Geometric self-adaptive machining method and device for free-form surface

Abstract

The invention discloses a free-form surface geometric self-adaptive machining method and device, and the method comprises the steps: obtaining a CAD model of a free-form surface workpiece, generating a machining path and measurement information of a blank workpiece based on the CAD model, and transmitting a measurement control instruction to a three-coordinate measuring machine based on the measurement information, measuring a blank workpiece which is clamped on the numerical control machine tool and is obtained based on the machining path, obtaining three-coordinate data Pme of each target measuring point, judging the machining precision of the blank workpiece according to the CAD model and the Pme, obtaining an ideal semi-finish machining CAD model of the free-form surface workpiece when the machining precision is smaller than a preset threshold value, and carrying out semi-finish machining on the free-form surface workpiece according to the ideal semi-finish machining CAD model. The method comprises the following steps: constructing a mirror surface Mm between a CAD model and an ideal semi-finishing CAD model, obtaining reflection point coordinate data Pcom corresponding to each Pme based on the Pmes and the Mm, obtaining an error spectrum based on all the Pcom, and performing finish machining on a blank workpiece by adopting the error spectrum as a finish machining path, so that the machining precision can be ensured in the machining process, the machining efficiency is improved, and the machining cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of mechanical processing, and in particular to a method and device for adaptive processing of free-form surface geometry. Background Art

[0002] Free-form surface parts have excellent aerodynamic and fluid properties and are widely used in aerospace, shipbuilding, marine, automotive and other fields. The machining accuracy and quality of free-form surface parts have a profound impact on the performance of the parts. However, the machining accuracy of free-form surface parts is often restricted by the motion accuracy of the machine tool itself. Therefore, corresponding methods are needed to improve the machining accuracy of parts to meet the growing demand.

[0003] At present, the adaptive machining method is mainly used to realize the machining of free-form surface parts. In order to obtain the error distribution of a certain part during the machining process, the adaptive machining method needs to set different machining parameters and conduct a large number of machining experiments to construct a complex machining model. The machining error of the surface part is characterized by establishing a polynomial function of the machining model, and the tool trajectory is corrected based on this condition to reduce the machining error. However, for different parts and different machine tools, the machining model may be different. If the machined parts or machine tools change, the machining model needs to be re-established. The machining process wastes raw materials, the machining efficiency is low, and the machining process is cumbersome. It is difficult to meet the requirements of machining efficiency and machining cost in actual generation; at the same time, in the current adaptive machining process, the detection results of the three-coordinate measuring machine are used to compensate for the machining error. In the subsequent machining process, it is necessary to modify the tool radius in the computer-aided manufacturing (CAM, full name Computer Aided Manufacturing) software to perform error compensation to regenerate the tool trajectory for fine machining. The defect of this method is that the regenerated tool trajectory for fine machining can only move outward or inward by a constant value, and cannot provide specific error compensation at a specific position, and the machining accuracy is low. Summary of the invention

[0004] The present application provides a free-form surface geometry adaptive processing method and device, which can ensure processing accuracy during the processing of free-form surface parts, improve processing efficiency, and reduce processing costs.

[0005] On the one hand, an embodiment of the present application provides a free-form surface geometry adaptive processing method, comprising:

[0006] Acquire a CAD model of a free-form surface workpiece, and generate a processing path and measurement information of a blank workpiece based on the CAD model, wherein the measurement information includes a plurality of target measurement points of the blank workpiece;

[0007] Based on the measurement information, a measurement control instruction is sent to a three-dimensional coordinate measuring machine, and the blank workpiece obtained based on the processing path clamped on the CNC machine tool is measured to obtain the three-dimensional coordinate data P of each target measuring point. me ;

[0008] According to the CAD model and P me The machining accuracy of the rough workpiece is judged. When the machining accuracy is less than a preset threshold, an ideal semi-finishing CAD model of the free-form surface workpiece is obtained, and a mirror surface M is constructed between the CAD model and the ideal semi-finishing CAD model. m , based on P me and M m Get each P me The corresponding reflection point coordinate data P com , based on all P com Obtaining an error map, and using the error map as a finishing path;

[0009] A finishing control instruction is sent to a tool of the numerically controlled machine tool based on the finishing path, and the rough workpiece is finished to obtain the free-form surface workpiece.

