Aircraft large-curvature carbon fiber composite material wallboard processing method

Abstract

The application provides an aircraft large-curvature carbon fiber composite material wallboard processing method, after an equal-curvature PCD milling cutter is used, the fitting degree of the cutter and the curved surface is obviously improved, the cutting force distribution is more uniform, the residual height processing path is combined, and the profile precision and the surface quality are obviously improved; in terms of side edge processing, the equal-curvature pineapple milling cutter is combined with a micro-inclination shearing cutting and a pre-pressing reinforcement process, the fiber cutting effect is more thorough, the fiber shedding, burr and delamination phenomenon are greatly reduced, and meanwhile, the one-time qualification rate of the part is improved; the self-adaptive processing path reduces the idle stroke and the repair times, effectively improves the cutting speed, and in addition, the service life of the PCD cutter is prolonged.

Description

Technical Field

[0001] This invention relates to the field of processing technology for carbon fiber composite components with large curvature, and particularly to a method for processing carbon fiber composite panels with large curvature for aircraft. Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) composites, with their advantages of high specific strength, high specific modulus, corrosion resistance, and strong design flexibility, have become the preferred material for core load-bearing components in the aerospace field, such as aircraft fuselage panels, wing skins, and tail panels. Among these, aircraft high-curvature CFRP panels (typically referring to curvature radii < 300 mm or overall bending angle > 30°) require five-axis CNC machining after layup and autoclave curing to achieve surface finishing, contour cutting, and side trimming, in order to meet aerospace-grade assembly precision and surface quality requirements.

[0003] Currently, during the machining process, conventional PCD ball end mills / ring end mills are used for profile machining, while carbide or ordinary PCD pineapple end mills are used for side cutting. This is combined with traditional equal-pitch line cutting / helical equal-height machining paths to complete the machining of large-curvature wall panels.

[0004] Current machining techniques suffer from several drawbacks. First, the cutting edge shape doesn't match the variable curvature surface and side profile well, resulting in unstable cutting posture, uneven cutting force distribution, and frequent occurrences of carbon fiber delamination, fiber shedding, burrs, and chipping. Second, surface accuracy and roughness are difficult to guarantee. To mitigate these defects, the feed rate is typically reduced, but this significantly decreases machining efficiency. Third, severe friction between the tool and the composite material leads to rapid wear of the PCD cutting edge, limiting the number of parts that can be machined with a single tool. Fourth, traditional constant-step methods are poorly adapted to variable curvature surfaces, resulting in uneven residual height and frequent overcutting or undercutting in high-curvature areas, requiring multiple reworks. Finally, rigid fixtures don't fit the high-curvature surface well enough, leading to uneven adhesion and unavoidable vibration and clamping deformation during machining, significantly impacting dimensional accuracy and resulting in a low first-pass yield. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a method for processing carbon fiber composite panels with large curvature for aircraft. The method aims to achieve efficient, high-precision, and defect-free processing of carbon fiber panels with large curvature by integrating tool structure customization, path adaptive planning, process parameter optimization, and conformal clamping technology.

[0006] According to an embodiment of the present invention, a method for processing carbon fiber composite panels for aircraft with large curvature includes the following steps: S1. After the wall panel is clamped and positioned, rough machining is performed using a PCD tapered ring milling cutter, followed by stress release. After rough machining, the workpiece is removed from the fixture, left to stand at room temperature to release the machining stress, and then re-clamped for subsequent machining. S2, the stress-relieved wall panel is scanned by the online probe of the machine tool to generate a deviation map, which is used to perform reverse compensation for the subsequent semi-finishing and finishing paths; S3, the wall panel after stress relief is semi-finished using a PCD ring milling cutter with equal curvature. During the semi-finishing process, the machining is carried out according to the adaptive machining path planning based on the curvature partition. S4. The semi-finished wall panel is rough-machined on the side using a PCD pineapple end mill with equal curvature. S5, after rough machining of the side panel, the surface is finished by using a PCD ring milling cutter with equal curvature; S6, after the surface is finished, the side of the wall panel is finished using a PCD pineapple end mill with equal curvature. S7. Inspect the wall panel after the side finishing process. If the inspection result is qualified, the final wall panel is obtained.

