A method for creating a drawing blank surface based on a parametric mesh surface

Abstract

The present invention relates to a method for creating a drawing blank surface based on a parametric mesh surface, and belongs to the technical field of stamping methods. The technical solution of the present invention is: in a commonly used three-dimensional modeling software, a reference plane and a reference point are set, and a group of orthogonal section curves required for the parametric mesh surface is created using a parametric sketch module method, and then a single face blank surface with parametric characteristics is obtained from the group of orthogonal section curves through a mesh command. The beneficial effect of the present invention is that it can be completed with the help of any commonly used three-dimensional industrial design software, and only commonly used simple modeling commands such as reference planes, sketches, reference points, meshes and fillets are used, and simple and efficient operation steps are provided, which can be applied to the efficient and high-quality design of the drawing blank surfaces of various stamping covers.

Description

Technical Field

[0001] The invention relates to a method for creating a drawing pressing surface based on a parameterized mesh surface, and belongs to the technical field of stamping methods. Background Art

[0002] The product design of large stamping cover parts and the process design of stamping and drawing currently adopt three-dimensional design methods. The process design steps of drawn parts generally follow the following steps: determine the drawing direction based on the three-dimensional product digital model, fill the internal holes of the product, create the product process extension surface (including the expansion of the flanging and shaping area), establish the pressing surface and the punch contour line, generate the pressing surface, produce the punch radius, generate the die radius and draw ribs, etc. The design of the pressing surface is a key design step. A good drawing pressing surface has the following main features: (1) Simple shape and smooth surface, which facilitates the uniform flow of materials to the center of the product; (2) Along the contour line of the drawing punch, the pressing surface ensures that the process supplement part of the drawing part changes evenly with the product shape, so that the material flow speed is relatively uniform during drawing and wrinkling is avoided. (3) Along the drawing height direction, the height of the overall position of the pressing surface should ensure that the degree of drawing deformation during stamping is moderate, avoiding both drawing cracking and insufficient plastic deformation and wrinkling. In order to meet the above requirements and realize rapid design and adjustment of the pressing surface, the design of the drawing pressing surface should adopt parametric design methods as much as possible. If conditions permit, it should be designed as a single sheet or stitched together by as few sheets as possible to reduce the complex correlation between multiple sheets when stitching multiple sheets, and ensure the stitching tolerance and smooth continuity (G1 and above continuity) between the sheets.

[0003] At present, the stamping industry often uses the multi-faceted splicing method when designing the drawing blank surface of large stamping parts, that is, first generate a separate local blank surface, and then make these surfaces as transition connections or splicing (stitching) to form a complete blank surface. In actual modeling work, traditional methods often use non-fully parametric design methods. The blank surface obtained in this way is a multi-piece stitched surface. In order to ensure the smoothness of the stitched surface, it is necessary to maintain the smoothness between the local blank surfaces, so the design and modification efficiency is low. Summary of the invention

[0004] The purpose of the present invention is to provide a method for creating a drawing blank surface based on a parametric mesh surface. In commonly used three-dimensional modeling software, the parametric function of the sketch is used to draw the cross-sectional curve group required for creating the parametric mesh surface, and then the cross-sectional curve group is used to generate a blank surface with parametric characteristics; this blank surface is composed of a single face piece, which can realize parametric design and adjustment, and is helpful to improve the design efficiency and quality of the drawing blank surfaces of various types of stamping covers; it can be completed with the help of any commonly used three-dimensional industrial design software, and only commonly used simple modeling commands such as reference planes, sketches, reference points, grids and fillets are used, and simple and efficient operation steps are provided, which can be applicable to the efficient and high-quality design of the drawing blank surfaces of various stamping covers, and effectively solves the above-mentioned problems existing in the background technology.

[0005] The technical solution of the present invention is: a method for creating a drawing blank surface based on a parameterized mesh surface, comprising the following steps:

[0006] (1) Using a single grid sheet to design the drawing pressing surface;

[0007] (2) Two sets of parametric sketch section lines that are orthogonal and close to the outer contour or inner contour of the product are used to generate the blanking surface, that is, the blanking surface generated by the two sets of orthogonal section lines in the U and V directions is consistent with the contour of the product;

[0008] (3) By setting the parameterized reference plane, sketch, associated points and the height parameters of the blanking surface, the shape and height of the cross-section line group of the generated mesh surface are controlled, thereby controlling the overall height of the blanking surface to ensure the degree of deformation during drawing;

[0009] (4) Set the alignment reference point in the sketch section line group so that the two groups of orthogonal section group lines intersect with zero tolerance to ensure the generation accuracy of the pressing surface.

