Multi-point cold-bending forming method of curved plate

Abstract

This application provides a multi-point cold bending forming method for curved plates, comprising: obtaining a theoretical model of the curved plate; selecting at least four non-coplanar points on the theoretical model of the curved plate as target feature points; marking multiple actual feature points on the physical curved plate, wherein the relative distance between each actual feature point along the surface of the physical curved plate corresponds one-to-one with the relative distance between each target feature point along the surface of the theoretical model of the curved plate; measuring the three-dimensional coordinates of the surface of the physical curved plate relative to the lower die to obtain a physical model of the curved plate; performing coordinate transformations of translation and / or rotation on the theoretical model and / or the physical model of the curved plate to align the actual feature points with the target feature points, thereby obtaining position transformation parameters; adjusting the lower die according to the position transformation parameters to obtain the adjusted lower die; and stamping the curved plate using the adjusted lower die. The multi-point cold bending forming method for curved plates of this application can reduce reliance on manual positioning and improve processing efficiency.

Description

Technical Field

[0001] This application relates to the field of shipbuilding technology, and in particular to a method for multi-point cold bending forming of curved plates. Background Technology

[0002] Multi-point cold bending is an advanced curved plate processing technology that replaces traditional cold bending dies. It can automatically generate flexible dies based on the original curved plate design data to complete the rapid cold processing of complex-shaped curved plates. This technology features wide applicability, high processing speed, and high precision. This advanced digital processing technology requires steps such as die adjustment, curved plate feeding, curved plate bending, curved surface measurement, processing correction, and curved plate unloading.

[0003] Currently, a permanent magnet is used to hold the steel plate during the feeding process. Since this is not a rigid fixation method, it's impossible to achieve complete accuracy when positioning the curved plate at the die. Furthermore, after the die is shaped, it has a certain form that differs significantly from the shape of the plate to be processed (e.g., a flat plate). After the plate is released from the magnetic chuck, some slippage is inevitable, and repeated adjustments are inefficient. In addition, due to springback, some stamping sections require multiple passes. During a single stamping pass, the plate may slip, or the initial shape may differ significantly from the target shape, leading to large errors in positioning calculations. Therefore, positioning adjustments are necessary in subsequent stamping passes.

[0004] A multi-point cold bending forming method for curved plates is needed to ensure a tight fit between the pressed curved plate and the mold, reduce reliance on manual labor, improve processing accuracy, and solve the problems of on-site safety and difficult processing positioning. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a multi-point cold bending forming method to solve the problem of difficult positioning of curved plates in the existing multi-point cold bending process.

[0006] In a first aspect, this application provides a multi-point cold bending forming method for curved plates, applied to a three-dimensional CNC plate bending machine, wherein the three-dimensional CNC plate bending machine includes an upper die and a lower die, and the multi-point cold bending forming method for curved plates includes:

[0007] Obtain the theoretical model of the curved plate;

[0008] At least four non-coplanar points are selected on the curved plate theoretical model as target feature points;

[0009] Multiple actual feature points are marked on the curved plate, and the relative distance between each actual feature point along the surface of the curved plate corresponds one-to-one with the relative distance between each target feature point along the surface of the theoretical model of the curved plate.

[0010] The three-dimensional coordinates of the curved plate surface relative to the lower pressing mold are measured to obtain the curved plate physical model;

[0011] The coordinate transformation of the curved plate theoretical model and / or the curved plate physical model is performed by translation and / or rotation to align the actual feature points with the target feature points, thereby obtaining the position transformation parameters;

[0012] The lower die is shaped according to the position transformation parameters to obtain the shaped lower die;

[0013] The curved plate is stamped using the adjusted die.

[0014] In one implementation of the first aspect, when the length of the curved plate is less than 3m, the number of target feature points is 4; when the length of the curved plate is greater than 3m, the curved plate is divided into multiple processing sections, and the number of target feature points in each processing section is 4.

[0015] In one implementation of the first aspect, the length of the curved plate is less than 3m, and the length of the lower die is L in the feeding direction of the curved plate; the curved plate has a first vertex, a second vertex, a third vertex, and a fourth vertex arranged in a clockwise direction, and the direction from the first vertex to the second vertex is the feeding direction; the target feature points include:

[0016] The first target feature point is located on the edge line of the curved plate where the first vertex and the second vertex are located, and the distance between the first target feature point and the second vertex is k1×L, where 1 / 2 <k1<3 / 4;

[0017] The second target feature point is located at the midpoint of the curved plate rib line where the second vertex and the third vertex are located;

[0018] The third target feature point is located on the edge line of the curved plate where the third vertex and the fourth vertex are located, and the distance between the third target feature point and the third vertex is k2×L, where 1 / 2 <k2<3 / 4;

[0019] The fourth target feature point is located at the midpoint of the curved plate rib line where the first target feature point and the third target feature point are located;

[0020] The actual feature points include:

[0021] The first actual feature point is located on the curved plate, and the position of the first actual feature point corresponds to the position of the first target feature point.