[0007] Furthermore, the curvature of the cutting edge arc of the equal curvature PCD ring milling cutter matches the curvature of the corresponding machining area of ​​the wall plate, wherein the rake angle is -5° to 0°, the clearance angle is 15° to 20°, the cutting edge blunting radius is 3μm to 5μm, and a 2 to 4 tooth low helix angle structure is adopted.

[0008] Furthermore, the cutting teeth of the equal curvature PCD pineapple end mill adopt an alternating left and right unequal tooth pitch structure, and the tooth curvature is adapted to the curvature of the side of the wall plate. The sharpness of the PCD cutting edge is controlled at 3μm~5μm, and the tool axis maintains an inclination angle of 1°~2° with the side machining surface to form a shearing cutting.

[0009] Furthermore, in step S3, the panel is divided into three processing areas according to its curvature radius: curvature radius < 100mm, curvature radius between 100mm and 300mm, and curvature radius > 300mm, and milling cutters and processing parameters corresponding to the curvature are matched respectively. The main path adopts streamlined machining with equal residual height, and the tool path is at an angle of 30°~60° to the fiber direction to avoid cutting parallel to the fiber. Dynamic tool posture adjustment: forward tilt angle 10°~30°, side tilt angle 5°~15°, the tilt angle increases synchronously with the increase of curvature, the posture change rate is ≤5° / mm, to avoid cutting force impact caused by sudden posture changes.

[0010] Furthermore, the feed rate for roughing is 1500 mm / min to 1800 mm / min, the feed rate for semi-finishing is 2200 mm / min to 2500 mm / min, the feed rate for surface finishing is 3000 mm / min to 4500 mm / min, and the feed rate for side finishing is 600 mm / min to 800 mm / min.

[0011] Furthermore, in step S1, the processing stress is released by letting the mixture stand at room temperature for 4 to 8 hours.

[0012] Furthermore, step S6 includes the following prior to: Aluminum foil with a thickness of 0.1mm to 0.2mm is pasted on both sides of the workpiece for pre-pressing reinforcement, and then removed after processing to further suppress edge delamination.

[0013] Furthermore, in step S2, the compensation amount is 80% to 90% of the predicted deformation.

[0014] Furthermore, a low-temperature micro-lubrication system is adopted, with a lubricating oil consumption of 5ml / h~20ml / h and a compressed air pressure of 0.5MPa~0.7MPa, which, together with a high-pressure air nozzle, discharges carbon fiber dust in real time.

[0015] This invention provides a method for processing carbon fiber composite panels with high curvature in aircraft. By using a constant curvature PCD end mill, the fit between the tool and the curved surface is significantly improved, and the cutting force distribution is more uniform. Combined with a machining path with constant residual height, the surface accuracy and surface quality are significantly improved. In terms of side processing, the constant curvature pineapple end mill, combined with micro-tilt shearing and pre-compression reinforcement processes, achieves more thorough fiber cutting, significantly reducing fiber shearing, burrs, and delamination, while improving the first-pass yield of parts. The adaptive machining path reduces idle travel and rework frequency, effectively increasing cutting speed. In addition, the service life of the PCD tool is extended. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the implementation of a method for processing large-curvature carbon fiber composite panels for aircraft, as proposed in an embodiment of the present invention.

[0017] The following detailed embodiments will be further described in conjunction with the above-mentioned accompanying drawings. Detailed Implementation

[0018] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0019] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] Example 1 Please see Figure 1 , Figure 1 This is a flowchart illustrating the implementation of a method for processing large-curvature carbon fiber composite panel for aircraft, as proposed in Embodiment 1 of the present invention. The method specifically includes steps S1 to S7, wherein: Step S1: After clamping and positioning the wall panel, rough machining is performed using a PCD tapered ring milling cutter, followed by stress relief.

[0022] Specifically, the workpiece is roughed using a traditional PCD tapered ring milling cutter. After roughing, the workpiece is removed from the fixture and left to stand at room temperature for 4 to 8 hours to release the machining stress before being re-clamped for subsequent machining.

