A method for obtaining the unfolded drawing of rolling lines for rolled parts with special cross-sections

Abstract

The invention discloses a method for obtaining a rolling line expansion diagram of a special-shaped cross-section rolled part, comprising the following steps: establishing a section position diagram of an upper and lower cross-section of a rolled part, using AutoCAD software to establish a section position diagram of an elbow design; creating a coordinate table of upper and lower cross-section lines of the rolled part, creating an Excel file of S4 and S5 cross-section line coordinate tables, inserting and simplifying the Excel file to form a single-section plane diagram; inputting coordinates into a graphic to generate upper and lower cross-section curves, arranging points on the single-section plane diagram, and generating a three-dimensional diagram of upper and lower cross-section curves; establishing a ruled surface model, establishing an S4-S5 section surface model; unfolding the surface model into a plane; extracting rolling line coordinates and inserting the expansion diagram, extracting the rolling line coordinates in CAD software, editing in Excel software and then inserting the graphic; the method for obtaining a rolling line expansion diagram of a special-shaped cross-section rolled part is suitable for all cross-sectional shapes, irregular three-dimensional space modeling, and expandable complex roll-formed plate parts, and also includes cross-sectional sheet metal parts formed by standard geometric curves.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical manufacturing sheet metal processing, and in particular to a lofting method for obtaining a rolling line development diagram of a special-section rolled part. Background Art

[0002] Parts made of plates with consistent thickness through cold working technology are generally called sheet metal parts. Common forming methods include: stamping, bending, rolling, etc. Cylinder parts made of medium-thick plates through rolling are widely used, and are often used in connecting pipes in industry and construction, such as penstocks, steel bifurcated pipes, turbine volutes, elbow pipes, etc. in hydropower stations.

[0003] Conditions for use of bending forming: This operation can only be completed when the two "section profile" lines are standard curves such as straight lines, arcs, or elliptical lines. If the "section profile" line is a spline curve, or an irregular curve such as an adjusted approximate arc, elliptical line, or polyline, the "sheet metal lofting" command will not be able to establish a 3D model. In addition, the "lofting" command in the "3D model" section of the menu bar of the basic operation interface of Autodesk inventor software can select more than two arbitrary curves (not in the same plane) to establish a surface model, and convert it into a sheet metal part through "thickening / offset", and you can also get a plane unfolding view. However, the unfolding view obtained by the "lofting" command does not have rolling lines.

[0004] Invention patent CN201510212604.7 proposes an operation method for generating lofting coordinates by unfolding steel bifurcations, volutes and elbows based on 3D modeling with Autodesk inventor software. The operation is completed by: ① establishing a 2D sketch → ② establishing a 3D surface → ③ trimming → ④ thickening → ⑤ unfolding → ⑥ extracting lofting coordinates. Its main feature is that in the unfolded state, by arranging small process holes in equal numbers on the upper and lower section contour lines, the process hole coordinates are extracted and tabulated in the engineering drawing environment.

[0005] It should be pointed out that the straight line formed by connecting the points of equal division of the length of the upper and lower section unfolding lines is consistent with the position of the V-line of the three-dimensional model only in special cases such as standard section shape and the position of the right cone, and can be used as a rolling line. It is not applicable to complex rolled parts with special-shaped sections. When the three-dimensional model is displayed in a three-dimensional wireframe, the "V-line" can be automatically displayed. By setting the number of "V-lines" on the surface, it can be fully used as a rolling line during rolling. The difficulty lies in how to extract the position parameters of the "V-line" so that it can be marked in the unfolded drawing. AutoCAD software has a "lofting" command in the "3D production" menu of the "3D modeling" workspace, which can display the "U-line and V-line" of the rolled part model. As of the AutoCAD 2020 version, there is no "expand" command, and plane unfolding cannot be performed.

