Method for preventing laser damage to walls by water channels in a hollow part

Abstract

The application discloses a method for preventing cavity from being damaged by water guide laser, comprising the following steps: scanning to obtain the geometric data of the internal cooling cavity of a turbine blade, and establishing a digital 3D model of the cavity; image processing on the scanning data; size shrinkage design; selecting polyurethane, nylon or polypropylene-polyester blend material to process a rigid protective piece; embedding the protective piece into the internal cavity of the turbine blade; injecting a thermosetting soft material into the gap; continuously curing the buffer layer; and removing the soft material. Through fine model design, material optimization and construction of multiple protective layers, the application effectively solves the problems of instability, insufficient adaptability and material performance limitations in protecting the cavity wall in the prior art, and significantly improves the protection effect during water guide laser processing.

Description

Technical Field

[0001] This invention relates to the field of water-guided laser processing technology, and in particular to a method for preventing water-guided laser damage to the walls of hollow components. Background Technology

[0002] Currently, water-guided laser processing technology has been applied in multiple fields. Its core idea lies in using water as a medium to guide the laser beam, reducing the thermal impact and mechanical shock of the laser on the workpiece. For example, existing water-guided laser devices (such as CN101823183A) focus the laser beam and project it through the top wall of a container, then use a water spray system on the bottom wall to conduct the beam underwater, thus protecting the workpiece surface to some extent. Simultaneously, some methods utilize water-guided laser blocking protection technology, adding specific substances to the workpiece interlayer to form a protective layer, thereby reducing the direct impact of the laser on the surface.

[0003] Although the above technologies have reduced the damage to the wall surface caused by laser processing to some extent, the existing technologies still have the following problems and shortcomings:

[0004] 1) Unstable protective effect: Water, as a medium, is greatly affected by factors such as temperature, flow rate, and pollution, making it difficult to maintain a uniform and sufficiently thick protective layer. The protective effect may decrease due to localized evaporation or uneven flow, leading to localized ablation or thermal damage to the wall surface under the high energy of the laser.

[0005] 2) Insufficient adaptability of cavity structures: For workpieces with complex internal cavities, current protection solutions mostly rely on the isolation effect of the water layer itself, lacking targeted design. Traditional products often fail to accurately model and control the internal shape and dimensions of the cavity, making it difficult to form a protective layer that fits tightly with the cavity wall. This can cause the laser beam to deviate from the predetermined path due to scattering or reflection, thereby damaging the cavity wall.

[0006] 3) Material selection and process limitations: Existing products rely heavily on conventional materials for protective components, which lack sufficient heat resistance, impact resistance, and cushioning performance, failing to provide adequate protection under high-energy laser effects. Furthermore, the manufacturing and installation processes of protective devices lack flexibility, making it difficult to precisely control the size and shape of different cavity components. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method to prevent water-guided laser damage to the walls of cavity components.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preventing water-guided laser damage to the wall of a cavity component includes the following steps:

[0010] (a) Obtain geometric data of the internal cooling cavity of the turbine blade through high-precision CT scanning or three-dimensional laser scanning, and establish a digital 3D model of the cavity;

[0011] (b) Image processing of scanned data: The Otsu thresholding algorithm is used to automatically determine the upper and lower limits of grayscale to complete binarization, and morphological opening and closing operations are performed on the binarization results to eliminate noise and artifacts;

[0012] (c) Based on the 3D model in step (a), perform a size reduction design to generate a protective part model that matches the original cavity shape but has a reduced volume. The reduction amount is controlled within the range of 0.5-2mm.

[0013] (d) Select polyurethane, nylon or polypropylene-polyester blend materials and manufacture rigid protective parts that match the shrinkage model by CNC machining, injection molding or 3D printing;

[0014] (e) The protective component is embedded inside the turbine blade cavity, forming a uniform gap between the outer wall of the protective component and the inner wall of the cavity;

[0015] (f) Injecting a substance with a viscosity μ = 0.8-1.2 Pa·s and a permeability k ≥ 1×10 into the gap. -10 A thermoplastic soft material of m² is used to fill gaps under an injection pressure of Δp = 0.15-0.25 MPa.

[0016] (g) Soft materials self-level to form a continuous buffer layer of 0.3-0.8 mm and then cure;

[0017] (h) A detachable sealing interface is pre-installed on the protective component for subsequent removal of soft materials by heating to soften or mechanical discharge.

[0018] Preferably, step (b) uses the Otsu thresholding algorithm to automatically determine the upper and lower bounds and minimize the intra-class variance:

[0019]

[0020] Perform morphological opening and closing operations on the binarized results to remove noise and minor artifacts.

