A high-precision metal airfoil test piece processing method

Abstract

The application discloses a processing method of a high-precision metal airfoil test piece, which comprises the following steps: blank preparation, numerical control rough milling, horizontal boring hole opening, numerical control milling, heat treatment aging, wire cutting, numerical control semi-finishing milling, three-coordinate detection, five-axis numerical control finishing milling, three-coordinate detection and numerical control milling. The processing method can meet the high-precision requirement of design drawings, greatly improve the processing efficiency, shorten the processing period, and has been successfully applied to small-batch production of airfoil test pieces, and the airfoil test pieces are delivered for test use.

Description

Technical Field

[0001] This invention belongs to the field of aerospace mechanical processing technology, specifically relating to a processing method for high-precision metal airfoil test pieces. Background Technology

[0002] The structure of the airfoil test piece is as follows Figure 1 As shown, it consists of an airfoil, an upper cover plate, a lower cover plate, and a pressure measuring tube. A stainless steel pressure measuring tube with an outer diameter of 1 mm is arranged in three holes inside the airfoil. The pressure measuring tube is connected to the surface of the airfoil and is used to carry out wind tests to obtain test parameters at various positions on the airfoil surface. The processing difficulty of the airfoil test piece is that the dimensional accuracy requirements of the airfoil are high, the thickness variation of the airfoil surface is large, the contour error of the surface needs to be controlled within 0.03 mm, and the surface roughness requirement is Ra0.8. There are also three φ10 mm through holes with a length of L = 840 mm inside for installing the pressure measuring tube.

[0003] Currently, there are two methods for processing products with similar structures. The first method involves clamping the metal blank at both ends and machining the outer shape in one go using a five-axis CNC machining equipment. Then, three φ10mm through holes with a length of L=840mm are drilled inside the airfoil. This is a common processing method, but it cannot meet the design requirements for the contour error and roughness of the airfoil surface. The second method is to use metal 3D printing. Compared with the first method, this method has higher processing efficiency and higher material utilization. The disadvantage is that the contour error and roughness of the airfoil surface cannot meet the design requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a high-precision machining method for metal airfoil test pieces. This machining method is an efficient machining scheme based on CNC machining improvements, which can meet the high dimensional accuracy requirements of the airfoil parts in the design drawings.

[0005] This invention provides a method for processing high-precision metal airfoil test pieces, comprising:

[0006] 1) Prepare the blank according to the dimensions and machining allowance required by the airfoil drawing;

[0007] 2) On a three-axis CNC milling machine, the blank is rough-machined by CNC milling. The airfoil has a first machining allowance and the surface error is controlled within 0.3mm. After rough machining, the part is provided with support frames on both sides along the length of the airfoil. The two ends of the support frames are connected to the two ends of the airfoil. The middle part is connected to the side of the airfoil through a connecting column. The upper and lower surfaces of the part after rough machining are also provided with two support bosses respectively.

[0008] 3) Place the rough-machined part upright along the chord direction on the machining platform of the horizontal boring machine. Adjust the upper edge of the part to be horizontal and ensure that the flatness error is controlled within 0.02mm. Use the upper edge as the machining reference surface A. Machin three φ10mm through holes with a length of 840mm from the connection part at both ends of the airfoil and connect them.

[0009] 4) Using the basic plane A as the reference, machine 8 φ10 (+0.01,0) mounting holes at the connection parts at both ends of the airfoil, machine M5 threaded holes on the support boss, machine the cover plate mounting groove and airfoil profile; leave 1mm for finishing of the airfoil profile and mounting groove;

[0010] 5) Perform heat treatment aging on the machined parts;

[0011] 6) The supporting frame around the part is removed by wire cutting to obtain the airfoil part;

[0012] 7) Place the airfoil part flat on the machining platform of the three-axis CNC machine. A fixed column is set under the support boss, and the airfoil part is connected and fixed to the fixed column with M5 bolts. A pad is set below the connecting part at both ends of the airfoil, and a pressure plate is set above it. Using the two mounting holes at both ends of the connecting part as a reference, adjust the posture of the part so that the straightness of the two mounting holes is controlled within 0.02mm. Use CNC milling to machine the curved surface of the airfoil and the cover plate mounting groove, leaving a second machining allowance.

