Compressor blade numerical control grinding machining method

Abstract

The invention relates to the technical field of blade machining, in particular to a compressor blade numerical control grinding method which comprises the following steps: S1, grinding tool preparation: selecting a cubic boron nitride grinding wheel as a grinding tool, adopting a CBN grinding wheel with the particle size of 60 # in a coarse grinding stage, and adopting a CBN grinding wheel with the particle size of 200 # in a fine grinding stage; the sizes of grinding wheels adopted in the coarse grinding stage and the fine grinding stage are the same; s2, dividing a grinding area; s3, rough grinding machining is conducted, specifically, rough grinding machining is conducted according to the sequence of an air inlet and outlet edge, a basin back edge plate, a blade root, a blade body and a blade root transfer arc; s4, accurate grinding machining is conducted, specifically, accurate grinding machining is conducted according to the sequence of the basin back edge plate, the blade body and the blade root adapter arc; and S5, deformation compensation is conducted, specifically, the deformation amount of the machined blade is measured, and reverse linear compensation is conducted.

Description

Technical Field

[0001] The present invention relates to the technical field of blade processing, and in particular to a numerical control grinding method for compressor blades. Background Art

[0002] Compressor blades, as one of the key components of aircraft engines, operate in harsh environments such as high temperature and high pressure, bearing extremely high loads, and their quality requirements are becoming increasingly stringent. Currently, the main method for precision machining of the blade body and flange surface of aircraft engine compressor blades is precision milling, but CNC milling has the following problems:

[0003] (1) High cost: 3-4 different milling cutters are required for combined processing, and the unit price of the cutters is expensive.

[0004] (2) Large deformation: Milling can easily cause the blade tip to shift, resulting in blade twisting or position deviation.

[0005] (3) Tool change marks: Tool wear compensation is complex during tool change, which can easily produce tool change marks of varying depths, affecting surface quality.

[0006] In recent years, the development of superabrasives (such as CBN grinding wheels) and CNC grinding technology has provided new insights into blade machining. Grinding offers advantages such as high precision, excellent surface quality, and low tool costs. However, the existing technology lacks an efficient grinding method for the entire surface of compressor blades. To address this issue, the present invention proposes a CNC grinding method for compressor blades. Summary of the Invention

[0007] The main purpose of the present invention is to propose a CNC grinding method for compressor blades to solve the problems of high cost, large deformation, and difficult tool control in milling of compressor blades, and to achieve high-precision and low-cost blade forming processing.

[0008] To achieve the above object, the present invention provides a method for numerically controlling the grinding of compressor blades, comprising the following steps:

[0009] S1. Grinding tool preparation: Cubic boron nitride grinding wheels are used as grinding tools. A 60# grit CBN grinding wheel is used for the rough grinding stage, and a 200# grit CBN grinding wheel is used for the fine grinding stage. The grinding wheels used in the rough grinding stage and the fine grinding stage are the same size.

[0010] S2, grinding area division;

[0011] S3, rough grinding: perform rough grinding in the order of intake and exhaust edge, basin back edge plate, blade root, blade body, and blade root transition arc;

[0012] S4, fine grinding: fine grinding is carried out in the order of basin back edge plate, blade body and blade root transition arc;

[0013] S5. Deformation compensation: Measure the deformation of the blade after machining and perform reverse linear compensation.

[0014] Preferably, in the step S3, when rough grinding the inlet and outlet edges, a machining method of from top to bottom, multiple tool paths, and one-way grinding is adopted, the tool axis direction is set to the machine tool Z-axis direction, the cutting depth per layer is 0.03 mm, and the machining allowance is 0.25 mm ± 0.05 mm.

[0015] Preferably, in the step S3, when rough grinding the shroud and backplate edges, a machining method of multiple tool paths, transverse reciprocating grinding, and from outside to inside is adopted, the tool axis forms a side inclination angle of 8° - 10° with respect to the blade body, and the machining allowance is 0.1 mm ± 0.025 mm.