[0022] The second actual feature point is located on the curved plate, and the position of the second actual feature point corresponds to that of the second target feature point.

[0023] The third actual feature point is located on the curved plate, and the position of the third actual feature point corresponds to that of the third target feature point.

[0024] The fourth actual feature point is located on the curved plate, and the position of the fourth actual feature point corresponds to that of the fourth target feature point.

[0025] In one implementation of the first aspect, the length of the curved plate is greater than 3m; the length of the lower die is L in the feeding direction of the curved plate; the curved plate has a first vertex, a second vertex, a third vertex, and a fourth vertex arranged in a clockwise direction, and the direction from the first vertex to the second vertex is the feeding direction; the target feature points include:

[0026] The first target feature point is located on the edge line of the curved plate where the first vertex and the second vertex are located, and the distance between the first target feature point and the second vertex is k1×L, where 1 / 2 <k1<3 / 4;

[0027] The second target feature point is located at the midpoint of the curved plate rib line where the second vertex and the third vertex are located;

[0028] The third target feature point is located on the edge line of the curved plate where the third vertex and the fourth vertex are located, and the distance between the third target feature point and the third vertex is k2×L, where 1 / 2 <k2<3 / 4;

[0029] The fourth target feature point is located at the midpoint of the curved plate rib line where the first target feature point and the third target feature point are located;

[0030] The fifth target feature point is located on the edge line of the curved plate where the first vertex and the second vertex are located, and the distance between the fifth target feature point and the second vertex is k3×L, where 1 <k3<5 / 3;

[0031] The sixth target feature point is the midpoint between the first vertex and the second vertex, which is taken as the feature reference point, and the midpoint of the curved plate rib line where the feature reference point is located is the sixth target feature point.

[0032] The seventh target feature point is located on the edge line of the curved plate where the third vertex and the fourth vertex are located, and the distance between the seventh target feature point and the third vertex is k4×L, where 1 <k4<5 / 3;

[0033] The eighth target feature point is located at the midpoint of the curved plate rib line where the fifth and seventh target feature points are located.

[0034] The midpoint between the second target feature point and the fourth target feature point is taken as the first center point, and the midpoint between the second actual feature point and the fourth actual feature point is taken as the second center point;

[0035] The coordinate transformation involving translation and / or rotation of the theoretical model and / or physical model of the curved plate specifically includes:

[0036] Perform a translation operation on the physical model of the curved plate so that the first center point and the second center point coincide;

[0037] The curved plate physical model is rotated around the first axis of rotation so that the second actual feature point, the fourth actual feature point, the second target feature point, and the fourth target feature point are collinear. The first axis of rotation passes through the second center point and is perpendicular to the plane containing the second target feature point, the second center point, and the second actual feature point.

[0038] Using the straight line where the second actual feature point and the fourth actual feature point are located as the second axis of rotation, the physical model of the curved board is rotated around the second axis of rotation to achieve registration between the physical model of the curved board and the theoretical model of the curved board.

[0039] In one implementation of the first aspect, the rotation of the curved plate physical model around the second axis is a second coordinate transformation, and the formula for the second coordinate transformation is as follows:

[0040]

[0041] Wherein, P represents the coordinates of each of the actual feature points before the second coordinate transformation;

[0042] P′ represents the coordinates of each of the actual feature points after the second coordinate transformation;

[0043] O1 represents the coordinates of the first center point;

[0044] O2 is the coordinate of the second center point before the second coordinate transformation;

[0045] R1 is the rotation matrix;

[0046] The formula for calculating the rotation matrix R1 is as follows:

[0047]

[0048] Where θ is the rotation angle about the second axis of rotation;

[0049] (x1, y1, z1) is the unit direction vector of the second axis of rotation.

[0050] In one implementation of the first aspect, the rotation angle θ is calculated using the following formula:

[0051]

[0052] Where A is the coordinate of the second target feature point;

[0053] D represents the coordinates of the fourth target feature point;

[0054] F represents the coordinates of the second actual feature point before the second coordinate transformation;

[0055] H represents the coordinates of the fourth actual feature point before the second coordinate transformation.

[0056] In one implementation of the first aspect, the unit direction vector is calculated using the following formula:

[0057]

[0058] Where A is the coordinate of the second target feature point;

[0059] D represents the coordinates of the fourth target feature point;

[0060] F represents the coordinates of the second actual feature point before the second coordinate transformation;

[0061] H represents the coordinates of the fourth actual feature point before the second coordinate transformation.