[0010] In the step (2), in order to better match the contour of the pressing surface with the matching product, intermediate section contour shape control lines are added in the X direction and the Y direction. The single-sided sheet pressing surface generated by such orthogonal section lines better matches the contour of the product, ensures the uniformity of the drawing deformation, and is conducive to eliminating drawing defects such as cracking and wrinkling.

[0011] In the step (3), in order to parameterize the shape and position of the binder surface, 8-10 reference planes are defined as design references for generating a sketch cross-section line group of the binder surface;

[0012] First, according to the drawing process benchmark, three orthogonal reference planes X0, Y0 and Z0 are designed to match the drawing process benchmark; based on the reference planes X0 and Y0, four upright reference planes X1, X2, Y1 and Y2 are designed as the boundary control planes of the left, right, front and back of the pressing surface, and at the same time as the working planes for drawing the sketch section line of the pressing surface; if it is necessary to add intermediate control section lines between the front and rear directions and the left and right directions of the pressing surface, the working planes X3 and Y3 for drawing the intermediate sketch section lines can be added accordingly;

[0013] In the step (3), the height of the sketch cross-section line is controlled by controlling the height parameter to adjust the height of the binder surface so that the drawing depth is moderate;

[0014] First, set a constant variable H0, and establish a reference plane Z1 with an upward or downward offset of H0 relative to the absolute horizontal plane reference Z0 in the drawing height direction; the reference plane Z1 will be used as the height reference for each sketch section line. The size setting of H0 should try to ensure that the position of each sketch section line is above or below the reference plane Z1 to ensure that there is no ambiguity in the generation or adjustment of the pressing surface.

[0015] In the step (3), the drawing uniformity of the blank pressing surface is ensured by controlling the geometric structure of the parameterized sketch cross-section line group; the parameterized sketch cross-section lines for generating the blank pressing surface are all composed of straight lines and circular arcs, and the order of each cross-section curve segment is ≤2, which reduces the geometric rigidity of the cross-section line group and naturally ensures the overall smoothness of the drawing blank pressing surface.

[0016] In the step (3), according to design specifications and experience, by controlling the size of the fillet radius in the sketch, the minimum radius of curvature of the pressing surface is controlled to be ≥ the minimum radius of the fillet in the sketch.

[0017] In the step (4), in order to ensure that the cross-section line groups generated by the left, right, front, rear and middle pressing surfaces intersect and match with geometric zero tolerance at the four outer contour corner points and the middle position, two points can be defined by associating the two end points of the previously drawn sketch cross-section line group. When drawing the sketch cross-section line group orthogonal to it, the outer contour end points are respectively coincident with the two points defined above or intersect and match at the middle position, that is, the generation accuracy of the pressing surface is ensured by the zero tolerance intersection of the orthogonal cross-section group lines.

[0018] The beneficial effects of the present invention are as follows: in commonly used 3D modeling software, the parametric function of the sketch is applied to draw the cross-section curve group required for creating a parametric mesh surface, and then a pressing surface with parametric characteristics is generated from the cross-section curve group; this pressing surface is composed of a single face piece, which can realize parametric design and adjustment, and helps to improve the design efficiency and quality of the drawing pressing surfaces of various types of stamping covers; it can be completed with the help of any currently commonly used 3D industrial design software, and only commonly used simple modeling commands such as reference planes, sketches, reference points, grids and fillets are used, and simple and efficient operation steps are provided, which can be suitable for the efficient and high-quality design of the drawing pressing surfaces of various stamping covers. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the digital model diagram of the original product of the background technology of the present invention;

[0020] Figure 2 It is a digital model diagram of the drawing process of the present invention using a single-sided sheet mesh surface as a pressing surface;

[0021] Figure 3 This is a diagram for explaining the supplementary terminology of the drawn part process of the present invention;

[0022] Figure 4 It is a two-dimensional stamping method diagram of the drawn part of the present invention;

[0023] Figure 5-1 This is the original product digital model of the truck rear enclosure;

