A non-destructive laser cleaning method and cleaning device for aluminum alloy workpiece surface

Abstract

The present invention discloses a non-destructive laser cleaning method and cleaning device for the surface of an aluminum alloy workpiece. The cleaning method includes ten steps: fixing the workpiece, determining the cleaning area, planning a flat-top laser scanning path, setting flat-top laser parameters, starting flat-top laser cleaning, planning a Gaussian laser scanning path, setting Gaussian laser parameters, starting Gaussian laser cleaning, determining the cleaning effect, and completing cleaning. The cleaning device includes a workbench with a 3D movable platform connected to a computer control system, an image acquisition device, a flat-top laser, a Gaussian laser, and a dynamic focusing optical system. Beneficial effect: Under the dual-pulse laser action of the flat-top laser and the Gaussian laser, the flat-top laser produces an effect in which the thermal elastic expansion of the paint layer and the substrate is greater than the adhesion between the two, and the Gaussian laser accurately cuts the edge of the expanded paint layer, thereby obtaining an efficient and non-destructive laser paint removal technology. A more efficient, uniform, and safe cleaning effect is achieved.

Description

Technical Field

[0001] The present invention relates to a cleaning method and a cleaning device, in particular to a non-destructive laser cleaning method and a cleaning device for the surface of an aluminum alloy workpiece, belonging to the technical field of laser cleaning. Background Art

[0002] Aluminum alloys, with their advantages of light weight and outstanding mechanical properties, are widely used in the aviation industry. To meet flight safety requirements and extend aircraft service life, aircraft require thorough surface paint removal every five to six years. Traditional removal methods are time-consuming and labor-intensive, and pose significant environmental risks. Laser cleaning technology, with its unique advantages of high efficiency, environmental friendliness, wide applicability, and high cleaning precision, is a promising paint removal method.

[0003] At present, the field of laser paint removal in the aviation industry mainly studies high-power laser cleaning devices and methods. Due to the inevitable thermal effect of the laser action process, the paint removal process can easily damage the surface of the aluminum alloy substrate. Reasonable configuration of laser process parameters can reduce the damage to the aluminum alloy substrate, but the laser cleaning efficiency cannot be guaranteed.

[0004] Chinese patent CN 118616422 A discloses a multi-wavelength laser composite cleaning device, system, and method. Lasers of different wavelengths, through an optical path composite mechanism, can be combined into a single laser beam directed at the same location on the object to be cleaned, or multiple laser beams directed at different locations on the object to be cleaned. The resulting effects are improved cleaning quality and efficiency. However, when combined into a single laser beam for cleaning, the power parameters of the different wavelengths cannot be precisely controlled, resulting in surface damage to the workpiece. Multiple laser beams directed at different locations on the object to be cleaned can result in inconsistent cleaning effects and quality. This technical solution fails to simultaneously address both cleaning quality and efficiency. Summary of the Invention

[0005] Purpose of the Invention: This invention addresses the relatively low cleaning efficiency and severe thermal damage issues inherent in existing technologies by providing a non-destructive laser cleaning method and device for aluminum alloy workpiece surfaces. Under the action of a dual-pulse laser, the flat-top laser produces a thermoelastic expansion of the paint layer and substrate that exceeds the adhesion between them. A second laser beam then precisely cuts the edges of the expanded paint layer, achieving a highly efficient, non-destructive laser paint removal technique and a more efficient, uniform, and safe cleaning effect.

[0006] Technical solution: A non-destructive laser cleaning method for the surface of an aluminum alloy workpiece, comprising the following steps:

[0007] Step 1: Fix the workpiece on the workbench with a 3D movable platform;

[0008] Step 2: Determine the cleaning area, determine the starting position for measurement and cleaning, and set the measurement parameters of the contour measurement system to match the working environment;

[0009] Step 3: Plan the flat-top laser scanning path. Plan the scanning path of the flat-top laser beam based on the size and shape of the area to be cleaned acquired in step 2, and store the starting, middle, and end coordinate parameters. The scanning path matches the shape and size of the area to be cleaned. If the area to be cleaned is square, the path adopts a square shape. If the area to be cleaned is smaller than the large spot diameter, a single large spot is used.

[0010] Step 4: Set the flat-top laser parameters according to the physicochemical properties of the paint layer, the physicochemical properties of the substrate, and the laser parameters;

[0011] Step 5: Start the flat-top laser cleaning and complete the scanning of the entire cleaning area according to the scanning path planned in step 3;

[0012] Step 6: Plan the Gaussian laser scanning path. Based on the shape formed by the flat-top laser scanning in step 3 and the image collected after the flat-top laser cleaning, plan a Gaussian laser scanning path to form a peripheral closed loop. Further correct the Gaussian laser scanning path by collecting the image after the flat-top laser cleaning.

