generated during the polishing process is collected in real time through a closed cover and a negative pressure suction system to prevent environmental pollution.

[0055] S2, Online Laser Cleaning: Using an infrared continuous laser beam (preferably 1064nm wavelength), the emitted laser light is split and shaped via a flying optical path, then passes through a beam-shaping module and a light-shielding tube to two laser cleaning heads located above and below the steel strip. The two laser cleaning heads are positioned opposite each other, staggered left and right to reduce the impact of heat accumulation, with a distance of 50mm between them. Each laser cleaning head integrates a 3D dynamic focusing scanning galvanometer, which irradiates the focused laser beam onto the upper and lower surfaces of the steel strip in an elliptical trajectory, removing residual rust and oil.

[0056] Among them, the infrared continuous laser is a nanosecond-level continuous laser.

[0057] Infrared continuous laser beams irradiating the upper and lower surfaces of the steel strip are staggered along the length of the steel strip. The process parameters for infrared continuous laser are: laser power 120W, scanning speed 3000mm / s, frequency 100kHz, scanning line width 54mm, and laser spot size after focusing 0.5mm.

[0058] The distance between the laser focus and the steel strip surface is set using a positive defocusing method, with a defocusing range of +0.2mm. This increases the spot area, reduces the peak power, and avoids excessive ablation of the substrate.

[0059] S3, Online Laser Hair Resurfacing: Using an ultraviolet pulsed laser beam, an array of micro-pits is etched on the surface of the steel strip to be composited after cleaning, forming a uniform surface roughening morphology.

[0060] The ultraviolet pulsed laser is a nanosecond-level pulsed laser (because the production line has steel strips and copper strips, if outer red light is used, the absorption rate of copper strips would be too low. To take into account the production line products, ultraviolet light is more suitable). The wavelength is 355nm, and its process parameters are: laser power 90W, scanning speed 2000mm / s, frequency 50kHz, and the size of the focused laser spot is 0.05mm.

[0061] While steps S2 and S3 are being performed, a local negative pressure is created in the laser processing area and auxiliary gas is blown out to collect the generated dust in real time.

[0062] S4. Post-processing: After the roughening process is completed, the steel strip continues to be conveyed to the discharge station. The trace amounts of residual dust on the surface are gently brushed off by a soft brush, and the dust is sucked away by a negative pressure suction system to ensure that the surface of the output steel strip is clean and can directly enter the next composite process.

[0063] Example 2 A laser cleaning and texturing method suitable for copper strips includes the following steps: S1. Mechanical grinding and polishing pretreatment: The steel strip (2mm thick and 50mm wide) is continuously unwound from the steel strip reel at a linear speed of 2m / min. The upper and lower surfaces of the steel strip are polished simultaneously using grinding and polishing wheels arranged opposite each other. The distance between the upper and lower grinding and polishing wheels is adjusted according to the thickness of the steel strip. The dust generated during the polishing process is collected in real time through a closed cover and a negative pressure suction system to prevent environmental pollution.

[0064] S2, Online Laser Cleaning: Using an infrared continuous laser beam (preferably 1064nm wavelength), the emitted laser light is split and shaped via a flying optical path, then passes through a beam-shaping module and a light-shielding tube to two laser cleaning heads located above and below the steel strip. The two laser cleaning heads are positioned opposite each other, staggered left and right to reduce the impact of heat accumulation, with a distance of 50mm between them. Each laser cleaning head integrates a 3D dynamic focusing scanning galvanometer, which irradiates the focused laser beam onto the upper and lower surfaces of the steel strip in an elliptical trajectory, removing residual rust and oil.

[0065] Among them, the infrared continuous laser is a nanosecond-level continuous laser.

[0066] Infrared continuous laser beams irradiating the upper and lower surfaces of the steel strip are staggered along the length of the steel strip, with a distance of 20mm between them.

