MBD-based three-dimensional part dimension mark automatic generation method

Abstract

The invention discloses an MBD-based three-dimensional part dimension mark automatic generation method, which comprises the following steps of: firstly, carrying out structural analysis on a topological object of a geometry, extracting all edge domain elements on the geometry, traversing each edge domain element in a set, analyzing a topological structure and a geometric curved surface related to the edge domain element, and finishing screening, filtering and classifying; obtaining a labeling element set of each type; secondly, for different types of labeling elements, qualitative positioning correlation between the labeling elements and the sizes is analyzed, and a corresponding size labeling algorithm is designed; the method comprises the following steps of: firstly, establishing an annotation plane according to a size generation requirement, and repeatedly judging the annotation plane and an existing annotation view set, and finally, quickly generating size information, and carrying out redundancy check and redundant size removal on the generated annotation information to realize the construction of a three-dimensional inspection model. According to the method, part manufacturing and detection information can be directly expressed on the three-dimensional model, the product development efficiency is improved, and the production period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional annotation of three-dimensional part models in a design process, and in particular to an automatic generation method of three-dimensional part dimension annotation based on MBD. Background Art

[0002] In recent years, with the rapid development of my country's aviation manufacturing industry, digitalization and intelligence have become new trends in the future of aviation industry technology updates. Although part design has been three-dimensionalized, the domestic inspection method based on model-based definition (MBD) technology is still relatively backward. The mainstream inspection technology of most aircraft manufacturers still relies on the preparation of inspection plans and the expression of part size and other information through two-dimensional drawings. This traditional inspection method is not only labor-intensive and inefficient, but also prone to deviations in the actual inspection process. Nowadays, the full three-dimensional digital product development model has entered a new stage. Boeing has fully adopted MBD technology in the development of new passenger aircraft represented by Boeing 787, directly using three-dimensional annotation models as the basis for manufacturing, and has achieved great success in the application of digital technology. Therefore, in order to promote the implementation process and technical level of digital design and manufacturing in the domestic manufacturing industry and realize the digital expression of detection information, it is necessary to combine the current aircraft digital manufacturing process and carry out research on three-dimensional digital technology suitable for the development of my country's manufacturing industry. Among them, the establishment of a three-dimensional inspection digital model based on MBD is the prerequisite for the application of digital inspection technology, and the intelligent creation of three-dimensional dimension annotation information is a key link. Although the 3D modeling software CATIA has a 3D annotation function module (Functional Tolerancing & Annotation), its functions have certain limitations, the operation process is cumbersome, and it cannot quickly and completely express the dimension annotation information. Moreover, designers have been working in an environment where they have exported 2D engineering drawings for a long time, and it is difficult for them to switch from 2D habitual thinking to 3D manual annotation. Therefore, in order to shorten the product development cycle and improve the quality of aircraft development, it is necessary to design a 3D dimension annotation automatic generation method. By using some simple human-computer interaction operations, the automatic annotation of 3D dimension information can be realized, 2D engineering drawing can be abandoned, and engineering and technical personnel can be liberated from the heavy 2D drawing work. Through the 3D dimension automatic generation technology, designers can quickly complete the construction of 3D inspection digital models, and use it as the only basis in the manufacturing and testing process, truly realizing paperless 3D digital integrated manufacturing. Moreover, the use of this method can greatly reduce the workload, unify the data expression forms of upstream and downstream design and manufacturing information, and effectively improve the R&D efficiency of designers in the manufacturing industry.

[0003] Traditional inspection methods have the following disadvantages:

[0004] 1. The 3D model needs to be exported to 2D engineering drawings. Deviations or omissions may occur during data conversion, resulting in ambiguity. In addition, the rework rate of 2D drawing design changes is high, resulting in a lot of labor waste.

[0005] 2. Two-dimensional engineering drawing relies entirely on manual annotation, which is arduous and slow to produce, seriously restricting the development efficiency of product parts, and unable to guarantee the integrity and accuracy of the annotation information.

[0006] 3. The traditional process requires continuous projection conversion from 3D to 2D. The expression of 3D structural information is not intuitive and is prone to misunderstanding.

[0007] 4. The built-in 3D annotation module of CATIA software is complex to operate, the annotation efficiency is low, and the operators are not familiar enough with it, which makes it difficult to meet the needs of actual production applications. Summary of the invention

[0008] The purpose of the present invention is to solve the technical problems existing in the prior art and to provide a method for automatically generating three-dimensional part dimensioning based on MBD.

