A clamping and aligning method for large structural parts based on in-machine measurement

Abstract

The application provides a large structure clamping and alignment method based on in-machine measurement, and relates to the technical field of numerical control machining. Measurement points and measurement paths are planned on a workpiece three-dimensional model, and measurement tasks are divided into three groups of measurements, i.e. leveling, finding an origin and finding an angle direction, so that the workpiece is gradually constrained in six degrees of freedom in space. The workpiece is preliminarily clamped on a machine tool, and leveling, finding an origin and finding an angle direction measurements are respectively performed. The leveling measurement is used to correct the flatness and inclination angle of the main reference surface of the workpiece, the finding an origin is used to correct the origin of the workpiece, and the finding an angle direction measurement is used to adjust the angular attitude of the workpiece. The application has the beneficial effects that high-precision alignment can be realized under the condition that the preliminary clamping precision of the workpiece is limited, and the machining precision and production efficiency of the machine tool are improved.

Description

Technical Field

[0001] This invention relates to the field of CNC machining technology, and in particular to a method for clamping and aligning large structural parts based on in-machine measurement. Background Technology

[0002] With the continuous evolution of automated production technology, the requirements for operational efficiency and machining accuracy of production lines are progressively increasing. In the field of large structural component machining, taking typical components such as aircraft structural components and central wing slats in the aerospace industry as examples, these components have technical characteristics such as large size, complex geometry, high surface continuity, and lack of explicit reference features. This characteristic directly makes the workpiece clamping and alignment process a core bottleneck restricting the improvement of machining accuracy and production efficiency.

[0003] Currently, the clamping, alignment, and deformation control of large structural components generally rely on customized special fixtures. However, these special fixtures require targeted design based on the specific structural parameters, material properties, and process flow of the parts, and must undergo multiple rounds of trial production and iterative optimization before finalization. This leads to problems such as high manufacturing costs, lengthy design cycles, and poor versatility, making it difficult to achieve large-scale application in multi-variety, small-batch production models. At the same time, traditional manual clamping and positioning methods are not only inefficient, but their positioning accuracy is also easily affected by human factors such as the operator's experience level and operational standardization, making it difficult to guarantee the consistency and stability of processing quality during mass production. In summary, how to achieve efficient and stable automated positioning of large structural components while ensuring that the positioning accuracy meets the technical requirements has become a key technical problem that urgently needs to be solved in the current manufacturing industry. Summary of the Invention

[0004] In view of this, in order to solve the problems of large structural components relying on special fixtures, high manufacturing costs, long cycle time, low efficiency and difficulty in guaranteeing accuracy of manual alignment, the embodiments of the present invention provide a clamping and alignment method for large structural components based on in-machine measurement.

[0005] Embodiments of the present invention provide a method for clamping and aligning large structural components based on in-machine measurement, comprising the following steps: S1. On the three-dimensional model of the workpiece, the measurement points and measurement paths are planned to generate a measurement program. The measurement program includes three measurement tasks: leveling, finding the origin, and finding the angular direction. The three measurement tasks constrain the six degrees of freedom of the workpiece in space step by step. S2. Initially clamp the workpiece; S3. The machine tool performs the leveling measurement task, obtains the actual leveling measurement data, compares the actual leveling measurement data with the leveling theoretical data, calculates the deviation matrix, and generates the corresponding leveling CNC program based on the deviation matrix. Based on the leveling CNC program, the machine tool is driven to perform planar posture adjustment, thereby correcting the planar posture of the workpiece. S4. The machine tool performs the origin-finding measurement task, obtains the actual measurement data of the origin-finding measurement, compares the actual measurement data of the origin-finding with the theoretical data of the origin-finding, calculates the deviation matrix, and generates the corresponding origin-finding CNC program based on the calculation results. Based on the origin-finding CNC program, the machine tool is driven to adjust the position of the workpiece, thereby determining the position reference of the workpiece and aligning the origin of the workpiece with the origin of the machine tool coordinate system. S5. The machine tool performs the angular direction measurement task, obtains the actual measurement data of the angular direction, compares the actual measurement data of the angular direction with the theoretical data of the angular direction, calculates the rotation deviation angle, and generates the corresponding angular direction CNC program based on the calculation result. Based on the angular direction CNC program, the machine tool is driven to perform angular adjustment, thereby determining the angular posture of the workpiece and making the workpiece direction consistent with the machine tool coordinate system.

