Five-axis linkage numerical control precision machining method for complex curved surface workpiece

Abstract

The application discloses a five-axis linkage numerical control precision machining method for a complex curved surface workpiece, and comprises the following steps: S1, reading original machining path data of the complex curved surface to be machined; S2, for a curved surface cutter contact point corresponding to each tool position, extracting principal curvature and principal direction geometric parameters of the position by relying on a curved surface geometric model; S3, combining structural geometric parameters of a cutter used, a cutter shaft posture and the equivalent curvature of the aforementioned normal section; S4, taking preset target surface roughness of the workpiece as a control constraint, establishing a quantitative mapping relationship between effective cutting contact arc length and cutter tip feed speed; S5, combining allowable feed acceleration and jerk limit threshold values of a machine tool, smoothing and optimizing an optimal feed speed sequence of the whole domain cutter path; and S6, carrying out post-processing on cutter path data after completing speed optimization and deviation compensation.

Description

Technical Field

[0001] This application relates to the field of CNC precision machining technology, and in particular to a five-axis linkage CNC precision machining method for complex curved surface workpieces. Background Technology

[0002] With the rapid development of high-end manufacturing fields such as aerospace, energy and power, and precision molds, core functional parts containing complex free-form surfaces are being used more and more widely, such as turbine blades, integral bladed disks, and optical mold forming surfaces. The curvature of these parts changes continuously, and the surface accuracy and surface quality directly determine the service performance of the entire machine. Five-axis linkage CNC milling is currently the core process for achieving precision machining of such parts.

[0003] Currently, the industry commonly employs a fixed-parameter toolpath planning mode for five-axis finishing of complex curved surfaces. This involves setting a uniform feed rate and tool path distance based on experience in planar machining to generate a globally consistent toolpath. However, during actual cutting, the curvature of complex curved surfaces along the feed direction is dynamically changing, causing significant fluctuations in the effective cutting contact arc length between the tool cutting edge and the workpiece surface: the contact arc length increases in concave curved surface regions, increasing the effective cutting edge length per unit time; while in convex curved surfaces with high curvature regions, the contact arc length decreases, concentrating the material load per unit cutting edge. Under constant feed parameters, there are significant differences in the uniformity of material removal and the surface residual height in different curvature regions, ultimately resulting in uneven surface roughness distribution and localized roughness deviations. Under conventional constant-parameter machining, the overall roughness fluctuation of variable-curvature surfaces is high, often requiring subsequent manual polishing, which reduces machining efficiency and can easily damage the original geometric accuracy of the surface.

[0004] To address the aforementioned issues, existing improvement solutions primarily focus on optimizing a single feed rate or adjusting a fixed line spacing. These solutions rely on simplified geometric empirical formulas to roughly match cutting parameters, failing to fully integrate multi-dimensional control methods such as tool axis posture fine-tuning and matching effective cutting edge segments. Some solutions excessively reduce feed rates in pursuit of surface quality, significantly sacrificing machining efficiency; others involve excessive parameter adjustments, easily introducing new problems such as cutting interference and machine tool impact vibration. Consequently, it is difficult to achieve high-precision uniformity control of the entire surface roughness while ensuring machining efficiency and process stability, thus failing to meet the batch precision machining requirements of high-end, complex curved surface parts.

[0005] Therefore, a five-axis linkage CNC precision machining method for complex curved surface workpieces is proposed. Summary of the Invention

[0006] This application aims to at least partially solve one of the technical problems in the aforementioned technologies.

[0007] To achieve the above objectives, the first aspect of this application proposes a five-axis linkage CNC precision machining method for complex curved surface workpieces, comprising the following steps:

[0008] S1: Read the original toolpath data for finishing the complex curved surface to be machined. This toolpath data is generated by five-axis linkage CAM programming and mainly includes the spatial coordinates of all tool points and the tool axis vector information corresponding to each tool point.

[0009] S2: For each tool contact point, extract the principal curvature and principal direction geometric parameters of the tool contact point based on the surface geometric model, and calculate the equivalent curvature of the normal section at the tool contact point in combination with the actual feed direction. At the same time, identify the concave and convex features of the surface in the current region.

[0010] S3: Combining the structural geometric parameters of the tool used, the tool axis posture and the aforementioned equivalent curvature of the normal section, the position of each tool contact point and the effective contact arc length between the tool cutting edge and the workpiece surface that actually participates in cutting are solved by geometric analytical methods.

