A free-form surface geometry self-adapting machining method and device

Abstract

A method and apparatus for adaptive machining of freeform surfaces, the method comprising: acquiring a CAD model of a freeform surface workpiece; generating a machining path and measurement information for a blank workpiece based on the CAD model; sending measurement control commands to a coordinate measuring machine (CMM) based on the measurement information; measuring the blank workpiece clamped on a CNC machine tool based on the machining path; and obtaining coordinate data P for each target measurement point. me According to the CAD model and P me The machining accuracy of the blank workpiece is judged. When the machining accuracy is less than a preset threshold, an ideal semi-finished CAD model of the freeform surface workpiece is obtained. A mirror M is constructed between the CAD model and the ideal semi-finished CAD model. m Based on P me and M m Get each P me Corresponding reflection point coordinate data P com Based on all P com Obtaining an error map and using it as a finishing path for finishing workpieces can ensure machining accuracy, improve machining efficiency, and reduce machining costs during the machining process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of machining, in particular to a free-form surface geometry adaptive machining method and device. BACKGROUND

[0002] Free-form surface parts have excellent aerodynamic performance and fluid performance, and are widely used in aerospace, shipbuilding, marine, automobile industry and other fields. The machining precision and quality of free-form surface parts deeply affect the performance of the parts. However, the machining precision of free-form surface parts is often subject to the motion precision of the machine tool itself, so corresponding methods are needed to improve the machining precision of the parts to meet the growing demand.

[0003] At present, adaptive machining methods are mainly used to realize the machining of free-form surface parts. In order to obtain the error distribution of a 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 curved surface part is represented by a polynomial function of the machining model, and the tool path is corrected based on this condition to reduce the machining error. However, for different parts and different machine tools, their machining models may be different. If the machined part or machine tool changes, the machining model needs to be re-established. The machining process wastes raw materials, has low machining efficiency, and is complicated, which is difficult to meet the demand for machining efficiency and cost in actual production. At the same time, in the current adaptive machining process, the detection results of the three-coordinate measuring machine are used for machining error compensation. In the subsequent machining process, the tool radius needs to be modified in the computer aided manufacturing (CAM) software to compensate for the error and regenerate the fine machining tool path. The defect of this method is that the regenerated fine machining tool path can only move outward or inward by a constant value, and cannot give a specific error compensation at a specific position, so the machining precision is low. SUMMARY

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

[0005] In one aspect, the present application provides a free-form surface geometry adaptive machining method, comprising:

[0006] 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, wherein the measurement information includes a plurality of target measurement points of the blank workpiece;

[0007] Based on the measurement information, a measurement control command is sent to the coordinate measuring machine to measure the blank workpiece clamped on the CNC machine tool based on the machining path, and to obtain the coordinate data P of each target measuring point. me ;

[0008] Based on the CAD model and P me The machining accuracy of the blank workpiece is judged. When the machining accuracy is less than a preset threshold, an ideal semi-finished CAD model of the freeform surface workpiece is obtained, and a mirror M is constructed between the CAD model and the ideal semi-finished CAD model. m Based on P me and M m Get each P me Corresponding reflection point coordinate data P com Based on all P com Obtain the error map and use the error map as the finishing path;

[0009] Based on the finishing path, a finishing control command is sent to the tool of the CNC machine tool to finish the blank workpiece and obtain the freeform surface workpiece.

[0010] On the other hand, embodiments of this application also provide a freeform surface geometry adaptive machining apparatus, including a processor and a memory:

[0011] The memory is used to store the freeform surface geometry adaptive machining program;

[0012] The processor is used to read the freeform surface geometry adaptive machining program and perform the freeform surface geometry adaptive machining method as described in the above embodiments.