[0009] To achieve the above object, the present invention provides a technical solution: a method for automatically generating 3D part dimensioning based on MBD, characterized in that: the method includes:

[0010] Step 1: Obtain the annotation document in the parts product;

[0011] Step 2: Get the TPS object set list, and retrieve the annotation set in the file in the form of the TPS object list; if successful, use it as the storage location for the subsequent creation of dimension annotation information; if unsuccessful, create a new annotation set;

[0012] Step 3: Build a general path and initialize the TTRS (Technologically and Topologically Related Surface) factory. TTRS is a surface related to technology and topology.

[0013] Step 4: Manage the annotation view. Obtain the annotation view list in the annotation set through the TPS object set interface. If the annotation view set does not exist, create a new annotation view set as the carrier of the annotation information.

[0014] Step 5: Perform a topological object structure analysis on the geometric body of the three-dimensional model, extract all the edge elements contained in the geometric body, and perform judgment and filtering to obtain a unique set of edge annotation elements;

[0015] Step 6: traverse the annotation element set, classify the annotation elements into plane elements and surface elements, obtain the surface type of the annotation elements, and extract the annotation elements that conform to the circular shape surface;

[0016] Step 7: traverse the surface annotation element set, obtain the upper limit point and lower limit point of the geometric surface, and extract its parameter values ​​in the U and V directions, and classify and annotate different surface element types;

[0017] Step 8: For the plane element type, the selection operation of the annotation element is completed through manual interaction, and then its topology and geometric structure are analyzed to complete the automatic annotation of the plane element shape and size;

[0018] Step 9: For the management of annotation views, when creating an annotation view, the normal vector of the annotation view to be created needs to be compared with the normal vectors of the existing annotation view list in the annotation set. If there are parallel or overlapping annotation views, the existing view will be used as the supporting view for dimensioning. If not, a new annotation view will be created to facilitate information management and identification.

[0019] Step 10: Update the 3D digital model of the product parts and display all dimension annotation information in the annotation set in the 3D model and structure tree.

[0020] Preferably, step 1 specifically includes the following steps:

[0021] Step 101, obtaining the current document pointer of the file by obtaining the current document editor object;

[0022] Step 102: Implement an interface through a file containing tolerance information, allow access to the tolerance set in the file, and obtain a pointer to the annotation document.

[0023] Preferably, step 3 specifically includes the following steps:

[0024] Step 301, extract the current pointer activation object, access the structure tree information of the part product file, obtain the part geometry in the product file, set the current activation object, and use it to build a general path;

[0025] Step 302: Screen and extract the annotation elements, and perform object characterization operations on them;

[0026] Step 303: Create a TTRS factory object and initialize the TTRS factory;

[0027] Step 304: construct a global variable set for storing the failed annotation faces, and pre-set a dialog box display list and highlighting operation for the elements in the set.

[0028] Preferably, step 4 specifically includes the following steps:

[0029] Step 401: Obtain the annotation view list in the annotation set through the TPS object set interface. If it does not exist, create a new annotation view set as a carrier of the annotation information.

[0030] Step 402: Create a view factory and construct a annotation plane according to the association relationship between annotation elements and dimensions;

[0031] Step 403: Repeatedly judge the annotation view, compare and judge the normal vector of the newly constructed annotation plane with the normal vectors of the annotation views in the existing annotation view set, so as to reduce the generation of unnecessary views;

[0032] Step 404: Before creating the annotation information, set the annotation view supporting the annotation information to an activated state.

[0033] Preferably, step 5 specifically includes the following steps:

[0034] Step 501, access the geometric structure of the three-dimensional model of the part, extract all the edge topological objects, and save them into the total set of edge elements;

[0035] Step 502: traverse all edge elements in the total set, obtain the surface cell structure units directly connected with them, and analyze their topological structures and geometric surfaces;

[0036] Step 503: By calculating, measuring and comparing the centroid and area of ​​the surface elements, repeated surface cell units are judged and filtered out, and the boundary elements associated with them are deleted to obtain a filtered boundary annotation element set.

[0037] Preferably, step 6 specifically includes the following steps:

[0038] Step 601: traverse the filtered edge element set to obtain the surface cells directly connected to it, and then obtain the geometric surface of the surface through the surface cells;

[0039] Step 602: Check the two direction parameters of the geometric surface and determine whether it is consistent with the circular contour surface. If it is consistent, add it to the surface annotation element set; if it is not consistent, add it to the annotation failure surface set.

