An adjustable pressure flexible blank holder loading draw die and method of use

Abstract

The present application belongs to the technical field of aircraft manufacturing, and discloses a flexible pressure-adjustable blank holder loading drawing die and a use method thereof. The drawing die comprises a female die, a blank holder and a male die. The female die surface is partially matched with the outer surface of a part. The upper surface of the blank holder is provided with a sunken surface matched with the shape of an expanded blank. The working surface of the male die is matched with the lower surface of the inner side area of the root fillet of the part. The female die and the blank holder tightly press the adjustable pressure fluid medium on the upper surface of the expanded blank, and the part is drawn and formed on the male die. The technical problem of concentrated pressure loading and mutual contradiction of traditional drawing and loading is overcome. The fluid medium flexible blank holder mode is adopted, the female die and the flange edge of the part are not in contact and friction, and the die bearing deformation does not affect the uniformity of the blank holder load. The present application has the advantages of good lubrication effect, low die processing cost, strong technical universality and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of plastic working in aircraft manufacturing, and particularly relates to an adjustable pressure flexible blank holder loading drawing die and a use method thereof, and is especially suitable for fluid loading blank holder drawing forming of deep cavity high-difficulty parts with large flange thickening distribution and width difference. BACKGROUND

[0002] It is known that local concentration of blank holder load is a common problem that has long plagued the yield of complex drawing parts. The larger the traditional rigid drawing blank holder load is, the better the surface quality of the part is, but the lower the yield is. The reason is that with the increase of the blank holder load, the deformation of the blank holder ring increases, and the local area flow resistance increases sharply due to the concentration of the blank holder load. Generally, the forming depth of a circular part is significantly higher than that of a part with irregular shape. The reason is that the more regular the shape is, the more uniform the flange thickening distribution is in the forming process, and the more likely it is to delay the rupture caused by local concentration of blank holder load. On the contrary, the more complex the shape is, the more likely it is to produce a large thickness difference in the flange edge, and the more likely it is to form a local concentration of blank holder load in the thickest part of the flange edge. The corresponding drawing force transmission area is quickly broken due to overloading. Especially for box-shaped deep cavity parts with large flange width in the corner area, the thickness and width of the flange edge are significantly larger than those of the remaining blank holder area during drawing, and the corner corresponding to the die round corner is prone to rupture. In addition, due to the limitations of factors such as thickness deviation distribution of the blank, manufacturing matching precision of the die pressure surface, and difference in die bearing deformation, it is difficult to ensure uniform pressure in each area of the pressure surface. Even if the same batch of raw materials and the same set of dies are used, there are differences in drawing effect, which greatly increases the difficulty of stable batch production of similar parts.

[0003] In actual drawing, in order to improve the surface quality of the drawing part, it is necessary to increase the blank holder load as much as possible, and in order to improve the yield, it is necessary to improve the lubrication effect. However, increasing the load and reducing friction, and uniform distribution of load are always in extreme conflict. In order to solve the risk of local friction increasing sharply caused by the increase of the blank holder load, the applicant's prior patent publication No. CN 116727524 A is essentially to make the load of the multiple variable gap pressure surfaces more uniform by the difference in compression degree of the double-sided plastic film. Compared with the conventional rigid blank holder method, this technology can increase the forming depth by nearly one time under the same blank holder load. However, with the further increase of the blank holder load, the risk of blank holder load concentration will be greater. This disclosed technology can only alleviate the effect of blank holder load concentration within a small range of increase of the blank holder load, and cannot freely adjust the effective blank holder load of the blank as needed. SUMMARY

[0004] This invention aims to overcome the common problem of traditional rigid blank holder drawing dies being affected by factors such as die deformation, blank thickness deviation, and uneven deformation due to irregular shape; leading to localized concentration of blank holder loads and localized overload in the corresponding force transmission area, thus hindering the improvement of forming depth and quality of complex parts. It proposes an adjustable-pressure flexible blank holder loading drawing die and its usage method. By applying a uniform blank holder load to the flange edge through a fluid medium in a high-pressure, closed environment, the blank holder load can be significantly increased while friction is reduced in a single-sided flexible contact state with the die, achieving the goal of simultaneously improving the forming depth and forming quality of complex parts.

