Automatic Intersection Feature Identification Method and System Based on Manufacturability Analysis

Abstract

This invention provides an automatic identification method and system for intersection features based on manufacturability analysis, comprising: Step 1: Based on the swing range of the five-axis machine tool axis and the tilt angle range of different machining methods, and according to the definition of manufacturability and the classification of machining surface types, the machining method of each surface is obtained, and the end face is identified by combining the tool reachability geometry algorithm; Step 2: Using the end face as the reference surface, a segmentation surface is constructed by extending the reference surface; Step 3: The difference between the preprocessor and postprocessor is calculated to obtain the machining domain of the process, and the machining area is obtained by finding the intersection of the segmentation surface and the machining domain; Step 4: A domain unit tree is constructed through the dependency relationship between domain units, and domain units with the same dependency surface are merged to construct intersecting domains, thus completing the identification of intersection features. This invention effectively solves the problem that volume decomposition algorithms are not applicable to complex surface features.

Description

Technical Field

[0001] This invention relates to the field of processing feature recognition technology, and more specifically, to an automatic recognition method and system for intersecting features based on processability analysis. Background Technology

[0002] Machining feature recognition is a key technology for intelligent CAM / CAPP, and it forms the foundation for many technologies such as CNC automatic programming, model comparison, and process reuse. In automatic programming systems, feature recognition maps the product's geometric model to machining features, providing support for process planning and machining area identification. Since the 1970s, researchers have developed various methods, including rule-based, graph-based, trace-based, volume decomposition-based, and neural network-based methods, leading to significant advancements in feature recognition technology. Among these, volume decomposition, based on the segmentation of a 3D model and Boolean operations, obtains the actual cutting body through Boolean subtraction between the part and the blank. Then, through segmentation and combination operations, the cutting body is decomposed into process cutting bodies. The resulting process cutting bodies are then mapped to machining features, completing the machining feature recognition process.

[0003] Patent document CN110837694A (application number: CN201911013154.3) discloses a method and apparatus for identifying rotary machining features. The method includes: determining whether a target part is a rotary part; if the target part is a rotary part, identifying all rotary surfaces of the target part; and identifying rotary machining features based on each rotary surface of the target part.

[0004] However, most existing 3D model feature recognition methods based on volume decomposition are designed for three-axis machining features. The cutting surfaces are also pre-defined as planes on the part, and the segmentation rules are not related to the machinability of the part. As a result, many meaningless plane segments are generated, the algorithm has a large computational load, and existing research only focuses on three-axis cutting bodies. This means that the developed algorithms can only recognize three-axis machined parts with regular geometric structures and low complexity. The recognition of complex features, especially intersecting features and curved surface features, remains a challenge that this technology has not yet fully solved. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the purpose of this invention is to provide an automatic identification method and system for intersecting features based on processability analysis.

[0006] The automatic identification method for intersection features based on manufacturability analysis provided by the present invention includes:

[0007] Step 1: Based on the swing range of the five-axis machine tool's tool axis and the tilt range of different machining methods, and according to the definition of machinability and the classification of machining surface types, obtain the machining method for each surface. Based on the surface machining method and the tool reachability geometric algorithm, comprehensively judge and identify the end face.

[0008] Step 2: Select the end face as the reference plane, and construct the segmentation surface by extending the reference plane;

[0009] Step 3: Calculate the difference between the predecessor and successor of the process to obtain the volume region to be processed; use the intersection and segmentation of the segmentation surface with the volume region to be processed to obtain the processing area. The intersection operation obtains the two-dimensional region range bounded by inner and outer rings, and the segmentation operation obtains the volume unit to be processed.

[0010] Step 4: Construct a volume domain unit tree based on the dependencies between volume domain units, merge volume domain units with the same dependency surface, construct intersecting volume domains, and complete the identification of intersecting features.

[0011] Preferably, step 1 includes:

[0012] The set of selectable tool axis directions is defined as follows: Within the machine tool's motion limits, the selectable tool axis direction v t The set of all selectable directions for the machine tool's tool axis, achieved by controlling its movement, is called the tool axis selectable direction set, denoted by V. t express;

[0013] Tool reachability is defined as follows: Let P f V is a point on surface f of the part after the process. t For the set of possible tool axis directions, if v exists t ∈V t And ray L(P) f ,v t If a point does not intersect with the subsequent workpiece in the process, then it is called point P. f With tool reachability, v t For P f The tool axis can be selected in a direction; if for any v t ∈V t , ray L(P f ,v t If all points P intersect with the subsequent workpieces in the same process, then point P is called point P. f P lacks tool reachability f There is no selectable tool axis direction;

[0014] The surface finishing methods for parts are divided into bottom edge machining, side edge machining, and corner rounding.

[0015] The cutter axis tilt angle is defined as follows: Let P f Let v be any point on surface f in the model. t The tool axis can be selected in any direction, and n is the direction of the face f in P.f External normal vector at point v t The angle between v and n is θ, and θ is called v. t At point P f The angle of the cutter shaft at the location;

[0016] The reasonable range of tool axis tilt angle is defined as follows: Under a certain machining method mt, the tool axis tilt angle θ can only be within a certain specific range Θ. mt The range of values ​​within this range is called the reasonable tool axis tilt angle range; if the tool axis can be selected in direction v t At point P f If the tool axis tilt angle falls within the reasonable tool axis tilt angle range, then it is called v t Let P be the point f Under this machining method (mt), the appropriate tool axis direction can be selected.

[0017] The end face is defined as follows: Under a certain machining method mt, when the tool axis inclination angle θ and tool axis vector are reasonably selected, the surface of the workpiece after the process is machined by the bottom cutting edge is called the end face;

[0018] The end face recognition process includes: inputting a given sequence of selectable processing methods mt1, mt2, ..., mt n And the surface f of the workpiece after the process; analyze the machinability of the surface of the workpiece under different processing methods according to the sequence of optional processing methods; determine whether the surface of the workpiece after the process is within a certain processing method mt. i If the next processing method (mt) is available, exit the loop; otherwise, analyze its next processing method (mt). i+1 Machinability under the following conditions; if the surface of the workpiece after the process is not machinable under all selectable machining methods, it is determined to be an unmachinable surface;

[0019] The process of determining the machinability of the workpiece surface after the process is as follows: Input the selectable tool axis direction set V t Processing method MT i Reasonable tool axis tilt angle range Θ mt After the process, the surface f of the workpiece is sampled; sampling point P is obtained on surface f. s Calculate P s External normal vector n; calculate set {v} t |v t ∈V t and <v t ,n>∈Θ mt}; Search and model do not interfere with each other. t If found, then click P. s It can be processed under processing mode MT; otherwise, point P. s It is not machinable, and the surface f is also not machinable; if all sampling points P s If both can be processed, then the determination of surface f in processing method mt is... i The following can be processed; otherwise, the surface f is processed in the mt mode.i It cannot be processed.

[0020] Preferably, step 2 includes:

[0021] Step 2.1: Obtain the geometric data of the reference plane according to the CAD system interface, including the plane type, plane normal, plane axis and plane boundary;

[0022] Step 2.2: Perform the extension operation of the reference surface according to the surface type. If the layered reference surface is part of a plane or quadratic surface, the extended layer is a complete plane or quadratic surface; if the layered reference surface is a freeform surface, construct the segmented surface according to the freeform surface extension rules.

