Surface cleaning method for large complex magnesium alloy structural part formed by electric arc additive manufacturing

Abstract

The invention discloses a surface cleaning method for a large complex magnesium alloy structural part formed through electric arc additive manufacturing, and belongs to the field of post-treatment of formed structural parts after electric arc additive manufacturing. The method comprises the following steps that a mechanical arm is adopted to drive a special wire brush to conduct preliminary mechanical cleaning, and flexible contact is achieved through a mechanical sensor and a floating clamp; acidic cleaning liquid is sprayed to the surface of the workpiece through an ultrasonic spraying system, the surface color change is monitored in real time through a high-speed camera so as to control the reaction endpoint, and flushing and drying are conducted in time; and finally, carrying out fine cleaning under the protection of argon by adopting large-light-spot laser with low power density, and monitoring in real time through a spectrograph to ensure the cleaning effect. According to the method, the oxide layer and the pollutants on the surface of the large complex component can be efficiently, losslessly and automatically removed, the problem that the magnesium alloy WAAM component is difficult to clean due to high chemical activity and complex structure is solved, and the whole process is environmentally friendly and controllable.

Description

A surface cleaning method for large and complex magnesium alloy structural parts formed by electric arc additive manufacturing. Technical Field

[0001] This invention belongs to the field of post-processing of shaped structural parts after arc additive manufacturing, and specifically relates to a surface cleaning method for large and complex magnesium alloy structural parts formed by arc additive manufacturing (WAAM). Background Technology

[0002] Wire arc additive manufacturing (WAAM) is one of the most widely used technologies in additive manufacturing, frequently applied in aerospace, military, and transportation industries. Compared to other additive manufacturing technologies, WAAM uses wire as its raw material, offering advantages such as high processing speed and low cost. However, when using magnesium alloys as raw materials, the high-temperature arc during the WAAM process causes MgO dust and slag to form on the surface of the magnesium alloy structural parts. Furthermore, the formed structural parts often exhibit geometric features such as grooves and pores, leading to a decline in overall structural performance. Therefore, timely selection of appropriate surface cleaning methods after WAAM formation can help improve the overall performance of the structural parts.

[0003] However, there is currently a lack of surface cleaning methods for large and complex magnesium alloy structural parts formed by arc additive manufacturing. Patent CN118256923A discloses a surface cleaning method for hot-stamped aluminum alloy products, suitable for cleaning large and complex aluminum alloy structural parts, but the electrolyte solution used in the cleaning process causes severe corrosion to the magnesium alloy structural parts, making it unsuitable for magnesium alloy materials. Patent CN102978636A discloses a cleaning method for the surface coating of waste magnesium alloy, using a strongly alkaline mixed solution to clean organic contaminants adhering to the surface of magnesium alloy structural parts, but this method requires immersing the entire structural part in the cleaning solution, making it unsuitable for large parts with complex structures. Patent CN109433745A uses a long focal depth laser to clean the surface of structural parts, suitable for large and complex curved steel structural parts, but due to the high chemical reactivity of magnesium alloys, the heat generated by laser irradiation may cause the magnesium alloy to melt or oxidize, making it unsuitable for magnesium alloy structural parts.

[0004] Therefore, there is an urgent need for a surface cleaning method for large and complex magnesium alloy structural parts formed by electric arc additive manufacturing, and this invention is proposed. Summary of the Invention

[0005] To fill the gap in surface cleaning of large and complex magnesium alloy structural parts formed by arc additive manufacturing, this invention provides a method for surface cleaning of such parts. The cleaning method of this invention does not damage the magnesium alloy structural parts and can thoroughly clean large magnesium alloy structural parts with complex structures.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A surface cleaning method for large and complex magnesium alloy structural parts formed by arc additive manufacturing, comprising the following steps: Step 1: Fix the large and complex magnesium alloy structural part to be cleaned on a worktable, and use a robotic arm with a special wire brush at the end to perform preliminary cleaning on the surface of the structural part according to a preset path to initially remove the oxide film on the surface of the structural part; Step 2: Use a robotic arm equipped with an ultrasonic spray system to spray a special acidic cleaning solution onto the surface of the structural part after preliminary cleaning, and use a high-speed camera to monitor in real time. Once the surface of the structural part is found to be cleaned, it is immediately rinsed and dried; Step 3: Use a robotic arm equipped with a laser cleaning system to perform a third cleaning on the structural part to remove the residual acidic cleaning solution and remaining contaminants on the surface of the structural part.

