Precision machining method for arc-shaped airfoil

Abstract

The invention discloses a precision machining method for an arc-shaped airfoil, and belongs to the technical field of airfoil machining. According to the structure and the material of the airfoil to be formed, a clamping tool is designed and machined, and the tool is used for clamping and supporting the airfoil. And the airfoil and the clamping tool are subjected to trial assembly, and the clamping tool profile which is not tightly matched is optimized according to the trial assembly result. The airfoil is clamped on a clamping tool, then the tool is fixed on a jaw vice, finally the jaw vice is fixed on a cradle of a cradle type five-axis machining center, the rotation and swing directions of the cradle and a turntable are set according to the airfoil structure and process requirements when various sizes are machined, and the airfoil is precisely machined. According to the method for clamping through the tool clamp, the problem that clamping is difficult due to the fact that the outer molded surface of an arc-shaped airfoil product is irregular is solved, after the airfoil and the tool are clamped and fastened, the overall rigidity is high, all molded surfaces are convenient and fast to machine, and the machining precision of the airfoil is greatly improved.

Description

Technical Field

[0001] The invention relates to a method for precisely machining a curved wing surface, and belongs to the technical field of wing surface machining. Background Art

[0002] At present, in the field of aerospace, the manufacturing method of first forming the required metal parts by additive manufacturing and then machining them for precision dimensional processing is becoming more and more widely used. The workpiece blank formed by additive manufacturing has less excess, which reduces the time of subsequent machining, but some complex parts have irregular shapes, such as curved wing surfaces. The workpiece blank formed by additive manufacturing cannot accurately locate the reference when it is machined for precision dimensional processing, and complex surfaces cannot be processed in one go. During the repeated clamping process, the accuracy of some dimensions and symmetry of the workpiece will be affected, resulting in a low pass rate for such products. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, a method for precision machining of a curved wing surface is proposed, by designing a clamping fixture, the wing surface is fixed on the clamping fixture for machining, and the machining accuracy of the wing surface is improved.

[0004] The technical solution of the present invention is:

[0005] A method for precision machining of a curved airfoil, comprising:

[0006] Design and process a clamping tool according to the structure and material of the airfoil to be formed, the tool being used to clamp and support the airfoil;

[0007] Test-fit the wing surface and the clamping fixture, and optimize the clamping fixture profile that is not tightly matched according to the test-fitting result;

[0008] The wing surface is clamped on a clamping fixture, and then the fixture is fixed on a vise, and finally the vise is fixed on a cradle of a cradle-type five-axis machining center. The rotation and swing directions of the cradle and the turntable when machining various dimensions are set according to the wing surface structure and process requirements, and the wing surface is precisely machined.

[0009] Furthermore, the clamping tooling includes a vertical plate, an arc-shaped main structure, and a boss;

[0010] The vertical plate supports the arc-shaped main structure, and the length and width of the vertical plate are the same as the length and width of the lower surface of the arc-shaped main structure;

[0011] The arc-shaped main structure imitates the arc-shaped surface of the airfoil to be formed, and after the airfoil is clamped by the clamping tool, the arc-shaped main structure is closely fitted with the arc-shaped surface of the airfoil to be formed;

[0012] A plurality of threaded holes are provided on the vertical plate for fixing the clamping fixture and the wing surface;

[0013] The boss is located on the side wall of the arc-shaped main structure and is used to limit the wing surface.

[0014] Furthermore, the manufacturing method of the clamping tool is:

[0015] The blank made of forged blank material is used as the fixture, and the blank is processed to the theoretical blank thickness by a common milling machine, and then the arc-shaped main structure is processed by a spherical tool through a vertical three-axis machining center;

[0016] Processing bosses and threaded holes, where the threaded hole processing method is:

[0017] The screw cooperates with the pressure plate to lock the vertical plate. When the screw passes through the pressure plate and is screwed into the threaded hole, the pressure plates will not interfere with the clamping tooling. The setting of the threaded hole position and hole diameter must ensure that the wing surface is evenly stressed during the locking process and the thread has sufficient load-bearing capacity.

[0018] Furthermore, according to the rigidity of the airfoil and the estimated stress deformation after the airfoil is fastened to the clamping fixture, the material hardness of the clamping fixture is selected to be not less than the material hardness of the airfoil.

[0019] Furthermore, the tooling size is minimized while meeting the containment range of the airfoil to be formed.

