Processing method of high-precision metal airfoil test piece

Abstract

The invention discloses a machining method of a high-precision metal airfoil test piece. The machining method comprises the steps of blank preparation, numerical control milling rough machining, horizontal boring trepanning, numerical control milling machining, heat treatment aging, linear cutting, numerical control milling semi-finish machining, three-coordinate detection, five-axis numerical control milling finish machining, three-coordinate detection and numerical control milling machining. The high-precision requirement of a design drawing can be met, meanwhile, the machining efficiency can be greatly improved, the machining period is shortened, and the machining scheme has been successfully applied to small-batch production of airfoil test pieces at present to be delivered to tests for use.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation mechanical processing, and in particular relates to a processing method for a high-precision metal airfoil test piece. Background Art

[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, and the pressure measuring tube is connected to the surface of the airfoil to carry out a blowing test and obtain the 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 large thickness variation of the airfoil curved surface, the contour error of the curved surface is required 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] There are currently two methods for processing products with similar structures. The first method is to clamp the two ends of a metal blank and complete the shape processing in one go on a five-axis CNC machining device, and then drill three φ10mm through holes with a length of L=840mm inside the airfoil. This is a common processing method, but this processing method cannot meet the design requirements of the profile error and roughness of the airfoil surface. The second method is to use metal 3D printing. Compared with the first method, this processing method has higher processing efficiency and material utilization, but the disadvantage is that the profile error and roughness of the airfoil surface cannot meet the design requirements. Summary of the invention

[0004] The purpose of the present invention is to provide a method for processing a high-precision metal airfoil test piece, which is an efficient processing scheme improved based on numerical control processing and can meet the high dimensional accuracy requirements of the design drawings on the airfoil.

[0005] The present invention provides a method for processing a high-precision metal airfoil test piece, comprising:

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

[0007] 2) On a three-axis CNC milling machine, the blank is subjected to CNC milling rough processing, and the profile of the airfoil is reserved with a first processing allowance, and the profile error is controlled within 0.3 mm; after the rough processing, the part is provided with support frames on both sides along the length direction of the airfoil, and the two ends of the support frame are connected to the connecting parts at both ends of the airfoil, and the middle is connected to the side of the airfoil through a connecting column, and the upper and lower surfaces of the part after the rough processing are also provided with two support bosses respectively;

[0008] 3) Stand the rough-machined part upright along the chord direction and place it on the processing platform of the horizontal boring machine, adjust the upper edge surface of the part to be horizontal, ensure that the flatness error is controlled within 0.02mm, use the upper edge surface as the processing reference surface A, and process 3 φ10mm through holes with a length of 840mm from the connection parts at both ends of the airfoil respectively and connect them;

[0009] 4) Taking the basic surface A as the reference, 8 φ10 (+0.01,0) mounting holes are processed at the connection parts at both ends of the airfoil, M5 threaded holes are processed on the supporting boss, and the cover plate mounting groove and airfoil profile are processed; 1mm is reserved for the airfoil profile and mounting groove for fine processing;

[0010] 5) Heat treatment of the processed parts;

[0011] 6) Using wire cutting to cut off the supporting frame around the part to obtain the airfoil part;

[0012] 7) Place the airfoil part flat on the three-axis CNC equipment processing platform, set a fixed support under the supporting boss, and connect and fix the airfoil part to the fixed support with M5 bolts. Pads are set under the connecting parts at both ends of the airfoil, and a pressure plate is set above. The posture of the part is adjusted based on the two mounting holes at both ends of the connecting part, so that the straightness of the two mounting holes is controlled within 0.02mm. Use CNC milling to process the curved surface shape of the airfoil and the cover plate mounting groove, and reserve the second processing allowance;

[0013] 8) Remove the parts from the three-axis CNC equipment processing platform, use three-coordinate detection to detect the deformation of the part surface, the relative position relationship between the surface and the reference hole, and record the surface detection data;

[0014] 9) Place the airfoil part flat on the processing platform of the five-axis CNC equipment, and use the same clamping method as in step 7), adjust the remaining processing allowance according to the surface detection data, and fine-process the airfoil shape, mounting holes and 99 Φ1.1mm pressure measuring holes;

[0015] 10) Remove the parts from the five-axis CNC equipment processing platform, use three-coordinate measurement to detect the deformation of the part surface, the relative position relationship between the surface and the reference hole, and record the surface detection data;

[0016] 11) If the test data is qualified, the supporting boss is removed and a 0.08mm margin is reserved for grinding. The ground surface is flush with the airfoil surface, and then the through holes, threaded holes and burrs and flanges are manually filed with a file. At the same time, the entire airfoil surface is ground and polished to a surface roughness of Ra0.8.

[0017] Optionally, the heating temperature of the heat treatment aging is 160°C to 200°C, and the insulation time is 5 hours.

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

[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 support boss has a diameter of 30 mm and a height of 7 mm.

[0023] Optionally, before rough machining the blank, the method further comprises:

[0024] The blank is quenched.

