Drawing forming method with composite-shaped drawing sill, die and vehicle body structural part

Abstract

The invention discloses a drawing forming method with a composite-shaped drawing sill, a die and a vehicle body structural part, and belongs to the technical field of metal plate stamping forming. According to the technical scheme, the drawing sill main body structure is arranged on the blank holder management face, the reverse forming rib is arranged on the outer side of the drawing sill, and plate flow is controlled in the drawing process through the composite material control structure, so that the plate generates sufficient plastic tensile deformation; compared with a traditional drawing sill, additional forming resistance is introduced through the reverse forming ribs, springback of parts is effectively reduced, and the size stability is improved; the waste material area is obviously reduced while the material control effect is guaranteed, and the material utilization rate is increased; through reasonable design of geometric parameters of the composite drawing sill, the drawing resistance can be adjusted, the material application range is widened, and the structural strength of the drawing sill and the mold debugging convenience are both considered; the drawing die is suitable for drawing forming of metal plates, and has the technical effects of reducing material cost, reducing die rectification times and improving production stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of stamping of sheet metal, and particularly relates to a drawing forming method, a die and a vehicle body structural component with a composite-shaped drawing sill. BACKGROUND

[0002] The stamping forming of sheet metal is widely used in the development and design of automobile bodies; the stamping forming technology of sheet metal includes drawing forming, shaping and other forming methods; among them, drawing forming is suitable for ordinary steel sheets and low-strength steel, and using drawing forming can effectively reduce the springback of parts and improve the stability of stamping production; in order to improve the material utilization rate, the current stamping process method has been continuously improved in terms of drawing height, management surface size, drawing rib design, etc., and certain effects have been obtained.

[0003] With the further improvement of material utilization rate, drawing sills are used instead of drawing ribs in the forming process, but it is found through practice that the drawing sill lacks the forming resistance on one side compared with the drawing rib, so through CAE simulation and debugging, it is found that it cannot produce enough plastic deformation in the product part, thereby causing the springback of the part to increase, which cannot meet the requirements of the part on the vehicle body for welding matching, and the mold rectification caused by the size unqualified due to springback includes re-making, processing, welding, processing and debugging on the press, etc., which needs to spend about 50,000-100,000 yuan, if multiple parts face the same problem, it will make the mold enterprise benefit decline, and even cause loss; if drawing ribs with greater resistance are used for drawing forming, since the drawing rib has a large width, the material utilization rate is low, if a single sheet of 5mm size is increased on one side for evaluation, for a single sheet of ordinary 1700mm*500mm high-strength steel, the material utilization rate will be reduced by about 2%, which cannot meet the cost control requirements of stamping production. SUMMARY

[0004] To solve the above problems, the present application provides a drawing forming method, a die and a vehicle body structural component with a composite-shaped drawing sill, which combines the advantages of traditional drawing sills and drawing ribs, avoids their respective shortcomings, can realize effective drawing resistance for common drawing forming, improves the material utilization rate, is convenient to debug and develop, and is easy to operate.

[0005] A drawing forming method with a composite-shaped drawing sill is used for the stamping drawing forming of sheet metal, and includes the following steps: in the drawing forming process, a reverse-shaped protruding rib is arranged in the drawing sill to form a composite drawing sill.

[0006] The composite-shaped drawing groove is arranged on the blank holder, and the inflow amount of the sheet metal is controlled during the sheet metal flowing into the forming area, so that sufficient plastic tensile deformation of the sheet metal in the target forming area is generated, thereby improving material utilization and reducing forming springback;

[0007] The blank holder is installed on the lower die seat together with the lower punch, and is driven to move by the lower pad of the press, and the blank holder is provided with the composite-shaped drawing groove;

[0008] In view of the problems that in the existing drawing forming process, the traditional drawing groove control material resistance is insufficient, it is difficult to make the sheet metal produce sufficient plastic tensile deformation, and the use of the drawing rib reduces the material utilization due to the large structure size, the application provides a drawing forming method, a die and a vehicle body structure part with a composite-shaped drawing groove; the reverse-shaped rib is introduced into the drawing groove, so that the drawing groove and the reverse-shaped rib play a synergistic role in the same structure, and the problem that the drawing resistance and the material utilization are difficult to be considered is solved;

