Accurate preparation method of interference film hole in turbine blade

Abstract

The invention relates to the technical field of turbine blade air film hole machining, in particular to a precise preparation method for interference air film holes in a turbine blade. By formulating a process route, accurately positioning a scheme, designing a special electrode and optimizing process parameters, the vector direction of the film hole meets the design requirement, and the machining efficiency is improved. The method comprises the following steps: performing structured light scanning on a blade to obtain point cloud data, and calculating a translation and rotation matrix to position an actual film hole position; the small hole machine electrode which is bent by 30 degrees and the forming machine electrode which is eccentrically and parallelly connected are designed to avoid interference; bottom hole and forming machining parameters are optimized, and machining precision and efficiency are ensured. The problem that the air film hole cannot be prepared according to the design requirement is solved, the batch production requirement is met, and the machining efficiency and reliability are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aero-engine and gas turbine manufacturing, and in particular relates to a method for accurately preparing interference air film holes on turbine blades. Background Art

[0002] In the field of aeroengines and gas turbines, the design of film holes on turbine blades is crucial for improving blade cooling performance and service life. Traditional film hole design typically involves fine-tuning the vector angle to avoid interfering structures, thereby enabling electrospark (EDM) hole machining. However, this design approach has significant technical shortcomings. First, in practice, fine-tuning the film hole vector angle to avoid interfering structures can result in failure to meet design requirements, necessitating compromises and impacting blade performance and reliability. Second, certain complex interference situations cannot be addressed with simple vector angle adjustments, making it difficult to achieve film hole fabrication that meets design requirements. These issues significantly limit the precision and efficiency of turbine blade film hole fabrication. Especially in mass production, efficiently and accurately fabricating interference holes and shielding holes that meet design requirements is a pressing technical challenge. Therefore, developing a method for precisely fabricating interference film holes on turbine blades, ensuring that the film hole vector orientation meets design requirements while improving fabrication efficiency and meeting mass production requirements, is of great engineering significance and technical value. Summary of the Invention

[0003] To address the shortcomings of existing techniques for fabricating interference film holes on turbine blades, the present invention provides a precise method for fabricating interference film holes on turbine blades. This method aims to address the existing issue of film hole vector angle adjustment, which can prevent design requirements from being met. By developing a precise process route, optimizing positioning methods, designing specialized electrodes, and optimizing parameters, the method ensures that the film hole vector orientation meets design requirements and improves processing efficiency.

[0004] The technical solution of the present invention is: A method for accurately preparing interference film holes on a turbine blade, characterized by comprising the following steps: S1: Precisely position the turbine blades by using a structured light scanner to obtain actual model point cloud data and calculate the deviation between the theoretical position and the actual position using the iterative closest point (ICP) algorithm; S2: Calculate the actual position of each air film hole based on the translation and rotation matrix; S3: Based on the principle of aligning the air film hole vector with the Z axis of the device, calculate the five-axis decomposition coordinates of the air film hole drilling position; S4: Install the fixture on the EDM small hole machine and align and tighten it to complete the bottom hole processing; S5: Install the parts with completed bottom hole processing on the EDM machine to complete the final forming process.

[0005] Furthermore, in the above-mentioned precise preparation method of interference film holes on a turbine blade, the translation and rotation matrix is used to describe the position and posture changes of the actual model relative to the theoretical model, and its expression includes translation vectors x0, y0, z0 and rotation vectors ix, jx, kx, iy, jy, ky, iz, jz, kz.

[0006] Furthermore, in the above-mentioned method for accurately preparing interference film holes on a turbine blade, the calculation formula for the actual position of each film hole is: x′=(x-x0)·ix+(y-y0)·jx+(z-z0)·kx, y′=(x-x0)·iy+(y-y0)·jy+(z-z0)·ky, z′=(x-x0)·iz+(y-y0)·jz+(z-z0)·kz, Among them, x′, y′, z′ are the positions of the air film hole in the actual coordinate system; x, y, z are the positions of the air film hole in the theoretical coordinate system; x0, y0, z0 are translation vectors; ix, jx, kx are X-axis rotation vectors; iy, jy, ky are Y-axis rotation vectors; iz, jz, kz are Z-axis rotation vectors.

[0007] Furthermore, in the above-mentioned precise preparation method of interference air film holes on turbine blades, the electrode of the electric spark hole machine adopts a curved design with a bending angle of 30° to avoid interference between the electrode and the blade edge plate during processing. The electrode includes a connector, an outer sleeve, an insulating layer and a guide, wherein the outer sleeve has a curved design with the guide to guide the electrode wire into the blade edge plate.