[0067] The process parameters for infrared continuous laser are: laser power 150W, scanning speed 4000mm / s, frequency 80kHz, scanning line width 54mm, and laser spot size after focusing 0.5mm.

[0068] The distance between the laser focus and the steel strip surface is set using a positive defocusing method, with a defocusing range of +0.2mm. This increases the spot area, reduces the peak power, and avoids excessive ablation of the substrate.

[0069] S3, Online Laser Hair Resurfacing: Using an ultraviolet pulsed laser beam, an array of micro-pits is etched on the surface of the steel strip to be composited after cleaning, forming a uniform surface roughening morphology.

[0070] The ultraviolet pulsed laser is a nanosecond-level pulsed laser with a wavelength of 355nm. Its process parameters are: laser power 80W, scanning speed 1500mm / s, and frequency 50kHz.

[0071] While steps S2 and S3 are being performed, a local negative pressure is created in the laser processing area and auxiliary gas is blown out to collect the generated dust in real time.

[0072] S4. Post-processing: After the roughening process is completed, the steel strip continues to be conveyed to the discharge station. The trace amounts of residual dust on the surface are gently brushed off by a soft brush, and the dust is sucked away by a negative pressure suction system to ensure that the surface of the output steel strip is clean and can directly enter the next composite process.

[0073] Comparative Example 1 Comparative Example 1 is a comparative test example of Example 1, and its difference from Example 1 is as follows: The two laser cleaning heads are positioned facing each other, one above the other.

[0074] Experiments have shown that when using the above method to laser clean copper, simultaneous heating of the upper and lower surfaces of the copper strip can easily lead to excessively high localized thermal effects, causing oxidation of the copper surface and affecting the laser-cleaned product. For excessively thin plates, it can cause deformation and discoloration.

[0075] Comparative Example 2 Comparative Example 2 is a comparative test example of Example 1, and its difference from Example 1 is as follows: In Comparative Example 2, an infrared picosecond laser was selected instead of an infrared nanosecond laser as the laser for laser cleaning.

[0076] Comparative Example 3 Comparative Example 3 is a comparative test example of Example 2, and its difference from Example 2 is as follows: In Comparative Example 3, an infrared nanosecond laser was used instead of an ultraviolet nanosecond laser as the laser for laser texturing. However, the absorption rate was too low and the texturing effect was poor when laser texturing copper strip material.

[0077] Performance testing: Figure 1 The images shown are macroscopic views and magnified views of the steel strip before and after laser cleaning in Example 1. It can be seen that laser cleaning can effectively remove surface rust.

[0078] Table 1 shows the surface roughness test values ​​of the uncleaned steel strip in Example 1. Table 2 shows the surface roughness test values ​​of the steel strip after laser cleaning in Example 1.

[0079] Table 1 parameter average value Maximum value Minimum value Standard deviation Ra (μm) 3.362 3.938 3.057 0.246 Rz (μm) 25.264 29.169 20.142 2.897 RSm (μm) 380.872 456.942 293.054 56.307 Table 2 parameter average value Maximum value Minimum value Standard deviation Ra (μm) 1.98 2.337 1.588 0.201 Rz (μm) 14.136 18.301 9.908 2.174 RSm (μm) 428.805 573.026 260.089 108.785 The surface roughness test data in Tables 1 and 2 further show that after laser cleaning, Ra (average roughness) and Rz (maximum height difference) are significantly reduced, indicating that the cleaning effectively removes the contaminants or oxide layer attached to the surface, making the surface smoother.

[0080] Figure 2 The image shows macroscopic images of Example 1 (infrared nanosecond laser) and Comparative Example 2 (infrared picosecond laser) after laser cleaning. It can be seen that both picosecond and nanosecond lasers can effectively remove surface rust and stains, and the nanosecond treatment shows a more obvious metallic luster.