[0009] Specifically, in the drawing forming process, the reverse-shaped rib is arranged in the drawing groove structure to form a composite-shaped drawing groove, and the composite drawing groove is arranged on the blank holder; when the sheet metal flows from the blank holder to the forming area during the drawing process, the composite-shaped drawing groove first applies a basic drawing resistance to the sheet metal through the drawing groove body, and the reverse-shaped rib further guides the sheet metal to produce local bending and reverse bending deformation, thereby significantly increasing the material flow resistance; through the synergistic effect of the above structure, the sheet metal obtains more sufficient and stable plastic tensile deformation in the target forming area;

[0010] The technical effects brought by this are: on the one hand, compared with the use of the traditional drawing groove alone, the present application can effectively inhibit the excessive inflow of the sheet metal, reduce the forming springback, and improve the dimensional stability of the part; on the other hand, compared with the forming method using the drawing rib, since the reverse-shaped rib is small in size and concentrated in position, the waste area can be reduced while ensuring the drawing resistance, thereby significantly improving the material utilization; at the same time, the composite-shaped drawing groove is arranged on the blank holder, and the blank holder is driven to move by the lower pad of the press, so that the structure is reasonably arranged.

[0011] The technical solution provided by the application also has the following technical features:

[0012] Preferably, in an embodiment of the application, the metal sheet is placed on the blank holder, the upper punch is driven downward by the press, and the blank holder is closed, and the composite drawing groove is formed, and then the upper punch continues to move downward to complete the drawing process;

[0013] Preferably, in one embodiment of this application, the composite drawing threshold on the blank holder is an upwardly convex drawing threshold, and a reverse forming rib is provided on the outside of the composite drawing threshold. When the upper die and the blank holder are fastened together, the composite-shaped drawing threshold simultaneously stamps the drawing threshold and the reverse forming rib.

[0014] Preferably, in one embodiment of this application, the composite drawing threshold is disposed on the outside of the parting line, and the composite drawing threshold is located near the pressure ring management surface of the parting line, so as to apply stable and adjustable drawing resistance to the sheet metal in the early stage of drawing.

[0015] Preferably, in one embodiment of this application, by adjusting the geometric parameters of the reverse forming rib, the shrinkage line of the drawn sheet is controlled within the transition fillet region of the reverse forming rib, thereby reducing the size of the scrap area while maintaining forming stability.

[0016] Preferably, in one embodiment of this application, during the drawing process, the upper die simultaneously completes the forming of the drawing threshold body and the reverse forming rib during the closing stage of the blank holder, so that the drawing resistance remains continuous and stable throughout the entire drawing stroke.

[0017] Preferably, in one embodiment of this application, the tensile strength of the metal sheet is a predetermined strength range, which is determined by matching material parameters with forming resistance design.

[0018] Preferably, in one embodiment of this application, the tensile strength of the metal sheet is between 290 MPa and 450 MPa.

[0019] Preferably, in one embodiment of this application, the width W1 of the drawing threshold management surface is ≥10mm;

[0020] The drawing threshold height is h1, h1 ≥ 5mm;

[0021] The r-angle of the drawing threshold resistance is r1 ≥ 1.5t, where t is the sheet thickness;

[0022] The angle r of the reverse forming rib is r2≧2mm for round ribs;

[0023] The height of the reverse forming rib, h2 ≥ 3mm;

[0024] Width of the reverse forming rib, W2 ≥ 4mm;

[0025] The parting line gap C is ≥3mm; if W1 cannot meet the minimum design value, then C will be moved as a whole towards the downward punch direction.

[0026] Preferably, in one embodiment of this application, a drawing die with a composite-shaped drawing threshold includes an upper die, a lower die, and a blank holder; the blank holder is disposed on the lower die; the blank holder is provided with a composite-shaped drawing threshold, and the blank holder is used to place the metal sheet; the press drives the upper die to move downward and closes with the blank holder, forming the composite drawing threshold of the metal sheet, and then the upper die continues to move downward to complete the drawing process.

[0027] Preferably, in one embodiment of this application, a vehicle body structural member with a composite-shaped drawing threshold is provided, the vehicle body structural member being manufactured using a drawing forming method with a composite-shaped drawing threshold.