[0040] Preferably, step 7 specifically includes the following steps:

[0041] Step 701: Create a global parameter representing a point on the CATSurface according to the parameter values ​​of the two extreme points, and obtain the direction vector of the point in the U and V directions on the surface;

[0042] Step 702: Obtain mathematical points related to the global parameter point, and create two mutually perpendicular annotation planes Plane(U) and Plane(V) according to direction vectors in the U and V directions;

[0043] Step 703: If the geometric surface is a cylindrical surface, obtain the high and low angle limits of the cylindrical surface respectively, calculate the curvature of the cylindrical surface, and extract the corresponding annotation elements;

[0044] Step 704: if the curvature of the cylindrical surface is less than 180°, mark it as a rounded corner, mark the rounded corner radius and mark the plane as Plane (V); otherwise, mark it as a cylindrical surface, mark the cylindrical surface diameter and mark the plane as Plane (U);

[0045] Step 705: If the geometric surface is a conical surface, extract its related elements, mark its bottom diameter and mark the plane as Plane (U);

[0046] Step 706: mark the height limits of the cylindrical surface and the conical surface, obtain the corresponding non-adjacent marking elements, complete the marking of the height of the cylinder or cone, and the marking plane is Plane (U);

[0047] Step 707: If the geometric surface is a spherical surface, i.e., a rounded corner, directly mark its spherical diameter and mark the plane as Plane (U);

[0048] Step 708: If it does not belong to these surface types or the annotation fails, it is stored in the annotation failure surface set and displayed in the dialog box list.

[0049] Preferably, step 8 specifically includes the following steps:

[0050] Step 801, construct a selection agent, create a plane annotation command, and associate it with a dialog box control command;

[0051] Step 802: Get the plane element selected by the selection agent, analyze its topological structure object, and extract all the edges on the surface;

[0052] Step 803: Filter all the edge regions, delete the curve elements and repeated elements contained in the edge region set, and extract the straight edge region element set;

[0053] Step 804: Obtain the mathematical plane of the annotation element and set it as a parameter for constructing the annotation view during the plane annotation process;

[0054] Step 805: perform a parallel judgment loop on the straight line boundary elements, classify and save the mutually parallel straight line elements into different sets, and filter out the individual non-parallel straight line elements, extract the positions of the two end points of the straight line segment, and mark the distance between the two points in the horizontal and vertical directions;

[0055] Step 806: traverse the selected multiple mutually parallel elements in the set, select the farthest straight line element as the reference for a group of parallel straight line annotations, and annotate the distance dimensions between other parallel straight lines and the reference to ensure that the dimensions are not redundant, thereby completing the annotation of the plane shaping dimensions.

[0056] Beneficial effects of the present invention:

[0057] 1. The present invention can analyze the geometric topological structure of the three-dimensional model of the part, extract the relevant annotation elements, and organize, filter and classify them to extract a set of annotation elements that meet the requirements. Finally, according to the program design algorithm, the rapid annotation of the part size information is realized, and some incomplete or irregular surfaces are centrally processed and highlighted.

[0058] 2. The three-dimensional inspection model constructed by the present invention serves as the only basis for inspection work, realizing a true single data source. It can not only ensure the correctness and integrity of the inspection planning information data, but also form an integrated closed-loop control of design-manufacturing-testing in the product development process, reduce the preparation time of part design, cut costs, and improve engineering quality.

[0059] 3. The present invention directly performs three-dimensional annotation on the three-dimensional model, and the detection information is directly expressed on the three-dimensional model. No two-dimensional drawings are output, which can ensure the unification of data sources, reduce unnecessary manpower and a large amount of repetitive labor, and reduce the rework rate of products. The digital transmission of data based on MBD avoids the conversion process of model data and detection data, improves detection efficiency and quality, and shortens the product development cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The drawings described herein are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0061] Figure 1 It is a flow chart for automatically generating dimension annotation of three-dimensional parts based on MBD in the present invention. DETAILED DESCRIPTION