[0006] Furthermore, it also includes S6, which involves replanning the retest points and retest measurement paths on the workpiece's three-dimensional model, executing the retest on the machine tool, obtaining the actual retest results, comparing the actual retest results with the theoretical retest points, and determining that the workpiece has been accurately aligned if the deviation is within the predetermined range; otherwise, repeating steps S1-S5 until the deviation is within the predetermined range.

[0007] Further, step S1 specifically includes: based on the three-dimensional model of the workpiece, combined with the structural features and positioning reference requirements of the workpiece, planning measurement points and measurement paths on the three-dimensional model, and generating corresponding measurement programs; according to the geometric features of the workpiece and the degrees of freedom to be constrained, dividing the measurement task into three measurement tasks: leveling, finding the origin, and finding the angular direction, so as to constrain the six degrees of freedom of the workpiece in space step by step.

[0008] Furthermore, the method for establishing the leveling measurement task in step S1 is as follows: select measurement points on the main reference plane of the workpiece, plan the measurement path in combination with the measurement strategy parameters, and generate the corresponding measurement program.

[0009] Furthermore, the method for establishing the original measurement task in step S1 is as follows: select measurement points on an auxiliary reference surface orthogonal to the main reference surface of the workpiece, plan the measurement path in combination with the measurement strategy parameters, and generate the corresponding measurement program.

[0010] Furthermore, the method for establishing the angular direction measurement task in step S1 is as follows: select measurement points on geometric features that are sensitive to angular changes, plan the measurement path in combination with measurement strategy parameters, and generate the corresponding measurement program.

[0011] Furthermore, geometric features sensitive to angular changes include locating holes, feature planes orthogonal to the main datum plane, feature surfaces parallel to the XZ or YZ plane of the machine tool coordinate system, and feature edges parallel to the X-axis or Y-axis direction of the machine tool coordinate system.

[0012] Furthermore, the method for obtaining the leveling CNC program in step S3 is as follows: based on the actual leveling measurement point set data and the leveling theoretical measurement point set data, the optimal rigid body transformation is solved to calculate the rotation matrix and translation vector, and the translation deviation in the Z-axis direction and the rotation deviation around the X-axis or Y-axis are extracted from them, thereby generating the corresponding CNC program based on the translation deviation and rotation deviation.

[0013] Further, in step S4, the method for obtaining the original CNC program is as follows: the coordinates of the original actual measurement point and the original theoretical measurement point are organized into a matrix form, and the deviation vector set of each measurement point is obtained by subtracting them point by point; then the coordinate components of all deviation vectors are accumulated and averaged to obtain the average translation amount of the workpiece as a whole; and then the corresponding CNC program is generated based on the average translation amount.

[0014] Further, in step S5, the method for obtaining the angular direction CNC program is as follows: by extracting the X-axis coordinates and Y-axis coordinates of the theoretical measurement point and the actual measurement point of the angular direction, two two-dimensional vectors u and v representing the theoretical direction and the actual direction are constructed respectively. Then, the angle between the two vectors is calculated by using the cross product and dot product of the vectors, thereby obtaining the rotational deviation angle of the workpiece relative to the theoretical reference in the plane, and generating the corresponding CNC program based on the rotational deviation angle.

[0015] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: The present invention provides a method for clamping and aligning large structural parts based on in-machine measurement. Measurement points and paths are planned on the three-dimensional model of the workpiece, and the measurement task is divided into three groups of measurements: leveling, origin finding, and angular finding. This achieves gradual constraint on the workpiece in six degrees of freedom in space. The workpiece is initially clamped on the machine tool, and leveling, origin finding, and angular finding measurements are performed respectively. The flatness and tilt angle of the main datum surface of the workpiece are corrected by leveling measurement, the origin of the workpiece is corrected by origin finding, and the angular orientation of the workpiece is adjusted by angular finding measurement. In this way, high-precision alignment can be achieved under the condition that the initial clamping accuracy of the workpiece is limited, thereby improving the machining accuracy and production efficiency of the machine tool. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for clamping and aligning large structural components based on in-machine measurement according to the present invention; Figure 2 This is a preliminary clamping diagram of the workpiece; Figure 3 This is a schematic diagram of the workpiece clamping and alignment process. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0018] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0019] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0020] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0021] It should be further noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Please refer to Figure 1 The embodiments of the present invention provide a clamping and alignment method for large structural components based on in-flight measurement, applicable to the clamping and positioning of large workpieces such as aircraft structural components and central wing slats in the aerospace industry, mainly including the following steps: S1. On the three-dimensional model of the workpiece, the measurement points and measurement paths are planned to generate a measurement program. The measurement program includes three measurement tasks: leveling, finding the origin, and finding the angular direction. The three measurement tasks constrain the six degrees of freedom of the workpiece in space step by step.