[0005] To achieve the aforementioned objectives, the technical solution adopted in this application is as follows:

[0006] An adjustable pressure flexible blank holder loading deep drawing die, comprising:

[0007] A die, wherein the die surface partially matches the outer surface of the part, and the matching part is the root fillet of the part and its adjacent areas on both sides;

[0008] A pressure ring, wherein the upper surface of the pressure ring is provided with an annular recessed surface whose outer contour matches the shape of the unfolded blank, and the inner contour of the recessed surface matches the root of the outer wall of the part;

[0009] The punch has a working surface that matches the lower surface of the inner corner area of ​​the root of the part, and the lower straight wall section of the punch's working surface matches the inner contour of the recessed surface of the pressure ring.

[0010] The die and pressure ring seal the adjustable pressure fluid medium on the unfolded blank, so that the surface of the unfolded blank corresponding to the annular recessed surface is in a uniform and flexible pressing state, and the unfolded blank is drawn into a part on the punch.

[0011] As a further aspect of the present invention: the lower surface of the die is provided with an inner sealing groove and an inner sealing ring at the rounded corner near the root of the part, and an outer sealing groove and an outer sealing ring are provided on the outer side of the annular recessed surface of the pressure ring. A liquid filling hole and a liquid draining hole are provided between the inner sealing ring and the outer sealing ring. The liquid filling hole is connected to a hydraulic power source through a pressurization pipeline, and the liquid draining hole is connected to a pressure control valve through a pressure relief pipeline.

[0012] As a further aspect of the present invention: the die and the pressure ring are provided with a zero-gap matching surface on the outside of the outer sealing groove and the outer sealing ring, and the zero-gap matching surface matches the extended supplementary surface of the outer surface of the flange edge of the part.

[0013] As a further aspect of the present invention: the matching gap between the die and the pressure ring in the annular recessed area of ​​the pressure ring is greater than the depth of the annular recessed area and greater than or equal to the thickness of the unfolded blank.

[0014] A method for using the adjustable pressure flexible blank holder loading drawing die, using the adjustable pressure flexible blank holder loading drawing die to draw and form parts, which comprises the following steps:

[0015] 1) Unfolded blank positioning preparation: raise the blank holder to make its upper surface lowest point higher than the working surface of the punch, and place the unfolded blank inside the contour of the annular depression surface of the blank holder;

[0016] 2) Unfolded blank compression: first lower the die to pre-compress the unfolded blank upper surface with the stationary blank holder, then fill the fluid medium from the die liquid hole and raise the pressure to the predetermined pressure, so that the unfolded blank in the annular depression surface area of the blank holder is in a flexible compression state;

[0017] 3) Flexible blank holder drawing: simultaneously lower the die and the blank holder, and by controlling the fluid pressure, the unfolded blank in the annular depression surface area is in a uniform loading environment and the blank holder produces single-sided flexible friction to complete the drawing of the part;

[0018] 4) Part unloading: first remove the die load pressure in the blank holder stationary state, so that the drawn part is separated from the die under the pressure of the remaining fluid in the pipeline, and then the die and the blank holder are raised in turn to separate the part from the punch.

[0019] As a further scheme of the present application: further comprising the following steps: before positioning the unfolded blank, covering the unfolded blank lower surface with a super-thin plastic film consistent with its shape; after the unfolded blank is positioned, covering the unfolded blank upper surface with a thickened plastic film.

[0020] As a further scheme of the present application: the super-thin plastic film covering the unfolded blank lower surface has single-sided adhesion, and the adhesion surface is attached to the unfolded blank; the thickened plastic film covering the unfolded blank upper surface is annular, and its inner and outer contours are compressed under the inner and outer sealing rings respectively.

[0021] As a further scheme of the present application: in the step 2), when the unfolded blank is compressed, the static load of the blank holder is not less than 3 times the rigid blank holder drawing blank holder load; in the step 3), when drawing, the dynamic load of the blank holder is not less than 5 times the product of the projection area of the blank holder annular depression surface and the highest fluid pressure.

[0022] As a further scheme of the present application: in the step 3), when drawing, the recommended unit blank holder force of the blank holder annular depression surface corresponding to the unfolded blank upper surface is 10-30Mpa.