[0028] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0029] Compared with the prior art, the technical solution of this application has achieved the following technical advancements:

[0030] 1. This application combines the drawing threshold and the reverse forming rib in a composite design. In order to solve the problem of insufficient material control resistance and difficulty in suppressing sheet springback of traditional drawing thresholds, the reverse forming rib is set on the outside of the drawing threshold to introduce bending-reverse bending deformation. This overcomes the defect of limited forming resistance of a single drawing threshold and achieves the technical effect of effectively reducing springback and improving the dimensional stability of parts without significantly increasing the complexity of the mold.

[0031] 2. This application forms a composite shape material control structure locally on the blank holder management surface. In order to solve the problem of increased waste area and reduced material utilization when using draw beads, a material control method with the draw bead as the main body and small-sized reverse forming beads as a supplement is adopted. This overcomes the defects of traditional draw beads occupying a large area of ​​blank holder surface and passively enlarging the feeding size. It achieves the technical effect of significantly improving material utilization and reducing raw material costs while ensuring the stability of drawing forming.

[0032] 3. This application realizes the parameterized adjustment of drawing resistance. In order to solve the problem of large differences in material control requirements for metal sheets of different strengths during drawing, the method of adjusting the magnitude of drawing resistance by adjusting the geometric parameters of the reverse forming rib is adopted. This overcomes the defects of the existing technology where the drawing resistance is not adjustable or the adjustment method is singular, and achieves the technical effect of broadening the application range of materials and improving the versatility and repeatability of the process.

[0033] This application also facilitates the structural layout for mold debugging and fitting. In response to the problem of difficult fitting and long debugging cycle of the blank holder caused by the complex material control structure, a method is used to form an upper convex drawing threshold on the blank holder and set it in coordination with the reverse forming rib. This overcomes the defect of the concave material control structure being inconvenient for manual fitting and fine adjustment, and achieves the technical effects of shortening the mold debugging cycle, reducing the mold modification cost, and improving production stability. Attached Figure Description

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0035] Figure 1 This is a schematic diagram of a high-strength steel drawing and forming structure according to an embodiment;

[0036] Figure 2 This is a schematic diagram of a composite drawing threshold structure according to one embodiment;

[0037] Figure 3 This is a schematic diagram of the geometric dimensions of a composite drawing threshold according to one embodiment;

[0038] Components in the diagram:

[0039] 1. Upper die

[0040] 2. Sheet material

[0041] 3. Composite drawing threshold

[0042] 4. Lower punch

[0043] 5. Pressure ring

[0044] 6. Shrinkage line

[0045] 8. Parting line. Detailed Implementation

[0046] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings. These embodiments are only for illustrating this application and are not intended to limit the invention.

[0047] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0050] like Figure 1 , 2 A drawing forming method with a composite-shaped drawing threshold for stamping and drawing metal sheets, characterized by the following steps: in the drawing forming process, a reverse-shaped rib is provided in the drawing threshold to form a composite drawing threshold 3;

[0051] A composite-shaped drawing threshold is provided on the blank holder 5 to control the inflow of the sheet 2 during the process of drawing the sheet 2 into the forming zone, so that the sheet 2 undergoes sufficient plastic tensile deformation in the target forming zone, thereby improving material utilization and reducing forming springback; the sheet 2 is a metal sheet.

[0052] The blank holder 5 and the lower punch 4 are also installed on the lower die base. The blank holder is driven to move by the lower pad of the press. The blank holder has a composite-shaped drawing sill.

[0053] The structural configuration of the composite-shaped drawing threshold 3 and its arrangement in the drawing process: By introducing a reverse-forming rib into the traditional drawing threshold structure, the drawing threshold simultaneously possesses the material control functions of both the drawing threshold and the drawing bead, and is set as a whole in the management surface area of ​​the blank holder 5; the composite-shaped drawing threshold and the blank holder 5 participate in the forming process as a whole, achieving effective control of the inflow of sheet metal 2 without significantly increasing the width of the blank holder surface, thus providing a structural basis for subsequent stable drawing forming;

[0054] During the drawing process, the sheet metal 2 is placed between the lower punch 4 and the blank holder 5. As the press moves, the lower press pad pushes the blank holder 5 to move in a controlled manner relative to the lower punch 4, and the upper die moves downward and closes with the blank holder 5. At this time, the composite shape drawing threshold 3 first applies basic drawing resistance to the sheet metal 2, while the reverse forming ribs therein force the sheet metal to undergo local bending and reverse bending deformation, thereby significantly increasing the material flow resistance. Through the above synergistic effect, the sheet metal 2 is uniformly and controlledly transported to the target area during the drawing process into the forming zone, avoiding local excessive flow.

