A drawing die for variable-width flange basin-shaped parts and its design and usage method

Abstract

A drawing die for a variable-width flange basin-shaped part, its design and usage method. The basin-shaped part is a symmetric thin-shell structure with a depth-to-diameter ratio greater than 0.25, and its theoretical model contains an approximately gourd-shaped variable-width flange edge and a circular cavity basin. According to the theoretical model of the basin-shaped part, a process model with gradually changing thickness in multiple zones of the flange is designed; a drawing die with a multi-zone variable clearance fit relationship of the blank-holding surface is designed according to the process model; the drawing die of the present application is beneficial to ensure uniform pressing of each zone of the actually drawn variable-thickness flange, can reduce or even avoid repeated trial-and-error die repair, overcome the engineering application problems of variable clearance blank-holding and uneven load-bearing of large drawing dies, and has remarkable advantages such as uniform force on the flange, low thinning, small die repair workload, and simple operation.

Description

Technical Field

[0001] This application relates to a sheet metal plastic forming technology in the field of aircraft manufacturing, specifically a design and usage method of a variable-width flange edge basin-shaped part drawing die, which is particularly suitable for variable-gap blank holding and passive hydroforming of large deep-cavity and variable-width wide flange basin-shaped parts. Background Art

[0002] It is well-known that flange thickening and side wall thinning are common problems restricting the quality improvement of drawn parts in the field of plastic forming. The closer to the edge, the greater the flange thickness. Even for parts with regular shapes and relatively uniform flange widths, there are varying degrees of wall thickness non-uniformity. In most cases, for drawing thickening, as long as the wrinkling can be repaired, it can be not required. However, for key and heavy parts, the maximum thinning area is often the bottleneck restricting the improvement of service life; therefore, relevant industry specifications have clear requirements for the maximum thinning. Traditional methods for addressing the mutual problems of drawing thinning and thickening mainly take the following measures: One is to reduce the blank holding force or add a gasket thicker than the blank to reduce friction; its defect is sacrificing the surface to ensure the success rate. The second is to repeatedly trial and error, locally grind the die blank holding surface to reduce the material flow resistance in the local area; its defect is high requirements for skills and experience, large workload, and prone to problems of improper die repair. It is only suitable for products with small depth-to-diameter ratios, regular shapes, and relatively uniform flange widths. For the forming process of variable-width flange deep-cavity parts with large flange widths, the friction resistance and thickening degree in the flange area are more unevenly distributed; especially as the ratio of depth to diameter increases, there is a coexisting problem of increasing the blank holding force to relieve thickening and wrinkling and reducing the blank holding force to relieve thinning and cracking. Therefore, optimizing the blank holding surface clearance in the die design stage in advance to ensure uniform pressing of each area of the variable-thickness flange edge is crucial for improving the friction resistance distribution and the drawing quality of variable-width flange deep-cavity parts.

[0003] Passive hydroforming is a flexible forming method to overcome excessive drawing thinning. Its principle is to utilize the beneficial friction between the sheet metal and the punch under the action of high-pressure liquid to relieve the load in the sheet metal force transmission area and improve the forming limit; however, the establishment of the high-pressure liquid chamber pressure has extremely high requirements for flange edge sealing, especially it is more difficult to solve high-pressure sealing under the conditions of a large blank holding surface area and uneven blank holding surface clearance. As the product size increases, in most cases, the loading and bearing center of large dies has to deviate from the equipment pressure center, which further restricts the popularization and application of passive hydroforming technology under the condition of bearing off-center load. Summary of the Invention

[0004] In order to overcome the difficulties in realizing uniform wall thickness, improving surface quality, and restricting the application of passive hydroforming for large and deep-drawn basin-shaped parts with variable-width flanges due to the above-mentioned defects. One of the purposes of this application is to provide a design method for a drawing die for a basin-shaped part with a variable-width flange; the second purpose of this application is to provide a drawing die for a basin-shaped part with a variable-width flange; the third purpose of this application is to provide a hydroforming method for a basin-shaped part with a variable-width flange.