[0062] In one implementation of the first aspect, the normal vector of the plane containing the first target feature point, the second target feature point, and the fourth target feature point is a first normal vector; the normal vector of the plane containing the first actual feature point, the second target feature point, and the fourth target feature point is a second normal vector; the angle between the first normal vector and the second normal vector is a first angle; the normal vector of the plane containing the second target feature point, the third target feature point, and the fourth target feature point is a third normal vector; the normal vector of the plane containing the second target feature point, the third actual feature point, and the fourth target feature point is a fourth normal vector; the angle between the third normal vector and the fourth normal vector is a second angle. The step of rotating the physical model of the curved board around the second axis of rotation to achieve registration between the physical model of the curved board and the theoretical model of the curved board specifically includes: rotating the physical model of the curved board around the second axis of rotation until the first angle is less than a first threshold and the second angle is less than a second threshold, thereby achieving registration between the actual feature point and the target feature point.

[0063] In one implementation of the first aspect, the step of adjusting the shape of the pressing die according to the position transformation parameters to obtain the adjusted pressing die specifically includes:

[0064] The curved plate theoretical model is inversely transformed according to the position transformation parameters to obtain the position-updated curved plate theoretical model;

[0065] The lower die is reshaped according to the curved plate theory model updated based on the position, resulting in the reshaped lower die.

[0066] As mentioned above, the multi-point cold bending forming method for curved plates in this application can reduce the reliance on manual positioning and improve processing efficiency. Attached Figure Description

[0067] Figure 1 The diagram shown is a schematic representation of a pre-formed curved plate in the prior art.

[0068] Figure 2 The diagram shows the structure of a pressing die in its initial state in the prior art.

[0069] Figure 3 Shown as a pressing die in the prior art, according to Figure 1 A schematic diagram of the structure after the curved plate has been shaped.

[0070] Figure 4 The diagram shown is a schematic diagram of dividing a long plate into processing sections according to an embodiment of this application.

[0071] Figure 5 This is a schematic diagram illustrating the principle of selecting target feature points in one embodiment of this application.

[0072] Figure 6 This is a schematic diagram illustrating the selection of actual feature points in one embodiment of this application.

[0073] Figure 7 The diagram shown is a schematic diagram of the principle of selecting target feature points on a long board in one embodiment of this application.

[0074] Figure 8 The diagram shown is a schematic diagram of a physical model of a rotating curved plate about a first axis of rotation, according to one embodiment of this application.

[0075] Figure 9 This is a schematic diagram showing the relative positions of the physical model and the theoretical model of the curved plate after they have been rotated around the first axis in one embodiment of this application.

[0076] Figure 10 This diagram shows a schematic representation of a physical model of a curved plate rotating about a second axis, according to one embodiment of this application. (Component labeling explanation follows.)

[0077] Explanation of icon numbers

[0078] 100. Curved plate theoretical model; 110. First processing section; 120. Second processing section; 130. Overlapping area; 140. Curved plate rib line; 200. Lower die; 210. Punch; 220. Profile. Detailed Implementation

[0079] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0080] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0081] A three-dimensional CNC bending machine for multi-point cold bending includes an upper die and a lower die. After each stamping, the springback of the curved plate needs to be measured. Based on the springback and the theoretical model of the curved plate, the lower die is adjusted. The theoretical model of the curved plate represents the three-dimensional coordinates of the curved plate relative to the die after it has been pressed and formed. After multiple stampings and adjustments, a finished curved plate that meets the accuracy requirements is obtained.

[0082] The specific shaping principle of multi-point cold bending is as follows: Figures 1-3 As shown. Figure 1 The theoretical model 100 for the curved plate represents the ideal shape of the curved plate after processing. Figure 2 The structure of the pressing die 200 in its initial state before shaping is shown. The pressing die consists of multiple punches 210. Each punch includes multiple columns that can move up and down, and a movable contact head (not shown) located at the top of the columns that can adaptively adjust its orientation according to the contact point. Figure 2 Before shaping, the tops of all punches are aligned. The structure of the lower die after shaping is as follows: Figure 3 As shown. Assuming the curved plate has no springback issue, the lifting height of each punch is adjusted so that the top of each punch forms an arc surface consistent with the theoretical model of the curved plate. In reality, the curved plate will spring back after stamping, so the springback coefficient must be considered when setting the lifting height of each punch.

[0083] The method of adjusting the shape of the lower die to match the shape of the constituent surfaces 220 of each punch 210 of the lower die with the shape of the curved plate theoretical model 100 can refer to existing technology and is not the focus of improvement of this invention. The present invention mainly solves the problem of low positioning accuracy between the curved plate and the die caused by the slippage of the curved plate after each stamping.

[0084] The technical solutions in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0085] like Figure 1 As shown, this embodiment provides a multi-point cold bending forming method for curved plates, applied to a three-dimensional CNC bending machine. The three-dimensional CNC bending machine includes an upper die and a lower die. The multi-point cold bending forming method for curved plates includes:

[0086] Step S100: Obtain the theoretical model of the curved plate.

[0087] Step S200: Select at least four non-coplanar points on the curved plate theoretical model as target feature points.

[0088] Step S300: Mark multiple actual feature points on the curved plate physical object. The relative distance between each actual feature point along the surface of the curved plate physical object corresponds one-to-one with the relative distance between each target feature point along the surface of the curved plate theoretical model.