[0020] Furthermore, the wing surface and the clamping fixture are trial-assembled, and according to the trial-assembly result, the clamping fixture profile that is not tightly matched is optimized, and the specific method is as follows:

[0021] Clamp the wing surface on the clamping fixture, fit the arc surface of the wing surface with the contoured surface of the arc-shaped main structure, observe whether the fitting state is obstructed, and mark the interference area;

[0022] Remove the wing surface, remove the interference area by machining, install the wing surface into the clamping fixture again, lock it with screws and pressure plates, start the machining center to simulate the machining route, observe and record the area where the clamping fixture blocks the machining, stop the trial cutting, remove the wing surface, and then remove the blocked area by machining.

[0023] Furthermore, the rotation and swing directions of the cradle and turntable are set when processing each size. The specific method is as follows:

[0024] Analyze the wing surfaces that need to be machined, the swing angle and swing range of the tool during processing, and select the initial position. The initial position can meet the full coverage of the machine tool forming range during the entire processing process;

[0025] For areas with high dimensional accuracy requirements, the machine tool rotation direction must be selected to ensure that the tool extension length is no more than three times the tool diameter when processing the area;

[0026] For multiple setting schemes that meet the above requirements, select the scheme that satisfies the most processing features after the turntable and cradle are turned over once, so as to reduce the number of product flips during the processing.

[0027] The advantages of the present invention compared with the prior art are:

[0028] (1) The present invention adopts a fixture clamping method to solve the problem of difficulty in clamping due to the irregular outer surface of the curved wing surface product.

[0029] (2) The tooling structure of the present invention fully considers the need to support the product processing surface, ensuring stability and reliability during product processing. It can effectively support the product during processing, ensuring that the product has strong overall rigidity after being clamped and fastened to the tooling.

[0030] (3) The processing scheme formulated by the present invention fully utilizes the processing characteristics of the five-axis machining center, and can ensure that all the precision matching features of the wing surface can be finely processed in one clamping. It can effectively avoid interference between the processing area and the machine tool or tooling, and at the same time ensure that the processing of various surfaces is convenient and fast.

[0031] (4) The wing surface fastening method selected by the present invention takes up little space, is convenient for product loading and unloading, and effectively avoids scratches on the curved surface during fastening through auxiliary gaskets. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0033] Figure 1 This is a flow chart of a method for precision machining of a curved airfoil according to an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of the tooling used for matching with the curved airfoil according to the embodiment of the present invention;

[0035] Figure 3 It is a structural schematic diagram of a clamping tool and a vise for a cradle turntable according to an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of a turntable on a cradle of a machining center according to an embodiment of the present invention;

[0037] Figure 5 This is a schematic structural diagram of a curved airfoil according to an embodiment of the present invention;

[0038] Figure 6 It is a schematic diagram of placing the curved wing surface on the tooling according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0040] The present invention proposes a method for precision machining of a curved wing surface, such as Figure 1 As shown, the following steps are included:

[0041] Step 101: According to the hardness and rigidity of the wing surface to be formed and the magnitude of the force applied during processing, select the tooling material and tooling size that meet the clamping and support requirements.

[0042] When selecting materials, we consider that the product has a long total length and the wing structure has a thin wall thickness. It is easy to deform when subjected to force during processing, and the product has high roughness requirements. If there is a large vibration during processing, it will affect the surface roughness of the product. Therefore, when selecting materials, we need to consider their rigidity so that the product can be given sufficient support during processing. In order to consider economic efficiency, when selecting tooling dimensions, we try to reduce the tooling dimensions as much as possible while meeting the product inclusion range. Under the premise of meeting the rigidity requirements of the product, we reduce the total thickness of the tooling.

[0043] When selecting the material for tooling and determining the thickness of the tooling, it is necessary to consider the stress conditions of the tooling during the actual processing and the stress deformation of the wing surface when it is fastened to the tooling. The hardness of the tooling material should not be less than the hardness of the wing surface. In this embodiment, No. 45 steel is selected.

[0044] Step 102: According to the structure and size of the airfoil to be formed, the basic form of the tooling and the clamping method required in the corresponding machining center are preset.

[0045] The airfoil to be formed is Figure 5 As shown in the figure, the designed tooling shape can provide good support for the wing surface and reduce deformation and vibration caused by the processing process. The clamping method is convenient for personnel to observe and operate, and all processing contents can be completed in one clamping.

[0046] The tooling consists of an arc-shaped body that conforms to the wing surface, threaded holes for clamping, and boss features that limit the product, such as Figure 2As shown, since the main feature of the product is the curved wing surface, it is preferred to use the wing surface as the main support symmetry when designing the tooling. Considering that the wing surface features are irregular, the profiling method is selected for manufacturing. Considering that the product blank is additively manufactured and the surface roughness is relatively long, when designing the profiling fitting range, it is selected to be lower than the wing surface generatrix (that is, the inclusion range is not greater than 50% of the wing surface shape). Considering that when the two small fillet areas on the front side of the curved surface of the product contact with the side wall of the tooling, two horizontal lines can be contacted. The horizontal and vertical directions of the constraint are both standard 90°, so it is most preferred to place the limit boss feature here when making the tooling.