[0023] Preferably, step 3 includes:

[0024] The intersection operator between the dividing surface and the volume domain to be processed is defined as follows: Let the dividing surface be l and the volume domain to be processed be m. Let l and m intersect, and let F be the set of intersecting surface domains of l and m. s , denoted as F s =Intersect(l,m), which is called the intersection operator;

[0025] The domain decomposition operator is defined as follows: Let F be the set of intersecting domains. s It consists of multiple unconnected surface regions, denoted as f. d1 f d2 , ..., f dn F s These regions are obtained after decomposition, denoted as (f d1 f d2 , ..., f dn = Disassemble(F) s ), where Disassemble(F s ) is the region decomposition operator;

[0026] The contour operator for a region is defined as follows: Let F be the set of intersecting regions. s Its contour ring set is denoted as C b For the set of intersecting surface regions F s After finding the contour, we get C. b , denoted as C b =Boundary(F s ), where Boundary(F s ) represents the region contour operator;

[0027] The process of solving the two-dimensional machining region using the intersection method is as follows: Input the dividing surface l and the volume region to be processed m; use l to find the intersection to obtain the set of intersecting surface regions F. s =Intersect(l,m); This function iterates through the set of intersecting surfaces F.s Determine if the intersection is valid, retain valid faces and delete invalid faces; find the intersection profile C. b =Boundary(F s ); using the intersecting profile C b For the set of intersecting surfaces F of the predecessor s Perform negative toroidal clipping, and denote the clipping result as F. l =Trim(F s C b ); For F l Perform region decomposition and exclude invalid regions; the result is denoted as (f1, f2, ..., f n = Disassemble(F) s ), and output;

[0028] The process of solving volumetric domain elements by the segmentation method is as follows: the segmentation surface is used as the segmentation element, the volumetric domain to be processed in the process is used as the segmentation object, the segmentation operation is performed using the CAD system interface, the segmentation result is obtained, and the segmentation result is split into individual volumetric domain elements and stored separately.

[0029] Preferably, step 4 includes:

[0030] For each volumetric unit, determine the volumetric units that the volumetric unit depends on or is depended on according to the vertical dependency relationship, and construct a tree structure. The construction process is as follows: Input volumetric units v1, v2, ..., v n Extract the set consisting of the lower interfaces of all volumetric units as S. d Process volumetric units v one by one i The bottom interface D di Accessing volumetric units v one by one i If v i For elements without a parent, set their parent element as the root node T; output the volume domain unit tree.

[0031] Body domain unit v i The bottom interface D di The processing procedure is as follows: Find the workpieces preceding and following the process that contain D. di The set of faces is F di ; Calculate H di =D di -F di ; For H di Each constituting region, from the center of the region along H di Create a ray h from the external normal vector at the center of the region. j ; use h j and S d -D di Find the intersection point, and denote the closest intersection point as P. k ; by P k Define the volumetric unit vk , where v k For v i Subfield elements, i = 1, 2, ..., n;

[0032] By analyzing the geometric relationship between the inner and outer ring contours, the relationship between dependency lines and dependency surfaces is determined, and volumetric units with the same dependency relationship are merged.

[0033] Dependency lines are defined as follows: if the intersection line l i It is the dividing surface l and a certain line l on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Depends on line l m ;

[0034] The dependency surface is defined as follows: if the intersection line l i It is the dividing surface l and a certain surface f on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Directly dependent on surface f m For the intersection line l i Depends on line l m In this case, it is called line l m The two sides are the intersection line l i The indirect dependency surfaces, and the direct dependency surfaces and indirect dependency surfaces are collectively referred to as the intersection dependency surfaces;

[0035] By traversing the tree model, the vertical positional relationship between volume domain units is determined. Combined with the dependency relationship of volume domain units, specific intersecting volumes are constructed to complete the identification of intersection features.

[0036] Let v be a volumetric element, and let C be the outer ring of its lower interface contour. v Based on the volumetric unit contours and longitudinal dependencies of the processing features, the type of processing feature of the volumetric unit can be determined.

[0037] If If edge e is an edge formed by the inner loop of the subsequent workpiece, and the volume unit v does not have any dependency or being depended on other volume units, then the volume unit v represents a simple feature.

[0038] If If edge e is an edge formed by the inner ring of the workpiece after the process, and there are other volume units that depend on volume unit v, then volume unit v represents the upper layer feature of the stepped intersection feature.

[0039] If If edge e is an edge formed by the inner ring of the workpiece after the process, and the volume unit v depends on other volume units, then the volume unit v represents the lower layer feature of the stepped intersecting feature.

[0040] If If edge r is formed by the outer ring of the preceding workpiece, then the volume unit v represents the parallel intersecting features.

[0041] The automatic intersection feature recognition system based on manufacturability analysis provided by the present invention includes:

[0042] Module M1: Based on the swing range of the five-axis machine tool's tool axis and the tilt range of different machining methods, and according to the definition of machinability and the classification of machining surface types, the machining method of each surface is obtained. Based on the surface machining method and the tool reachability geometric algorithm, the end face is comprehensively judged and identified.

[0043] Module M2: Selects the end face as the reference plane and constructs the segmentation surface by extending the reference plane;

[0044] Module M3: The difference between the predecessor and successor of the process is calculated to obtain the volume region to be processed in the process; the processing area is obtained by intersecting and dividing the volume region with the dividing surface. The intersection operation obtains the two-dimensional region range bounded by inner and outer rings, and the division operation obtains the volume unit to be processed.

[0045] Module M4: Constructs a volume domain unit tree based on the dependencies between volume domain units, merges volume domain units with the same dependency surface, constructs intersecting volume domains, and completes the identification of intersecting features.

[0046] Preferably, the module M1 includes:

[0047] The set of selectable tool axis directions is defined as follows: Within the machine tool's motion limits, the selectable tool axis direction v t The set of all selectable directions for the machine tool's tool axis, achieved by controlling its movement, is called the tool axis selectable direction set, denoted by V. t express;

[0048] Tool reachability is defined as follows: Let P f V is a point on surface f of the part after the process. t For the set of possible tool axis directions, if v exists t ∈V t And ray L(P) f ,v t If a point does not intersect with the subsequent workpiece in the process, then it is called point P. f With tool reachability, v t For P f The tool axis can be selected in a direction; if for any v t ∈V t , ray L(P f ,v t If all points P intersect with the subsequent workpieces in the same process, then point P is called point P. f P lacks tool reachability f There is no selectable tool axis direction;

[0049] The surface finishing methods for parts are divided into bottom edge machining, side edge machining, and corner rounding.

[0050] The cutter axis tilt angle is defined as follows: Let P f Let v be any point on surface f in the model. t The tool axis can be selected in any direction, and n is the direction of the face f in P. f External normal vector at point v t The angle between v and n is θ, and θ is called v. t At point P f The angle of the cutter shaft at the location;

[0051] The reasonable range of tool axis tilt angle is defined as follows: Under a certain machining method mt, the tool axis tilt angle θ can only be within a certain specific range Θ. mt The range of values ​​within this range is called the reasonable tool axis tilt angle range; if the tool axis can be selected in direction v t At point P f If the tool axis tilt angle falls within the reasonable tool axis tilt angle range, then it is called v t Let P be the point f Under this machining method (mt), the appropriate tool axis direction can be selected.

[0052] The end face is defined as follows: Under a certain machining method mt, when the tool axis inclination angle θ and tool axis vector are reasonably selected, the surface of the workpiece after the process is machined by the bottom cutting edge is called the end face;

[0053] The end face recognition process includes: inputting a given sequence of selectable processing methods mt1, mt2, ..., mt n And the surface f of the workpiece after the process; analyze the machinability of the surface of the workpiece under different processing methods according to the sequence of optional processing methods; determine whether the surface of the workpiece after the process is within a certain processing method mt. i If the next processing method (mt) is available, exit the loop; otherwise, analyze its next processing method (mt). i+1 Machinability under the following conditions; if the surface of the workpiece after the process is not machinable under all selectable machining methods, it is determined to be an unmachinable surface;

[0054] The process of determining the machinability of the workpiece surface after the process is as follows: Input the selectable tool axis direction set V t Processing method MT i Reasonable tool axis tilt angle range Θ mt After the process, the surface f of the workpiece is sampled; sampling point P is obtained on surface f. s Calculate P s External normal vector n; calculate set {v} t |v t ∈V t and <v t ,n>∈Θ mt}; Search and model do not interfere with each other. t If found, then click P.s It can be processed under processing mode MT; otherwise, point P. s It is not machinable, and the surface f is also not machinable; if all sampling points P s If both can be processed, then the determination of surface f in processing method mt is... i The following can be processed; otherwise, the surface f is processed in the mt mode. i It cannot be processed.

[0055] Preferably, the module M2 includes:

[0056] Module M2.1: Obtains geometric data of the reference plane based on the CAD system interface, including plane type, plane normal, plane axis and plane boundary;

[0057] Module M2.2: Performs the extension operation of the reference surface according to the surface type. If the layered reference surface is part of a plane or quadratic surface, the extended layer is a complete plane or quadratic surface; if the layered reference surface is a freeform surface, the segmented surface is constructed according to the freeform surface extension rules.