[0013] Compared with related technologies, the freeform surface geometry adaptive machining method and apparatus of this application embodiment does not require a large number of machining experiments, eliminates the process of establishing a machining model, saves time, avoids waste of raw materials, and reduces machining costs. It uses an error map as the finishing path, and overcuts the undercut positions on the blank workpiece to ensure the correct machining allowance. Undercutting is performed on the overcut positions on the blank workpiece, so that the freeform surface workpiece obtained after finishing is closer to the CAD model of the freeform surface workpiece. The CAD model is the ideal model of the freeform surface workpiece, which ensures the machining accuracy of the freeform surface part and improves machining efficiency.

[0014] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the solutions described in the description and the accompanying drawings. Attached Figure Description

[0015] The accompanying drawings are included to provide a further understanding of the technical scheme of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical scheme of the present application, and do not constitute a limitation on the technical scheme of the present application.

[0016] Figure 1 is a free-form surface geometry adaptive machining method flowchart of the embodiment of the present application;

[0017] Figure 2 is a schematic diagram of acquiring a reflection point through a mirror surface of the embodiment of the present application;

[0018] Figure 3 is a free-form surface geometry adaptive machining method flowchart of the specific example of the present application;

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

[0020] The present application describes a plurality of embodiments, but the description is exemplary rather than limiting, and it is obvious to those skilled in the art that there can be more embodiments and implementation schemes within the scope of the embodiments described in the present application. Although many possible combinations of features 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 can be used in combination with any other feature or element of any other embodiment, or can replace any other feature or element of any other embodiment.

[0021] The present application includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features and elements disclosed in the present application can also be combined with any conventional features or elements to form a unique inventive scheme defined by the claims. Any feature or element of any embodiment can also be combined with features or elements from other inventive schemes to form another unique inventive scheme defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in the present application can be implemented alone or in any appropriate combination. Therefore, the embodiments are not limited other than according to the limitations made according to the appended claims and their equivalent replacements. In addition, various modifications and changes can be made within the scope of protection of the appended claims.

[0022] Furthermore, in describing representative embodiments, the specification can have presented the method and / or process as a particular sequence of steps. However, to the extent that the method or process depends on the performance of certain steps, the method or process is not limited to the order of steps presented nor to performing some specific steps before other specific steps, unless the description clearly indicates otherwise. Other steps can be utilized, and not all of the steps that are utilized can be presented in this specification. For example, it is possible to utilize steps that are not recited in this specification. Thus, the particular sequence of steps presented in this specification is not a limitation on the order in which steps can be carried out. Nor is the particular sequence of steps presented in this specification a limitation on steps that can be carried out in conjunction with carrying out the steps presented in this specification. Further, the claims are not limited to the particular order of steps that are recited in this specification.

[0023] The embodiments of the present application provide a free-form surface geometry adaptive machining method, comprising steps S1000-S4000, as shown in the following figure. Figure 1

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

[0025] S2000: Send a measurement control instruction to a three-coordinate measuring machine based on the measurement information, measure the blank workpiece clamped on the numerical control machine tool based on the machining path, and obtain three-coordinate data P me of each target measurement point.

[0026] S3000: According to the CAD model and P me , judge the machining precision of the blank workpiece, when the machining precision is less than a preset threshold, obtain an ideal semi-finishing CAD model of the free-form surface workpiece, and construct a mirror surface M m between the CAD model and the ideal semi-finishing CAD model, obtain corresponding reflection point coordinate data P me of each P m based on P me and M com , obtain an error map based on all P com , and use the error map as a finishing machining path.

[0027] S4000: Send a finishing machining control instruction to a tool of the numerical control machine tool based on the finishing machining path, and perform finishing machining on the blank workpiece to obtain the free-form surface workpiece.

[0028] ​In the embodiment, the free-form surface workpiece can be a car body, an airplane wing, a propeller, an architectural facade, an optical element, a bearing, a gear, sports equipment, etc. The examples of the free-form surface workpieces are exemplary descriptions and are not intended to limit the present application, and will not be described herein.

[0029] In the 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 a workpiece of each free-form surface, and then the multiple free-form surfaces are combined to obtain a finished combined workpiece.