[0011] S4: Using the workpiece's preset target surface roughness as a control constraint, establish a quantitative mapping relationship between the effective cutting contact arc length and the tool tip feed rate, and solve the optimal tool tip feed rate corresponding to each tool position point in reverse based on this mapping relationship.

[0012] S5: Combining the machine tool's allowable feed acceleration and jerk limit threshold, the optimal feed speed sequence of the entire toolpath is smoothed to eliminate speed abrupt changes; at the same time, relying on the five-axis machine tool kinematic model, the actual feed deviation of the tool tip caused by the rotation axis motion coupling during the linkage process is compensated to ensure the stability of the tool tip cutting speed.

[0013] S6: Post-process the toolpath data after speed optimization and deviation compensation to adapt it to the target five-axis machine tool structure and CNC system format, and finally generate a precision machining NC program that can be directly executed on the machine;

[0014] This solution uses the effective cutting contact arc length as the core link, establishing a closed-loop solution path that optimizes surface geometry, cutting contact state, and feed parameters. It fundamentally solves the problem of uneven global roughness distribution caused by dynamic fluctuations in the cutting contact state of complex surfaces with varying curvature. The entire optimization process is completed in the toolpath post-processing stage, without modifying the machine tool hardware structure or changing the trajectory topology and interference avoidance logic of the original toolpath, making it easy to implement in engineering. At the same time, it superimposes feed sequence smoothing and five-axis linkage feed deviation compensation, which not only avoids machine tool impact vibration caused by parameter abrupt changes, but also eliminates the distortion of actual cutting speed caused by the coupling motion of the rotary axis, ensuring stable machining process and precise and controllable cutting speed.

[0015] In addition, the five-axis linkage CNC precision machining method for complex curved surface workpieces proposed in this application may also have the following additional technical features:

[0016] As a further description of the above technical solution:

[0017] The quantitative mapping relationship constructed in step S4 is based on the geometric model of feed residual height under the machining condition of variable curvature surface. At the same time, the matching correction coefficient of tool and workpiece material is obtained by fitting multiple sets of process experiments, and the theoretical geometric model is calibrated and compensated for errors.

[0018] This solution uses tool and material matching correction coefficients fitted by process experiments to calibrate the residual height model derived purely by geometry. This overcomes the limitation of large deviations between traditional pure geometric models and actual machining conditions. It can adapt to the cutting characteristics of different workpiece materials and tool types, significantly improve the actual solution accuracy of the mapping model, avoid systematic deviations between theoretical calculations and on-site machining results, and ensure the accuracy of roughness control.

[0019] As a further description of the above technical solution:

[0020] Between steps S3 and S4, an adaptive fine-tuning step for the tool axis tilt angle is added; a reasonable fluctuation range of the effective cutting contact arc length is preset; when the real-time contact arc length of the tool contact point is detected to exceed the range, the current tool axis tilt angle is slightly adaptively adjusted within a safety margin that does not cause machining interference.

[0021] Specifically, for high-curvature concave surface regions, the tool axis tilt angle is appropriately increased to shorten the effective cutting contact arc length; for high-curvature convex surface regions, the tool axis tilt angle is appropriately decreased to extend the effective cutting contact arc length, so that the contact arc length of each tool contact point in the entire region converges to a preset reasonable range.

[0022] This solution reduces the global fluctuation of the contact arc length from a geometrical perspective by slightly adaptively adjusting the tool axis tilt angle. This effectively reduces the magnitude of feed rate adjustment in extreme curvature regions, avoiding machining efficiency loss due to a significant decrease in feed rate. The adjustment process is strictly limited to a non-interference safety margin, without introducing cutting interference risks. It can complement feed rate optimization, balancing surface quality consistency and machining efficiency without sacrificing machining safety.

[0023] As a further description of the above technical solution:

[0024] Step S4 simultaneously performs curvature adaptive tool path spacing fine-tuning while solving for the optimal feed rate;

[0025] Using the theoretical residual height corresponding to the target surface roughness as the control benchmark, and combining the local equivalent curvature of each tool contact point, the optimal tool path spacing adapted to the current surface features is solved in reverse. Within the preset floating ratio range of the original programmed path spacing, a small adjustment is made. The path spacing is appropriately widened in flat areas of the surface to improve processing efficiency, and the path spacing is appropriately densed in high curvature areas to suppress residual height deviation and ensure the uniformity of the overall surface processing quality.