[0016] Preferably, in the step S3, when rough grinding the blade root, a machining method of multiple tool paths and transverse reciprocating grinding is adopted, the tool axis is set to the machine tool Z-axis direction, and the incoming blade body allowance is set as the machining allowance.

[0017] Preferably, in the step S3, when rough grinding the blade body, machining is carried out from the blade tip to the blade root direction, adopting a machining method of multiple tool paths and transverse reciprocating grinding; for the blade face and blade back, a layered and reverse staggered machining method is adopted; the tool axis is set to the machine tool Z-axis direction, and the machining allowance is 0.25 mm ± 0.05 mm.

[0018] Preferably, in the step S3, when rough grinding the blade root transition arc, machining is carried out in a way of from top to bottom and spiral forward grinding, the tool axis is set to the machine tool Z-axis direction, and the machining allowance is set as 0.25 mm ± 0.05 mm.

[0019] Preferably, in the step S4, when finish grinding the shroud and backplate edges, a machining method of transverse reciprocating grinding and from outside to inside is adopted, the tool axis forms a side inclination angle of 8° - 10° with respect to the blade body, and the machining allowance is 0.01 mm ± 0.005 mm.

[0020] Preferably, in the step S4, when finish grinding the blade body, a machining method of multiple tool paths, spiral forward grinding, and from top to bottom is adopted, the tool axis is set to the machine tool Z-axis direction, and the machining allowance is set as 0.01 mm ± 0.005 mm.

[0021] Preferably, in the step S4, when finish grinding the blade root transition arc, a machining method of high-density tool paths, low feed rate, and spiral forward grinding is adopted, the tool axis direction forms a side inclination angle of 3° - 4° with respect to the blade body, and the machining allowance is 0.01 mm ± 0.005 mm.

[0022] Preferably, in the step S5, the steps of deformation compensation include:

[0023] S501. Measure the offset ΔY in the Y direction of the first measurable section at the blade tip using a coordinate measuring machine.

[0024] S502. Measure the Z - direction distance D from the blade tip to the blade root.

[0025] S503. Calculate the compensation angle θ according to the formula tanθ = ΔY / D.

[0026] S504. Perform reverse compensation of the θ angle in the machining coordinate system.

[0027] Due to the adoption of the above - mentioned technical solution, the beneficial effects of the present invention are as follows:

[0028] (1) Tool cost advantage: For traditional CNC milling of the blade body and flange profile of a compressor blade, 3 - 4 types of milling cutters in combination are required, while the CNC grinding method of the present invention only needs 2 grinding wheels of the same size but different grain sizes to complete the processing. In comparison, the average unit cost of the grinding wheel is about 1 / 2 of the cost of the milling cutter, significantly reducing the tool procurement cost.

[0029] (2) Advantage of no tool - joint marks: After CNC milling, tool - joint marks are likely to appear and vary in depth. Too deep marks are not conducive to the subsequent polishing process and are likely to result in residual tool - joint marks after polishing, making the surface quality of the blade unqualified. However, the CNC grinding method of the present invention can effectively eliminate tool - joint marks during the processing, making the surface of the blade body smooth and flat after grinding, without obvious processing marks, providing a good basis for subsequent finishing processes such as polishing, and making it easier to obtain a high - quality blade surface, improving the overall appearance quality and performance of the blade.

[0030] (3) Advantage of beneficial influence of residual stress: CNC milling will generate residual tensile stress on the blade surface, which will reduce the fatigue life of the blade and affect the reliability and durability of the blade during actual operation. In contrast, the residual stress generated on the blade surface after CNC grinding is residual compressive stress, and the residual compressive stress can offset part of the tensile stress generated during the blade operation, thus being beneficial to improving the fatigue life of the blade, enabling the blade to operate more stably and lastingly under harsh working conditions such as high temperature and high pressure, reducing the maintenance and replacement costs caused by fatigue failure of the blade, and improving the safety and reliability of the aero - engine.

