Laser removal method and device for ceramic coating of aero-engine turbine blade

Abstract

The invention discloses an aero-engine turbine blade ceramic coating laser removing method and device, and relates to the technical field of surface cleaning, the aero-engine turbine blade ceramic coating laser removing device comprises a control cabinet, a driving platform, a working head, an image acquisition module, a clamping module, an operation panel and the like. Regional division and thickness identification of the ceramic coating on the surface of the blade are realized only through an image acquisition module based on an infrared thermal imaging technology, so that the complexity of a processing system is reduced, and the equipment cost is reduced; the driving platform adopts a gantry type five-degree-of-freedom driving mechanism, and five degrees of freedom respectively move along an x axis, a y axis and a z axis and rotate around an a axis and a b axis, so that the driving platform can adapt to machining of complex blade surface shapes; and the clamping module which is self-adaptive to center and provides reliable clamping is adopted, so that machining tremor or deformation and adverse effects of the machining tremor or deformation on track planning and machining precision are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of surface cleaning, and particularly to a method and equipment for laser removal of ceramic coatings on aero-engine turbine blades. Background Art

[0002] Since aero-engine turbine blades need to operate in high-temperature and high-pressure environments for a long time, their surfaces are usually coated with ceramic thermal barrier coatings to effectively improve the high-temperature resistance and service life of the blades. The ceramic thermal barrier coating is generally composed of ceramic materials such as yttria-stabilized zirconia (YSZ), and has excellent heat insulation performance, which can reduce the substrate temperature by hundreds of degrees Celsius. However, as the service time increases, the ceramic coating gradually ages, cracks, and peels off, losing its protective effect. Therefore, during the remanufacturing and maintenance of turbine blades, it is necessary to efficiently and non-destructively remove the failed coating.

[0003] Traditional coating removal methods mainly include mechanical or chemical methods such as sandblasting and chemical etching, which have problems such as low processing accuracy, serious environmental pollution, and large damage to the substrate material. In recent years, due to its advantages such as high energy density, non-contact processing, and strong controllability, laser removal technology has gradually become a research hotspot for ceramic coating removal. The laser heats the coating in a short time, causing its thermal expansion or melting and vaporization, thereby realizing the peeling of the coating, and has advantages such as high removal efficiency, small heat-affected zone, and strong automation potential.

[0004] However, in the existing laser removal technology, there are problems such as coating area identification, coating thickness identification, and reliable clamping of the blade. For coating area identification, machine vision systems, high-precision 3D laser scanning, or infrared thermal imaging technology are usually used; after identifying the coating area, ultrasonic testing, laser-induced ultrasound, eddy current testing, or optical interference methods are used to identify the thickness of different coating areas, and it is impossible to complete the identification of the coating area and thickness through the same set of systems; at the same time, due to the complex structure of the blade, traditional clamping of the blade is likely to cause processing tremors or deformations, which will directly affect the trajectory planning and processing accuracy. Summary of the Invention

[0005] The purpose of the present invention is to provide a laser removal processing method that can simultaneously identify the ceramic coating area and thickness only through infrared thermal imaging technology, and based on this method, provide a five-axis linkage laser processing equipment that can perform adaptive centering on the blade and provide reliable clamping.

[0006] For the above technical problems, the technical solution adopted by the present invention is: a method for laser removal of ceramic coatings on aero-engine turbine blades, characterized by including the following steps: Step S1: Clamp and fix a single blade, continuously blow hot air onto the blade surface from all around the blade. After the hot air blowing stops, let the blade cool naturally. The duration of natural cooling is the cooling time. When the cooling time expires, use an infrared thermal imager to sequentially capture the surface temperature distribution maps of the two side surfaces of the blade body. The two side surfaces of the blade body are the blade basin curved surface and the blade back curved surface respectively; Step S2: Save both surface temperature distribution maps as grayscale images. The pixel value in the grayscale image represents the temperature value at that pixel point; perform edge detection processing on the grayscale image to obtain the boundary lines where the temperature changes abruptly; the enclosed area that does not contain other boundary lines inside the boundary lines, or the enclosed area formed between two nested boundary lines is the isothermal region; Step S3: Set a threshold temperature. The isothermal region with an average temperature greater than or equal to the threshold temperature is the coating residue area, and the isothermal region with an average temperature less than the threshold temperature is the metal exposure area; Step S4: Estimate the surface area of each coating residue area according to the imaging parameters of the infrared thermal imager and the total number of pixel points in each coating residue area; estimate the coating thickness of each coating residue area according to the surface area of each coating residue area, the average temperature, the physical property parameters of the coating material, the ambient temperature, the energy parameters of the hot air, and the time parameters when the infrared thermal imager captures the surface of the coating residue area; Step S5: Mount a laser cleaning head by a gantry five-degree-of-freedom driving mechanism. Based on the coating thickness and the material removal characteristic parameters of the laser cleaning head, complete the trajectory planning of the laser cleaning operation for the entire coating residue area on the side surface of the blade through offline programming; Step S6: Perform laser cleaning on the current blade surface according to the result of the trajectory planning. After the cleaning is completed, conduct quality inspection on the current blade. The blades with incomplete removal of the surface coating are regarded as blades to be cleaned, and repeat the operations of Steps S1 to S5.