[0023] In this embodiment of the invention, a low-temperature micro-volume lubrication (CMQL) system is employed, with a lubricating oil consumption of 5 ml / h to 20 ml / h and a compressed air pressure of 0.5 MPa to 0.7 MPa. High-pressure air nozzles are used to discharge carbon fiber dust in real time. The low-temperature micro-volume lubrication system is a green cutting and machining cooling and lubrication device that combines low-temperature cold air cutting technology with micro-volume lubrication (MQL) technology. Its core idea is to first cool the compressed air to below 0°C (typically -10°C to -40°C or even lower) through methods such as vortex tubes, energy conversion refrigeration, or vapor compression refrigeration. Then, this low-temperature airflow is mixed with a very small amount of lubricating oil (usually biodegradable vegetable oil, with a consumption of only 0.03 L / h to 0.4 L / h) in an atomizing nozzle to form micron-sized aerosol droplets, which are then sprayed at high speed onto the cutting area between the tool and the workpiece.

[0024] In other embodiments of the present invention, the low-temperature micro-lubrication system can be replaced by low-temperature cold air cutting at -10℃ to 0℃ with an air pressure of 0.6 to 0.8 MPa, to achieve environmentally friendly processing without cutting fluid and avoid thermal softening of the resin matrix.

[0025] In addition, a composite clamping scheme consisting of a silicone vacuum adsorption pad, multi-point adjustable support columns, and edge aluminum alloy pressure strips is adopted during processing: the silicone vacuum adsorption pad is conformally attached to the bottom of the large-curvature wall panel, providing a uniformly distributed adsorption constraint force through vacuum negative pressure; the multi-point adjustable support columns are height-adaptively adjusted according to the curvature distribution of the surface, forming distributed rigid support to suppress vibration and deformation during processing; the edge aluminum alloy pressure strips provide circumferential clamping constraint on the outer contour edge of the wall panel to prevent edge warping and displacement. The support point spacing is ≤100mm, and the vacuum pressure is 0.5~0.7MPa. It should be noted that if a flexible vacuum pad is unavailable, a customized gypsum conformal support fixture + edge pressure plate can be used to achieve stable clamping of large-curvature wall panels, suitable for small-batch trial production.

[0026] Understandably, rough machining requires removing approximately 85% of the material, resulting in high cutting forces and concentrated heat, which introduces significant residual stress at the carbon fiber / resin matrix interface and within the workpiece. If the workpiece is not removed after rough machining and machining continues under clamping constraints, the residual stress will be "frozen" within the workpiece by the fixture's constraints, unable to be released. Once finally released, the workpiece will undergo uncontrollable springback deformation, directly exceeding the surface accuracy tolerances. Therefore, after rough machining, the workpiece is removed from the fixture and left to stand at room temperature for 4-8 hours, allowing it to be in a completely unconstrained free state. This allows the residual stress to be fully released through material creep and springback, enabling the workpiece to complete free deformation and reach a new stable equilibrium state before re-clamping for subsequent machining. This forms a close causal relationship with step S2. Specifically, because the deformation has been fully completed and tends to stabilize in the free state, the deviation map obtained by the online probe scanning in step S2 can truly and uniquely characterize the amount of springback deformation caused by stress release. Based on this, the generated reverse compensation has a reliable correction benchmark, and the subsequent semi-finishing and finishing paths can accurately offset the springback, so that the final surface meets the accuracy requirements. Conversely, if this stress release process is not performed, the stress will be continuously and randomly released again during the subsequent processing as the material is removed. The workpiece surface changes continuously during processing, and the deviation scanned in step S2 is only an intermediate transient value. The reverse compensation will lose an accurate benchmark and cannot converge, ultimately leading to loss of surface accuracy and an increased rework rate.

[0027] Step S2 involves scanning the surface of the stress-relieved panel using an online probe on a machine tool to generate a deviation map, which is used for reverse compensation of the subsequent semi-finishing and finishing paths.

[0028] It should be noted that after the stress relief process is completed, the actual surface of the panel is scanned and measured point by point using the machine tool's integrated online probe to obtain the three-dimensional coordinate data of the actual surface. The measured data is compared and analyzed with the theoretical digital model to generate a surface deviation distribution map. Based on this deviation data, a reverse compensation algorithm is used to correct the tool path for subsequent semi-finishing and finishing, so that the tool performs corresponding compensating cutting in the deviation area, thereby offsetting the surface springback deformation caused by stress relief and ensuring that the final machined surface meets the design accuracy requirements. In this embodiment of the invention, the compensation amount is 80% to 90% of the predicted deformation amount.