[0026] This solution supplements roughness control by adjusting the tool path spacing, forming a dual-parameter adjustment with feed rate optimization. Compared to single feed adjustment, it offers higher precision in controlling residual height and greater flexibility. The spacing adjustment is limited to a small fluctuation range of the original spacing, without disrupting the overall layout logic of the original toolpath. In flat areas, the spacing is widened to improve efficiency, while in high-curvature areas, the spacing is denser to ensure quality. This approach maximizes the balance between machining efficiency and surface quality while ensuring roughness uniformity.

[0027] As a further description of the above technical solution:

[0028] After the surface curvature feature recognition is completed in step S2 and before the contact arc length is calculated in step S3, an effective working segment partition matching step for the cutting edge is added.

[0029] Based on the differences in the surface tilt angles corresponding to each tool contact point, the overall complex surface is divided into multiple machining feature intervals, and the optimal tool axis tilt angle range is matched for different intervals. During the machining process, the optimal cutting edge segment of the tool is always used to participate in cutting, avoiding sudden changes in the cutting edge linear velocity caused by frequent switching of the cutting edge position, and effectively improving the problem of local surface roughness fluctuation.

[0030] This solution starts with the participation state of the cutting edge of the tool. By matching fixed effective cutting edge segments in different zones, it eliminates the roughness fluctuations caused by the switching of cutting edge position and sudden changes in cutting edge linear velocity due to changes in surface slope. It complements the feed and attitude parameter optimization in multiple dimensions, further compressing the fluctuation range of local surface roughness and improving the stability of surface quality across the entire area.

[0031] As a further description of the above technical solution:

[0032] During the machining process, the tool axis tilt angle is finely adjusted, the feed distance is adaptively adjusted, and the tool tip feed speed is optimized in a coordinated manner.

[0033] When the real-time effective contact arc length of the tool contact point deviates from the reference contact arc length beyond the preset threshold, the contact arc length is calibrated by adjusting the geometric parameters of the tool axis posture and the tool travel distance. Then, the optimal feed speed is matched by solving the calibrated contact arc length to achieve the coordinated adaptation of geometric features and cutting parameters.

[0034] This solution clarifies the execution priority and linkage logic of multi-parameter coordination. It stipulates that when the contact arc length deviation is large, the geometric parameters (tool axis tilt angle, tool path distance) should be calibrated first, and then the feed parameters should be matched. This avoids control conflicts and process risks caused by simultaneous large adjustments of multiple parameters. Through the coordination mechanism of hierarchical control, the optimal matching of geometric features and cutting parameters is achieved, which not only ensures the surface roughness control effect, but also maintains the overall smoothness of the toolpath and the machining stability.

[0035] As a further description of the above technical solution:

[0036] The original five-axis finishing toolpath data in step S1 is generated by general CAM software. The toolpath data adopts CLS format or APT format and can be directly read and analyzed to obtain the tool position point and tool axis vector parameters.

[0037] This solution limits the source and format of toolpath data, is compatible with the standard output format of mainstream CAM software, does not require changing existing programming tools or developing dedicated programming interfaces, can be directly embedded into existing machining processes, has strong compatibility, low implementation cost, and is easy to promote and apply in industrial production scenarios.

[0038] As a further description of the above technical solution:

[0039] The post-processing in step S6 is compatible with mainstream five-axis machine tools with dual rotary tables, dual swivel heads, and swivel head rotary tables, and is adapted to various commercial CNC system program formats. The generated NC program fully retains the RTCP tool tip following function and safety obstacle avoidance path logic of the original toolpath, without changing the interference protection performance of the original toolpath.

[0040] Advantages of this invention:

[0041] According to the five-axis linkage CNC precision machining method for complex curved surface workpieces in this application, starting from the root cause of the change in cutting contact state, a quantitative mapping relationship between the geometric features of the curved surface and the cutting parameters is established. This can fundamentally solve the problem of uneven surface roughness distribution caused by the dynamic fluctuation of contact arc length in complex curved surfaces with variable curvature, significantly compress the surface roughness fluctuation range, significantly reduce the workload of subsequent manual polishing and finishing, and avoid the damage to the original surface geometric accuracy caused by polishing.