[0023] Specifically, based on the three-dimensional model of the workpiece, combined with the structural features and positioning reference requirements of the workpiece, measurement points and measurement paths are planned on the three-dimensional model, and corresponding measurement programs are generated. According to the geometric features of the workpiece and the degrees of freedom to be constrained, the measurement task is divided into three measurement tasks: leveling, origin finding, and angular direction finding, so as to constrain the six degrees of freedom of the workpiece in space step by step.

[0024] The method for establishing the leveling measurement task is as follows: select measurement points on the main datum plane of the workpiece, plan the measurement path based on the measurement strategy parameters, and generate the corresponding measurement program. The purpose of the leveling measurement task is to eliminate the translational degree of freedom of the workpiece in the normal direction of the main datum plane (Z-axis direction of the machine tool coordinate system) and constrain the rotational degree of freedom of the workpiece around the X-axis and Y-axis of the machine tool coordinate system, thereby ensuring the parallelism between the main datum plane of the workpiece and the datum plane of the machine tool.

[0025] The method for establishing the original measurement task is as follows: select measurement points on an auxiliary datum plane orthogonal to the main datum plane of the workpiece, plan the measurement path based on the measurement strategy parameters, and generate the corresponding measurement program. The purpose of finding the original measurement task is to eliminate the translational degrees of freedom of the workpiece in the datum plane (constraining translation in the X and Y directions) and determine the position datum of the workpiece in the plane.

[0026] The method for establishing an angular measurement task is as follows: Measurement points on geometric features sensitive to angular changes are selected, and a measurement path is planned based on measurement strategy parameters to generate the corresponding measurement program. Geometric features sensitive to angular changes include positioning holes, feature planes orthogonal to the main datum plane, feature surfaces parallel to the XZ or YZ plane of the machine tool coordinate system, and feature edges parallel to the X or Y axis of the machine tool coordinate system. The purpose of the angular measurement task is to constrain the workpiece's rotational degree of freedom around the Z-axis and determine the workpiece's angular orientation in the plane.

[0027] S2, such as Figure 2 As shown, the workpiece is initially clamped so that it is roughly in the vicinity of the precise clamping position. High-precision placement is not required; it is only necessary to ensure that the workpiece is within the measurable range of the machine tool.

[0028] S3, such as Figure 3 As shown in the upper middle section, the machine tool performs a leveling measurement task, acquires actual leveling measurement data, compares the actual leveling measurement data with the theoretical leveling data, calculates the deviation matrix, and generates a corresponding leveling CNC program based on the deviation matrix. Based on the leveling CNC program, the machine tool is driven to perform planar posture adjustment, thereby correcting the planar posture of the workpiece.

[0029] The specific method for obtaining the leveling CNC program is as follows: Based on the actual measurement point set data and the theoretical measurement point set data for leveling, the optimal rigid body transformation is solved to calculate the rotation matrix and translation vector. The translation deviation in the Z-axis direction and the rotation deviation around the X-axis or Y-axis are extracted from the translation deviation and rotation deviation, and the corresponding CNC program is generated based on the translation deviation and rotation deviation.

[0030] In actual machine tool measurement, if the workpiece is not significantly tilted during initial clamping, the accurate Z-direction translation value can be obtained from the first calculation. If there is tilt, the initial Z-direction translation deviation may be inaccurate. Usually, after completing the initial leveling, it is necessary to perform the measurement again and update the deviation matrix to obtain a more accurate Z-direction translation value and rotation angle around the X / Y axis, thereby ensuring that the flatness and posture of the workpiece meet the requirements.

[0031] S4, such as Figure 3 As shown in the middle section, the machine tool performs the origin-finding measurement task, obtains the actual measurement data of the origin-finding measurement, compares the actual measurement data of the origin-finding with the theoretical data of the origin-finding, calculates the deviation matrix, and generates the corresponding origin-finding CNC program based on the calculation results. Based on the origin-finding CNC program, the machine tool is driven to adjust the position of the workpiece, thereby determining the position reference of the workpiece and aligning the origin of the workpiece with the origin of the machine tool coordinate system.