[0006] The existing sheet metal unfolding programs (sheet metal unfolding and blanking software) on the Internet can only be used for the layout of conventional sheet metal parts, such as arbitrary angle elbows, tees, reducing tees, Y-shaped tees, eccentric round top and square bottom, square top and round bottom, eccentric rectangular square cone, flat-mouthed centered circular cone, cone, etc. It cannot be used for complex three-dimensional rolled parts composed of special-shaped sections.

[0007] The methods of pattern development and opening adopted in the prior art include: drawing method, mathematical formula calculation method, software programming method, 3D software modeling and development method, etc. Among them, the 3D modeling and development method has become a development trend and is in the development and exploration stage. For complex three-dimensional rolled parts composed of special-shaped cross-sections, there is currently no generally recognized modeling and development method based on commonly used software. Summary of the invention

[0008] The purpose of the present invention is to solve the above-mentioned problem and to provide a layout method for obtaining the unfolded diagram of the rolling line of the special-shaped cross-section rolled parts. According to the operating method of the present invention, the unfolded diagram of the complex rolled parts with special-shaped cross-sections can be accurately obtained together with the rolling line parameter information. The graphics are connected to the control program of the CNC cutting machine, and the material can be directly cut on the steel plate; and the rolling line coordinates during rolling are provided. The CNC cutting machine can automatically mark the lines with ink to guide the arc pressing and rounding process of the plate rolling machine; the alignment and docking of the arc rolling, rounding and assembly processes in the manufacturing process are easier to control, thereby improving product quality, saving production time and improving labor efficiency.

[0009] To achieve the above object, the technical solution of the present invention is: a method for obtaining a layout of a rolled part with a special-shaped cross-section with a rolling line development diagram, comprising the following steps:

[0010] S1: Establish the segmented position diagram of the upper and lower sections of the rolled part, and use AutoCAD software to establish the segmented position diagram of the elbow design;

[0011] S2: Create the coordinate table of the upper and lower cross-section lines of the rolled part, and create the Excel file of the coordinate table of the cross-section lines of S4 and S5, insert it, and simplify it to form a single-section plane drawing;

[0012] S3: Graphically input coordinates, generate upper and lower section curves, arrange points on a single section plane, and generate a three-dimensional diagram of the upper and lower section curves;

[0013] S4: Establish a ruled surface model and establish a S4-S5 section surface model;

[0014] S5: The surface model is unfolded into a plane;

[0015] S6: Extract the rolling line coordinates and insert them into the development drawing. Extract the rolling line coordinates in the CAD software, edit them in Excel software and then insert them into the drawing.

[0016] Preferably, in S1, the segmented positions of the elbow tube design are accurately transplanted into CAD and used as a two-dimensional basic sketch for lofting, which includes the segmented positions of all segments, so as to facilitate the subsequent use of segment-by-section expansion.

[0017] Preferably, for easy viewing in S2, use the copy command and "paste" it into the "elbow pipe design section position" of S1 under the CAD "Edit" menu, draw the corresponding cross-sectional shape diagram, delete other redundant parts such as the section position lines, and form a complete drawing and save it as "S4-S5 section plan view".

[0018] Preferably, S3 includes the following four steps:

[0019] S3.1: Draw auxiliary lines;

[0020] S3.2: Specify the midpoint of the S4 section line as the origin, the upper right end of the S4 section line as the x-axis direction, and the front end of the auxiliary line as the y-axis direction to establish the S4 section coordinate system;

[0021] S3.3: Draw the 1 / 2 lofting curve of S4 section;

[0022] S3.4: Repeat the above steps and draw the 1 / 2 lofting curve of S5 section.

[0023] Preferably, S4 includes the following two steps:

[0024] S4.1: Start Rhino 7 software and generate a surface model through Rhino 7 software;

[0025] S4.2: Project auxiliary lines on the surface to locate the V-line position.

[0026] Preferably, S5 includes the following two steps:

[0027] S5.1: The surface model of Section S4-S5 is developed together with the projection lines;

[0028] S5.2: Draw a V-shaped line on the development diagram.