[0013] Step 7: Setting Gaussian laser parameters: Setting Gaussian laser parameters according to the physicochemical properties of the paint layer, the physicochemical properties of the substrate, and the laser parameters;

[0014] Step 8: Start the Gaussian laser for cleaning. Start the Gaussian laser to complete the scanning of the entire cleaning area according to the scanning path planned in step 6.

[0015] Step 9: Determine the cleaning effect. If the test result shows that there is still a residual paint layer on the surface of the workpiece, the system will restart from step 2 until the cleaning effect meets the set requirements; if the test result shows that the workpiece surface meets the cleaning requirements, it will proceed to step 10;

[0016] Step 10: After cleaning is completed, shut down and maintain the laser cleaning device.

[0017] The present invention can achieve non-destructive high-quality cleaning. Through the flat-top laser beam emitted by the flat-top laser and the Gaussian laser beam emitted by the Gaussian laser, according to the combination of force effect and thermal effect, the paint layer expands and bulges after the flat-top laser beam performs preliminary treatment on the surface of the workpiece, and the Gaussian laser beam accurately cuts the paint layer on the surface of the workpiece, and finally the surface paint layer falls off directly. Compared with the traditional single-beam laser cleaning device, the cleaning quality is significantly improved. The flat-top laser beam emitted by the flat-top laser in the present invention has a uniform distribution of the energy of the flat-top laser beam on the surface of the workpiece, making the cleaning process more uniform and effectively avoiding the phenomenon of incomplete cleaning or local over-cleaning. The present invention greatly improves the efficiency of laser cleaning through the combination of rapid laser endothermic expansion and edge cutting. The performance requirements of the two lasers used are not high, and compared with the single-beam laser paint removal that requires high energy and high power lasers, the cost of the equipment is greatly reduced.

[0018] Preferably, in order to separate the paint layer from the aluminum alloy while avoiding thermal damage to the aluminum alloy substrate, the flat-top laser emits a flat-top beam, the spot of the flat-top beam is a large spot, and the diameter of the large spot ranges from 50um to 5cm;

[0019] The flat-top laser parameter in step 4 is the flat-top laser energy density W1, which is calculated as follows:

[0020]

[0021] Where W1 is the flat-top laser energy density of the flat-top laser, K is the thermal conductivity, δ is the reflectivity of the material to the laser, τ is the pulse width, α is the thermal diffusivity, d is the distance between the two parallel planes of the primer and the substrate, and H 12 is the Hamaker coefficient of the contact between the substrate and the paint layer, with the unit of N·m, σ is the thermal expansion coefficient of the paint layer, with the unit of 1 / °C or 1 / °F, and E is the Young's modulus of elasticity of the paint layer, with the unit of Pascal or psi.

[0022] After the large laser spot energy is absorbed by the paint layer, the thermal effect of the flat-top laser causes the paint layer to expand or bulge due to the different physical and chemical properties of the aluminum alloy and the paint layer, significantly weakening the connection between the paint layer and the substrate. Because the melting point of the aluminum alloy substrate is much higher than the set laser temperature, thermal damage to the aluminum alloy substrate is avoided.

[0023] The flat-top laser utilizes a large flat-top beam spot because its energy distribution is relatively uniform, ensuring consistent energy density over a large area. The laser energy is rapidly absorbed by the surface material, resulting in a low laser energy density. The temperature at this point is insufficient to melt the surface paint layer, but it merely induces expansion or bubbling. Therefore, the mechanism is not traditional ablation or vaporization. The large flat-top beam spot provides a relatively uniform low energy density over a large area, enabling physical separation and delamination of the paint layer over a wide area. This gentle force effect pushes away or expands the entire paint layer.

[0024] Preferably, in order to precisely control the laser energy density of the flat-top laser to achieve separation of the paint layer from the aluminum alloy while avoiding thermal damage to the aluminum alloy substrate, the laser energy density of the flat-top laser is less than the laser removal threshold of the paint layer and less than the laser damage threshold of the aluminum alloy.

[0025] Preferably, in order to improve the cleaning efficiency, the scanning path of the flat-top laser is planned in step 3 as a single spot or a scanning superimposed spot; the spot size and scanning mode are set according to the shape and size of the area to be cleaned;

[0026] When the area to be cleaned is large, the spot diameter is 50um-1cm, and a scanning beam is used to form a large spot. The scanning method is "bow" or "spiral" or other scanning methods. When the diameter of the area to be cleaned is less than 5cm and relatively dispersed, a spot diameter of 1cm-5cm is used, and a single beam is used to form a large spot.

[0027] Preferably, in order to improve efficiency while avoiding affecting cleaning quality, the superposition rate of the scanning superimposed light spots is -20%<η1<10%.