[0010] On the other hand, the embodiment of the present application further provides a free-form surface geometry adaptive processing device, including a processor and a memory:

[0011] The memory is used to store the free-form surface geometry adaptive processing program;

[0012] The processor is used to read the free-form surface geometry adaptive processing program and perform the free-form surface geometry adaptive processing method as described in the above embodiment.

[0013] Compared with the related art, a free-form surface geometry adaptive processing method and device in an embodiment of the present application does not require a large number of processing tests, eliminates the process of establishing a processing model, saves time, avoids waste of raw materials, and reduces processing costs; uses an error map as a finishing path, and changes the under-cut positions on the rough workpiece into over-cut positions to ensure the correct processing allowance, and performs under-cut processing on the over-cut positions on the rough workpiece, so that the free-form surface workpiece obtained after finishing processing is closer to the CAD model of the free-form surface workpiece, wherein the CAD model is an ideal model of the free-form surface workpiece, which ensures the processing accuracy of the free-form surface parts and improves the processing efficiency.

[0014] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0016] Figure 1 is a flow chart of a free-form surface geometry adaptive processing method according to an embodiment of the present application;

[0017] Figure 2 is a schematic diagram of obtaining reflection points through a mirror surface in an embodiment of the present application;

[0018] Figure 3 It is a flow chart of the free-form surface geometry adaptive processing method of the specific example of the present application;

[0019] Figure 4 It is a schematic diagram of a free-form surface geometry adaptive processing device according to an embodiment of the present application. DETAILED DESCRIPTION

[0020] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0021] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0022] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0023] The present application embodiment provides a free-form surface geometry adaptive processing method, including steps S1000-S4000, such as Figure 1 As shown,

[0024] S1000: Acquire a CAD model of a free-form surface workpiece, and generate a processing path and measurement information of a blank workpiece based on the CAD model, wherein the measurement information includes a plurality of target measurement points of the blank workpiece;

[0025] S2000: Sending a measurement control instruction to a three-dimensional coordinate measuring machine based on the measurement information, measuring the blank workpiece obtained based on the processing path clamped on the CNC machine tool, and obtaining the three-dimensional coordinate data P of each target measuring point me ;

[0026] S3000: According to the CAD model and P me The machining accuracy of the rough workpiece is judged. When the machining accuracy is less than a preset threshold, an ideal semi-finishing CAD model of the free-form surface workpiece is obtained, and a mirror surface M is constructed between the CAD model and the ideal semi-finishing CAD model. m , based on P me and M m Get each P me The corresponding reflection point coordinate data P com , based on all P com Obtaining an error map, and using the error map as a finishing path;

[0027] S4000: Sending a finishing control instruction to a tool of the CNC machine tool based on the finishing path, and finishing the rough workpiece to obtain the free-form surface workpiece.

[0028] In this embodiment, the free-form surface workpiece can be a car body, an airplane wing, a propeller, a building facade, an optical element, a bearing, a gear, sports equipment, etc. The above examples of free-form surface workpieces are all exemplary descriptions and are not limitations of this application, and will not be described in detail herein.

[0029] In this embodiment, the free-form surface workpiece includes only one free-form surface; for a combined workpiece including multiple free-form surfaces, steps S1000-S4000 can be performed on each free-form surface to obtain workpieces of various free-form surfaces, and then multiple free-form surfaces can be combined to obtain a finely machined combined workpiece.

[0030] In this embodiment, the CNC machine tool for processing free-form surface workpieces can be a five-axis machine tool, a laser processing machine tool, an ultrasonic processing machine tool, an electric spark processing machine tool, etc. The above examples of CNC machine tools are all illustrative descriptions and are not limitations of this application. They will not be described one by one in this article.