[0029] Step S3: The wall panel after stress relief is semi-finished using a PCD ring milling cutter with equal curvature. During the semi-finishing process, the machining is carried out according to the adaptive machining path planning based on the curvature partition.

[0030] In the embodiments of the present invention, the curvature of the cutting edge arc of the equal curvature PCD ring milling cutter is matched with the curvature of the corresponding machining area of ​​the wall plate, wherein the rake angle is -5°~0°, the clearance angle is 15°~20°, the cutting edge passivation radius is 3μm~5μm, and a 2~4 tooth low helix angle (10°~15°) structure is adopted.

[0031] It should be noted that the processing area is divided into three zones based on the radius of curvature of the panel: radius of curvature < 100mm (minimal curvature zone), radius of curvature between 100mm and 300mm (large curvature zone), and radius of curvature > 300mm (gentle curvature zone). Each zone is matched with a milling cutter and processing parameters corresponding to its curvature. For example, when processing a radius of curvature < 100mm (minimal curvature zone), a PCD ball end mill is used, with the spindle angle simulating a constant curvature ring end mill. In this case, the rake angle is -5° and the clearance angle is 15°. As curvature increases, the front and rear swing angles increase in fit. When working with a curvature radius of 100mm~300mm (large curvature zone), the front and rear swing angles of the PCD ball end mill spindle are simulated as a uniform curvature ring end mill. At this time, the front angle is -3° and the rear angle is 17°, and the front and rear swing angles increase in fit as curvature increases. When machining with a curvature radius >300mm (gentle curvature zone), the front and rear swing angles of the PCD ball end mill spindle are simulated as a uniform curvature ring end mill. At this time, the front angle is -1° and the rear angle is 19°, and the front and rear swing angles increase in fit as curvature increases.

[0032] The main path employs constant residual height streamline machining, with the tool path at a 30°~60° angle to the fiber direction to avoid parallel fiber cutting. It can be understood that the principle of constant residual height streamline machining is based on the constraint of a constant residual height between adjacent toolpaths, generating a continuous and smooth tool path along the principal curvature direction or streamline direction of the surface. It should be noted that in some other embodiments of this invention, constant residual height streamline machining can be replaced by a hybrid spiral constant height-local streamline machining, as specifically implemented below: Surface preprocessing: Divided into gentle curvature region, large curvature region, and minimal curvature region according to curvature; The entire system generates a spiral contour path, with a spiral rise angle of 8°~12° in flat areas and 5°~8° in areas with high curvature. The minimal curvature region is nested with local streamlined paths for milling, and a 5mm~10mm circular arc transition section is set at the path connection; Supporting parameters: feed per tooth reduced by 20% in the minimum curvature zone, tool posture change rate ≤3° / mm.

[0033] Dynamic tool posture adjustment: forward tilt angle 10°~30°, side tilt angle 5°~15°, the tilt angle increases synchronously with the increase of curvature, the posture change rate ≤5° / mm, to avoid cutting force impact caused by sudden posture changes. Understandably, the dynamic tool posture adjustment is related to the machining area. The tilt angle increases synchronously with the increase of the radius of curvature. The dynamic adjustment depends on the machining parameter settings, and the area is reflected in the machining program. For example, in the area of ​​minimal curvature, the minimum tilt angle parameter value is used. When suddenly changing to the area of ​​medium curvature radius, the tilt angle is set in the program and gradually increased through the adjustment of the forward and backward tilt angles to complete the dynamic adjustment.

[0034] Understandably, the wall surface is first divided into three regions based on the radius of curvature: <100mm, 100~300mm, and >300mm. Essentially, this decomposes the complex surface with varying curvature into several sub-regions with relatively uniform curvature. This is the prerequisite for implementing the latter two measures—only within a region where the curvature is approximately constant can matching a PCD ring milling cutter with the corresponding curvature be meaningful. Only then can the tool's cutting edge arc fit well with the surface of the machining area, ensuring uniform distribution of cutting force and stable contact. On this basis, each region is matched with its own rake angle, clearance angle, and feed parameters to ensure uniform cutting load and residual height in each region. Dynamic adjustment of the tool posture is the execution link connecting the three. On the one hand, it adjusts the swing angle to ensure that the uniform curvature cutting edge maintains the optimal fitting angle during the transition between each region and even between sub-regions. On the other hand, it avoids the impact of cutting force caused by sudden changes in posture when switching regions by limiting the rate of posture change.