[0023] As a further scheme of the present application: in the step 4), when the part drawing is finished and unloaded, the hydraulic source connected with the pressurizing pipeline is closed first; then the concave die is appropriately lifted to make it unload and depressurize, and the lifting height of the concave die during the depressurizing is less than the difference between the thickness of the sealing ring in the natural state and the depth of the sealing groove.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. The drawing die of the present application can realize single-sided flexible friction blank holder drawing forming, compared with the traditional double-sided contact rigid blank holder die; the lubrication effect of the flange edge can be improved by several times, and the higher blank holder load can be used to improve the surface quality of the drawn part.

[0026] 2. The drawing die of the present application only needs to match the edge area of the concave die and the blank holder ring, and the precision of the pressure area is only ensured by the single-sided blank holder ring; compared with the traditional double-sided contact rigid blank holder die, there is no high-precision gap matching manufacturing requirement, and the die cost is low.

[0027] 3. The drawing die of the present application uses high-pressure liquid to load the flange edge of the part, and the gap between the effective pressure area of the concave die and the blank holder ring is greater than the thickness of the blank; compared with the traditional double-sided contact rigid blank holder die, the common problem of easy concentration of blank holder load under high load environment can be completely eliminated.

[0028] 4. The drawing die and forming method adopted by the present application can simultaneously meet the application requirements of high blank holder load and high lubrication effect; and has the advantages of easy implementation and strong universality.

[0029] The present application will be further described below in combination with the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation of the present application.

[0031] In the drawings:

[0032] Figure 1 It is a schematic diagram of a typical part structure suitable for the present application;

[0033] Figure 2 It is a schematic diagram of a typical part drawing die and forming principle suitable for the present application;

[0034] Figure 3 It is a schematic diagram of a concave die structure of a typical part drawing die suitable for the present application;

[0035] Figure 4 It is a schematic diagram of a convex die structure of a typical part drawing die suitable for the present application;

[0036] Figure 5The edge ring structure diagram of the typical part drawing die suitable for the present application is shown in the figure.

[0037] Figure 6 The blank pressing principle diagram of the typical part before drawing suitable for the present application is shown in the figure.

[0038] The figure mark explanation: 1. Part, 2. Flange edge, 3. Root fillet, 4. Concave die, 5. Edge ring, 6. Convex die, 7. Straight wall section, 8. Inner sealing groove, 9. Inner sealing ring, 10. Outer sealing groove, 11. Outer sealing ring, 12. Liquid filling hole, 13. Liquid discharge hole, 14. Pressurizing pipeline, 15. Pressure relief pipeline, 16. Sunken surface, 17. Zero-gap matching profile, 18. Expanded blank. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0040] Firstly, the defects of the traditional drawing process suitable for the typical part of the present application are introduced:

[0041] Referring to the drawings Figure 1 The long box shape with a widened flange edge 2 is one of the representative parts 1 suitable for the present application. Because the structure of the part 1 is irregular, obvious thickness difference is prone to occur in each area of the flange edge 2 during the drawing process, and the load of the concave die on the flange edge 2 is all concentrated in the area with large thickness. The traditional rigid edge drawing die and forming method are difficult to ensure the uniform pressure of each area of the flange edge 2 due to the limitation of many factors such as the distribution of the thickness deviation of the blank, the manufacturing matching precision of the flange edge 2 area of the die, the bearing deformation difference of the die, etc. For the irregular part drawing forming, the common problem of mutual contradiction between the increase of the edge load and the concentration of the bearing deformation load is always faced, which seriously restricts the improvement of the forming depth and quality.

[0042] Secondly, the die technical solution suitable for the typical part of the present application is introduced:

[0043] In order to solve the above-mentioned problems existing in the irregular part drawing forming by the existing rigid edge technology, referring to the drawings Figure 2 to Figure 6 The main technical solution of the drawing die of the present application is as follows:

[0044] An adjustable pressure flexible blank holder loading deep drawing die includes a die 4, a blank holder ring 5, and a punch 6. The die 4's profile partially matches the outer surface of part 1, with the matching area being the root fillet 3 of the part and its adjacent areas on both sides. The upper surface of the blank holder ring 5 has an annular recessed surface 16 whose outline matches the shape of the unfolded blank 18, and the inner outline of the recessed surface 16 matches the root of the outer wall of part 1. The working surface of the punch 6 matches the lower surface of the inner area of ​​the root fillet 3 of the part, and the lower straight wall section 7 of the working surface of the punch 6 matches the inner outline of the recessed surface 16 of the blank holder ring. The die 4 and the blank holder ring 5 seal the adjustable pressure fluid medium onto the unfolded blank 18, so that the surface of the unfolded blank 18 corresponding to the annular recessed surface 16 is in a uniform and flexible compressed state, and the unfolded blank 18 is deep drawn into part 1 on the punch 6.