[0081] Figure 3 The average microhardness graphs are shown for conventional sandpaper polishing and for Example 1 (infrared nanosecond laser) and Comparative Example 2 (infrared picosecond laser) laser cleaning. It can be seen that there is no significant difference in the microhardness of the steel strip surface after picosecond laser cleaning; after nanosecond laser cleaning, the microhardness of the steel strip surface decreases slightly, which may be due to surface remelting or thermal effects, but the overall impact is not significant.

[0082] Example 3 This embodiment provides a laser cleaning and texturing device adapted to a steel / copper thin-plate composite production line, such as... Figures 4 to 6 As shown, it includes the following: Steel strip tray 1 is mainly used to load the metal steel strip to be cleaned and the metal steel strip after cleaning and roughening. The feeding and polishing assembly 4 is bolted to the inner left wall of the machine housing 2. A steel belt enters the feeding and polishing assembly 4 through the feed inlet 701 on the left side of the machine housing 2, passing through two opposing polishing wheels 401. The two polishing wheels 401 are connected to two grinding wheel motors 403, which rotate when energized, driving the polishing wheels 401 to perform preliminary polishing of the steel belt, removing large contaminants or adhering substances. The two grinding wheel motors 403 are mounted on the housing of the feeding and polishing assembly 4, and their spacing can be adjusted with bolts to control the distance between the two polishing wheels 401 (to accommodate steel belts of different thicknesses). A dust extraction pipe 402 is fixed to the housing of the feeding and polishing assembly 4 and connected to external dust extraction equipment to remove contaminants and dust generated by the two polishing wheels 401 from the steel belt, preventing dust overflow. A hard brush is installed at the outlet 404 of the feed grinding and polishing assembly 4. After being processed by the upper and lower grinding and polishing wheels 401, the steel belt continues to move forward. It will pass through the hard brush, which will remove the large pieces of grinding and polishing dust remaining on the steel belt. The dust will then be sucked away by the dust collector connected to the dust extraction pipe 402 at the feed inlet.

[0083] The outer casing 2 completely surrounds the equipment, preventing dust from spilling out during the cleaning and texturing of the steel strip and thus avoiding any negative impact on the external environment. The outer casing 2 is bolted to the top of the electrical cabinet 3. A top dust extraction fan 13 is installed on the top of the outer casing 2 and connected to the dust removal equipment outside the equipment through the top dust extraction fan pipe 14. The top dust extraction fan 13 creates negative pressure inside the outer casing 2 to prevent dust from spilling out during the cleaning and texturing of the steel strip.

[0084] The laser cleaning assembly 5 includes a flight optical path 502, which is fixed to the outer shell 2 of the aforementioned body by bolts. The laser emitted by the infrared continuous laser 501 is transmitted to the galvanometer of the lower laser cleaning head 504 after optical path design, beam splitting and beam shaping, and then emitted to irradiate the lower surface of the steel strip. It can also be transmitted to the galvanometer of the upper laser cleaning head 505 and emitted to irradiate the upper surface of the steel strip. The laser optical path is protected by a light shield 503 to prevent laser leakage and accidental damage.

[0085] The lower laser cleaning head motion module and the upper laser cleaning head motion module consist of two sets of motors, both of which are fixed to the marble column by bolts. They can drive the lower laser cleaning head 504 and the upper laser cleaning head 505 to move in the Z and X directions. Their function is to achieve the best cleaning effect when cleaning steel strips of different thicknesses by adjusting the positions of the lower laser cleaning head 504 and the upper laser cleaning head 505 as well as the laser process parameters.

[0086] The laser texturing component 6 is fixed to the marble column by bolts and fixing plates. After the steel strip is laser cleaned by the lower laser cleaning head 504 and the upper laser cleaning head 505, the laser texturing component 6 will irradiate the cleaned surface of the steel strip with the laser emitted by the ultraviolet pulse fiber laser 601 through the galvanometer scanning method, to form micro-pits and create a texturing effect, which can increase the bonding effect of the plate interface in subsequent processes.

