Method for extracting contour line of turning blank on revolution surface of three-dimensional volute model
By constructing a plane that intersects with the rotating surface of the volute model, generating contour lines, and identifying the inner and outer surface groups, the problem of frequent manual intervention in the machining of volute parts is solved, and the automated extraction of contour lines and generation of machining blanks from the rotating surface of the volute model are realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU JITRI HUST INTELLIGENT EQUIP TECH CO LTD
- Filing Date
- 2026-01-16
- Publication Date
- 2026-05-01
AI Technical Summary
Existing technologies struggle to automatically identify the blank contour lines of complex curved rotating parts like volutes, leading to frequent manual intervention during processing and preventing end-to-end automation from the 3D model to the closed wireframe.
By constructing a plane that intersects with the turning surface, the intersection line is obtained and swept around the axis of rotation. The contour line is generated by combining the intersection with the reference plane. The inner and outer side groups are identified by the boundary of the reference plane. The contour lines are deduplicated and sorted, and finally a closed wireframe is formed to generate the machining blank.
It realizes the automated extraction of the contour lines of the rotating surface of the volute model, reduces manual intervention, improves the automation level of the machining process, and is suitable for CNC turning process planning of volute-type complex curved rotating parts.
Smart Images
Figure CN121963180A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of intelligent manufacturing and CNC machining technology, and more specifically, to a method for extracting the outline of a blank during the turning of a three-dimensional volute model. Background Technology
[0002] Turning, as a core process in the manufacturing of rotating parts, relies heavily on the accurate extraction of the blank contour lines for its level of automation. In the context of intelligent manufacturing, "one-click toolpath generation" technology is gradually replacing traditional manual intervention, achieving automated conversion from 3D models to CNC toolpaths through intelligent algorithm chains. Among these, machining feature recognition, as the starting point of the integrated CAD-CAPP-CAM process, directly determines the reliability of subsequent process planning. For conventional rotating parts (such as shafts and sleeves), existing CAD / CAM systems (such as Siemens NX) can automatically extract contour lines through single-section analysis or simple geometric rules. However, the rotating surfaces of complex rotating parts like volutes consist of multiple face groups, including inner and outer surfaces, and form multi-layered topological relationships with the upper and lower reference surfaces, making it difficult for existing technologies to automatically analyze their blank contour lines.
[0003] Existing technologies have limitations in extracting the contour lines of the rotating surfaces of volutes. While the Maximum Turnable State (MTS) algorithm proposed by Yip-Hoi and Dutta provides a computational framework for mill-turn composite parts, the extraction of the maximum turnable state—that is, the solid obtained by sweeping after extracting the turning contour lines—remains a problem to be solved. Other traditional methods, such as the intersection method based on a single Z-axis section, cannot distinguish between "surface groups connected to the outer side of the upper reference plane" and "surface groups connected to the inner side," requiring process engineers to manually annotate the boundaries of face groups. This is especially problematic when the model has topological fragmentation (such as interrupted face group connections), as the logical relationship between the inner and outer face groups completely fails. Although Li and Shah pointed out in "Recognition of Interacting Turning Features for Mill / Turn Parts" that feature interactions lead to changes in topology, their graph theory method focuses on eliminating interference between coaxial features and does not solve the problem of automatic layering of inner and outer face groups in the spiral structure of volutes.
[0004] The aforementioned issues necessitate frequent human-machine interaction during the actual machining of volute parts: manually dividing layers, removing duplicate lines, and repairing outer boundaries. This prevents end-to-end automation from the 3D model to the closed wireframe, becoming a key bottleneck restricting the implementation of intelligent manufacturing. Therefore, the industry urgently needs a method to extract the contour lines of turned surfaces with a single click, reducing manual intervention and improving the automation level from CAD / CAM models to the actual machining process. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for extracting the outline of a blank in the turning process of a three-dimensional volute model, so as to solve the problem that the outline of the blank cannot be automatically identified in the turning process of a three-dimensional volute model.