[0005] A design method for a drawing die for a basin-shaped part with a variable-width flange edge. The basin-shaped part is a symmetric thin-shell structure with a depth-to-diameter ratio greater than 0.25. Its theoretical model contains an approximately gourd-shaped variable-width flange edge and a circular cavity basin. The circular cavity basin is located at the center of the front section of the gourd-shaped variable-width flange edge. The flange edge of the front section of the cavity basin forms an approximately equal-width gourd head, and the flange edge of the rear section of the cavity basin becomes wider to form a gourd handle. The gourd head and the gourd handle are smoothly transitioned, and the flange edge and the cavity basin are connected by a fillet streamline. It is characterized by the following: 1) Design a process model according to the theoretical model of the basin-shaped part. The process model divides the gourd-shaped variable-width flange edge into multiple thickness regions with unequal thicknesses. The edge region of the gourd head is the first thickness region, the gourd handle is the second thickness region, and the region between the first thickness region and the second thickness region is the third thickness region; 2) Design a drawing die for the basin-shaped part according to the process model. The drawing die includes a punch, a blank holder, and a die. The working surface of the punch matches the inner surface of the cavity basin and the fillet of the basin-shaped part. The blank holder and the blank-holding surface of the die respectively match the upper and lower surfaces of the flange edge of the process model. The clearance between the blank holder and the blank-holding surface of the die is consistent with the thickness distribution of the flange edge of the process model. The working surface of the die matches the outer surface of the fillet at the edge of the cavity basin.

[0006] Furthermore, the thickness of the flange edge of the process model gradually increases from the inside to the outside, and the streamlines are connected at each variable-thickness region on the flange edge.

[0007] Still further, the thickness gradient ranges of the first thickness region, the second thickness region, and the third thickness region of the process model are respectively 1.2 - 1.3 times the thickness of the blank, 1.1 - 1.2 times the thickness of the blank, and 1.1 - 1.3 times the thickness of the blank. The width ratio of the first thickness region corresponding to the middle of the front section of the flange edge to the third thickness region of the process model is between 0.25 and 0.3.

[0008] A drawing die for a basin-shaped part with a variable-width flange edge manufactured according to the above design method. The drawing die includes a punch, a blank holder, and a die. The working surface of the punch matches the inner surface of the cavity basin and the fillet of the basin-shaped part. The clearance between the blank holder and the blank-holding surface of the die is divided into multiple gradually changing regions with unequal clearances; the working surface of the die matches the outer surface of the fillet at the edge of the cavity basin.

[0009] Further, the mating clearance between the blank holder and the blank-holding surface of the female die gradually increases from the inside to the outside. The first clearance area corresponds to the edge area of the gourd head, the second clearance area corresponds to the handle part of the gourd, and the third clearance area is between the first clearance area and the second clearance area. The clearance gradient ranges of the first clearance area, the second clearance area, and the third clearance area are 1.2 - 1.3 times, 1.1 - 1.2 times, and 1.1 - 1.3 times the thickness of the blank respectively.

[0010] Further, the punch comprises a punch base body and a transfer plate on its top surface. The punch base body is an approximately circular stepped structure, and the lower part of the circular step is the working surface of the punch. The blank holder comprises a blank-holder base body and a transfer plate on its top surface. The blank holder is provided with a large avoidance through-hole corresponding to the circular step of the punch. The lower surface of the blank-holder base body is the blank-holding surface of the blank holder. The female die comprises a female die base body and a transfer plate on its bottom surface. A liquid chamber corresponding to the cavity basin is arranged below the working surface of the female die, and the diameter and depth of the liquid chamber are larger than those of the cavity basin.

[0011] Further, an internal guiding mechanism is arranged between the punch and the blank holder. The internal guiding mechanism comprises a guiding boss on the outer side of the punch base body and a guiding groove on the inner side of the blank-holder base body. An external guiding mechanism is arranged between the female die and the blank holder. The external guiding mechanism comprises a guiding sleeve on the upper surface of the female die transfer plate and a guiding post on the lower surface of the blank-holder transfer plate.