[0047] Step 103: According to the size, precise camber shape and clamping requirements of the wing surface to be formed, the corresponding camber and shape of the tooling are processed and the threaded holes for clamping the workpiece are processed.

[0048] The processed cambered shape needs to be able to produce a tight fit with the arc of the wing surface, and no obvious vibration will occur during the processing. The setting position of the threaded hole can fully fix the wing surface and the tooling, and will not interfere with the work of the machining center during the processing. In this embodiment, the threaded hole size is M12, and the effective depth is 15mm. In order to consider the tightness of the product wing surface and the tooling profiling surface while considering the economy of tooling production, a forged blank is selected as the blank for tooling production, and the blank is processed to the theoretical blank thickness by an ordinary milling machine, and then the cambered surface processing is completed by a spherical tool through a vertical three-axis machining center. This method ensures the contour of the profiling surface and greatly reduces the processing cost. Considering the poor rigidity of the product, in order to avoid product deformation during the processing, the processing range of the tooling profiling surface gives the product wing surface the maximum wrapping and support under the premise of ensuring that there is no interference with the processing.

[0049] The selection of threaded holes, hole positions and hole diameters required for fastening fully considers the following issues:

[0050] 1. When the screw rod cooperates with the pressure plate to lock the product, the operator is convenient for construction. When the operator passes the screw rod through the pressure plate and screws it into the threaded hole, the pressure plates will not interfere with the tooling or product features. When unloading new products, the pressure plate can remain installed on the tooling to avoid repeated operations.

[0051] 2. When the screw rod cooperates with the pressure plate to lock the product, the tightness of the product constraint. The selection of the threaded hole position determines the position and angle of force applied to the product. The selection of the hole position and hole diameter of this tooling can fully ensure that the product is evenly stressed during the locking process and the thread has sufficient load-bearing capacity.

[0052] Step 104: Analyze the test assembly results of the airfoil to be formed and the tooling, and optimize the surfaces with loose fit and obstructed processing;

[0053] After the tooling profiling surface is processed, place the product on the tooling, fit the product wing surface with the tooling profiling surface, and then observe whether the fitting state is blocked and mark the interference area. Remove the product and machine the interference area, then put the wing surface into the tooling again, lock it with the screw and the pressure plate, start the machining center to simulate the machining route, observe and record the area where the tooling blocks the machining, stop the trial cutting, remove the product, and machine the blocked area.

[0054] The tooling can fully fix the wing surface, and all non-processing areas can be supported by the tooling. The tool can feed at an angle that meets the processing requirements, and will not interfere with the measurement of dimensions during the processing. Because the tool size required for some surfaces to be processed is small and the tool rigidity is low, the tool depth length for each surface can be less than 50mm, and the tool will not deform or break during the processing due to insufficient rigidity.

[0055] Step 105: Clamp the wing surface to be formed on the tooling and the cradle of the cradle-type five-axis machining center, and set the rotation and swing directions of the cradle and the turntable when processing various dimensions according to the wing surface structure and process requirements.

[0056] The selection of the rotation direction of the cradle and turntable during the processing is the selection of the product processing plan. It is necessary to take into account the various features to be processed, the operating characteristics of the machine tool, the dimensional accuracy requirements, and the processing efficiency of the product. First, by analyzing the various machined surfaces of the product, the swing angle and swing range of the tool during processing, ensure that the selected initial position can be met, and the machine tool formation range can be fully covered during the entire processing process. Second, for areas with high processing dimensional accuracy, when selecting the machine tool rotation direction, it is necessary to ensure that the tool extension length is no more than three times the tool diameter when processing this area, so as to ensure that the high-precision surface roughness meets the requirements. Third, the selection of the processing plan must try to ensure that more processing features are completed after the turntable and cradle are flipped once, so as to reduce the number of product flips during the processing process.

[0057] The final processing solution is to place the product vertically relative to the turntable after the product and the tooling are fitted and locked. Figure 6 As shown, the tooling is locked by vise clamping, and the cradle is rotated -90° to the initial state of processing. At this time, the processing reference is selected by the front face of the product. During the processing, the turntable is rotated to 0°, 90°, and 180° to complete the processing of various product surfaces. Figure 3 As shown, the turntable on the cradle is Figure 4 shown.