[0007] Further, in Step S1, the temperature of the hot air ranges from 200°C to 255°C; the duration of continuously blowing hot air is the heating time, and the heating time ranges from 30 s to 120 s; the cooling time ranges from 10 s to 60 s.

[0008] Further, in Step S2, the edge detection processing includes the following steps: Step S21: Denoise the grayscale image through Gaussian filtering; Step S22: Use the histogram equalization algorithm to enhance the contrast of the denoised grayscale image; Step S23: Apply the Sobel algorithm or the Canny algorithm to perform edge detection on the grayscale image after contrast enhancement, and the identified edge line is the boundary line.

[0009] Further, in step S3, the threshold temperature ranges from 100°C to 150°C.

[0010] Further, in step S4, the formula for calculating the surface area of the coating residue area is: ; In the formula, A is the surface area of the current coating residue area; is the surface bending coefficient of the current coating residue area, with a value range of 1 to 1.5; is the total number of pixel points in the current coating residue area; W is the width of the thermal imager imaging sensor; H is the height of the thermal imager imaging sensor; M is the horizontal resolution of the photo taken by the thermal imager; K is the vertical resolution of the photo taken by the thermal imager; r is the average value of the nearest distance and the farthest distance from the thermal imager lens to the side of the blade; f is the focal length of the thermal imager.

[0011] Further, in step S4, the formula for calculating the coating thickness of the coating residue area is: ; In the formula, d is the coating thickness of the current coating residue area; is the compensation coefficient of the current coating residue area; k is the thermal conductivity of the coating in the current coating residue area; t is the cumulative time from the start of natural cooling of the blade to the current coating residue area being photographed by the thermal imager; is the material density of the coating in the current coating residue area; c is the specific heat capacity of the coating in the current coating residue area; is the heating efficiency of the hot air, with a value range of 0.3 to 0.7; P is the output power of the device providing the hot air; is the average temperature of the current coating residue area at t time; is the temperature of the surrounding environment of the current coating residue area at t time; is the compensation adjustment amount of the current coating residue area.

[0012] The present invention also provides a laser processing device based on a laser removal method for ceramic coatings on aeroengine turbine blades, comprising a control cabinet, a driving platform, a sealing cover, a working head, an image acquisition module, a displacement linear module, a clamping module, an operation panel, a ventilation filter, and a hatch. It is characterized in that: the driving platform and the displacement linear module are both fixedly installed on the control cabinet; the end of the driving platform is installed with a working head, and the working head is a laser cleaning head; the sealing cover is fixedly installed on the control cabinet; the driving platform and the displacement linear module are both located inside the sealing cover; the image acquisition module is hoisted inside the sealing cover; the clamping module is fixedly installed on the moving end of the displacement linear module; the clamping module is used for clamping the blade to be processed; the operation panel is rotatably installed on the side of the control cabinet; the ventilation filter is fixedly installed on the top of the sealing cover; the hatch is hinged on the side of the sealing cover.

[0013] Further, the driving platform includes a support column, an x-axis linear module, a y-axis linear module, a z-axis linear module, an a-axis rotation module, and a b-axis rotation module; there are two x-axis linear modules; each x-axis linear module is fixedly connected to the control cabinet through two support columns; both ends of the y-axis linear module are fixedly connected to the moving ends of one x-axis linear module respectively; the z-axis linear module is fixedly installed on the moving end of the y-axis linear module; the a-axis rotation module is fixedly installed on the moving end of the z-axis linear module; the b-axis rotation module is fixedly installed on the rotating end of the a-axis rotation module; the working head is fixedly connected to the rotating end of the b-axis rotation module.

[0014] Further, the image acquisition module includes a hanging plate, a first motor, a cantilever, a sliding shaft, and an infrared camera; the hanging plate is fixedly installed inside the sealing cover; the first motor is fixedly installed on the hanging plate; the first end of the cantilever is fixedly installed on the output shaft of the first motor; the second end of the cantilever is an elastic clip structure with screw fastening, and the sliding shaft is slidably installed inside the elastic clip and fastened by a screw; the infrared camera is fixedly installed at the end of the sliding shaft; the infrared camera uses a thermal imager.

