A method for processing a thin-wall blade airfoil

Abstract

The application provides a thin-wall blade profile machining method, which can effectively inhibit the machining vibration of thin-wall blades, improve the profile machining efficiency and machining precision, and significantly improve the profile tolerance of the air inlet and outlet edges. The method comprises the following steps: S01, rough milling of the profile part; S02, fine milling of the profile part except the cavity; installing the rough-milled blade on a low-stress clamping fixture; fine milling the upper and lower profiles of the blade respectively, covering a layer of elastic material at the position corresponding to the cavity of the blade when the upper profile of the blade is machined; covering a layer of elastic material at the groove position of the cavity of the blade when the lower profile of the blade is machined, manually attaching the back-arc damping clamping block of the upper profile damping assembly to the back-arc, and pressing the clamping surface one of the inner-arc damping clamping block of the upper profile damping assembly to the two ends of the inner-arc of the blade and pressing the clamping surface two of the inner-arc damping clamping block of the upper profile damping assembly to the elastic material; and S03, fine milling of the blade cavity.

Description

Technical Field

[0001] This invention relates to the field of blade milling technology, specifically a method for machining thin-walled blade profiles. Background Technology

[0002] Thin-walled blades are commonly used in aero engines and gas turbines. Their blade lengths range from 300-1000 mm, with chord lengths of 100-400 mm, while the average thickness of their blade profile is only 1-3 mm. They are characterized by large size, wide chord length, and thin walls, resulting in extremely poor machining rigidity. Figure 1 The image shows the blade profile machining area for thin-walled blades. Figure 2 for Figure 1 Sectional view along the AA direction. Figure 2 The thickness of the hollow inner cavity of the blade at point a is only 1~3mm. During the blade milling process, at the air inlet and outlet edges of the blade (i.e. Figure 1 , 2 The machining vibration is very likely to occur at points B and C, resulting in out-of-tolerance shape and profile, and overcutting of the air inlet and outlet edges due to machining vibration.

[0003] The traditional method for processing this type of blade is to divide the blade base and blade back into two processes, with one side positioned and the other side processed. The advantage of this method is that it has good processing rigidity, but the disadvantage is that processing the blade shape separately will cause the blade shape to be affected by the positioning accuracy, resulting in processing errors, especially the processing error of the air inlet and outlet edge contours of the blade. Summary of the Invention

[0004] To address the issue of vibration affecting machining accuracy in thin-walled blade processing, this invention provides a method for machining thin-walled blade profiles that can effectively suppress vibration during thin-walled blade processing, improve machining efficiency and accuracy, and significantly enhance the profile of the air inlet and outlet edges of the blade surface.

[0005] The technical solution is as follows: a method for machining thin-walled blade profiles, used for machining blades with thin-walled cavities in the middle, characterized by the following steps: S01: rough milling of the blade profile, the machining area includes the complete blade profile and the inner arc cavity of the blade profile; the rough milling method is to rotate and mill along the blade profile contour, and a certain allowance is left after the rough milling is completed;

[0006] S02: Finish milling of the blade portion excluding the cavity; after rough milling, the blade is removed from the rough milling fixture, the machining deformation is released, and it is reinstalled on the low-stress clamping fixture. The finish milling method is to rotate along the blade profile and process it in 2 to 3 layers, gradually machining the allowance left by rough milling to the design size.

[0007] The low-stress clamping fixture includes an upper surface damping component and a lower surface damping component for clamping the upper and lower surfaces of the blade. The upper surface damping component and the lower surface damping component each include an inner arc damping clamping block and a back arc damping clamping block. The clamping surface of the back arc damping clamping block is configured to conform to the back arc surface of the blade. The clamping surfaces at both ends of the inner arc damping clamping block are configured to conform to the inlet and outlet sides of the inner arc surface of the blade. The clamping surface of the inner arc damping clamping block corresponding to the blade cavity position has a certain gap with the blade.

[0008] During precision milling, the upper and lower profiles of the blade are machined separately. When machining the upper profile of the blade, the back arc damping clamping block of the lower profile damping component is manually attached to the back arc. A layer of elastic material is covered at the position corresponding to the blade cavity. The clamping surface one of the inner arc damping clamping block of the lower profile damping component is pressed onto both ends of the inner arc of the blade, and the clamping surface two is pressed onto the elastic material.