[0029] Preferably, S6 includes the following three steps:

[0030] S6.1: The expanded view is simplified and adjusted to the XY plane of the world coordinate system;

[0031] S6.2: Points and numbering at both ends of the rolling line;

[0032] S6.3: Extract the point coordinates and insert the list into the graph.

[0033] Compared with the prior art, the present invention has the following beneficial effects: the position and number of the rolling lines marked on the unfolded view are completely consistent with the V-line of the ruled surface of the three-dimensional model, and the number of rolling lines can be freely increased or decreased as needed. The rolling line obtained in this way is the side mother line after the plate is rolled. This greatly facilitates the manufacturing process: the division of rolled tiles of single-section large-scale rolled parts, the ordering of steel plate layout, the trimming and docking of plates, the spraying of the rolling lines of CNC cutting machines, the arc pressing and rounding during the rolling of the plate rolling machine, and the inspection and measurement during the assembly and installation process. By providing accurate drawing data, unnecessary material waste is avoided, the difficulty of arc rolling is reduced, manufacturing time is saved, and manufacturing quality and production efficiency are improved;

[0034] It should be noted that this method is suitable for all cross-sectional shapes, irregular three-dimensional shapes, and expandable complex roll-formed plate parts, including cross-sectional sheet metal parts formed by standard geometric curves;

[0035] The patent of this invention fully considers the manufacturing process requirements during three-dimensional modeling and unfolding and provides the rolling line coordinate table information completely on the unfolded drawing, providing direct guidance and standard basis for manufacturing processing, facilitating subsequent rolling and assembly processes, and ensuring that quality control during manufacturing is easier to achieve, thus having innovative and practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a flow chart showing the operation of the sample.

[0037] Figure 2 It is a segmented position diagram of the elbow tube design of the present invention.

[0038] Figure 3 This is the plan view of section S4-S5 of the present invention.

[0039] Figure 4 This is a cross-sectional curve diagram of section S4-S5 of the present invention.

[0040] Figure 5 This is the surface model diagram of section S4-S5 of the present invention.

[0041] Figure 6 This is a V-line position diagram for projecting auxiliary lines on a curved surface according to the present invention.

[0042] Figure 7 The S4-S5 section surface model is developed for the present invention and a V element line diagram is drawn.

[0043] Figure 8 This is the coordinate expansion diagram of the rolling line of the S4-S5 section of the present invention. DETAILED DESCRIPTION

[0044] The present invention will now be described in further detail with reference to the accompanying drawings. The accompanying drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and thus only show the components related to the present invention.

[0045] For example, please refer to Figure 1-8 A method for obtaining a layout of a rolled part with a special-shaped cross-section with a rolling line expansion diagram. Taking the expansion of the elbow S4-S5 section as an example, the operation process includes at least the following steps:

[0046] S1: Establish the upper and lower section position diagram of the rolled part.

[0047] Use AutoCAD software to create the elbow design segmentation position diagram: Open AutoCAD 2007 software, select a metric template that is consistent with the design drawing unit, create the first file Drawing1.dwg, and save it as "Elbow Design Segmentation Position". In the basic operation interface X, Y viewport, use the corresponding line type and command to accurately draw the 1:1 segmentation position line of the design elbow, that is, the side view of the elbow installation position is as follows Figure 2 As shown. And mark the corresponding sections S1-S12.

[0048] Step description: The key point of this step is to accurately transfer the segmented position of the elbow design to CAD as a two-dimensional basic sketch for lofting. It includes all segmented positions for easy use in subsequent segment-by-section expansion.

[0049] S2: Create the coordinate table of the upper and lower section lines of the rolled part.