[0031] In this embodiment, the fixture of the CNC machine tool is used to fix the blank workpiece. During the entire process of steps S2000-S4000, the fixture can be used to fix the blank workpiece to the CNC machine tool, and then the three-coordinate measuring machine is used to measure the blank workpiece until the finishing of the blank workpiece is finally completed. The position of the blank workpiece can always remain unchanged, that is, the measurement of the blank workpiece is in-situ measurement, and the finishing of the blank workpiece is in-situ finishing. There is no need to disassemble and clamp from measurement to finishing, which avoids the movement of the blank workpiece, avoids the positioning error and deformation error caused by secondary clamping and the deformation introduced during the transportation process, and eliminates the time-consuming transportation.

[0032] In this embodiment, the three-coordinate measuring machine can be selected according to the size of the free-form surface workpiece. For example, a gantry-type three-coordinate measuring machine or a bridge-type measuring machine can be selected for a large free-form surface workpiece, and a horizontal arm-type measuring machine can be selected for a small free-form surface workpiece. In terms of the measurement principle, a contact-type mechanical three-coordinate measuring machine or a non-contact laser three-coordinate measuring machine can be used.

[0033] In this embodiment, the processing of the free-form surface workpiece can be divided into three stages: rough machining, semi-finishing and finishing. Among them, the tool for rough machining can be a flat-bottomed milling cutter, and the tool for semi-finishing and finishing can be a ball-end milling cutter; rough machining mainly involves the processing of raw materials, and the raw materials after rough machining will present the prototype of the free-form surface workpiece, and there will be more "steps"; semi-finishing is a connecting link in the entire machining process, which can remove the excess left after rough machining, and improve the dimensional accuracy and surface quality based on the rough machining results to obtain a blank workpiece. A machining allowance of 0.2 mm can be retained during semi-finishing; finally, a free-form surface workpiece is obtained by finishing the blank workpiece. During finishing, under-cutting is performed on the over-cut parts of the blank workpiece, and over-cutting is performed on the under-cut parts of the blank workpiece to ensure the accuracy of the free-form surface workpiece after finishing.

[0034] In this embodiment, after rough machining, semi-finishing programming can be performed by CAD software to generate a semi-finishing path and an ideal semi-finishing CAD model. The ideal semi-finishing CAD model guides the semi-finishing process to ensure that the semi-finishing allowance is uniform and prepares for finishing.

[0035] The free-form surface geometry adaptive processing method of this embodiment does not require a large number of processing tests, eliminates the process of establishing a processing model, saves time, avoids waste of raw materials, and reduces processing costs; uses an error map as a finishing path, and changes the under-cut positions on the rough workpiece into over-cut positions to ensure the correct processing allowance, and performs under-cut processing on the over-cut positions on the rough workpiece, so that the free-form surface workpiece obtained after finishing processing is closer to the CAD model of the free-form surface workpiece, wherein the CAD model is an ideal model of the free-form surface workpiece, which ensures the processing accuracy of the free-form surface parts and improves the processing efficiency.

[0036] In an exemplary embodiment, the CAD model can be a surface model S(u, v) located in a parameter space, wherein the parameter space includes a main direction and an orthogonal direction orthogonal to the main direction, u represents the main direction parameter of S(u, v) in the parameter space, and v represents the orthogonal direction parameter of S(u, v) in the parameter space.

[0037] In this embodiment, the main direction of the parameter space can be the direction in which the tangent slope of the surface model S (u, v) changes fastest. The orthogonal direction is orthogonal to the main direction. The main direction and the orthogonal direction can jointly reflect the spatial distribution of the surface model S (u, v). Any point of the surface model S (u, v) in the parameter space can be represented by a combination of u and v.

[0038] In this embodiment, the ideal semi-finishing CAD model and the surface model S(u, v) are located in the same parameter space, and the ideal semi-finishing CAD model is also a surface model.