[0007] Preferably, in step 1, the special wire brush is a special stainless steel wire brush with an aluminum-plated surface, in order to avoid damaging the surface of the magnesium alloy structural parts or forming a microcouple effect.

[0008] Furthermore, in step 1, the special brush is 10 cm long and 5 cm in diameter, composed of stainless steel filaments with a diameter of 0.05-0.15 mm. The filament material is 304 stainless steel, and the filament density is 20-30 clusters / square centimeter. The surface of the filaments is electroplated with an aluminum layer with a thickness of 5-15 μm. This aluminum layer is firmly bonded to the stainless steel substrate and has no visible pores.

[0009] Preferably, the wire brush is mounted at the end of the robotic arm via a clamp with an axial floating function. This floating mechanism allows the wire brush to have a floating displacement of ±2mm in the direction perpendicular to the workpiece surface, so as to adapt to the slight undulations of the workpiece surface and work together with the mechanical sensor to achieve flexible cleaning.

[0010] Preferably, in step 1, the end of the robotic arm is also equipped with a force sensor to monitor the cleaning force of the wire brush in real time, ensuring that flexible cleaning is achieved and avoiding damage to the magnesium alloy structural components.

[0011] Preferably, the force threshold of the force sensor is 5 N. When the real-time monitored force value exceeds 5 N, the control host commands the robot arm to lift 0.1 mm along the normal direction until the force value returns to below 5 N.

[0012] Preferably, in step 1, the running path of the robotic arm is designed using the STL model of the magnesium alloy structural component. The specific process is as follows: 1) Input the parameters of the special wire brush: length 10 cm, diameter 5 cm; 2) Offset the STL model of the structural component upward by 2 mm along its surface normal to generate a tool running trajectory surface so that the wire brush works at a preset safe distance; 3) Generate equidistant parallel paths covering the entire surface by slicing on the offset surface. The key parameters of the path include: safe height 2 mm, path spacing 25 mm, brushing speed 15 mm / s, and wire brush rotation speed 300 r / min; 4) Convert the path into code that can be executed by the robot controller through the processor.

[0013] Preferably, in step 2, 1 L of acidic cleaning solution contains: 80-100 mL of phosphoric acid (H3PO4), 8-12 g of sodium molybdate (Na2MoO4), 1-3 mL of nitric acid (HNO3), 15-25 g of citric acid (C6H8O7), 1-2 g of hydroxyethyl cellulose (HEC), 0.3-0.7 g of 8-hydroxyquinoline (8HQ), and the remainder is deionized water.

[0014] Preferably, in step 2, the robotic arm for ultrasonic spray cleaning is equipped with a high-speed camera to monitor the cleaning process in real time.

[0015] Preferably, in step 2, the cleaning is considered complete when the surface color of the structural component changes uniformly from gray-black to metallic gray-white by observing with a high-speed camera.

[0016] Preferably, in step 2, the ultrasonic spray system has a frequency of 50 Hz, a duty cycle of 5%, a nozzle distance of 5-30 cm, a flow rate of 50-100 mL / min, an atomized droplet diameter of 50-100 μm, and a cleaning time of 30-120 s.

[0017] Preferably, in step 2, the temperature of the acidic cleaning solution is 20-40℃.

[0018] Preferably, in step 3, the laser cleaning system uses a pulsed fiber laser with a wavelength of 1064 nm, and uses a convex lens to focus the laser into a large spot with a diameter of 1 cm, controlling the laser strength to 10-50 W / cm². 2 Low-power focused lasers are used to ensure that magnesium alloy structural components are not damaged.

[0019] Preferably, in step 3, the robotic arm is also equipped with a spectrometer to monitor the cleaning effect in real time and provide feedback to the control host to dynamically adjust the laser parameters.

[0020] Preferably, in step 3, an argon protective atmosphere is provided during the laser cleaning process, while simultaneously blowing away any remaining solid particles.

[0021] Preferably, step 3 further includes rinsing and drying the structural components after laser cleaning.

[0022] Preferably, in step 3, the intensity of the characteristic spectral lines of Mg is monitored by a spectrometer. When the intensity tends to stabilize and the intensity of the spectral lines of O drops to the background noise level, the cleaning of the area is determined to be complete.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The cleaning method of the present invention can thoroughly clean large magnesium alloy structural parts with complex structures through a robotic arm. The specially made acidic cleaning solution can be precisely applied to the area to be cleaned and fully reacted. The reaction time can be precisely controlled by real-time monitoring through a high-speed camera. The laser cleaning system can finely clean the acidic cleaning solution residue and remaining contaminants. Moreover, the structural parts after laser cleaning can be linked with the arc additive manufacturing process, seamlessly connecting the additive manufacturing process.