[0031] (4) Smaller machining deformation: During the machining process, the stress generated by grinding is smaller than that generated by milling. The smaller grinding stress effectively controls the deformation of the blade during machining, enabling it to more accurately maintain the designed shape and dimensional accuracy. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0033] Figure 1 It is a schematic diagram of blade area division;

[0034] Figure 2 It is a schematic diagram of rough grinding the inlet edge;

[0035] Figure 3 It is a schematic diagram of rough grinding the exhaust edge;

[0036] Figure 4 It is a schematic diagram of rough grinding the basin edge plate;

[0037] Figure 5 It is a schematic diagram of rough grinding the back edge plate;

[0038] Figure 6 It is a schematic diagram of rough grinding the blade root Figure 1 ;

[0039] Figure 7 It is a schematic diagram of rough grinding the blade root Figure 2 ;

[0040] Figure 8 It is a schematic diagram of rough grinding the blade basin of the blade body;

[0041] Figure 9 It is a schematic diagram of rough grinding the blade back of the blade body;

[0042] Figure 10 It is a schematic diagram of rough grinding the blade root transition arc;

[0043] Figure 11 It is a schematic diagram of fine grinding the basin edge plate;

[0044] Figure 12 It is a schematic diagram of fine grinding the back edge plate;

[0045] Figure 13 It is a schematic diagram of fine grinding the blade body;

[0046] Figure 14 It is a schematic diagram of fine grinding the blade root transition arc;

[0047] Figure 15 It is a schematic diagram of reverse linear compensation.

[0048] Explanation of the reference numerals in the drawings: A, blade basin; B, blade back; C, inlet edge; D, exhaust edge; E, blade root transition arc; F, basin edge plate; G, back edge plate. Detailed implementation manners

[0049] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0050] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a certain specific posture (as shown in the accompanying drawings). If this specific posture changes, then the directional indication also changes accordingly.

[0051] As shown in the accompanying drawings, a numerical control grinding method for compressor blades includes the following steps:

[0052] S1. Grinding tool preparation: Select a cubic boron nitride grinding wheel as the grinding tool. Among them, a CBN grinding wheel with a grain size of 60# is used in the rough grinding stage to quickly remove the surplus. A CBN grinding wheel with a grain size of 200# is used in the finish grinding stage to obtain a better surface quality. The grinding wheels used in the rough grinding stage and the finish grinding stage are the same in size except for the different grain sizes, which is convenient for tool modeling and program preparation. When designing the CBN grinding wheels for the rough grinding stage and the finish grinding stage, according to the size characteristics of the blade's suction side, pressure side, inlet and outlet edges, root transition arc, and flange runner surface, a CBN grinding wheel with a size that meets the full-profile grinding of the corresponding blade is designed to ensure the accessibility of polishing in different regions, eliminate the tool mark at the tool change point, reduce the types of tools used, and lower the processing cost.

[0053] S2. Grinding area division; in combination with Figure 1 As shown, the area includes seven processing areas: the suction side A of the blade, the pressure side B of the blade, the inlet edge C, the outlet edge D, the root transition arc E, the flange on the suction side F, and the flange on the pressure side G.

[0054] S3. Rough grinding: The rough grinding is carried out in the order of the inlet and outlet edges, the flanges on the suction and pressure sides, the blade root, the blade body, and the root transition arc;

[0055] S4. Finish grinding: The finish grinding is carried out in the order of the flanges on the suction and pressure sides, the blade body, and the root transition arc;

[0056] S5. Deformation compensation: Measure the deformation amount of the blade after processing and perform reverse linear compensation.