[0087] The upper laser cleaning head 505, the lower laser cleaning head 504, and the laser texturing component 6 are respectively equipped with a first air blowing assembly 8, a second air blowing assembly 9, and a third air blowing assembly 10 near the scanning galvanometer for directionally blowing away the dust generated during processing. Compressed air is blown out towards each laser processing area through the nozzles of the first air blowing assembly 8, the second air blowing assembly 9, and the third air blowing assembly 10, respectively, directionally blowing away the peeled oxide dust from the processing position. This maintains the cleanliness of the processing area, prevents secondary dust pollution, and, in conjunction with the dust extraction system, improves the overall dust removal efficiency.

[0088] The outer casing 2 of the machine body also houses a first side dust extraction assembly 11 and a second side dust extraction assembly 12. The dust extraction port is connected to an external dust removal device via a flexible hose. Its position can be adjusted according to the blowing angle of the air blowing assembly (the blowing angle is adjustable) to facilitate the removal of a large amount of dust generated during the cleaning process. The first side dust extraction assembly 11, the first air blowing assembly 8, and the second air blowing assembly 9 are located on the left and right sides of the upper laser cleaning head 505, respectively. The first side dust extraction assembly 11 is used to extract the dust blown out by the first air blowing assembly 8 and the second air blowing assembly 9. The second side dust extraction assembly 12 and the third air blowing assembly 10 are located on the left and right sides of the scanning galvanometer of the laser texturing assembly 6, respectively. The second side dust extraction assembly 12 is used to extract the dust blown out by the third air blowing assembly 10. To address the issue of dust dispersion that can still occur with top-mounted dust extraction and air blowing alone, a first side-mounted dust extraction assembly 11 and a second side-mounted dust extraction assembly 12 were added. The first side-mounted dust extraction assembly 11, along with the first air blowing assembly 8 and the second air blowing assembly 9, are located on the left and right sides of the upper laser cleaning head 505, respectively, forming a counter-current airflow. The second side-mounted dust extraction assembly 12 and the third air blowing assembly 10 are located on the left and right sides of the scanning galvanometer of the laser texturing assembly 6, respectively. The air blowing assembly laterally blows the dust towards the opposite side-mounted dust extraction assembly, minimizing the path of dust from generation to collection and preventing dust dispersion within the cavity. This structure significantly improves the directional dust collection rate and reduces dust accumulation and maintenance frequency within the equipment.

[0089] Preferably, the first air blowing assembly 8, the second air blowing assembly 9, and the third air blowing assembly 10 are located between the scanning galvanometer of the lower laser cleaning head 504 and the laser texturing assembly 6. To avoid mutual airflow interference from multiple air blowing assemblies, the air blowing assemblies of the cleaning station and the texturing station are spatially staggered, so that each station can perform cleaning independently and the airflow will not collide with each other, thus ensuring the cleaning effect of each station.

[0090] The complete set of equipment can be directly connected to existing steel-copper composite production lines to achieve integrated operation of continuous automatic feeding of steel strip, preliminary grinding and polishing, double-sided laser cleaning, laser surface roughening, dust removal and purification, and automatic discharge. The equipment is equipped with multi-position air blowing and internal negative pressure dust extraction structure, which ensures fully enclosed dust collection, low noise and no pollution. It is suitable for continuous online processing of steel / copper thin plates of different widths and thicknesses.

[0091] The lasers are equipped with a 200W infrared continuous laser and a 100W ultraviolet nanosecond fiber laser, respectively. The infrared laser wavelength is 1064nm and the ultraviolet laser wavelength is 355nm, which can meet the different process parameter requirements for cleaning oil stains and rust on steel / copper strips and roughening the surface array micro-pits. The adjustable frequencies of the lasers are 50-10kHz and 10-100kHz, respectively.