[0089] Step S400: Measure the three-dimensional coordinates of the curved plate surface relative to the lower die to obtain the curved plate physical model;

[0090] Step S500: Perform coordinate transformations of translation and / or rotation on the theoretical model and / or physical model of the curved plate to register the actual feature points with the target feature points and obtain the position transformation parameters.

[0091] Step S600: Adjust the shape of the lower die according to the position transformation parameters to obtain the adjusted lower die;

[0092] Step S700: Use the adjusted lower die to stamp the curved plate.

[0093] In the multi-point cold bending forming process of curved plates, the lower die is adjusted according to the theoretical model of the curved plate. Under ideal conditions without considering springback, the shape of the lower die surface 220 after adjustment is consistent with the shape of the surface of the theoretical model of the curved plate. The shape of the theoretical model of the curved plate is set by the ship designers. The theoretical model of the curved plate defines the processing target of multi-point cold bending forming. The coordinate reference system of each point in the theoretical model of the curved plate can be consistent with the coordinate reference system of each punch in the lower die during adjustment, or it can be inconsistent with the coordinate reference system of each punch in the lower die during adjustment. When the coordinate reference system of each point in the theoretical model of the curved plate is inconsistent with the coordinate reference system of each punch in the lower die during adjustment, it is necessary to unify the theoretical model of the curved plate and the physical model of the curved plate to the same coordinate system through coordinate transformations such as translation and / or rotation. Existing technologies can be used to unify the coordinate system.

[0094] The physical model of the curved plate represents both the shape of the plate after the previous stamping and before the next stamping, and its position relative to the lower die. Ideally, after multiple stampings, the position of the physical model matches the position of the theoretical model. However, in actual processing, the curved plate may slip relative to the lower die, causing the position of the physical model to differ from the theoretical model.

[0095] The physical model of the curved plate can be obtained using equipment such as a 3D laser scanner. The physical model of the curved plate should include at least the coordinate data of the actual feature points corresponding to the positions of the target feature points.

[0096] The target feature points are selected from the theoretical model of the curved plate, while the actual feature points are selected from the physical model of the curved plate. Ideally, registration is complete when each target feature point corresponds one-to-one with each actual feature point. In actual manufacturing, the shape of the curved plate may not yet match the theoretical model. Therefore, during registration, a preset range of positional deviation is allowed between the target feature points and their corresponding actual feature points.

[0097] Since the curved plate processed by the three-dimensional CNC bending machine may be a complex curved surface that cannot be completed by the traditional three-axis roll forming, the target feature points include at least 4 non-coplanar points to adapt to the three-dimensional structure of the complex curved surface, and to ensure that the theoretical model and the physical model of the curved plate are registered as a whole, so as to avoid the situation where only the local registration of the target feature points occurs, while the other parts have excessive errors.

[0098] The registered position transformation parameters reflect the positioning error caused by slippage and other factors on the curved plate. Therefore, during the shaping of the lower die, in addition to considering the shape of the curved plate's theoretical model and its springback characteristics, the position and orientation of the curved plate's theoretical model can be changed based on this positioning error. This allows for compensation of the positioning error caused by the curved plate's slippage through the shaping of the lower die.

[0099] Therefore, the lower die after the adjustment of the present invention automatically compensates for the error caused by the slippage of the curved plate, thereby improving the processing efficiency of multi-point cold bending of the curved plate.

[0100] When the curved plate is small, the processing area of ​​the 3D CNC bending machine can completely cover the curved plate, and the processing can be completed by multiple punchings in one feeding. When the curved plate is long, the processing area of ​​the 3D CNC bending machine is not enough to completely cover the curved plate. A segmented processing method can be adopted, that is, the curved plate is divided into multiple processing sections, and one processing section is sent to the processing area at a time to gradually complete the processing of the entire curved plate.

[0101] To accommodate curved boards of varying lengths, in this embodiment, when the length of the curved board is less than 3m, the number of target feature points is 4. When the length of the curved board is greater than 3m, the curved board is divided into multiple processing sections, with each processing section containing 4 target feature points.

[0102] To further ensure the continuity of shape changes between different processing sections, adjacent processing sections have overlapping areas. For example... Figure 4 As shown, the curved plate includes a first processing section 110 located within a solid frame and a second processing section 120 located within a dashed frame. Figure 4 The area corresponding to the shadow box in the image is the overlapping area 130.

[0103] like Figure 5 , Figure 6 As shown, in this embodiment, the length of the curved plate is less than 3m, and the length of the lower die is L in the feeding direction of the curved plate. The curved plate has a first vertex D1, a second vertex D2, a third vertex D3, and a fourth vertex D4 arranged in a clockwise direction, and the direction from the first vertex D1 to the second vertex D2 is the feeding direction.