[0032] The specific method for obtaining the original CNC program is as follows: the coordinates of the actual measurement points and the theoretical measurement points are organized into a matrix form, and the deviation vector set of each measurement point is obtained by subtracting them point by point; then the coordinate components of all deviation vectors are accumulated and averaged to obtain the average translation of the workpiece as a whole; then, according to the axial constraint parameters determined by S3, only the translation components in the specified direction are retained to obtain the final translation vector, and the corresponding CNC program is generated based on the translation vector.

[0033] The machine tool then adjusts the workpiece position according to the CNC program to determine the workpiece's position reference, aligning the workpiece's origin with the machine tool's coordinate system origin.

[0034] S5, such as Figure 3 As shown in the lower middle section, the machine tool performs the angular direction measurement task, obtains the actual measurement data of the angular direction, compares the actual measurement data of the angular direction with the theoretical data of the angular direction, calculates the rotational deviation angle, and generates the corresponding angular direction CNC program based on the calculation result. Based on the angular direction CNC program, the machine tool is driven to perform angular adjustment, thereby determining the angular posture of the workpiece and making the workpiece direction consistent with the machine tool coordinate system.

[0035] The method for obtaining the angular direction CNC program is as follows: by extracting the X-axis coordinates and Y-axis coordinates of the theoretical measurement point and the actual measurement point of the angular direction, two two-dimensional vectors u and v representing the theoretical direction and the actual direction are constructed respectively. Then, the angle between the two vectors is calculated by using the cross product and dot product of the vectors, thereby obtaining the rotational deviation angle of the workpiece relative to the theoretical reference in the plane. The corresponding CNC program is generated based on the rotational deviation angle.

[0036] The machine tool then performs angular adjustment of the coordinate system according to the CNC program, thereby determining the angular orientation of the workpiece and making the workpiece orientation consistent with the machine tool coordinate system.

[0037] In addition, to ensure the workpiece clamping and alignment accuracy, the present invention provides a method for clamping and aligning large structural parts based on in-machine measurement, which further includes step S6: replanning the re-measurement points and re-measurement paths on the three-dimensional model of the workpiece, performing re-measurement on the machine tool, obtaining the actual re-measurement results, comparing the actual re-measurement results with the theoretical re-measurement points, and determining that the workpiece has been accurately aligned if the deviation is within a predetermined range; if the deviation exceeds the predetermined range, repeating steps S1-S5 until the deviation is within the predetermined range.

[0038] Specifically: After completing the three sets of adjustment steps—leveling, homing, and angular alignment—that is, after completing steps S1-S5, to ensure alignment accuracy, re-measurement points are planned on the workpiece's 3D model, along with corresponding re-measurement paths. The planned re-measurement points should cover the main datum plane, auxiliary datum plane, and angularly sensitive feature points, and be evenly distributed in key areas of the workpiece to verify the accuracy of the aforementioned leveling, homing, and angular alignment adjustments. Simultaneously, a re-measurement program is generated. Subsequently, the re-measurement program is executed to obtain actual re-measurement data; the actual re-measurement data is compared with the theoretical re-measurement point data in the 3D model, the deviation of each re-measurement point is calculated, and the deviation label for each re-measurement point is displayed on the interface. If all remeasured deviations are within the predetermined range, which is the preset allowable range for alignment accuracy, then the workpiece can be determined to have been accurately aligned and can proceed to the subsequent processing steps. If there are deviations that exceed the predetermined range, then the corresponding leveling, homing, or angular alignment steps are returned based on the deviation results. That is, steps S1-S5 are repeated to recalculate and adjust the required CNC program and drive the machine tool to make corrections until all deviations of the workpiece meet the accuracy requirements, thus confirming that the workpiece has been accurately aligned.