[0028] Preferably, to achieve efficient and non-destructive paint removal, the Gaussian laser emits a small Gaussian beam with a spot diameter ranging from 1 μm to 50 μm. This is because the energy distribution of a Gaussian beam is strongest at the center and decreases as it moves away from the center. A small spot can concentrate the laser energy into a very small area, generating extremely high laser energy density. After the laser is absorbed, the surface temperature of the paint layer rises, exceeding the vaporization temperature of the paint layer, causing the edges of the paint layer to be cut, resulting in rapid peeling of the paint layer over a large area, achieving efficient and non-destructive paint removal.

[0029] The Gaussian laser parameter in step 7 is the Gaussian laser energy density W2, which is calculated as follows:

[0030]

[0031] Among them, T s is the vaporization temperature of the paint layer, K is the thermal conductivity, α is the thermal diffusivity, δ is the reflectivity of the material to the laser, and τ is the pulse width.

[0032] Preferably, in order to precisely control the laser energy density of the Gaussian laser to achieve separation of the paint layer from the aluminum alloy while avoiding thermal damage to the aluminum alloy substrate, the laser energy density of the Gaussian laser is greater than the laser removal threshold of the paint layer but less than the laser damage threshold of the aluminum alloy.

[0033] Preferably, in order to improve efficiency while avoiding affecting the cleaning quality, when planning the Gaussian laser scanning path in step six, the laser beam scanning path of the Gaussian laser covers the outer edge of the laser beam of the flat-top laser, and the superposition rate of the scanning superimposed light spots is 0.1%<η2<30%.

[0034] There are many ways to combine the two laser beams. The contour scanned by the flat-top laser on the material surface can be square, rectangular, circular, etc., which is specifically set according to the shape and size of the area to be cleaned. The Gaussian laser acting on the material surface scans along the edge of the contour scanned by the flat-top laser, and is corrected in combination with the collected contour image scanned by the flat-top laser to cover the edge of the flat-top laser contour.

[0035] The scanning path of the flat-top laser is in the shape of a "bow", forming a filled square figure. The scanning starting point of the Gaussian laser is the same as that of the flat-top laser. The path scans clockwise or counterclockwise along the edge of the square figure to form a closed "mouth" shape.

[0036] A non-destructive laser cleaning device for aluminum alloy workpiece surfaces, comprising a computer control system, a workbench with a 3D movable platform, an image acquisition device, a flat-top laser, a Gaussian laser, and a dynamic focusing optical system, wherein the computer control system is respectively connected to the workbench with a 3D movable platform, the image acquisition device, the flat-top laser, the Gaussian laser, and the dynamic focusing optical system by signal;

[0037] The dynamic focusing optical system includes a flat-top laser scanning galvanometer, a Gaussian laser scanning galvanometer, a beam combiner and an adjustable focusing lens system;

[0038] The flat-top laser emitted by the flat-top laser is focused onto the workpiece surface through a flat-top laser scanning galvanometer, a beam combiner and an adjustable focusing lens system in sequence;

[0039] The Gaussian laser emitted by the Gaussian laser is sequentially focused onto the workpiece surface by a Gaussian laser scanning galvanometer, a beam combiner and an adjustable focusing lens system;

[0040] The adjustable focusing lens adjusts the focal length of the laser beam, precisely focusing the laser energy onto the workpiece surface for efficient laser cleaning. The flat-top laser scanning galvanometer, Gaussian laser scanning galvanometer, and beam combiner rapidly shift the laser beam path, enabling high-speed, high-precision laser scanning on the workpiece surface, ensuring uniform cleaning and treatment.

[0041] The workpiece to be cleaned is fixed on a workbench with a 3D movable platform, and the movement of the workbench enables the setting of the cleaning trajectory;

[0042] The worktable of the 3D movable platform is adapted to move in the X, Y, and Z directions to ensure precise alignment of the workpiece surface with the laser beam output by the laser. The pulsed laser is coupled to the worktable of the 3D movable platform. The worktable of the 3D movable platform is controlled by a computer control system and has a movement accuracy of 5μm.

[0043] The image acquisition device acquires images of the size and shape of the area to be cleaned on the surface of the workpiece and the cleaning effect and feeds them back to the computer control system.

[0044] The shooting direction of the image acquisition device is consistent with the irradiation direction of the pulse laser, so as to acquire the image of the workpiece located on the workbench of the 3D mobile platform.

[0045] To avoid environmental pollution, the system further includes a dust collection device, which is connected to a computer control system and activated simultaneously with the flat-top laser and the Gaussian laser. The dust collection device of the present invention is activated synchronously with the laser cleaning process, effectively removing stripped coatings or contaminants in real time. It also prevents secondary contamination through a high-efficiency filter, maintaining a clean working environment and meeting environmental protection requirements.