[0025] Optionally, the blank is made of S2311 high-strength die steel.

[0026] Optionally, the length, width and height dimensions of the blank are 855×285×36 mm.

[0027] The present invention provides a method for processing high-precision metal airfoil test pieces, which can meet the high-precision requirements of design drawings, and at the same time can greatly improve processing efficiency and shorten processing cycles. Currently, the processing scheme has been successfully applied to small-batch production of airfoil test pieces for delivery for test use. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure is a diagram showing the structure of the airfoil test piece;

[0029] Figure 2 It is the three-view drawing of the airfoil;

[0030] Figure 3 This is the processing flow chart of the airfoil test piece;

[0031] Figure 4 It is a diagram of the blank;

[0032] Figure 5 After rough machining Figure 1 ;

[0033] Figure 6 After rough machining Figure 2 ;

[0034] Figure 7 This is a diagram of the part after horizontal boring;

[0035] Figure 8 This is a diagram of parts after CNC machining;

[0036] Fig. 9This is a diagram of the parts before wire cutting;

[0037] Fig.10 This is a diagram of the parts after wire cutting;

[0038] Fig.11 Clamping of airfoil parts Figure 1 ;

[0039] Fig.12 Clamping of airfoil parts Figure 2 ;

[0040] Fig.13 This is a diagram of a fixed support. DETAILED DESCRIPTION

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

[0042] For example, the airfoil test piece structure to be processed in the present invention is as follows: Figure 1 As shown in the figure, its overall dimensions are 840×210×19.7mm in length×width×height respectively. 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 1mm is arranged in three holes inside the airfoil. The pressure measuring tube is connected to the surface of the airfoil to carry out a wind blowing test and obtain the 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 curved surface is 19.7mm, the thickness of the thinnest point is 0.84mm, the contour error of the curved surface is required to be controlled within 0.03mm, and the surface roughness is required to be Ra0.8. There are also three φ10mm through holes with a length of L=840mm inside for installing pressure measuring tubes.

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

[0044] Step 1: Determine the complete processing flow of the airfoil test piece

[0045] Step 2: For the airfoil parts that are the most difficult to process, we creatively developed an efficient and reliable processing plan and designed the corresponding auxiliary tooling. The specific processing process is as follows:

[0046] Blank preparation → CNC milling rough machining → horizontal boring and opening → CNC milling → heat treatment and aging → wire cutting → CNC milling semi-finishing → three-coordinate inspection → five-axis CNC milling finishing → three-coordinate inspection → CNC milling.

[0047] 1) Billet preparation

[0048] According to the required dimensions of the airfoil drawing, a blank with an outer dimension of 855×285×36mm was prepared. The dimension includes the allowance to be processed. The material used is S2311 high-strength die steel. The material has been quenched in the blank state and has good rigidity and strength, which can effectively reduce the deformation of parts during the processing process.

[0049] 2) CNC milling rough processing

[0050] Rough machining is performed on CNC milling machines. The shape of the parts after rough machining is as follows Figure 5 , Figure 6 As shown, the wing-shaped part has a 2mm machining allowance reserved for its profile, and the profile error is controlled within 0.3mm. After machining, the solid body is provided with a support frame around it, and a support boss is provided in the middle. The boss has a diameter of 30mm and a height of 7mm. There are 4 bosses on the front and back sides. The main functions of the support frame are:

[0051] a. Since the airfoil is relatively long, reaching 840mm in length and with a maximum thickness of only 19.7mm, the rigidity is insufficient. Adding a support frame plays a role in fixing and strengthening, increasing rigidity, and preventing deformation during processing;

[0052] b. The support frame can be used as a clamping chuck, which can be clamped and fixed on the CNC machining platform to facilitate CNC machining.

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

[0054] 3) Horizontal boring

[0055] Will Figure 6 The parts after medium and rough processing are placed upright on the processing platform of the horizontal boring machine. The support frames on both sides are clamped with a clamping fixture, and the upper edge surface 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 processing reference surface A, and three φ10mm through holes with a length of L=840mm are processed from the left and right sides respectively.

[0056] 4) CNC milling

[0057] Taking basic surface A as reference, 8-φ10 (+0.01, 0) hole, cover plate mounting groove and airfoil profile are processed respectively, and 4-M5 threaded hole is processed on the supporting boss. Among them, 8-φ10 (+0.01, 0) hole is processed as 8-φ8H7, and 1mm is reserved for airfoil profile and mounting groove for fine processing.

[0058] 5) Heat treatment aging

[0059] The parts after the above processing are subjected to heat treatment aging, the heating temperature is 160℃~200℃, and the holding time is 5h. The purpose of heat treatment aging is to eliminate the residual mechanical processing 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 parts.

[0060] 6) Wire cutting

[0061] The wire cutting process removes the supporting frame around the part. The parts before and after processing are as follows: Fig. 9 shown.