[0024] Figure 5-2 It is the original product digital model drawing of the hood 1;

[0025] Figure 5-3 It is the original product digital model of the hood 2;

[0026] Figure 5-4 This is a drawing of the traditional method of drawing and pressing the material surface of the rear enclosure of a truck in the background technology;

[0027] Figure 5-5 It is a drawing of the material surface of the conventional method of drawing down the hood 1 of the background technology;

[0028] Figure 5-6 It is a drawing of the material surface of the conventional method of drawing down the hood 2 of the background technology;

[0029] Figure 5-7 This is a drawing and pressing surface diagram of the rear side of the truck under the method of the present invention;

[0030] Figure 5-8 This is a drawing and pressing surface diagram of the lower hood 1 according to the method of the present invention;

[0031] Figure 5-9 This is a drawing and pressing surface diagram of the lower hood 2 according to the method of the present invention;

[0032] Figure 6 The present invention sets 8 reference planes;

[0033] Figure 7 It is the process surface diagram of the punch based on which the pressing surface of the present invention is designed;

[0034] Figure 8 It is a single sketch cross-section line drawing of the present invention;

[0035] Fig. 9 These are two groups of orthogonal sketch section line group drawings completed by the present invention;

[0036] Fig.10 It is a drawing of the pressing surface completed by the present invention;

[0037] Fig.11 The present invention is to extract the contour line diagram of the punch;

[0038] Fig.12 The present invention generates the die fillet and blank holder diagram;

[0039] Fig.13 The present invention generates the engine hood pressing surface diagram based on the intermediate sketch section group. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the invention implementation cases clearer, the technical solutions in the implementation cases of the present invention will be clearly and completely described below in conjunction with the drawings in the implementation cases. Obviously, the implementation cases described are only a small part of the implementation cases of the present invention, rather than all the implementation cases. Based on the implementation cases in the present invention, all other implementation cases obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] A method for creating a drawing blank surface based on a parameterized mesh surface, which uses a single mesh sheet to design the drawing blank surface, includes the following steps:

[0042] (1) Two sets of parametric sketch section lines that are orthogonal and approximate the outer contour or inner contour of the product are used to generate the blanking surface, that is, the two sets of orthogonal section lines in the U and V directions are matched to match the blanking surface and the contour of the product;

[0043] (2) By setting the parameterized reference plane, sketch, associated points and the height parameters of the blanking surface, the shape and height of the cross-section line group of the generated mesh surface are controlled, thereby controlling the overall height of the blanking surface to ensure the degree of deformation during drawing;

[0044] (3) Set the alignment reference point in the sketch section line group so that the two groups of orthogonal section group lines intersect with zero tolerance to ensure the generation accuracy of the pressing surface.

[0045] In the step (1), in order to better match the contour of the pressing surface with the matching product, intermediate section contour shape control lines are added in the X direction and the Y direction. The single-sided sheet pressing surface generated by such orthogonal section lines better matches the contour of the product, ensures the uniformity of the drawing deformation, and is conducive to eliminating drawing defects such as cracking and wrinkling.

[0046] In the step (2), in order to parameterize the shape and position of the binder surface, 8-10 reference planes are defined as design references for the sketch cross-section line group for generating the binder surface;

[0047] First, according to the drawing process benchmark, three orthogonal reference planes X0, Y0 and Z0 are designed to match the drawing process benchmark; based on the reference planes X0 and Y0, four upright reference planes X1, X2, Y1 and Y2 are designed as the boundary control planes of the left, right, front and back of the pressing surface, and at the same time as the working planes for drawing the sketch section line of the pressing surface; if it is necessary to add intermediate control section lines between the front and rear directions and the left and right directions of the pressing surface, the working planes X3 and Y3 for drawing the intermediate sketch section lines can be added accordingly;

[0048] In the step (2), the height of the sketch cross-section line is controlled by controlling the height parameter to adjust the height of the binder surface so that the drawing depth is moderate;

[0049] First, set a constant variable H0, and establish a reference plane Z1 with an upward or downward offset of H0 relative to the absolute horizontal plane reference Z0 in the drawing height direction; the reference plane Z1 will be used as the height reference for each sketch section line. The size setting of H0 should try to ensure that the position of each sketch section line is above or below the reference plane Z1 to ensure that there is no ambiguity in the generation or adjustment of the pressing surface.

