Method for preventing water-guided laser of cavity piece from damaging wall

Abstract

The invention discloses a method for preventing water-guided laser of a cavity part from damaging a wall, which comprises the following steps of: scanning to obtain geometric data of a cooling cavity in a turbine blade, and establishing a cavity digital 3D model; performing image processing on the scanning data; the size is designed to be shrunk inwards; a polyurethane, nylon or polypropylene-polyester blend material is selected to process a rigid protection piece; the protection part is embedded into the cavity of the turbine blade; a thermosetting soft material is injected into the gap; curing the continuous buffer layer; the soft material is removed. Through fine model design, material optimization and construction of multiple protection layers, the problems of instability, insufficient adaptability, material performance limitation and the like in the aspect of protecting the wall surface of the cavity in the prior art are effectively solved, and the protection effect during water-jet guided laser processing is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-guided laser processing, and particularly relates to a method for preventing water-guided laser from damaging the wall of a cavity part. BACKGROUND

[0002] At present, water-guided laser processing technology has been applied in many fields, and its core idea is to use water as a medium to guide the laser beam, thereby reducing the thermal impact and mechanical impact of the laser on the workpiece. For example, the existing water-guided laser device (such as CN101823183A) focuses the laser beam and then shoots it into the container from the top wall, and realizes water conduction with the help of the water spraying system of the bottom wall, thereby protecting the workpiece wall to a certain extent. At the same time, some methods use water-guided laser blocking protection technology to add specific substances in the workpiece interlayer to form a protective layer, so as to reduce the direct impact of the laser on the wall.

[0003] Although the above-mentioned technology reduces the damage of laser processing to the wall to a certain extent, the existing technology still has the following problems and deficiencies:

[0004] 1) Unstable protection effect: Water as a medium is greatly affected by factors such as temperature, flow rate and pollution, and it is difficult to maintain a uniform and thick protective layer at all times. Due to the local evaporation or uneven flow of the water layer, the protection effect may decrease, and then the wall may be locally ablated or thermally damaged under the action of high-energy laser.

[0005] 2) Insufficient adaptability of cavity structure: For workpieces with complex internal cavities, the current protection scheme relies mainly on the isolation effect of the water layer, and lacks targeted design. Traditional products often fail to accurately model and size the internal shape of the cavity, making it difficult to form a protective layer that closely matches the cavity wall, which may 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: The existing products rely on conventional materials for the material selection of the protection components, which lack sufficient heat resistance, impact resistance and cushioning performance, and cannot provide sufficient protection under the action of high-energy laser. In addition, the manufacturing and installation process of the protection device lacks flexibility, and it is difficult to finely adjust according to the size and shape of different cavity parts. SUMMARY

[0007] The purpose of the present application is to solve the problems existing in the prior art, and to provide a method for preventing water-guided laser from damaging the wall of a cavity part.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] A method for preventing water-guided laser from damaging the wall of a cavity part, comprising the following steps:

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

[0011] (b) Image processing of the scanning data: automatically determine the upper and lower limits of the gray scale to complete the binarization by using Otsu threshold algorithm, and perform morphological opening and closing operation on the binarization result to eliminate noise and artifacts;

[0012] (c) According to the 3D model of (a), the size is designed to be shrunk, and a protective part model matching the original cavity shape but with reduced volume is generated, and the shrinkage amount is controlled in the range of 0.5-2mm;

[0013] (d) Select polyurethane, nylon or polypropylene-polyester blend material, and manufacture rigid protective parts matching the shrinkage model by numerical control machining, injection molding or 3D printing;

[0014] (e) Embed the protective part inside the turbine blade cavity, and form a uniform gap between the outer wall of the protective part and the inner wall of the cavity;

[0015] (f) Inject a thermosetting soft material with viscosity μ = 0.8-1.2 Pa·s and permeability k≥1×10 -10 m 2 Under the injection pressure of Δp = 0.15-0.25 MPa, fill the gap;

[0016] (g) The soft material self-levels to form a continuous buffer layer of 0.3-0.8mm and solidifies;

[0017] (h) Pre-set a detachable sealing interface on the protective part for subsequent removal of the soft material by heating and softening or mechanical discharge.

[0018] Preferably, (b) uses Otsu threshold algorithm to automatically determine the upper and lower limits, and minimizes the intra-class variance:

[0019]

[0020] Perform morphological opening and closing operation on the binarization result to eliminate noise and small artifacts.

[0021] Preferably, the shrinkage design of (c) needs to meet the gap volume to protective part volume ratio of 1:5-1:8, and the directional offset of normal vector of each point on the curved surface after shrinkage is ≤0.1mm.