[0104] The target feature points include the first target feature point C, the second target feature point A, the third target feature point B, and the fourth target feature point D. The first target feature point C is located on the curved plate edge line where the first vertex D1 and the second vertex D2 are located, and the distance between the first target feature point C and the second vertex is k1×L, where 1 / 2 < k1 < 3 / 4. The second target feature point A is located at the midpoint of the curved plate rib line 140 where the second vertex D2 and the third vertex D3 are located. The third target feature point B is located on the curved plate edge line where the third vertex D3 and the fourth vertex D4 are located, and the distance between the third target feature point B and the third vertex D3 is k2×L, where 1 / 2 < k2 < 3 / 4. The fourth target feature point D is located at the midpoint of the curved plate rib line where the first target feature point and the third target feature point are located.

[0105] The actual feature points include the first actual feature point E, the second actual feature point F, the third actual feature point G, and the fourth actual feature point H located on the physical curved plate. The position of the first actual feature point E corresponds to that of the first target feature point C. The position of the second actual feature point F corresponds to that of the second target feature point A. The position of the third actual feature point G corresponds to that of the third target feature point B. The position of the fourth actual feature point H corresponds to that of the fourth target feature point D.

[0106] In this embodiment, when selecting the positions of the first target feature point C, the second target feature point A, and the third target feature point B, the second vertex D2 and the third vertex D3 can be referred to, and the corresponding lengths can be measured on the edge line of the curved plate theoretical model. When selecting the position of the fourth target feature point D, the corresponding length can be measured on the tangent line passing through the first target feature point C and the third target feature point B. The selected target feature points A, B, C, and D in this embodiment can not only reflect the maximum deformation of the whole curved plate but also avoid the problem of overfitting caused by too many feature points. The measurement of the actual feature points E, F, G, and H can refer to the corresponding target feature points.

[0107] As Figure 7 shown, in this embodiment, the length of the curved plate is greater than 3m; in the feeding direction of the curved plate, the length of the lower pressing die is L; the curved plate has the first vertex D1, the second vertex D2, the third vertex D3, and the fourth vertex D4 arranged in a clockwise direction, and the direction from the first vertex D1 to the second vertex D2 is the feeding direction; the target feature points include:

[0108] The first target feature point c, located on the curved plate edge line where the first vertex D1 and the second vertex D2 are located, and the distance between the first target feature point c and the second vertex D2 is k1×L, where 1 / 2 < k1 < 3 / 4.

[0109] The second target feature point a, located at the midpoint of the curved plate rib line where the second vertex D2 and the third vertex D3 are located.

[0110] The third target feature point b is located on the edge line of the curved plate where the third vertex D3 and the fourth vertex D4 are located, and the distance between the third target feature point and the third vertex is k2×L, where 1 / 2 <k2<3 / 4。

[0111] The fourth target feature point d is located at the midpoint of the curved plate rib line where the first target feature point c and the third target feature point b are located.

[0112] The fifth target feature point g is located on the edge line of the curved plate where the first vertex D1 and the second vertex D2 are located, and the distance between the fifth target feature point g and the second vertex D2 is k3×L, where 1 <k3<5 / 3。

[0113] The sixth target feature point e is determined by taking the midpoint between the first vertex D1 and the second vertex D2 as the feature reference point, and the midpoint of the curved plate rib line where the feature reference point is located as the sixth target feature point e.

[0114] The seventh target feature point f is located on the edge line of the curved plate where the third vertex D3 and the fourth vertex D4 are located, and the distance between the seventh target feature point f and the third vertex D3 is k4×L, where 1 <k4<5 / 3。

[0115] The eighth target feature point h is located at the midpoint of the curved plate rib line where the fifth target feature point g and the seventh target feature point f are located.

[0116] like Figure 8 , Figure 9 As shown, the curved plate theory model uses Figure 8 The dashed lines in the diagram represent the physical model of the curved plate. Figure 8 The solid line in the diagram indicates that the midpoint between the second target feature point A and the fourth target feature point D is the first center point O1, and the midpoint between the second actual feature point F and the fourth actual feature point H is the second center point O2.

[0117] In this embodiment, the coordinate transformation of the curved plate theoretical model and / or the curved plate physical model by translation and / or rotation specifically includes:

[0118] Step S510: Perform a translation operation on the curved plate physical model so that the first center point O1 and the second center point O2 coincide. The model after the first center point O1 and the second center point O2 coincide is as follows. Figure 8 As shown.

[0119] Step S520: Rotate the physical model of the curved plate around the first axis of rotation, so that the second actual feature point F, the fourth actual feature point H, the second target feature point A, and the fourth target feature point are collinear by D. The first axis of rotation passes through the second center point O2 and is perpendicular to the plane containing the second target feature point A, the second center point O2, and the second actual feature point F. Take a point R1 on the first axis of rotation; then line O2R1 is perpendicular to line O2F and line O2A. The model after lines AD and FH are collinear is as follows. Figure 9 As shown.