[0015] Furthermore, the clamping module includes a bracket, a second motor, a sliding sleeve, a mandrel, a secondary conical block, a primary conical block, a secondary connecting rod, a primary connecting rod, a boss, a sliding rod, a hollow stud, a spring, a clamping ball, a nozzle, a hot air blower, and an air outlet; the bracket is fixedly connected to the moving end of the shifting linear module; the second motor is fixedly installed on the bracket; the sliding sleeve is fixedly installed on the output shaft of the second motor; the middle part of the mandrel is rotationally connected to the bracket through a threaded fit; both ends of the mandrel are square shaft structures; the primary conical block is fixedly installed on the square shaft at the first end of the mandrel; the boss is hinged to the square shaft at the first end of the mandrel; the secondary conical block is fixedly installed on the square shaft at the second end of the mandrel; the square shaft at the second end of the mandrel is inserted into the sliding sleeve and is slidably connected to the sliding sleeve; the cone angle of the secondary conical block is greater than that of the primary conical block; the middle parts of the two primary connecting rods are circumferentially and evenly hinged to the bracket; the middle parts of the two secondary connecting rods are circumferentially and evenly hinged to the bracket; the root base of the blade to be processed includes four positioning side surfaces and one positioning bottom surface; the first positioning side surface and the third positioning side surface of the root base of the blade to be processed are tenon tooth structures, and the surface of the tenon tooth structure is a wavy curved surface; the second positioning side surface and the fourth positioning side surface of the root base of the blade to be processed are positioning end surfaces, and the positioning end surfaces are flat surfaces; the positioning bottom surface of the root base of the blade to be processed is a flat surface; the first end of the primary connecting rod is provided with a cylindrical surface structure for clamping the tenon tooth structure; the second end of the primary connecting rod is provided with a spherical surface structure that is in sliding point contact connection with the primary conical block; the first end of the secondary connecting rod is rotationally installed with a hollow stud through a threaded fit; a sliding rod is slidably installed in the hollow stud; a clamping ball is fixedly installed at the end of the sliding rod; a spring is sleeved on the sliding rod, and both ends of the spring are fixedly connected to the clamping ball and the hollow stud respectively; the clamping ball is used for clamping the positioning end surface of the root base of the blade to be processed; the second end of the secondary connecting rod is provided with a spherical surface structure that is in sliding point contact connection with the secondary conical block; the boss is used for fitting the positioning bottom surface of the root base of the blade to be processed; the rotation axis of the primary connecting rod on the bracket is orthogonal to the rotation axis of the secondary connecting rod on the bracket; the four nozzles are circumferentially and evenly fixedly installed on the bracket, and one nozzle is arranged between every two adjacent primary connecting rods and secondary connecting rods; the first end of the nozzle faces the blade to be processed; the hot air blower is fixedly installed on the bracket; the hot air blower is provided with four air outlets; each air outlet is communicated with the second end of a nozzle through a pipeline.

[0016] The beneficial effects of the present invention compared with the prior art are as follows: (1) The regional division and thickness identification of the ceramic coating on the blade surface are realized only through an image acquisition module based on infrared thermal imaging technology, reducing the complexity of the processing system and the equipment cost; (2) Since each pixel in infrared thermal imaging corresponds to a temperature point, a thickness distribution map with micron-level resolution can be generated to accurately locate the residual coating area and thickness; (3) The driving platform adopts a gantry five-degree-of-freedom driving mechanism, and the five degrees of freedom are the movements along the x-axis, y-axis, and z-axis, as well as the rotations around the a-axis and b-axis, which can adapt to the processing of complex blade surface shapes; (4) The clamping module that adopts self-adaptive centering and provides reliable clamping eliminates the processing tremors or deformations and their adverse effects on the trajectory planning and processing accuracy. Description of the Drawings

[0017] Figure 1 It is a flow chart of the laser removal method for the ceramic coating of the aero-engine turbine blade of the present invention.

[0018] Figure 2 It is the general assembly drawing of the laser processing equipment of the present invention.

[0019] Figure 3 It is a schematic diagram of the structure and installation relationship of each transmission part on the control cabinet of the present invention.

[0020] Figure 4 It is a schematic diagram of the structure of the clamping module of the present invention.

[0021] In the figure: 1 - control cabinet; 2 - driving platform; 3 - sealing cover; 4 - working head; 5 - image acquisition module; 6 - displacement linear module; 7 - clamping module; 8 - operation panel; 9 - ventilation filter; 10 - hatch; 11 - blade to be processed; 201 - pillar; 202 - x-axis linear module; 203 - y-axis linear module; 204 - z-axis linear module; 205 - a-axis rotation module; 206 - b-axis rotation module; 501 - hanging plate; 502 - first motor; 503 - cantilever; 504 - sliding shaft; 505 - infrared camera; 701 - bracket; 702 - second motor; 703 - sliding sleeve; 704 - mandrel; 705 - sub-cone block; 706 - main-cone block; 707 - sub-link; 708 - main-link; 709 - convex platform; 710 - sliding rod; 711 - hollow stud; 712 - spring; 713 - clamping ball; 714 - nozzle; 715 - hot air blower; 716 - air outlet. Detailed Embodiment

[0022] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments. Among them, the accompanying drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0023] Figures 1 to 4 This is a preferred embodiment of the present invention.