[0039] In an exemplary embodiment, the “generating a machining path and measurement information of a blank workpiece based on the CAD model” in step S1000 may include steps S1100-S1300:

[0040] S1100: Generate the machining path of the corresponding blank workpiece based on S(u, v), including a rough machining path and a semi-finishing machining path;

[0041] S1200: planning target measuring points for S(u, v) based on a preset number of target measuring points N;

[0042] S1300: Planning a measurement path based on the planned multiple target measuring points, wherein the measurement path is a movement path of the three-dimensional coordinate measuring machine passing through the multiple target measuring points in sequence during the measurement of the blank workpiece; wherein the measurement information also includes the measurement path.

[0043] In this embodiment, rough machining control instructions can be generated according to the rough machining path, and the rough machining control instructions are sent to the tool used for rough machining of the CNC machine tool to complete the rough machining of the raw material; semi-finishing control instructions can be generated according to the semi-finishing path, and the semi-finishing control instructions are sent to the tool used for semi-finishing of the CNC machine tool to complete the semi-finishing of the raw material and obtain a blank workpiece.

[0044] In this embodiment, the processing path generated in step S1100 may also include an initial finishing path. If, when judging the processing accuracy of the blank workpiece in step S3000, the processing accuracy is not less than a preset threshold, the finishing of the blank workpiece is still completed according to the initial finishing path.

[0045] In this embodiment, when executing step S1200 to plan the target measuring points, the uniform distribution principle or the key feature priority principle can be followed. The uniform distribution principle means that the target measuring points are evenly distributed to avoid overcrowding or sparseness in certain areas; the key feature priority principle means that more target measuring points are preferentially configured at key parts of the free-form surface workpiece, such as the mating surface position, the positioning hole position, etc.

[0046] In an exemplary embodiment, step S1200 may include steps S1210-S1250:

[0047] S1210: Discretize S(u, v) into n curves S(u i , v) or S(u, v i), wherein i=1, 2, ... n, and n is an integer greater than 1;

[0048] S1220: Evenly distribute the N target measuring points on the n space curves, wherein for each space curve, there are t target measuring points; wherein the target measuring points include anchor points and even points on the space curve to which they belong, the anchor points include endpoints and extreme points of the space curve, and the positions of the even points on the space curve are p 0 , where t is an integer greater than 1, N = m;

[0049] S1230: Obtain the Gaussian curvature g(u, v) of each anchor point, and perform normalization based on the Gaussian curvatures of all anchor points to obtain the normalized Gaussian curvature g corresponding to each anchor point. k ;

[0050] S1240: According to the normalized Gaussian curvature g k , respectively update the initial position of each uniform point to obtain the final position corresponding to each uniform point;

[0051] S1250: The positions of all anchor points and the final positions of all uniform points are taken as the positions of the target measuring points.

[0052] In this embodiment, in step S1210, S(u, v) is discretized into n curves S(u i , v) or S(u, v i ), S(u i , v) is discretized into n curves in the main direction, S(u, v i ) means discretizing into n curves in orthogonal directions. Just select one direction for discretization. The size of n can be set according to the size of S(u, v).

[0053] In this embodiment, step S1220 is a step for planning the initial position of the target measuring point. The principle adopted is the uniform distribution principle. N target measuring points are evenly distributed on n space curves. In subsequent steps, the anchor point position is always maintained at the initial position, and only step S1240 is used to update the position of each uniform point.

[0054] In this embodiment, the Gaussian curvature g(u, v) described in step S1230 represents the local property of one of the anchor points on S(u, v), which is only related to the geometric shape near the anchor point; after normalizing the Gaussian curvatures g(u, v) of all anchor points, the normalized Gaussian curvature g corresponding to each anchor point is obtained. k , g corresponding to all anchor points k The sum is 1.

[0055] In an exemplary embodiment, step S1240 may include: performing one or more rounds of iterations, taking the position corresponding to each uniform point obtained in the last iteration of the last round as the final position, wherein each round of iteration includes at most A iterations, and the hyperparameter β corresponding to each round of iteration is different, and each round of iteration may include steps S1241-S1242:

[0056] S1241: Setting the hyperparameter β corresponding to the current round;

[0057] S1242: According to the hyperparameter β and the normalized Gaussian curvature g k Perform B iterations corresponding to the current round, where 1≤B≤A;

[0058] In this embodiment, if the current tolerance is less than the tolerance threshold for the first time in the Bth iteration of the current round, the current round is taken as the last round and the iteration is taken as the last iteration; if the current tolerance is still not less than the tolerance threshold until the Ath iteration of the current round, the next round of iteration is performed.