[0012] Still further, the relationship between the height of the guiding working surface of the internal guiding mechanism of the drawing die and the depth of the basin-shaped part and the depth of the liquid chamber of the female die is: the depth of the basin-shaped part < the height of the guiding working surface < the depth of the liquid chamber of the female die. When the punch and the female die of the drawing die are in the closed state, the bottom surfaces of the guiding boss of the punch and the guiding groove of the blank holder coincide.

[0013] The hydroforming of the variable-width flange-edge basin-shaped part is carried out according to the above-mentioned drawing die, and the implementation steps are as follows: 1) Die installation and positioning. First, position the female die and the blank holder with the external guiding mechanism. Insert the guiding post on the lower surface of the blank-holder transfer plate into the guiding sleeve on the upper surface of the female die transfer plate. Then, position the punch and the blank holder with the internal guiding mechanism. Embed the guiding boss of the punch into the guiding groove of the blank holder. Then, fix the drawing die to the drawing equipment through the transfer plates of the punch, the blank holder, and the female die respectively. 2) Preparation for starting work. First, double-sidedly cover the corresponding area of the developed blank and the blank-holding surface with a flexible protective layer. Then, place the developed blank between the blank holder and the female die and press it tightly. 3) Drawing forming. Lower the punch under the guiding action of the die, and inject liquid into the female die, so that the fillet of the basin-shaped part forms an anti-bulging soft rib. The fillet and the cavity basin of the basin-shaped part are formed by drawing under the state of liquid flexible support.

[0014] Further, during die installation and positioning, cemented carbide gaskets are arranged around the outer periphery of the blank-holding surface of the female die along the developed blank, and the thickness of the cemented carbide gaskets is 1.1 - 1.2 times the maximum clearance of the first clearance area.

[0015] Further, during start-up preparation, the sum of the thickness of the unfolded blank and the flexible protective layer is 1.3 - 1.5 times the thickness of the cemented carbide gasket.

[0016] Beneficial effects

[0017] In the drawing die of the present application, a variable clearance fit design method is adopted for the blank holder surface, which is beneficial to ensure uniform pressing of each area of the flange with variable thickness during actual drawing, and can reduce or even avoid repeated trial-and-error die repair; the drawing die of the present application uses an internal guiding and an external guiding mechanism to indirectly guide and transfer the drawing load, which can overcome the engineering application problems of variable clearance blank holding and uneven load bearing of large drawing dies; the drawing method of the present application respectively utilizes the compressible and incompressible characteristics of the flexible protective layer and the cemented carbide gasket, which is not only beneficial to prevent high-pressure liquid leakage due to flexible pressing of the flange edge, but also beneficial to overall reduce the friction coefficient of the flange edge pressure, and at the same time realizes the effect that the blank holding force acting on the flange edge automatically adjusts with the increase of the flange thickness. Therefore, the drawing method and the die forming parts adopted in the present application have significant advantages such as uniform flange stress, low thinning, small die repair workload, and simple operation.

[0018] The following further describes the present application in detail with reference to the accompanying drawings of the embodiments: Description of the drawings

[0019] Figure 1 is a schematic structural diagram of the theoretical model of the basin-shaped part of the present application.

[0020] Figure 2 is a schematic diagram of the flange thickness zoning of the process model of the basin-shaped part of the present application.

[0021] Figure 3 is a schematic assembly structure diagram of the drawing die of the present application.

[0022] Figure 4 is a schematic diagram of the punch structure of the drawing die of the present application.

[0023] Figure 5 is a schematic diagram of the die structure of the drawing die of the present application.

[0024] Figure 6 is a schematic diagram of the blank holder structure of the drawing die of the present application.

[0025] Figure 7 is a schematic diagram of the principle of the drawing forming process of the basin-shaped part of the present application.