[0046] Beneficial effects: Under the dual-pulse laser action of the flat-top laser and the Gaussian laser, the flat-top laser produces an effect in which the thermal elastic expansion of the paint layer and the substrate is greater than the adhesion between the two, and the Gaussian laser accurately cuts the edge of the expanded paint layer, thereby obtaining a highly efficient and non-destructive laser paint removal technology. The device and method proposed in the present invention overcome the limitations of single-beam laser paint removal and achieve a more efficient, uniform and safe cleaning effect. The energy of the laser used in the present invention is much lower than the energy requirement of the existing single-beam laser paint removal, which is beneficial to reducing costs. The dust suction device of the present invention is started synchronously with the laser cleaning process, and can remove the peeled coating or pollutants in real time, and prevent secondary pollution through a high-efficiency filter, so as to keep the working environment clean and meet environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0048] Figure 1 is a flow chart of the cleaning method of the present invention;

[0049] Figure 2 It is a structural schematic diagram of the cleaning device of the present invention;

[0050] Figure 3 This is a schematic diagram of the laser cleaning path of the present invention Figure 1 ;

[0051] Figure 4 This is a schematic diagram of the laser cleaning path of the present invention Figure 2 ;

[0052] Figure 5 This is a schematic diagram of the laser cleaning path of the present invention Figure 3 ;

[0053] Figure 6 This is a schematic diagram of the laser cleaning path of the present invention Figure 4 ;

[0054] Figure 7 This is a scanning electron microscope image of the laser cleaning effect of the present invention. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0057] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0058] like Figure 1 and 2 As shown, a non-destructive laser cleaning method for the surface of an aluminum alloy workpiece includes the following steps:

[0059] Step 1: Secure the aluminum alloy workpiece to be cleaned on a 3D movable workbench 2 to ensure a smooth surface. Activate image acquisition device 3 to capture an image of the aluminum alloy workpiece's surface. Image acquisition device 3 transmits the image to computer control system 1 for storage.

[0060] Step 2: Determine the cleaning area, determine the starting position for measurement and cleaning, and set the measurement parameters of the contour measurement system to match the working environment;

[0061] Step 3: Plan the flat-top laser scanning path. Plan the scanning path of the flat-top laser beam based on the size and shape of the area to be cleaned acquired in step 2, and store the starting, middle, and end coordinate parameters. The scanning path matches the shape and size of the area to be cleaned. If the area to be cleaned is square, the path adopts a square shape. If the area to be cleaned is smaller than the large spot diameter, a single large spot is used.

[0062] like Figure 3-6 As shown, in order to improve the cleaning efficiency, the scanning path of the flat-top laser is planned in step 3 as a single spot or a scanning superimposed spot; the spot size and scanning mode are set according to the shape and size of the area to be cleaned;

[0063] When the area to be cleaned is large, the spot diameter is 50um-1cm, and a scanning beam is used to form a large spot. The scanning method is "bow" or "spiral" or other scanning methods. When the diameter of the area to be cleaned is less than 5cm and relatively dispersed, a spot diameter of 1cm-5cm is used, and a single beam is used to form a large spot.

[0064] Step 4: Set the flat-top laser parameters according to the physicochemical properties of the paint layer, the physicochemical properties of the substrate, and the laser parameters;

[0065] In order to separate the paint layer from the aluminum alloy while avoiding thermal damage to the aluminum alloy substrate, the flat-top laser emits a flat-top beam with a large spot size, and the diameter of the large spot ranges from 50 μm to 5 cm.

[0066]

[0067] Where W1 is the flat-top laser energy density of the flat-top laser, K is the thermal conductivity, δ is the reflectivity of the material to the laser, τ is the pulse width, α is the thermal diffusivity, d is the distance between the two parallel planes of the primer and the substrate, and H 12is the Hamaker coefficient of the contact between the substrate and the paint layer, with the unit of N·m, σ is the thermal expansion coefficient of the paint layer, with the unit of 1 / °C or 1 / °F, and E is the Young's modulus of elasticity of the paint layer, with the unit of Pascal or psi.

[0068] Calculations show that when the flat-top laser energy density is 4.456 J / cm2, the surface will expand or bulge. When the flat-top laser energy density is greater than 4.456 J / cm2, the surface primer will be ablated and vaporized.

[0069] The flattened laser parameters of flattened laser 4 are set to: flattened laser energy density of 3.819 J / cm²-4.456 J / cm², scanning speed of 1500 mm / s-2000 mm / s, and frequency of 80 kHz-100 kHz (a pulsed laser with a laser power parameter range of 0 W-100 W is selected). To protect the aluminum alloy substrate, the computer control system 1 ensures that the laser parameters are within a safe range to avoid damage to the substrate. Simultaneously, the adjustable focusing lens system 64 in the dynamic focusing optical system accurately positions the laser beam focus on the paint layer on the aluminum alloy surface.