[0059] In this embodiment, after one or more rounds of iterations, the position of the uniform point will be changed. The larger the hyperparameter β is, the closer the target measurement point is to the normalized Gaussian curvature g. k Areas with high values ​​are denser, and the normalized Gaussian curvature g k Areas with small values ​​will be more sparse; if the hyperparameter β is smaller, the distribution of target measurement points will be closer to a uniform distribution.

[0060] In this embodiment, if multiple rounds of iterations are required, the hyperparameter β can be changed from small to large to ensure that the hyperparameter β used in each round of iteration is different and the hyperparameter β used in the same round of iteration remains unchanged; if in the current round of iteration, A iterations are performed and the current tolerance is still not less than the tolerance threshold, it means that the value of the hyperparameter β in the current round is unreasonable, then the value of the hyperparameter β is changed for the next round of iteration.

[0061] In an exemplary embodiment, step S1242 may include: setting B to 1, and performing a Bth iteration, wherein each iteration includes steps S12421-S12423:

[0062] S12421: According to the hyperparameter β and the normalized Gaussian curvature g corresponding to the current round k Get the current position p corresponding to each uniform point respectively j , where the current position p j Based on the previous position p obtained in the previous iteration of the current round j-1Calculate the previous position p at the first iteration of the current round j-1 For p 0 ;

[0063] S12422: Based on the current positions p of all the uniform points j Reconstruct the surface with the positions of all anchor points to obtain the current surface;

[0064] S12423: Calculate the current tolerance according to the current surface and the surface model S(u,v), and determine the relationship between the current tolerance and the tolerance threshold. When the current tolerance is not less than the tolerance threshold and B is less than A, perform the next iteration of the current round, increase B by 1, and change the current position p of each uniform point to j As the previous position p of the next iteration of the current round j-1 .

[0065] In an exemplary embodiment, when executing step S12421, each of the uniform points may be used as a current uniform point, and steps S124211-S124213 may be performed on the current uniform point:

[0066] S124211: Determine the previous position p of the current uniform point j-1 The nearest Z anchor points P z , where Z ≥ 2, z = 1, ... Z;

[0067] S124212: Get p respectively j-1 To the Z anchor points P z The parameter distance d z , the current uniform point points to the Z anchor points P respectively z The parameter vector The Z anchor points P z The corresponding normalized Gaussian curvature g z ;

[0068] S124213: According to the formula Calculate the current position p of the current uniform point j .

[0069] In this embodiment, taking Z=2 as an example, steps S124211-S124213 are described to determine the previous position p of the current uniform point. j-1 The two nearest anchor points P1 and P2; get p j-1 The parameter distance d1 to P1, the parameter vector of the current uniform point pointing to P1 Normalized Gaussian curvature g1 of P1; get p j-1 The parameter distance d2 to P2, the parameter vector of the current uniform point pointing to P2 The normalized Gaussian curvature g2 of P2; according to the formula Calculate the current position p of the current uniform point j .

[0070] In this embodiment, after the final positions of all uniform points are obtained, steps S1250 and S1300 may be sequentially executed to obtain a measurement path. When executing step S2000, a measurement control instruction may be generated according to the measurement path, and the measurement control instruction may be sent to a three-dimensional coordinate measuring machine to measure the blank workpiece clamped on the CNC machine tool, and obtain the three-dimensional coordinate data P of each target measuring point. me .