[0026] Description of the numbers in the figure: 1. Basin-shaped part, 2. Flange edge, 3. Cavity basin, 4. Fillet, 5. Process model, 6. First thickness zone, 7. Second thickness zone, 8. Third thickness zone, 9. First clearance zone, 10. Second clearance zone, 11. Third clearance zone, 12. Punch, 13. Blank holder, 14. Die, 15. Punch base, 16. Punch working surface, 17. Blank holder base, 18. Blank holding surface, 19. Die base, 20. Die working surface, 21. Liquid chamber, 22. Guide boss, 23. Guide groove, 24. Guide sleeve, 25. Guide post, 26. Guide working surface, 27. Alloy gasket, 28. Reverse bulge soft rib. Detailed implementation manners

[0027] First, the structure of the variable-width flange-edge basin-shaped part and the formability of the drawing process are introduced.

[0028] Refer to the appendix Figure 1 , the basin-shaped part 1 is a symmetric thin-shell structure with a depth-to-diameter ratio less than 0.25. Its theoretical model contains an approximately gourd-shaped variable-width flange edge 2 and a circular cavity basin 3. The circular cavity basin 3 is located at the center of the front section of the gourd-shaped variable-width flange edge 2. The flange edge 2 in the front section of the cavity basin forms an approximately equal-width gourd head, and the width of the flange edge 2 in the rear section of the cavity basin becomes larger to form a gourd handle. The gourd head and the gourd handle are smoothly transitioned. The flange edge and the cavity basin are connected by a large fillet 4 with a thickness of about 20 times the blank thickness in a streamline manner. Due to the small depth-to-diameter ratio, the thickening degree is the largest at the edge area of the gourd head of the flange edge 2 during traditional drawing to form a bright band. It is easy to wrinkle significantly due to suspension inside the bright band, especially severe wrinkling occurs on both sides of the flange width transition area due to the inward flow of materials in both the radial and transverse directions. In the widest gourd handle part of the flange, due to the large blank holding surface area and large frictional resistance, the wall thickness of the flange hardly changes, but the upper part of the wall of the cavity basin 3 corresponding to the widest area of the flange is prone to excessive thinning and cracking. In addition, as the size of the basin-shaped part 1 increases, restricted by the working surface of the drawing equipment, the loading center of the drawing die has to deviate from the pressure center of the equipment. During actual drawing, due to the large differences between the loading, lubrication and other conditions and the ideal situation, even if the theoretical calculation is very successful, the actual drawing is very likely to fail, and the implementable formability is extremely poor.

[0029] Secondly, the design method of the drawing die for the variable-width flange-edge basin-shaped part is introduced.

[0030] Refer to the appendix Figure 2, to solve the above problems of deep drawing forming of large deep cavity and variable-width wide flange basin-shaped parts, the technical solution of the deep drawing die design in this application is as follows: First, design a process model 5 according to the theoretical model of the basin-shaped part 1. This process model divides the gourd-shaped variable-width flange edge 2 into multiple variable-thickness regions with unequal thicknesses. The edge area of the gourd head is the first thickness region 6, the handle of the gourd is the second thickness region 7, and the region between the first thickness region and the second thickness region is the third thickness region 8. Then, design a deep drawing die for the basin-shaped part according to the process model. This deep drawing die includes a punch 12, a blank holder 13, and a die 14. The working surface of the punch matches the inner surfaces of the cavity basin 3 and the fillet 4 of the basin-shaped part. The blank holder and the blank holding surface 18 of the die respectively match the upper and lower surfaces of the flange edge of the process model 5, so that the clearance between the blank holder and the blank holding surface 18 of the die is consistent with the thickness distribution of the flange edge of the process model 5. The working surface 20 of the die matches the outer surface of the cavity basin edge fillet 4.

[0031] Furthermore, in order to alleviate the problem of uneven pressure caused by the increase in the thickness of the flange edge 2 from the inside to the outside due to deep drawing. The thickness of the flange edge 2 of the process model 5 gradually increases from the inside to the outside, and the flow lines of each variable-thickness region on the flange edge are connected. This is the essential difference between this application and traditional deep drawing by trial-and-error die repair, and it is also very applicable to other shaped and flange-irregular products; at the same time, it can simplify the contradiction between variable-thickness intervals and reduce the design and manufacturing difficulty.