[0035] More specifically, the graded feed rate (VF) is optimized: the feed rate for roughing is 1500 mm / min to 1800 mm / min, the feed rate for semi-finishing is 2200 mm / min to 2500 mm / min, the feed rate for surface finishing is 3000 mm / min to 4500 mm / min, and the feed rate for side finishing is 600 mm / min to 800 mm / min. The feed rate in the small curvature area is reduced by 30% to 50%, and unidirectional climb milling is used throughout the process.

[0036] Step S4: Roughly machine the side of the semi-finished panel using a PCD pineapple end mill with constant curvature.

[0037] Specifically, the cutting teeth of the equal curvature PCD pineapple end mill adopt an alternating left and right unequal tooth pitch structure, and the tooth curvature is adapted to the curvature of the side of the wall plate. The sharpness of the PCD cutting edge is controlled at 3μm~5μm, and the tool axis maintains an inclination angle of 1°~2° with the side machining surface to form a shearing cutting.

[0038] Step S5: After rough machining of the side panel, the surface is finished using a PCD ring milling cutter with equal curvature.

[0039] The curvature of the cutting edge of the equal curvature PCD ring milling cutter matches the curvature of the corresponding machining area of ​​the wall plate. The front angle is -5° to 0°, the back angle is 15° to 20°, the cutting edge blunting radius is 3μm to 5μm, and a 2 to 4 tooth low helix angle structure is adopted.

[0040] Step S6: After surface finishing, the side of the wall panel is finished using a PCD pineapple end mill with equal curvature.

[0041] Prior to this, aluminum foil with a thickness of 0.1mm to 0.2mm is pasted on both sides of the workpiece for pre-pressing reinforcement, and then removed after processing to further suppress edge delamination.

[0042] The cutting teeth of the equal curvature PCD pineapple end mill adopt an alternating left and right unequal tooth pitch structure, and the tooth curvature is adapted to the curvature of the side of the wall plate. The sharpness of the PCD cutting edge is controlled at 3μm~5μm, and the tool axis maintains an inclination angle of 1°~2° with the side machining surface to form a shearing cutting.

[0043] Understandably, the shearing cutting formed by maintaining a 1°~2° angle between the tool axis and the side machining surface allows the PCD cutting edge to apply a progressive sliding shearing force to the fibers rather than a frontal impact squeezing force. The fibers are "cut" one by one rather than "torn" or "crushed," which significantly reduces the tendency of fibers to be pulled out from the cutting mechanism. At the same time, the lateral component of the shearing cutting is smaller, reducing the rolling displacement of the surface fibers towards the free edge. However, the shearing cutting will still produce a residual pushing effect towards the edge. The process itself cannot completely eliminate the problem of the outermost fiber fraying due to the lack of out-of-plane support. At this time, the pre-compression reinforcement of 0.1~0.2mm aluminum foil on both sides makes up for this shortcoming. The aluminum foil applies out-of-plane compression constraint to the surface fibers on both sides of the workpiece, keeping them in a "clamped" state during the cutting process. Even if the cutting edge has a tendency to pull out fibers, the fibers cannot come out in the out-of-plane direction. Moreover, the aluminum foil itself is soft and easy to cut with the tool without damaging the cutting edge, ultimately suppressing edge fraying.

[0044] In other embodiments of the present invention, the constant curvature PCD end mill can be replaced with an integral PCD structure to improve tool rigidity and is suitable for roughing with large allowances; in areas with extremely small curvature, the constant curvature PCD ball end mill can be used instead of the ring end mill to improve accessibility.

[0045] Step S7: Inspect the wall panel after the side finishing process. If the inspection result is qualified, the final wall panel is obtained.