[0058] Preferably, the module M3 includes:

[0059] The intersection operator between the dividing surface and the volume domain to be processed is defined as follows: Let the dividing surface be l and the volume domain to be processed be m. Let l and m intersect, and let F be the set of intersecting surface domains of l and m. s , denoted as F s =Intersect(l,m), which is called the intersection operator;

[0060] The domain decomposition operator is defined as follows: Let F be the set of intersecting domains. s It consists of multiple unconnected surface regions, denoted as f. d1 f d2 , ..., f dn F s These regions are obtained after decomposition, denoted as (f d1 f d2 , ..., f dn = Disassemble(F) s ), where Disassemble(F s ) is the region decomposition operator;

[0061] The contour operator for a region is defined as follows: Let F be the set of intersecting regions. s Its contour ring set is denoted as C b For the set of intersecting surface regions F s After finding the contour, we get C. b , denoted as C b =Boundary(F s ), where Boundary(Fs ) represents the region contour operator;

[0062] The process of solving the two-dimensional machining region using the intersection method is as follows: Input the dividing surface l and the volume region to be processed m; use l to find the intersection to obtain the set of intersecting surface regions F. s =Intersect(l,m); This function iterates through the set of intersecting surfaces F. s Determine if the intersection is valid, retain valid faces and delete invalid faces; find the intersection profile C. b =Boundary(F s ); using the intersecting profile C b For the set of intersecting surfaces F of the predecessor s Perform negative toroidal clipping, and denote the clipping result as F. l =Trim(F s C b ); For F l Perform region decomposition and exclude invalid regions; the result is denoted as (f1, f2, ..., f n = Disassemble(F) s ), and output;

[0063] The process of solving volumetric domain elements by the segmentation method is as follows: the segmentation surface is used as the segmentation element, the volumetric domain to be processed in the process is used as the segmentation object, the segmentation operation is performed using the CAD system interface, the segmentation result is obtained, and the segmentation result is split into individual volumetric domain elements and stored separately.

[0064] Preferably, the module M4 includes:

[0065] For each volumetric unit, determine the volumetric units that the volumetric unit depends on or is depended on according to the vertical dependency relationship, and construct a tree structure. The construction process is as follows: Input volumetric units v1, v2, ..., v n Extract the set consisting of the lower interfaces of all volumetric units as S. d Process volumetric units v one by one i The bottom interface D di Accessing volumetric units v one by one i If v i For elements without a parent, set their parent element as the root node T; output the volume domain unit tree.

[0066] Body domain unit v i The bottom interface D di The processing procedure is as follows: Find the workpieces preceding and following the process that contain D. di The set of faces is F di ; Calculate H di =D di -F di ; For H di Each constituting region, from the center of the region along Hdi Create a ray h from the external normal vector at the center of the region. j ; use h j and S d -D di Find the intersection point, and denote the closest intersection point as P. k ; by P k Define the volumetric unit v k , where v k For v i Subfield elements, i = 1, 2, ..., n;

[0067] By analyzing the geometric relationship between the inner and outer ring contours, the relationship between dependency lines and dependency surfaces is determined, and volumetric units with the same dependency relationship are merged.

[0068] Dependency lines are defined as follows: if the intersection line l i It is the dividing surface l and a certain line l on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Depends on line l m ;

[0069] The dependency surface is defined as follows: if the intersection line l i It is the dividing surface l and a certain surface f on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Directly dependent on surface f m For the intersection line l i Depends on line l m In this case, it is called line l m The two sides are the intersection line l i The indirect dependency surfaces, and the direct dependency surfaces and indirect dependency surfaces are collectively referred to as the intersection dependency surfaces;

[0070] By traversing the tree model, the vertical positional relationship between volume domain units is determined. Combined with the dependency relationship of volume domain units, specific intersecting volumes are constructed to complete the identification of intersection features.

[0071] Let v be a volumetric element, and let C be the outer ring of its lower interface contour. v Based on the volumetric unit contours and longitudinal dependencies of the processing features, the type of processing feature of the volumetric unit can be determined.

[0072] If If edge e is an edge formed by the inner loop of the subsequent workpiece, and the volume unit v does not have any dependency or being depended on other volume units, then the volume unit v represents a simple feature.

[0073] If If edge e is an edge formed by the inner ring of the workpiece after the process, and there are other volume units that depend on volume unit v, then volume unit v represents the upper layer feature of the stepped intersection feature.

[0074] If If edge e is an edge formed by the inner ring of the workpiece after the process, and the volume unit v depends on other volume units, then the volume unit v represents the lower layer feature of the stepped intersecting feature.

[0075] If If edge r is formed by the outer ring of the preceding workpiece, then the volume unit v represents the parallel intersecting features.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] (1) The present invention judges the machinability of the surface of the workpiece after the process based on the processing capability of the machine tool equipment, and quickly determines the end face of the workpiece accordingly. This avoids the problem of meaningless division caused by the traditional volume decomposition and segmentation surface that does not consider machinability, simplifies the operation process and improves efficiency.

[0078] (2) This invention extends the segmentation surface used in volume decomposition from a plane to a curved surface, effectively solving the problem that volume decomposition algorithms are not applicable to complex curved surface features;

[0079] (3) In view of the characteristics of large integral complex structural parts in aerospace, the present invention improves the intersecting feature recognition technology composed of slots, bosses, hole systems, etc., effectively solves the problem of automatic recognition of stepped and parallel intersecting features, and also accommodates simple non-intersecting features.

[0080] (4) The automatic identification method and algorithm of intersecting features based on manufacturability proposed in this invention can obtain high-quality intersecting feature extraction results within an acceptable time range, simplify the manual interaction process of CNC machining CAM programming, and provide support for intelligent process design systems of three-dimensional models. Attached Figure Description

[0081] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0082] Figure 1 This is the overall flowchart;

[0083] Figure 2 This is a schematic diagram illustrating the reachability of the cutting tool.

[0084] Figure 3a Schematic diagram of the tool axis tilt angle for bottom cutting edge machining;

[0085] Figure 3b Schematic diagram of the tool axis tilt angle for side-cutting machining;

[0086] Figure 3c Schematic diagram of the tool axis tilt angle for fillet machining;

[0087] Figure 4aA schematic diagram for solving the domain to be processed using the difference method;

[0088] Figure 4b To obtain the two-dimensional processing area;

[0089] Figure 5 This is a schematic diagram illustrating the determination of dependencies between volume units;

[0090] Figure 6a This is a schematic diagram of the intersection line dependence line;

[0091] Figure 6b This is a schematic diagram of the intersection of the surface lines;

[0092] Figure 7a This is a schematic diagram of a simple feature;

[0093] Figure 7b This is a schematic diagram of the stepped intersection feature;

[0094] Figure 7c This is a schematic diagram illustrating the parallel intersecting features;

[0095] Figure 7d A schematic diagram of the outline of a simple feature volume unit;

[0096] Figure 7e A schematic diagram of the outline of a stepped intersecting feature domain unit;

[0097] Figure 7f This is a schematic diagram of the outline of a parallel intersecting feature domain unit. Detailed Implementation

[0098] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0099] Example 1:

[0100] like Figure 1 This invention provides an automatic identification method for intersecting features based on processability analysis, comprising the following steps: Step 1: Processability analysis; Step 2: Segmentation surface construction; Step 3: Volume domain unit generation; Step 4: Intersecting volume domain construction.

[0101] Step 1 includes: based on the swing range of the five-axis machine tool's tool axis and the reasonable tilt angle range of different machining methods, and based on the definition of machinability and the classification of machining surface types, obtaining the machining method of each surface, and comprehensively judging and identifying the end face based on the surface machining method and the tool reachability geometric algorithm.

[0102] Define the set of selectable tool axis directions and tool reachability:

[0103] Definition 1: The set of selectable tool axis directions is defined as follows: Within the machine tool's motion limits, the selectable tool axis direction v t The set of all selectable directions for the tool axis, determined by controlling the movement of the machine tool's tool axis, is called the tool axis selectable direction set, denoted by V. t represent.

[0104] Definition 2: Tool reachability is defined as follows: Let P f V is a point on surface f of the part after the process. t For the set of possible tool axis directions, if v exists t ∈V t And ray L(P) f ,v t If a point does not intersect with the subsequent workpiece in the process, then it is called point P. f With tool reachability, v t For P f The tool axis can be selected in a direction; otherwise, for any v t ∈V t , ray L(P f ,v t If all points P intersect with the subsequent workpieces in the same process, then point P is called point P. f P lacks tool reachability f There is no selectable tool axis direction.