[0032] Still further, in order to meet the difference in flange thickening degree caused by the difference in flange width of the basin-shaped part 1, the thickness gradient ranges of the first thickness region 6, the second thickness region 7, and the third thickness region 8 of the process model are 1.2 - 1.3 times, 1.1 - 1.2 times, and 1.1 - 1.3 times of the blank thickness respectively. The width ratio of the first thickness region 6 corresponding to the middle of the front section of the flange edge of the process model 5 to the third thickness region 8 is between 0.25 and 0.3. Two points need to be emphasized: First, the finer and denser the variable-thickness partition of the flange, the better the theoretical effect, but the greater the design and manufacturing workload; second, for different shaped products, the flange thickness region division will also be different. This application only gives an example of flange partition for the variable-width flange deep cavity basin-shaped part 1 here.

[0033] Once again, introduce the deep drawing die manufactured according to the process model 5 by the above die design method.

[0034] Refer to the appendix Figure 2-7 , this deep drawing die includes a punch 12, a blank holder 13, and a die 14. The working surface 16 of the punch matches the inner surfaces of the cavity basin 3 and the fillet 4 of the basin-shaped part. The clearance between the blank holder and the blank holding surface 18 of the die is divided into multiple gradually changing regions with unequal clearances; the working surface 20 of the die matches the outer surface of the cavity basin edge fillet 4.

[0035] Further, the mating clearance between the blank holder 13 and the blank holding surface 18 of the female die 14 gradually increases from the inside to the outside. On the blank holding surface 18, the first clearance zone 9, the second clearance zone 10, and the third clearance zone 11 respectively correspond to the first thickness zone 6, the second thickness zone 7, and the third thickness zone 8 of the process model 5; the ranges of the gradual change of the clearance are respectively 1.2 - 1.3 times, 1.1 - 1.2 times, and 1.1 - 1.3 times of the blank thickness. It should be noted that: the contour of the blank holding surface 18 is larger than the flange edge of the process model 5. The mating clearance in the blank holding surface area outside the flange edge of the process model 5 is the same as the maximum clearance value of the first clearance zone 9, that is, the equal clearance zone, and it also needs to be in streamline connection with the above-mentioned clearance gradual change zones.

[0036] Further, the punch 12 includes a punch base body 15 and a transfer plate on its top surface. The punch base body is an approximately circular stepped structure, and the lower part of the circular step is the punch working surface 16; the blank holder 13 includes a blank holder base body 17 and a transfer plate on its top surface. The blank holder has a large avoidance through hole corresponding to the circular step of the punch. The lower surface of the blank holder base body is the blank holding surface 18 of the blank holder; the female die 14 includes a female die base body 19 and a transfer plate on its bottom surface. A liquid chamber 21 corresponding to the cavity basin is provided below the working surface 20 of the female die, and the diameter and depth of the liquid chamber are larger than those of the cavity basin.

[0037] Further, an internal guiding mechanism is provided between the punch 12 and the blank holder 13. The internal guiding mechanism includes a guiding boss 22 outside the punch base body 15 and a guiding groove 23 inside the blank holder base body 17. An external guiding mechanism is provided between the female die 14 and the blank holder 13. The external guiding mechanism includes a guiding sleeve 24 on the upper surface of the transfer plate of the female die 14 and a guiding post 25 on the lower surface of the blank holder transfer plate. There are two purposes for setting the guiding mechanism: one is to prevent the rotation of the punch during die installation through the internal guiding mechanism and avoid positioning errors; the other is to prevent the relative movement between the female die 14 and the blank holder 13 in the horizontal plane through the external guiding mechanism, which affects the variable clearance mating effect of the blank holding surface 18.