[0071] In this embodiment, according to all P me The contour of the rough workpiece can be obtained, and then step S3000 is executed to compare the contour of the rough workpiece with the CAD model of the free-form surface workpiece, that is, to compare the contour of the rough workpiece with the surface model S(u, v), so as to obtain the machining accuracy of the rough workpiece. When the machining accuracy is less than a preset threshold, it is necessary to regenerate a finishing path to replace the initial finishing path. When regenerating the finishing path, the mirror M can be constructed according to the ideal semi-finishing CAD model of the free-form surface workpiece and the surface model S(u, v). m , mirror M m It is the surface between the ideal semi-finished CAD model and the surface model S(u, v), the mirror surface M m Distance to the ideal semi-finished CAD model and mirror surface M m The distance to the surface model S(u, v) is equal, such as Figure 2 shown.

[0072] In an exemplary embodiment, the "based on P me and M m Get each P me The corresponding reflection point coordinate data P com ” may include steps S3100-S3400:

[0073] S3100: According to any point P on S(u, v) f Determine the main direction parameter u corresponding to this point f and the orthogonal direction parameter v f ;

[0074] S3200: Acquire corresponding point P on the ideal semi-finishing CAD model s , where P s The main direction parameter and the orthogonal direction parameter are u f and v f ;

[0075] S3300: Utilizing formulas Get the construction vector n of S(u,v);

[0076] S3400: For each P me Perform the following operations respectively: me Along the construction vector n to the mirror M m Extension, obtain the extension direction and the mirror M m The intersection point P m ; Get the P me With P m The distance D m ; Using formula P com =P me -2D m ·nGet the P me The corresponding reflection point coordinate data P com .

[0077] In this embodiment, for a surface model S(u, v), when executing step S3100, any point P can be selected on S(u, v). f , then determine P in the parameter space of the surface model S(u, v) f The main direction parameter u f and the orthogonal direction parameter v f , when executing step S3200, based on u obtained in S3100 f and v f Get the corresponding point P on the ideal semi-finishing CAD model s , that is, P f and P f The main direction parameters and orthogonal direction parameters are the same.

[0078] In this embodiment, for the same surface model S(u, v), the direction of its construction vector n is the same at any point; by executing step S3400, P can be obtained. me Based on the mirror M m The reflection point P com , that is, P me and P com Based on the mirror M m The symmetric point of Figure 2 shown.

[0079] In an exemplary embodiment, the step S3000 of “based on all P com Obtaining an error map and using the error map as a finishing path may include step S3500:

[0080] S3600: Based on all P comSurface interpolation reconstruction is performed to obtain the error map, and the error map is used as the finishing path.

[0081] In this embodiment, all reflection point coordinate data P corresponding to the surface model S (u, v) can be com Surface interpolation reconstruction is performed to generate an error map, which can be used to replace the initial finishing path. The error map is as follows: Figure 2 shown.

[0082] In order to illustrate the free-form surface geometry adaptive processing method of the embodiment of the present application, a specific example is used to describe it in detail below, including steps S1-S10, such as Figure 3 As shown:

[0083] S1: Obtain a CAD model of a free-form surface workpiece, the CAD model is a surface model S (u, v);

[0084] S2: Generate rough machining path, semi-finishing path and initial finishing path based on the surface model S(u, v), and generate target measuring points and measuring path;

[0085] S3: performing rough machining and semi-finishing machining according to the rough machining path and the semi-finishing path respectively to obtain a blank workpiece;

[0086] S4: Clamp the blank workpiece on the CNC machine tool, measure the blank workpiece according to the target measuring point and measuring path, and obtain the three-coordinate data P of each target measuring point me , according to the three-coordinate data P me Obtain the contour of the blank workpiece;

[0087] S5: Compare the contour of the rough workpiece with the surface model S (u, v) to determine the relationship between the machining accuracy and the preset threshold. When the machining accuracy is less than the preset threshold, execute step S6; when the machining accuracy is not less than the preset threshold, execute step S10;

[0088] S6: Obtain the ideal semi-finishing CAD model of the free-form surface workpiece, and construct a mirror surface M between the surface model S(u, v) and the ideal semi-finishing CAD model m ;

[0089] S7: Determine the construction vector n of the surface model S(u, v), and convert each P me Along the construction vector n to the mirror M m Extension, obtain the extension direction and the mirror M m The intersection point P m , get the P me With P m The distance D m ; Using formula P com =Pme -2D m ·nGet the P me The corresponding reflection point coordinate data P com ;

[0090] S8: Based on all reflection point coordinate data P com Perform surface interpolation to obtain an error map, and use the error map as a finishing path;

[0091] S9: finishing the rough workpiece based on the finishing path;

[0092] S10: Finish machining the rough workpiece based on the initial finishing path.