[0105] A schematic diagram of tool accessibility is shown below. Figure 2 As shown, the workpiece after the process has a closed angle, and the dashed line represents the limit of the tool axis swing. If point A (the unmachined point) is forcibly machined, the tool will inevitably interfere with the workpiece after the process. Therefore, point A is not accessible to the tool, and only point B (the machined point) is accessible to the tool.

[0106] Tool accessibility describes the machinability of the workpiece surface after the operation under conditions of tool axis oscillation restriction and no interference. When a certain machining method is clearly adopted, the limitations of the machining method on the tool axis should be further considered.

[0107] The machining method decision is based on the definition of machinability and the classification of machining surface types to determine the machining method for each surface. In the CNC machining of complex features, the surface machining methods for parts are divided into bottom-cutting, side-cutting, and fillet machining, with significant differences in the tool axis tilt angle under these three methods. To rigorously describe the machinability of the workpiece surface after a specific machining method, reasonable ranges for three and four tool axis tilt angles are defined.

[0108] In definition 3, the tool axis tilt angle is defined as follows: Let P f Let v be any point on surface f in the model. t The tool axis can be selected in any direction, and n is the direction of the face f in P. fExternal normal vector at point v t The angle between v and n is θ, and θ is called v. t At point P f The angle of the cutter shaft at that location.

[0109] Definition 4 states that the reasonable range of the tool axis tilt angle is defined as follows: Under a certain machining method mt, the tool axis tilt angle θ can only be within a certain specific range Θ. mt The range of values ​​within this range is called the reasonable tool axis tilt angle range. If the tool axis can be selected in direction v... t At point P f If the tool axis tilt angle falls within the reasonable tool axis tilt angle range, then it is called v t Let P be the point f The appropriate tool axis direction can be selected under this machining method (mt).

[0110] Figure 3 illustrates the tool axis tilt angles for the three machining methods. In bottom-cutting machining, the tool end face contacts the workpiece surface after the process, and the tool axis direction is parallel or nearly parallel to the normal to the cutting point. The reasonable tool axis tilt angle range is [0, α] (α ∈ [0, π / 2]). In side-cutting machining, the tool side contactes the workpiece surface after the process, and the tool axis direction is perpendicular to the normal to the cutting point. The reasonable tool axis tilt angle range is π / 2. In fillet machining, the tool bottom R contacts the workpiece surface after the process, and the tool axis direction is neither parallel nor perpendicular to the normal to the cutting point. The reasonable tool axis tilt angle range is [α, π / 2 - β] (α, β ∈ [0, π / 2]). Here, α and β are constants set to ensure algorithm stability, typically taken as 5° or 15°.

[0111] To describe the relationship between the tool machining process and the surface geometry of the workpiece after the process, the surface in contact with the tool cutting is defined as Definition 5.

[0112] Definition 5, the end face is defined as follows: Under a certain machining method mt, when the tool axis inclination angle θ and the tool axis vector are reasonably selected, the surface of the workpiece after the process is machined by the bottom cutting edge is called the end face.

[0113] As defined in Definition 5, the end face should be identified by combining the surface processing method and the tool accessibility geometric algorithm. Therefore, the end face identification steps are: (1) Input the given sequence of selectable processing methods mt1, mt2, ..., mt n (2) Analyze the machinability of the workpiece surface under different processing methods according to the sequence of optional processing methods; (3) Determine whether the workpiece surface is within a certain processing method mt. i If the next processing method (mt) is available, exit the loop; otherwise, analyze its next processing method (mt). i+1 (4) If the surface of the workpiece after the process is not machinable under all selectable processing methods, it is determined to be an unmachinable surface.

[0114] Among them, the method for judging the machinability of the surface of the workpiece after the process is: (1) Input the selectable tool axis direction set V t Processing method MT i Reasonable tool axis tilt angle range Θ mt (2) Obtain sampling point P on surface f after the process. s Calculate P s (3) Calculate the set {v} t |v t ∈V t and <v t ,n>∈Θ mt};(4) Search and model do not interfere with each other v t If found, then click P. s It can be processed under processing mode MT; otherwise, point P. s Unprocessable, surface f is also unprocessable; (5) if all sampling points P s Both can be processed; the judgment surface f is determined by the processing method mt. i The following can be processed; otherwise, the surface f is processed in the mt mode. i It cannot be processed.

[0115] Step 2 includes: selecting the end face as the reference face, and constructing the segmentation surface by extending the reference face.

[0116] Segmentation surface extension refers to finding the end working surface based on the workpiece after the process and extending the end working surface to obtain the segmentation surface. In five-axis machining feature recognition, the workpiece surface used to construct the segmentation surface is called the reference surface. Reference surface extension is divided into two steps: (1) Obtaining the geometric information of the reference surface. Obtain the geometric data of the reference surface according to the CAD system interface, including the surface type, surface normal, surface axis, surface boundary, etc.; (2) Extending the reference surface. Perform the extension operation of the reference surface according to the surface type. If the layered reference surface is a plane or part of a quadratic surface such as a cylindrical surface, sphere, or torus, then the segmentation surface after its extension is a complete plane or quadratic surface. If the layered reference surface is a free surface, the segmentation surface is constructed according to the free surface extension rules such as tangent continuity or curvature continuity.

[0117] Step 3 includes: calculating the difference between the preceding and succeeding parts of the process to obtain the processing domain; and using a dividing surface to intersect and divide the processing domain to obtain the processing area, wherein the intersection operation obtains a two-dimensional region range limited by inner and outer rings, and the division operation obtains the processing domain unit.

[0118] The difference method is used to solve for the domain to be processed. Following the methods commonly used in this field, the difference between the preceding and succeeding parts of the process is used to form the domain to be processed. A diagram illustrating the difference is shown below. Figure 4a As shown, the shading spots represent the volume region to be processed. The processing area is obtained by finding the intersection of the segmented surface and the volume region. The resulting two-dimensional processing area is shown in the figure. Figure 4b As shown. Figure 4a The medium-thick line contour represents the contour of the workpiece preceding the process, while the thin line contour represents the contour of the workpiece following the process. There are complex nested relationships between the contours of the workpiece preceding and following the process. After subtracting, the nested relationships are transformed into parallel relationships, simplifying the difficulty of identifying the processing domain. After solving the intersection problem for the two-dimensional processing region, the two-dimensional region can be represented by one outer ring and n inner rings (n≥1).

[0119] To solve the two-dimensional machining region, relevant operator definitions are given, including Definition 6 Intersection operator between the dividing surface and the machining region, Definition 7 Region decomposition operator, and Definition 8 Region contour operator.

[0120] Definition 6 defines the intersection operator between the dividing surface and the volume domain to be processed as follows: Let the dividing surface be l and the volume domain to be processed be m. Let l and m intersect, and let F be the set of intersecting surface domains of l and m. s , denoted as F s =Intersect(l,m), which is called the intersection operator.

[0121] Definition 7 states that the surface decomposition operator is defined as follows: Let F be a set of intersecting surface regions. s It consists of multiple unconnected surface regions, denoted as f. d1 f d2 , ..., f dn F s These regions can be obtained after decomposition, denoted as (f d1 f d2 , ..., f dn = Disassemble(F) s ), where Disassemble(F s ) is the region decomposition operator.

[0122] Definition 8, the region contour operator is defined as follows: Let F be the set of intersecting regions. s Its contour ring set (grouped by region and distinguishing between outer and inner rings) is denoted as C. b For the set of intersecting surface regions F s After finding the contour, we get C. b , denoted as C b =Boundary(F s ), where Boundary(F s ) is the region contour operator.

[0123] The process of solving the two-dimensional machining region using the intersection method is as follows:

[0124] Step 1: Input the dividing surface l and the volume to be processed m;

[0125] Step 2: Use l to find the intersection, and obtain the set of intersecting surface regions F. s =Intersect(l,m);

[0126] Step 3: Check the set of intersecting surface regions F one by one. s If a result is invalid, retain the valid result and delete the invalid result.