[0024] As Figure 1 shown, the laser removal method of the ceramic coating of the aeroengine turbine blade of the present invention includes the following steps: Step S1: Clamp and fix a single blade, continuously blow hot air from the periphery of the blade to the blade surface, the temperature range of the hot air is 200°C to 255°C, and 230°C is taken in this embodiment; the time for continuously blowing hot air is the heating time, and the heating time range is 30s to 120s, and 80s is taken in this embodiment; after the hot air stops blowing, let the blade cool naturally, and the continuous time of natural cooling is the cooling time, and the cooling time range is 10s to 60s, and 30s is taken in this embodiment; when the cooling time ends, use an infrared thermal imager to sequentially take the surface temperature distribution maps of the two sides of the blade body, and the two sides of the blade body are the blade concave surface and the blade convex surface respectively; Step S2: Save both surface temperature distribution maps as grayscale images, and the pixel values in the grayscale images represent the temperature values at the corresponding pixel points; perform denoising processing on the grayscale images by Gaussian filtering; use the histogram equalization algorithm to enhance the contrast of the denoised grayscale images; apply the Sobel algorithm or the Canny algorithm to perform edge detection on the grayscale images after contrast enhancement, and the identified edge lines are the boundary lines to obtain the boundary lines where the temperature changes suddenly; the enclosed area without other boundary lines inside the boundary lines or the enclosed area between two nested boundary lines is the isothermal area; Step S3: Set a threshold temperature, and the threshold temperature range is 100°C to 150°C, and 140°C is taken in this embodiment; the isothermal area with an average temperature greater than or equal to the threshold temperature is the coating residue area, and the isothermal area with an average temperature less than the threshold temperature is the metal exposure area; Step S4: Estimate the surface area of each coating residue area according to the imaging parameters of the infrared thermal imager and the total number of pixel points in each coating residue area; the calculation formula for the surface area of the coating residue area is: ; In the formula, A is the surface area of the current coating residue area; is the surface bending coefficient of the current coating residue area, with a value range of 1 to 1.5; is the total number of pixels in the current coating residue area; W is the width of the imaging sensor of the thermal imager; H is the height of the imaging sensor of the thermal imager; M is the horizontal resolution of the photo taken by the thermal imager; K is the vertical resolution of the photo taken by the thermal imager; r is the average value of the closest distance and the farthest distance from the lens of the thermal imager to the side of the blade; f is the focal length of the thermal imager; According to the surface area and average temperature of each coating residue area, the physical property parameters of the coating material, the ambient temperature, the energy parameters of the hot air, and the time parameters when the thermal imager takes the surface of the coating residue area, estimate the coating thickness of each coating residue area. The calculation formula for the coating thickness of the coating residue area is: ; In the formula, d is the coating thickness of the current coating residue area; is the compensation coefficient of the current coating residue area; k is the thermal conductivity of the coating in the current coating residue area; t is the cumulative time from the start of the natural cooling of the blade to the time when the current coating residue area is photographed by the thermal imager; is the material density of the coating in the current coating residue area; c is the specific heat capacity of the coating in the current coating residue area; is the heating efficiency of the hot air, with a value range of 0.3 to 0.7; P is the output power of the device providing the hot air; is the current coating residue area at t the average temperature at the moment; is the surrounding environment of the current coating residue area at t the temperature at the moment; is the compensation adjustment amount of the current coating residue area; Step S5: Mount the laser cleaning head by the gantry five-degree-of-freedom driving mechanism, and based on the coating thickness and the material removal characteristic parameters of the laser cleaning head, perform offline programming through PowerMill software to complete the trajectory planning of the laser cleaning operation for the entire coating residue area on the side of the blade; Step S6: Perform laser cleaning on the current blade surface according to the result of the trajectory planning. After cleaning, conduct quality inspection on the current blade. For the blades with unclean surface coatings removed, regard them as blades to be cleaned and re-perform the operations in Steps S1 to S5.

[0025] Such as Figure 2As shown in the figure, a laser processing device for the laser removal method of the ceramic coating of the aero-engine turbine blade based on the present invention is given; the driving platform 2 and the displacement linear module 6 are both fixedly installed on the control cabinet 1; a working head 4 is installed at the end of the driving platform 2, and the working head 4 is a laser cleaning head; the sealing cover 3 is fixedly installed on the control cabinet 1; the driving platform 2 and the displacement linear module 6 are both located inside the sealing cover 3; the image acquisition module 5 is hoisted inside the sealing cover 3; the clamping module 7 is fixedly installed on the moving end of the displacement linear module 6; the clamping module 7 is used for clamping the blade 11 to be processed; the operation panel 8 is rotatably installed on the side of the control cabinet 1; the ventilation filter 9 is fixedly installed on the top of the sealing cover 3; the hatch 10 is hinged on the side of the sealing cover 3.