[0045] The following aspects need to be emphasized in mold design and manufacturing:

[0046] Firstly, to ensure that the flange edge seal is properly adjusted during deep drawing while also considering the effective pressure load, refer to the attached document. Figure 2 Appendix Figure 6 The lower surface of the die 4 is provided with an inner sealing groove 8 and an inner sealing ring 9 at the rounded corner 3 near the root of the part. An outer sealing groove 10 and an outer sealing ring 11 are provided on the outer side of the annular recessed surface 16 of the pressure ring 5. A liquid filling hole 12 and a liquid draining hole 13 are provided between the inner sealing ring 9 and the outer sealing ring 11. The liquid filling hole 12 is connected to a hydraulic source through a pressurization pipeline 14, and the liquid draining hole 13 is connected to a pressure control valve through a pressure relief pipeline 15. By adjusting the pressure control valve, the fluid pressure acting on the flange edge 2 can be adjusted as needed.

[0047] Secondly, to prevent deformation of the pressure ring 5 under high load conditions while also improving the sealing effect, please refer to the attached document. Figure 2 The die 4 and the pressure ring 5 are also provided with a zero-gap matching surface 17 on the outside of the outer sealing groove 10 and the outer sealing ring 11. The zero-gap matching surface 17 matches the extended supplementary surface of the outer surface of the flange edge 2 of the part. The function of the zero-gap matching surface 17 in the edge area of ​​the die is to prevent the pressure ring 5 from deforming due to excessive load.

[0048] Thirdly, in order to achieve uniform edge load while ensuring ultra-high lubrication effect, please refer to the attached document. Figure 2 Appendix Figure 5 The gap between the die 4 and the pressure ring 5 in the annular recessed surface 16 area of ​​the pressure ring is greater than the depth of the annular recessed surface 16 and the thickness of the unfolded blank 18. When the gap between the recessed surface 16 area is greater than the thickness of the sheet, even if the pressure ring 5 is deformed, the unfolded blank 18 will only have one-sided flexible friction contact with the pressure ring 5.

[0049] The biggest difference between the deep drawing die of the present application and the traditional deep drawing die is that the friction between the upper surface of the sheet metal and the concave die 4 is almost negligible, and only the single flexible friction between the blank holder 5 and the sheet metal is generated; and the high-pressure bearing of the blank holder 5 is not easy to deform, and even if the deformation is generated, the load uniformity will not be affected, the lubrication effect can be improved by several times, and even the improvement effect can reach several orders of magnitude.

[0050] Secondly, the use method of forming a typical part using the deep drawing die of the present application is introduced:

[0051] The use method of forming a part using the adjustable pressure flexible blank holder loading deep drawing die is as follows: Figure 1 to Figure 6 The main implementation steps are as follows:

[0052] 1) blank positioning preparation: the upper surface of the blank holder 5 is raised to be higher than the top end of the working surface of the punch 6, and the spread blank 18 is placed in the contour inside the annular depression surface 16 of the blank holder 5.

[0053] 2) blank pressing: first, the concave die 4 is lowered to pre-press the upper surface of the spread blank 18 with the static blank holder 5, then fluid medium is filled from the fluid filling hole 12 of the concave die 4 and the pressure is raised to a predetermined pressure, so that the spread blank 18 in the annular depression surface 16 area of the blank holder 5 is in a flexible pressing state.

[0054] 3) flexible blank holder drawing: the concave die 4 and the blank holder 5 are lowered synchronously, and through the control of the fluid pressure, the spread blank 18 in the annular depression surface 16 area generates single flexible friction with the blank holder 5 in the uniform loading environment to complete the drawing forming of the part 1.