[0013] 8) Remove the part from the machining platform of the three-axis CNC machine, use a three-coordinate measuring machine to detect the deformation of the part's surface and the relative positional relationship between the surface and the reference hole, and record the surface detection data;

[0014] 9) Place the airfoil part flat on the machining platform of the five-axis CNC machine, and use the same clamping method as in step 7). Adjust the remaining machining allowance according to the surface inspection data, and finish machine the airfoil shape, mounting holes and 99 Φ1.1mm pressure measuring holes.

[0015] 10) Remove the part from the five-axis CNC machining platform, use a three-coordinate measuring machine to detect the deformation of the part's surface and the relative positional relationship between the surface and the reference hole, and record the surface detection data;

[0016] 11) If the test data is qualified, process and remove the support boss, leave a 0.08mm margin for grinding, and make the ground surface flush with the airfoil surface. Then, use a file to manually file all through holes, threaded holes and burrs and flanges around the perimeter. At the same time, grind and polish the entire airfoil surface to make the surface roughness Ra0.8.

[0017] Optionally, the heating temperature for heat treatment aging is 160℃~200℃, and the holding time is 5h.

[0018] Optionally, the first machining allowance is 2mm and the second machining allowance is 0.5mm.

[0019] Optionally, the cutting depth of the tool in steps 2)-4) is 0.5 mm;

[0020] The cutting depth of the tool in step 7) is 0.2 mm;

[0021] The cutting depth of the tool in step 9) is 0.2 mm.

[0022] Optionally, the diameter of the support boss is 30mm and the height is 7mm.

[0023] Optionally, before rough machining of the billet, the method further includes:

[0024] The blank is quenched.

[0025] Optionally, the billet can be made of S2311 high-strength mold steel.

[0026] Optionally, the blank dimensions are 855×285×36mm.

[0027] This invention provides a processing method for high-precision metal airfoil test pieces, which can meet the high-precision requirements of design drawings, while significantly improving processing efficiency and shortening the processing cycle. This processing scheme has been successfully applied to produce airfoil test pieces in small batches and delivered for testing. Attached Figure Description

[0028] Figure 1 This is a diagram showing the structural composition of the airfoil test specimen;

[0029] Figure 2 Three-view diagram of the airfoil;

[0030] Figure 3 Flowchart of airfoil test piece fabrication;

[0031] Figure 4 A diagram of the billet;

[0032] Figure 5 For rough processing Figure 1 ;

[0033] Figure 6 For rough processing Figure 2 ;

[0034] Figure 7 A diagram of the part after drilling with a horizontal boring machine;

[0035] Figure 8 A diagram showing the part after CNC machining;

[0036] Figure 9This is a diagram of the part before wire EDM.

[0037] Figure 10 This is a diagram of the part after wire cutting;

[0038] Figure 11 Clamping of airfoil components Figure 1 ;

[0039] Figure 12 Clamping of airfoil components Figure 2 ;

[0040] Figure 13 This is a diagram illustrating a fixed support pillar. Detailed Implementation

[0041] The processing method of the high-precision metal airfoil test piece provided by the present invention will be explained below with reference to the accompanying drawings.

[0042] For example, the airfoil test specimen structure to be processed in this invention is as follows: Figure 1 As shown, its external dimensions (length × width × height) are 840 × 210 × 19.7 mm. The airfoil test piece consists of an airfoil, an upper cover plate, a lower cover plate, and a pressure measuring tube. A stainless steel pressure measuring tube with an outer diameter of 1 mm is arranged in three holes inside the airfoil. The pressure measuring tube is connected to the surface of the airfoil for conducting wind tests and obtaining test parameters at various positions on the airfoil surface. The difficulty in processing the airfoil test piece lies in the high dimensional accuracy requirements of the airfoil. The maximum thickness of the airfoil surface is 19.7 mm, the thinnest point thickness is 0.84 mm, the contour error of the surface needs to be controlled within 0.03 mm, and the surface roughness requirement is Ra0.8. There are also three φ10 mm through holes with a length of L = 840 mm inside for installing the pressure measuring tube.

[0043] The technical solution of the high-precision metal airfoil test piece processing method provided by the present invention includes the following:

[0044] Step 1: Determine the complete machining process for the airfoil test piece.

[0045] Step Two: For the airfoil component, which is the most difficult to process, an efficient and reliable processing plan was creatively developed, and corresponding auxiliary tooling was designed. The specific processing flow is as follows:

[0046] Blank preparation → CNC milling roughing → horizontal boring → CNC milling → heat treatment and aging → wire cutting → CNC milling semi-finishing → coordinate measuring machine inspection → five-axis CNC milling finishing → coordinate measuring machine inspection → CNC milling.