[0006] As a first aspect of the present invention, a method for extracting the contour lines of a blank machined on a three-dimensional volute model's rotating surface is provided, the method comprising the following steps: Step S1: Input the three-dimensional volute model and extract all turning surfaces from the three-dimensional volute model; Step S2: Traverse each turning surface, take multiple scattered points on the edge of each turning surface, select the scattered point farthest from the axis of rotation, and construct a plane through the farthest scattered point and the axis of rotation. Then intersect the constructed plane with the corresponding turning surface to obtain the intersection line corresponding to each turning surface. Step S3: Sweep each intersecting line around the rotation axis to obtain the corresponding swept toroidal surface, and use the same reference plane to intersect each swept toroidal surface to obtain the contour line of each swept toroidal surface on the same reference plane. Step S4: Remove duplicates and sort all contour lines; Step S5: Connect the sorted outlines to obtain a closed wireframe; Step S6: Sweep the closed wireframe around the axis of rotation to form the machining blank of the three-dimensional volute model.
[0007] Furthermore, the extraction of all turning surfaces from the three-dimensional volute model includes: In all the turning surfaces of the three-dimensional volute model, the horizontal plane with the highest coordinate value in the axial direction is defined as the upper reference plane, and the horizontal plane with the lowest coordinate value in the axial direction is defined as the lower reference plane. Based on the connection relationship of all turning surfaces in the adjacent node diagram, the turning surface group connected to the outside of the upper reference plane is defined as the outer surface group, and the turning surface group connected to the inside of the upper reference plane is defined as the inner surface group. Among all the turning surfaces of the three-dimensional volute model, there must be at least an upper reference surface or a lower reference surface. If there is a lower reference surface but no upper reference surface, the three-dimensional volute model or the rotating shaft is rotated 180° to ensure that the upper reference surface exists.
[0008] Further, step S2 includes: Store the intersection lines corresponding to each turning face into an intersection line list; When the connection between the turning surfaces in the inner side group and / or the turning surfaces in the outer side group is interrupted, multiple lists of intersecting lines are used for storage.
[0009] Further, step S3 includes: Store the contour lines of each swept torus on the same reference plane in a contour line list.
[0010] Further, step S4 includes: Step S41: Create a first list L1 and a second list L2; Step S42: Traverse the contour lines in the contour line list L and compare them with the contour lines in the first list L1; wherein, firstly, select the currently traversed contour line 1 in the contour line list L, and determine whether there is a contour line in the first list L1 that completely overlaps with the contour line 1. If there is, then no processing is done on the contour line 1; if not, then the contour line 1 is added to the first list L1; then, the other contour lines in the contour line list L are sequentially compared with the contour lines in the first list L1 to update the first list L1; Step S43: Traverse the contour lines in the first list L1 and compare them with the contour lines in the second list L2; wherein, firstly, select the contour line 2 currently traversed in the first list L1, and determine whether there is a contour line in the second list L2 that partially overlaps with the contour line 2. If there is, then the contour line 2 is not processed; if there is not, then the contour line 2 is added to the second list L2; then, the other contour lines in the first list L1 are compared with the contour lines in the second list L2 in turn to update the second list L2; Step S44: Output the final updated second list L2. Sort all the contour lines in the final updated second list L2 according to the order of contour lines corresponding to the upper reference plane -> contour lines corresponding to the inner surface group -> contour lines corresponding to the lower reference plane -> contour lines corresponding to the outer surface group to obtain the sorted second list L2.
[0011] Further, determining whether there exists a contour line in the first list L1 that completely coincides with the contour line 1 includes: Obtain the start point S1 and end point E1 of the contour line 1 in the contour line list L, and obtain the start point S2 and end point E2 of a certain contour line in the first list L1. If the following conditions are met: "the distance between the starting point S1 and the starting point S2 is less than the tolerance value, and the distance between the ending point E1 and the ending point E2 is less than the tolerance value", or "the distance between the starting point S1 and the ending point E2 is less than the tolerance value, and the distance between the ending point E1 and the starting point S2 is less than the tolerance value", then it is determined that there is a contour line in the first list L1 that completely overlaps with the contour line 1. If the contour line 1 in the contour line list L does not meet the above conditions with any of the contour lines in the first list L1, then it is determined that there is no contour line in the first list L1 that completely overlaps with the contour line 1.
[0012] Further, determining whether there exists a contour line in the second list L2 that partially overlaps with the contour line 2 includes: Obtain the midpoint M1 of the contour line 2 in the first list L1, and obtain a certain contour line in the second list L2, and calculate the distance between the midpoint M1 of the contour line 2 and the certain contour line in the second list L2. If the distance is less than the tolerance value, it is determined that there is a contour line in the second list L2 that partially overlaps with the contour line 2; wherein, when the length of the contour line 2 is greater than the partially overlapping contour line in the second list L2, the partially overlapping contour line in the second list L2 is replaced with the contour line 2; when the length of the contour line 2 is not greater than the partially overlapping contour line in the second list L2, the contour line 2 is not processed. If the distance is not less than the tolerance value, it is determined that there is no contour line in the second list L2 that partially overlaps with the contour line 2.