[0024] 2. The acidic cleaning solution used in this invention is an environmentally friendly cleaning solution with no heavy metal pollution.

[0025] 3. The cleaning method of the present invention solves the problem of cleaning large and complex magnesium alloy structural parts. At the same time, the method avoids problems such as corrosion, overheating and structural damage, and can achieve automation and precise control, thereby improving cleaning quality and efficiency. Attached Figure Description

[0026] Figure 1 is a flowchart of the cleaning method of the present invention; Figure 2 is a diagram of the apparatus of the cleaning method of the present invention; Figure 3 is a structural schematic diagram of the mechanical sensor of the present invention; Figure 4 is a structural schematic diagram of the ultrasonic spraying device of the present invention; Figure 5 is a structural schematic diagram of the laser cleaning head of the present invention; In the figures, 1-control panel I; 2-pulsed fiber laser host; 3-power supply device I; 4-five-axis robotic arm; 5-control panel II; 6-power supply device II; 7-mechanical sensor; 8-special wire brush; 9-worktable; 10-substrate; 11-strument to be cleaned; 12-power supply device III; 13-cleaning fluid storage tank; 14-control panel III; 15-control host; 16-high-speed camera; 17-ultrasonic spraying device; 18-pulsed fiber laser cleaning head; 19-elastic element; 20-electrical interface; 21-nozzle; 22-ultrasonic transducer; 23-cleaning fluid supply channel; 24-compressed air inlet; 25-focusing lens group; 26-power supply and signal transmission channel. Detailed Implementation

[0027] The method of the present invention will be further described below with reference to the embodiments and accompanying drawings.

[0028] As shown in Figure 2, the cleaning equipment used in the cleaning method of the present invention includes a workbench 9, a base plate 10 disposed on the workbench 9, and a structural component 11 to be cleaned fixed on the base plate 10. The core components of the cleaning equipment include a special wire brush 8, an ultrasonic spray device 17, and a pulsed fiber laser cleaning head 18, which are respectively mounted on a five-axis robotic arm 4. The five-axis robotic arm 4 is connected to a control panel II 5 and a power supply device II 6; a force sensor 7 is also provided at its end. The ultrasonic spray device 17 is connected to an independent power supply device III 12, a cleaning fluid storage tank 13, and a control panel III 14; and is equipped with a high-speed camera 16 for monitoring the cleaning process. The pulsed fiber laser cleaning head 18 is driven by a pulsed fiber laser host 2 and is connected to a power supply device I 3 and a control panel I 1. The control panels I, II, and III of the entire set of equipment are all connected to a central control host 15 to achieve integrated and coordinated control.

[0029] As shown in Figure 3, in the cleaning device of the present invention, the mechanical sensor 7 includes an elastic element 19 and an electrical interface 20. It is connected to the special wire brush 8 through the electrical interface 20 and to the end of the five-axis robotic arm 4 through the elastic element 19, thus forming a flexible cleaning mechanism.

[0030] As shown in Figure 4, in the cleaning equipment of the present invention, the ultrasonic spraying device 17 includes a nozzle 21, an ultrasonic transducer 22, a cleaning fluid supply channel 23, and a compressed air inlet 24. The compressed air inlet 24 provides a protective atmosphere, and the cleaning fluid in the cleaning fluid supply channel 23 is sprayed onto the surface of the structural component through the nozzle 21 by the ultrasonic transducer 22.

[0031] As shown in Figure 5, in the cleaning equipment of the present invention, the pulsed fiber laser cleaning head 18 includes a focusing lens group 25, which is connected to the pulsed fiber laser host 2 through a power supply and signal transmission channel 26 to realize laser transmission and focusing. Example 1

[0032] For example, the magnesium alloy structural component to be cleaned is a Mg-9Gd-3Y-1Zn-0.6Zr alloy, and its shape is a concentric conical cylinder with an inner / outer diameter of 500 / 510 mm at the upper end and an inner / outer diameter of 100 / 110 mm at the lower end.

[0033] As shown in Figure 1, this embodiment provides a surface cleaning method for large and complex magnesium alloy structural parts formed by electric arc additive manufacturing, including the following steps: Step 1, a coordinate system is established on the worktable using a robotic arm, and the large and complex magnesium alloy structural parts to be cleaned are fixed on the worktable.