[0021] Preferably, the inward design in step (c) needs to satisfy the ratio of gap volume to protective component volume as 1:5-1:8, and the offset of the normal vector direction of each point on the curved surface after inward reduction is ≤0.1mm.

[0022] Preferably, the screening conditions for the polyurethane, nylon, or polypropylene-polyester blend material in step (d) are as follows:

[0023] Based on the shrinkage model, easily machinable materials such as polyurethane and nylon, which have excellent heat resistance and impact resistance, are selected. Protective components that match the shrinkage model are manufactured using CNC machining, injection molding, or 3D printing technologies. These protective components have a precise structure and can be firmly embedded into the internal cavity of the turbine blades.

[0024] If the original surface is parametrically represented as normal vector ;

[0025] The soft material is a polypropylene-polyester blend, with viscosity μ and permeability k satisfying Darcy's law.

[0026]

[0027] The injection pressure is designed to be Δp≈0.2MPa to ensure that the gap is filled within seconds.

[0028] Preferably, the protective component in step (d) is manufactured using selective laser sintering of nylon powder, with a layer thickness controlled at 20-50 μm and a porosity of <0.5%.

[0029] Preferably, the soft material in step (f) is a composite material of polypropylene and polyester blended in a mass ratio of 65:35, with a heat distortion temperature ≥180℃, an elastic modulus of 50-100MPa, and satisfying Darcy's law flow equation.

[0030] Preferably, in step (f), the injection pressure Δp = 0.2 ± 0.02 MPa, the filling time is controlled between 5 and 15 seconds, and the gap filling integrity is ≥ 99%.

[0031] In step (g), the self-leveling thickness is controlled between 0.3-0.8 mm, forming a continuous buffer layer after curing. Following step (g), energy absorption verification is performed: the energy absorbed per unit area E of the buffer layer during laser drilling is calculated. abs :

[0032]

[0033] Where m is the material mass, C p Given specific heat capacity and ΔT as the temperature difference, E is required. abs ≥30% of laser energy density.

[0034] The detachable interface in step (h) is a tubular structure with a threaded sealing cap, located in the non-stressed area of ​​the protective component, with an inner diameter of 3-5 mm.

[0035] The present invention also proposes the application of the aforementioned method in the water-guided laser drilling process of turbine blades, in order to avoid damage to the workpiece during the drilling process.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] 1. To address the shortcomings of existing technologies, this invention proposes a novel strategy for preventing wall damage, primarily through:

[0038] 1) Cavity model extraction and internal shrinkage design: High-precision 3D modeling technology is used to extract the cavity geometry data and internal shrinkage design is carried out on the inner wall to ensure that the subsequent protective components can form a uniform gap with the cavity wall.

[0039] 2) Use materials that are easy to process and have excellent cushioning properties: Select materials such as polyurethane and nylon to process and manufacture protective parts. These materials have good heat resistance, impact resistance and cushioning ability, and can effectively absorb laser energy.

[0040] 3) Multi-layer protection design: The manufactured protective component is inserted into the cavity, and polypropylene and polyester materials are filled between it and the cavity wall to form a buffer isolation layer, which further disperses the laser energy and prevents damage to the wall.

[0041] In summary, this invention, through meticulous model design, material optimization, and the construction of multiple protective layers, effectively solves the problems of instability, insufficient adaptability, and material performance limitations in the protection of cavity walls in existing technologies, and significantly improves the protective effect during water-guided laser processing. Attached Figure Description

[0042] Figure 1 This is a process flow diagram of a method for preventing water-guided laser damage to the wall of a cavity component, as proposed in this invention.

[0043] Figure 2 This is a diagram of the protective structure for the application of the method of the present invention in water-guided laser processing;

[0044] Figure 3 This is a construction structure diagram of the method of the present invention when applied to water-guided laser processing. Detailed Implementation

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0046] Example

[0047] Turbine blades are critical high-temperature structural components in aero-engines, typically featuring complex cooling chambers and flow channels to achieve effective cooling in high-temperature environments. While water-guided laser drilling offers good quality and is suitable for turbine blades, direct water-guided laser drilling can lead to localized ablation of the internal cavity walls, affecting the blade's structural integrity and service life. This invention addresses this issue by proposing a water-guided laser protection strategy based on hollow components, with the specific steps as follows:

[0048] 1) Extract the cavity model

[0049] High-precision CT scanning or 3D laser scanning technology is used to obtain detailed geometric data of the cooling cavity inside the turbine blades, and a digital 3D model is established. This step ensures that subsequent designs can fully reflect the actual internal structure.

[0050] 2) Image segmentation and 3D reconstruction

[0051] The Otsu thresholding algorithm is used to automatically determine the upper and lower bounds and minimize the intra-class variance.

[0052]

[0053] Perform morphological opening and closing operations on the binarized results to remove noise and minor artifacts.