[0030] In the embodiment, the numerical control machine tool for machining the free-form surface workpiece can be a five-axis machine tool, a laser machining machine tool, an ultrasonic machining machine tool, an electric spark machining machine tool, etc. The examples of the numerical control machine tools are exemplary descriptions and are not intended to limit the present application, and will not be described herein.

[0031] In the embodiment, the fixture of the numerical control 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 on the numerical control machine tool, and then a three-coordinate measuring machine is used to measure the blank workpiece until the final finishing of the blank workpiece is completed. The position of the blank workpiece can be kept unchanged, i.e., the measurement of the blank workpiece is in-situ measurement, and the finishing of the blank workpiece is in-situ finishing. From the measurement to the completion of the finishing, there is no need to disassemble and clamp, which avoids the movement of the blank workpiece, the positioning error caused by the secondary clamping, the deformation error, and the deformation introduced in the transportation process, and saves the time for transportation.

[0032] In the embodiment, the three-coordinate measuring machine can be selected according to the size of the free-form surface workpiece. For example, a gantry 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. From the measurement principle, a contact-type mechanical three-coordinate measuring machine can be used, or a non-contact-type laser three-coordinate measuring machine can be used.

[0033] In the embodiment, the machining of the free-form surface workpiece can be divided into three stages of rough machining, semi-finishing and finishing, wherein the tool for rough machining can be selected as a flat bottom milling cutter, and the tools for semi-finishing and finishing can be selected as ball-end milling cutters; the rough machining is mainly for machining the raw material, and the raw material after the rough machining will present the rudiment of the free-form surface workpiece and have more "steps"; the semi-finishing is a link between the preceding and the following in the whole machining process, can remove the excess amount left after the rough machining, improve the dimensional accuracy and surface quality on the basis of the rough machining result, and obtain a blank workpiece, and 0.2mm machining allowance can be reserved during the semi-finishing; finally, the free-form surface workpiece is obtained through the finishing of the blank workpiece, and the free-form surface workpiece after the finishing is ensured to have the accuracy by under-cutting at the over-cut part of the blank workpiece and over-cutting at the under-cut part of the blank workpiece.

[0034] In the embodiment, the semi-finishing programming can be performed by the CAD software after the rough machining, the semi-finishing path and the ideal semi-finishing CAD model are generated, the ideal semi-finishing CAD model guides the semi-finishing process, the uniform semi-finishing allowance is ensured, and the preparation for the finishing is made.

[0035] The free-form surface geometry self-adaptive machining method of the embodiment does not need to perform a large number of machining tests, avoids the process of establishing a machining model, saves time, avoids the waste of raw materials, and reduces the machining cost; the error map is used as the finishing path, the under-cut position on the blank workpiece is over-cut to ensure the correct machining allowance, and the over-cut position on the blank workpiece is under-cut, so that the free-form surface workpiece obtained after the finishing is closer to the CAD model of the free-form surface workpiece, the CAD model is an ideal model of the free-form surface workpiece, the machining accuracy of the free-form surface part is ensured, and the machining efficiency is improved.

[0036] In an example embodiment, the CAD model can be a surface model S(u, v) located in a parameter space, 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 the embodiment, the main direction of the parameter space can be the direction with the fastest change of the tangent slope of the surface model S(u, v), the orthogonal direction is orthogonal and perpendicular to the main direction, and 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 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 example embodiment, the step of "generating a machining path and measurement information of the blank workpiece based on the CAD model" in step S1000 can include steps S1100-S1300:

[0040] S1100: generating 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 measurement points for S(u, v) based on a preset target measurement point number N;

[0042] S1300: planning a measurement path based on the planned plurality of target measurement points, wherein the measurement path is a movement path of the three-coordinate measuring machine through the plurality of target measurement points in sequence during measurement of the blank workpiece; and wherein the measurement information further includes the measurement path.