[0042] The multi-parameter collaborative control mechanism, which adopts adaptive feed rate optimization, micro-correction of tool axis tilt angle, follow-up adjustment of tool feed distance, and zone matching of effective cutting edge segment, has higher control accuracy and adjustment flexibility compared with single parameter optimization scheme. It can avoid process risks such as cutting interference and sudden load change caused by large adjustment of a single parameter. While ensuring the consistency of surface roughness, it can reasonably match the cutting parameters of each area, taking into account both machining efficiency and process stability.

[0043] The synchronous introduction of feed sequence smoothing and five-axis linkage feed deviation compensation can eliminate machine tool impact vibration caused by abrupt changes in discrete parameters, correct the distortion of the actual cutting speed of the tool tip caused by the coupled motion of the rotary axis, effectively suppress surface vibration defects, and further improve the stability of the machining process and the surface machining accuracy.

[0044] The entire optimization process is completed in the toolpath post-processing stage, without requiring any modification to the machine tool hardware structure, and without changing the trajectory topology, interference avoidance logic, and safety path of the original toolpath. It has a low threshold for engineering implementation and is compatible with the standard toolpath format output by mainstream CAM software. It is compatible with various five-axis machine tool structures such as dual rotary tables, dual swivel heads, and swivel head-rotor composites, as well as corresponding mainstream CNC systems. It can be directly embedded into existing machining processes and has low promotion and application costs and strong scenario adaptability.

[0045] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0046] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0047] Figure 1 This is a flowchart illustrating a five-axis linkage CNC precision machining method for complex curved surface workpieces according to an embodiment of this application;

[0048] Figure 2 This is a schematic diagram comparing the surface roughness of a five-axis linkage CNC precision machining method for complex curved surface workpieces according to an embodiment of this application;

[0049] Figure 3 This is a schematic diagram comparing the processing time of a five-axis linkage CNC precision machining method for complex curved surface workpieces according to an embodiment of this application. Detailed Implementation

[0050] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0051] The following describes, with reference to the accompanying drawings, a five-axis linkage CNC precision machining method for complex curved surface workpieces according to an embodiment of this application. The machining object of this embodiment is a single rotor blade profile of an integral bladed disk of a certain type of aero-engine. The workpiece material is TC4 titanium alloy. The blade profile is a free-form surface, including three typical variable curvature features: a strong convex arc area at the blade tip, an approximately flat area on the blade body, and a strong concave arc area at the blade root. The overall dimensions of the profile are approximately chord length 80mm and blade height 50mm. The single-sided allowance for finishing is 0.1mm. The machining requirements are: profile accuracy ≤0.02mm, surface roughness Ra ≤0.8μm across the entire area, and roughness range ≤0.2μm across the entire area.

[0052] The five-axis linkage machining center adopts the DMG MORI DMU50 dual rotary table structure and the CNC system is SIEMENS 840Dsl. The system supports RTCP tool tip following function. The positioning accuracy of the machine tool translation axis is ±0.003mm and the positioning accuracy of the rotary axis is ±5mm. The tooling adopts a special impeller tensioning fixture. After the workpiece is clamped, the overall rigidity meets the requirements of vibration control for precision machining.

[0053] The finishing tool is a φ12mm solid carbide TiAlN coated ball end mill with 2 teeth, a ball end radius R=6mm, and a cutting edge radius of [missing information]. The tool overhang length is 35mm, the finishing spindle speed is set to n=8000r / min, and the radial depth of cut (i.e., the initial tool path distance) is set to... Axial depth of cut .

[0054] like Figure 1-3 As shown in Embodiment 1 of this application, the five-axis linkage CNC precision machining method for complex curved surface workpieces comprises the following specific steps:

[0055] S1 Original 5-Axis Finishing Toolpath Data Acquisition:

[0056] The original toolpath was programmed using the UGNX12.0CAM module, with surface region drive selected as the drive method and reciprocating cutting mode as the toolpath. The toolpath was arranged along the chord of the blade. The original toolpath used a globally constant feed rate setting, with the tool tip feed rate... The corresponding feed per tooth After programming, a CLS format toolpath file is output. The file contains 12,860 toolpath points arranged in the machining sequence. Each toolpath point contains three-dimensional spatial coordinates (X,Y,Z), tool axis vector (I,J,K), and original feed command values. The toolpath completely covers all curvature areas of the blade profile, including three typical feature segments: the tip convex arc, the blade flat area, and the root concave arc. The original toolpath has been verified by the UG built-in interference check module, with no risk of overcutting or collision.