[0055] Through the above-described implementation methods and working principles, this invention achieves an effective balance between drawing resistance and material utilization during the drawing process. The composite-shaped drawing threshold 3, while ensuring sufficient material control resistance, can stably control the sheet shrinkage line near the composite drawing threshold due to its relatively concentrated structural dimensions, thereby reducing the waste area and improving material utilization. At the same time, sufficient plastic stretching deformation helps reduce forming springback and improve the consistency of part dimensions. The structure in which the blank holder 5 and the lower punch 4 are jointly installed on the lower die base and driven by the lower pad also makes the die debugging and fitting process more convenient, thus improving the stability and operability of the drawing process as a whole.

[0056] Specifically, in one embodiment of this application, a metal sheet is placed on a blank holder, and the upper die 1 is driven downward by a press to close with the blank holder 5. The sheet is then formed by a composite drawing threshold, and the upper die 1 continues to move downward to complete the drawing process.

[0057] The composite drawing threshold on the blank holder is a convex drawing threshold. A reverse forming rib is provided on the outside of the composite drawing threshold. When the upper die and the blank holder are engaged, the composite-shaped drawing threshold simultaneously stamps the drawing threshold and the reverse forming rib.

[0058] Based on the structural feature of a composite drawing threshold including the drawing threshold body and reverse forming ribs on the blank holder management surface, the upper die 1 applies basic drawing resistance and additional bending-reverse bending resistance to the sheet metal simultaneously during the closing and downward movement of the blank holder 5. This overcomes the defects of insufficient resistance in traditional drawing thresholds and excessive occupation of blank holder surface by the drawing ribs. It achieves the technical effect of significantly improving material utilization, reducing forming springback, and facilitating mold debugging and fitting while ensuring forming stability and dimensional accuracy. By reasonably matching the geometric parameters of the composite drawing threshold with the sheet metal strength, it avoids cracking due to excessive resistance or springback due to insufficient resistance.

[0059] Specifically, in one embodiment of this application, the composite drawing threshold 3 is disposed outside the parting line 8, and the composite drawing threshold 3 is close to the management surface of the pressure ring 5 of the parting line 8, which is used to apply stable and adjustable drawing resistance to the sheet 2 in the early stage of drawing; it overcomes the defects of uneven force or unstable material control effect of traditional material control structure in the early stage of drawing, and achieves the technical effect of effectively suppressing the excessively fast flow of sheet material in the early stage of the entire drawing process, improving the stress state of the material, and improving the forming consistency and dimensional stability; it solves the problem of delayed material control intervention and difficulty in stabilizing the instantaneous inflow of material when the sheet 2 enters the forming zone in the early stage of drawing.

[0060] Specifically, in one embodiment of this application, by adjusting the geometric parameters of the reverse forming rib, the shrinkage line 6 of the drawn sheet is controlled within the transition rounded area of ​​the reverse forming rib, thereby reducing the size of the scrap area while maintaining forming stability. This overcomes the defects of shrinkage line drift and difficulty in accurate prediction in traditional material control structures, and achieves the technical effect of effectively reducing the size of the scrap area, improving material utilization, and enhancing process controllability while ensuring forming stability and forming quality.

[0061] Specifically, in one embodiment of this application, during the drawing process, the upper die 1 simultaneously completes the forming of the drawing threshold body and the reverse forming rib during the closing stage of the blank holder 5, so that the drawing resistance remains continuous and stable throughout the entire drawing stroke; overcoming the defects of different material control structures taking effect in stages and unstable resistance connection in the prior art, and achieving the technical effect of maintaining continuous and stable drawing resistance throughout the entire drawing stroke.

[0062] Specifically, in one embodiment of this application, the tensile strength of the metal sheet is a predetermined strength range, which is determined by matching material parameters with forming resistance. This overcomes the shortcomings of the prior art, such as the disconnect between material control structure and material properties and poor process adaptability, and achieves the technical effects of stabilizing forming quality, reducing springback and reducing forming defects while broadening the application range of materials.

[0063] Specifically, in one embodiment of this application, the tensile strength of the metal sheet is between 290 MPa and 450 MPa, which can meet the production needs of most workpieces.