[0008] Furthermore, in the above-mentioned precise preparation method of interference air film holes on turbine blades, the electrode of the electric spark forming machine is designed to be parallel to the direction of movement, and interference with the blade edge plate is avoided through parallel transfer, including a guide rod, an eccentric, a tightening bolt and a forming electrode.

[0009] Furthermore, the aforementioned method for precisely preparing interference film holes on turbine blades utilizes relatively high processing parameters, as the inner wall of the film hole can be roughened and the thickness of the remelting layer does not need to be considered. The process parameters are: pulse width 6-12 levels, pulse interval 10-18 levels, current 3-5 levels, capacitance 2-3 levels, sensitivity 0-2 levels, servo speed 1-3 levels, voltage 50-80V, and rotation speed 50-300 rpm. For film hole preparation using an EDM machine, the presence of a bottom hole provides excellent operating conditions and high processing efficiency, so the parameters primarily consider the controllability of the remelting layer thickness. Specific parameters include: pulse width 10-30μs, pulse interval 80-120μs, current 1-3 levels, high voltage 1 level, servo 4-6 levels, tool lift 1 level, discharge 3 levels, negative polarity, low voltage 0 level, and flushing pressure 0.08-0.12MPa.

[0010] Through the above-mentioned technical solution, the present invention solves the problem of turbine blade air film hole interference holes being unable to be prepared according to design requirements, while ensuring that the air film hole vector direction meets the design requirements. Furthermore, the method significantly improves the production efficiency of interference air film holes, meeting the needs of mass production.

[0011] Furthermore, the key technical points of the present invention include the following aspects: The first is a process for preparing interference holes and masking holes for turbine blade film holes, encompassing three key steps: precise positioning, bottom hole preparation, and forming. This process achieves high-precision film hole processing through precise point cloud data matching, five-axis decomposition coordinate calculation, and specialized electrode design.

[0012] The second innovation is electrode design. The electrode for the EDM hole cutter is curved at a 30° angle, effectively preventing interference between the electrode and the blade edge during machining. The electrode for the EDM forming machine is designed to be parallel to the direction of motion. This parallel connection avoids interference with the blade edge, further improving machining accuracy and reliability.

[0013] The third is the optimization of process parameters. In response to the different requirements of bottom hole preparation and forming processing, the EDM parameters are optimized respectively to ensure a balance between processing efficiency and precision.

[0014] Advantages and beneficial effects of the present invention: The above technical solution fully meets the design requirements for the preparation of interference holes and shielding holes in turbine blade film holes, significantly improving processing efficiency and meeting the needs of mass production. Furthermore, the curved electrode and parallel transition design effectively avoid interference between the electrode and the blade edge, ensuring the safety and reliability of the processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of an electrode for electrospark small hole machining according to the present invention; Figure 2 It is a structural schematic diagram of the electrode for EDM machining of the present invention.

[0016] In the figure, 1-connector; 2-outer sleeve; 3-insulating layer; 4-guide; 5-guide rod; 6-eccentric; 7-tightening bolt; 8-molded electrode. DETAILED DESCRIPTION

[0017] The present invention provides a method for accurately preparing interference film holes on turbine blades, which is mainly achieved by formulating a process route, accurately positioning a solution, designing a dedicated electrode, and optimizing processing parameters. Figure 1 and attached Figure 2 Specific embodiments of the present invention are described in detail.

[0018] First, the turbine blades must be precisely positioned. This involves scanning the blades and their fixtures with a structured light scanner to obtain point cloud data for the actual model. The Iterative Closest Point (ICP) algorithm is used to match the actual point cloud with the theoretical model, calculating a translation and rotation matrix. This matrix describes the position and orientation of the actual model relative to the theoretical model, expressed as translation vectors x0, y0, and z0, and rotation vectors ix, jx, kx, iy, jy, ky, iz, jz, and kz. Based on this matrix, the actual position of each film hole can be calculated.

[0019] The calculation formula for the air film hole position is: x′=(x-x0)·ix+(y-y0)·jx+(z-z0)·kx, y′=(x-x0)·iy+(y-y0)·jy+(z-z0)·ky, z′=(x-x0)·iz+(y-y0)·jz+(z-z0)·kz.

[0020] Where x, y, and z are positions in the theoretical coordinate system, and x′, y′, and z′ are positions in the actual coordinate system.

[0021] Furthermore, based on the principle of aligning the film hole vector with the Z axis of the equipment, the five-axis decomposition coordinates of the film hole drilling position were calculated. These coordinates are applicable to two sets of equipment: the EDM machine for small hole processing and the EDM forming machine for final forming processing.