[0055] 4) part unloading: first, the load pressure of the concave die 4 is released in the static state of the blank holder 5, so that the drawn part 1 is separated from the concave die 4 under the pressure of the remaining fluid in the pipeline, and then the concave die 4 and the blank holder 5 are raised in turn, and the part 1 is separated from the punch 6.

[0056] The use technical points of the deep drawing die need to be explained as follows:

[0057] First, before the positioning of the spread blank 18, a super-thin plastic film consistent with the shape of the spread blank 18 is covered on the lower surface of the spread blank 18; after the positioning of the spread blank is completed, a thickened plastic film is covered on the upper surface of the spread blank 18. For the blank preparation work before drawing, it is also necessary to pay attention to that the super-thin plastic film covered on the lower surface of the spread blank 18 has single-sided adhesion, and the adhesive surface is attached to the spread blank 18; the thickened plastic film covered on the upper surface of the spread blank 18 has an annular profile, and the inner and outer profiles are respectively pressed against the inner sealing ring 9 and the outer sealing ring 11 below. The purpose of covering the single-sided adhesion super-thin plastic film on the spread blank 18 is to reduce the friction between the sheet and the blank holder 5 and to improve the sealing effect; and the purpose of covering the thickened plastic film on the upper surface of the spread blank 18 is to make the spread blank 18 better sealed with the blank holder 5 as the fluid pressure increases.

[0058] Second, when the spread blank 18 is pressed, the static load of the blank holder 5 is not less than 3 times the rigid blanking drawing blank load; during the drawing forming, the dynamic load of the blank holder 5 is not less than 5 times the product of the projected area of the annular sunken surface 16 of the blank holder and the highest fluid pressure. For flexible blank loading drawing, it is also necessary to emphasize that the effective load of the liquid on the sheet is not equivalent to the true load of the blank holder 5, and the true load of the blank holder 5 only affects the sealing and lubrication effect, and is not directly related to the drawing quality and depth limit of the part 1. Increasing the blank holder load is to ensure the absolute sealing of the liquid high-pressure environment, and the improvement of the sealing condition is the guarantee of improving the lubrication effect.

[0059] Third, for high-difficulty parts in traditional drawing, the unit blank holder load is about 3-4 MPa, but the load uniformity and lubrication effect are obviously improved in the single-sided flexible friction state. The recommended unit blank force of the annular sunken surface 16 of the blank holder 5 corresponding to the upper surface of the spread blank 18 is 10-30 MPa. In the single-sided flexible friction state, even if the effective blank load of the sheet increases several times, the flow resistance of the flange edge 2 will not only not increase significantly, but also may be lower than that of rigid blank drawing. Therefore, the drawing method of the present application not only helps to improve the surface quality under high blank load, but also can realize the forming depth improvement under high lubrication effect.

[0060] Fourth, when the part 1 is unloaded after drawing, first, the hydraulic source connected with the pressurizing pipeline 14 is closed; then the concave die 4 is raised to release the load pressure, and the rising height of the concave die 4 during pressure relief is less than the difference between the thickness of the sealing ring in the natural state and the depth of the sealing groove, and the purpose of controlling the rising height of the concave die 4 is to ensure that the part 1 is separated from the concave die 4, and to avoid that the flange edge 2 of the part is stressed to produce large deformation.

[0061] In summary, the biggest difference between the drawing method of the present application and the traditional drawing method is that the concentrated common problem of the blank load in the traditional drawing can be completely avoided, and the single-sided flexible friction lubrication effect is significantly improved; it is convenient to use high lubrication and high blank load to improve the depth limit and surface quality. Thus, the purpose of the present application is achieved.

[0062] The above merely provides the preferred embodiment of the present application and not intended to limit the present application. Accordingly, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the scope of the present application.