[0064] Specifically, in one embodiment of this application, such as Figure 3 The width of the drawing threshold management surface W1 is ≥10mm;

[0065] The drawing threshold height is h1, h1 ≥ 5mm;

[0066] The r-angle of the drawing threshold resistance, r1≧1.5t, where t is the sheet thickness;

[0067] The angle r of the reverse forming rib is r2≧2mm for round ribs;

[0068] The height of the reverse forming rib, h2 ≥ 3mm;

[0069] Width of the reverse forming rib, W2 ≥ 4mm;

[0070] The parting line gap C is ≥3mm; if W1 cannot meet the minimum design value, then C will be moved downwards towards the punch.

[0071] This application provides a feasible technical solution for drawing with a composite shape threshold.

[0072] Specifically, in one embodiment of this application, a drawing forming die with a composite-shaped drawing threshold is provided, employing a drawing forming method with a composite-shaped drawing threshold. The method includes an upper die, a lower die, and a blank holder. The blank holder is disposed on the lower die. A composite-shaped drawing threshold is provided on the blank holder, which is used to hold the metal sheet. The press drives the upper die downwards, closing it with the blank holder, thus forming the composite drawing threshold of the metal sheet. Subsequently, the upper die continues to descend, completing the drawing process. This method solves the problem that existing drawing forming dies cannot meet the requirements for composite drawing threshold forming in terms of material control capability, forming stability, and process consistency. It achieves the technical effect of fully utilizing the composite drawing threshold's material control effect throughout the entire drawing stroke, high repeatability of the forming process, and stable product dimensional accuracy and consistency.

[0073] Specifically, in one embodiment of this application, a vehicle body structural component with a composite-shaped drawing threshold is provided. The vehicle body structural component is manufactured using a drawing forming method with a composite-shaped drawing threshold, which can obtain a vehicle body structural component that meets the requirements, and has high material utilization and stable process control.

[0074] Specifically, in one embodiment of this application, there are generally two ways to form metal sheets: one is drawing, and the other is shaping. If forming can eliminate forming defects such as wrinkling and cracking, it can be prioritized for stamping process layout, significantly improving material utilization. However, for certain parts with special shapes or material strengths, forming may lead to wrinkling, significant springback, and difficulty in compensation. Furthermore, errors in material feeding or die clearance can cause unstable product dimensions, resulting in scrapped parts. Drawing, on the other hand, can more effectively avoid wrinkling and cracking, and significantly reduce springback. However, this method tends to result in low material utilization, leading to excessively high raw material procurement costs. To improve material utilization in drawing, a drawing threshold is an effective method. However, due to its geometric characteristics, this method has limited control over material flow resistance and cannot achieve sufficient material resistance control to improve material utilization. Therefore, this invention improves the traditional drawing threshold by adding reverse-forming ribs to increase forming resistance, naming it a composite drawing threshold. Its characteristic indicators are as follows:

[0075] The width of the drawing threshold management surface is W1, W1 ≥ 10mm, which is the same as that of a traditional drawing threshold.

[0076] The drawing threshold height is h1, h1 ≥ 5mm; traditional drawing thresholds have no parameters.

[0077] The r-angle of the drawing threshold resistance is r1 ≥ 1.5t, where t is the sheet thickness. Traditional drawing thresholds have no parameters.

[0078] For reverse forming ribs, if the rib is round, r2 ≥ 2mm. Traditional drawing sills do not have this feature.

[0079] The height of the reverse forming rib is h2 ≥ 3 mm, a feature not found in traditional drawing thresholds.

[0080] The width of the reverse forming rib is W2≧4mm, a feature not found in traditional drawing thresholds;

[0081] The parting line gap C is ≥3mm. If W1 cannot meet the minimum design value, C needs to be moved downwards towards the punch to ensure the strength of the drawing threshold. Traditional drawing thresholds do not have this parameter.

[0082] like Figure 1 As shown, the present invention provides a method for drawing and forming metal sheets, applicable to the field of metal stamping, comprising the following steps:

[0083] 1. Determine the stamping process scheme based on the geometric characteristics of the part. If a drawing process is used, the method of this invention can be adopted.

[0084] 2. Determine the strength grade of the sheet material. This invention is mainly used for tensile strengths between 290MPa and 450MPa; for those exceeding this range, CAE verification analysis is used.