[0034] Step 2: Use UG software to set the cleaning path for the structural component to be cleaned. The specific process is as follows: 1) Input the parameters of the wire brush: length 10 cm, diameter 5 cm; 2) Offset the STL model of the structural component upwards by 2 mm along its surface normal to generate a tool trajectory surface so that the wire brush works within a preset safe distance; 3) Generate equidistant parallel paths covering the entire surface by slicing on the offset surface. The key parameters of the path include: safe height 2 mm, path spacing 25 mm, brushing speed 15 mm / s, and wire brush rotation speed 300 r / min; 4) Convert the path into code executable by the robot controller using a processor.

[0035] Step 3: Using a robotic arm equipped with special wire brushes, the magnesium alloy structural components are initially cleaned according to a preset path. Simultaneously, a force sensor mounted on the robotic arm monitors the cleaning force of the special wire brushes in real time. When the real-time monitored force exceeds 5 N, the control unit instructs the robotic arm to lift 0.1 mm along the normal direction until the force returns to 5 N. Below N, avoid damaging the magnesium alloy structural components; Step 4, using a robotic arm equipped with an ultrasonic spray system, spray a specially formulated acidic cleaning solution onto the surface of the structural components. The specially formulated acidic cleaning solution will adhere to the surface of the structural components and react fully to achieve a precision cleaning effect. A high-speed camera equipped at the end of the robotic arm is used to monitor the cleaning effect of the surface of the structural components in real time. When the surface color of the structural components changes from gray-black to metallic gray-white uniformly, it is determined that the cleaning is complete. In this embodiment, 45 seconds is used. After that, the cleaning solution is rinsed off in time to prevent damage to the substrate surface of the magnesium alloy structural components; Step 5, the surface of the structural components after precision cleaning is rinsed and dried with clean water to remove residual cleaning solution; Step 6, using a robotic arm equipped with a laser cleaning system, a low-power, large-spot laser is used to perform final cleaning on the surface of the structural components under argon protection. The cleaning effect is monitored in real time by a spectrometer and feedback is given to the control host to dynamically adjust the laser parameters to remove acidic cleaning solution residue and remaining contaminants. After cleaning, the surface cleaning quality of the magnesium alloy structural components is checked.

[0036] In step 3 of this embodiment, the special brush is composed of stainless steel wire with a diameter of 0.05 mm, the wire material is 304 stainless steel, and the wire density is 25 clusters / square centimeter; the surface of the wire is plated with an aluminum layer with a thickness of 10 μm by electroplating.

[0037] Furthermore, the wire brush is mounted at the end of the robotic arm via a clamp with an axial floating function. This floating mechanism allows the wire brush to have a floating displacement of ±2mm in the direction perpendicular to the workpiece surface, so as to adapt to the slight undulations of the workpiece surface and work together with the mechanical sensor to achieve flexible cleaning.

[0038] In step 4, the acidic cleaning solution 1 L contains: phosphoric acid H3PO4: 100 mL, sodium molybdate Na2MoO4: 10 g, nitric acid HNO3: 2 mL, citric acid C6H8O7: 20 g, hydroxyethyl cellulose HEC: 1.5 g, 8-hydroxyquinoline 8HQ: 0.5 g, and the remainder is deionized water.

[0039] The cleaning solution used in step 4 is a specially formulated solution. Based on a typical acidic cleaning solution, it incorporates hydroxyethyl cellulose and 8-hydroxyquinoline. Hydroxyethyl cellulose adds appropriate viscosity to the cleaning solution, preventing excessive dripping when sprayed onto a vertical surface. 8-hydroxyquinoline forms a protective layer on the magnesium alloy substrate surface, preventing excessive corrosion and damage to the substrate. This cleaning solution is simple to use, produces no heavy metal pollution, and aligns with green industry development.

[0040] In step 4 of this embodiment, a high-speed camera mounted at the end of the robotic arm is used to monitor the cleaning effect on the surface of the magnesium alloy structural component in real time, so as to avoid excessive reaction of the specially made acidic cleaning solution and damage to the magnesium alloy structural component.

[0041] In this embodiment, the ultrasonic spray system has a frequency of 50 Hz, a duty cycle of 5%, a nozzle distance of 15 cm, a cleaning fluid temperature of 25°C, a flow rate of 65 mL / min, and an atomized droplet diameter of 70 μm.