[0070] The flattened laser beam from flattened laser 4 is activated, and computer control system 1 instructs worktable 2, a 3D movable platform, to move the aluminum alloy workpiece under the laser beam. The flattened laser beam causes the paint layer's surface to rapidly expand due to heat, causing bulging or loosening, thereby reducing the bond strength between the paint layer and the aluminum alloy substrate.

[0071] After the large laser spot energy is absorbed by the paint layer, the thermal effect of the flat-top laser causes the paint layer to expand or bulge due to the different physical and chemical properties of the aluminum alloy and the paint layer, significantly weakening the connection between the paint layer and the substrate. Since the melting point of the aluminum alloy substrate is much higher than the temperature generated by the laser, thermal damage to the aluminum alloy substrate is avoided.

[0072] The flat-top laser 4 uses a large flat-top spot because its energy distribution is relatively uniform, ensuring consistent energy density over a large area. The laser energy is rapidly absorbed by the surface material, resulting in a low laser energy density. The temperature at this point is insufficient to melt the surface paint layer, but it merely induces expansion or bubbling. Therefore, the mechanism is not traditional ablation or vaporization. The large flat-top laser beam provides a relatively uniform low energy density over a large area, enabling physical separation and debonding of the paint layer over a wide area. This gentle force effect pushes away or expands the entire paint layer.

[0073] In order to precisely control the laser energy density of the flat-top laser 4 to achieve separation of the paint layer from the aluminum alloy while avoiding thermal damage to the aluminum alloy substrate, the laser energy density of the flat-top laser 4 is less than the laser removal threshold of the paint layer and less than the laser damage threshold of the aluminum alloy.

[0074] In order to improve efficiency while avoiding affecting cleaning quality, the superposition rate of the scanning superimposed light spots is -20%<η1<10%.

[0075] Step 5: Start the flat-top laser cleaning and complete the scanning of the entire cleaning area according to the scanning path planned in step 3;

[0076] Step 6: Plan the scanning path of the Gaussian laser 5. Plan a Gaussian laser 5 scanning path with a peripheral closed loop based on the shape formed by the flat-top laser scanning in step 3 and the image collected after the flat-top laser 4 is cleaned. Further correct the scanning path of the Gaussian laser 5 by collecting the image after the flat-top laser 4 is cleaned.

[0077] like Figure 3-6 As shown, in order to improve efficiency while avoiding affecting the cleaning quality, when planning the scanning path of the Gaussian laser 5 in step six, the laser beam scanning path of the Gaussian laser 5 covers the outer edge of the laser beam of the flat-top laser 4, and the superposition rate of the scanning superimposed light spots is 0.1%<η2<30%.

[0078] Step 7: Set the parameters of the Gaussian laser 5 according to the physicochemical properties of the paint layer, the physicochemical properties of the substrate and the laser parameters;

[0079] To achieve efficient and non-destructive paint removal, the Gaussian laser emits a small Gaussian beam with a spot diameter ranging from 1µm to 50µm. This is because the energy distribution of a Gaussian beam is strongest at the center and decreases as it moves away from the center. This small spot concentrates the laser energy into a very small area, generating extremely high laser energy density. When the laser is absorbed, the surface temperature of the paint layer rises, exceeding its vaporization temperature. This causes the edges of the paint to be cut, rapidly stripping the paint over a large area, achieving efficient and non-destructive paint removal.

[0080] The parameter of the Gaussian laser 5 in step 7 is the Gaussian laser energy density W2, which is calculated as follows:

[0081]

[0082] Among them, T s is the vaporization temperature of the paint layer, K is the thermal conductivity, α is the thermal diffusivity, δ is the reflectivity of the material to the laser, and τ is the pulse width.

[0083] After the initial treatment is complete, computer control system 1 restarts Gaussian laser 5 with parameters such as energy density of 9.549J / cm²-11.459J / cm², scanning speed of 1200mm / s-2000mm / s, and frequency of 80kHz-100kHz. It also controls worktable 2, a 3D movable platform, to move the aluminum alloy workpiece into the flat-top laser irradiation area. The Gaussian laser precisely cuts and strips the loosened paint edges, ensuring complete removal from the aluminum alloy surface while minimizing damage to the substrate. Gaussian laser scanning galvanometer 62 ensures precise removal of the paint edges.

[0084] In order to precisely control the laser energy density of the Gaussian laser 5 to achieve separation of the paint layer from the aluminum alloy while avoiding thermal damage to the aluminum alloy substrate, the laser energy density of the Gaussian laser 5 is greater than the laser removal threshold of the paint layer but less than the laser damage threshold of the aluminum alloy.