[0120] Step S530, as follows Figure 10 As shown, the physical model of the curved plate is rotated around the straight line where the second actual feature point F and the fourth actual feature point H are located as the second axis of rotation, thereby achieving the registration between the physical model of the curved plate and the theoretical model of the curved plate.

[0121] When the curved plate is a hyperboloid, the first bending direction is around the straight line containing FH, and the second bending direction is around one of the rib lines. In this embodiment, the AD line and FH line of the curved plate are first aligned, and then the edge lines are brought closer by rotation, ensuring that the curvature of the hyperboloid is basically consistent in the first bending direction. This embodiment also ensures that the position of the curved plate is consistent in the feeding direction by coinciding the first center point O1 and the second center point O2. According to the general shape of the curved plate, the target feature points A, B, C, and D are connected to form a tetrahedron, and the actual E, F, G, and H in the processing process also form another tetrahedron. Figure 9 In this configuration, one edge of each tetrahedron CABD and tetrahedron EFGH already coincides. Therefore, it is only necessary to rotate around the AD(FH) axis until the spatial distance between points E and C is equal to or nearly equal to the spatial distance between points B and G. After each cold bend, the FH line of the curved plate is approximately located at the lowest point of the concave surface formed by the lower die. During the processing, the positions of the actual feature points F and H on the curved plate do not change much, while the positions of the actual feature points E and G change significantly. In this embodiment, during the shaping process, the AD line and the FH line are first aligned, and then rotated around the AD(FH) axis until the spatial distance between points E and C is equal to or nearly equal to the spatial distance between points B and G. This minimizes the impact of subsequent processing on parts that have already met the processing requirements in the previous processing, thereby improving processing efficiency.

[0122] The first coordinate transformation involves rotating the physical model of the curved plate around the first axis of rotation, and the second coordinate transformation involves rotating the physical model of the curved plate around the second axis of rotation. After performing coordinate transformations on the actual feature points E, F, G, and H, the new actual feature points are obtained as E′, F′, G′, and H. ′ .

[0123] like Figure 8 As shown, the physical model of the curved plate rotating around the second axis O1R1 represents the second coordinate transformation. The formula for the second coordinate transformation is as follows:

[0124]

[0125] Where P represents the coordinates of each actual feature point before the second coordinate transformation;

[0126] P′ represents the coordinates of each actual feature point after the second coordinate transformation;

[0127] O1 represents the coordinates of the first center point;

[0128] O2 represents the coordinates of the second center point before the second coordinate transformation;

[0129] R1 is the rotation matrix.

[0130] The formula for calculating the rotation matrix R1 is as follows:

[0131]

[0132] Where θ is the rotation angle about the second axis;

[0133] (x1, y1, z1) is the unit direction vector of the second axis of rotation.

[0134] Specifically, the rotation angle θ is calculated using the following formula:

[0135]

[0136] The unit direction vector is calculated using the following formula:

[0137]

[0138] The first method to measure registration error is to calculate the distance d1 between the target feature point C and the actual feature point E, and the distance d2 between the target feature point B and the actual feature point G. When both distances d1 and d2 are less than a certain threshold, registration is considered complete. This registration method requires high accuracy in the labeling and measurement of the actual feature points.

[0139] The specific calculation formula is as follows:

[0140]

[0141]

[0142] Among them, (X) C ,Y C Z C () represents the coordinates of the target feature point C;

[0143] (X E ,Y E Z E() represents the coordinates of the target feature point E;

[0144] (X B ,Y B Z B () represents the coordinates of the target feature point B;

[0145] (X G ,Y G Z G ) represents the coordinates of the target feature point C.

[0146] In this embodiment, the normal vector of the plane containing the first target feature point C, the second target feature point A, and the fourth target feature point D is the first normal vector, and the normal vector of the plane containing the first actual feature point E, the second target feature point A, and the fourth target feature point D is the second normal vector. The angle between the first normal vector and the second normal vector is the first included angle. The normal vector of the plane containing the second target feature point A, the third target feature point B, and the fourth target feature point D is the third normal vector. The normal vector of the plane containing the second target feature point A, the third actual feature point G, and the fourth target feature point D is the fourth normal vector. The angle between the third normal vector and the fourth normal vector is the second included angle. The physical model of the curved plate is rotated around the second axis of rotation to achieve registration between the physical model and the theoretical model of the curved plate. Specifically, this includes rotating the physical model of the curved plate around the second axis of rotation until the first included angle is less than a first threshold and the second included angle is less than a second threshold, thereby achieving registration between the actual feature points and the target feature points.