[0042] In step 6 of this embodiment, the laser cleaning system uses a convex lens to focus the laser into a large spot with a diameter of 1 cm and controls the laser strength to 30 W / cm². 2 A low-power focused laser was used to ensure that the magnesium alloy structural components were not damaged. The laser was emitted by a pulsed fiber laser with a wavelength of 1064 nm, and the laser parameters were: power 10 W, scanning speed 3000 mm / s, and power density 12.7 W / cm². 2 The pulse frequency is 20 kHz.

[0043] In step 6 of this embodiment, the intensity of the characteristic spectral line of Mg (e.g., at 517 nm) is monitored by a spectrometer. When the intensity tends to stabilize and the intensity of the spectral line of O (e.g., at 777 nm) drops to the background noise level, it is determined that the cleaning of the area is complete.

[0044] The above description is only one embodiment of the method of the present invention and does not limit the patent scope of the method of the present invention. Any equivalent structural or procedural transformations made based on the description and drawings of the method of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this method.

Claims

1. A surface cleaning method for large, complex magnesium alloy structural parts manufactured by arc additive manufacturing, characterized in that, The process includes the following steps: Step 1: Fix the large, complex magnesium alloy structural component to be cleaned on the worktable. Use a robotic arm equipped with a special wire brush at its end to perform preliminary cleaning on the surface of the component according to a preset path to initially remove the oxide film. Step 2: Use a robotic arm equipped with an ultrasonic spray system to spray a specially formulated acidic cleaning solution onto the surface of the component after preliminary cleaning. Use a high-speed camera to monitor the process in real time. Once the surface cleaning is complete, immediately rinse and dry the component. Step 3: Use a robotic arm equipped with a laser cleaning system to perform a third cleaning on the component to remove any residual acidic cleaning solution and remaining contaminants from the surface.

2. The cleaning method according to claim 1, characterized in that, In step 1, the special brush is 10 cm long and 5 cm in diameter, and is made of stainless steel wire with a diameter of 0.05-0.15 mm. The brush wire material is 304 stainless steel and the brush wire density is 20-30 clusters / square centimeter. The surface of the brush wire is plated with an aluminum layer with a thickness of 5-15 μm by electroplating.

3. The cleaning method according to claim 1, characterized in that, In step 1, a force sensor is also installed at the end of the robotic arm to monitor the brush cleaning force in real time. The force threshold of the force sensor is 5 N. When the real-time monitored force value exceeds 5 N, the host computer commands the robotic arm to lift 0.1 mm along the normal direction until the force value returns to below 5 N.

4. The cleaning method according to claim 1, characterized in that, In step 2, 1 L of acidic cleaning solution contains: 80-100 mL of phosphoric acid (H3PO4), 8-12 g of sodium molybdate (Na2MoO4), 1-3 mL of nitric acid (HNO3), 15-25 g of citric acid (C6H8O7), 1-2 g of hydroxyethyl cellulose (HEC), 0.3-0.7 g of 8-hydroxyquinoline (8HQ), and the remainder is deionized water.

5. The cleaning method according to claim 1, characterized in that, In step 2, a high-speed camera is installed on the robotic arm of the ultrasonic spray cleaning to monitor the cleaning process in real time. When the surface color of the structural component changes from gray-black to metallic gray-white, it is determined that the cleaning is complete.

6. The cleaning method according to claim 1, characterized in that, In step 2, the ultrasonic spray system has a frequency of 50 Hz, a duty cycle of 5%, a nozzle distance of 5-30 cm, a flow rate of 50-100 mL / min, an atomized droplet diameter of 50-100 μm, and a cleaning time of 30-120 s.

7. The cleaning method according to claim 1, characterized in that, In step 3, the laser cleaning system uses a pulsed fiber laser with a wavelength of 1064 nm. A convex lens is used to focus the laser into a large spot with a diameter of 1 cm, and the laser strength is controlled at 10⁻⁵⁰ W / cm². 2 Low-power focused lasers are used to ensure that magnesium alloy structural components are not damaged.

8. The cleaning method according to claim 1, characterized in that, In step 3, an argon protective atmosphere is provided during the laser cleaning process, while solid particle residue is blown away.

9. The cleaning method according to claim 1, characterized in that, In step 3, a spectrometer is also mounted on the robotic arm to monitor the cleaning effect in real time and provide feedback to the control host to dynamically adjust the laser parameters.

10. The cleaning method according to claim 9, characterized in that, In step 3, the intensity of the characteristic spectral lines of Mg is monitored by a spectrometer. When the intensity tends to stabilize and the intensity of the spectral lines of O drops to the background noise level, the cleaning of the area is considered complete.

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