[0050] Create an Excel file of the S4 and S5 section line coordinate table, insert it, and simplify it to form a single section plan: Open Excel software, create a new table file, and name it "S4, S5 section 1 / 4 coordinate.xlsx". Express the X and Y coordinates of the quarter of the S4 and S5 sections of the elbow design drawing in a list, add a new column (X, Y) after the Y column, and use the Excel software data reference formula: =x column row number &", "&y column row number, and automatically introduce the data entered in the first X column and Y column into the (X, Y) column for synthetic position coordinates for standby use.

[0051] For easy viewing, use the copy command and "paste" to the CAD "Edit" menu. Figure 3 Draw the corresponding cross-sectional shape diagram, delete the redundant parts such as other node position lines, and save the complete figure as "S4-S5 section plan" (see Figure 3 ).

[0052] S3: Graphically input coordinates and generate upper and lower section curves.

[0053] Arrange points on a single-section plane diagram to generate a three-dimensional diagram of the upper and lower section curves.

[0054] S3.1: Open the "S4-S5 Section Plan" file again, and draw a 1000mm long straight line as an auxiliary line, starting from the midpoint of the S4 section line and perpendicular to the x and y planes.

[0055] S3.2: Open the "View" menu on the CAD operation interface, select the "Free Dynamic Observation" command in the "Dynamic Observation" secondary menu, and rotate the "S4-S5 Section Plan" to the axial direction for three-dimensional observation. Open the "Tools" menu, select the "Three Points" command in the "New UCS" secondary menu, specify the midpoint of the S4 section line as the origin, the upper right end of the S4 section line as the x-axis, and the front end of the auxiliary line as the y-axis to establish the S4 section coordinate system; click the "Tools" menu again, select the "Name UCS" command, and in the pop-up dialog box, change "Current UCS Unnamed" to "S4 Section" and set it as the current coordinate system.

[0056] S3.3: Open the "S4, S5 Section 1 / 4 Coordinates.xlsx" file, copy all the coordinate values ​​in the "x, y" column in the coordinate table; open the "Draw" menu in the CAD operation interface menu bar, select the "Multi-point" command in the "Point" secondary menu, right-click and paste in the "Command Line", and the 1 / 4 coordinate point on the S4 section is automatically generated; use the "Mirror" command to symmetric to the 4th quadrant, and symmetric the two nearest points on the right side of the x-axis in the 2nd and 3rd quadrants; click the "Spline Curve" command, pick up the points on and to the right of the x-axis, and produce the 1 / 2 curve on the S4 section. The two points on the left side of the x-axis are only used as tangent direction points at the start and end of the spline curve, and the curve is not drawn.

[0057] Because the neutral layer is at 1 / 2 of the plate thickness during roll forming, the inner diameter section curve obtained needs to be offset to the outside by 1 / 2 of the plate thickness using the "offset" command to form the section lofting curve. At this point, the 1 / 2 lofting curve of the S4 section is completed.

[0058] S3.4: Repeat the above steps to draw the 1 / 2 lofting curve of the S5 section. Delete unnecessary content and save it as a three-dimensional diagram of the "S4-S5 section curve" (see Figure 4 ).

[0059] Steps: After starting "Spline", paste x, y coordinates in the command line to directly generate a curve, but there is no adjacent point outside the curve to specify the tangent direction, which affects the curve shape. When using it, you need to arrange the tangent points at both ends of the drawn curve in advance; you can also use the "Image" command to arrange the coordinate points on the entire section, draw a closed spline curve, and then use the "Trim" command to cut off half to form a 1 / 2 curve of the section.

[0060] S4: Establish a ruled surface model and establish the S4-S5 section surface model.

[0061] S 4.1: Start Rhino 7 software: Click the "Open" command in the "File" drop-down menu on the menu bar of the operation interface, and select the "S4-S5 Section Curve" graphic to open. In the pop-up "DWG / DXF Import Options" card, select "Bidirectional Accuracy" for grid accuracy (others are default), and then click "OK" to import the CAD drawing into the software. Then select the "Surface Tools" section under the "Command" line, select the "Loft" command in the pop-up left toolbar, select the S4-S5 section curve in turn, and press the "Enter" key to complete. The pop-up "Loft Options" card: select "Straight Segment" for style, click the "Split at Tangent Point" option, enter "19" for the number of reconstruction points, and click "OK" for other options to generate a surface model by default (see Figure 5 ).