[0058] When processing the curved surface on one side of the wing to be formed, the cradle rotates -90°, and when processing the curved surface on the other side, the cradle rotates -90° and the turntable rotates 180°. When processing the left and right end surfaces, the cradle rotates -90° and the turntable rotates 90°. When processing the wing to be formed in various sizes, the cradle and tooling can ensure that the operator can observe the processing without obstruction.

[0059] Because the tool size required for machining some surfaces is small and the tool rigidity is low, the tool depth required for machining each surface during the machining process can meet the machining needs when it is less than 50mm, and the tool will not deform or break due to insufficient rigidity during the machining process. When machining all surfaces, the cradle and the turntable are located so that the operator will not be blocked from observing the machining situation. For the measurement of small planes on small arc surfaces, a vernier caliper needs to be used with a block gauge for measurement.

[0060] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for precision machining of a curved airfoil, characterized in that: include: Design and process a clamping tool according to the structure and material of the airfoil to be formed, the tool being used to clamp and support the airfoil; Test-fit the wing surface and the clamping fixture, and optimize the clamping fixture profile that is not tightly matched according to the test-fitting result; The wing surface is clamped on a clamping fixture, and then the fixture is fixed on a vise, and finally the vise is fixed on a cradle of a cradle-type five-axis machining center. The rotation and swing directions of the cradle and the turntable when machining various dimensions are set according to the wing surface structure and process requirements, and the wing surface is precisely machined.

2. A method for precision machining of a curved airfoil according to claim 1, characterized in that: The clamping tooling includes a vertical plate, an arc-shaped main structure, and a boss; The vertical plate supports the arc-shaped main structure, and the length and width of the vertical plate are the same as the length and width of the lower surface of the arc-shaped main structure; The arc-shaped main structure imitates the arc-shaped surface of the airfoil to be formed, and after the airfoil is clamped by the clamping tool, the arc-shaped main structure is closely fitted with the arc-shaped surface of the airfoil to be formed; A plurality of threaded holes are provided on the vertical plate for fixing the clamping fixture and the wing surface; The boss is located on the side wall of the arc-shaped main structure and is used to limit the wing surface.

3. A method for precision machining of a curved airfoil according to claim 2, characterized in that: The manufacturing method of the clamping tool is: The blank made of forged blank material is used as the fixture, and the blank is processed to the theoretical blank thickness by a common milling machine, and then the arc-shaped main structure is processed by a spherical tool through a vertical three-axis machining center; Processing bosses and threaded holes, where the threaded hole processing method is: The screw cooperates with the pressure plate to lock the vertical plate. When the screw passes through the pressure plate and is screwed into the threaded hole, the pressure plates will not interfere with the clamping tooling. The setting of the threaded hole position and hole diameter must ensure that the wing surface is evenly stressed during the locking process and the thread has sufficient load-bearing capacity.

4. The method for precision machining of a curved airfoil according to claim 2, characterized in that: According to the rigidity of the wing surface and the estimated stress deformation after the wing surface is fastened to the clamping fixture, the material hardness of the clamping fixture is selected to be no less than the material hardness of the wing surface.

5. The method for precision machining of a curved airfoil according to claim 2, characterized in that: Under the premise of meeting the containment range of the wing surface to be formed, the tooling size should be reduced as much as possible.

6. The method for precision machining of a curved airfoil according to claim 1, characterized in that: The wing surface and the clamping fixture are trial-assembled, and according to the trial-assembly result, the clamping fixture profile that is not tightly matched is optimized, and the specific method is as follows: Clamp the wing surface on the clamping fixture, fit the arc surface of the wing surface with the contoured surface of the arc-shaped main structure, observe whether the fitting state is obstructed, and mark the interference area; Remove the wing surface, remove the interference area by machining, install the wing surface into the clamping fixture again, lock it with screws and pressure plates, start the machining center to simulate the machining route, observe and record the area where the clamping fixture blocks the machining, stop the trial cutting, remove the wing surface, and then remove the blocked area by machining.

7. The method for precision machining of a curved airfoil according to claim 1, characterized in that: To set the rotation and swing direction of the cradle and turntable when processing each size, the specific method is: Analyze the wing surfaces that need to be machined, the swing angle and swing range of the tool during processing, and select the initial position. The initial position can meet the full coverage of the machine tool forming range during the entire processing process; For areas with high dimensional accuracy requirements, the machine tool rotation direction must be selected to ensure that the tool extension length is no more than three times the tool diameter when processing the area; For multiple setting schemes that meet the above requirements, select the scheme that satisfies the most processing features after the turntable and cradle are turned over once, so as to reduce the number of product flips during the processing.

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