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

[0044] In this embodiment, the machining path generated in step S1100 can further include an initial finishing machining path, and if the machining precision is not less than a preset threshold when the machining precision of the blank workpiece is judged in step S3000, the finishing machining of the blank workpiece is still completed according to the initial finishing machining path.

[0045] In this embodiment, when the planning of target measurement points in step S1200 is performed, the uniform distribution principle or the key feature priority principle can be followed, the uniform distribution principle means that the target measurement points are uniformly distributed to avoid over-dense or over-dense in some areas; the key feature priority principle means that more target measurement points are preferentially configured in key positions of the free-form surface workpiece, such as fitting surface positions, positioning hole positions, etc.

[0046] In an example embodiment, step S1200 can include steps S1210-S1250:

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

[0048] S1220: uniformly distribute N target measurement points on the n spatial curves, wherein for each spatial curve, there are t target measurement points; wherein the target measurement points include anchor points and uniform points on the spatial curve, the anchor points include end points and extreme points of the spatial curve, and the uniform points are at positions p 0 , wherein t is an integer greater than 1, and N = m;

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

[0050] S1240: update the initial positions of each uniform point according to the normalized Gaussian curvatures g k , respectively, to obtain the final positions of each uniform point.

[0051] S1250: take the positions of all anchor points and the final positions of all uniform points as the positions of the target measurement 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 ) in the corresponding parameter space. S(u i , v) is discretized into n curves in the main direction, and S(u, v i ) is discretized into n curves in the orthogonal direction. One of the directions can be selected for discretization, and the size of n can be set according to the size of S(u, v).

[0053] In this embodiment, step S1220 is a step of planning the initial positions of the target measurement points. The principle adopted is the uniform distribution principle, and N target measurement points are uniformly distributed on n spatial curves. In subsequent steps, the positions of the anchor points remain at the initial positions, and only the positions of the uniform points are updated in step S1240.

[0054] In this embodiment, the Gaussian curvature g(u, v) in step S1230 represents the local properties of one anchor point on S(u, v) and is only related to the geometry near the anchor point. After normalization of the Gaussian curvatures g(u, v) of all anchor points, the normalized Gaussian curvatures g k of each anchor point are obtained, and the sum of the g k corresponding to all anchor points is 1.

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

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

[0057] S1242: obtaining the current position p k of each of the uniform points according to the hyperparameter β and the normalized Gaussian curvature g

[0058] In the present 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 iteration is performed.

[0059] In the present embodiment, after one or more iterations, the positions of the uniform points are changed, and the greater the hyperparameter β, the more concentrated the target measurement points in the area with a high value of the normalized Gaussian curvature g k , and the more sparse the target measurement points in the area with a low value of the normalized Gaussian curvature g k ; and the smaller the hyperparameter β, the closer the distribution of the target measurement points to the uniform distribution.

[0060] In the present embodiment, if multiple iterations are needed, the hyperparameter β can be changed in a trend from small to large, so as to ensure that the hyperparameter β used in each iteration is different, and the hyperparameter β used in the same iteration is unchanged; if A iterations are performed in the current iteration, and the current tolerance is still not less than the tolerance threshold, it indicates that the value of the hyperparameter β in the current round is unreasonable, and the value of the hyperparameter β is changed for the next iteration.

[0061] In an example embodiment, step S1242 can include setting B as 1, and performing the Bth iteration, wherein each iteration includes steps S12421-S12423:

[0062] S12421: obtaining the current position p k of each of the uniform points according to the hyperparameter β corresponding to the current round and the normalized Gaussian curvature g j , respectively, wherein the current position p j of each of the uniform points is obtained based on the last position p 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 position p of all the uniform points j Reconstruct the surface using the positions of all anchor points to obtain the current surface;

[0064] S12423: Calculate the current tolerance based on the current surface and the surface model S(u,v), and determine the relationship between the current tolerance and the tolerance threshold. If the current tolerance is not less than the tolerance threshold and B is less than A, proceed to the next iteration of the current round, increment B by 1, and set the current position p of each uniform point. j The previous position p, which is the next iteration of the current round. j-1 .