[0147] The first normal vector in this embodiment reflects Figure 5 , Figure 6 The orientation of the upper half of the curved plate in the figure, and the second normal vector in this embodiment reflect... Figure 5 , Figure 6 The orientation of the lower half of the curved plate is considered. A smaller first included angle indicates that the orientation of the upper half of the actual curved plate is closer to the theoretical model of the curved plate, and a smaller second included angle indicates that the orientation of the lower half of the actual curved plate is closer to the theoretical model of the curved plate. This embodiment does not directly use the distance between the actual feature point and the target feature point as the registration error standard. Instead, it divides the curved plate into upper and lower parts and uses the orientation of the upper and lower parts as the registration error standard. When both the first and second included angles are small, it indicates that the orientation of the curved plate to be processed is consistent with the orientation of the surface formed by the lower die, thereby reducing the sensitivity to the marking error of the actual feature points.

[0148] Specifically, the formula for calculating the first normal vector is as follows:

[0149]

[0150] The formula for calculating the second normal vector is as follows:

[0151]

[0152] The formula for calculating the third normal vector is as follows:

[0153]

[0154] The formula for calculating the fourth normal vector is as follows:

[0155]

[0156] After registering the theoretical model and the physical model of the curved board, position transformation parameters are obtained, such as coordinate transformation parameters for translation and / or rotation. With these coordinate transformation parameters, theoretically, the physical curved board can be translated and / or rotated in the same way as the physical model and the actual curved board, according to their size ratios. To avoid introducing new positioning errors by directly adjusting the pose of the physical curved board, in this embodiment, the lower die is shaped according to the position transformation parameters to obtain the shaped lower die, specifically including:

[0157] Step S610: Perform an inverse transformation on the curved plate theoretical model according to the position transformation parameters to obtain a position-updated curved plate theoretical model. On the one hand, the shape of the updated curved plate theoretical model is the ideal target shape. On the other hand, the position of the updated curved plate theoretical model corresponds to the position of the actual curved plate after slippage.

[0158] Step S620: Adjust the shape of the lower die according to the position-updated curved plate theoretical model to obtain the adjusted lower die.

[0159] The scope of protection for the multi-point cold bending forming method of curved plates in this application is not limited to the execution order of the steps listed in this embodiment. Any solution achieved by adding, subtracting, or replacing steps in the prior art based on the principles of this application is included within the scope of protection of this application.

[0160] The descriptions of the processes or structures corresponding to the above figures each have their own emphasis. For parts of a process or structure that are not described in detail, please refer to the relevant descriptions of other processes or structures.

[0161] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A multi-point cold bending forming method of a curved plate applied to a three-dimensional numerical control bending machine, the three-dimensional numerical control bending machine comprising an upper press die and a lower press die, characterized in that, The multi-point cold bending forming method of the curved plate includes: Obtain the theoretical model of the curved plate; Select at least 4 non-coplanar points on the theoretical model of the curved plate as target feature points; when the length of the curved plate is less than 3m, the number of the target feature points is 4; wherein, the length of the curved plate is less than 3m, in the feeding direction of the curved plate, the length of the lower pressing die is L; the curved plate has a first vertex, a second vertex, a third vertex, and a fourth vertex arranged in a clockwise direction, and the direction from the first vertex to the second vertex is the feeding direction; the target feature points include: a first target feature point, located on the curved plate edge line where the first vertex and the second vertex are located, and the distance between the first target feature point and the second vertex is k1×L, where 1 / 2 < k1 < 3 / 4; a second target feature point, located at the midpoint of the curved plate rib line where the second vertex and the third vertex are located; a third target feature point, located on the curved plate edge line where the third vertex and the fourth vertex are located, and the distance between the third target feature point and the third vertex is k2×L, where 1 / 2 < k2 < 3 / 4; a fourth target feature point, located at the midpoint of the curved plate rib line where the first target feature point and the third target feature point are located; Mark multiple actual feature points on the physical curved plate, and the relative distances between the actual feature points along the surface of the physical curved plate correspond one-to-one to the relative distances between the target feature points along the surface of the theoretical model of the curved plate; the actual feature points include: a first actual feature point, located on the physical curved plate, and the position of the first actual feature point corresponds to that of the first target feature point; a second actual feature point, located on the physical curved plate, and the position of the second actual feature point corresponds to that of the second target feature point; a third actual feature point, located on the physical curved plate, and the position of the third actual feature point corresponds to that of the third target feature point; a fourth actual feature point, located on the physical curved plate, and the position of the fourth actual feature point corresponds to that of the fourth target feature point; Measure the three-dimensional coordinates of the surface of the physical curved plate relative to the lower pressing die to obtain the physical curved plate model; Perform coordinate transformation of translation and / or rotation on the theoretical model of the curved plate and / or the physical curved plate model to register the actual feature points with the target feature points, and obtain the position transformation parameters; Adjust the shape of the lower pressing die according to the position transformation parameters to obtain the adjusted lower pressing die; Stamp the curved plate with the adjusted lower pressing die; Wherein, the midpoint of the second target feature point and the fourth target feature point is used as the first center point, and the midpoint of the second actual feature point and the fourth actual feature point is used as the second center point; the coordinate transformation of translation and / or rotation on the theoretical model of the curved plate and / or the physical curved plate model specifically includes: Perform a translation operation on the physical curved plate model to make the first center point and the second center point coincide; The curved plate physical model is rotated around the first axis of rotation so that the second actual feature point, the fourth actual feature point, the second target feature point, and the fourth target feature point are collinear. The first axis of rotation passes through the second center point and is perpendicular to the plane containing the second target feature point, the second center point, and the second actual feature point. Using the straight line containing the second and fourth actual feature points as the second axis of rotation, the physical model of the curved board is rotated around the second axis of rotation to achieve registration between the physical model of the curved board and the theoretical model of the curved board; rotating the physical model of the curved board around the second axis of rotation constitutes the second coordinate transformation, and the formula for the second coordinate transformation is as follows: ， in, The coordinates of each of the actual feature points prior to the second coordinate transformation; The coordinates of each of the actual feature points after the second coordinate transformation; The coordinates of the first center point; The coordinates of the second center point before the second coordinate transformation; Let the rotation matrix be the rotation matrix; The calculation formula is as follows: ， in, The rotation angle is the rotation about the second axis. is the unit direction vector of the second axis of rotation.