[0057] In combination with Figure 2 、 Figure 3As shown, in the step S3, the allowance of the air inlet and exhaust edges of the blank is usually the largest. To quickly remove the relatively large allowance of the air inlet and exhaust edges, a CBN grinding wheel with a grain size of 60# is selected as the cutting tool. When rough grinding the air inlet and exhaust edges, a machining method of top-down, multiple tool paths, and one-way grinding is adopted. The tool axis direction is set to the Z-axis direction of the machine tool. The cutting depth per layer is 0.03 mm, and the machining allowance is 0.25 mm ± 0.05 mm.

[0058] Combined with Figure 4 and Figure 5 As shown, in the step S3, only simple rough milling has been performed on the flange of the blank, and there is still a relatively large allowance. To prevent the grinding wheel from interfering with the flange when grinding the blade body, a CBN grinding wheel with a grain size of 60# is selected as the cutting tool. When rough grinding the front and back flanges, a machining method of multiple tool paths, transverse reciprocating grinding, and from outside to inside is adopted. To reduce the contact area between the cutting tool and the blade, thereby increasing the grinding force per unit area, the tool axis should be given an appropriate side inclination angle towards the blade body. Specifically, the tool axis forms a side inclination angle of 8° - 10° with respect to the blade body, and the machining allowance is 0.1 mm ± 0.025 mm.

[0059] Combined with Figure 6 and Figure 7 As shown, in the step S3, a relatively large allowance remains in the root part of the blank. Generally, it is larger than the allowance of the blade body part. Therefore, before rough grinding the blade body, the allowance of the root needs to be removed to be close to the allowance of the blade body. A CBN grinding wheel with a grain size of 60# is selected as the cutting tool. Specifically, when rough grinding the root, a machining method of multiple tool paths and transverse reciprocating grinding is adopted. The tool axis is set to the Z-axis direction of the machine tool, and the incoming blade body allowance is set as the machining allowance.

[0060] Combined with Figure 8 and Figure 9 As shown, in the step S3, since the bending moment borne by the root is the largest when machining the tip, which has the greatest impact on the deformation of the blade, when rough grinding the blade body, the machining is carried out from the tip to the root direction. A machining method of multiple tool paths and transverse reciprocating grinding is adopted; for the front and back of the blade, a layered and reverse staggered machining method is used; the tool axis is set to the Z-axis direction of the machine tool, and the machining allowance is 0.25 mm ± 0.05 mm.

[0061] Combined with Figure 10 As shown, in the step S3, when rough grinding the fillet arc of the root, a CBN grinding wheel with a grain size of 60# is selected as the cutting tool, and a machining method of from top to bottom and spiral forward grinding is adopted. The tool axis is set to the Z-axis direction of the machine tool, and the machining allowance is set as 0.25 mm ± 0.05 mm.

[0062] Combined with Figure 11 、 Figure 12As shown, in the step S4, to ensure the machining accuracy and surface quality of the back edge plate of the basin, a CBN grinding wheel with a grit size of 200# is selected as the cutting tool when finely grinding the back edge plate of the basin. The horizontal reciprocating grinding and the machining method from the outside to the inside are adopted. The tool axis should be given an appropriate side inclination angle towards the blade body. Specifically, the side inclination angle formed by the tool axis relative to the blade body is 8° - 10°, and the machining allowance is 0.01mm ± 0.005mm.

[0063] Combined with Figure 13 As shown, in the step S4, to ensure the machining accuracy and surface quality of the blade body, a CBN grinding wheel with a grit size of 200# is selected as the cutting tool when finely grinding the blade body. The multiple tool paths, spiral down grinding, and the machining method from top to bottom are adopted. The tool axis is set in the Z-axis direction of the machine tool, and the machining allowance is set to 0.01mm ± 0.005mm.