[0022] Next comes the design and application of electrodes.

[0023] According to the attached Figure 1As shown in the figure, the electrode of the EDM machine adopts a curved design with a bending angle of 30°, which effectively avoids the interference between the electrode and the blade edge plate during the processing. The electrode is composed of multiple parts, including a connector 1, an outer sleeve 2, an insulating layer 3 and a guide 4. The guide 4 has a curved design 5, which is used to guide the electrode wire into the blade edge plate to ensure processing accuracy. Figure 2 As shown, the electrode of the EDM machine is designed to be parallel to the direction of motion, and avoids interference with the blade edge plate through parallel switching. The electrode includes a guide rod 5, an eccentric 6, a clamping bolt 7 and a forming electrode 8.

[0024] After completing the electrode design, the processing parameters need to be optimized.

[0025] For the process of preparing the bottom hole by the EDM machine, since the inner wall of the air film hole is allowed to be rough and the thickness of the remelting layer does not need to be considered, a larger processing parameter is selected. The specific processing parameters are shown in Table 1: Table 1 EDM small hole machining parameters

[0026] For the process of preparing air film holes by EDM, due to the presence of bottom holes, the working conditions are good and the processing efficiency is high, so the parameters mainly consider the controllability of the remelting layer thickness. The specific parameter settings are shown in Table 2: Table 2 EDM machining parameters

[0027] In actual operation, follow the steps below.

[0028] First, install the fixture on the small hole machine and align and press it, install the φ0.4 standard guide and electrode wire, align the tool on the inner hole of the fixture and the workbench surface, and install the part on the fixture.

[0029] Then, according to the dotting process parameters, each previously determined air film hole position is dotted with a depth of no more than 0.5 mm in the basic coordinate system.

[0030] Next, remove the standard guide from the equipment and install the φ0.4 special electrode guide on the W axis of the small hole machine and pre-tighten it. Move the axes so that the special electrode is close to the reference plane parallel to the X-axis direction. Manually adjust the guide angle so that its projection line on the XY plane is parallel to the reference plane. After locking the guide, pass the electrode wire upward from the guide outlet and tighten it to the clamping can.

[0031] The device is then moved according to the calculated two angular components of the five-axis air film hole. The actual swing axis angle is equal to the calculated angle minus the 30° bend angle of the dedicated elbow guide. The electrode wire is visually aligned with the punch mark, the distance from the guide to the part is adjusted, and the drilling parameters are called to complete the φ0.4 bottom hole.

[0032] After completing the processing of all the air film bottom holes, remove the fixture together with the parts from the small hole machine and install it on the EDM machine, straighten the long side of the fixture parallel to the X-axis direction of the equipment.

[0033] Install the φ0.7 eccentric electrode holder and electrode on the equipment, adjust the C axis of the equipment so that the eccentric direction is parallel to the Y axis, and straighten the electrode in the X and Y directions so that the Z-direction runout is less than 0.02.

[0034] Use a special electrode to align the base disc of the part fixture and align its upper end face, and clear the X, Y, and Z axes.

[0035] According to the coordinate values obtained previously, the electrode is aligned with the φ0.4 bottom hole on the part and EDM forming drilling is performed.

[0036] In the above-described embodiments, electrode design plays a key role. The electrode in the EDM hole punching machine adopts a curved design with a 30° bend angle, effectively preventing interference between the electrode and the blade edge during machining. The electrode in the EDM die-casting machine is designed to be parallel to the direction of motion, avoiding interference with the blade edge through parallel switching. These designs not only improve machining safety and reliability, but also significantly enhance machining efficiency. By optimizing machining parameters, the EDM hole punching machine achieves efficient material removal during the rough machining phase, while the EDM die-casting machine ensures controllable remelting layer thickness during the fine machining phase, meeting design requirements. Furthermore, embodiments of the present invention also address the need for mass production of interference holes and shielding holes for turbine blade film holes. The above-described process route and operational steps enable high-precision film hole machining while significantly improving machining efficiency. For example, in mass production, structured light scanning can be used to acquire point cloud data and calculate actual position, enabling rapid positioning. Dedicated electrode design and optimized parameters can shorten machining time and ensure high machining quality. These technical approaches collectively constitute the core advantages of the present invention, resolving interference issues existing in the prior art while simultaneously meeting both design and production requirements. In summary, the present invention achieves efficient and accurate preparation of turbine blade air film hole interference hole shielding hole through precise positioning, dedicated electrode design and parameter optimization. Figure 1 and attached Figure 2 The electrode structure design shown in the figure, the technical solution of the present invention has high practicality and promotion value, and can be widely used in the fields of aircraft engine and gas turbine manufacturing. Example

[0037] This embodiment is a method for preparing φ1.3 interference film holes on triple turbine guide blades. The specific steps are as follows: 1. Determine the actual position and normal vector of the blade film hole on the fixture QB377-0157.