[0062] Step description: The "Reconstruction Points" in the option card is determined by the number of rolling lines required. The more points, the more precise but the more work to do. When the odd number "3+2X" is selected, the side mother line on the Y axis of the lofted pipe segment is displayed, which is conducive to alignment during rolling and assembly. It should be noted that the actual number of V-line lines displayed in the model is "points-2".

[0063] S 4.2: Project auxiliary lines on the surface to locate the V-line position: Open the "Standard" section in the "Horizontal Toolbar" under the "Command" line of the Rhino 7 operation interface. Select the "Multiple Lines" command on the left toolbar, and draw continuous jagged lines at both ends of each V-line in the "S4-S5 Section Surface Model". The "×"-shaped diagonal lines between the surface V-lines are easy to identify (see Figure 6 ).

[0064] Select the "Project Curve or Control Point" command on the left toolbar again, and in the command options: select "Relax (L) = No, Delete Input (D) = Yes, Destination Layer (O) = Current, Direction (I) = Work Plane Z"; click the auxiliary line and press the "Enter" key, select the surface to be projected and press the "Enter" key to end. Project the auxiliary line on the surface and locate the V line position--the operation steps are completed.

[0065] S5: The surface model is unfolded into a plane.

[0066] S5.1: The surface model of Section S4-S5 is unfolded together with the projection lines.

[0067] In the Rhino 7 interface, open the "Surface Tools" section in the "Horizontal Toolbar" under the "Command" line. Click the "Flatten Expandable Surface" command, and select the options: "Explode (E) = No, Keep Properties (K) = Yes, Relative Tolerance (R) = 0.01, Warning (W)", then select the projection line and surface and press the "Enter" key to confirm. The software automatically unfolds the "S4-S5 Section Surface" to the x, y coordinate plane (see Figure 7 ), the pink projection line is an arc-shaped sawtooth line. The corresponding position of the vertex of the "diamond" formed by the intersection of the two sawtooth lines is the end point of the V element line of the surface model. Connect the two "vertices" to get the V element line on the surface model. The S4 section unfolding curve is labeled ③, the S5 section unfolding curve is labeled ①, and the straight line generated between the two section unfolding curves is the "surface construction line" generated by the software system by default. Through measurement, it can be proved that the surface model generated in the "straight section" style of the "lofting" command of the Rhino 7 software is unfolded by the "flatten expandable surface" command to obtain the "surface construction line" in the plane view. The direction is consistent with the V element line of the surface model, and can be used as the rolling line of the roll-formed sheet metal.

[0068] S5.2: Draw a V-shaped line on the development diagram.

[0069] In the Rhino 7 operation interface, open the "Standard" section in the "Horizontal Toolbar" under the "Command" line. Select the "Single Line" command in the left toolbar, capture the "Intersection Point" to connect the vertices of the projection line "diamond", and draw all V lines on the unfolded contour. Select the unfolded view and open the "Properties" button in the right toolbar: Remove the √ in the □ after "Show Surface Construction Lines" under "Construction Line Density". Then delete the projection lines and surface models on the unfolded view, and you can get the S4-S5 section unfolded view (with V lines). Save it as a "S4-S5 Section Exploded View (.dwg format)" file through the "Save As" command in the "File" menu.

[0070] S6: Extract rolling line coordinates and insert them into the development diagram.

[0071] Extract the rolling line coordinates in the CAD software, edit them in Excel software and insert them into the graphics.

[0072] Rhino software is highly compatible with Auto CAD software. Graphics drawn with Rhino software can be saved as Auto CAD Drawing (.*dwg) format files and then opened and edited with the corresponding version of Auto CAD software. The following is an explanation using the expanded diagram of Section S4-S5.