[0064] Combined with Figure 14 As shown, in the step S4, to ensure the machining accuracy and surface quality of the fillet at the blade root transition, a CBN grinding wheel with a grit size of 200# is selected as the cutting tool when finely grinding the fillet at the blade root transition. The high-density tool path, low feed rate, and spiral down grinding machining method are adopted. The tool axis should be given an appropriate side inclination angle towards the blade body. Specifically, the side inclination angle formed by the tool axis direction relative to the blade body is 3° - 4°, and the machining allowance is 0.01mm ± 0.005mm. Ensure that the fillet at the blade root transition is smoothly transitioned with the blade body and the edge plate.

[0065] After the grinding process is completed in the above order, use a coordinate measuring machine to measure the positional deviation △X and △Y in the X and Y directions of the first measurable section at the blade tip before fitting. During the grinding process implemented on the basis of zonal grinding, it is found that the deformation mainly concentrates in the Y direction, that is, the offset in the blade pressure side and suction side directions, and there is basically no offset in the X direction. The offset is larger the farther away from the blade root. Therefore, usually only the Y-direction deformation is compensated. It is approximately considered that the deformation distributed along the stacking axis direction of the blade body is linearly variable. Therefore, combined with Figure 15 As shown, in the step S5, the steps of deformation compensation include:

[0066] S501. Use a coordinate measuring machine to measure the offset △Y in the Y direction of the first measurable section at the blade tip;

[0067] S502. Measure the Z-direction distance D from the blade tip to the blade root;

[0068] S503. Calculate the compensation angle θ according to the formula tanθ = △Y / D;

[0069] S504. Perform the reverse compensation of the θ angle in the machining coordinate system.

[0070] In addition, during the manufacturing process of the blade, there will be process bosses. In this embodiment, the grinding object is the blade after the tenon and the rough-milled runner surface of the flange have been processed. To reduce the risk of tool interference, the process bosses are removed before grinding.

[0071] During grinding, install the 3R quick-change tooling base on the A-axis or C-axis workbench of the grinding machine. Clamp the blade on the 3R quick-change tooling. Return each axis of the machine to zero. Correctly clamp the core rod standard part. Press the dial indicator on the core rod standard part. Align the position and perpendicularity of the fixture by dial indicator. The fluctuation of the position is ≤0.02 mm, and the fluctuation of the perpendicularity is ≤0.01 mm. After the mounting rod of the CBN grinding wheel is clamped on the grinding machine, use the dial indicator to confirm that the roundness runout of the mounting rod is ≤0.01 mm.

[0072] When using the CNC grinding method for the compressor blade provided in this embodiment, when programming the grinding program, first perform model optimization. The model optimization uses UG three-dimensional model design software. The processing model is a three-dimensional model obtained by optimizing and adjusting the theoretical model of the blade and then supplementing the correct root fillet and runner surface of the flange according to the design drawing; select the corresponding CBN grinding wheel with appropriate size according to different levels of blades, establish the corresponding tool model, and then copy and divide the entity of the blade theoretical model. Divide the suction side, pressure side, inlet and outlet edges, root fillet, and runner surface of the flange of the blade as the drive surfaces of the corresponding parts. Use the surface drive and multi-axis machining strategy to program the grinding program, optimize the tool path trajectory, and achieve sectional grinding forming.

[0073] The following methods are used to control grinding deformation: The grinding process is a vertical cantilever machining. When machining the tip of the blade far from the clamping end, the root of the blade bears a large bending moment. When machining the root of the blade close to the clamping end, the root of the blade bears a small bending moment. To ensure that the root of the blade has sufficient bending stiffness to resist deformation, machine from the tip to the root; to reduce the grinding stress deformation of the blade, use the method of reverse interleaving and layered machining for grinding; approximate the deformation distributed along the stacking axis as a linear change and perform reverse linear compensation.