[0085] 3. The width of the composite drawing threshold management surface invented is usually 10mm. If a smaller size is used, it is difficult to guarantee the strength of the drawing threshold. If the parting line can move to the inside of the lower punch, the management surface will move with the parting line to the lower punch, thereby further improving the material utilization rate.

[0086] 4. The height of the invented drawing threshold is usually 5mm. This height is suitable for the drawing of most steel plates. If the height is increased further, the resistance of the drawing threshold can be increased, which makes it easier to adjust the flow rate of the forming process, but it also increases the risk of drawing threshold breakage.

[0087] 5. The drawing threshold r-angle of the invention is usually not less than 1.5 times the thickness of the sheet metal. If the r-angle is too small, the wear of the r-angle will be significantly increased. In addition, due to the rapid change of geometry at the r-angle and the high strength of the sheet metal, the sheet metal cannot follow the shape of the die due to the bending moment after the blank holder is engaged, and a certain degree of bending will be formed. This will affect the fit of the blank holder's blank holder surface. At the same time, due to the excessive bending and reverse bending effect during the drawing process, the CAE analysis and the actual debugging will differ, resulting in the CAE analysis being unable to effectively guide the debugging process.

[0088] 6. The invented drawing threshold reverse forming rib is relatively small, generally with a width of no more than 5mm and a height of no more than 4mm. The resistance is adjusted by the size of r2, thereby compensating for the insufficient resistance of the drawing threshold.

[0089] 7. Because the reverse forming rib has smaller geometric features, the shrinkage line of the sheet material of this composite drawing sill is ultimately controlled at the r-angle of the reverse forming rib compared to the drawing rib. It can usually save about 5mm of sheet material compared to the method using drawing rib, which has a great advantage in terms of material utilization.

[0090] Specifically, in one embodiment of this application, the present invention discloses a composite drawing threshold and forming process that can improve material utilization. This method addresses the issue that traditional drawing thresholds, due to their low drawing resistance, cannot effectively reduce material flow during the drawing process, resulting in insufficient stretching of the product. The invention provides a composite drawing threshold that effectively reduces material flow. This method combines the characteristics of a drawing threshold and a draw bead, positioned outside the parting line. A convex drawing threshold is used on the management surface of the blank holder near the parting line, facilitating the fitting of the blank holder surface. Micro-draw beads are used in the recessed area outside the drawing threshold, forming a composite drawing threshold. This method avoids the problem that traditional drawing thresholds alone cannot generate sufficiently strong drawing resistance, while draw beads alone result in a large area being placed on the blank holder surface, ultimately being cut off as waste, leading to low material utilization. This method achieves the goals of reducing material flow, significantly improving material utilization, and ensuring effective fitting of the management surface.

[0091] 1. The drawing process is adopted. The upper die is a concave die, referred to as the upper concave die, and the lower die is a punch, referred to as the lower punch. The blank holder 5 and the lower punch 4 are also installed on the lower die base. The blank holder is driven to move by the lower pad of the press. The blank holder has a composite-shaped drawing threshold. The metal sheet is placed on the blank holder. The upper die is driven to move downward by the press and closes with the blank holder. The composite drawing threshold is used for forming. Then the upper die continues to move downward to complete the drawing process.

[0092] 2. The composite drawing threshold on the blank holder is a convex drawing threshold. A reverse forming rib is designed on the outside of the drawing threshold. When the upper die and the blank holder are fastened together, the composite-shaped drawing threshold simultaneously stamps the drawing threshold and the reverse forming rib.

[0093] 3. The width of the composite drawing threshold management surface invented is usually 10mm. If a smaller size is used, it is difficult to guarantee the strength of the drawing threshold. If the parting line can move to the inside of the lower punch, the management surface will move to the lower punch along with the parting line, thereby further improving the material utilization rate.

[0094] 4. The height of the invented drawing threshold is usually 5mm. This height is suitable for drawing most metal sheets with tensile strength below 340MPa. If the height is increased further, the resistance of the drawing threshold can be increased, which makes it easier to adjust the flow rate of the forming process, but it also increases the risk of drawing threshold breakage.