[0065] In one exemplary embodiment, when performing step S12421, each of the uniform points can be taken as the current uniform point, and steps S124211-S124213 can be performed on the current uniform points:

[0066] S124211: Determine the previous position p relative to the current uniform point. j-1 The most recent Z anchor points P z Where Z≥2, z=1,……Z;

[0067] S124212: Obtain 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 parameter vector The Z anchor points P z The corresponding normalized Gaussian curvatures 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, which involves determining 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, and the parameter vector pointing from the current uniform point to P1. The normalized Gaussian curvature g1 of P1; obtain p j-1 The parameter distance d2 to P2, and the parameter vector pointing from the current uniform point 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 obtaining the final positions of all uniform points, steps S1250 and S1300 can be executed sequentially to obtain the measurement path. When executing step S2000, measurement control commands can be generated according to the measurement path and sent to the coordinate measuring machine to measure the blank workpiece clamped on the CNC machine tool, thereby obtaining the coordinate data P of each target measuring point. me .

[0071] In this embodiment, based on all P me The outline of the blank workpiece can be obtained. Then, step S3000 is executed to compare the outline of the blank workpiece with the CAD model of the freeform surface workpiece, that is, to compare the outline of the blank workpiece with the surface model S(u,v). The machining accuracy of the blank workpiece can be obtained. When the machining accuracy is less than a preset threshold, the finishing path needs to be regenerated to replace the initial finishing path. When regenerating the finishing path, a mirror surface M can be constructed based on the ideal semi-finishing CAD model of the freeform surface workpiece and the surface model S(u,v). m Mirror M m It is the surface located between the ideal semi-finished CAD model and the surface model S(u,v), mirror surface M. m Distance to the ideal semi-finished CAD model and mirror surface M m The distances to the surface model S(u, v) are equal, such as Figure 2 As shown.

[0072] In one exemplary embodiment, the "based on P" in step S3000 me and M m Get each P me Corresponding reflection point coordinate data P com "This may include steps S3100-S3400:

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

[0074] S3200: Obtain the corresponding point P on the ideal semi-finished CAD model. s , where P s The principal direction parameter and the orthogonal direction parameter are respectively u f and v f ;

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

[0076] S3400: For each P me Perform the following operations respectively: [The P] me Along the construction vector n towards the mirror M m Extend, obtain the extension direction and the mirror M m intersection point P m ; Obtain the P me With P m Distance D m Using formula P com =P me -2D m ·n obtains 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, P is determined in the parameter space of the surface model S(u, v). f The principal direction parameter u f and orthogonal direction parameter v f When executing step S3200, based on u obtained in S3100 f and v f Obtain the corresponding point P on the ideal semi-finished CAD model. s That is, P f and P f The principal 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 mirror M m The reflection point P com That is, P me and P com Based on mirror M m The symmetrical point, such as Figure 2 As shown.

[0079] In one exemplary embodiment, step S3000, "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 comThe surface interpolation reconstruction is performed to obtain the error atlas, and the error atlas is used as the finishing path.

[0081] In this embodiment, all reflection point coordinate data P com corresponding to the surface model S(u, v) can be used to perform the surface interpolation reconstruction to generate the error atlas, and the error atlas can be used to replace the initial finishing path. The error atlas is shown in FIG. 4. Figure 2

[0082] To illustrate the free-form surface geometry adaptive machining method of the embodiments of the present application, a specific example is used to describe in detail below, including steps S1-S10, as shown in FIG. 3. Figure 3

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

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

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

[0086] S4: Clamping the rough workpiece on the numerical control machine tool, measuring the rough workpiece according to the target measurement points and the measurement path to obtain the three-coordinate data P me of each target measurement point, and obtaining the profile of the rough workpiece according to the three-coordinate data P me ;

[0087] S5: Comparing the profile of the rough workpiece with the surface model S(u, v) to determine the relationship between the machining precision and the preset threshold value, when the machining precision is less than the preset threshold value, executing step S6; when the machining precision is not less than the preset threshold value, executing step S10;