[0062] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0063] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0064] In order to overcome the problems of cumbersome two-dimensional drawing export, slow detection speed, high cost and easy operation error in the process of parts inspection, a method for automatic generation of three-dimensional part dimension annotation based on MBD is proposed. The present invention provides an auxiliary work of three-dimensional annotation for digital inspection technology to meet the current production level of manufacturing industry, improve the efficiency and quality of parts inspection, reduce unnecessary manpower and labor waste, and reduce production cost. The method firstly performs structural analysis on the topological object of the geometric body, extracts all the boundary elements on the geometric body, and traverses each boundary element in the set, analyzes the topological structure and geometric surface related to it, completes screening, filtering and classification, and obtains various types of annotation element sets; secondly, for different types of annotation elements, analyzes the qualitative positioning association between annotation elements and dimensions, and designs corresponding dimension annotation algorithms; then, creates annotation planes according to the requirements of dimension generation, and repeats judgment with the existing annotation view set to reduce the generation of unnecessary views. Finally, the rapid generation of dimension information is completed, and the generated annotation information is checked for redundancy, and redundant dimensions are removed to realize the construction of three-dimensional inspection model.

[0065] The present invention can help designers quickly and efficiently complete the generation of three-dimensional dimension annotation information of parts, directly express part manufacturing and inspection information on the three-dimensional model, abandon the traditional tedious operation of exporting two-dimensional drawings and then manually annotating them, thereby improving product development efficiency and shortening the production cycle.

[0066] Example 1

[0067] Reference Figure 1 , a preferred embodiment of the present invention, a method for automatically generating 3D part dimensioning based on MBD, the method comprising the following steps:

[0068] Step 1: Get the current document pointer of the file by obtaining the current document editor object, and then obtain the annotation document in the part product through the tolerance document interface.

[0069] Step 2: Construct the annotation information carrier. Access the relevant TPS document and retrieve the annotation set in the file in the format of TPS object list. If it does not exist, create a new annotation set as the storage location for the subsequent dimension annotation information.

[0070] Step 3: Build a general path and initialize the TTRS (Technologically and Topologically Related Surface) factory. TTRS is a surface related to technology and topology.

[0071] Specifically, step 301, extract the current pointer activation object, access the structure tree information of the part product file, obtain the part geometry in the product file, set the current activation object, and use it to construct the general path;

[0072] Step 302: Screen and extract the annotation elements, and perform object characterization operations on them;

[0073] Step 303: Create a TTRS factory object and initialize the TTRS factory;

[0074] Step 304: construct a global variable set for storing the failed annotation faces, and pre-set a dialog box display list and highlighting operation for the elements in the set.

[0075] Step 4: Manage annotation views, create annotation view sets, and annotation planes.

[0076] Specifically, step 401 , obtain the annotation view list in the annotation set through the TPS object set interface. If it does not exist, create a new annotation view set as a carrier of the annotation information.

[0077] Step 402: Create a view factory and construct a annotation plane according to the association relationship between annotation elements and dimensions.

[0078] Step 403 : Repeat the annotation view judgment, compare and judge the normal vector of the newly constructed annotation plane with the normal vectors of the annotation views in the existing annotation view set, so as to reduce the generation of unnecessary views.

[0079] Step 404: Before creating the annotation information, set the annotation view supporting the annotation information to an activated state.

[0080] Step 5: Geometric topological object analysis: Extract all the edge elements contained in the geometric body, and perform judgment and filtering to obtain a unique set of edge annotation elements.

[0081] Specifically, step 501 accesses the geometric structure of the three-dimensional model of the part, extracts all edge topological objects, and saves them into the total set of edge elements.

[0082] Step 502: traverse all edge elements in the total set, obtain the surface cell structural units directly connected with them, and analyze their topological structures and geometric surfaces.

[0083] Step 503: By calculating, measuring and comparing the centroid and area of ​​the surface elements, repeated surface cell units are judged and filtered out, and the boundary elements associated with them are deleted to obtain a filtered boundary annotation element set.

[0084] Step 6: Traverse the annotation element set and classify the annotation elements into plane elements and surface elements. According to different element types, formulate corresponding dimensioning methods.

[0085] Step 7: For the surface element type, extract its corresponding geometric surface, obtain its upper and lower limit points, and determine whether its surface type is cylindrical, conical, chamfered, spherical, etc., and then add it to the corresponding annotation set, and complete the annotation of the surface type element according to the relevant annotation algorithm designed by the program

[0086] Step 8: For the plane element type, complete the selection of annotation elements through manual interaction, analyze its topology and geometry, extract the linear boundary annotation element set, and then perform parallel loop judgment on the annotation elements in the set. Finally, for multiple parallel linear elements, select the benchmark and complete the relative position annotation. For individual non-parallel linear elements, directly annotate the horizontal and vertical distance dimensions between their two end points.