[0026] As Figure 3 shown, in the driving platform 2, there are two x-axis linear modules 202; each x-axis linear module 202 is fixedly connected to the control cabinet 1 through two struts 201; both ends of the y-axis linear module 203 are fixedly connected to the moving ends of one x-axis linear module 202 respectively; the z-axis linear module 204 is fixedly installed on the moving end of the y-axis linear module 203; the a-axis rotation module 205 is fixedly installed on the moving end of the z-axis linear module 204; the b-axis rotation module 206 is fixedly installed on the rotating end of the a-axis rotation module 205; the working head 4 is fixedly connected to the rotating end of the b-axis rotation module 206; in the image acquisition module 5, the hanging plate 501 is fixedly installed inside the sealing cover 3; the first motor 502 is fixedly installed on the hanging plate 501; the first end of the cantilever 503 is fixedly installed on the output shaft of the first motor 502; the second end of the cantilever 503 is an elastic clip structure with screw fastening, and the sliding shaft 504 is slidably installed inside the elastic clip and fastened by a screw fastener; the infrared camera 505 is fixedly installed at the end of the sliding shaft 504; the infrared camera 505 uses a thermal imager.

[0027] As Figure 3 and Figure 4As shown, in the clamping module 7, the bracket 701 is fixedly connected to the moving end of the shifting linear module 6; the second motor 702 is fixedly installed on the bracket 701; the sliding sleeve 703 is fixedly installed on the output shaft of the second motor 702; the middle part of the mandrel 704 is rotationally connected to the bracket 701 through threaded cooperation; both ends of the mandrel 704 are square shaft structures; the main cone block 706 is fixedly installed on the square shaft at the first end of the mandrel 704; the boss 709 is hinged to the square shaft at the first end of the mandrel 704; the sub-cone block 705 is fixedly installed on the square shaft at the second end of the mandrel 704; the square shaft at the second end of the mandrel 704 is inserted into the sliding sleeve 703 and is slidably connected to the sliding sleeve 703; the cone apex angle of the sub-cone block 705 is greater than that of the main cone block 706; the middle parts of the two main connecting rods 708 are circumferentially and evenly hinged to the bracket 701; the middle parts of the two sub-connecting rods 707 are circumferentially and evenly hinged to the bracket 701; the root base of the blade 11 to be processed includes four positioning side surfaces and one positioning bottom surface; the first positioning side surface and the third positioning side surface of the root base of the blade 11 to be processed are tenon tooth structures, and the surface of the tenon tooth structure is a wavy curved surface; the second positioning side surface and the fourth positioning side surface of the root base of the blade 11 to be processed are positioning end surfaces, and the positioning end surfaces are flat surfaces; the positioning bottom surface of the root base of the blade 11 to be processed is a flat surface; the first end of the main connecting rod 708 is provided with a cylindrical surface structure for clamping the tenon tooth structure; the second end of the main connecting rod 708 is provided with a spherical surface structure that is in sliding point contact connection with the main cone block 706; the first end of the sub-connecting rod 707 is rotationally installed with a hollow stud 711 through threaded cooperation; a sliding rod 710 is slidably installed in the hollow stud 711; a clamping ball 713 is fixedly installed at the end of the sliding rod 710; a spring 712 is sleeved on the sliding rod 710, and both ends of the spring 712 are fixedly connected to the clamping ball 713 and the hollow stud 711 respectively; the clamping ball 713 is used for clamping the positioning end surface of the root base of the blade 11 to be processed; the second end of the sub-connecting rod 707 is provided with a spherical surface structure that is in sliding point contact connection with the sub-cone block 705; the boss 709 is used for fitting the positioning bottom surface of the root base of the blade 11 to be processed; the rotation axis of the main connecting rod 708 on the bracket 701 is orthogonal to the rotation axis of the sub-connecting rod 707 on the bracket 701; the four nozzles 714 are circumferentially and evenly fixedly installed on the bracket 701, and one nozzle 714 is arranged between every two adjacent main connecting rods 708 and sub-connecting rods 707; the first end of the nozzle 714 faces the blade 11 to be processed; the hot air blower 715 is fixedly installed on the bracket 701; four air outlets 716 are arranged on the hot air blower 715; each air outlet 716 is communicated with the second end of one nozzle 714 through a pipeline.

[0028] The working principle of the present invention: When the laser processing equipment of the present invention is in use, first, the hatch 10 should be opened to clamp the blade to be processed, and after the clamping is completed, the hatch 10 is closed; for the clamping method, such as Figure 4As shown, the second motor 702 drives the mandrel 704 to rotate forward, causing the secondary cone block 705 and the primary cone block 706 to move Figure 4 downward as shown. At this time, the distance between the first ends of the two main linkages 708 and the distance between the two clamping balls 713 both increase to allow the blade 11 to be processed to be placed. Then, the blade 11 to be processed is manually placed and supported by the boss 709. Next, the second motor 702 drives the mandrel 704 to rotate in reverse, causing the secondary cone block 705 and the primary cone block 706 to move Figure 4 upward as shown. The primary cone block 706 contacts the second ends of the two main linkages 708 and forces them to swing, causing the first ends of the two main linkages 708 to gradually clamp the dovetail structure of the blade 11 to be processed; the secondary cone block 705 contacts the second ends of the two secondary linkages 707 and forces them to swing, causing the clamping balls 713 at the first ends of the two secondary linkages 707 to gradually clamp the positioning end face of the blade 11 to be processed; during the above process, the main linkages 708 and the boss 709 mainly play a role in rigidly clamping the blade to be processed, and the secondary linkages 707 mainly play a role in initial positioning of the blade to be processed; the structural design of the clamping module 7 enables the blade to be processed to be accurately centered and clamped; in particular, the setting of the slide rod 710 and the spring 712 is used to provide an elastic support force, and the setting of the hollow stud 711 is used to adjust the initial distance between the two clamping balls 713 or the elastic support force after clamping the blade to be processed.