[0057] S2 tool contact point local geometric feature extraction and curvature calculation:

[0058] Read all tool positions from the toolpath file and project each tool position onto the workpiece NURBS surface model along the tool axis vector direction to obtain the surface tool contact point corresponding to each tool position. Based on differential geometry theory, solve for the local geometric features of each tool contact point:

[0059] (1) Calculate the first basic form coefficients E, F, G and the second basic form coefficients L, M, N at the tool contact point by using the first and second partial derivatives of the surface, and solve for the two principal curvatures k1, k2 and the corresponding principal directions at the point.

[0060] (2) Project the toolpath feed direction vector onto the tangential plane of the tool contact point to obtain the feed direction tangential vector; based on the principal curvature and principal direction, calculate the equivalent curvature of the normal section in the feed direction using the direction angle formula of curvature. The calculation formula is:

[0061]

[0062] in The angle between the feed direction and the first principal direction.

[0063] (3) Based on the equivalent curvature The sign of the surface determines its concavity / convexity property. When >0, it is a convex surface. When <0, it is a concave surface. <0.005mm -1 It was determined to be an approximately flat region;

[0064] The calculation results for the three typical regions in this embodiment are as follows:

[0065] A certain blade contact point in the flat area of ​​the blade: =0.002mm -1 , =0.005mm -1 Equivalent curvature in the feed direction =0.003mm -1 It is determined to be a weakly convex flat region;

[0066] A certain blade contact point in the convex arc area of ​​the blade tip: =0.08mm -1 , =0.03mm -1 Equivalent curvature in the feed direction =0.08mm -1 Corresponding radius of curvature =12.5mm, which is determined to be a strongly convex curved surface;

[0067] A certain knife contact point in the concave arc region of the leaf root: =-0.06mm -1 , =-0.02mm -1 Equivalent curvature in the feed direction =-0.06mm -1 The corresponding absolute value of the radius of curvature =16.67mm, which is determined to be a strongly concave surface.

[0068] Analytical calculation of effective cutting contact arc length of S3:

[0069] Combining tool geometry parameters, tool axis posture, and equivalent curvature of the tool contact point, the effective cutting contact arc length at each tool contact point, where the tool cutting edge and the workpiece surface actually participate in the cutting, is calculated using a geometric analytical method. For the ball end mill used in this embodiment, the formula for calculating the effective cutting contact arc length under the condition of finishing a small depth of cut is as follows:

[0070] For convex surfaces :

[0071]

[0072] For concave surfaces :

[0073]

[0074] For approximately flat regions :

[0075]

[0076] in The radius of the ball end mill is... To measure the amount of knife cuts on the back, The absolute value of the equivalent radius of curvature;

[0077] Substituting the process parameters in this embodiment =6mm =0.1mm, the effective cutting contact arc length of three typical regions was calculated:

[0078] Reference contact arc length in flat area ;

[0079] Contact arc length of the blade tip with strong convex curved surface It is about 17.8% shorter than the flat area;

[0080] Leaf root concave surface contact arc length The growth rate was approximately 25.1% compared to the flatter areas;

[0081] It can be seen that the contact arc length of a variable curvature surface fluctuates by more than 40% across the entire range, which will inevitably lead to uneven surface roughness distribution under constant feed parameters.

[0082] Inverse solution for the optimal feed rate under constant roughness constraint S4:

[0083] This step uses a preset target surface roughness. With 0.8μm as a constraint, and based on the control principle of constant feed per tooth corresponding to unit effective cutting arc length, a quantitative mapping model between effective cutting contact arc length and tool tip feed speed is established, and the optimal feed speed of each tool contact point is solved in reverse.

[0084] (1) Theoretical mapping relationship construction: When the feed rate per unit length of the cutting edge is constant, the residual cutting height is uniform, and the corresponding surface roughness is uniform. Therefore, the optimal feed rate per tooth is... With effective contact arc length Satisfies a direct proportional relationship:

[0085]

[0086] in The feed per tooth is the baseline for the flat zone. This is the reference contact arc length in the flat region.