[0013] Further, step S44 includes: The contour lines corresponding to the inner side surface group are sorted by axial height from high to low; The contour lines corresponding to the outer surface group are sorted by axial height from low to high.
[0014] Further, step S5 includes: The sorted outlines are connected to form an initial wireframe; if the initial wireframe is incomplete, it is completed to obtain the closed wireframe. Wherein, when the inner contour line corresponding to the inner side group of the initial wireframe is missing, a straight line is used to fill in the missing inner contour line; Specifically, when the outer contour line corresponding to the outer side group of the initial wireframe is missing, the missing outer contour line is filled in.
[0015] Furthermore, the step of completing the missing outer contour line when the outer contour line corresponding to the outer side group of the initial wireframe is missing includes: If the upper reference plane has no outer surface group, the outermost coordinate of the contour line corresponding to the upper reference plane is used, denoted as P1; if the upper reference plane has an outer surface group, the outermost coordinate of the contour line corresponding to the outer surface group is used, denoted as P1. If the lower reference plane has no outer surface group, the outermost coordinate of the contour line corresponding to the lower reference plane is used, denoted as P2; if the lower reference plane has an outer surface group, the outermost coordinate of the contour line corresponding to the outer surface group is used, denoted as P2; if there is no lower reference plane and no outer surface group connected to the lower reference plane, the lowest coordinate of the contour line corresponding to the inner surface group is used directly, denoted as P2. Find the vertical connection point between P1 and P2 on the outer side, and connect them vertically and horizontally to complete the missing outer contour line.
[0016] The present invention provides a method for extracting the outline of a blank for machining a three-dimensional volute model on the surface of revolution. This method has the following advantages: starting from the topological and geometric properties of the surface of revolution of the volute model, various features of the surface of revolution of the volute can be identified relatively accurately, and it has a certain degree of generalization. Attached Figure Description
[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.
[0018] Figure 1 The flowchart illustrates the method for extracting the outline of a blank during the turning of a three-dimensional volute model, as provided in this invention.
[0019] Figure 2 This is a schematic diagram illustrating the division of the upper reference surface, inner surface group, lower reference surface, and outer surface group in the three-dimensional volute model provided by the present invention.
[0020] Figure 3A and Figure 3B This is a schematic diagram for obtaining a certain intersecting line provided by the present invention.
[0021] Figure 4 This is a schematic diagram for obtaining a certain contour line provided by the present invention.
[0022] Figure 5A This is a schematic diagram of obtaining the first type of closed wireframe provided by the present invention.
[0023] Figure 5B This is a schematic diagram of obtaining a second type of closed wireframe provided by the present invention.
[0024] Figure 6A for Figure 5A A schematic diagram of the machining blank corresponding to the first type of closed wireframe.
[0025] Figure 6B for Figure 5B A schematic diagram of the machining blank corresponding to the second type of closed wireframe.
[0026] Figure 7 This is a schematic diagram of the contour line extraction for Example 1 of the three-dimensional volute model provided by the present invention.
[0027] Figure 8 This is a schematic diagram of the contour line extraction for Example 2 of the three-dimensional volute model provided by the present invention.
[0028] Figure 9 This is a schematic diagram of the contour line extraction for Example 3 of the three-dimensional volute model provided by the present invention.
[0029] Figure 10 This is a schematic diagram of the contour line extraction for Example 4 of the three-dimensional volute model provided by the present invention. Detailed Implementation
[0030] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a method for extracting the outline of a blank during turning of a three-dimensional volute model according to the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.
[0031] This embodiment provides a method for extracting the contour lines of a blank during the turning of a three-dimensional volute model, such as... Figure 1 As shown, the method for extracting the contour lines of the blank during the turning of the three-dimensional volute model includes the following steps: Step S1: Input the three-dimensional volute model and extract all turning surfaces from the three-dimensional volute model; It should be noted that all turning surfaces are obtained through the 3D volute model and the index of the turning surfaces.