[0073] S6.1: The expanded view is simplified and adjusted to the XY plane of the world coordinate system.

[0074] Open the Auto CAD software to enter the basic operation interface, click the "File" menu in the upper left corner of the screen → "Open" command in the drop-down menu, and select the saved S4-S5 section expansion drawing (.dwg format) file in the pop-up dialog box to open. First, simplify the view, delete unnecessary graphics and lines, and only keep the expansion drawing with rolling lines. Set the plane where the expansion drawing is located as the current view, select "Name UCS" in the "Tools" menu, set "World Coordinate System W" to "Current" and click "OK"; use the "Move" command to move the lower left corner of the expansion drawing to the coordinate origin (0,0,0); use the "Rotate" command to set the long side straight line of the expansion drawing to the Y axis, and the horizontal direction on the right side of the Y axis at 90° is the X axis. The coordinate system adjustment of the expansion drawing is completed.

[0075] S6.2: The ends of the rolling line shall be numbered and points shall be arranged.

[0076] On the Auto CAD operation interface, click the "Format" menu in the menu bar → the "Point Style" command in the pop-up drop-down menu → set an easily recognizable "point" style such as the "0+×" symbol, etc.; then click the "Draw" menu in the menu bar → the "Point" command in the pop-up drop-down menu → select "Multiple Points" to place points on the intersection of the S4 / 2 section expansion curve and the V element line in the expansion diagram. Complete the point placement of all V element line S4 section ends; then select the "Annotation" menu in the menu bar → "Multiple Leaders" command, and number each point on the S4 / 2 section expansion line from left to right: A1, A2...A17. The V element (i.e. rolling line) of the upper section is point-placed and numbered.

[0077] S6.3: Extract the point coordinates and insert the list into the graph.

[0078] In the menu bar "Tools" → select the "Data Extraction" command → the "Data Extraction" dialog box pops up, click "Create New Data Extraction", go to "Next" → Save the data extraction as a file name: XX (.dxe default format) "Save" to the graphics folder → Check the "Data Source" Include current map", click "Next" → Select the object from which to extract data: Only keep points, click "Next" → In the pop-up dialog box: Check the filter on the right side Geometry", the "Position X, Position Y, Position Z" options will appear in the left property window. Because the Z coordinates of the plane unfolded view are all zero, Position Z can be left unchecked. Click "Next" → the "Data Extraction-Optimize Data" dialog box will pop up: a list of point, Position X, and Position Y coordinates will appear in the window, continue to click "Next" → the "Data Extraction-Select Output" dialog box will pop up: check " Output data to external file (.xls)", specify the folder where the graphics are located, and save it as "S4 / 2 section development curve coordinates".xls file. Click the highlighted "Next" button → the "Data Extraction-Select Output" dialog box pops up: click the "Finish" button to complete the "Data Extraction" command.

[0079] Open the "S4 / 2 Section Development Curve Coordinates.xls" file obtained above and edit it in Microsoft Office Excel software: delete the "Count" column, rename "Name" to "Serial Number" to correspond to the point number on the S4-S5 section development diagram. Add a title name: S4 / 2 Section Development Curve Coordinates Table. When completed, Figure 8 ; Input the above table into the drawing by "copy and paste" or "insert" command of CAD software. The extraction and insertion of the coordinate table of the S4 / 2 section development curve are completed.

[0080] Repeat the above operation: first delete all points on the S4 / 2 section development curve. Arrange points again at the intersection of the S5 / 2 section development curve and the V element line in the development diagram, repeat the above "06.1-06.3" steps, complete the extraction and insertion of the S5 / 2 section development curve coordinate table, and obtain the "S4-S5 section development diagram.dwg" file containing complete information.

[0081] Steps: In the CAD software "Data Extraction - Select Output" dialog box: check "Insert data extraction processing into graphics" to directly insert the extracted table into the graphics. Since the CAD table content and the graphics are related, it is not easy to edit, so it is not recommended. Of course, it does not rule out other commands that can also complete the coordinate extraction function.