[0092] Both the laser cleaning head and the laser texturing component 6 are equipped with 3D dynamic focusing scanning galvanometers, which can cover the width of conventional steel and copper thin plates. The dynamic focusing can adapt to the height difference on the surface of the thin plate and the slight fluctuations generated during material transmission. The spot size is fine and controllable, and it can accurately complete large-area cleaning and micro-scale dot matrix etching and texturing. The spot size after focusing by the laser cleaning head galvanometer and the laser texturing galvanometer is 0.5mm and 0.05mm, respectively.

[0093] The motion modules of the lower laser cleaning head, the upper laser cleaning head, and the scanning galvanometer of the laser texturing component 6 all adopt a servo motor linear module structure, which can realize lateral translation in the X direction and vertical adjustment in the Z direction, adapt to steel strips of different thicknesses, and quickly switch production specifications.

[0094] When performing a streamlined laser cleaning and texturing process on a 50mm wide and 1mm thick steel strip, the entire roll of steel strip is loaded onto the steel strip reel 1. The end of the steel strip is pulled through the feeding and polishing assembly 4. The front end of the feeding and polishing assembly 4 has an openable window. The positions of the upper and lower grinding wheel motors 403 are adjusted to control the spacing between the upper and lower polishing grinding wheels 401, thereby adapting to the thickness of the steel strip. The steel strip passes sequentially through the upper and lower polishing grinding wheels 401 and the hard brush at the discharge port 404 before being smoothly fed into the processing cavity inside the machine housing 2. In the initial standby state of the equipment, the top dust extraction fan 13, the dust extraction pipe 402 at the feed port, and the dust extraction pipe 702 at the discharge port are kept running throughout the process, forming an internal negative pressure sealed dust removal environment.

[0095] The steel strip is pulled forward by the production line at a uniform speed of 2m / min and fed into the feeding grinding and polishing assembly 4. The upper and lower grinding wheel motors 403 drive the upper and lower grinding and polishing wheels 401 to rotate synchronously, performing preliminary mechanical grinding and polishing on the upper and lower surfaces of the steel strip to remove large pieces of rust, thick oil stains and attached debris from the surface of the steel strip. The dust generated by grinding and polishing is sucked away by the dust extraction pipe 402 at the feed port in real time under negative pressure. Subsequently, the steel strip passes through a hard brush to brush off the loose dust and particulate debris remaining on the surface, which is simultaneously collected and processed by the feeding dust extraction system, completing the pre-treatment process.

[0096] After the roughing process of the above-mentioned feeding grinding and polishing component 4, the steel strip continues to enter the laser processing area inside the machine body shell 2 at a constant speed. The 200W infrared continuous laser is started to continuously output laser. The laser beam is collimated / expanded and shaped by the flying optical path 502, then split and passed through the line shaping module. After passing through the light shielding tube 503, it is transmitted to the galvanometers of the lower laser cleaning head 504 and the upper laser cleaning head 505 respectively. Then, after passing through the field lens, the line laser output is realized. The lower laser cleaning head 504 and the upper laser cleaning head 505 simultaneously irradiate the upper and lower surfaces of the steel strip. The process parameters are set, and the laser power is 60%. The laser power is optimized according to the cleaning effect. If residual stains are cleaned, the laser power can be increased in increments of 5%. If laser heat burns the substrate, the laser power can be decreased in increments of 5%.

[0097] The line laser scanning speed is calculated based on the size of the focused spot d1=0.5mm. Currently, the speed of the steel strip is 2m / min, which is approximately v1=33.3mm / s. The time taken for the steel strip to travel the distance of one spot is s1. Currently, the width of the steel strip is d2=50mm.

[0098] s1 = d1 / v1 ≈ 0.015s; At speed S1, the line laser scanning speed needs to cover the entire width of the steel strip for cleaning, so setting the scanning line width to 55mm is sufficient to cover the entire width of the steel strip.

[0099] v2=d2 / s1≈3667mm / s; According to the calculation, v2 = 3667 mm / s, where v2 is the minimum speed. Considering the overlap of the laser spot, the laser spot overlap can make the steel strip cleaner more uniform and thorough. Therefore, the laser scanning speed can be increased in increments of 5% based on the cleaning effect.