[0032] Preferably, such as Figure 2 As shown, the extraction of all turning surfaces from the three-dimensional volute model includes: In all the turning surfaces of the three-dimensional volute model, the horizontal plane with the highest coordinate value in the axial direction is defined as the upper reference plane, and the horizontal plane with the lowest coordinate value in the axial direction is defined as the lower reference plane. Based on the connection relationship of all turning surfaces in the adjacent node diagram, the turning surfaces connected to the outside of the upper reference plane (or the upper and lower reference planes if there is a lower reference plane) are used as the boundary. The turning surfaces connected to the inside of the upper reference plane are defined as the outer surface group, and the turning surfaces connected to the inside of the upper reference plane are defined as the inner surface group. Among all the turning surfaces of the three-dimensional volute model, there must be at least an upper reference surface or a lower reference surface. If there is a lower reference surface but no upper reference surface, the three-dimensional volute model or the rotating shaft is rotated 180° to ensure that the upper reference surface exists.
[0033] Step S2: Traverse each turning surface, take multiple scattered points on the edge of each turning surface, select the scattered point farthest from the axis of rotation, and construct a plane through the farthest scattered point and the axis of rotation. Then intersect the constructed plane with the corresponding turning surface to obtain the intersection line corresponding to each turning surface. Preferably, step S2 includes: Store the intersection lines corresponding to each turning face into an intersection line list; When the connection between the turning surfaces in the inner side group and / or the turning surfaces in the outer side group is interrupted, multiple lists of intersecting lines are used for storage.
[0034] In this embodiment of the invention, if there is a turning surface such as Figure 3A As shown, the radius corresponding to the maximum rotation profile of the turning surface is selected at the four corner points of a rectangle; as... Figure 3B As shown, in practice, it is necessary to take scattered points on the side of the rectangle, take the scattered point farthest from the axis, construct a plane through the axis of rotation and the farthest scattered point, and intersect the turning surface with the constructed plane to obtain the corresponding intersection line.
[0035] Step S3: Since the positions of the intersecting lines corresponding to each turning surface are not fixed and the risk of coplanarity is high, each intersecting line is swept 360 degrees around the rotation axis to obtain the corresponding swept toroidal surface. The same reference plane (preset as XOZ plane, where Z is the direction of the rotation axis) is used to intersect with each swept toroidal surface to obtain the contour line of each swept toroidal surface on the same reference plane. In embodiments of the present invention, such as Figure 4 As shown, for a model that is symmetrical in the sense of rotational transformation (i.e., without convex or concave parts), its contour line can be obtained by intersecting it with any reference plane.
[0036] Preferably, step S3 includes: Store the contour lines of each swept torus on the same reference plane in a contour line list.
[0037] Step S4: Remove duplicates and sort all contour lines; It should be noted that the contour list L, which stores all contours, contains many completely overlapping contours. These overlapping contours arise because equivalent surface structures, under rotational meaning, undergo a sweep-intersection operation, resulting in identical contours. For example, a sidewall has several protrusions that are equivalent in rotational projection mapping. That is, given a rotational projection transformation T, for a contour C in image space, these protrusions belong to the set of all preimages mapped to contour C. After an axis-sweep-intersection operation, several overlapping contours C are generated, requiring deduplication. Simultaneously, some structures may produce partially overlapping but different contours, such as one long and one short contour. The longer contour covers the shorter one, so the shorter contour needs to be removed.
[0038] Preferably, step S4 includes: Step S41: Create a first list L1 and a second list L2; Step S42: Traverse the contour lines in the contour line list L and compare them with the contour lines in the first list L1; wherein, firstly, select the currently traversed contour line 1 in the contour line list L, and determine whether there is a contour line in the first list L1 that completely overlaps with the contour line 1. If there is, then no processing is done on the contour line 1; if not, then the contour line 1 is added to the first list L1; then, the other contour lines in the contour line list L are sequentially compared with the contour lines in the first list L1 to update the first list L1; Specifically, determining whether there exists a contour line in the first list L1 that completely coincides with the contour line 1 includes: Obtain the start point S1 and end point E1 of the contour line 1 in the contour line list L, and obtain the start point S2 and end point E2 of a certain contour line in the first list L1. If the following conditions are met: "the distance between the starting point S1 and the starting point S2 is less than the tolerance value (default is 0.01mm), and the distance between the ending point E1 and the ending point E2 is less than the tolerance value", or "the distance between the starting point S1 and the ending point E2 is less than the tolerance value, and the distance between the ending point E1 and the starting point S2 is less than the tolerance value", then it is determined that there is a contour line in the first list L1 that completely overlaps with the contour line 1. The reason for cross-comparison of the starting point and the ending point is that the contour line obtained by sweep-intersection may have an uncertain direction, so the direction from the starting point to the ending point of the obtained contour line is uncertain, and cross-verification is required.