[0047] 1) Billet preparation

[0048] Based on the dimensions required by the airfoil drawing, a blank with external dimensions of 855×285×36mm was prepared. This dimension includes the allowance to be processed. The material selected is S2311 high-strength mold steel. The material has been quenched in the blank state, which has good rigidity and strength and can effectively reduce the deformation of the parts during the processing.

[0049] 2) CNC milling roughing

[0050] Rough machining is performed on a CNC milling machine. The shape of the part after rough machining is as follows: Figure 5 , Figure 6 As shown, the airfoil has a 2mm machining allowance, and the surface error is controlled within 0.3mm. The machined solid body has a supporting frame around its circumference and a supporting boss in the middle. The boss has a diameter of 30mm and a height of 7mm, with four bosses on both sides. The main function of the supporting frame is:

[0051] a. Due to the long size of the airfoil, reaching 840mm in length and only 19.7mm in maximum thickness, its rigidity is insufficient. Adding a support frame serves to fix and strengthen it, increasing rigidity and preventing deformation during processing.

[0052] b. The support frame can be used as a clamping chuck to be fixed on the CNC machining platform for easy CNC machining.

[0053] The support boss is used in the CNC milling semi / finishing process. An M5 threaded hole needs to be machined in the middle of the boss, mainly for fixing and supporting purposes.

[0054] 3) Horizontal boring machine hole opening

[0055] Will Figure 6 After rough and medium machining, the part is placed upright on the machining platform of the horizontal boring machine. The two supporting frames are clamped with a clamping fixture. The upper edge of the part is adjusted to be horizontal to ensure that the flatness error is controlled within 0.02mm. Then, this surface is used as the machining reference surface A, and three φ10mm through holes with a length of L=840mm are machined from the left and right sides respectively.

[0056] 4) CNC milling

[0057] Based on the basic surface A, machine 8-φ10 (+0.01,0) holes, cover plate mounting groove and airfoil profile respectively, and machine 4-M5 threaded holes on the support boss. Among them, the 8-φ10 (+0.01,0) holes are machined according to 8-φ8H7. The airfoil profile and mounting groove are reserved with 1mm for fine machining.

[0058] 5) Heat treatment aging

[0059] The parts that have been processed are subjected to heat treatment aging at a temperature of 160℃~200℃ for 5 hours. The purpose of heat treatment aging is to eliminate residual mechanical stress inside the parts, so that the parts reach a stable state and no longer deform, in preparation for the subsequent surface finishing of the airfoil.

[0060] 6) Wire EDM

[0061] Wire EDM removes the supporting frame around the perimeter of the part. The parts before and after processing are shown below. Figure 9 As shown.

[0062] 7) CNC milling semi-finishing

[0063] Press the airfoil components Figure 11 , Figure 12 The part is clamped and fixed on the CNC machining platform as shown. Two M5 bolts are used to connect and fix the airfoil to the fixed support. Using the two φ8H7 holes at both ends of the part as references, the part's orientation is adjusted to ensure the straightness of the two φ8H7 reference holes is controlled within 0.02mm. Then, a pressure plate is used to press... Figure 12 The four locations shown are clamped and fixed. The curved surface of the airfoil and the cover plate mounting groove are machined by CNC milling, with a machining allowance of 0.5mm reserved.

[0064] 8) Coordinate Measuring

[0065] The coordinate measuring machine (CMM) is used to detect the deformation of the part's surface and the relative positional relationship between the surface and the reference hole, and the surface detection data is recorded.

[0066] 9) Five-axis CNC milling finishing

[0067] The part is remounted on the machining platform according to the clamping method shown in step 7. The remaining machining allowance is adjusted according to the coordinate measuring machine data. The airfoil shape, 8-φ10 (+0.01,0) holes and 99 Φ1.1 pressure measuring holes are then finished to achieve the final state.

[0068] 10) Coordinate Measuring

[0069] The coordinate measuring machine (CMM) is used to detect the deformation of the part's surface and the relative positional relationship between the surface and the reference hole, and the surface detection data is recorded.

[0070] 11) CNC milling

[0071] After the test data is qualified, the 4-Φ30 bosses are removed by machining, leaving a 0.08mm allowance for grinding to ensure that the surface is flush with the airfoil surface. Then, the through holes, threaded holes and burrs and flanges around the perimeter are manually filed with a file. The 0.08mm allowance left at the 4-Φ30 bosses is manually ground and polished until it is smoothly transitioned with the surface. At the same time, the entire airfoil surface is ground and polished to achieve a surface roughness of Ra0.8.