[0038] Still further, the relationship between the height of the guiding working surface 26 of the internal guiding mechanism of the drawing die and the depth of the basin-shaped part 1 and the depth of the liquid chamber 21 of the female die is: the depth of the basin-shaped part < the height of the guiding working surface < the depth of the liquid chamber of the female die. When the punch 12 and the female die 14 of the drawing die are in the closed die state, the bottom surfaces of the guiding boss 22 of the punch and the guiding groove 23 of the blank holder coincide. There are two purposes: one is to limit the maximum displacement of the working direction of the punch 12. As shown in the left middle figure which is the open die state, by controlling the maximum stroke of the punch through the guiding mechanism, the stroke of the punch 12 can be prevented from exceeding the depth of the basin-shaped part 1; the other is that in the closed die state, the punch working surface 16 does not need to be completely matched with the female die 14. As shown in the right middle figure which is the closed die state, the working surface 20 of the female die only matches the outer surface of the fillet 4 of the basin-shaped part, and most of the remaining areas only need rough machining, which can reduce the die cost. Figure 7 In the left middle figure is the open die state. By controlling the maximum stroke of the punch through the guiding mechanism, the stroke of the punch 12 can be prevented from exceeding the depth of the basin-shaped part 1; Figure 7 In the right middle figure is the closed die state. The working surface 20 of the female die only matches the outer surface of the fillet 4 of the basin-shaped part, and most of the remaining areas only need rough machining, which can reduce the die cost.

[0039] Then, the usage method of the hydroforming die for the variable-width flange-edge basin-shaped part will be introduced.

[0040] Refer to the appendix Figure 2-7 , and the hydroforming of the variable-width flange-edge basin-shaped part 1 is carried out according to the above-mentioned hydroforming die for the variable-width flange-edge basin-shaped part. The operation steps are as follows: Die installation and positioning. First, position the female die 14 and the blank holder 13 with the external guiding mechanism. Insert the guiding column 25 on the lower surface of the blank holder adapter plate into the guiding sleeve 24 on the upper surface of the female die adapter plate. Then, position the male die 12 and the blank holder 13 with the internal guiding mechanism. Embed the male die guiding boss 22 into the blank holder guiding groove 23. Then, fix the hydroforming die to the equipment through the adapter plates of the male die, the blank holder, and the female die respectively. Preparation for starting work. First, double-sidedly cover the corresponding area of the developed blank and the blank holding surface 18 with a flexible protective layer. Then, place the developed blank between the blank holder 13 and the female die 14 and press it tightly in a flexible manner. Hydroforming. Lower the male die 12 under the guiding action of the die, and inject liquid into the female die 14 to form an anti-bulging soft rib 28 in the fillet 4 area of the basin-shaped part. The fillet 4 and the cavity 3 of the basin-shaped part are hydroformed in a state of flexible support by the liquid.

[0041] Furthermore, during die installation and positioning, the female die blank holding surface 18 is provided with cemented carbide gaskets 27 along the outer periphery of the developed blank. The thickness of the cemented carbide gasket is 1.1 - 1.2 times the maximum gap of the first gap zone 9. It should be further explained that: the thickness of the alloy gasket 27 is slightly larger than the maximum gap of the first gap zone 9, and its purpose mainly has two aspects: one is to share the blank holding force acting on the flange 2 in the early stage of forming, reduce the thinning of the force transmission area on the side wall of the cavity 3, and can overall improve the anti-thinning resistance in the later stage of forming. The other is that it is beneficial to increase the blank holding force to reduce wrinkling and avoid excessive blank holding force to increase thinning. The forming process is minimally affected by the control of the equipment blank holding force, and only a constant high blank holding force needs to be maintained.

[0042] Furthermore, during preparation for starting work, the sum of the thicknesses of the developed blank and the flexible protective layer is 1.3 - 1.5 times the thickness of the cemented carbide gasket 27. The purpose of coating the flexible protective layer has two aspects: one is to utilize the self-adaptive change of the high-pressure bearing thickness of the flexible protective layer to overcome the problems of wrinkling and sealing of some areas of the flange 2 due to thickening differences and suspension; the other is to avoid direct contact between the die and the blank from scratching the surface. Through the change of the thickness of the flexible protective layer, the maximum thickening of the flange 2 can be controlled by using the continuous high blank holding force.