[0039] If the contour line 1 in the contour line list L does not meet the above conditions with any of the contour lines in the first list L1, then it is determined that there is no contour line in the first list L1 that completely overlaps with the contour line 1.
[0040] Step S43: Traverse the contour lines in the first list L1 and compare them with the contour lines in the second list L2; wherein, firstly, select the contour line 2 currently traversed in the first list L1, and determine whether there is a contour line in the second list L2 that partially overlaps with the contour line 2. If there is, then the contour line 2 is not processed; if there is not, then the contour line 2 is added to the second list L2; then, the other contour lines in the first list L1 are compared with the contour lines in the second list L2 in turn to update the second list L2; Specifically, determining whether there exists a contour line in the second list L2 that partially overlaps with the contour line 2 includes: Obtain the midpoint M1 of the contour line 2 in the first list L1, and obtain a certain contour line in the second list L2, and calculate the distance between the midpoint M1 of the contour line 2 and the certain contour line in the second list L2. If the distance is less than the tolerance value, it is determined that there is a contour line in the second list L2 that partially overlaps with the contour line 2. It can be considered that a longer contour line covers the shorter contour line. Specifically, when the length of the contour line 2 is greater than the partially overlapping contour line in the second list L2, the partially overlapping contour line in the second list L2 is replaced with the contour line 2. When the length of the contour line 2 is not greater than the partially overlapping contour line in the second list L2, the contour line 2 is not processed. If the distance is not less than the tolerance value, it is determined that there is no contour line in the second list L2 that partially overlaps with the contour line 2.
[0041] Step S44: Output the final updated second list L2 (the contour lines in the second list L2 do not overlap). In the ACIS engine, sort all the contour lines in the final updated second list L2 in the order of contour lines corresponding to the upper reference plane -> contour lines corresponding to the inner surface group -> contour lines corresponding to the lower reference plane -> contour lines corresponding to the outer surface group to obtain the sorted second list L2.
[0042] Specifically, step S44 includes: The contour lines corresponding to the inner side surface group are sorted by axial height from high to low; The contour lines corresponding to the outer surface group are sorted by axial height from low to high.
[0043] Step S5: Connect the sorted outlines to obtain a closed wireframe; Preferably, step S5 includes: The sorted outlines are connected to form an initial wireframe; if the initial wireframe is incomplete, it is completed to obtain the closed wireframe. Wherein, when the inner contour line corresponding to the inner side group of the initial wireframe is missing, a straight line is used to fill in the missing inner contour line; Specifically, when the outer contour line corresponding to the outer side group of the initial wireframe is missing, the missing outer contour line is filled in.
[0044] It should be noted that for each face group, its contour line on the reference plane can be obtained; the contour lines corresponding to each face group are connected in the order of upper reference plane -> inner face group -> lower reference plane -> outer face group; then the segmented contour lines are supplemented to form a closed directed wireframe or planar solid.
[0045] Specifically, the step of completing the missing outer contour line when the outer contour line corresponding to the outer side group of the initial wireframe is missing includes: If the upper reference plane has no outer surface group, the outermost coordinate of the contour line corresponding to the upper reference plane is used, denoted as P1; if the upper reference plane has an outer surface group, the outermost coordinate of the contour line corresponding to the outer surface group is used, denoted as P1. If the lower reference plane has no outer surface group, the outermost coordinate of the contour line corresponding to the lower reference plane is used, denoted as P2; if the lower reference plane has an outer surface group, the outermost coordinate of the contour line corresponding to the outer surface group is used, denoted as P2; if there is no lower reference plane and no outer surface group connected to the lower reference plane, the lowest coordinate of the contour line corresponding to the inner surface group is used directly, denoted as P2. Find the vertical connection point between P1 and P2 on the outer side, and connect them vertically and horizontally to complete the missing outer contour line.
[0046] In embodiments of the present invention, such as Figure 5A As shown, the left side is the inner contour line, and the several diagonal lines on the left side are the straight lines directly constructed between the inner contour line groups. The right side is the outer contour line. This model has an upper reference plane, but no lower reference plane and an outer surface group connected to the lower reference plane. Therefore, the lowest point of the inner surface group in the axial direction is directly connected to the outermost point of the upper reference plane in a vertical-horizontal manner to form a closed wireframe.