[0127] Step 4: Find the intersection profile C b =Boundary(F s );

[0128] Step 5: Utilize the intersecting contour C b For the set of intersecting surfaces F of the predecessor s Perform negative toroidal clipping, and denote the clipping result as F. l =Trim(F s C b );

[0129] Step 6: For F l Perform region decomposition and exclude invalid regions; the result is denoted as (f1, f2, ..., f n = Disassemble(F) s ), and output.

[0130] The partitioning method solves for volumetric elements by using partitioning surfaces to partition the volumetric area to be processed, thus obtaining the volumetric elements to be processed. It consists of two steps: (1) Performing the partitioning operation, with the partitioning surfaces as partitioning elements and the volumetric area to be processed as the partitioning object. The partitioning operation is performed using the CAD system interface to obtain the partitioning result; (2) Splitting the partitioned object, splitting the partitioning result into individual volumetric elements, and storing them separately for subsequent element combination steps.

[0131] Step 4 includes: constructing a volume domain unit tree through the dependencies between volume domain units, merging volume domain units with the same dependency surface, constructing intersecting volume domains, and completing the identification of intersecting features.

[0132] The domain unit tree is constructed by determining the domain units that the domain unit depends on or is depended on according to the vertical dependency relationship, and constructing a tree structure. The construction steps are as follows: (1) Input domain units v1, v2, ..., v n (2) Extract the set consisting of the lower interfaces of all volumetric units as S. d (3) Process each volumetric unit v i The bottom interface D di (4) Accessing each volumetric unit v one by one i If v i If there is no parent domain element, set its parent domain element as the root node T; (5) Output the volume domain unit tree.

[0133] The aforementioned body domain unit v i The bottom interface D di (i = 1, 2, ..., n) The processing method is: (1) Find the items containing D in the predecessor and successor of the process. di The set of faces is F di (2) Calculate H di =D di -F di (3) For H di Each constituting region, from the center of the region along H di Create a ray h from the external normal vector at the center of the region. j (4) Using h j and S d -D di Find the intersection point, and denote the closest intersection point as P. k (5) By P k Define the volumetric unit v k , let v k For v i subdomain element, v i For v k The parent domain element, as shown in the diagram. Figure 5 As shown.

[0134] Volumetric units are merged by analyzing the geometric relationships between the inner and outer ring contours to determine the dependency lines and dependency surfaces, and volumetric units with the same dependency relationships are merged.

[0135] Let C be the intersection profile of the dividing surface l and a certain workpiece m, and let the intersection line l be... i (i = 1, 2, ..., n) are the constituent elements of C. According to Definition 9 (dependency line) and Definition 10 (dependency surface), l i The geometric elements on the domain m to be processed can be either dependent lines or dependent surfaces.

[0136] Definition 9 states that the dependency line is defined as follows: if the intersection line l i It is the dividing surface l and a certain line l on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Depends on line l m .

[0137] Definition 10 states that the dependency surface is defined as follows: if the intersection line l i It is the dividing surface l and a certain surface f on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Directly dependent on surface f m For the intersection line l i Depends on line l m In this case, it is called line l m The two sides are the intersection line li The indirect dependencies are collectively referred to as the intersection dependencies.

[0138] Figure 6 shows a schematic diagram of the intersection line dependency line and the intersection line dependency surface. Figure 6a The intersection line depends on l1, and its dependency surfaces are f1 and f2. Figure 6b The intersection line depends only on surface f3 and has no other intersection line.

[0139] Intersection feature generation involves determining the vertical positional relationships between volumetric units by traversing a tree model, and then constructing specific intersecting volumes based on the dependencies between these units, thus completing the identification of intersection features. The three types of features used in this patent description are simple features, stepped intersection features, and parallel intersection features. The characteristics of each type of feature and its volumetric unit contour are shown in Figure 7. A schematic diagram of a simple feature is shown below. Figure 7a As shown, the contour of its volumetric unit is as follows Figure 7d As shown, there is no vertical dependency between volumetric units; the stepped intersection feature is illustrated as follows. Figure 7b As shown, the contour of its volumetric unit is as follows Figure 7e As shown, there is a vertical dependency between volumetric units; the parallel intersecting feature is illustrated as follows. Figure 7c As shown, the contour of its volumetric unit is as follows Figure 7f As shown, there are lateral dependencies between domain units.

[0140] Let v be a volumetric element, and let C be the outer ring of its lower interface contour. v Based on the contours and longitudinal dependencies of the volumetric units of the processing features, rules 1, 2, 3, and 4 are given to determine the processing feature type of the volumetric unit.

[0141] Rule 1, if for If edge e is an inner loop formed by the process, and the volume unit v does not have any dependency or being depended on other volume units, then the volume unit v represents a simple feature.

[0142] Rule 2, if for If edge e is an inner ring formed by the subsequent process, and there are other volumetric units that depend on volumetric unit v, then volumetric unit v represents the upper layer feature of the stepped intersection feature.

[0143] Rule 3, if for If edge e is an inner ring formed by the process, and volume unit v depends on other volume units, then volume unit v represents the lower layer feature of the stepped intersecting feature.

[0144] Rule 4, if for If edge r is formed by the outer ring of the preceding workpiece, then the volume unit v represents the parallel intersecting features.

[0145] Based on the above rules, corresponding geometric algorithms can be developed to construct simple features with no dependency, intersecting features with vertical or horizontal dependency, and are suitable for the automatic identification of intersecting features composed of stepped and parallel slots, bosses, and holes.

[0146] Example 2:

[0147] The present invention also provides an automatic intersection feature recognition system based on processability analysis. The automatic intersection feature recognition system based on processability analysis can be implemented by executing the process steps of the automatic intersection feature recognition method based on processability analysis. That is, those skilled in the art can understand the automatic intersection feature recognition method based on processability analysis as a preferred embodiment of the automatic intersection feature recognition system based on processability analysis.

[0148] The automatic intersection feature recognition system based on manufacturability analysis provided by the present invention includes: Module M1: Based on the swing range of the five-axis machine tool axis and the tilt range of different machining methods, and according to the definition of manufacturability and the classification of machining surface types, the machining method of each surface is obtained, and the end face is identified by comprehensively judging based on the surface machining method and the tool reachability geometric algorithm; Module M2: The end face is selected as the reference surface, and a segmentation surface is constructed by extending the reference surface; Module M3: The difference between the preprocessor and the postprocessor is calculated to obtain the machining domain of the process; the intersection and segmentation of the segmentation surface and the machining domain are used to obtain the machining area, wherein the intersection operation obtains the two-dimensional region range restricted by the inner and outer rings, and the segmentation operation obtains the machining domain unit; Module M4: A domain unit tree is constructed through the dependency relationship between the domain units, and domain units with the same dependency surface are merged to construct the intersecting domain, thus completing the recognition of the intersection feature.

[0149] The module M1 includes:

[0150] The set of selectable tool axis directions is defined as follows: Within the machine tool's motion limits, the selectable tool axis direction v t The set of all selectable directions for the machine tool's tool axis, achieved by controlling its movement, is called the tool axis selectable direction set, denoted by V. t express;

[0151] Tool reachability is defined as follows: Let P f V is a point on surface f of the part after the process. t For the set of possible tool axis directions, if v exists t ∈V t And ray L(P) f ,v t If a point does not intersect with the subsequent workpiece in the process, then it is called point P. f With tool reachability, v t For P f The tool axis can be selected in a direction; if for any vt ∈V t , ray L(P f ,v t If all points P intersect with the subsequent workpieces in the same process, then point P is called point P. f P lacks tool reachability f There is no selectable tool axis direction;

[0152] The surface finishing methods for parts are divided into bottom edge machining, side edge machining, and corner rounding.

[0153] The cutter axis tilt angle is defined as follows: Let P f Let v be any point on surface f in the model. t The tool axis can be selected in any direction, and n is the direction of the face f in P. f External normal vector at point v t The angle between v and n is θ, and θ is called v. t At point P f The angle of the cutter shaft at the location;

[0154] The reasonable range of tool axis tilt angle is defined as follows: Under a certain machining method mt, the tool axis tilt angle θ can only be within a certain specific range Θ. mt The range of values ​​within this range is called the reasonable tool axis tilt angle range; if the tool axis can be selected in direction v t At point P f If the tool axis tilt angle falls within the reasonable tool axis tilt angle range, then it is called v t Let P be the point f Under this machining method (mt), the appropriate tool axis direction can be selected.