2. The multi-point cold bending forming method for curved plates according to claim 1, characterized in that, When the length of the curved plate is greater than 3m, the curved plate is divided into multiple processing sections, and the number of target feature points in each processing section is 4.

3. The multi-point cold bending forming method for curved plates according to claim 2, characterized in that, The length of the curved plate is greater than 3m; the length of the lower die is L in the feeding direction of the curved plate; the curved plate has a first vertex, a second vertex, a third vertex, and a fourth vertex arranged in a clockwise direction, and the direction from the first vertex to the second vertex is the feeding direction; The target feature points include: The first target feature point is located on the edge line of the curved plate where the first vertex and the second vertex are located, and the distance between the first target feature point and the second vertex is k1×L, where 1 / 2 <k1<3 / 4; The second target feature point is located at the midpoint of the curved plate rib line where the second vertex and the third vertex are located; The third target feature point is located on the edge line of the curved plate where the third vertex and the fourth vertex are located, and the distance between the third target feature point and the third vertex is k2×L, where 1 / 2 <k2<3 / 4; The fourth target feature point is located at the midpoint of the curved rib line where the first target feature point and the third target feature point are located; The fifth target feature point is located on the edge line of the curved plate where the first vertex and the second vertex are located, and the distance between the fifth target feature point and the second vertex is k3×L, where 1 <k3<5 / 3; The sixth target feature point is the midpoint between the first vertex and the second vertex, which is taken as the feature reference point, and the midpoint of the curved plate rib line where the feature reference point is located is the sixth target feature point. The seventh target feature point is located on the edge line of the curved plate where the third vertex and the fourth vertex are located, and the distance between the seventh target feature point and the third vertex is k4×L, where 1 <k4<5 / 3; The eighth target feature point is located at the midpoint of the curved plate rib line where the fifth and seventh target feature points are located.

4. The multi-point cold bending forming method for curved plates according to claim 1, characterized in that, The rotation angle The following formula is used for calculation: ， in, The coordinates of the second target feature point; The coordinates of the fourth target feature point; The coordinates of the second actual feature point before the second coordinate transformation; The coordinates of the fourth actual feature point prior to the second coordinate transformation.

5. The multi-point cold bending forming method for curved plates according to claim 1, characterized in that, The unit direction vector is calculated using the following formula: ， in, The coordinates of the second target feature point; The coordinates of the fourth target feature point; The coordinates of the second actual feature point before the second coordinate transformation; The coordinates of the fourth actual feature point prior to the second coordinate transformation.

6. The multi-point cold bending forming method for curved plates according to claim 1, characterized in that, The normal vector of the plane containing the first target feature point, the second target feature point, and the fourth target feature point is the first normal vector; the normal vector of the plane containing the first actual feature point, the second target feature point, and the fourth target feature point is the second normal vector; the angle between the first normal vector and the second normal vector is the first angle; the normal vector of the plane containing the second target feature point, the third target feature point, and the fourth target feature point is the third normal vector; the normal vector of the plane containing the second target feature point, the third actual feature point, and the fourth target feature point is the fourth normal vector; the angle between the third normal vector and the fourth normal vector is the second angle. The step of rotating the physical model of the curved board around the second axis of rotation to achieve registration between the physical model of the curved board and the theoretical model of the curved board specifically includes: rotating the physical model of the curved board around the second axis of rotation until the first angle is less than a first threshold and the second angle is less than a second threshold, thereby achieving registration between the actual feature point and the target feature point.

7. The multi-point cold bending forming method for curved plates according to claim 1, characterized in that, The step of adjusting the shape of the lower die according to the position transformation parameters to obtain the adjusted lower die specifically includes: The curved plate theoretical model is inversely transformed according to the position transformation parameters to obtain the position-updated curved plate theoretical model; The lower die is reshaped according to the curved plate theory model updated based on the position, resulting in the reshaped lower die.

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