[0047] In embodiments of the present invention, such as Figure 5B As shown, the left side is the inner contour line, and the several diagonal lines on the left side are the straight lines directly constructed between the inner line groups. The right side is the outer contour line. This model has an upper reference plane and a lower reference plane. The two highest and lowest straight lines perpendicular to the rotation axis are the contour lines corresponding to the upper and lower reference planes. Construct straight lines to connect the unconnected parts to form a closed wireframe.
[0048] Step S6: Sweep the closed wireframe around the axis of rotation to form the machining blank of the three-dimensional volute model, such as... Figures 6A-6B As shown, In this embodiment of the invention, the contour line extraction process for four three-dimensional volute model examples is as follows: Figures 7-10 As shown.
[0049] The method for extracting the blank contour line of the turning surface of a three-dimensional volute model provided by this invention is particularly suitable for CNC turning process planning and machining path generation of complex curved surface turning parts such as volutes. Starting from the topological and geometric properties of the turning surface features of the volute model, various features of the volute turning surface can be identified relatively accurately, and it has a certain degree of generalization.
[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for extracting the contour lines of a blank during the turning of a three-dimensional volute model, characterized in that, The method for extracting the contour lines of the blank during the turning of the three-dimensional volute model includes the following steps: Step S1: Input the three-dimensional volute model and extract all turning surfaces from the three-dimensional volute model; Step S2: Traverse each turning surface, take multiple scattered points on the edge of each turning surface, select the scattered point farthest from the axis of rotation, and construct a plane through the farthest scattered point and the axis of rotation. Then intersect the constructed plane with the corresponding turning surface to obtain the intersection line corresponding to each turning surface. Step S3: Sweep each intersecting line around the rotation axis to obtain the corresponding swept toroidal surface, and use the same reference plane to intersect each swept toroidal surface to obtain the contour line of each swept toroidal surface on the same reference plane. Step S4: Remove duplicates and sort all contour lines; Step S5: Connect the sorted outlines to obtain a closed wireframe; Step S6: Sweep the closed wireframe around the axis of rotation to form the machining blank of the three-dimensional volute model.
2. The method for extracting the contour line of a blank processed by turning a three-dimensional volute model according to claim 1, characterized in that, The extraction of all turning surfaces from the three-dimensional volute model includes: In all the turning surfaces of the three-dimensional volute model, the horizontal plane with the highest coordinate value in the axial direction is defined as the upper reference plane, and the horizontal plane with the lowest coordinate value in the axial direction is defined as the lower reference plane. Based on the connection relationship of all turning surfaces in the adjacent node diagram, the turning surface group connected to the outside of the upper reference plane is defined as the outer surface group, and the turning surface group connected to the inside of the upper reference plane is defined as the inner surface group. Among all the turning surfaces of the three-dimensional volute model, there must be at least an upper reference surface or a lower reference surface. If there is a lower reference surface but no upper reference surface, the three-dimensional volute model or the rotating shaft is rotated 180° to ensure that the upper reference surface exists.
3. The method for extracting the contour line of a blank during turning of a three-dimensional volute model according to claim 2, characterized in that, Step S2 includes: Store the intersection lines corresponding to each turning face into an intersection line list; When the connection between the turning surfaces in the inner side group and / or the turning surfaces in the outer side group is interrupted, multiple lists of intersecting lines are used for storage.
4. The method for extracting the contour line of a blank during turning of a three-dimensional volute model according to claim 1, characterized in that, Step S3 includes: Store the contour lines of each swept torus on the same reference plane into a contour line list.