[0009] When processing the lower profile of the blade, first manually attach the back arc damping clamping block of the upper profile damping assembly to the back arc, cover the groove position in the blade cavity with a layer of elastic material, press the clamping surface one of the inner arc damping clamping block of the upper profile damping assembly onto both ends of the inner arc of the blade, and press the clamping surface two onto the elastic material.

[0010] S03: Precision milling of blade cavities.

[0011] Preferably, blade rough milling uses a solid carbide rough milling cutter with inserts or a solid carbide cutter with a large radius; blade finish milling uses a solid carbide close-tooth milling cutter with ≥6 cutting edges; and internal cavity finish milling uses a solid carbide milling cutter.

[0012] Preferably, the allowance during rough milling of the blade shape is set to 1~5mm.

[0013] Preferably, the rough milling step distance of the blade profile is controlled within the range of 0.1~0.5mm according to the wave height, and the finish milling step distance of the blade profile is controlled within the range of 0.01~0.5mm according to the wave height.

[0014] Preferably, the cutting parameters for rough milling of the blade profile are set as follows: linear speed Vc = 20~300m / min, cutting amount per tooth Fz = 0.1~0.4mm, and depth of cut 1-5mm; the cutting parameters for finish milling of the blade profile are usually set as follows: linear speed Vc = 20~300m / min, cutting amount per tooth Fz = 0.1~0.4mm, and depth of cut 0.1-0.8mm.

[0015] Preferably, during blade rough milling, the tool and the blade are at a fixed forward tilt angle, which is 5~30°.

[0016] Preferably, during the precision milling of the blade cavity, the blade back arc surface is positioned by a fixture and machined by a milling cutter. During the machining process, the bottom edge and side edge of the milling cutter participate in the cutting simultaneously, with a cutting depth of 3~20mm and a side edge step of 0.5-3mm.

[0017] The beneficial effects of this invention are as follows: When precision milling the blade profile, a special low-stress clamping fixture is used for clamping. This fixture can effectively suppress the problem of machining vibration on the inlet and outlet air edges. At the same time, during the machining process, the blade is divided into upper and lower sections, and the upper and lower sections are machined by rotating along the blade profile contour. The blade head and blade back of the upper or lower section can be machined in one go, avoiding the large machining error of the inlet and outlet air edge contour caused by machining the blade head and blade back separately in the traditional method. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the blade profile machining area for thin-walled blades.

[0019] Figure 2 for Figure 1 A sectional view;

[0020] Figure 3 This is a cross-sectional view of the cutting marks on the surface after blade milling.

[0021] Figure 4 This is a schematic diagram of the milling direction of the profile as provided in this invention;

[0022] Figure 5 This is a cross-sectional view of the lower profile of the blade after it has been clamped by the blade profile machining damping fixture. Detailed Implementation

[0023] A method for machining thin-walled blade profiles, used for machining blades with thin-walled cavities in the middle, includes the following steps: S01: rough milling; the blade is mounted on an A+B type five-axis machining equipment, and a special low-stress rough milling cutter is used to rough machine the blade profile (including the complete blade profile and the inner arc cavity part of the blade profile). The rough milling method is to rotate and mill along the blade profile. After the rough milling is completed, a certain allowance is left. During the machining process, the cutter and the blade profile are at a fixed forward tilt angle. The equipment realizes this machining action through the linkage of five axes: X, Y, Z, A, and B.

[0024] S02: Finish Milling; After rough milling, the blade is removed from the rough milling fixture, the machining deformation is released, and it is reinstalled on a low-stress clamping fixture. The blade body (excluding the cavity area) is then finish milled using a dedicated low-stress finish milling tool. The finish milling method involves rotating along the blade profile (direction such as...). Figure 4 (As shown by the arrow) Through 2 to 3 layers of processing, the allowance left by rough milling is gradually processed to the design size. During finish milling, the blade, blade base, and blade back are processed into shape in one go, which has higher processing accuracy compared to the traditional single-sided processing method.