[0029] As Figure 3 shown, the two side surfaces of the blade body described in step S1 are the two surfaces of the blade 11 to be processed facing the displacement linear module 6 and the hot air blower 715. In Figure 3 , the side surface of the blade 11 to be processed facing the displacement linear module 6 is the blade basin curved surface, and the side surface of the blade 11 to be processed facing the hot air blower 715 is the blade back curved surface; when using the laser processing equipment of the present invention, the displacement linear module 6 is controlled through the operation panel 8 to drive the clamping module 7 to move to a position where the axes of the second motor 702 and the first motor 502 coincide, corresponding to Figure 3The clamping module 7 moves leftward; then, the hot air blower 715 starts preheating but does not blow air. At the same time, the first motor 502 drives the cantilever 503 to rotate to a position where the cantilever 503 is perpendicular to the displacement linear module 6, and the infrared camera 505 is located on the side where the displacement linear module 6 is. After the hot air blower 715 finishes preheating, it continuously blows hot air at 230 °C into the four nozzles 714 for 80 s. The nozzles 714 are thin-walled metal tubes that can be manually bent and deformed. In this embodiment, the first ends of the four nozzles 714 all point obliquely upward at 45° towards the blade 11 to be processed. After the hot air stops being blown in, the blade is allowed to cool naturally for 30 s, and then the infrared camera 505 collects the surface temperature distribution map of the blade basin surface of the blade 11 to be processed facing the displacement linear module 6. Then, the first motor 502 drives the cantilever 503 to rotate 180°, and then the infrared camera 505 collects the surface temperature distribution map of the blade back surface of the blade 11 to be processed facing the hot air blower 715. The time interval between the two acquisitions of the surface temperature distribution maps is 5 s; according to the different specifications of the blade 11 to be processed, the clamping position of the sliding shaft 504 on the cantilever 503 can be manually adjusted in advance.

[0030] After collecting the surface temperature distribution map, the work in steps S2 to S4 is carried out, where r is approximately the distance from the thermal imager lens to the axis of the first motor 502; at the same time, the displacement linear module 6 drives the clamping module 7 to move to the processing position below the driving platform 2 and remains stationary; after completing the work in step S5, the driving platform 2 drives the working head 4 to perform the work in step S6, and finally the removal of the ceramic coating is completed.

[0031] Particularly, in this embodiment, three sides of the sealing cover 3 are hollowed out and embedded with transparent glass; the hatch 10 is hollowed out and embedded with transparent glass.

[0032] Particularly, in this embodiment, a control system and a cooling system are provided in the control cabinet 1. The control system is used for relaying the electrical connection between the operation panel 8 and the driving platform 2, the working head 4, the image acquisition module 5, the displacement linear module 6, the clamping module 7, and the ventilation filter 9; the cooling system is used for controlling the environmental temperature inside the sealing cover 3; the cooling system is also used for cooling the working head 4.

[0033] Particularly, in this embodiment, the ventilation filter 9 connects the internal and external spaces of the sealing cover 3. The ventilation filter 9 is internally provided with a fan and a filter element, which are used for ventilation and air exchange while filtering out the fumes generated during processing inside the sealing cover 3.

[0034] Particularly, the displacement linear module 6, the x-axis linear module 202, the y-axis linear module 203, and the z-axis linear module 204 can all adopt a linear motor or a ball screw structure driven by a motor.

[0035] In particular, the operation panel 8 is hinged at the first end of two serially-connected and mutually-hinged connecting rods; the second ends of the two serially-connected and mutually-hinged connecting rods are hinged to the control cabinet 1.