[0039] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0040] Where there is no conflict, the embodiments and features described above can be combined with each other. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for clamping and aligning large structural components based on in-machine measurement, characterized in that, Includes the following steps: S1. On the three-dimensional model of the workpiece, the measurement points and measurement paths are planned to generate a measurement program. The measurement program includes three measurement tasks: leveling, finding the origin, and finding the angular direction. The three measurement tasks constrain the six degrees of freedom of the workpiece in space step by step. The method for establishing the leveling measurement task in step S1 is as follows: select measurement points on the main reference plane of the workpiece, plan the measurement path in combination with the measurement strategy parameters, and generate the corresponding measurement program. The method for establishing the original measurement task in step S1 is as follows: select measurement points on the auxiliary reference surface orthogonal to the main reference surface of the workpiece, plan the measurement path in combination with the measurement strategy parameters, and generate the corresponding measurement program. The method for establishing the angular direction measurement task in step S1 is as follows: select measurement points on geometric features that are sensitive to angular changes, plan the measurement path in combination with measurement strategy parameters, and generate the corresponding measurement program. S2. Initially clamp the workpiece; S3. The machine tool performs the leveling measurement task, obtains the actual leveling measurement data, compares the actual leveling measurement data with the leveling theoretical data, calculates the deviation matrix, and generates the corresponding leveling CNC program based on the deviation matrix. Based on the leveling CNC program, the machine tool is driven to perform planar posture adjustment, thereby correcting the planar posture of the workpiece. The method for obtaining the leveling CNC program in step S3 is as follows: based on the actual leveling measurement point set data and the leveling theoretical measurement point set data, the optimal rigid body transformation is solved to calculate the rotation matrix and translation vector, and the translation deviation in the Z-axis direction and the rotation deviation around the X-axis or Y-axis are extracted from them, thereby generating the corresponding CNC program based on the translation deviation and rotation deviation. S4. The machine tool performs the origin-finding measurement task, obtains the actual measurement data of the origin-finding measurement, compares the actual measurement data of the origin-finding with the theoretical data of the origin-finding, calculates the deviation matrix, and generates the corresponding origin-finding CNC program based on the calculation results. Based on the origin-finding CNC program, the machine tool is driven to adjust the position of the workpiece, thereby determining the position reference of the workpiece and aligning the origin of the workpiece with the origin of the machine tool coordinate system. In step S4, the method for obtaining the original CNC program is as follows: the coordinates of the original actual measurement points and the original theoretical measurement points are organized into a matrix form, and the deviation vector set of each measurement point is obtained by subtracting them point by point; then the coordinate components of all deviation vectors are accumulated and averaged to obtain the average translation amount of the workpiece as a whole; and then the corresponding CNC program is generated based on the average translation amount. S5. The machine tool performs the angular direction measurement task, obtains the actual measurement data of the angular direction, compares the actual measurement data of the angular direction with the theoretical data of the angular direction, calculates the rotation deviation angle, and generates the corresponding angular direction CNC program based on the calculation result. Based on the angular direction CNC program, the machine tool is driven to perform angular adjustment, thereby determining the angular orientation of the workpiece and making the workpiece direction consistent with the machine tool coordinate system. In step S5, the method for obtaining the angular direction CNC program is as follows: by extracting the X-axis coordinates and Y-axis coordinates of the theoretical measurement point and the actual measurement point of the angular direction, two two-dimensional vectors u and v representing the theoretical direction and the actual direction are constructed respectively. Then, the angle between the two vectors is calculated by using the cross product and dot product of the vectors, thereby obtaining the rotational deviation angle of the workpiece relative to the theoretical reference in the plane. The corresponding CNC program is generated based on the rotational deviation angle.

2. The method for clamping and aligning large structural components based on in-machine measurement as described in claim 1, characterized in that: It also includes S6, which replans the retest points and retest measurement paths on the 3D model of the workpiece, the machine tool performs the retest, and obtains the actual retest results. The actual retest results are compared with the theoretical retest points. If the deviation is within the predetermined range, it is determined that the workpiece has been accurately aligned; if the deviation exceeds the predetermined range, steps S1-S5 are repeated until the deviation is within the predetermined range.

3. The method for clamping and aligning large structural components based on in-machine measurement as described in claim 1, characterized in that: Step S1 specifically includes: based on the three-dimensional model of the workpiece, combined with the structural features and positioning reference requirements of the workpiece, planning measurement points and measurement paths on the three-dimensional model, and generating corresponding measurement programs; according to the geometric features of the workpiece and the degrees of freedom to be constrained, dividing the measurement task into three measurement tasks: leveling, finding the origin, and finding the angular direction, so as to constrain the six degrees of freedom of the workpiece in space step by step.

4. The method for clamping and aligning large structural components based on in-machine measurement as described in claim 3, characterized in that: Geometric features sensitive to angular changes include locating holes, feature planes orthogonal to the main datum plane, feature planes parallel to the XZ or YZ plane of the machine tool coordinate system, and feature edges parallel to the X or Y axis of the machine tool coordinate system.

Images