[0046] It should be noted that this processing method can be used to process various large-curvature carbon fiber composite components in the aerospace field, including fuselage panels, wing skins, tail panels, engine nacelle covers, etc. of civil passenger aircraft / military aircraft. In addition, it can also be used for processing the leading / trailing edges of large-curvature carbon fiber blades in the wind power industry, processing curved surface components of carbon fiber car bodies in rail transit, processing carbon fiber body panels for new energy vehicles, and processing curved surfaces of carbon fiber composite ship hulls in the shipbuilding industry.

[0047] In summary, the method for processing large-curvature carbon fiber composite panels for aircraft provided in this invention significantly improves the tool-to-surface fit and the cutting force distribution by using a constant-curvature PCD end mill. Combined with a machining path with equal residual height, the surface accuracy and surface quality are significantly improved. In terms of side processing, the constant-curvature pineapple end mill, combined with micro-tilt shearing and pre-compression reinforcement processes, achieves more thorough fiber cutting, significantly reducing fraying, burrs, and delamination, while also improving the first-pass yield of parts. The adaptive machining path reduces idle travel and rework frequency, effectively increasing cutting speed. In addition, the service life of the PCD tool is extended.

[0048] Example 2 Embodiment 2 of the present invention provides a processing example of a large curvature fuselage panel for a certain type of passenger aircraft. Specifically, the part parameters are: T700 carbon fiber / epoxy resin composite material, overall curvature radius of 80~250mm, hyperboloid structure, blank thickness of 6mm, thickness after processing of 4mm, required surface accuracy of ±0.05mm, and no delamination or stripping on the side.

[0049] Tool configuration: Rough machining: φ16mm PCD tapered ring end mill, taper 3°, R angle 2mm; Semi-finishing: φ12mm equal curvature PCD ring end mill (cutting edge curvature 200mm), rake angle -5°, clearance angle 15°, cutting edge blunting radius 3μm, 2 teeth, helix angle 12°; Surface finishing: φ12mm equal curvature PCD ring milling cutter (cutting edge curvature 80mm / 200mm), rake angle -5°, clearance angle 15°, cutting edge blunting radius 3μm, 2 teeth, helix angle 10°; Side machining: φ10mm equal curvature PCD pineapple end mill, staggered unequal tooth pitch, PCD cutting edge sharpness controlled at 3μm, and the tool axis maintains a 1° inclination angle with the side machining surface.

[0050] Clamping scheme: 8mm thick silicone vacuum pad is used for adsorption, 32 adjustable support columns are arranged below, and the edges are pressed with aluminum alloy pressure strips, with a vacuum pressure of 0.6MPa.

[0051] Processing flow: (1) Rough machining: Five-axis cycloidal machining, removing 85% of the allowance, with a feed rate of 1600 mm / min; (2) Stress relief: Disassemble the workpiece and let it stand at room temperature for 6 hours; (3) In-machine inspection: The probe scans the surface and generates a deviation compensation file; (4) Semi-finishing: Curvature partition streamline machining, leave 0.3mm allowance, feed speed is 2200mm / min. Process the overall generated spiral contour path, the spiral helix angle is 10° in the flat area and 6° in the large curvature area; The minimal curvature region is nested with local streamlined paths for milling, and an 8mm circular arc transition section is set at the path connection point; Supporting parameters: feed per tooth reduced by 15% in the minimum curvature zone, tool posture change rate ≤2° / mm.

[0052] Dynamic adjustment of tool posture: forward tilt angle 15°, side tilt angle 10°, the tilt angle is increased synchronously with the increase of curvature, the posture change rate is ≤3° / mm, to avoid the impact of cutting force caused by sudden posture changes; (5) Roughing of the side: layer cutting, leaving a 0.2mm allowance, feed rate is 600mm / min; (6) Surface finishing: forward tilt 30°, side tilt 12°, feed speed 3200mm / min, generate a spiral contour path for the whole, spiral helix angle 12° in the flat area, and helix angle 8° in the large curvature area; The minimal curvature region is nested with local streamlined paths for milling, and a 10mm circular arc transition section is set at the path connection; Supporting parameters: feed per tooth reduced by 20% in the minimum curvature zone, tool posture change rate ≤3° / mm.