[0155] The end face is defined as follows: Under a certain machining method mt, when the tool axis inclination angle θ and tool axis vector are reasonably selected, the surface of the workpiece after the process is machined by the bottom cutting edge is called the end face;

[0156] The end face recognition process includes: inputting a given sequence of selectable processing methods mt1, mt2, ..., mt n And the surface f of the workpiece after the process; analyze the machinability of the surface of the workpiece under different processing methods according to the sequence of optional processing methods; determine whether the surface of the workpiece after the process is within a certain processing method mt. i If the next processing method (mt) is available, exit the loop; otherwise, analyze its next processing method (mt). i+1 Machinability under the following conditions; if the surface of the workpiece after the process is not machinable under all selectable machining methods, it is determined to be an unmachinable surface;

[0157] The process of determining the machinability of the workpiece surface after the process is as follows: Input the selectable tool axis direction set V t Processing method MT i Reasonable tool axis tilt angle range Θ mt After the process, the surface f of the workpiece is sampled; sampling point P is obtained on surface f. s Calculate Ps External normal vector n; calculate set {v} t |v t ∈V t and <v t ,n>∈Θ mt}; Search and model do not interfere with each other. t If found, then click P. s It can be processed under processing mode MT; otherwise, point P. s It is not machinable, and the surface f is also not machinable; if all sampling points P s If both can be processed, then the determination of surface f in processing method mt is... i The following can be processed; otherwise, the surface f is processed in the mt mode. i It cannot be processed.

[0158] The module M2 includes: Module M2.1: Obtaining geometric data of the reference surface according to the CAD system interface, including surface type, surface normal, surface axis and surface boundary; Module M2.2: Performing the extension operation of the reference surface according to the surface type. If the layered reference surface is part of a plane or quadratic surface, the extended layer is a complete plane or quadratic surface; if the layered reference surface is a freeform surface, the segmented surface is constructed according to the freeform surface extension rules.

[0159] The module M3 includes:

[0160] The intersection operator between the dividing surface and the volume domain to be processed is defined as follows: Let the dividing surface be l and the volume domain to be processed be m. Let l and m intersect, and let F be the set of intersecting surface domains of l and m. s , denoted as F s =Intersect(l,m), which is called the intersection operator;

[0161] The domain decomposition operator is defined as follows: Let F be the set of intersecting domains. s It consists of multiple unconnected surface regions, denoted as f. d1 f d2 , ..., f dn F s These regions are obtained after decomposition, denoted as (f d1 f d2 , ..., f dn = Disassemble(F) s ), where Disassemble(F s ) is the region decomposition operator;

[0162] The contour operator for a region is defined as follows: Let F be the set of intersecting regions. s Its contour ring set is denoted as C b For the set of intersecting surface regions F sAfter finding the contour, we get C. b , denoted as C b =Boundary(F s ), where Boundary(F s ) represents the region contour operator;

[0163] The process of solving the two-dimensional machining region using the intersection method is as follows: Input the dividing surface l and the volume region to be processed m; use l to find the intersection to obtain the set of intersecting surface regions F. s =Intersect(l,m); This function iterates through the set of intersecting surfaces F. s Determine if the intersection is valid, retain valid faces and delete invalid faces; find the intersection profile C. b =Boundary(F s ); using the intersecting profile C b For the set of intersecting surfaces F of the predecessor s Perform negative toroidal clipping, and denote the clipping result as F. l =Trim(F s C b ); For F l Perform region decomposition and exclude invalid regions; the result is denoted as (f1, f2, ..., f n = Disassemble(F) s ), and output;

[0164] The process of solving volumetric domain elements by the segmentation method is as follows: the segmentation surface is used as the segmentation element, the volumetric domain to be processed in the process is used as the segmentation object, the segmentation operation is performed using the CAD system interface, the segmentation result is obtained, and the segmentation result is split into individual volumetric domain elements and stored separately.

[0165] The module M4 includes:

[0166] For each volumetric unit, determine the volumetric units that the volumetric unit depends on or is depended on according to the vertical dependency relationship, and construct a tree structure. The construction process is as follows: Input volumetric units v1, v2, ..., v n Extract the set consisting of the lower interfaces of all volumetric units as S. d Process volumetric units v one by one i The bottom interface D di Accessing volumetric units v one by one i If v i For elements without a parent, set their parent element as the root node T; output the volume domain unit tree.

[0167] Body domain unit v i The bottom interface D di The processing procedure is as follows: Find the workpieces preceding and following the process that contain D. di The set of faces is F di ; Calculate H di=D di -F di ; For H di Each constituting region, from the center of the region along H di Create a ray h from the external normal vector at the center of the region. j ; use h j and S d -D di Find the intersection point, and denote the closest intersection point as P. k ; by P k Define the volumetric unit v k , where v k For v i Subfield elements, i = 1, 2, ..., n;

[0168] By analyzing the geometric relationship between the inner and outer ring contours, the relationship between dependency lines and dependency surfaces is determined, and volumetric units with the same dependency relationship are merged.

[0169] Dependency lines are defined as follows: if the intersection line l i It is the dividing surface l and a certain line l on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Depends on line l m ;

[0170] The dependency surface is defined as follows: if the intersection line l i It is the dividing surface l and a certain surface f on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Directly dependent on surface f m For the intersection line l i Depends on line l m In this case, it is called line l m The two sides are the intersection line l i The indirect dependency surfaces, and the direct dependency surfaces and indirect dependency surfaces are collectively referred to as the intersection dependency surfaces;

[0171] By traversing the tree model, the vertical positional relationship between volume domain units is determined. Combined with the dependency relationship of volume domain units, specific intersecting volumes are constructed to complete the identification of intersection features.

[0172] Let v be a volumetric element, and let C be the outer ring of its lower interface contour. v Based on the volumetric unit contours and longitudinal dependencies of the processing features, the type of processing feature of the volumetric unit can be determined.

[0173] If If edge e is an edge formed by the inner loop of the subsequent workpiece, and the volume unit v does not have any dependency or being depended on other volume units, then the volume unit v represents a simple feature.

[0174] If If edge e is an edge formed by the inner ring of the workpiece after the process, and there are other volume units that depend on volume unit v, then volume unit v represents the upper layer feature of the stepped intersection feature.

[0175] If If edge e is an edge formed by the inner ring of the workpiece after the process, and the volume unit v depends on other volume units, then the volume unit v represents the lower layer feature of the stepped intersecting feature.

[0176] If If edge r is formed by the outer ring of the preceding workpiece, then the volume unit v represents the parallel intersecting features.