[0100] The laser frequency is set to 50kHz. The frequency is optimized based on the cleaning effect and thermal impact. If the heat accumulation is too high while other parameters remain unchanged, the frequency parameter can be reduced by 2%.

[0101] Defocus amount: Set to 0.1-0.3mm for positive defocus.

[0102] Based on the above-mentioned parameters, the residual oil stains, oxidation and rust on the surface of the steel strip are precisely removed without damaging the base material of the steel strip. At the same time, the air blowing component continuously sprays compressed air to blow the fine dust generated by laser processing in a directional manner toward the first side dust extraction component 11 inside the equipment. The overflowing dust will also be drawn away by the top dust extraction fan 13.

[0103] After the steel strip completes double-sided laser cleaning, it continues to be conveyed forward and enters the working area of ​​the laser texturing component 6. The 100W ultraviolet nanosecond fiber laser is started and the laser is directly transmitted to the galvanometer through the fiber. The galvanometer scans the area of ​​the steel strip to be composited and etches an array of micro-pits to form a uniform surface texturing morphology. This increases the physical contact area and bonding friction of the composite interface in the subsequent process of the steel strip, effectively preventing subsequent composite board delamination, peeling, and interlayer slip defects.

[0104] Set the process parameters as follows: laser power 50%, scanning speed 2000 mm / s, frequency 50 kHz. If the depth of the micro-pits or the roughening effect is insufficient, the laser power can be increased in increments of 5%. Since the requirements for the precision and roughness of the array micro-pits are not high, only the micro-pits need to be processed.

[0105] Throughout the laser cleaning and laser texturing process, the air blowing component continuously sprays compressed air, directing the fine dust generated by laser processing towards the first side dust extraction component 11 and the second side dust extraction component 12 inside the equipment; the top dust extraction fan 13, together with the top dust extraction fan pipe 14, forms a negative pressure in the cavity, and the dust is uniformly collected to the external dust removal equipment for filtration and treatment. The fully enclosed structure of the machine shell 2 prevents dust from overflowing and noise from spreading, achieving green and low-noise production.

[0106] After cleaning and roughening, the steel strip continues to be conveyed forward to the discharge assembly 7. The soft brush of the discharge assembly 7 removes the trace amount of residual dust on the surface, and the dust extraction pipe 702 at the discharge port simultaneously uses negative pressure to adsorb the overflowing dust. Finally, the strip is flattened and sent out of the equipment to directly connect to the subsequent copper strip composite forming process.

[0107] The entire production line operates continuously in a cycle, with the steel strip tray continuously unwinding, feeding and polishing, laser double-sided cleaning, laser precision texturing, sealed dust removal, and automatic discharge running synchronously and uninterruptedly. There is no need to set up separate cleaning stations or texturing stations, no need to add multiple separate devices, and a reduction in dedicated operators. It is compatible with existing steel / copper thin plate composite production lines for seamless integration, suitable for large-scale automated continuous production, and can be operated after simple training. It has strong versatility and significantly reduces long-term operating and maintenance costs.

[0108] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A laser cleaning and texturing method suitable for thin metal sheets, characterized in that, Includes the following steps: S1. Mechanical grinding and polishing pretreatment: Preliminary mechanical polishing is performed on the surface of the metal sheet that is continuously conveyed at a set linear speed to remove large pieces of rust, thick oil stains and attached debris from the surface of the metal sheet; S2, Online Laser Cleaning: Using an infrared continuous laser beam, the upper and lower surfaces of the pre-treated metal sheet are simultaneously irradiated in an elliptical trajectory to remove residual rust and oil stains. Among them, the infrared continuous laser beams irradiating the upper and lower surfaces of the metal sheet are staggered along the length of the metal sheet; The process parameters for infrared continuous laser are: laser power 100-200W, scanning speed 1000-4000mm / s, frequency 50-100kHz, and scanning line width greater than the width of the steel strip. S3, Online Laser Hair Resurfacing: Using an ultraviolet pulsed laser beam, an array of micro-pits is etched on the surface of the cleaned metal sheet to be composited, forming a uniform surface roughening morphology.