[0093] In this specific example, after the rough workpiece is clamped on the CNC machine tool in step S4, the position of the rough workpiece remains unchanged until the finishing is completed, that is, until step S9 or S10 is completed, that is, steps S4-S10 of this specific example are the process of in-situ measurement and in-situ finishing.

[0094] The present application also provides a free-form surface geometry adaptive processing device, such as Figure 4 As shown, including a processor and a memory,

[0095] The memory is used to store the free-form surface geometry adaptive processing program;

[0096] The processor is used to read the free-form surface geometry adaptive processing program and perform the free-form surface geometry adaptive processing method as described in the above embodiment.

[0097] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for geometrically adaptive machining of free-form surfaces, characterized in that: include: Acquire a CAD model of a free-form surface workpiece, and generate a processing path and measurement information of a blank workpiece based on the CAD model, wherein the measurement information includes a plurality of target measurement points of the blank workpiece; Based on the measurement information, a measurement control instruction is sent to a three-dimensional coordinate measuring machine, and the blank workpiece obtained based on the processing path clamped on the CNC machine tool is measured to obtain the three-dimensional coordinate data P of each target measuring point. me ; According to the CAD model and P me The machining accuracy of the rough workpiece is judged. When the machining accuracy is less than a preset threshold, an ideal semi-finishing CAD model of the free-form surface workpiece is obtained, and a mirror surface M is constructed between the CAD model and the ideal semi-finishing CAD model. m , based on P me and M m Get each P me The corresponding reflection point coordinate data P com , based on all P com Obtaining an error map, and using the error map as a finishing path; A finishing control instruction is sent to a tool of the numerically controlled machine tool based on the finishing path, and the rough workpiece is finished to obtain the free-form surface workpiece.

2. The free-form surface geometry adaptive processing method according to claim 1, characterized in that: The CAD model is a surface model S(u,v) located in a parameter space, wherein the parameter space includes a main direction and an orthogonal direction orthogonal to the main direction, u represents the main direction parameter of S(u,v) in the parameter space, and v represents the orthogonal direction parameter of S(u,v) in the parameter space.

3. The free-form surface geometry adaptive processing method according to claim 2, characterized in that: The step of generating a machining path and measurement information of a rough workpiece based on the CAD model includes: Generate the machining path of the corresponding rough workpiece based on S(u,v), including a rough machining path and a semi-finishing machining path; Plan the target measuring points S(u,v) based on the preset number of target measuring points N; A measurement path is planned based on the planned multiple target measuring points, wherein the measurement path is a movement path of the three-dimensional coordinate measuring machine passing through the multiple target measuring points in sequence during the measurement process of the blank workpiece; wherein the measurement information also includes the measurement path.

4. The free-form surface geometry adaptive processing method according to claim 3, characterized in that: The planning of target measuring points for S(u,v) based on the preset number of target measuring points N includes: Discretize S(u,v) into n curves S(u i ,v) or S(u,v i ), where i=1, 2, ... n, and n is an integer greater than 1; The N target measuring points are evenly distributed on the n space curves, wherein for each space curve, there are t target measuring points; wherein the target measuring points include anchor points and uniform points on the space curve to which they belong, the anchor points include endpoints and extreme points of the space curve, and the position of the uniform point on the space curve is p 0 , where t is an integer greater than 1, N = tn; Obtain the Gaussian curvature g(u,v) of each anchor point, and perform normalization based on the Gaussian curvature of all anchor points to obtain the normalized Gaussian curvature g corresponding to each anchor point k ; According to the normalized Gaussian curvature g k , respectively update the initial position of each uniform point to obtain the final position corresponding to each uniform point; The positions of all anchor points and the final positions of all uniform points are taken as the positions of the target measuring points.