[0072] After multiple rounds of iterative processing, the optimal tool selection and machining parameter settings were obtained for the airfoil.

[0073] The cutting tools and machining parameters used in CNC machining are as follows:

[0074]

Claims

1. A method for processing high-precision metal airfoil test pieces, characterized in that, include: 1) Prepare the blank according to the dimensions and machining allowance required by the airfoil drawing; 2) On a three-axis CNC milling machine, the blank is rough-machined by CNC milling. The airfoil has a first machining allowance and the surface error is controlled within 0.3mm. After rough machining, the part is provided with support frames on both sides along the length of the airfoil. The two ends of the support frames are connected to the two ends of the airfoil. The middle part is connected to the side of the airfoil through a connecting column. The upper and lower surfaces of the part after rough machining are also provided with two support bosses respectively. 3) Place the rough-machined part upright along the chord direction on the machining platform of the horizontal boring machine. Adjust the upper edge of the part to be horizontal and ensure that the flatness error is controlled within 0.02mm. Use the upper edge as the machining reference surface A. Machin three φ10mm through holes with a length of 840mm from the connection part at both ends of the airfoil and connect them. 4) Using the basic plane A as the reference, machine 8 φ10 (+0.01,0) mounting holes at the connection parts at both ends of the airfoil, machine M5 threaded holes on the support boss, machine the cover plate mounting groove and airfoil profile; leave 1mm for finishing of the airfoil profile and mounting groove; 5) Perform heat treatment aging on the machined parts; 6) The supporting frame around the part is removed by wire cutting to obtain the airfoil part; 7) Place the airfoil part flat on the machining platform of the three-axis CNC machine. A fixed column is set under the support boss, and the airfoil part is connected and fixed to the fixed column with M5 bolts. A pad is set below the connecting part at both ends of the airfoil, and a pressure plate is set above it. Using the two mounting holes at both ends of the connecting part as a reference, adjust the posture of the part so that the straightness of the two mounting holes is controlled within 0.02mm. Use CNC milling to machine the curved surface of the airfoil and the cover plate mounting groove, leaving a second machining allowance. 8) Remove the part from the machining platform of the three-axis CNC machine, use a three-coordinate measuring machine to detect the deformation of the part's surface and the relative positional relationship between the surface and the reference hole, and record the surface detection data; 9) Place the airfoil part flat on the machining platform of the five-axis CNC machine, and use the same clamping method as in step 7). Adjust the remaining machining allowance according to the surface inspection data, and finish machine the airfoil shape, mounting holes and 99 Φ1.1mm pressure measuring holes. 10) Remove the part from the five-axis CNC machining platform, use a three-coordinate measuring machine to detect the deformation of the part's surface and the relative positional relationship between the surface and the reference hole, and record the surface detection data; 11) If the test data is qualified, process and remove the support boss, leave a 0.08mm margin for grinding, and make the ground surface flush with the airfoil surface. Then, use a file to manually file all through holes, threaded holes and burrs and flanges around the perimeter. At the same time, grind and polish the entire airfoil surface to make the surface roughness Ra0.

8.

2. The processing method for high-precision metal airfoil test pieces according to claim 1, characterized in that, The heating temperature for heat treatment aging is 160℃~200℃, and the holding time is 5h.

3. The processing method for high-precision metal airfoil test pieces according to claim 1, characterized in that, The first machining allowance is 2mm, and the second machining allowance is 0.5mm.

4. The processing method for high-precision metal airfoil test pieces according to claim 1, characterized in that, The cutting depth of the tool in steps 2)-4) is 0.5 mm; The cutting depth of the tool in step 7) is 0.2 mm; The cutting depth of the tool in step 9) is 0.2 mm.

5. The processing method for high-precision metal airfoil test pieces according to claim 1, characterized in that, The diameter of the support boss is 30mm and the height is 7mm.

6. The processing method for high-precision metal airfoil test pieces according to claim 1, characterized in that, Before rough machining of the billet, the method further includes: The blank is quenched.

7. The processing method for high-precision metal airfoil test pieces according to claim 1, characterized in that, The blank is made of S2311 high-strength mold steel.

8. The processing method for high-precision metal airfoil test pieces according to claim 1, characterized in that, The dimensions of the blank are 855×285×36mm (length×width×height).

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