[0095] 5. The drawing threshold r-angle of the invention is usually not less than 1.5 times the thickness of the sheet metal. If the r-angle is too small, the wear of the r-angle will be significantly increased. In addition, due to the rapid change of geometry at the r-angle and the high strength of the sheet metal, the sheet metal cannot follow the shape of the die due to the bending moment after the blank holder is engaged, and a certain degree of bending will be formed. This will affect the fit of the blank holder's blank holder surface. At the same time, due to the excessive bending and reverse bending effect during the drawing process, the CAE analysis and the actual debugging will differ, resulting in the CAE analysis being unable to effectively guide the debugging process.

[0096] 6. The invented drawing threshold reverse forming rib is relatively small, generally with a width of no more than 5mm and a height of no more than 4mm. The resistance is adjusted by the size of r2, thereby compensating for the insufficient resistance of the drawing threshold.

[0097] 7. Because the reverse forming rib has smaller geometric features, the shrinkage line of the sheet material of this composite drawing sill is ultimately controlled at the r-angle of the reverse forming rib compared to the drawing rib. It can usually save about 5mm of sheet material compared to the method using drawing rib, which has a great advantage in terms of material utilization.

[0098] Specifically, in one embodiment of this application, the present invention firstly uses an upper convex drawing threshold near the parting line based on the design principle of the drawing threshold. The advantage of this method is that, since the mold adopts a single-action forming method, that is, an upper concave mold, a lower convex mold, and a pressure ring placed on the lower convex mold side, the upper convex drawing threshold designed on the pressure ring facilitates the fitter's grinding and fitting of the management surface. Otherwise, if it is designed as a lower concave type, it is not convenient for the fitter's tools to grind and fit.

[0099] Specifically, in one embodiment of this application, the second aspect of the invention is to design a reverse forming concave rib on the side of the drawing threshold. This concave rib draws upon the working principle of the drawing bead and can be designed as a semi-circular concave rib according to the strength level of the sheet metal. Its main function is to increase the forming resistance of the drawing threshold by means of the reverse forming concave rib when the drawing threshold is insufficient to provide sufficient drawing resistance, thereby effectively controlling the material flow. The reverse forming concave rib is adjustable in terms of material control, and the shrinkage line of the sheet metal after drawing can be controlled at the r-angle of the reverse forming concave rib, thereby optimizing the material utilization rate.

[0100] Specifically, in one embodiment of this application, the second aspect of the invention lies in ensuring the strength of the composite drawing threshold through reasonable parameter design. To control the proper flow of material and optimize material utilization, the drawing threshold combined with inverse forming ribs effectively achieves the above objectives. However, due to the influence of the geometry of the inverse forming ribs, the resistance caused by the geometric characteristics resulting from material flow during the drawing process is very large, which may affect the strength of the drawing threshold. This invention ensures its strength by reasonably designing the geometric parameters.

[0101] Specifically, in one embodiment of this application, such as Figure 3 The geometric characteristics of the composite drawing threshold are as follows:

[0102] The width of the drawing threshold management surface W1 is ≥10mm

[0103] Drawing threshold height h1, h1 ≥ 5mm

[0104] The draw threshold resistance angle r1 ≥ 1.5t, where t is the sheet thickness.

[0105] For reverse forming ribs, if the rib is round, r2 ≥ 2mm;

[0106] Reverse forming rib height, h2≧3mm

[0107] Width of reverse forming rib, W2≧4mm

[0108] The parting line gap C is ≥3mm. If W1 cannot meet the minimum design value, C needs to be moved downwards towards the punch to ensure the drawing threshold strength.

[0109] In summary, this invention aims to solve the problem of insufficient material control resistance in the drawing threshold and low utilization rate of draw beads in existing sheet metal drawing processes. Addressing the technical contradictions of traditional drawing thresholds failing to induce sufficient plastic stretching in the sheet metal during forming, leading to increased springback and insufficient dimensional accuracy, and the significant increase in scrap area, material costs, and mold modification costs due to the larger structural dimensions associated with draw beads, this invention proposes a drawing forming method, mold, and body structural component with a composite-shaped drawing threshold. This is achieved by placing the drawing threshold near the parting line on the blank holder. The main structure of the sill is further reinforced with anti-forming ribs on its outer side. This allows the sheet metal to undergo bending-reverse bending deformation introduced by the sill forming and anti-forming ribs during the drawing process, thereby effectively increasing the drawing resistance without significantly expanding the material control area. Through the rational design of the geometric parameters of the composite sill, the sheet metal shrinkage line can be stably controlled within the anti-forming rib transition area, enabling precise adjustment of the material inflow. This solution effectively reduces springback, improves part dimensional consistency, and significantly increases material utilization while ensuring forming quality and structural strength, demonstrating good process adaptability and industrial application value.