[0087] Convert the feed per tooth to the tool tip feed rate: ;

[0088] (2) Process Error Compensation Correction: The pure geometric model does not consider the influence of actual factors such as cutting force deformation, edge reflection, and material plastic deformation. Therefore, the model is calibrated by fitting correction coefficients through process experiments. In this embodiment, for the machining combination of TC4 titanium alloy and carbide ball end mills, three sets of plane cutting calibration tests with different feed rates were completed. The actual surface roughness was detected and compared with the theoretical value to obtain the process correction coefficients. =1.15, the corrected optimal feed rate formula is:

[0089]

[0090] Substituting the contact arc length values ​​for a typical region, the calculation yields:

[0091] Optimal feed in the tip arc region ;

[0092] Optimal feed in the flat region of the blade ;

[0093] Optimal feed in the concave arc region of the blade root ;

[0094] Through the above calculations, the feed rate is automatically reduced in convex curved areas with short contact arc lengths, and the feed rate is automatically increased in concave curved areas with long contact arc lengths, ensuring uniform feed rate per unit cutting length across the entire area and achieving consistent surface roughness control from the source.

[0095] While calculating the feed rate, a curvature-following toolpath spacing fine-tuning is performed simultaneously: using the target residual height as a reference, the optimal toolpath spacing is calculated in reverse by combining local equivalent curvature. The spacing adjustment is limited to ±10% of the original spacing, i.e., 0.27mm~0.33mm. The optimal spacing calculation formula is:

[0096]

[0097] Calculations show that: the row spacing in the convex curved area is widened to 0.33mm to improve efficiency; the row spacing in the concave curved area is tightened to 0.27mm to control residual height; and the original row spacing of 0.3mm is maintained in the flat area. The row spacing adjustment and feed speed optimization are performed in tandem. When the contact arc length deviation exceeds 20%, the row spacing is adjusted first; when the deviation is less than 20%, only the feed is adjusted to avoid process risks caused by excessive adjustment of a single parameter.

[0098] In addition, this step simultaneously performs effective section matching of the cutting edge: the blade profile is divided into three machining zones according to the surface slope (angle between the surface normal and the machine tool Z-axis) at the tool contact point, corresponding to different tool axis tilt angle ranges: the flat zone with a slope < 30° is matched with a side tilt angle of 0°~15°, and the cutting is performed using the center cutting edge of the tool tip arc; the gentle slope zone with a slope of 30°~60° is matched with a side tilt angle of 15°~30°, and the cutting is performed using the upper part of the arc cutting edge; the steep wall zone with a slope > 60° is matched with a side tilt angle of 30°~45°, and the cutting is performed using the transition section between the arc and the cylindrical cutting edge. Through section matching, the cutting edge segment is kept relatively stable, eliminating roughness fluctuations caused by sudden changes in the cutting edge linear velocity.

[0099] S5 feed sequence smoothing and five-axis linkage feed deviation compensation:

[0100] The feed rate obtained by direct inverse kinematics is a discrete point value. Feed steps are likely to occur between adjacent tool points, exceeding the acceleration and deceleration capabilities of the machine tool. Therefore, the feed sequence of the entire toolpath needs to be smoothed. At the same time, the rotary axis motion in five-axis linkage will be superimposed with the tool tip additional speed, which will cause the actual cutting speed to deviate from the command value. Compensation and correction are required.

[0101] (1) Feed sequence smoothing: preset feed acceleration threshold =0.3g (approximately 2.94m / s²), accelerometer threshold =20m / s³, a fifth-order polynomial interpolation algorithm is used to perform global smoothing on the discrete feed sequence to ensure that the feed value, acceleration and jerk are continuous without abrupt changes, and to avoid surface ripples caused by machine tool impact. The smoothing process aims at the optimal feed value and tries to get as close as possible to the theoretical optimal value while satisfying the dynamic constraints.

[0102] (2) Five-axis linkage feed deviation compensation: Based on the kinematic model of the five-axis machine tool with dual rotary table, the angular velocity and angular acceleration of the rotating axis at each tool position point are calculated, and the additional linear velocity of the tool tip point caused by the rotational motion is solved; the additional velocity vector and the tool tip feed velocity vector are combined to correct the feed command value in reverse, so as to ensure that the actual cutting speed of the tool tip relative to the workpiece is equal to the set optimal value. In this embodiment, the swing angle of the blade root concave arc area changes drastically, and the additional speed of the rotating axis can reach up to 85 mm / min. After compensation, the actual cutting speed deviation is controlled within 2%.