[0038] The original coordinates (theoretical position) and vectors of the air film hole are as follows:

[0039] The blade is scanned and measured on the blue light camera measurement device to obtain the actual point cloud model of the blade. The actual point cloud model is aligned with the theoretical model of the blade body, and the rotation matrix and translation vector of the blade position on the fixture relative to the theoretical model are obtained as follows:

[0040] Right now: x0=-0.2076, y0=0.5519, z0=-0.66, ix=0.9996, jx=-0.0179, kx=0.012, iy=0.0176, jy=0.9997, ky=-0.014, iz=-0.0124, jz=0.0139, kz=1, According to the calculation formula of the air film hole position: x′=(x-x0)·ix+(y-y0)·jx+(z-z0)·kx, y′=(x-x0)·iy+(y-y0)·jy+(z-z0)·ky, z′=(x-x0)·iz+(y-y0)·jz+(z-z0)·kz.

[0041] Calculated x′=139.6606, y′=-39.044, z′=86.02767 Therefore, on the fixture QB377-0157, the actual position coordinates and vector direction of the air film hole are as follows:

[0042] The five-axis coordinate values of the Zhonggu high-speed small hole machine are as follows:

[0043] 2. Make dot marks on the Zhonggu high-speed small hole machine according to the above coordinates.

[0044] Install the fixture on the small hole machine and align and tighten it. Install the φ0.4 standard guide and electrode wire. Perform tool alignment on the fixture inner hole and the worktable surface. Then, according to the following process parameters, mark each previously determined air film hole position with a depth of no more than 0.5mm in the basic coordinate system. The drilling parameters are as follows:

[0045] 3. Remove the standard guide from the equipment and install the φ0.7 special electrode guide on the W axis of the small hole machine and pre-tighten it. Move each axis so that the special electrode is close to the reference plane parallel to the X axis direction. Manually adjust the guide angle so that its projection line on the XY plane is parallel to the reference plane. After locking the guide, pass the electrode wire upward from the guide outlet and tighten it to the clamping can.

[0046] Set the B-axis angle of the machine to 40.48485 degrees and the C-axis angle to 165.2142 degrees, visually align the electrode wire to the punch mark, adjust the distance from the guide to the part, and call the following punching parameters to complete the φ0.7 bottom hole processing.

[0047]

[0048] 4. Remove the fixture together with the parts from the small hole machine and install it on the Dimoncat EDM machine, straighten the long side of the fixture parallel to the X-axis direction of the equipment.

[0049] Install the φ1.3 eccentric electrode holder and electrode on the equipment, adjust the C axis of the equipment so that the eccentric direction is parallel to the Y axis, and straighten the electrode in the X and Y directions so that the Z-direction runout is less than 0.02.

[0050] Adjust the B-axis angle of the Dimoncat EDM equipment to 70.48485185 degrees and the A-axis angle to 194.7858479 degrees.

[0051] Insert a plug gauge into the bottom hole of the φ0.7 air film hole. Align the center of the plug gauge with the forming machine electrode. Set the X and Y axes to 0 and remove the plug gauge. Perform EDM drilling using the parameters in the table below.

[0052]

[0053] The diameter, angle and position of the air film holes meet the design requirements. Example

[0054] This embodiment is a method for preparing φ1.1 interference film holes on turbine guide blades, and the specific steps are as follows: 1. Determine the actual position and normal vector of the blade film hole on the fixture QB377-0142.

[0055] The original coordinates (theoretical position) and vectors of the air film hole are as follows:

[0056] The blade is scanned and measured on the blue light camera measurement device to obtain the actual point cloud model of the blade. The actual point cloud model is aligned with the theoretical model of the blade body, and the rotation matrix and translation vector of the blade position on the fixture relative to the theoretical model are obtained as follows:

[0057] That is, According to the calculation formula of the air film hole position: x′=(x-x0)·ix+(y-y0)·jx+(z-z0)·kx, y′=(x-x0)·iy+(y-y0)·jy+(z-z0)·ky, z′=(x-x0)·iz+(y-y0)·jz+(z-z0)·kz.

[0058] Calculated x′=16.96856, y′=-60.3004, z′=85.9198 Therefore, on the fixture QB377-0142, the actual position coordinates and vector direction of the air film hole are as follows:

[0059] The five-axis coordinate values of the Zhonggu high-speed small hole machine are as follows:

[0060] 2. Make dot marks on the Zhonggu high-speed small hole machine according to the above coordinates.