Claims

1. A method for using an adjustable pressure flexible blank holder loading deep drawing die, wherein the adjustable pressure flexible blank holder loading deep drawing die is used to deep draw parts, characterized in that, Adjustable pressure flexible blank holder loading drawing die, comprising: a die (4), the die (4) profile matches with part (1) outer surface part, the profile matching part is part root fillet (3) and its both sides adjacent area; Blank holder (5), the upper surface of blank holder (5) is provided with annular depression surface (16) with shape matching with spread blank (18), the inner profile of annular depression surface (16) matches with part (1) outside wall root, for accommodating and positioning spread blank (18); Punch (6), the working surface of punch (6) matches with the lower surface of inside area of part root fillet (3), the lower straight wall section (7) of punch (6) working surface matches with the inner profile of blank holder depression surface (16); The die (4) and blank holder (5) seal adjustable pressure fluid medium on spread blank (18), so that the surface of spread blank (18) corresponding to annular depression surface (16) is in uniform flexible compression state, and spread blank (18) is drawn into part (1) on punch (6); The lower surface of die (4) is provided with inner sealing groove (8) and inner sealing ring (9) near part root fillet (3), outer sealing groove (10) and outer sealing ring (11) are arranged outside annular depression surface (16) of blank holder (5), liquid inlet hole (12) and liquid outlet hole (13) are arranged between inner sealing ring (9) and outer sealing ring (11), the liquid inlet hole (12) is connected with hydraulic source through pressure pipeline (14), and the liquid outlet hole (13) is connected with pressure control valve through pressure relief pipeline (15); The die (4) and blank holder (5) are further provided with zero gap matching profile (17) outside outer sealing groove (10) and outer sealing ring (11), and the zero gap matching profile (17) matches with the extension complementary surface of the outer surface of part flange edge (2); The matching gap of die (4) and blank holder (5) in annular depression surface (16) area is greater than the depth of annular depression surface (16), and is greater than the thickness of spread blank (18); The method comprises the following steps: 1) spread blank positioning preparation: the upper surface of blank holder (5) is lowest, and the lower surface of punch (6) working surface is higher than the lower surface of punch (6) working surface, and the spread blank (18) is arranged in the inner profile of annular depression surface (16) of blank holder (5); wherein, before positioning of spread blank (18), the lower surface of spread blank (18) is covered with ultrathin plastic film consistent with the shape of spread blank (18); after positioning of spread blank (18), the upper surface of spread blank (18) is covered with thickened plastic film; the ultrathin plastic film covered on the lower surface of spread blank (18) has single-sided adhesion, and the adhesion surface is attached to spread blank (18); the thickened plastic film covered on the upper surface of spread blank (18) is annular, and the inner profile and the outer profile are pressed to the lower surface of inner sealing ring (9) and outer sealing ring (11) respectively. 2) Unfolded blank compression: first lower the concave die (4) to make it pre-compress the upper surface of the unfolded blank (18) with the static blank holder (5), then fill fluid medium from the fluid filling hole (12) of the concave die (4) and pressurize it to a predetermined pressure, so that the unfolded blank (18) is in a flexible compression state on the annular depression surface (16) of the blank holder (5); wherein, when the unfolded blank (18) is compressed, the static load of the blank holder (5) is not less than 3 times the rigid blanking load; 3) Flexible blanking: simultaneously lower the concave die (4) and the blank holder (5), and through the control of fluid pressure, the unfolded blank (18) in the annular depression surface (16) area is in a uniform loading environment and the blank holder (5) generates single-sided flexible friction to complete the deep drawing forming of the part (1); wherein, during the deep drawing forming, the dynamic load of the blank holder (5) is not less than 5 times the product of the projection area of the blank holder annular depression surface (16) and the highest fluid pressure; 4) Part unloading: first remove the load pressure of the concave die (4) in the static state of the blank holder (5) to make the deep drawn part (1) separate from the concave die (4) under the pressure of the remaining fluid in the pipeline, then sequentially raise the concave die (4) and the blank holder (5), and separate the part (1) from the convex die (6); wherein, when the part (1) is unloaded after deep drawing, first close the hydraulic source connected with the pressurizing pipeline (14); then appropriately raise the concave die (4) to remove the load pressure, and the rising height of the concave die (4) during pressure relief is less than the difference between the thickness of the sealing ring in the natural state and the depth of the sealing groove.

2. A method of using an adjustable pressure flexible blank holder drawing die according to claim 1, wherein, In the step 3), during the deep drawing forming, the unit blanking force of the blank holder annular depression surface (16) corresponding to the upper surface of the unfolded blank (18) is 10-30 Mpa.

Images