[0103] After the contact arc length is calculated but before the feed rate is solved, an adaptive micro-correction of the tool axis tilt angle is performed simultaneously: the preset allowable fluctuation range of the effective cutting contact arc length is ±15% of the reference arc length, i.e., [1.86mm, 2.52mm]. When the contact arc length of the tool contact point exceeds this range, the tool axis tilt angle is slightly adjusted within a non-interference safety margin, with the adjustment range controlled within ±5°. Specifically, the tilt angle is increased in strongly concave curved areas to shorten the contact arc length, and the tilt angle is decreased in strongly convex curved areas to increase the contact arc length, so that the adjusted contact arc length converges to within the allowable range.

[0104] For example, the original side tilt angle of the blade root concave arc area is 15°, and the contact arc length of 2.74mm exceeds the upper limit. After increasing the side tilt angle to 19°, the contact arc length is shortened to 2.45mm, falling into the allowable range. At this time, the feed rate does not need to be significantly reduced to meet the surface roughness requirements, effectively balancing machining efficiency. The entire adjustment is verified by offline interference to ensure that a safety margin of not less than 0.5mm is maintained between the tool and the workpiece, with no risk of overcutting.

[0105] S6 Post-processing and CNC Program Generation:

[0106] The post-processing of the optimized toolpath data is adapted to the DMU50 dual-rotary-table five-axis machine tool structure and the SIEMENS 840Dsl CNC system format. The post-processing process fully preserves the original toolpath's RTCP tool tip following instructions, safe retraction path, tool change logic, and interference avoidance strategies, only replacing the feed rate value at the tool position point and fine-tuning the tool axis vector and travel distance. Finally, a G-code CNC program that can be directly executed on the machine is generated. The program contains all machining information, including translational axis coordinates, rotary axis angles, feed rate commands, and spindle speed commands, and can be directly imported into the machine tool control system for finishing.

[0107] To verify the practical effect of this method, two identical blade samples were machined using the same machine tool, cutting tool, and clamping conditions, respectively, using both the traditional constant parameter machining scheme and the scheme of this invention. After machining, the surface roughness was measured using a Taylor Hopson FormTalysurfi series roughness tester at five measuring points in each of three typical areas along the feed direction: the tip convex arc, the blade flat area, and the root concave arc. The test results are as follows:

[0108] Traditional constant parameter scheme: average of tip convex arc region =1.05μm, average of flat areas on the leaf blade =0.72μm, average of leaf root concave arc region =0.58μm, global roughness range is 0.47μm, coefficient of variation is 22.3%; total processing time is 12.8 minutes.

[0109] Invention solution: average of the convex arc area at the blade tip =0.83μm, average of flat areas on the leaf blade =0.76μm, average of leaf root concave arc region =0.74μm, global roughness range is 0.09μm, coefficient of variation is 4.2%; total processing time is 11.5 minutes, and processing efficiency is improved by about 10.2% compared with traditional methods.

[0110] Comparative results show that the method of the present invention can control the global roughness fluctuation of the variable curvature surface within a very small range, significantly improving the surface quality consistency. At the same time, the processing efficiency can be slightly improved by reasonably matching the feed and line spacing parameters, which fully meets the precision processing requirements of high-end complex curved surface parts.

[0111] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0112] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0113] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A five-axis linkage CNC precision machining method for complex curved surface workpieces, characterized in that, Includes the following steps: S1: Read the original toolpath data for finishing the complex curved surface to be machined. This toolpath data is generated by five-axis linkage CAM programming and mainly includes the spatial coordinates of all tool points and the tool axis vector information corresponding to each tool point. S2: For each tool contact point, extract the principal curvature and principal direction geometric parameters of the tool contact point based on the surface geometric model, and calculate the equivalent curvature of the normal section at the tool contact point in combination with the actual feed direction. At the same time, identify the concave and convex features of the surface in the current region. S3: Combining the structural geometric parameters of the tool used, the tool axis posture and the aforementioned equivalent curvature of the normal section, the position of each tool contact point and the effective contact arc length between the tool cutting edge and the workpiece surface that actually participates in cutting are solved by geometric analytical methods. S4: Using the workpiece's preset target surface roughness as a control constraint, establish a quantitative mapping relationship between the effective cutting contact arc length and the tool tip feed rate, and solve the optimal tool tip feed rate corresponding to each tool position point in reverse based on this mapping relationship. S5: Combining the machine tool's allowable feed acceleration and jerk limit threshold, the optimal feed speed sequence of the entire toolpath is smoothed to eliminate speed abrupt changes; at the same time, relying on the five-axis machine tool kinematic model, the actual feed deviation of the tool tip caused by the rotation axis motion coupling during the linkage process is compensated to ensure the stability of the tool tip cutting speed. S6: Post-process the toolpath data after speed optimization and deviation compensation, adapt it to the target five-axis machine tool structure and CNC system format, and finally generate a precision machining NC program that can be directly executed on the machine.