[0054] 3) Protective component design

[0055] Based on the 3D model of the turbine blade cooling cavity, the internal dimensions of the cavity were reduced to create a slightly smaller model than the original cavity. This ensures a uniform gap between the protective component and the cavity wall after installation, while also providing sufficient space for filling with soft materials to achieve a buffering and protective effect.

[0056] 4) Selection of soft materials:

[0057] Based on the shrinkage model, easily machinable materials such as polyurethane and nylon with excellent heat resistance and impact resistance are selected. Protective components that match the shrinkage model are manufactured using CNC machining, injection molding, or 3D printing technologies. These protective components have a precise structure and can be firmly embedded into the internal cavity of the turbine blades.

[0058] If the original surface is parametrically represented as normal vector ;

[0059] The soft material is a polypropylene-polyester blend, with viscosity μ and permeability k satisfying Darcy's law.

[0060]

[0061] The injection pressure is designed to be Δp≈0.2MPa to ensure that the gap is filled within seconds.

[0062]

[0063] The thickness of the self-leveling compound is controlled at 0.3-0.8mm, and a continuous buffer layer is formed after curing.

[0064] Energy absorption calculation

[0065]

[0066] 5) Reserve an exclusion mechanism for maintenance.

[0067] The design incorporates removable or drainable interfaces, allowing the soft filling material to be easily removed during subsequent maintenance, cleaning, or replacement by softening with heat or mechanical removal. This design ensures that the protective layer can be updated when necessary, extending the overall service life of the turbine blades.

[0068] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preventing water-guided laser damage to the wall of a cavity component, characterized in that, Includes the following steps: (a) Obtain geometric data of the internal cooling cavity of the turbine blade through high-precision CT scanning or three-dimensional laser scanning, and establish a digital 3D model of the cavity; (b) Image processing of scanned data: The Otsu thresholding algorithm is used to automatically determine the upper and lower limits of grayscale to complete binarization, and morphological opening and closing operations are performed on the binarization results to eliminate noise and artifacts; (c) Based on the 3D model in step (a), perform a size reduction design to generate a protective part model that matches the original cavity shape but has a reduced volume. The reduction amount is controlled within the range of 0.5-2mm. (d) Select polyurethane, nylon or polypropylene-polyester blend materials and manufacture rigid protective parts that match the shrinkage model by CNC machining, injection molding or 3D printing; (e) The protective component is embedded inside the turbine blade cavity, forming a uniform gap between the outer wall of the protective component and the inner wall of the cavity; (f) Injecting a substance with a viscosity μ = 0.8-1.2 Pa·s and a permeability k ≥ 1×10 into the gap. -10 A thermoplastic soft material of m² is used to fill gaps under an injection pressure of Δp = 0.15-0.25 MPa. (g) Soft materials self-level to form a continuous buffer layer of 0.3-0.8 mm and then cure; (h) A detachable sealing interface is pre-installed on the protective component for subsequent removal of soft materials by heating to soften or mechanical discharge.

2. The method for preventing water-guided laser damage to the wall of a cavity component according to claim 1, characterized in that, Step (b) uses the Otsu thresholding algorithm to automatically determine the upper and lower bounds and minimize the intra-class variance: ； Perform morphological opening and closing operations on the binarized results to remove noise and minor artifacts.

3. The method for preventing water-guided laser damage to the wall of a cavity component according to claim 1, characterized in that, The inward design in step (c) must meet the requirement that the ratio of the gap volume to the protective component volume is 1:5-1:8, and the offset of the normal vector direction of each point on the curved surface after inward reduction is ≤0.1mm.

4. The method for preventing water-guided laser damage to the wall of a cavity component according to claim 1, characterized in that, The protective component in step (d) is manufactured using selective laser sintering of nylon powder, with a layer thickness controlled at 20-50 μm and a porosity of <0.5%.

5. The method for preventing water-guided laser damage to the wall of a cavity component according to claim 1, characterized in that, The soft material in step (f) is a composite material of polypropylene and polyester blended in a mass ratio of 65:35, with a heat distortion temperature ≥180℃ and an elastic modulus of 50-100MPa.

6. The method for preventing water-guided laser damage to the wall of a cavity component according to claim 1, characterized in that, In step (f), the injection pressure Δp = 0.2 ± 0.02 MPa, the filling time is controlled between 5 and 15 seconds, and the gap filling integrity is ≥ 99%.

7. The method for preventing water-guided laser damage to the wall of a cavity component according to claim 1, characterized in that, The detachable interface in step (h) is a tubular structure with a threaded sealing cap, located in the non-stressed area of ​​the protective component, with an inner diameter of 3-5 mm.

8. The application of the method described in any one of claims 1-7 in the process of water-guided laser drilling of turbine blades.

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