[0087] Step 9: Perform a redundancy check on all dimensions in the annotation set, traverse each annotation information, and analyze its TTRS object. If there are duplicate elements, delete the relevant duplicate annotation information.

[0088] Step 10: Update the 3D digital model of the product parts and display all dimension annotation information in the annotation set in the 3D model and structure tree.

[0089] The present invention can analyze the geometric topological structure of the three-dimensional model of the part, extract the relevant annotation elements, and organize, filter and classify them to extract a set of annotation elements that meet the requirements. Finally, according to the program design algorithm, the rapid annotation of the part size information is realized, and some incomplete or irregular surfaces are centrally processed and highlighted.

[0090] The three-dimensional inspection model constructed by the present invention serves as the only basis for inspection work, realizing a true single data source. It can not only ensure the correctness and integrity of the inspection planning information data, but also form an integrated closed-loop control of design-manufacturing-testing in the product development process, reduce the preparation time of part design, cut costs, and improve engineering quality.

[0091] The present invention directly performs three-dimensional annotation on the three-dimensional model, and the detection information is directly expressed on the three-dimensional model. No two-dimensional drawings are output, which can ensure the unification of data sources, reduce unnecessary manpower and a large amount of repetitive labor, and reduce the rework rate of products. The digital transmission of data based on MBD avoids the conversion process of model data and detection data, improves detection efficiency and quality, and shortens the product development cycle.

[0092] In summary, the present invention can help designers quickly and efficiently complete the generation of three-dimensional dimension annotation information of parts, directly express part manufacturing and inspection information on the three-dimensional model, abandon the traditional tedious operation of exporting two-dimensional drawings and then manually annotating them, improve product development efficiency, and shorten the production cycle.

[0093] Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

[0094] The above description is only a preferred implementation mode of the present invention. Any technical solution that achieves the purpose of the present invention by substantially the same means belongs to the protection scope of the present invention.

Claims

1. A method for automatically generating 3D part dimensioning based on MBD, characterized by: The method comprises the following steps: Step 1: Obtain the annotation document in the parts product; Step 2: Get the TPS object set list, and retrieve the annotation set in the file in the form of the TPS object list; if successful, use it as the storage location for the subsequent creation of dimension annotation information; if unsuccessful, create a new annotation set; Step 3: construct a general path and initialize the TTRS factory, where TTRS is a surface related to process and topology; Step 4: Manage the annotation view. Obtain the annotation view list in the annotation set through the TPS object set interface. If the annotation view set does not exist, create a new annotation view set as the carrier of the annotation information. Step 5: Perform a topological object structure analysis on the geometric body of the three-dimensional model, extract all the edge elements contained in the geometric body, and perform judgment and filtering to obtain a unique set of edge annotation elements; Step 6: traverse the annotation element set, classify the annotation elements into plane elements and surface elements, obtain the surface type of the annotation elements, and extract the annotation elements that conform to the circular shape surface; Step 7: traverse the surface annotation element set, obtain the upper limit point and lower limit point of the geometric surface, and extract its parameter values ​​in the U and V directions, and classify and annotate different surface element types; Step 8: For the plane element type, the selection operation of the annotation element is completed through manual interaction, and then its topology and geometric structure are analyzed to complete the automatic annotation of the plane element shape and size; Step 9: For the management of annotation views, when creating an annotation view, the normal vector of the annotation view to be created needs to be compared with the normal vectors of the existing annotation view list in the annotation set. If there are parallel or overlapping annotation views, the existing view will be used as the supporting view for dimensioning. If not, a new annotation view will be created to facilitate information management and identification. Step 10: Update the 3D digital model of the product parts and display all dimension annotation information in the annotation set in the 3D model and structure tree.

2. The method for automatically generating 3D part dimensioning based on MBD according to claim 1, characterized in that: Step 1 specifically includes the following steps: Step 101, obtaining the current document pointer of the file by obtaining the current document editor object; Step 102: Implement an interface through a file containing tolerance information, allow access to the tolerance set in the file, and obtain a pointer to the annotation document.

3. The method for automatically generating 3D part dimensioning based on MBD according to claim 1, characterized in that: Step 3 specifically includes the following steps: Step 301, extract the current pointer activation object, access the structure tree information of the part product file, obtain the part geometry in the product file, set the current activation object, and use it to build a general path; Step 302: Screen and extract the annotation elements, and perform object characterization operations on them; Step 303: Create a TTRS factory object and initialize the TTRS factory; Step 304: construct a global variable set for storing the failed annotation faces, and pre-set a dialog box display list and highlighting operation for the elements in the set.