[0022] Preferably, the selection conditions of polyurethane, nylon or polypropylene-polyester blend material in (d) are:

[0023] Based on the reduced model, easy-to-process materials such as polyurethane and nylon with excellent heat and impact resistance are selected and manufactured through CNC machining, injection molding, or 3D printing to match the reduced model. This protective component has a precise structure and can be firmly embedded in the internal cavity of the turbine blade.

[0024] If the original surface is parameterized as x(u,v), the normal vector

[0025] The soft material is a polypropylene-polyester blend, and its viscosity μ and permeability k satisfy Darcy's law:

[0026]

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

[0028] Preferably, the protective element of (d) is manufactured by selective laser sintering of nylon powder, with the layer thickness controlled to be 20-50 μm and the porosity of the molded element being less than 0.5%.

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

[0030] Preferably, the injection pressure of (f) is Δp=0.2±0.02 MPa, the filling time is controlled within 5-15 seconds, and the gap filling completeness is ≥99%.

[0031] The thickness of the self-leveling in (g) is controlled to be 0.3-0.8 mm, and a continuous buffer layer is formed after solidification; after (g), energy absorption verification is performed: the energy value E absorbed per unit area of ​​the buffer layer during laser drilling is calculated. abs :

[0032] E abs =mc p ΔT

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

[0034] The detachable interface (h) is a tubular structure with a threaded sealing cover, which is arranged in the non-stressed area of ​​the protective part, and the inner diameter of the interface is 3-5mm.

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

[0036] Compared with the prior art, the present application has the beneficial effects that:

[0037] 1. To overcome the shortcomings of the prior art, the present application proposes a brand-new anti-wall damage strategy, mainly through:

[0038] 1) Cavity model extraction and inward design: high-precision three-dimensional modeling technology is used to extract cavity geometric data, and the inner wall is designed inwardly to ensure that the subsequent protective parts can form a uniform gap with the cavity wall.

[0039] 2) Use materials that are easy to process and have excellent buffering performance: polyurethane, nylon and other materials are selected to process and manufacture protective parts, which have good heat resistance, impact resistance and buffering capacity, and can effectively absorb laser energy.

[0040] 3) Multi-protection layer design: the processed protective parts are inserted into the cavity, and polypropylene and polyester materials are filled between the protective parts and the cavity wall to form a buffer isolation layer, further dispersing the laser energy and preventing wall damage.

[0041] In summary, through fine model design, material optimization and multi-protection layer construction, the present application effectively solves the problems of instability, insufficient adaptability and material performance limitations in protecting the cavity wall of the prior art, and significantly improves the protection effect during water guide laser processing. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 A process flow chart of a method for preventing water guide laser from damaging the wall of a cavity part is proposed for the present application.

[0043] Figure 2 A protective structure diagram of the method of the present application when applied to water guide laser processing;

[0044] Figure 3 A construction structure diagram of the method of the present application when applied to water guide laser processing. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described below in conjunction with the prior known technology. Obviously, the described embodiments are only part of the embodiments of the present application, not all.

[0046] Example 1:

[0047] Turbine blade is a key high-temperature structural component in an aero-engine, and a complex cooling cavity and flow channel are usually designed inside the turbine blade to achieve effective cooling in a high-temperature environment. Since water guide laser drilling has good quality and is suitable for turbine blades, direct water guide laser drilling may cause local ablation of the inner cavity wall, thereby affecting the structural integrity and service life of the blade. The present application proposes a water guide laser protection strategy based on a cavity part, and the specific steps are as follows:

[0048] S1, extracting a cavity model

[0049] The cooling cavity inside the turbine blade is scanned by high-precision CT scanning or three-dimensional laser scanning technology to obtain detailed geometric data of the cavity, and a digital 3D model is established. This step ensures that the subsequent design can fully reflect the actual internal structure.

[0050] 2) image segmentation and 3D reconstruction

[0051] The upper and lower limits are automatically determined by using the Otsu threshold algorithm to minimize the intra-class variance

[0052]

[0053] Morphological opening and closing operation is performed on the binary result to remove noise and small artifacts

[0054] 3) protection part design

[0055] According to the 3D model of the turbine blade cooling cavity, the size of the cavity inside is designed to be shrunk, and an inner shrinkage model slightly smaller than the original cavity size is generated. In this way, a uniform gap can be formed between the protection part and the cavity wall after installation, and enough space can be reserved for filling soft materials to achieve the buffering protection effect.