[0050] In the step (2), the drawing uniformity of the blank pressing surface is ensured by controlling the geometric structure of the parameterized sketch cross-section line group; the parameterized sketch cross-section lines for generating the blank pressing surface are all composed of straight lines and circular arcs, and the order of each cross-section curve segment is ≤2, which reduces the geometric rigidity of the cross-section line group and naturally ensures the overall smoothness of the drawing blank pressing surface.

[0051] In the step (2), according to design specifications and experience, by controlling the size of the fillet radius in the sketch, the minimum radius of curvature of the pressing surface is controlled to be ≥ the minimum radius of the fillet in the sketch.

[0052] In the step (3), in order to ensure that the cross-section line groups generated by the left, right, front, rear and middle pressing surfaces intersect and match with zero geometric tolerance at the four outer contour corner points and the middle position, two points can be defined by associating the two end points of the previously drawn sketch cross-section line group. When drawing the sketch cross-section line group orthogonal to it, the outer contour end points are respectively coincident with the two points defined above or intersect and match at the middle position, that is, the generation accuracy of the pressing surface is ensured by the zero tolerance intersection of the orthogonal cross-section group lines.

[0053] 1. Terms related to the patent method

[0054] In order to better describe the patented method, the main terms involved in the drawing press surface design will be explained according to the process design steps of the drawn part.

[0055] 1) Product digital model: The three-dimensional digitally defined product provided by the customer (such as Figure 1 , Figure 5-1 to Figure 5-3 ).

[0056] 2) Drawing process digital model: a three-dimensional digital model that expresses the drawn part (such as Figure 2 )

[0057] 3) Internal hole filling: Complete the holes that must be filled in the drawing model (such as Figure 3 )

[0058] 4) Process extension part: In order to meet the needs of subsequent processes, the smooth extension part of the original product surface (including the expansion of flanged and shaped structural shapes) (such as Figure 3 ).

[0059] 5) Process vertical wall part: the vertical surface formed by the drawing part (such as Figure 3 ).

[0060] 6) Punch fillet: The rounded part between the process extension part and the process wall (such as Figure 3 ).

[0061] 7) Pressing surface: The curved surface used for pressing during drawing. After the rounding operation, the pressing surface will become an annular curved surface - the blank holder (such as Figure 3 ).

[0062] 8) Punch contour line: the intersection line between the process wall part and the pressing surface (becomes a virtual intersection line after the subsequent rounding operation); the punch contour line is extracted before the blank holder is generated (such as Figure 3 ).

[0063] 9) Blank holding ring: The annular surface formed by the blank holding surface and the process wall rounding operation (such as Figure 3 ).

[0064] 10) Die fillet: The rounded part between the process wall and the pressing surface (such as Figure 3 )

[0065] 11) Drawbead center line: The center position line required to construct the drawbead on the blanking surface (used to generate equivalent ribs for forming simulation and actual ribs for die drawing) (such as Figure 3 ).

[0066] 2. Introduction to the traditional drawing press surface design method and characteristics

[0067] 1. There are two methods for traditional drawing press surface design.

[0068] 1) Three-dimensional modeling method of drawing press surface based on stamping method

[0069] First, experienced technicians complete the two-dimensional stamping method diagram of the drawn part (such as Figure 4 ), the two-dimensional stamping method diagram of the drawn part contains the four outer boundaries of the blanking surface (i.e., the front, back, left, and right blanking surface lines) to constrain the outer contour of the blanking surface. Then, the three-dimensional modeling personnel follow the design principles of the blanking surface in the above technical background, use the two-dimensional stamping method diagram of the drawn part as a reference for modeling constraints, design and adjust the shape and position of the blanking surface line in the three-dimensional software, complete multiple local blanking surface patches, and then complete the design of the entire blanking surface through stitching and transition connection. The completed blanking surface is similar to the one in Figure 5 Figure 5-4 , Figure 5-5 , Figure 5-6 As shown, it is made of multiple sheets sewn together.

[0070] 2) A three-dimensional modeling method for directly completing the blanking surface of the drawn part based on the original product digital model

[0071] This method omits the two-dimensional stamping process diagram of the drawn part. Experienced process personnel follow the design principles of the blanking surface in the above technical background and directly complete multiple local blanking surface pieces in the three-dimensional design software. Then, the whole blanking surface design is completed through stitching and transition connection. The completed blanking surface is similar to that in Figure 5. Figure 5-4 , Figure 5-5 , Figure 5-6 As shown, it is made of multiple sheets sewn together.