[0053] Dynamic tool posture adjustment: forward tilt angle 30°, side tilt angle 15°, the tilt angle is increased synchronously with the increase of curvature, the posture change rate is ≤5° / mm, to avoid cutting force impact caused by sudden posture changes; (7) Side finishing: micro-tilt angle 1.5°, last cut allowance 0.1mm, feed speed 800mm / min; (8) Final inspection: surface accuracy ±0.03mm, surface roughness Ra=1.2μm, no defects on the side.

[0054] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for processing carbon fiber composite panel for aircraft with large curvature, characterized in that, The method includes the following steps: S1. After the wall panel is clamped and positioned, rough machining is performed using a PCD tapered ring milling cutter, followed by stress release. After rough machining, the workpiece is removed from the fixture, left to stand at room temperature to release the machining stress, and then re-clamped for subsequent machining. S2, the stress-relieved wall panel is scanned by the online probe of the machine tool to generate a deviation map, which is used to perform reverse compensation for the subsequent semi-finishing and finishing paths; S3, the wall panel after stress relief is semi-finished using a PCD ring milling cutter with equal curvature. During the semi-finishing process, the machining is carried out according to the adaptive machining path planning based on the curvature partition. S4. The semi-finished wall panel is rough-machined on the side using a PCD pineapple end mill with equal curvature. S5, after rough machining of the side panel, the surface is finished by using a PCD ring milling cutter with equal curvature; S6, after the surface is finished, the side of the wall panel is finished using a PCD pineapple end mill with equal curvature. S7. Inspect the wall panel after the side finishing process. If the inspection result is qualified, the final wall panel is obtained. The curvature of the cutting edge arc of the equal curvature PCD ring milling cutter is matched with the curvature of the corresponding machining area of ​​the wall plate. The front angle is -5° to 0°, the clearance angle is 15° to 20°, the cutting edge blunting radius is 3μm to 5μm, and a 2 to 4 tooth low helix angle structure is adopted, with a low helix angle of 10° to 15°. The cutting teeth of the equal curvature PCD pineapple end mill adopt a staggered unequal tooth pitch structure, and the tooth curvature is adapted to the curvature of the side of the wall plate. The sharpness of the PCD cutting edge is controlled at 3μm~5μm, and the tool axis maintains an inclination angle of 1°~2° with the side machining surface to form a shearing cutting. In step S3, the panel is divided into three processing areas according to its curvature radius: curvature radius < 100mm, curvature radius between 100mm and 300mm, and curvature radius > 300mm. The milling cutter and processing parameters corresponding to the curvature are matched respectively. The main path adopts streamlined machining with equal residual height, and the tool path is at an angle of 30°~60° to the fiber direction to avoid cutting parallel to the fiber. Dynamic tool posture adjustment: forward tilt angle 10°~30°, side tilt angle 5°~15°, the tilt angle increases synchronously with the increase of curvature, the posture change rate is ≤5° / mm, to avoid cutting force impact caused by sudden posture changes.

2. The method for processing large-curvature carbon fiber composite panel for aircraft according to claim 1, characterized in that, The feed rate for roughing is 1500 mm / min to 1800 mm / min, the feed rate for semi-finishing is 2200 mm / min to 2500 mm / min, the feed rate for surface finishing is 3000 mm / min to 4500 mm / min, and the feed rate for side finishing is 600 mm / min to 800 mm / min.

3. The method for processing large-curvature carbon fiber composite panel for aircraft according to claim 1, characterized in that, In step S1, the processing stress is released by letting the room stand for 4 to 8 hours at room temperature.

4. The method for processing large-curvature carbon fiber composite panel for aircraft according to claim 1, characterized in that, Step S6 is preceded by: Aluminum foil with a thickness of 0.1mm to 0.2mm is pasted on both sides of the workpiece for pre-pressing reinforcement, and then removed after processing to further suppress edge delamination.

5. The method for processing large-curvature carbon fiber composite panel for aircraft according to claim 1, characterized in that, In step S2, the compensation amount is 80% to 90% of the predicted deformation.

6. The method for processing large-curvature carbon fiber composite panel for aircraft according to claim 1, characterized in that, It adopts a low-temperature micro-lubrication system with a lubricating oil consumption of 5ml / h to 20ml / h and a compressed air pressure of 0.5MPa to 0.7MPa, and is equipped with a high-pressure air nozzle to discharge carbon fiber dust in real time.

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