[0110] This application, by designing a composite feature with a drawing threshold and a reverse forming rib on the blank holder, can generate sufficient drawing resistance. At the same time, due to the small feature geometry, it can significantly improve material utilization compared to traditional drawing ribs. It solves the problem of simultaneously providing drawing resistance and improving material utilization. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0111] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A drawing forming method with a composite-shaped drawing threshold, used for stamping and drawing forming of metal sheets, characterized in that, The process includes the following steps: In the drawing process, a reverse-forming rib is provided in the drawing threshold to form a composite drawing threshold; A composite drawing threshold is set on the blank holder (5) to control the flow rate of the sheet material (2) during the process of drawing it into the forming area, so that the sheet material can generate sufficient plastic tensile deformation in the target forming area, thereby improving the material utilization rate while reducing forming springback. The blank holder (5) and the lower punch (4) are also installed on the lower die base. The blank holder is driven to move by the lower pad of the press. The blank holder has a composite-shaped drawing sill.

2. The drawing forming method with a composite shape drawing threshold as described in claim 1, characterized in that, The metal sheet is placed on the blank holder, and the upper die (1) is driven down by the press to close with the blank holder (5). It is formed by the composite drawing threshold. Then the upper die (1) continues to move down to complete the drawing process. The composite drawing threshold on the blank holder is a convex drawing threshold. A reverse forming rib is provided on the outside of the composite drawing threshold. When the upper die and the blank holder are engaged, the composite-shaped drawing threshold simultaneously stamps the drawing threshold and the reverse forming rib.

3. The drawing forming method with a composite shape drawing threshold as described in claim 2, characterized in that, The composite drawing threshold (3) is located outside the parting line (8) and is close to the management surface of the pressure ring (5) of the parting line (8), so as to apply a stable and adjustable drawing resistance to the sheet (2) in the early stage of drawing.

4. The drawing forming method with a composite shape drawing threshold as described in claim 3, characterized in that, By adjusting the geometric parameters of the reverse forming rib, the shrinkage line (6) of the drawn sheet is controlled within the transition fillet area of ​​the reverse forming rib, thereby reducing the size of the scrap area while maintaining forming stability.

5. The drawing forming method with a composite shape drawing threshold as described in claim 1, characterized in that, During the drawing process, the upper die (1) simultaneously completes the forming of the drawing threshold body and the reverse forming rib during the closing stage of the blank holder (5), so that the drawing resistance remains continuous and stable throughout the entire drawing stroke.

6. The drawing forming method with a composite shape drawing threshold as described in claim 1, characterized in that, The tensile strength of the metal sheet is within a predetermined strength range, which is determined by matching material parameters with forming resistance.

7. The drawing forming method with a composite shape drawing threshold as described in claim 6, characterized in that, The tensile strength of the metal sheet is between 290 MPa and 450 MPa.

8. A drawing forming method with a composite shape drawing threshold as described in any one of claims 1-7, characterized in that, The width of the drawing threshold management surface W1 is ≥10mm; The drawing threshold height is h1, h1 ≥ 5mm; The r-angle of the drawing threshold resistance is r1 ≥ 1.5t, where t is the sheet thickness; The angle r of the reverse forming rib is r2≧2mm for round ribs; The height of the reverse forming rib, h2 ≥ 3mm; Width of the reverse forming rib, W2 ≥ 4mm; The parting line gap C is ≥3mm; if W1 cannot meet the minimum design value, then C will be moved as a whole towards the downward punch direction.

9. A drawing die with a composite-shaped drawing threshold, employing the drawing method with a composite-shaped drawing threshold as described in any one of claims 1-7, characterized in that, It includes an upper die, a lower die, and a blank holder; the blank holder is set on the lower die; the blank holder is provided with a composite-shaped drawing sill, and the blank holder is used to place the metal sheet; the press drives the upper die to move downward and closes with the blank holder, forming the composite drawing sill of the metal sheet, and then the upper die continues to move downward to complete the drawing process.

10. A vehicle body structural component with a composite-shaped drawn threshold, characterized in that, The vehicle body structural components are manufactured using the drawing forming method with a composite shape drawing threshold as described in any one of claims 1-7.

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