4. The method for automatically generating 3D part dimensioning based on MBD according to claim 1, characterized in that: Step 4 specifically includes the following steps: Step 401: Obtain the annotation view list in the annotation set through the TPS object set interface. If it does not exist, create a new annotation view set as a carrier of the annotation information. Step 402: Create a view factory and construct a annotation plane according to the association relationship between annotation elements and dimensions; Step 403: Repeatedly judge the annotation view, compare and judge the normal vector of the newly constructed annotation plane with the normal vectors of the annotation views in the existing annotation view set, so as to reduce the generation of unnecessary views; Step 404: Before creating the annotation information, set the annotation view supporting the annotation information to an activated state.

5. The method for automatically generating 3D part dimensioning based on MBD according to claim 1, characterized in that: Step 5 specifically includes the following steps: Step 501, access the geometric structure of the three-dimensional model of the part, extract all the edge topological objects, and save them into the total set of edge elements; Step 502: traverse all edge elements in the total set, obtain the surface cell structure units directly connected with them, and analyze their topological structures and geometric surfaces; Step 503: By calculating, measuring and comparing the centroid and area of ​​the surface elements, repeated surface cell units are judged and filtered out, and the boundary elements associated with them are deleted to obtain a filtered boundary annotation element set.

6. The method for automatically generating 3D part dimensioning based on MBD according to claim 1, characterized in that: Step 6 specifically includes the following steps: Step 601: traverse the filtered edge element set to obtain the surface cells directly connected to it, and then obtain the geometric surface of the surface through the surface cells; Step 602: Check the two direction parameters of the geometric surface and determine whether it is consistent with the circular contour surface. If it is consistent, add it to the surface annotation element set; if it is not consistent, add it to the annotation failure surface set.

7. The method for automatically generating 3D part dimensioning based on MBD according to claim 1, characterized in that: Step 7 specifically includes the following steps: Step 701: Create a global parameter representing a point on the CATSurface according to the parameter values ​​of the two extreme points, and obtain the direction vector of the point in the U and V directions on the surface; Step 702: Obtain mathematical points related to the global parameter point, and create two mutually perpendicular annotation planes Plane(U) and Plane(V) according to direction vectors in the U and V directions; Step 703: If the geometric surface is a cylindrical surface, obtain the high and low angle limits of the cylindrical surface respectively, calculate the curvature of the cylindrical surface, and extract the corresponding annotation elements; Step 704: if the curvature of the cylindrical surface is less than 180°, mark it as a rounded corner, mark the rounded corner radius and mark the plane as Plane (V); otherwise, mark it as a cylindrical surface, mark the cylindrical surface diameter and mark the plane as Plane (U); Step 705: If the geometric surface is a conical surface, extract its related elements, mark its bottom diameter and mark the plane as Plane (U); Step 706: mark the height limits of the cylindrical surface and the conical surface, obtain the corresponding non-adjacent marking elements, complete the marking of the height of the cylinder or cone, and the marking plane is Plane (U); Step 707: If the geometric surface is a spherical surface, i.e., a rounded corner, directly mark its spherical diameter and mark the plane as Plane (U); Step 708: If it does not belong to these surface types or the annotation fails, it is stored in the annotation failure surface set and displayed in the dialog box list.

8. The method for automatically generating 3D part dimensioning based on MBD according to claim 1, characterized in that: Step 8 specifically includes the following steps: Step 801, construct a selection agent, create a plane annotation command, and associate it with a dialog box control command; Step 802: Get the plane element selected by the selection agent, analyze its topological structure object, and extract all the edges on the surface; Step 803: Filter all the edge regions, delete the curve elements and repeated elements contained in the edge region set, and extract the straight edge region element set; Step 804: Obtain the mathematical plane of the annotation element and set it as a parameter for constructing the annotation view during the plane annotation process; Step 805: perform a parallel judgment loop on the straight line boundary elements, classify and save the mutually parallel straight line elements into different sets, and filter out the individual non-parallel straight line elements, extract the positions of the two end points of the straight line segment, and mark the distance between the two points in the horizontal and vertical directions; Step 806: traverse the selected multiple mutually parallel elements in the set, select the farthest straight line element as the reference for a group of parallel straight line annotations, and annotate the distance dimensions between other parallel straight lines and the reference to ensure that the dimensions are not redundant, thereby completing the annotation of the plane shaping dimensions.

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