[0072] 2. Characteristics and shortcomings of traditional drawing press surface design methods

[0073] 1) The traditional drawing blanking surface design method rarely uses the sketch module to draw the production section line of the blanking surface. Generally, a non-parametric method is used to generate multiple face pieces, and then the blanking surface is obtained by the splicing method. In this way, the surface boundary connection tolerance accuracy and surface smoothness are difficult to control.

[0074] 2) If the surface boundary connection tolerance accuracy of the multi-faceted sheet is not enough or the surface boundary connection smoothness is poor, it will cause difficulty or failure in the generation of 3D drawbeads.

[0075] 3) Since most of the designs are non-parametric, the minimum curvature radius of the pressing surface cannot be "explicitly" controlled (the minimum curvature radius of the pressing surface produced by this patent depends on the minimum fillet radius in the cross-section line group. By controlling the size of the sketch, the minimum curvature radius of the pressing surface can be "explicitly" controlled to be ≥ the minimum fillet radius in the sketch).

[0076] 4) Traditional methods use many steps and modeling commands, and the design and adjustment are very cumbersome and inefficient.

[0077] 3. Implementation steps of the present invention

[0078] After the stamping direction and orientation are determined, the following contents are carried out in order: internal hole filling, process extension (including the expansion of flanging and shaping areas), process wall part, punch fillet, pressing surface, punch contour line, die fillet, drawbead center line, etc. Here, a certain car engine hood outer panel is taken as an example. It is assumed that the design steps before the pressing surface have been completed, that is, the punch process supplement (such as Figure 7 As shown), on this basis, the design steps of the binder surface of the present invention are introduced as follows:

[0079] 1) Define 8-10 reference planes as the design reference for the pressing surface

[0080] First, design three orthogonal reference planes X0, Y0, and Z0 according to the drawing process reference. Based on the reference planes X0 and Y0, design four upright reference planes X1, X2, Y1, and Y2 as the boundary control planes for the left, right, front, and back of the pressing surface, and at the same time as the working planes for drawing the section lines of the pressing surface sketch. When the product is symmetrical left and right or front and back, you can use the symmetry to draw only planes X1 or X2, Y1, or Y2. If you need to add a drawing plane for the intermediate control section line between the front and rear directions and (or) the left and right directions of the pressing surface, generally select planes X0 and (or) Y0 (such as Figure 6 and Fig.13 as shown).

[0081] In order to parametrically define a reference plane that controls the height of the drawing press, first set a constant variable H0, and establish a reference plane Z1 with an upward or downward offset of H0 relative to the absolute horizontal plane reference Z0 in the drawing height direction. Z1 will be used as the height dimension reference for drawing the section line of the press sketch.

[0082] 2) Draw 4-6 groups of sketch section lines (such as Figure 8 and Fig. 9 )

[0083] Draw sketch section line groups on each sketch placement surface. The order can be selected by the designer. Set reference points at both ends of the sketch section group line drawn first. The endpoints of the sketch section group line drawn later and perpendicular to it should coincide with the set reference points to ensure the geometric zero tolerance accuracy requirements when generating the mesh surface. In addition, each sketch section group line should match the front, back, left, and right (including the middle) contours of the product as much as possible. The specific steps are as follows:

[0084] a. Take Z1 as the sketch height reference; draw the sketch section group line on the reference plane X1 as the left binder surface boundary control line. In order to parameterize the drawing depth, use H0 as the driving parameter to control the overall height position of the left binder surface boundary line (such as Figure 8 ).

[0085] b. Draw the right pressing surface boundary line in the same way as step a. If the product is bilaterally symmetrical, the reference plane X0 can be used as the mirror plane, and the right pressing surface boundary line can be obtained by mirroring the left pressing surface boundary line, or the left pressing surface boundary line can be projected onto the reference plane X2 to obtain the right pressing surface cross-section line.

[0086] c. This step is optional to control the shape of the middle position in the X direction (refer to Fig.13 ).