[0085] Step 8: Start the Gaussian laser 5 for cleaning. Start the Gaussian laser 5 to complete the scanning of the entire cleaning area according to the scanning path planned in step 6.

[0086] Step 9: Determine the cleaning effect. If the test result shows that there is still a residual paint layer on the surface of the workpiece, the system will restart from step 2 until the cleaning effect meets the set requirements; if the test result shows that the workpiece surface meets the cleaning requirements, it will proceed to step 10;

[0087] Step 10: After cleaning is completed, shut down and maintain the laser cleaning device.

[0088] The present invention can achieve non-destructive high-quality cleaning. Through the flat-top laser beam emitted by the flat-top laser and the Gaussian laser beam emitted by the Gaussian laser, according to the combination of force effect and thermal effect, the paint layer expands and bulges after the flat-top laser beam performs preliminary treatment on the surface of the workpiece, and the Gaussian laser beam accurately cuts the paint layer on the surface of the workpiece, and finally the surface paint layer falls off directly. Compared with the traditional single-beam laser cleaning device, the cleaning quality is significantly improved. The flat-top laser beam emitted by the flat-top laser in the present invention has a uniform distribution of the energy of the flat-top laser beam on the surface of the workpiece, making the cleaning process more uniform and effectively avoiding the phenomenon of incomplete cleaning or local over-cleaning. The present invention greatly improves the efficiency of laser cleaning through the combination of rapid laser endothermic expansion and edge cutting. The performance requirements of the two lasers used are not high, and compared with the single-beam laser paint removal that requires high energy and high power lasers, the cost of the equipment is greatly reduced.

[0089] like Figure 2As shown, a non-destructive laser cleaning device for the surface of an aluminum alloy workpiece includes a computer control system 1, a workbench 2 with a 3D movable platform, an image acquisition device 3, a flat-top laser 4, a Gaussian laser 5, and a dynamic focusing optical system 6. The computer control system 1 is signal-connected to the workbench 2 with a 3D movable platform, the image acquisition device 3, the flat-top laser 4, the Gaussian laser 5, and the dynamic focusing optical system 6 respectively;

[0090] The dynamic focusing optical system 6 includes a flat-top laser scanning galvanometer 61, a Gaussian laser scanning galvanometer 62, a beam combiner 63 and an adjustable focusing lens system 64;

[0091] The function of the adjustable focusing lens 64 is to adjust the focal length of the laser beam so that the laser energy can be accurately focused on the surface of the workpiece to achieve an efficient laser cleaning effect.

[0092] The flat-top laser emitted by the flat-top laser 4 is focused onto the workpiece surface through the flat-top laser scanning galvanometer 61, the beam combiner 63 and the adjustable focusing lens system 64 in sequence;

[0093] The Gaussian laser emitted by the Gaussian laser 5 is focused onto the workpiece surface through the Gaussian laser scanning galvanometer 62, the beam combiner 63 and the adjustable focusing lens system 64 in sequence;

[0094] The function of the flat-top laser scanning galvanometer 61, Gaussian laser scanning galvanometer 62 and beam combiner 63 is to quickly move the path of the laser beam, thereby achieving high-speed and high-precision laser scanning on the surface of the workpiece to ensure uniform cleaning and processing.

[0095] The workpiece to be cleaned is fixed to a worktable 2 with a 3D movable platform. The movement of the worktable 2 establishes the cleaning trajectory. The worktable 2 is adapted to move in the X, Y, and Z directions to ensure precise alignment of the workpiece surface with the laser beam output by the laser. The pulsed laser cooperates with the worktable 2 on the 3D movable platform. The worktable 2 is controlled by a computer control system 1, with a movement accuracy of 5μm.

[0096] The image acquisition device 3 captures images of the size and shape of the area to be cleaned on the workpiece surface, as well as the cleaning effect, and feeds them back to the computer control system 1. The shooting direction of the image acquisition device 3 is consistent with the irradiation direction of the pulsed laser, so as to capture images of the workpiece located on the workbench 2 of the 3D mobile platform.

[0097] The cleaning system further includes a dust collecting device 7, which is connected to the computer control system 1 and is activated simultaneously with the flat-top laser 4 and the Gaussian laser 5. The dust collecting device 7 is activated synchronously during the cleaning process to ensure that the stripped coating or contaminants are immediately removed to prevent secondary contamination.