[0177] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0178] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. An automatic identification method for intersecting features based on processability analysis, characterized in that, include: Step 1: Based on the swing range of the five-axis machine tool's tool axis and the tilt range of different machining methods, and according to the definition of machinability and the classification of machining surface types, obtain the machining method for each surface. Based on the surface machining method and the tool reachability geometric algorithm, comprehensively judge and identify the end face. The end face is defined as follows: Under a certain machining method mt, when the tool axis inclination angle θ and tool axis vector are reasonably selected, the surface of the workpiece after the process is machined by the bottom cutting edge is called the end face; Step 2: Select the end face as the reference plane, and construct the segmentation surface by extending the reference plane; Step 3: Calculate the difference between the predecessor and successor of the process to obtain the volume region to be processed; use the intersection and segmentation of the segmentation surface with the volume region to be processed to obtain the processing area. The intersection operation obtains the two-dimensional region range bounded by inner and outer rings, and the segmentation operation obtains the volume unit to be processed. Step 4: Construct a volume domain unit tree based on the dependencies between volume domain units, merge volume domain units with the same dependency surface, construct intersecting volume domains, and complete the identification of intersection features; Step 4 includes: For each volumetric unit, determine the volumetric units that the volumetric unit depends on or is depended on according to the vertical dependency relationship, and construct a tree structure. The construction process is as follows: Input volumetric units v1, v2, ..., v n Extract the set consisting of the lower interfaces of all volumetric units as S. d Process volumetric units v one by one i The bottom interface D di Accessing volume domain units v one by one i If v i For elements without a parent, set their parent element as the root node T; output the volume domain unit tree. Body domain unit v i The bottom interface D di The processing procedure is as follows: Find the workpieces preceding and following the process that contain D. di The set of faces is F di ; Calculate H di =D di -F di ; For H di Each constituting region, from the center of the region along H di Create a ray h from the external normal vector at the center of the region. j ; use h j and S d -D di Find the intersection point, and denote the closest intersection point as P. k ; by P k Define the volumetric unit v k , where v k For v i Subfield elements, i = 1, 2, ..., n; By analyzing the geometric relationship between the inner and outer ring contours, the relationship between dependency lines and dependency surfaces is determined, and volumetric units with the same dependency relationship are merged. Dependency lines are defined as follows: if the intersection line l i It is the dividing surface l and a certain line l on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Depends on line l m ; The dependency surface is defined as follows: if the intersection line l i It is the dividing surface l and a certain surface f on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Directly dependent on surface f m For the intersection line l i Depends on line l m In this case, it is called line l m The two sides are the intersection line l i The indirect dependency surfaces, and the direct dependency surfaces and indirect dependency surfaces are collectively referred to as the intersection dependency surfaces; By traversing the tree model, the vertical positional relationship between volume domain units is determined. Combined with the dependency relationship of volume domain units, specific intersecting volumes are constructed to complete the identification of intersection features. Let v be a volumetric element, and let C be the outer ring of its lower interface contour. v Based on the volumetric unit contours and longitudinal dependencies of the processing features, the type of processing feature of the volumetric unit can be determined. If If edge e is an edge formed by the inner loop of the subsequent workpiece, and the volume unit v does not have any dependency or being depended on other volume units, then the volume unit v represents a simple feature. If If edge e is an edge formed by the inner ring of the workpiece after the process, and there are other volume units that depend on volume unit v, then volume unit v represents the upper layer feature of the stepped intersection feature. If If edge e is an edge formed by the inner ring of the workpiece after the process, and the volume unit v depends on other volume units, then the volume unit v represents the lower layer feature of the stepped intersecting feature. If If edge r is formed by the outer ring of the preceding workpiece, then the volume unit v represents the parallel intersecting features.

2. The automatic identification method for intersection features based on processability analysis according to claim 1, characterized in that, Step 1 includes: The set of selectable tool axis directions is defined as follows: Within the machine tool's motion limits, the selectable tool axis direction v t The set of all selectable directions for the machine tool's tool axis, achieved by controlling its movement, is called the tool axis selectable direction set, denoted by V. t express; Tool reachability is defined as follows: Let P f V is a point on surface f of the part after the process. t For the set of possible tool axis directions, if v exists t ∈V t And ray L(P) f ,v t If a point does not intersect with the subsequent workpiece in the process, then it is called point P. f With tool reachability, v t For P f The tool axis can be selected in a direction; if for any v t ∈V t , ray L(P f ,v t If all points P intersect with the subsequent workpieces in the same process, then point P is called point P. f P lacks tool reachability f There is no selectable tool axis direction; The surface finishing methods for parts are divided into bottom edge machining, side edge machining, and corner rounding. The cutter axis tilt angle is defined as follows: Let P f Let v be any point on surface f in the model. t The tool axis can be selected in any direction, and n is the direction of the face f in P. f External normal vector at point v t The angle between v and n is θ, and θ is called v. t At point P f The angle of the cutter shaft at the location; The reasonable range of tool axis tilt angle is defined as follows: Under a certain machining method mt, the tool axis tilt angle θ can only be within a certain specific range Θ. mt The range of values ​​within this range is called the reasonable tool axis tilt angle range; if the tool axis can be selected in direction v t At point P f If the tool axis tilt angle falls within the reasonable tool axis tilt angle range, then it is called v t Let P be the point f Under this machining method (mt), the appropriate tool axis direction can be selected. The end face recognition process includes: inputting a given sequence of selectable processing methods mt1, mt2, ..., mt n And the surface f of the workpiece after the process; analyze the machinability of the surface of the workpiece under different processing methods according to the sequence of optional processing methods; determine whether the surface of the workpiece after the process is within a certain processing method mt. i If the next processing method (mt) is available, exit the loop; otherwise, analyze its next processing method (mt). i+1 Machinability under the following conditions; if the surface of the workpiece after the process is not machinable under all selectable machining methods, it is determined to be an unmachinable surface; The process of determining the machinability of the workpiece surface after the process is as follows: Input the selectable tool axis direction set V t Processing method MT i Reasonable cutter shaft tilt angle range Θ mt After the process, the surface f of the workpiece is sampled; sampling point P is obtained on surface f. s Calculate P s External normal vector n; calculate set {v} t |v t ∈V t and <v t ,n>∈Θ mt }; Search and model do not interfere with each other. t If found, then click P. s It can be processed under machining mode MT; otherwise, point P. s It is not machinable, and the surface f is also not machinable; if all sampling points P s If both can be processed, then the determination of surface f in processing method mt is... i The following can be processed; otherwise, the surface f is processed in the mt mode. i It cannot be processed.

3. The automatic identification method for intersection features based on manufacturability analysis according to claim 1, characterized in that, Step 2 includes: Step 2.1: Obtain the geometric data of the reference plane according to the CAD system interface, including the plane type, plane normal, plane axis and plane boundary; Step 2.2: Perform the extension operation of the reference surface according to the surface type. If the layered reference surface is part of a plane or quadratic surface, the extended layer is a complete plane or quadratic surface; if the layered reference surface is a freeform surface, construct the segmented surface according to the freeform surface extension rules.

4. The automatic identification method for intersection features based on manufacturability analysis according to claim 1, characterized in that, Step 3 includes: The intersection operator between the dividing surface and the volume domain to be processed is defined as follows: Let the dividing surface be l and the volume domain to be processed be m. Let l and m intersect, and let F be the set of intersecting surface domains of l and m. s , denoted as F s =Intersect(l,m), which is called the intersection operator; The domain decomposition operator is defined as follows: Let F be the set of intersecting domains. s It consists of multiple unconnected surface regions, denoted as f. d1 f d2 , ..., f dn F s These regions are obtained after decomposition, denoted as (f d1 f d2 , ..., f dn = Disassemble(F) s ), where Disassemble(F s ) is the region decomposition operator; The contour operator for a region is defined as follows: Let F be the set of intersecting regions. s Its contour ring set is denoted as C b For the set of intersecting surface regions F s After finding the contour, we get C. b , denoted as C b =Boundary(F s ), where Boundary(F s ) represents the region contour operator; The process of solving the two-dimensional machining region using the intersection method is as follows: Input the dividing surface l and the volume region to be processed m; use l to find the intersection to obtain the set of intersecting surface regions F. s =Intersect(l,m); This function iterates through the set of intersecting surfaces F. s Determine if the intersection is valid, retain valid faces and delete invalid faces; find the intersection profile C. b =Boundary(F s ); using the intersecting contour C b For the set of intersecting surface regions F of the predecessor s Perform negative toroidal clipping, and denote the clipping result as F. l =Trim(F s C b ); For F l Perform region decomposition and exclude invalid regions; the result is denoted as (f1, f2, ..., f n = Disassemble(F) s ), and output; The process of solving volumetric domain elements by the segmentation method is as follows: the segmentation surface is used as the segmentation element, the volumetric domain to be processed in the process is used as the segmentation object, the segmentation operation is performed using the CAD system interface, the segmentation result is obtained, and the segmentation result is split into individual volumetric domain elements and stored separately.