[0025] Specifically, the low-stress clamping fixture includes an upper profile damping assembly and a lower profile damping assembly for clamping the upper and lower profiles of the blade (upper and lower refer to the two parts of the blade, corresponding to...). Figure 1 When considering the leaf position in a diagram, "up" and "down" can be understood as the front and back halves of the leaf, respectively. Figure 5 As shown, the upper and lower profile damping components include an inner arc damping clamping block 1 and a back arc damping clamping block 2, respectively. The clamping surface of the back arc damping clamping block 2 is contoured to the back arc profile of the blade to maximize the fit between the clamped surface and the tooling. The clamping surfaces at both ends of the inner arc damping clamping block 1 (DE and FG areas) are contoured to the inlet and outlet sides of the inner arc profile of the blade to form a rigid clamping area. The clamping surface 2 of the inner arc damping clamping block corresponding to the blade cavity position (EF area) has a certain gap with the blade to form a flexible clamping area. This area does not directly fit with the blade cavity and is designed with a uniform 2mm gap. This gap is used to fill the elastic film material during use, which plays a role in flexible support and clamping, while avoiding the problem of over-constraint caused by excessive clamping surface leading to blade cross-sectional shape deformation.

[0026] Each of the inner and outer shock-absorbing clamping blocks features a hollow, shell-like design. The clamping blocks have a wall thickness of 3-5mm, are made of lightweight materials, and are manufactured using 3D printing. The total weight is no more than 2kg, ensuring that the weight of the clamp itself does not affect the deformation of the blade profile. Furthermore, the upper and lower profile shock-absorbing components are designed with four through holes for connection and tightening with four screws of corresponding sizes.

[0027] During precision milling, the upper and lower profiles of the blade are machined separately. When machining the upper profile of the blade, the back arc damping clamping block of the lower profile damping component is first manually attached to the back arc. A layer of elastic film material is then covered at the position corresponding to the blade cavity. The clamping surface one of the inner arc damping clamping block of the lower profile damping component is pressed onto both ends of the inner arc of the blade, and the clamping surface two is pressed onto the elastic material.

[0028] When machining the lower profile of the blade, remove the lower profile fixture, first manually attach the back arc damping clamping block of the upper profile damping component to the back arc, cover the groove position of the blade cavity with a layer of elastic film material, press the clamping surface one of the inner arc damping clamping block of the upper profile damping component onto both ends of the inner arc of the blade, and press the clamping surface two onto the elastic material.

[0029] During the machining of the upper and lower surfaces, the other half of the leaf is held by a shock-absorbing fixture, which can effectively improve machining rigidity and solve the problems of machining vibration and overcutting.

[0030] S03: Blade Cavity Precision Milling; The blade's back arc surface is positioned using a fixture, and the hollow inner cavity of the blade is machined using a high-speed milling machine. A dedicated carbide end mill is used for inner cavity milling, and the bottom and side cutting edges participate in the cutting simultaneously through CNC programming. The cutting depth is 3~20mm, with a side cutting edge step of 0.5-3mm to improve cutting efficiency. This method effectively ensures the wall thickness of the thin-walled areas within the inner cavity and improves the machining accuracy. Simultaneously, the back arc positioning method for machining the inner arc significantly improves machining rigidity, increases machining efficiency, and reduces machining deformation.

[0031] In addition, blade rough milling uses insert-type solid carbide rough milling cutters or solid carbide cutters with large radius; blade finish milling uses solid carbide close-tooth milling cutters with ≥6 cutting edges; internal cavity finish milling uses solid carbide milling cutters. Compared with traditional milling cutters, its design features are a larger rake angle and a larger chip groove, which reduces cutting force and improves chip removal capability.

[0032] The allowance during rough milling of blade-shaped parts is set to 1~5mm depending on the deformation of such parts. The allowance should be minimized as much as possible within the allowable deformation range to release residual stress and improve the machining accuracy of subsequent finish milling processes.

[0033] like Figure 3 As shown, the rough milling step distance of the blade profile is controlled within the range of 0.1~0.5mm according to the wave height S, and the finish milling step distance of the blade profile is controlled within the range of 0.01~0.5mm according to the wave height S.

[0034] When rough milling the blade, the cutting parameters are set as follows: linear speed Vc = 20~300m / min, cutting amount per tooth Fz = 0.1~0.4mm, depth of cut 1-5mm; when finish milling the blade, the cutting parameters are usually set as follows: linear speed Vc = 20~300m / min, cutting amount per tooth Fz = 0.1~0.4mm, depth of cut 0.1-0.8mm.