5. The free-form surface geometry adaptive processing method according to claim 4, characterized in that: According to the normalized Gaussian curvature g k , respectively updating the initial position of each uniform point to obtain the final position corresponding to each uniform point, including: Perform one or more rounds of iterations, and use the position corresponding to each uniform point obtained in the last iteration of the last round as the final position, wherein each round of iteration includes at most A iterations, and the hyperparameter β corresponding to each round of iteration is different, and each round of iteration includes the following steps: Set the hyperparameter β corresponding to the current round; According to the hyperparameter β and the normalized Gaussian curvature g k Perform B iterations corresponding to the current round, where 1≤B≤A; Among them, if in the Bth iteration of the current round, the current tolerance is less than the tolerance threshold for the first time, then the current round is taken as the last round, and this iteration is taken as the last iteration; if until the Ath iteration of the current round, the current tolerance is still not less than the tolerance threshold, then the next round of iteration is performed.

6. The free-form surface geometry adaptive processing method according to claim 5, characterized in that: The hyperparameter β and the normalized Gaussian curvature g k Performing B iterations corresponding to the current round includes: Set B to 1 and perform the Bth iteration, where each iteration includes the following steps: According to the hyperparameter β and the normalized Gaussian curvature g corresponding to the current round k Get the current position p corresponding to each uniform point respectively j , where the current position p j Based on the previous position p obtained in the previous iteration of the current round j-1 Calculate the previous position p at the first iteration of the current round j-1 For p 0 ; According to the current position p of all the uniform points j Reconstruct the surface with the positions of all anchor points to obtain the current surface; The current tolerance is calculated according to the current surface and S(u,v), and the relationship between the current tolerance and the tolerance threshold is determined. When the current tolerance is not less than the tolerance threshold and B is less than A, the next iteration of the current round is performed, B is increased by 1, and the current position p of each uniform point is changed to j As the previous position p of the next iteration of the current round j -1 .

7. The free-form surface geometry adaptive processing method according to claim 6, characterized in that: The hyperparameter β corresponding to the current round and the normalized Gaussian curvature g k Get the current position p corresponding to each uniform point respectively j ,include: Take each uniform point as the current uniform point and perform the following operations: Determine the previous position p of the current uniform point j-1 The nearest Z anchor points P z , where Z ≥ 2, z = 1, ... Z; Get p respectively j-1 To the Z anchor points P z The parameter distance d z , the current uniform point points to the Z anchor points P respectively z The parameter vector The Z anchor points P z The corresponding normalized Gaussian curvature g z ; According to the formula Calculate the current position p of the current uniform point j .

8. The free-form surface geometry adaptive processing method according to claim 2, characterized in that: The P-based me and M m Get each P me The corresponding reflection point coordinate data P com ,include: According to any point P on S(u,v) f Determine the main direction parameter u corresponding to this point f and the orthogonal direction parameter v f ; Obtain the corresponding point P on the ideal semi-finishing CAD model s , where P s The main direction parameter and the orthogonal direction parameter are u f and v f ; Using the formula Get the construction vector n of S(u,v); For each P me Perform the following operations respectively: me Along the construction vector n to the mirror M m Extension, obtain the extension direction and the mirror M m The intersection point P m ; Get the P me With P m The distance D m ; Using formula P com =P me -2D m ·nGet the P me The corresponding reflection point coordinate data P com .

9. The free-form surface geometry adaptive processing method according to claim 1, characterized in that: Based on all P com Obtaining an error map and using the error map as a finishing path includes: Based on all P com Surface interpolation reconstruction is performed to obtain the error map, and the error map is used as the finishing path.

10. A free-form surface geometry adaptive processing device, comprising a processor and a memory, characterized in that: The memory is used to store the free-form surface geometry adaptive processing program; The processor is used to read the free-form surface geometry adaptive processing program and perform the free-form surface geometry adaptive processing method as described in any one of claims 1-9.

Images