[0087] Take Z1 as the height reference, add the middle pressing surface sketch control line group between the left and right pressing surface boundary lines. Figure 1 It is usually drawn on the reference plane X0, and its shape matches the X0 cross-section shape of the product. H0 is used as the driving parameter to control the overall height position of the cross-section line group of the intermediate pressing surface.

[0088] d. With Z1 as the height reference, draw the sketch section group line on the reference plane Y1 as the front blanking surface section line group (Y positive direction). In order to parametrically control the drawing depth, use H0 as the driving parameter to control the height position of the left blanking surface side section line group, and fit the two ends of the sketch line group to the endpoints of the left and right blanking surface boundary lines to intersect the orthogonal section line group (0 tolerance).

[0089] e. With Z1 as the height reference, draw the sketch section group line on the reference plane Y2 as the rear binder surface section line group (Y negative direction). In order to parametrically control the drawing depth, use H0 as the driving parameter to control the height position of the left binder surface section line group, and match the two ends of the sketch line group to the endpoints of the left and right binder surface section line groups. If the product is symmetrical from front to back, the boundary line of the rear binder surface can be obtained using the symmetry method

[0090] f. This step is optional to control the shape of the middle section line group in the Y direction of the binder surface.

[0091] Same as step c, with Z1 as the height reference, add the middle binder surface sketch control line group between the front and rear binder surface edge section line groups. Figure 1 Generally drawn on the reference plane Y0, the shape and product are consistent with the Y0 section shape. Use H0 as the driving parameter to control the overall height of the middle binder surface section line group, and match the two ends of the sketch section line group to the endpoints of the left and right binder surface section line groups.

[0092] Complete the sketch line group as Fig. 9 As shown; if you need to add an intermediate sketch section line group, you can refer to Fig.13 .

[0093] 3) Use the mesh command to generate a parameterized pressing surface

[0094] Use the mesh generation command in common software to generate the parameterized binder surface. The operation steps may vary in different software. Fig.10 .

[0095] 4) Adjust the sketch parameters to control the degree of fit between the pressing surface and the product contour.

[0096] Adjust the sketch parameters so that the pressing surface generated by the sketch curve meets the uniformity of drawing and controls the occurrence of wrinkling and cracking.

[0097] 5) Use the parameter H0 of the pressure surface position control surface to adjust the overall depth of the drawn part.

[0098] Adjust the setting value of H0 and change the overall height position of the pressing surface to obtain a suitable overall depth of the drawn part, which ensures the necessary rigidity, strength and plastic freezing while ensuring no risk of cracking.

[0099] 6) Parameterized minimum radius control of the pressing surface

[0100] Adjust the fillet size in the sketch section line group to ensure that the surface radius on the blank holder surface is larger than the minimum required value (such as company specifications or empirical values).

[0101] 7) Extract the punch contour line (used for the lower die parting design of the drawing punch and the blank holder), such as Fig.11 .

[0102] 8) Generate blank holder

[0103] After the pressing surface and the process vertical surface are rounded, the die radius and the annular pressure ring surface (such as Fig.12 ).

[0104] 9) Generate the center line of the drawbead on the blank holder.

[0105] After completing the above design, you can perform a simulation analysis of the drawing process. If you find that the drawing press surface design has defects or deficiencies, you can adjust the relevant parameters according to the above steps to obtain a new press surface process plan. If necessary, perform a simulation analysis of the drawing process again and continue to adjust the relevant parameters until the ideal press surface is obtained.

[0106] 6. Technical features of this patent

[0107] 1. The design steps of this special feature are simple, and only basic modeling commands such as plane, sketch, grid and fillet are needed; the design of the pressing surface is fully parameterized. It is convenient to quickly design and adjust the optimized pressing surface with high efficiency.

[0108] 2. The mesh command commonly used in industrial software is used to generate a single patch as the pressing surface. The operation is simple, and the smoothness and tolerance accuracy of the internal surface of the obtained patch are easy to ensure, avoiding the problem of insufficient tolerance accuracy or poor smoothness of surface boundary connection of multi-patch pressing surfaces, thereby improving the design quality of the pressing surface and ensuring the stable generation of subsequent 3D drawbeads.

[0109] 3) Due to the use of parametric sketch design, the minimum curvature radius of the binder surface can be "explicitly" controlled. The binder surface produced by this patent is a mesh surface of a single face, and its minimum curvature radius depends on the minimum fillet radius in the cross-sectional line group that generates it. Therefore, according to design specifications and experience, by controlling the arc radius in the sketch, the minimum curvature radius of the binder surface can be controlled to be ≥ the minimum radius of the fillet in the sketch cross-sectional line group.