[0098] like Figure 3 As shown, in this embodiment, Figure 3 (a) is the large spot scanning path of the first flat-top laser beam of the flat-top laser 4. The first flat-top light beam relies on a large spot with a large area and uniform energy distribution (diameter range of 1mm-5mm) based on the force effect to cause the paint layer to expand or bubble. The "bow" shape can effectively reduce the superposition of heat, so that the material can be heated more evenly and reduce thermal damage. Figure 3 (b) is the small spot scanning path of the second Gaussian laser emitted by the Gaussian laser 5. The second Gaussian light needs to concentrate energy into a small spot (diameter range of 0.2mm-0.5mm) according to the thermal effect, and realizes the cutting of the material through high-temperature melting or gasification. The starting point of the cleaning path of the first flat-top light and the second Gaussian light is the same.

[0099] like Figure 4 As shown, in this embodiment, Figure 4 (a) is the large spot scanning path of the first flat-top laser beam emitted by the flat-top laser 4. The large spot of the first flat-top laser beam is rectangular (side length range is 1m-5mm), and the scanning path is in the shape of a "bow", which can effectively reduce thermal damage; Figure 4 (b) is the small spot scanning path of the second Gaussian laser emitted by the Gaussian laser 5. The second Gaussian light needs to concentrate energy into a small spot (diameter range of 0.2mm-0.5mm) according to the thermal effect, and realizes the cutting of the material through high-temperature melting or gasification. The starting point of the cleaning path of the first flat-top light and the second Gaussian light is the same.

[0100] like Figure 5 As shown, in this embodiment, Figure 5 (a) is the scanning path of a large spot (diameter range 0.2mm-0.5mm) of the first flat-top light beam emitted by the flat-top laser 4, and the spiral scanning path can reduce repeated ablation and effectively avoid ineffective movement of the laser beam; Figure 5 (b) is the scanning path of the second Gaussian light beam emitted by the Gaussian laser 5. The second Gaussian light beam needs to concentrate energy into a small spot (diameter range of 0.2mm-0.5mm) according to the thermal effect, and realizes the cutting of the material through high-temperature melting or vaporization. The cleaning path of the second Gaussian light beam is along the edge of the large spot of the first flat-top light beam.

[0101] like Figure 6 As shown, in this example, Figure 6 (a) is the large spot of the first flat-top laser of the flat-top laser 4. When the diameter of the area to be cleaned is less than 5 cm and is relatively dispersed, a single beam with a large spot diameter of 1 cm-5 cm is used. Figure 6(b) is the small spot scanning path of the second Gaussian laser emitted by the Gaussian laser. The direct range of the small spot is 0.2mm-0.5mm. The cleaning path of the second Gaussian light is along the edge of the large spot of the first flat-top light.

[0102] like Figure 7 As shown, in this embodiment, the laser energy density of the second Gaussian laser emitted by the fixed Gaussian laser 5 is 11.459 J / cm2, the frequency is 100 kHz, and the scanning speed is 1500 mm / s. The frequency of the first Gaussian laser emitted by the fixed flat-top laser 4 is 100 kHz, and the scanning speed is 1500 mm / s. Figure 7 These are scanning electron micrographs at different laser energy densities. The leftmost SEM image shows a flat-top laser energy density of 3.183 J / cm², indicating slight melting of the paint layer on the aluminum alloy surface. However, due to insufficient energy density, the aluminum alloy was not completely cleaned due to insufficient expansion and bulging. The middle SEM image shows a flat-top laser energy density of 3.565 J / cm², indicating a relatively smooth surface with a visible cleaning path and only a small amount of contaminants. This indicates optimal cleaning results. The rightmost SEM image shows a flat-top laser energy density of 4.074 J / cm², indicating excessive cleaning due to excessively high laser energy density, indicating surface blackening and damage to the substrate.

[0103] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0104] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A non-destructive laser cleaning method for the surface of an aluminum alloy workpiece, characterized in that: The following steps are involved: Step 1: Fix the workpiece on the workbench with a 3D movable platform; Step 2: Determine the cleaning area, determine the starting position for measurement and cleaning, and set the measurement parameters of the contour measurement system to match the working environment; Step 3: Plan the flat-top laser scanning path. Plan the scanning path of the flat-top laser beam according to the size and shape of the area to be cleaned acquired in step 2, and store the starting, middle and end point coordinate parameters. Step 4: Set the flat-top laser parameters according to the physicochemical properties of the paint layer, the physicochemical properties of the substrate, and the laser parameters; The flat-top laser parameter is the flat-top laser energy density W1, where W1 is less than the laser removal threshold of the paint layer and less than the laser damage threshold of the aluminum alloy; Step 5: Start the flat-top laser cleaning and complete the scanning of the entire cleaning area according to the scanning path planned in step 3; Step 6: Plan the Gaussian laser scanning path. According to the shape formed by the flat-top laser scanning in step 3 and the image collected after the flat-top laser cleaning, plan the Gaussian laser scanning path to form a peripheral closed loop. When planning the Gaussian laser scanning path in step 6, the laser beam scanning path of the Gaussian laser covers the outer edge of the laser beam of the flat-top laser, and the superposition rate of the scanning superimposed light spots is 0.1%<η2<30%; Step 7: Setting Gaussian laser parameters: Setting Gaussian laser parameters according to the physicochemical properties of the paint layer, the physicochemical properties of the substrate, and the laser parameters; The Gaussian laser parameter is the Gaussian laser energy density W2, where W2 is greater than the laser removal threshold of the paint layer but less than the laser damage threshold of the aluminum alloy; Step 8: Start the Gaussian laser for cleaning. Start the Gaussian laser to scan the entire cleaning area according to the scanning path planned in step 6. Step 9: Determine the cleaning effect. If the test result shows that there is still a residual paint layer on the surface of the workpiece, restart from step 2 until the cleaning effect meets the set requirements; if the test result shows that the workpiece surface meets the cleaning requirements, proceed to step 10; Step 10: After cleaning is completed, shut down and maintain the laser cleaning device.