[0082] Theoretically, a unidirectional curved surface with a curve in one direction and a straight line in the other direction is an expandable figure. All expandable sheet metal parts can be rolled by a plate rolling machine. This patented method is fully applicable; because metal materials have a certain degree of ductility while undergoing plastic deformation, for complex spatial shapes such as the steel structure of the Bird's Nest, the manufacturing method generally adopts stamping. The expansion diagram obtained by this patented layout method can be used for material cutting and arrangement.

[0083] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for obtaining a layout of a rolled part with a special-shaped cross-section and a rolling line development diagram, comprising the following steps: Step 1: Create the upper and lower section position diagram of the rolled part, and use AutoCAD software to create the elbow design section position diagram: Step 2: Create the coordinate table of the upper and lower sections of the rolled part, and create the Excel file of the S4 and S5 section coordinate table. Insert and simplify it to form a single-section plane drawing: Open the Excel software, create a new table file, and name it "S4, S5 section 1 / 4 coordinate.xlsx" file; express the X and Y coordinates of the quarter of the S4 and S5 sections of the elbow design drawing in a list, add a new column (X, Y) after the Y column, and automatically import the data entered in the first X and Y columns into the (X, Y) column for the synthetic position coordinates for standby use; Step 3: Graphically input coordinates, generate upper and lower section curves, arrange points on a single section plane, and generate a three-dimensional diagram of the upper and lower section curves; Step 4: Create a ruled surface model and a S4-S5 section surface model; click the "Open" command in the "File" drop-down menu in the operation interface menu bar, and select the "S4-S5 section curve" graphic to open; in the pop-up "DWG / DXF Import Options" card, select "Bidirectional Accuracy" for grid accuracy and click "OK" to import the CAD drawing into the software; then select the "Surface Tools" section under the "Command" line, select the "Loft" command in the pop-up left toolbar, select the S4-S5 section curve in turn, and press the "Enter" key to complete; in the pop-up "Loft Options" card: select "Straight Segment" for style, click the "Split at Tangent Point" option, enter "19" for the number of reconstruction points, and click "OK" for other options by default to generate a surface model; Step 5: Unfold the surface model into a plane; Step 6: Extract the rolling line coordinates and insert them into the development drawing. Extract the rolling line coordinates in the CAD software, edit them in the Excel software and insert them into the drawing; In step 1, the segmented positions of the elbow design are accurately transplanted into CAD as a two-dimensional basic sketch for lofting, which includes the positions of all segmented sections, so as to facilitate subsequent section-by-section expansion. In step 2, for easy viewing, use the copy command and "paste" it to the "elbow pipe design section position" of S1 under the "Edit" menu in CAD, draw the corresponding cross-sectional shape diagram, delete the redundant parts of other section position lines, and form a complete figure and save it as "S4-S5 section plan"; Step 3 includes the following four steps: S3.1: Draw auxiliary lines; S3.2: Specify the midpoint of the S4 section line as the origin, the upper right end of the S4 section line as the x-axis direction, and the front end of the auxiliary line as the y-axis direction to establish the S4 section coordinate system; S3.3: Draw the 1 / 2 lofting curve of S4 section; S3.4: Repeat the above steps and draw the 1 / 2 lofting curve of S5 section; Step 4 includes the following two steps: S4.1: Start Rhino 7 software and generate a surface model through Rhino 7 software; S4.2: Project auxiliary lines on the surface to locate the V-line position; Step 5 includes the following two steps: S5.1: The surface model of Section S4-S5 is developed together with the projection lines; S5.2: Draw a V-shaped line on the development diagram; Step 6 includes the following three steps: S6.1: The expanded view is simplified and adjusted to the XY plane of the world coordinate system; S6.2: Points and numbering at both ends of the rolling line; S6.3: Extract the point coordinates and insert the list into the graph.

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