[0074] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A numerical control grinding method for a compressor blade, characterized in that It includes the following steps: S1. Grinding tool preparation: Select a cubic boron nitride grinding wheel as the grinding tool. For the rough grinding stage, a CBN grinding wheel with a grit size of 60# is used, and for the finish grinding stage, a CBN grinding wheel with a grit size of 200# is used; the grinding wheel sizes used in the rough grinding stage and the finish grinding stage are the same; S2. Grinding area division; S3. Rough grinding: Perform rough grinding in the order of the intake and exhaust edges, the back edge of the basin, the blade root, the blade body, and the fillet at the blade root transition; S4. Finish grinding: Perform finish grinding in the order of the back edge of the basin, the blade body, and the fillet at the blade root transition; S5. Deformation compensation: Measure the deformation amount of the blade after machining and perform reverse linear compensation.

2. The CNC grinding method for a compressor blade according to claim 1, wherein, In the step S3, when rough grinding the intake and exhaust edges, a machining method of from top to bottom, multiple tool paths, and one-way grinding is adopted. The tool axis direction is set to the Z-axis direction of the machine tool. The cutting depth per layer is 0.03 mm, and the machining allowance is 0.25 mm ± 0.05 mm.

3. The numerical control grinding method for a compressor blade according to claim 1, characterized in that, In the step S3, when rough grinding the back edge of the basin, a machining method of multiple tool paths, transverse reciprocating grinding, and from outside to inside is adopted. The tool axis forms a side inclination angle of 8° - 10° with respect to the blade body, and the machining allowance is 0.1 mm ± 0.025 mm.

4. The numerical control grinding method for a compressor blade according to claim 1, characterized in that In the step S3, when rough grinding the blade root, a machining method of multiple tool paths and transverse reciprocating grinding is adopted. The tool axis is set to the Z-axis direction of the machine tool, and the incoming blade body allowance is set as the machining allowance.

5. A numerical control grinding method for a compressor blade according to claim 1, characterized in that, In the step S3, when rough grinding the blade body, machining is carried out from the blade tip to the blade root direction. A machining method of multiple tool paths and transverse reciprocating grinding is adopted; for the blade concave and blade convex, a layered and reverse staggered machining method is adopted; the tool axis is set to the Z-axis direction of the machine tool, and the machining allowance is 0.25 mm ± 0.05 mm.

6. The CNC grinding method for a compressor blade according to claim 1, wherein, In the step S3, when rough grinding the fillet at the blade root transition, a machining method of from top to bottom and spiral forward grinding is adopted. The tool axis is set to the Z-axis direction of the machine tool, and the machining allowance is set to 0.25 mm ± 0.05 mm.

7. A numerical control grinding method for a compressor blade according to claim 1, characterized in that, In the step S4, when finish grinding the back edge of the basin, a machining method of transverse reciprocating grinding and from outside to inside is adopted. The tool axis forms a side inclination angle of 8° - 10° with respect to the blade body, and the machining allowance is 0.01 mm ± 0.005 mm.

8. The CNC grinding method for a compressor blade according to claim 1, characterized in that, In the step S4, when finish grinding the blade body, a machining method of multiple tool paths, spiral forward grinding, and from top to bottom is adopted. The tool axis is set to the Z-axis direction of the machine tool, and the machining allowance is set to 0.01 mm ± 0.005 mm.

9. A CNC grinding method for a compressor blade as claimed in claim 1, characterized in that, In the step S4, when finish grinding the fillet at the blade root transition, a machining method of high-density tool paths, low feed, and spiral forward grinding is adopted. The tool axis direction forms a side inclination angle of 3° - 4° with respect to the blade body, and the machining allowance is 0.01 mm ± 0.005 mm.

10. A numerical control grinding method for a compressor blade according to claim 1, characterized in that, In the step S5, the steps of deformation compensation include: S501. Use a coordinate measuring machine to measure the offset △Y of the first measurable cross-section at the blade tip in the Y direction; S502. Measure the Z-direction distance D from the blade tip to the blade root; S503. Calculate the compensation angle θ according to the formula tanθ = △Y / D; S504. Perform reverse compensation of the θ angle in the machining coordinate system.

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