2. The method according to claim 1, characterized in that, In step S2, a beam of continuous infrared laser light is uniformly split into two paths through a flying optical path, which are then irradiated onto the upper and lower surfaces of the metal sheet, respectively.

3. The method according to claim 2, characterized in that, In step S2, the misalignment distance between the infrared continuous laser beams irradiating the upper and lower surfaces of the metal sheet is ≥20mm.

4. The method according to claim 3, characterized in that, In step S2, the infrared continuous laser is a nanosecond-level continuous laser and / or a picosecond-level continuous laser.

5. The method according to claim 1, characterized in that, In step S3, the ultraviolet pulsed laser is a nanosecond or picosecond pulsed laser with a wavelength of 355nm. Its process parameters are: laser power 50-100W, scanning speed 1000-3000mm / s, and frequency 10-100kHz.

6. A laser cleaning and texturing apparatus for implementing the method as described in any one of claims 1-5, characterized in that, This includes the outer casing, which forms a sealed processing cavity inside; The machine body shell is provided with a feeding grinding and polishing component, a laser cleaning component and a laser texturing component arranged sequentially from the feeding side to the discharging side; The laser cleaning assembly includes an infrared continuous laser, a flying optical path, an upper laser cleaning head, and a lower laser cleaning head. The laser emitted by the infrared continuous laser is split by the flying optical path and transmitted to the upper and lower laser cleaning heads respectively, so as to simultaneously perform laser cleaning on the upper and lower surfaces of the metal sheet. The upper and lower laser cleaning heads are arranged alternately from left to right. The top of the outer casing of the machine body is provided with a dust extraction port, and a top dust extraction fan is installed in the dust extraction port. The top dust extraction fan is connected to an external dust removal device through a dust extraction pipe.

7. The apparatus according to claim 6, characterized in that, Near the scanning galvanometers of the upper laser cleaning head, the lower laser cleaning head, and the laser texturing component, a first air blowing component, a second air blowing component, and a third air blowing component are respectively provided for directionally blowing away the dust generated during processing.

8. The apparatus according to claim 7, characterized in that, The outer casing of the machine body is also equipped with a first side dust extraction component and a second side dust extraction component. The first side dust extraction component, the first air blowing component, and the second air blowing component are respectively located on the left and right sides of the upper laser cleaning head. The first side dust extraction component is used to extract the dust blown out by the first air blowing component and the second air blowing component. The second side dust extraction component and the third air blowing component are respectively located on the left and right sides of the scanning galvanometer of the laser texturing component. The second side dust extraction component is used to extract the dust blown out by the third air blowing component. The first air blowing component, the second air blowing component, and the third air blowing component are located between the lower laser cleaning head and the scanning galvanometer of the laser texturing component.

9. The apparatus according to claim 6, characterized in that, The feeding and polishing assembly includes a first housing, which is installed inside the outer shell of the machine body on the feeding side. Inside the first housing, there are upper and lower polishing wheels arranged opposite each other with adjustable spacing. The metal sheet passes between the upper and lower polishing wheels. The upper and lower polishing wheels are respectively driven and connected to a grinding wheel motor. The grinding wheel motor is installed on the inner wall of the first housing. The side wall of the first housing has an outlet for the metal sheet to pass through.

10. The apparatus according to claim 9, characterized in that, A discharge assembly is provided inside the outer casing of the machine body near the discharge side. The discharge assembly includes a second housing, which is installed on the discharge side of the outer casing of the machine body. An inlet is provided on the side of the second housing away from the discharge side of the outer casing of the machine body. Brushes are provided at the top and bottom of the inlet of the first housing and the outlet of the second housing, respectively. Dust extraction pipes are connected inside the first housing and the second housing.

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