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

[0089] S7: Determining the construction vector n of the surface model S(u, v), extending each P me along the construction vector n to the mirror surface M m , obtaining the intersection point P m of the extension direction and the mirror surface M m , obtaining the distance D me between the P m and P m ; using the formula P com =P​​me 2D m • n obtain the P me corresponding said reflection point coordinate data P com ;

[0090] S8: based on all reflection point coordinate data P com carrying out surface interpolation, obtaining an error map, and taking the error map as a finishing path;

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

[0092] S10: finishing the blank workpiece based on the initial finishing path.

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

[0094] The embodiments of the present application also provide a free-form surface geometry adaptive machining device, as shown in the accompanying drawings, which comprises a processor and a memory, Figure 4

[0095] The memory is used to save a free-form surface geometry adaptive machining program;

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

[0097] ​Those of ordinary skill in the art will realize and understand that all or some of the steps in the methods disclosed above and the functional modules / units in the systems and devices can be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementation, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component can have multiple functions, or one function or step can be performed by several physical components in cooperation. Some or all of the components can be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on computer-readable media, which can include computer storage media (or non-transitory media) and communication media (or transitory media). As is well known to those of ordinary skill in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is 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 which can be used to store the desired information and which can be accessed by a computer. Furthermore, it is common and well understood by those of ordinary skill in the art that communication media typically embodies 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 can include any information delivery media.

Claims

1. A method for free-form surface geometry adaptive machining, characterized in that, The method comprises: obtaining a CAD model of a free-form surface workpiece, generating a machining path and measurement information of a rough workpiece based on the CAD model, wherein the measurement information comprises a plurality of target measurement points of the rough workpiece; sending measurement control instructions to the coordinate measuring machine based on the measurement information, measuring the rough workpiece clamped on the numerical control machine tool based on the machining path to obtain three-coordinate data P of each target measurement point me ; Based on the CAD model and P me The machining accuracy of the blank workpiece is judged. When the machining accuracy is less than a preset threshold, an ideal semi-finished CAD model of the freeform surface workpiece is obtained, and a mirror M is constructed between the CAD model and the ideal semi-finished CAD model. m Based on P me and M m Get each P me Corresponding reflection point coordinate data P com Based on all P com Obtain the error map and use the error map as the finishing path; sending a fine machining control instruction to a tool of the numerical control machine tool based on the fine machining path, and performing fine machining on the rough workpiece to obtain the free-form surface workpiece.

2. The free-form surface geometry adaptive machining method of claim 1, wherein: the CAD model is a surface model S(u, v) in a parameter space, the parameter space comprising a main direction and an orthogonal direction orthogonal to the main direction, u representing a main direction parameter of S(u, v) in the parameter space, and v representing an orthogonal direction parameter of S(u, v) in the parameter space.

3. The free-form surface geometry self-adaptive machining method according to claim 2, wherein, The method comprises: generating the machining path of the corresponding rough workpiece based on S(u, v), including a rough machining path and a semi-fine machining path; planning target measurement points for S(u, v) based on a preset target measurement point number N; planning a measurement path based on the planned plurality of target measurement points, wherein the measurement path is a movement path of the three-coordinate measuring machine through the plurality of target measurement points in sequence during measurement of the rough workpiece; and wherein the measurement information further comprises the measurement path.

4. The method of claim 3, wherein the freeform surface geometry adaptive machining method further comprises: The method comprises: Discretize S(u,v) into n curves S(u) in the parameter space. i ,v) or S(u,v) i ), where i = 1, 2, ..., n, and n is an integer greater than 1; N target measuring points are evenly distributed in the n spatial curves, wherein, for each spatial curve, there are t target measuring points; wherein the target measuring points include anchor points and uniform points on the spatial curve, the anchor points include end points and extreme points of the spatial curve, and the uniform points are located at positions p of the spatial curve 0 wherein t is an integer greater than 1, and N = tn. obtain a Gaussian curvature g(u, v) of each of the anchor points, and perform normalization processing based on the Gaussian curvatures of all the anchor points to obtain a normalized Gaussian curvature g corresponding to each of the anchor points k ; According to the normalized Gaussian curvature g k The initial position of each uniform point is updated respectively to obtain the final position corresponding to each uniform point. using the positions of all anchor points and the final positions of all uniform points as the positions of the target measurement points.