[0035] To avoid overcutting, the machining program, created using dedicated CNC programming software, maintains a fixed forward tilt angle between the tool and the blade during rough milling, ranging from 5 to 30 degrees.

[0036] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A thin-wall blade airfoil machining method for machining a blade having a thin-wall cavity in a middle portion, characterized by, It includes the following steps: S01: Rough milling of the blade profile, the machining area includes the complete blade profile and the inner arc cavity of the blade profile; the rough milling method is to rotate and mill along the blade profile contour, and a certain amount of allowance is left after the rough milling is completed; S02: Finish milling of the blade portion excluding the cavity; after rough milling, the blade is removed from the rough milling fixture, the machining deformation is released, and it is reinstalled on the low-stress clamping fixture. The finish milling method is to rotate along the blade profile and process it in 2 to 3 layers, gradually machining the allowance left by rough milling to the design size. The low-stress clamping fixture includes an upper surface damping component and a lower surface damping component for clamping the upper and lower surfaces of the blade. The upper surface damping component and the lower surface damping component each include an inner arc damping clamping block and a back arc damping clamping block. The clamping surface of the back arc damping clamping block is set in the same shape as the back arc surface of the blade. The clamping surfaces at both ends of the inner arc damping clamping block are set in the same shape as the inlet and outlet sides of the inner arc surface of the blade. The clamping surface of the inner arc damping clamping block corresponding to the blade cavity position has a certain flexible clamping area between it and the blade. This area does not directly fit with the inner cavity of the blade and is designed with a uniform 2mm gap. This gap is used to fill the elastic film material during use, which plays the role of flexible support and clamping, while avoiding the over-constraint caused by excessive pressure surface, resulting in blade cross-sectional shape compression deformation. During precision milling, the upper and lower profiles of the blade are machined separately. When machining the upper profile of the blade, the back arc damping clamping block of the lower profile damping component is manually attached to the back arc. A layer of elastic material is covered at the position corresponding to the blade cavity. The clamping surface one of the inner arc damping clamping block of the lower profile damping component is pressed onto both ends of the inner arc of the blade, and the clamping surface two is pressed onto the elastic material. When processing the lower profile of the blade, first manually attach the back arc damping clamping block of the upper profile damping assembly to the back arc, cover the groove position in the blade cavity with a layer of elastic material, press the clamping surface one of the inner arc damping clamping block of the upper profile damping assembly onto both ends of the inner arc of the blade, and press the clamping surface two onto the elastic material. S03: Precision milling of blade cavities.

2. A method of machining a thin- walled blade profile according to claim 1, characterized in that: For rough milling of the blade shape, use a solid carbide rough milling cutter with inserts or a solid carbide cutter with a large radius; for finish milling of the blade shape, use a solid carbide fine-tooth milling cutter with ≥6 cutting edges; for finish milling of the internal cavity, use a solid carbide milling cutter.

3. A method of machining a thin blade airfoil profile according to claim 2, wherein: The allowance for rough milling of the blade shape is set to 1~5mm.

4. The method for processing thin-walled blade profiles according to claim 3, characterized in that: For rough milling of the blade profile, the step distance is controlled within the range of 0.1~0.5mm for the wave height, and for finish milling of the blade profile, the wave height is controlled within the range of 0.01~0.5mm.

5. The method for processing thin-walled blade profiles according to claim 4, characterized in that: For rough milling of the blade profile, the cutting parameters are set as follows: linear speed Vc = 20~300m / min, cutting amount per tooth Fz = 0.1~0.4mm, and depth of cut 1-5mm; for finish milling of the blade profile, the cutting parameters are set as follows: linear speed Vc = 20~300m / min, cutting amount per tooth Fz = 0.1~0.4mm, and depth of cut 0.1-0.8mm.

6. The method for processing thin-walled blade profiles according to claim 5, characterized in that: During blade rough milling, the tool and blade are at a fixed forward tilt angle, which is 5~30°.

7. The method for processing thin-walled blade profiles according to claim 1, characterized in that: When precision milling the blade cavity, the blade back arc surface is positioned by a fixture and machined by a milling cutter. During the machining process, the bottom edge and side edge of the milling cutter participate in the cutting simultaneously, with a cutting depth of 3~20mm and a side edge step of 0.5-3mm.

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