[0056] 4) soft material selection:

[0057] According to the inner shrinkage model, polyurethane, nylon and other easily processable materials with excellent heat resistance and impact resistance are selected, and the protection part matching the inner shrinkage model is manufactured by numerical control machining, injection molding or 3D printing technology. The protection part has precise structure and can be firmly embedded in the turbine blade internal cavity.

[0058] If the original curved surface is parameterized as x(u,v), the normal vector

[0059] The soft material is a polypropylene-polyester blend, and the viscosity μ and permeability k satisfy the Darcy law:

[0060]

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

[0062] E abs = mc p ΔT

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

[0064] Energy absorption calculation

[0065] E abs = mc p ΔT

[0066] 5) Reserve exclusion mechanism for maintenance

[0067] During the design process, a detachable or discharge interface is reserved, so that the filled soft material can be conveniently removed by heating and softening or mechanical discharge during subsequent maintenance, cleaning or replacement. This design ensures that the protective layer can be updated when necessary, prolonging the overall service life of the turbine blade.

[0068] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art, according to the technical solution and the inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preventing water-guided laser damage to the wall of a cavity, characterized in that: The following steps are involved: (a) Obtain geometric data of the cooling cavity inside the turbine blade through high-precision CT scanning or 3D laser scanning, and create a digital 3D model of the cavity; (b) Image processing of the scanned data: using the Otsu threshold algorithm to automatically determine the upper and lower limits of the grayscale to complete the binarization, and performing morphological opening and closing operations on the binarization results to eliminate noise and artifacts; (c) Based on the 3D model in (a), a size reduction design is performed to generate a protective part model that matches the original cavity shape but is reduced in size, with the reduction amount controlled within the range of 0.5-2 mm; (d) Use polyurethane, nylon, or polypropylene-polyester blend materials to manufacture rigid protective parts that match the internal model through CNC machining, injection molding, or 3D printing; (e) embedding the protective member into the turbine blade cavity to form a uniform gap between the outer wall of the protective member and the inner wall of the cavity; (f) Injection of a solution with a viscosity of μ = 0.8-1.2 Pa·s and a permeability of k ≥ 1×10 -10 m 2 Thermosetting soft materials fill the gap at an injection pressure of Δp = 0.15-0.25MPa; (g) The soft material self-levels to form a 0.3-0.8 mm continuous buffer layer and solidifies; (h) A removable sealing interface is provided on the protective part for subsequent removal of the soft material by heating softening or mechanical discharge.

2. The method for preventing water-guided laser damage to the wall of a cavity according to claim 1, characterized in that: (b) The Otsu threshold algorithm is used to automatically determine the upper and lower limits to minimize the intra-class variance: Perform morphological opening and closing operations on the binarization results to remove noise and tiny artifacts.

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

4. The method for preventing water-guided laser damage to the wall of a cavity according to claim 1, characterized in that: The screening conditions for the (d) polyurethane, nylon or polypropylene-polyester blend material are: Based on the reduced model, easy-to-process materials such as polyurethane and nylon with excellent heat and impact resistance are selected and manufactured through CNC machining, injection molding, or 3D printing to match the reduced model. This protective component has a precise structure and can be firmly embedded in the internal cavity of the turbine blade. If the original surface is parameterized as x(u,v), the normal vector The soft material is a polypropylene-polyester blend, and its viscosity μ and permeability k satisfy Darcy's law: The designed injection pressure Δp≈0.2MPa ensures that the gap is filled within seconds.

5. The method for preventing water-guided laser damage to the wall of a cavity according to claim 1, characterized in that: The protective part (d) is manufactured by selective laser sintering nylon powder, the layer thickness is controlled to be 20-50 μm, and the porosity of the molded part is less than 0.5%.

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

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

8. The method for preventing water-guided laser damage to the wall of a cavity according to claim 1, characterized in that: The thickness of the self-leveling in (g) is controlled to be 0.3-0.8 mm, and a continuous buffer layer is formed after solidification; after (g), energy absorption verification is performed: the energy value E absorbed per unit area of ​​the buffer layer during laser drilling is calculated. abs : E abs =mc p ΔT Where m is the material mass, C p is the specific heat capacity, ΔT is the temperature difference, and E is required abs ≥30% of laser energy density.

9. The method for preventing water-guided laser damage to the wall of a cavity according to claim 1, characterized in that: The detachable interface (h) is a tubular structure with a threaded sealing cover, which is arranged in the non-stressed area of ​​the protective part, and the inner diameter of the interface is 3-5mm.

10. Application of the method according to any one of claims 1 to 9 in the process of water-guided laser drilling of turbine blades.

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