Claims

1. A method for laser removal of ceramic coatings on aeroengine turbine blades, characterized in that, It includes the following steps: Step S1: Clamp and fix a single blade, continuously blow hot air towards the blade surface from all around the blade. After the hot air stops being blown, let the blade cool naturally. The duration of natural cooling is the cooling time. When the cooling time ends, use an infrared thermal imager to sequentially capture the surface temperature distribution maps of the two sides of the blade body. The two sides of the blade body are the suction surface curve and the pressure surface curve respectively; Step S2: Save both surface temperature distribution maps as grayscale images. The pixel value in the grayscale image represents the temperature value at that pixel point; by performing edge detection processing on the grayscale image, obtain the boundary line where the temperature changes abruptly; the enclosed area that does not contain other boundary lines inside the boundary line, or the enclosed area formed between two nested boundary lines inside and outside is the isothermal region; Step S3: Set a threshold temperature. The isothermal region with an average temperature greater than or equal to the threshold temperature is the coating residue area, and the isothermal region with an average temperature less than the threshold temperature is the metal exposure area; Step S4: According to the imaging parameters of the infrared thermal imager and the total number of pixels in each coating residue area, estimate the surface area of each coating residue area; according to the surface area and average temperature of each coating residue area, the physical property parameters of the coating material, the ambient temperature, the energy parameters of the hot air, and the time parameters when the infrared thermal imager captures the surface of the coating residue area, estimate the coating thickness of each coating residue area; Step S5: Mount a laser cleaning head by a gantry five-degree-of-freedom driving mechanism. Based on the coating thickness and the material removal characteristic parameters of the laser cleaning head, through offline programming, complete the trajectory planning of the laser cleaning operation for the entire coating residue area on the side of the blade; Step S6: Perform laser cleaning on the current blade surface according to the result of the trajectory planning. After cleaning, conduct quality inspection on the current blade. The blade with incomplete removal of the surface coating is regarded as the blade to be cleaned, and repeat the operations of steps S1 to S5; 2. The method for laser removal of ceramic coating on an aeroengine turbine blade as claimed in claim 1, wherein: In step S1, the temperature range of the hot air is 200°C to 255°C; the duration of continuously blowing hot air is the heating time, and the value range of the heating time is 30s to 120s; the value range of the cooling time is 10s to 60s.

3. The method for laser removal of ceramic coating on an aeroengine turbine blade according to claim 2, wherein: In step S2, the edge detection processing includes the following steps: Step S21: Perform denoising processing on the grayscale image through Gaussian filtering; Step S22: Use the histogram equalization algorithm to perform contrast enhancement processing on the denoised grayscale image; Step S23: Apply the Sobel algorithm or the Canny algorithm to perform edge detection on the grayscale image after contrast enhancement processing, and the identified edge line is the boundary line.

4. The method for laser removal of the ceramic coating of an aeroengine turbine blade as described in claim 3, characterized in that: In step S3, the value range of the threshold temperature is 100°C to 150°C.

5. The method for laser removal of the ceramic coating on the aero-engine turbine blade according to claim 4, characterized in that: In step S4, the calculation formula for the surface area of the coating residue area is: ； Wherein, A is the surface area of the current coating residue area; is the surface bending coefficient of the current coating residue area, and the value range is from 1 to 1.5; is the total number of pixel points in the current coating residue area; W is the width of the imaging sensor of the thermal imager; H is the height of the imaging sensor of the thermal imager; M is the horizontal resolution of the photo taken by the thermal imager; K is the vertical resolution of the photo taken by the thermal imager; r is the average value of the nearest distance and the farthest distance from the lens of the thermal imager to the side of the blade; f is the focal length of the thermal imager.

6. The method for laser removal of the ceramic coating on the aero-engine turbine blade according to claim 5, characterized in that: In step S4, the calculation formula for the coating thickness of the coating residue area is: ； Wherein, d is the coating thickness of the current coating residue area; is the compensation coefficient of the current coating residue area; k is the thermal conductivity of the coating in the current coating residue area; t is the cumulative time consumed from the start of natural cooling of the blade to the current coating residue area being photographed by the thermal imager; is the material density of the coating in the current coating residue area; c is the specific heat capacity of the coating in the current coating residue area; is the heating efficiency of the hot air, and the value range is from 0.3 to 0.7; P is the output power of the device that provides the hot air; is the current coating residue area at t is the average temperature at the moment; is the temperature of the surrounding environment of the current coating residue area at t at the moment; is the compensation adjustment amount of the current coating residue area.

7. The laser processing equipment for the laser removal method of the ceramic coating of the aero-engine turbine blade according to claim 6, comprising a control cabinet (1), a driving platform (2), a sealing cover (3), a working head (4), an image acquisition module (5), a displacement linear module (6), a clamping module (7), an operation panel (8), a ventilation filter (9), and a hatch (10), characterized in that: The driving platform (2) and the shifting linear module (6) are both fixedly installed on the control cabinet (1); a working head (4) is installed at the end of the driving platform (2), and the working head (4) is a laser cleaning head; the sealing cover (3) is fixedly installed on the control cabinet (1); the driving platform (2) and the shifting linear module (6) are both located inside the sealing cover (3); the image acquisition module (5) is hoisted inside the sealing cover (3); the clamping module (7) is fixedly installed on the moving end of the shifting linear module (6); the clamping module (7) is used for clamping the blade to be processed (11); the operation panel (8) is rotatably installed on the side of the control cabinet (1); the ventilation filter (9) is fixedly installed on the top of the sealing cover (3); the hatch door (10) is hinged on the side of the sealing cover (3).