5. The method for extracting the contour line of a blank processed by turning a three-dimensional volute model according to claim 4, characterized in that, Step S4 includes: Step S41: Create a first list L1 and a second list L2; Step S42: Traverse the contour lines in the contour line list L and compare them with the contour lines in the first list L1; wherein, firstly, select the currently traversed contour line 1 in the contour line list L, and determine whether there is a contour line in the first list L1 that completely overlaps with the contour line 1. If there is, then no processing is done on the contour line 1; if not, then the contour line 1 is added to the first list L1; then, the other contour lines in the contour line list L are sequentially compared with the contour lines in the first list L1 to update the first list L1; Step S43: Traverse the contour lines in the first list L1 and compare them with the contour lines in the second list L2; wherein, firstly, select the contour line 2 currently traversed in the first list L1, and determine whether there is a contour line in the second list L2 that partially overlaps with the contour line 2. If there is, then the contour line 2 is not processed; if there is not, then the contour line 2 is added to the second list L2; then, the other contour lines in the first list L1 are compared with the contour lines in the second list L2 in turn to update the second list L2; Step S44: Output the final updated second list L2. Sort all the contour lines in the final updated second list L2 according to the order of contour lines corresponding to the upper reference plane -> contour lines corresponding to the inner surface group -> contour lines corresponding to the lower reference plane -> contour lines corresponding to the outer surface group to obtain the sorted second list L2.
6. The method for extracting the contour line of a blank during turning of a three-dimensional volute model according to claim 5, characterized in that, The determination of whether there is a contour line in the first list L1 that completely coincides with the contour line 1 includes: Obtain the start point S1 and end point E1 of the contour line 1 in the contour line list L, and obtain the start point S2 and end point E2 of a certain contour line in the first list L1. If the following conditions are met: "the distance between the starting point S1 and the starting point S2 is less than the tolerance value, and the distance between the ending point E1 and the ending point E2 is less than the tolerance value", or "the distance between the starting point S1 and the ending point E2 is less than the tolerance value, and the distance between the ending point E1 and the starting point S2 is less than the tolerance value", then it is determined that there is a contour line in the first list L1 that completely overlaps with the contour line 1. If the contour line 1 in the contour line list L does not meet the above conditions with any of the contour lines in the first list L1, then it is determined that there is no contour line in the first list L1 that completely overlaps with the contour line 1.
7. The method for extracting the contour line of a blank during turning of a three-dimensional volute model according to claim 5, characterized in that, The step of determining whether there is a contour line in the second list L2 that partially overlaps with the contour line 2 includes: Obtain the midpoint M1 of the contour line 2 in the first list L1, and obtain a certain contour line in the second list L2, and calculate the distance between the midpoint M1 of the contour line 2 and the certain contour line in the second list L2. If the distance is less than the tolerance value, it is determined that there is a contour line in the second list L2 that partially overlaps with the contour line 2; wherein, when the length of the contour line 2 is greater than the partially overlapping contour line in the second list L2, the partially overlapping contour line in the second list L2 is replaced with the contour line 2; when the length of the contour line 2 is not greater than the partially overlapping contour line in the second list L2, the contour line 2 is not processed. If the distance is not less than the tolerance value, it is determined that there is no contour line in the second list L2 that partially overlaps with the contour line 2.
8. The method for extracting the contour line of a blank processed by turning a three-dimensional volute model according to claim 5, characterized in that, Step S44 includes: The contour lines corresponding to the inner side surface group are sorted by axial height from high to low; The contour lines corresponding to the outer surface group are sorted by axial height from low to high.
9. The method for extracting the contour line of a blank during turning of a three-dimensional volute model according to claim 8, characterized in that, Step S5 includes: The sorted outlines are connected to form an initial wireframe; if the initial wireframe is incomplete, it is completed to obtain the closed wireframe. Wherein, when the inner contour line corresponding to the inner side group of the initial wireframe is missing, a straight line is used to fill in the missing inner contour line; Specifically, when the outer contour line corresponding to the outer side group of the initial wireframe is missing, the missing outer contour line is filled in.
10. The method for extracting the contour line of a blank processed by turning a three-dimensional volute model according to claim 9, characterized in that, The process of completing the missing outer contour line when the outer contour line corresponding to the outer side group of the initial wireframe is missing includes: If the upper reference plane has no outer surface group, the outermost coordinate of the contour line corresponding to the upper reference plane is used, denoted as P1; if the upper reference plane has an outer surface group, the outermost coordinate of the contour line corresponding to the outer surface group is used, denoted as P1. If the lower reference plane has no outer surface group, the outermost coordinate of the contour line corresponding to the lower reference plane is used, denoted as P2; if the lower reference plane has an outer surface group, the outermost coordinate of the contour line corresponding to the outer surface group is used, denoted as P2; if there is no lower reference plane and no outer surface group connected to the lower reference plane, the lowest coordinate of the contour line corresponding to the inner surface group is used directly, denoted as P2. Find the vertical connection point between P1 and P2 on the outer side, and connect them vertically and horizontally to complete the missing outer contour line.