[0061] Install the fixture on the small hole machine, align and tighten it. Install the φ0.4 standard guide and electrode wire. Align the tool between the fixture's inner hole and the worktable surface. Then, according to the following process parameters, mark each previously determined air film hole location with a depth no greater than 0.5mm in the basic coordinate system.

[0062]

[0063] 3. Remove the standard guide from the equipment and install the φ0.7 special electrode guide on the W axis of the small hole machine and pre-tighten it. Move each axis so that the special electrode is close to the reference plane parallel to the X axis direction. Manually adjust the guide angle so that its projection line on the XY plane is parallel to the reference plane. After locking the guide, pass the electrode wire upward from the guide outlet and tighten it to the clamping can.

[0064] Set the B-axis angle of the machine to 42.5176 degrees and the C-axis angle to 178.9741 degrees, visually align the electrode wire to the punch mark, adjust the distance from the guide to the part, and call the following punching parameters to complete the φ0.7 bottom hole processing.

[0065]

[0066] 4. Remove the fixture together with the parts from the small hole machine and install it on the Dimoncat EDM machine, straighten the long side of the fixture parallel to the X-axis direction of the equipment.

[0067] Install the φ1.1 eccentric electrode holder and electrode on the equipment, adjust the C axis of the equipment so that the eccentric direction is parallel to the Y axis, and straighten the electrode in the X and Y directions so that the Z-direction runout is less than 0.02.

[0068] Adjust the B-axis angle of the Dimoncat EDM equipment to 72.5176 degrees and the A-axis angle to 181.0259 degrees.

[0069] Insert a plug gauge into the bottom hole of the φ0.7 air film hole. Align the center of the plug gauge with the forming machine electrode. Set the X and Y axes to 0 and remove the plug gauge. Perform EDM drilling using the parameters in the table below.

[0070]

[0071] The diameter, angle and position of the air film holes meet the design requirements.

Claims

1. A precise preparation method for interference film holes on turbine blades, characterized in that: The following steps are involved: S1: Precisely position the turbine blades by using a structured light scanner to obtain actual model point cloud data and calculate the deviation between the theoretical position and the actual position using the closest point iterative closest point algorithm; S2: Calculate the actual position of each air film hole based on the translation and rotation matrix; S3: Based on the principle of aligning the air film hole vector with the Z axis of the device, calculate the five-axis decomposition coordinates of the air film hole drilling position; S4: Install the fixture on the EDM small hole machine and align and tighten it to complete the bottom hole processing; S5: Install the parts with completed bottom hole processing on the EDM machine to complete the final forming process.

2. The method for accurately preparing interference film holes on turbine blades according to claim 1, characterized in that: The translation rotation matrix includes translation vectors x0, y0, z0 and rotation vectors ix, jx, kx, iy, jy, ky, iz, jz, kz.

3. The method for accurately preparing interference film holes on turbine blades according to claim 2, characterized in that: The calculation formula for the actual position of each air film hole is: x′=(x-x0)·ix+(y-y0)·jx+(z-z0)·kx, y′=(x-x0)·iy+(y-y0)·jy+(z-z0)·ky, z′=(x-x0)·iz+(y-y0)·jz+(z-z0)·kz.

4. The method for accurately preparing interference film holes on turbine blades according to claim 1, characterized in that: The electrode of the EDM small hole machine adopts a curved design with a bending angle of 30°. The electrode includes a connector, an outer sleeve, an insulating layer and a guide.

5. The method for accurately preparing interference film holes on turbine blades according to claim 1, characterized in that: The electrode of the electric spark forming machine is designed to be parallel to the movement direction, and the interference with the blade edge plate is avoided through parallel transfer. It includes a guide rod, an eccentric, a clamping bolt and a forming electrode.

6. The method for accurately preparing interference film holes on turbine blades according to claim 1, characterized in that: When the EDM machine is used to process the bottom hole with a depth range of 0 to -6 mm, the process parameters are: pulse width 6-12 gears, pulse interval 10-18 gears, current 3-5 gears, capacitance 2-3 gears, sensitivity 0-2 gears, servo speed 1-3 gears, voltage 50-80 volts, speed 50-300 rpm. When the EDM forming machine is used to prepare air film holes, the process parameters are: pulse width 10-30μs, pulse interval 80-120μs, current 1-3 gears, high voltage 1 gear, servo 4-6 gears, tool lift 1 gear, discharge 3 gears, negative polarity, low pressure 0 gear, and flushing pressure 0.08-0.12MPa.

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