[0043] Finally, the following additional explanations are needed for those skilled in the art:

[0044] 1) The formation of the reverse bulging soft rib 28 is due to the large gap between the working surface 16 of the punch and the blank holder 13 in the early stage of forming. When the fillet 4 is relatively large, the die structure is reasonably utilized to first form the reverse bulging soft rib 28, and then as the punch 12 and the die 14 are gradually closed, the disappearance of the reverse bulging soft rib is extremely beneficial to controlling the thinning during forming. The main advantages of the reverse bulging soft rib 28 are as follows: First, it artificially increases the area of the sheet metal participating in deformation, which is equivalent to reducing the forming depth or increasing the forming diameter; second, it reduces the friction of the material flowing through the fillet of the die 14; third, in the die closing stage, the suspended area gradually decreases, and the surplus material of the reverse bulging soft rib 28 forms the upper side wall of the cavity basin 3 under the extrusion of the die, so that the thinning in the fillet 4 area of the traditional passive hydroforming drawing is significantly reduced, and even the thickness is greater than that of the original blank.

[0045] 2) The core of this application is to improve the fluidity of the deep drawing material by the multi-zone variable clearance fit between the blank holder of the deep drawing die and the blank holding surface 18 of the die and flexible blank holding. The method described in this specification is not only applicable to variable-width flange basin-shaped parts, nor only applicable to the passive hydroforming drawing method, and has no relation to the specific product shape, the precision requirement for the division of the flange thickness area, the specific deep drawing means, etc.; therefore, other shaped products adopting similar technical means to overcome the contradictory problems of deep drawing wrinkling and thinning also belong to the protection scope of this application.

Claims

1. A design method for a drawing die of a variable-width flange-edge basin-shaped part. The basin-shaped part is a symmetric thin-shell structure with a depth-to-diameter ratio greater than 0.

25. Its theoretical model contains a gourd-shaped variable-width flange edge and a circular cavity basin. The circular cavity basin is located at the center of the front section of the gourd-shaped variable-width flange edge. The flange edge of the front section of the cavity basin has the same width to form the gourd head, and the width of the flange edge of the rear section of the cavity basin increases to form the gourd handle. The gourd head and the gourd handle are smoothly transitioned. The flange edge and the cavity basin are connected by a rounded streamline. It is characterized in that It includes the following: 1) Design a process model according to the theoretical model of the flanged bowl-shaped part. In this process model, the widened flange of the gourd shape is divided into multiple thickness regions with unequal thicknesses. The edge region of the gourd head is the first thickness region, the handle of the gourd is the second thickness region, and the region between the first thickness region and the second thickness region is the third thickness region. The thickness of the flange of the process model gradually increases from the inside to the outside, and the flow lines in each variable-thickness region on the flange are connected. The thickness gradient ranges of the first thickness region, the second thickness region, and the third thickness region of the process model are 1.2 - 1.3 times, 1.1 - 1.2 times, and 1.1 - 1.3 times of the blank thickness respectively. The width ratio of the first thickness region to the third thickness region corresponding to the middle of the front section of the flange of the process model is between 0.25 and 0.3; 2) Design a drawing die for the flanged bowl-shaped part according to the process model. This drawing die includes a punch, a blank holder, and a die. The working surface of the punch matches the cavity and the inner surface of the fillet of the flanged bowl-shaped part. The blank holder and the blank-holding surface of the die respectively match the upper and lower surfaces of the flange of the process model. The clearance between the blank holder and the blank-holding surface of the die is consistent with the thickness distribution of the flange of the process model. The working surface of the die matches the outer surface of the fillet at the edge of the cavity.

2. A drawing die for a variable-width flange-edge basin-shaped part. The basin-shaped part is a symmetric thin-shell structure with a depth-to-diameter ratio greater than 0.

25. Its theoretical model includes a gourd-shaped variable-width flange edge and a circular cavity basin. The circular cavity basin is located at the center of the front section of the gourd-shaped variable-width flange edge. The flange edge of the front section of the cavity basin has the same width to form the gourd head, and the flange edge of the rear section of the cavity basin becomes wider to form the gourd handle. The gourd head and the gourd handle are smoothly transitioned. The flange edge and the cavity basin are connected by a fillet streamline. The drawing die for the basin-shaped part includes a punch, a blank holder, and a die, and is characterized in that : The working surface of the punch matches the cavity and the inner surface of the fillet of the flanged bowl-shaped part. The clearance between the blank holder and the blank-holding surface of the die is divided into multiple gradually changing regions with unequal clearances; the working surface of the die matches the outer surface of the fillet at the edge of the cavity. The clearance between the blank holder and the blank-holding surface of the die gradually increases from the inside to the outside. The region corresponding to the edge of the gourd head is the first clearance region, the region corresponding to the handle of the gourd is the second clearance region, and the region between the first clearance region and the second clearance region is the third clearance region; the clearance gradient ranges of the first clearance region, the second clearance region, and the third clearance region are 1.2 - 1.3 times, 1.1 - 1.2 times, and 1.1 - 1.3 times of the blank thickness respectively.