[0110] 4) This patented method is applicable to the rapid design and process verification of the drawing pressing surface scheme for most of the cover parts drawing processes.

Claims

1. A method for creating a drawing blank surface based on a parameterized mesh surface, characterized in that The following steps are involved: (1) Using a single grid sheet to design the drawing pressing surface; (2) Two sets of parametric sketch section line groups that are orthogonal and close to the outer contour or inner contour of the product are used to generate the blanking surface, that is, the blanking surface generated by the two sets of orthogonal section lines in the U and V directions matches the contour of the product; in order to better match the blanking surface with the contour of the matching product, the middle section contour shape control line is added in the X direction and the Y direction. The single-sided sheet blanking surface generated by such orthogonal section lines better matches the contour of the product, ensures the uniformity of drawing deformation, and is conducive to eliminating the drawing defects of cracking and wrinkling; (3) By setting the parameterized reference plane, sketch, associated points and the height parameters of the blanking surface, the shape and height of the cross-section line group of the generated mesh surface are controlled, thereby controlling the overall height of the blanking surface to ensure the degree of deformation during drawing; (4) Set the alignment reference point in the sketch section line group so that the two groups of orthogonal section group lines intersect with zero tolerance to ensure the generation accuracy of the pressing surface.

2. The method for creating a drawing blank surface based on a parameterized mesh surface according to claim 1, characterized in that: In the step (3), in order to parameterize the shape and position of the binder surface, 8-10 reference planes are defined as design references for generating a sketch cross-section line group of the binder surface; First, according to the drawing process datum, three orthogonal datum planes X0, Y0 and Z0 are designed to match the drawing process datum; based on the datum planes X0 and Y0, four upright datum planes X1, X2, Y1 and Y2 are designed as the left, right, front and back boundary control planes of the pressing surface, and at the same time as the working planes for drawing the sketch section line of the pressing surface; if it is necessary to add intermediate control section lines between the front and rear directions and the left and right directions of the pressing surface, corresponding working planes X3 and Y3 for drawing the intermediate sketch section lines are added.

3. The method for creating a drawing blank surface based on a parameterized mesh surface according to claim 2, characterized in that: In the step (3), the height of the sketch cross-section line is controlled by controlling the height parameter to adjust the height of the binder surface so that the drawing depth is moderate; First, set a constant variable H0, and establish a reference plane Z1 with an upward or downward offset of H0 relative to the absolute horizontal plane reference Z0 in the drawing height direction; the reference plane Z1 will be used as the height reference for each sketch section line. The size setting of H0 should try to ensure that the position of each sketch section line is above or below the reference plane Z1 to ensure that there is no ambiguity in the generation or adjustment of the pressing surface.

4. The method for creating a drawing blank surface based on a parameterized mesh surface according to claim 1, characterized in that: In the step (3), the drawing uniformity of the blank pressing surface is ensured by controlling the geometric structure of the parameterized sketch cross-section line group; the parameterized sketch cross-section lines for generating the blank pressing surface are all composed of straight lines and circular arcs, and the order of each cross-section curve segment is ≤2, which reduces the geometric rigidity of the cross-section line group and naturally ensures the overall smoothness of the drawing blank pressing surface.

5. The method for creating a drawing blank surface based on a parameterized mesh surface according to claim 1, characterized in that: In the step (3), according to design specifications and experience, by controlling the size of the fillet radius in the sketch, the minimum radius of curvature of the pressing surface is controlled to be ≥ the minimum radius of the fillet in the sketch.

6. The method for creating a drawing blank surface based on a parameterized mesh surface according to claim 1, characterized in that: In the step (4), in order to ensure that the cross-section line groups generated by the left, right, front, rear and middle pressing surfaces intersect and match with geometric zero tolerance at the four outer contour corner points and the middle position, two points are defined in association with the two end points of the previously drawn sketch cross-section line group. When drawing the sketch cross-section line group orthogonal to it, the outer contour end points are respectively coincident with the two points defined above or intersect and match at the middle position, that is, the generation accuracy of the pressing surface is ensured by the zero tolerance intersection of the orthogonal cross-section group lines.

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