5. The freeform surface geometry self-adaptive machining method of claim 4, wherein, said according to the normalized Gaussian curvature g k updating the initial position of each of the uniform points respectively to obtain the final position corresponding to each of the uniform points, comprising: performing one or more iterations, and using the position of each uniform point obtained in the last iteration in the last round as the final position, wherein each iteration includes at most A iterations, the hyperparameters β corresponding to each iteration are different, and each iteration comprises the following steps: setting the hyperparameter β corresponding to the current round; According to the hyperparameter β and the normalized Gaussian curvature g k B iterations corresponding to the current round are performed, where 1≤B≤A; wherein if the current tolerance is less than a 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; and if the current tolerance is not less than the tolerance threshold until the Ath iteration of the current round, the next iteration is performed.

6. The freeform surface geometry self-adaptive machining method of claim 5, wherein, the normalized Gaussian curvature g k performing B iterations corresponding to the current round, comprising: setting B to 1 and performing the Bth iteration, wherein each iteration comprises the following steps: According to the hyperparameter β corresponding to the current round and the normalized Gaussian curvature g k Respectively, the current position p corresponding to each of the uniform points is obtained j , wherein the current position p j Based on the last position p obtained by the last iteration of the current round j-1 Calculate the last 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 Carry out surface reconstruction according to the position of all the anchor points, and obtain a current surface; calculating the current tolerance according to the current surface and S(u, v), and judging 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, performing the next iteration of the current round, B is increased by 1, and the current position p of each uniform point is updated as j the last position p as the next iteration of the current round j -1 .

7. The free-form surface geometry self-adaptive machining method according to claim 6, wherein, According to the current wheel corresponding to the super parameter β and the normalized Gaussian curvature g k Respectively, the current position p of each uniform point is obtained j , comprising: taking each uniform point as a current uniform point and performing the following operations: determining a previous position p of the current uniform point j-1 the Z most recent anchor points P z wherein Z≥2, z=1, …, Z respectively obtain p j-1 the parameter distance d z of the Z anchor points P z , the parameter vector z of the current uniform point respectively pointing to the Z anchor points P the Z anchor points P z corresponding normalized Gaussian curvature g z ; According to the formula The current position p of the current uniform point is calculated when the current position p j .

8. The method of claim 2, wherein the freeform surface geometry adaptive machining method further comprises: The P me and M m acquire each P me corresponding to the reflection point coordinate data P com , including: According to any point P on S(u, v) f Determining the main direction parameter u corresponding to the point f And the orthogonal direction parameter v f ; acquiring a corresponding point P on the ideal semi-finish CAD model s wherein the principal direction parameter and the orthogonal direction parameter of P s are u f and v f respectively; Using the formula Obtain the construction vector n of S(u, v); For each P me , the following operations are performed respectively: obtaining the mirror surface M me along the construction vector n towards the mirror surface M m , obtaining the intersection point P m of the extension direction and the mirror surface M m , obtaining the distance D me between P m and P m , and obtaining the corresponding reflected point coordinate data P com of P me using the formula P m =P me -2D com ·n.

9. The method of claim 1, wherein the freeform surface geometry adaptive machining method further comprises: The all P com Obtaining an error map and using the error map as a finishing path includes: based on all P com a curved 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 machining device comprising a processor and a memory, wherein: the memory is configured to store a free-form surface geometry adaptive machining program; the processor is configured to read the free-form surface geometry adaptive machining program and perform the free-form surface geometry adaptive machining method of any one of claims 1-9.

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