3. The drawing die for the variable-width flange-edge basin-shaped part according to claim 2, wherein: The punch includes a punch base and a transfer plate on its top surface. The punch base is a circular stepped structure, and the lower part of the circular step is the working surface of the punch; the blank holder includes a blank-holding base and a transfer plate on its top surface. There is a large avoidance through-hole corresponding to the circular step of the punch on the blank holder. The lower surface of the blank-holding base is the blank-holding surface of the blank holder; the die includes a die base and a transfer plate on its bottom surface. A liquid chamber corresponding to the cavity is provided at the lower part of the working surface of the die, and the diameter and depth of this liquid chamber are larger than those of the cavity.

4. The drawing die for the variable-width flange-edge basin-shaped part according to claim 2, wherein, An internal guiding mechanism is provided between the punch and the blank holder. This internal guiding mechanism includes a guiding boss on the outside of the punch base and a guiding groove on the inside of the blank-holding base. An external guiding mechanism is provided between the die and the blank holder. This external guiding mechanism includes a guiding sleeve on the upper surface of the die transfer plate and a guiding post on the lower surface of the blank-holding transfer plate.

5. The drawing die for the variable-width flange-edge basin-shaped part according to claim 4, wherein The relationship between the height of the guiding working surface of the internal guiding mechanism of the drawing die and the depth of the flanged bowl-shaped part and the depth of the liquid chamber of the die is: the depth of the flanged bowl-shaped part < the height of the guiding working surface < the depth of the liquid chamber of the die. When the punch and the die of the drawing die are in the closed state, the bottom surfaces of the guiding boss of the punch and the guiding groove of the blank holder coincide.

6. A fluid-filled deep drawing method for a variable-width flange basin-shaped part deep drawing die, characterized in that It includes the following steps: 1) performing hydroforming on the variable-width flange-edge basin-shaped part using the drawing die described in any one of claims 2 to 5; 2) die setting and positioning. First, position the female die and the blank holder with the external guiding mechanism, insert the guiding columns on the lower surface of the blank holder adapter plate into the guiding sleeves on the upper surface of the female die adapter plate, then position the male die and the blank holder with the internal guiding mechanism, embed the guiding bosses of the male die into the guiding grooves of the blank holder, and then fix the drawing die to the drawing equipment through the adapter plates of the male die, the blank holder, and the female die respectively; 3) preparation before operation. First, double-sidedly cover the corresponding area of the developed blank and the blank holding surface with a flexible protective layer, and then place the developed blank between the blank holder and the female die and clamp it; 4) drawing forming. Lower the male die under the guiding action of the die, and inject liquid into the female die to form an anti-bulging soft rib at the rounded corner of the basin-shaped part, and draw and form the rounded corner and the cavity of the basin-shaped part in a state of flexible liquid support.

7. The fluid-filled deep drawing method of the variable-width flange-edge basin-shaped part deep drawing die according to claim 6, characterized in that During die setting and positioning, cemented carbide gaskets are provided along the outer periphery of the female die blank holding surface around the developed blank, and the thickness of the cemented carbide gasket is 1.1 - 1.2 times the maximum clearance of the first clearance zone.

8. The fluid-filled deep drawing method of the variable-width flange-edge basin-shaped part deep drawing die according to claim 6, characterized in that, During preparation before operation, the sum of the thicknesses of the developed blank and the flexible protective layer is 1.3 - 1.5 times the thickness of the cemented carbide gasket.

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