5. An automatic intersecting feature recognition system based on manufacturability analysis, characterized in that, include: Module M1: Based on the swing range of the five-axis machine tool's tool axis and the tilt range of different machining methods, and according to the definition of machinability and the classification of machining surface types, the machining method of each surface is obtained. Based on the surface machining method and the tool reachability geometric algorithm, the end face is comprehensively judged and identified. The end face is defined as follows: Under a certain machining method mt, when the tool axis inclination angle θ and tool axis vector are reasonably selected, the surface of the workpiece after the process is machined by the bottom cutting edge is called the end face; Module M2: Selects the end face as the reference plane and constructs the segmentation surface by extending the reference plane; Module M3: The difference between the predecessor and successor of the process is calculated to obtain the volume region to be processed in the process; the processing area is obtained by intersecting and dividing the volume region with the dividing surface. The intersection operation obtains the two-dimensional region range bounded by inner and outer rings, and the division operation obtains the volume unit to be processed. Module M4: Constructs a volume domain unit tree based on the dependencies between volume domain units, merges volume domain units with the same dependency surface, constructs intersecting volume domains, and completes the identification of intersecting features; The module M4 includes: For each volumetric unit, determine the volumetric units that the volumetric unit depends on or is depended on according to the vertical dependency relationship, and construct a tree structure. The construction process is as follows: Input volumetric units v1, v2, ..., v n Extract the set consisting of the lower interfaces of all volumetric units as S. d Process volumetric units v one by one i The bottom interface D di Accessing volume domain units v one by one i If v i For elements without a parent, set their parent element as the root node T; output the volume domain unit tree. Body domain unit v i The bottom interface D di The processing procedure is as follows: Find the workpieces preceding and following the process that contain D. di The set of faces is F di ; Calculate H di =D di -F di ; For H di Each constituting region, from the center of the region along H di Create a ray h from the external normal vector at the center of the region. j ; use h j and S d -D di Find the intersection point, and denote the closest intersection point as P. k ; by P k Define the volumetric unit v k , where v k For v i Subfield elements, i = 1, 2, ..., n; By analyzing the geometric relationship between the inner and outer ring contours, the relationship between dependency lines and dependency surfaces is determined, and volumetric units with the same dependency relationship are merged. Dependency lines are defined as follows: if the intersection line l i It is the dividing surface l and a certain line l on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Depends on line l m ; The dependency surface is defined as follows: if the intersection line l i It is the dividing surface l and a certain surface f on the surface of the workpiece. m The result of the intersection is called the intersection line l. i Directly dependent on surface f m For the intersection line l i Depends on line l m In this case, it is called line l m The two sides are the intersection line l i The indirect dependency surfaces, and the direct dependency surfaces and indirect dependency surfaces are collectively referred to as the intersection dependency surfaces; By traversing the tree model, the vertical positional relationship between volume domain units is determined. Combined with the dependency relationship of volume domain units, specific intersecting volumes are constructed to complete the identification of intersection features. Let v be a volumetric element, and let C be the outer ring of its lower interface contour. v Based on the volumetric unit contours and longitudinal dependencies of the processing features, the type of processing feature of the volumetric unit can be determined. If If edge e is an edge formed by the inner loop of the subsequent workpiece, and the volume unit v does not have any dependency or being depended on other volume units, then the volume unit v represents a simple feature. If If edge e is an edge formed by the inner ring of the workpiece after the process, and there are other volume units that depend on volume unit v, then volume unit v represents the upper layer feature of the stepped intersection feature. If If edge e is an edge formed by the inner ring of the workpiece after the process, and the volume unit v depends on other volume units, then the volume unit v represents the lower layer feature of the stepped intersecting feature. If If edge r is formed by the outer ring of the preceding workpiece, then the volume unit v represents the parallel intersecting features.

6. The automatic intersection feature recognition system based on manufacturability analysis according to claim 5, characterized in that, The module M1 includes: The set of selectable tool axis directions is defined as follows: Within the machine tool's motion limits, the selectable tool axis direction v t The set of all selectable directions for the machine tool's tool axis, achieved by controlling its movement, is called the tool axis selectable direction set, denoted by V. t express; Tool reachability is defined as follows: Let P f V is a point on surface f of the part after the process. t For the set of possible tool axis directions, if v exists t ∈V t And ray L(P) f ,v t If a point does not intersect with the subsequent workpiece in the process, then it is called point P. f With tool reachability, v t For P f The tool axis can be selected in a direction; if for any v t ∈V t , ray L(P f ,v t If all points P intersect with the subsequent workpieces in the same process, then point P is called point P. f P lacks tool reachability f There is no selectable tool axis direction; The surface finishing methods for parts are divided into bottom edge machining, side edge machining, and corner rounding. The cutter axis tilt angle is defined as follows: Let P f Let v be any point on surface f in the model. t The tool axis can be selected in any direction, and n is the direction of the face f in P. f External normal vector at point v t The angle between v and n is θ, and θ is called v. t At point P f The angle of the cutter shaft at the location; The reasonable range of tool axis tilt angle is defined as follows: Under a certain machining method mt, the tool axis tilt angle θ can only be within a certain specific range Θ. mt The range of values ​​within this range is called the reasonable tool axis tilt angle range; if the tool axis can be selected in direction v t At point P f If the tool axis tilt angle falls within the reasonable tool axis tilt angle range, then it is called v t Let P be the point f Under this machining method (mt), the appropriate tool axis direction can be selected. The end face is defined as follows: Under a certain machining method mt, when the tool axis inclination angle θ and tool axis vector are reasonably selected, the surface of the workpiece after the process is machined by the bottom cutting edge is called the end face; The end face recognition process includes: inputting a given sequence of selectable processing methods mt1, mt2, ..., mt n And the surface f of the workpiece after the process; analyze the machinability of the surface of the workpiece under different processing methods according to the sequence of optional processing methods; determine whether the surface of the workpiece after the process is within a certain processing method mt. i If the next processing method (mt) is available, exit the loop; otherwise, analyze its next processing method (mt). i+1 Machinability under the following conditions; if the surface of the workpiece after the process is not machinable under all selectable machining methods, it is determined to be an unmachinable surface; The process of determining the machinability of the workpiece surface after the process is as follows: Input the selectable tool axis direction set V t Processing method MT i Reasonable cutter shaft tilt angle range Θ mt After the process, the surface f of the workpiece is sampled; sampling point P is obtained on surface f. s Calculate P s External normal vector n; calculate set {v} t |v t ∈V t and <v t ,n>∈Θ mt }; Search and model do not interfere with each other. t If found, then click P. s It can be processed under processing mode MT; otherwise, point P. s It is not machinable, and the surface f is also not machinable; if all sampling points P s If both can be processed, then the determination of surface f in processing method mt is... i The following can be processed; otherwise, the surface f is processed in the mt mode. i It cannot be processed.

7. The automatic intersection feature recognition system based on manufacturability analysis according to claim 5, characterized in that, The module M2 includes: Module M2.1: Obtains geometric data of the reference plane based on the CAD system interface, including plane type, plane normal, plane axis and plane boundary; Module M2.2: Performs the extension operation of the reference surface according to the surface type. If the layered reference surface is part of a plane or quadratic surface, the extended layer is a complete plane or quadratic surface; if the layered reference surface is a freeform surface, the segmented surface is constructed according to the freeform surface extension rules.

8. The automatic intersection feature recognition system based on manufacturability analysis according to claim 5, characterized in that, The module M3 includes: The intersection operator between the dividing surface and the volume domain to be processed is defined as follows: Let the dividing surface be l and the volume domain to be processed be m. Let l and m intersect, and let F be the set of intersecting surface domains of l and m. s , denoted as F s =Intersect(l,m), which is called the intersection operator; The domain decomposition operator is defined as follows: Let F be the set of intersecting domains. s It consists of multiple unconnected surface regions, denoted as f. d1 f d2 , ..., f dn F s These regions are obtained after decomposition, denoted as (f d1 f d2 , ..., f dn = Disassemble(F) s ), where Disassemble(F s ) is the region decomposition operator; The contour operator for a region is defined as follows: Let F be the set of intersecting regions. s Its contour ring set is denoted as C b For the set of intersecting surface regions F s After finding the contour, we get C. b , denoted as C b =Boundary(F s ), where Boundary(F s ) represents the region contour operator; The process of solving the two-dimensional machining region using the intersection method is as follows: Input the dividing surface l and the volume region to be processed m; use l to find the intersection to obtain the set of intersecting surface regions F. s =Intersect(l,m); This function iterates through the set of intersecting surfaces F. s Determine if the intersection is valid, retain valid faces and delete invalid faces; find the intersection profile C. b =Boundary(F s ); using the intersecting contour C b For the set of intersecting surface regions F of the predecessor s Perform negative toroidal clipping, and denote the clipping result as F. l =Trim(F s C b ); For F l Perform region decomposition and exclude invalid regions; the result is denoted as (f1, f2, ..., f n = Disassemble(F) s ), and output; The process of solving volumetric domain elements by the segmentation method is as follows: the segmentation surface is used as the segmentation element, the volumetric domain to be processed in the process is used as the segmentation object, the segmentation operation is performed using the CAD system interface, the segmentation result is obtained, and the segmentation result is split into individual volumetric domain elements and stored separately.

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