[0062] 7) CNC milling semi-finishing

[0063] Press the airfoil Fig.11 , Fig.12 The method shown is clamped and fixed on the CNC equipment processing platform, and the airfoil is connected and fixed to the fixed support with two M5 bolts. The two φ8H7 at both ends of the part are used as the reference, and the posture of the part is adjusted to control the straightness of the two φ8H7 reference holes within 0.02mm, and then the pressure plate is used to press Fig.12 The four positions shown are clamped and fixed, and the airfoil curved surface shape and cover plate mounting groove are processed by CNC milling, leaving a processing allowance of 0.5 mm.

[0064] 8) Three-coordinate detection

[0065] The three-coordinate system detects the deformation of the part surface and the relative position relationship between the surface and the reference hole, and records the surface detection data.

[0066] 9) Five-axis CNC milling finishing

[0067] Install the part on the processing platform again according to the clamping method shown in step 7, adjust the remaining processing allowance according to the three-coordinate detection data, and fine-process the airfoil shape, 8-φ10 (+0.01,0) holes and 99 Φ1.1 pressure measuring holes to achieve the final state.

[0068] 10) Three-coordinate detection

[0069] The three-coordinate system detects the deformation of the part surface and the relative position relationship between the surface and the reference hole, and records the surface detection data.

[0070] 11) CNC milling

[0071] After the inspection data is qualified, the 4-Φ30 boss is removed and a 0.08mm margin is reserved for grinding to ensure that the surface is flush with the airfoil surface. Then, the through holes, threaded holes and burrs and flanging around the periphery are manually repaired with a file. The 0.08mm margin reserved at the 4-Φ30 boss is manually ground and polished until it has a smooth transition with the profile surface. At the same time, the entire airfoil surface is ground and polished to a surface roughness of Ra0.8.

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

[0073] The tools and processing parameters used in the CNC machining process are as follows:

[0074]

Claims

1. A method for processing a high-precision metal airfoil test piece, characterized in that: include: 1) Prepare the blank according to the required dimensions and machining allowance of the airfoil drawing; 2) On a three-axis CNC milling machine, the blank is subjected to CNC milling rough processing, and the profile of the airfoil is reserved with a first processing allowance, and the profile error is controlled within 0.3 mm; after the rough processing, the part is provided with support frames on both sides along the length direction of the airfoil, and the two ends of the support frame are connected to the connecting parts at both ends of the airfoil, and the middle is connected to the side of the airfoil through a connecting column, and the upper and lower surfaces of the part after the rough processing are also provided with two support bosses respectively; 3) Stand the rough-machined part upright along the chord direction and place it on the processing platform of the horizontal boring machine, adjust the upper edge surface of the part to be horizontal, ensure that the flatness error is controlled within 0.02mm, use the upper edge surface as the processing reference surface A, and process 3 φ10mm through holes with a length of 840mm from the connection parts at both ends of the airfoil respectively and connect them; 4) Taking the basic surface A as the reference, 8 φ10 (+0.01,0) mounting holes are processed at the connection parts at both ends of the airfoil, M5 threaded holes are processed on the supporting boss, and the cover plate mounting groove and airfoil profile are processed; 1mm is reserved for the airfoil profile and mounting groove for fine processing; 5) Heat treatment of the processed parts; 6) Using wire cutting to cut off the supporting frame around the part to obtain the airfoil part; 7) Place the airfoil part flat on the three-axis CNC equipment processing platform, set a fixed support under the supporting boss, and connect and fix the airfoil part to the fixed support with M5 bolts. Pads are set under the connecting parts at both ends of the airfoil, and a pressure plate is set above. The posture of the part is adjusted based on the two mounting holes at both ends of the connecting part, so that the straightness of the two mounting holes is controlled within 0.02mm. Use CNC milling to process the curved surface shape of the airfoil and the cover plate mounting groove, and reserve the second processing allowance; 8) Remove the parts from the three-axis CNC equipment processing platform, use three-coordinate detection to detect the deformation of the part surface, the relative position relationship between the surface and the reference hole, and record the surface detection data; 9) Place the airfoil part flat on the processing platform of the five-axis CNC equipment, and use the same clamping method as in step 7), adjust the remaining processing allowance according to the surface detection data, and fine-process the airfoil shape, mounting holes and 99 Φ1.1mm pressure measuring holes; 10) Remove the parts from the five-axis CNC equipment processing platform, use three-coordinate measurement to detect the deformation of the part surface, the relative position relationship between the surface and the reference hole, and record the surface detection data; 11) If the test data is qualified, the supporting boss is removed and a 0.08mm margin is reserved for grinding. The ground surface is flush with the airfoil surface, and then the through holes, threaded holes and burrs and flanges are manually filed with a file. At the same time, the entire airfoil surface is ground and polished to a surface roughness of Ra0.

8.

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

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

4. The method for processing a high-precision metal airfoil test piece 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 method for processing a high-precision metal airfoil test piece according to claim 1, characterized in that: The support boss has a diameter of 30 mm and a height of 7 mm.

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

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

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

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