2. The five-axis linkage CNC precision machining method for complex curved surface workpieces according to claim 1, characterized in that: The quantitative mapping relationship constructed in step S4 is based on the geometric model of feed residual height under the machining condition of variable curvature surface. At the same time, the matching correction coefficient of tool and workpiece material is obtained by fitting multiple sets of process experiments, and the theoretical geometric model is calibrated and compensated for errors.

3. The five-axis linkage CNC precision machining method for complex curved surface workpieces according to claim 1, characterized in that: Between steps S3 and S4, an adaptive fine-tuning step for the tool axis tilt angle is added; a reasonable fluctuation range of the effective cutting contact arc length is preset; when the real-time contact arc length of the tool contact point is detected to exceed the range, the current tool axis tilt angle is slightly adaptively adjusted within a safety margin that does not cause machining interference. Specifically, for high-curvature concave surface regions, the tool axis tilt angle is appropriately increased to shorten the effective cutting contact arc length; for high-curvature convex surface regions, the tool axis tilt angle is appropriately decreased to extend the effective cutting contact arc length, so that the contact arc length of each tool contact point in the entire region converges to a preset reasonable range.

4. The five-axis linkage CNC precision machining method for complex curved surface workpieces according to claim 1, characterized in that: Step S4 simultaneously performs curvature adaptive tool path spacing fine-tuning while solving for the optimal feed rate; Using the theoretical residual height corresponding to the target surface roughness as the control benchmark, and combining the local equivalent curvature of each tool contact point, the optimal tool path spacing adapted to the current surface features is solved in reverse. Within the preset floating ratio range of the original programmed path spacing, a small adjustment is made. The path spacing is appropriately widened in flat areas of the surface to improve machining efficiency, and the path spacing is appropriately densed in high curvature areas to suppress residual height deviation and ensure the uniformity of the overall machining quality of the surface.

5. The five-axis linkage CNC precision machining method for complex curved surface workpieces according to claim 1, characterized in that: After the surface curvature feature recognition is completed in step S2 and before the contact arc length is calculated in step S3, an effective working segment partition matching step for the cutting edge is added. Based on the differences in the surface tilt angles corresponding to each tool contact point, the overall complex surface is divided into multiple machining feature intervals, and the optimal tool axis tilt angle range is matched for different intervals. During the machining process, the optimal cutting edge segment of the tool is always used to participate in cutting, avoiding sudden changes in the cutting edge linear velocity caused by frequent switching of the cutting edge position, and effectively improving the problem of local surface roughness fluctuation.

6. The five-axis linkage CNC precision machining method for complex curved surface workpieces according to any one of claims 3 to 5, characterized in that: During the machining process, the tool axis tilt angle is finely adjusted, the feed distance is adaptively adjusted, and the tool tip feed speed is optimized in a coordinated manner. When the real-time effective contact arc length of the tool contact point deviates from the reference contact arc length beyond a preset threshold, the contact arc length is calibrated by adjusting the geometric parameters of the tool axis posture and the tool travel distance. Then, the optimal feed rate is matched by solving the calibrated contact arc length to achieve coordinated adaptation of geometric features and cutting parameters.

7. The five-axis linkage CNC precision machining method for complex curved surface workpieces according to claim 1, characterized in that: The original five-axis finishing toolpath data in step S1 is generated by general CAM software. The toolpath data adopts CLS format or APT format, and the tool position point and tool axis vector parameters can be directly read and analyzed.

8. The five-axis linkage CNC precision machining method for complex curved surface workpieces according to claim 1, characterized in that: The post-processing in step S6 is compatible with mainstream five-axis machine tools with dual rotary tables, dual swivel heads, and swivel head rotary tables, and is adapted to various commercial CNC system program formats. The generated NC program fully retains the RTCP tool tip following function and safety obstacle avoidance path logic of the original toolpath, without changing the interference protection performance of the original toolpath.

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