2. The non-destructive laser cleaning method for the surface of an aluminum alloy workpiece according to claim 1, characterized in that: The flat-top laser emits a flat-top beam, the spot of the flat-top beam is a large spot, and the diameter of the large spot ranges from 50um to 5cm; The calculation method of the flattened laser energy density W1 in step 4 is as follows: ； Where W1 is the flat-top laser energy density of the flat-top laser, K is the thermal conductivity, δ is the reflectivity of the material to the laser, τ is the pulse width, α is the thermal diffusivity, d is the distance between the two parallel planes of the primer and the substrate, and H 12 is the Hamaker coefficient of the contact between the substrate and the paint layer, with the unit of N∙m, σ is the thermal expansion coefficient of the paint layer, with the unit of 1 / °C or 1 / °F, and E is the Young's modulus of elasticity of the paint layer, with the unit of Pascal or psi.

3. The non-destructive laser cleaning method for the surface of an aluminum alloy workpiece according to claim 1, wherein: In step 3, the scanning path of the flat-top laser is planned to be a single spot; When the spot diameter is 50um-1cm, a scanning beam method is used to form a large spot, and the scanning method is "bow" or "spiral"; when the spot diameter is 1cm-5cm, a single beam large spot is used.

4. The non-destructive laser cleaning method for the surface of an aluminum alloy workpiece according to claim 1, wherein: In the step 3, the scanning path of the flat-top laser is planned to be a scanning superimposed light spot; The superposition rate of the scanning superimposed light spots is -20%<η1<10%.

5. The non-destructive laser cleaning method for the surface of an aluminum alloy workpiece according to claim 1, characterized in that: The Gaussian laser emits a Gaussian beam, the spot of the Gaussian beam is a small spot, and the diameter of the spot ranges from 1um to 50um. The Gaussian laser energy density W2 in step 7 is calculated as follows: ； Among them, T s is the vaporization temperature of the paint layer, K is the thermal conductivity, α is the thermal diffusivity, δ is the reflectivity of the material to the laser, and τ is the pulse width.

6. A cleaning device for implementing the non-destructive laser cleaning method for the surface of an aluminum alloy workpiece according to claim 1, characterized in that: The system comprises a computer control system (1), a workbench (2) with a 3D movable platform, an image acquisition device (3), a flat-top laser (4), a Gaussian laser (5), and a dynamic focusing optical system (6), wherein the computer control system (1) is respectively connected to the workbench (2) with a 3D movable platform, the image acquisition device (3), the flat-top laser (4), the Gaussian laser (5), and the dynamic focusing optical system (6) by signals; The dynamic focusing optical system (6) includes a flat-top laser scanning galvanometer (61), a Gaussian laser scanning galvanometer (62), a beam combiner (63), and an adjustable focusing lens system (64); The flat-top laser emitted by the flat-top laser (4) is focused onto the workpiece surface through a flat-top laser scanning galvanometer (61), a beam combiner (63), and an adjustable focusing lens system (64) in sequence; The Gaussian laser emitted by the Gaussian laser (5) is focused onto the workpiece surface through the Gaussian laser scanning galvanometer (62), the beam combiner (63) and the adjustable focusing lens system (64) in sequence; The workpiece to be cleaned is fixed on a workbench (2) which is a 3D movable platform, and the workbench (2) moves to achieve the setting of the cleaning trajectory; The image acquisition device (3) acquires images of the size and shape of the area to be cleaned on the surface of the workpiece and the cleaning effect and feeds them back to the computer control system (1).

7. The cleaning device for the non-destructive laser cleaning method for the surface of an aluminum alloy workpiece according to claim 6, characterized in that: It also includes a dust suction device (7), which is connected to the computer control system (1) for control, and the dust suction device (7) is turned on simultaneously with the flat-top laser (4) and the Gaussian laser (5).

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