8. The laser processing device according to claim 7, wherein: The driving platform (2) includes a support column (201), an x-axis linear module (202), a y-axis linear module (203), a z-axis linear module (204), an a-axis rotation module (205), and a b-axis rotation module (206); there are two x-axis linear modules (202); each x-axis linear module (202) is fixedly connected to the control cabinet (1) through two support columns (201); both ends of the y-axis linear module (203) are fixedly connected to the moving ends of an x-axis linear module (202) respectively; the z-axis linear module (204) is fixedly installed on the moving end of the y-axis linear module (203); the a-axis rotation module (205) is fixedly installed on the moving end of the z-axis linear module (204); the b-axis rotation module (206) is fixedly installed on the rotating end of the a-axis rotation module (205); the working head (4) is fixedly connected to the rotating end of the b-axis rotation module (206).

9. The laser processing device according to claim 8, wherein: The image acquisition module (5) includes a hanging plate (501), a first motor (502), a cantilever (503), a sliding shaft (504), and an infrared camera (505); the hanging plate (501) is fixedly installed inside the sealing cover (3); the first motor (502) is fixedly installed on the hanging plate (501); the first end of the cantilever (503) is fixedly installed on the output shaft of the first motor (502); the second end of the cantilever (503) is an elastic clip structure with screw fastening, and the sliding shaft (504) is slidably installed inside the elastic clip and tightened by a screw fastening hoop; the infrared camera (505) is fixedly installed at the end of the sliding shaft (504); the infrared camera (505) uses a thermal imager.

10. The laser processing device according to claim 9, characterized in that: The clamping module (7) includes a bracket (701), a second motor (702), a sliding sleeve (703), a mandrel (704), a secondary conical block (705), a primary conical block (706), a secondary connecting rod (707), a primary connecting rod (708), a boss (709), a sliding rod (710), a hollow stud (711), a spring (712), a clamping ball (713), a nozzle (714), a hot air blower (715), and an air outlet (716); the bracket (701) is fixedly connected to the moving end of the displacement linear module (6); the second motor (702) is fixedly installed on the bracket (701); the sliding sleeve (703) is fixedly installed on the output shaft of the second motor (702); the middle part of the mandrel (704) is rotationally connected to the bracket (701) through a threaded fit; both ends of the mandrel (704) are square shaft structures; the primary conical block (706) is fixedly installed on the square shaft at the first end of the mandrel (704); the boss (709) is hinged to the square shaft at the first end of the mandrel (704); the secondary conical block (705) is fixedly installed on the square shaft at the second end of the mandrel (704); the square shaft at the second end of the mandrel (704) is inserted into the sliding sleeve (703) and is slidably connected to the sliding sleeve (703); the cone angle of the secondary conical block (705) is greater than the cone angle of the primary conical block (706); the middle parts of the two primary connecting rods (708) are circumferentially and evenly hinged to the bracket (701); the middle parts of the two secondary connecting rods (707) are circumferentially and evenly hinged to the bracket (701); the root base of the blade to be processed (11) includes four positioning side faces and one positioning bottom face; the first positioning side face and the third positioning side face of the root base of the blade to be processed (11) are tenon tooth structures, and the surface of the tenon tooth structure is a wavy curved surface; the second positioning side face and the fourth positioning side face of the root base of the blade to be processed (11) are positioning end faces, and the positioning end faces are flat surfaces; the positioning bottom face of the root base of the blade to be processed (11) is a flat surface; the first end of the primary connecting rod (708) is provided with a cylindrical surface structure for clamping the tenon tooth structure; the second end of the primary connecting rod (708) is provided with a spherical surface structure that is in sliding point contact connection with the primary conical block (706); the first end of the secondary connecting rod (707) is rotationally installed with a hollow stud (711) through a threaded fit; a sliding rod (710) is slidably installed inside the hollow stud (711); a clamping ball (713) is fixedly installed at the end of the sliding rod (710); a spring (712) is sleeved on the sliding rod (710), and both ends of the spring (712) are fixedly connected to the clamping ball (713) and the hollow stud (711) respectively; the clamping ball (713) is used for clamping the positioning end face of the root base of the blade to be processed (11); the second end of the secondary connecting rod (707) is provided with a spherical surface structure that is in sliding point contact connection with the secondary conical block (705); the boss (709) is used for fitting the positioning bottom face of the root base of the blade to be processed (11); the rotation axis of the primary connecting rod (708) on the bracket (701) is orthogonal to the rotation axis of the secondary connecting rod (707) on the bracket (701);Four nozzles (714) are fixedly installed on the bracket (701) in a circumferentially uniform distribution, and one nozzle (714) is arranged between every two adjacent main connecting rods (708) and auxiliary connecting rods (707); the first end of the nozzle (714) faces the blade to be processed (11); the hot air blower (715) is fixedly installed on the bracket (701); four air outlets (716) are arranged on the hot air blower (715); each air outlet (716) is communicated with the second end of one nozzle (714) through a pipeline.

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