Pressure-adjustable flexible blank pressing loading deep drawing die and using method thereof

Abstract

The invention belongs to the technical field of aircraft manufacturing, and discloses a pressure-adjustable flexible blank pressing loading deep drawing die and a using method thereof.The deep drawing die comprises a female die, a blank pressing ring and a male die, the molded surface of the female die is partially matched with the outer surface of a part, and the upper surface of the blank pressing ring is provided with a sunken surface matched with an unfolded blank in shape; 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 pressure-adjustable fluid medium is tightly pressed on the upper surface of the unfolded blank in a sealed mode through the female die and the blank holder, and part drawing forming is carried out on the male die. And the technical problem of mutual contradiction of edge pressing load concentration during traditional deep drawing load increase is solved. A fluid medium flexible edge pressing mode is adopted, contact friction does not exist between the female die and the flange edge of the part, and the edge pressing load uniformity is not affected when the die bears deformation; the lubricating device has the remarkable advantages of good lubricating effect, low mold processing cost, high technical universality and the like.

Description

Technical Field

[0001] The invention application belongs to the field of plastic processing technology in aircraft manufacturing, and specifically relates to an adjustable pressure flexible edge-pressing loading deep drawing die and a method of using the same, which is particularly suitable for fluid-loaded edge-pressing deep drawing of deep-cavity, difficult parts with large flange thickening distribution and width differences. Background Art

[0002] It is well known that local concentration of blank holder load is a common problem that has long plagued the yield rate of complex deep drawing parts. The larger the blank holder load of traditional rigid deep drawing, the better the surface quality of the parts, but the lower the yield rate. The reason is that as the blank holder load increases, the deformation of the blank holder ring increases, and the concentration of the blank holder load causes a sharp increase in the flow resistance in the local area. Usually, the forming depth of circular parts is significantly higher than that of irregularly shaped parts. The reason is that the more regular the shape, the more uniform the thickening distribution of the flange edge during the forming process, and the easier it is to delay the rupture caused by the local concentration of the blank holder load. On the contrary, the more complex the shape, the easier it is for the flange edge to produce a large thickness difference during the forming process, and the blank holder load concentration is quickly formed in the local area with the largest thickness of the flange edge, and the corresponding deep drawing force transmission area is quickly broken due to overload. Especially for box-shaped deep cavity parts with a large flange width in the corner area, the thickness and width of the flange edge are significantly greater than the remaining blank holder areas during deep drawing, and it is very easy to break at the corresponding corner of the punch radius. In addition, it is difficult to ensure uniform pressure in each area of ​​the blank holder surface due to many factors such as the distribution of blank thickness deviation, the manufacturing matching accuracy of the die blank holder surface, and the difference in die load deformation. Even with the same batch of raw materials and the same set of molds, there are differences in the drawing effects, which greatly increases the difficulty of stable batch production of similar parts.

[0003] In actual deep drawing, in order to improve the surface quality of the drawn parts, it is necessary to increase the blank holder load as much as possible, while in order to increase the yield rate, it is necessary to improve the lubrication effect; however, increasing the blank holder load and reducing friction and uniform load distribution are always extremely contradictory. In order to solve the risk of a sharp increase in local friction due to an increase in the blank holder load, the applicant's prior patent publication number is: CN 116727524 A, the essence of which is to make the loads of multiple variable gap blanking surface areas more uniform through the difference in the degree of compression of the double-sided plastic film. Compared with the conventional rigid blank holder method, this technology can increase the forming depth by nearly double the blank holder load conditions; however, as the blank holder load further increases, the risk of blank holder load concentration will be greater. This public technology can only alleviate the blank holder load concentration effect within a small range of blank holder load increase, and cannot achieve the free adjustment of the effective blank holder load of the blank on demand. Summary of the invention

[0004] The present invention is applied to overcome the influence of factors such as mold deformation, thickness deviation of blank, irregular shape and uneven deformation of traditional rigid edge-holding drawing; local edge-holding load is easily concentrated, corresponding to local overload of force transmission area, and restricts the common problem of contradiction between improving the forming depth and quality of complex parts. A flexible edge-holding loading drawing die with adjustable pressure and its use method are proposed, which applies uniform edge-holding load to the flange edge through fluid medium in a high-pressure closed environment; when the single-sided flexible contact of the blank with the die is in state, the edge-holding load can be significantly increased and friction can be reduced, so as to achieve the purpose of improving the forming depth and forming quality of complex parts at the same time.

[0005] In order to achieve the above invention objectives, the technical solutions adopted in this application are as follows:

[0006] A flexible edge-pressing loading drawing die with adjustable pressure, comprising:

[0007] Concave mold, the concave mold surface matches the outer surface of the part, and the matching part of the mold surface is the root fillet of the part and the adjacent areas on both sides;

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

[0009] A punch, wherein the punch working surface matches the lower surface of the inner area of ​​the fillet at the root of the part, and the lower straight wall section of the punch working surface matches the inner contour of the sunken surface of the blank holder;

[0010] The concave die and the blank holder seal the adjustable pressure fluid medium on the unfolded blank, so that the surface of the unfolded blank corresponding to the annular sunken surface is in a uniform flexible compression state, and the unfolded blank is deep-drawn into a part on the convex die.

[0011] As a further solution of the present invention: the lower surface of the die is provided with an inner sealing groove and an inner sealing ring at the fillet near the root of the part, an outer sealing groove and an outer sealing ring are provided on the outer side of the annular sunken surface of the pressure ring, and a liquid filling hole and a liquid drain hole are provided between the inner sealing ring and the outer sealing ring, the liquid filling hole is connected to the hydraulic source through a pressurized pipeline, and the liquid drain hole is connected to the pressure control valve through a pressure relief pipeline.

[0012] As a further solution of the present invention: the die and the blank holder are further provided with a zero-gap matching surface on the outer side 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 solution of the present invention: the matching gap between the die and the blank holder in the annular depressed surface area of ​​the blank holder>the depth of the annular depressed surface≥the thickness of the unfolded blank.

[0014] A method for using a flexible pressure-adjustable edge-loading drawing die, using the flexible pressure-adjustable edge-loading drawing die to perform deep drawing forming on a part, comprising the following steps:

[0015] 1) Preparation for positioning the unfolded blank: Raise the blank holder so that the lowest point of its upper surface is higher than the punch working surface, and place the unfolded blank inside the contour of the annular sunken surface of the blank holder;

[0016] 2) Compressing the unfolded blank: firstly, the concave die is lowered so that it and the stationary blank holder ring pre-compress the upper surface of the unfolded blank, and then the fluid medium is filled from the liquid filling hole of the concave die and the pressure is increased to a predetermined pressure, so that the annular sunken surface area of ​​the blank holder ring corresponding to the upper surface of the unfolded blank is in a flexible and compressed state;

[0017] 3) Flexible blank holder drawing: The die and blank holder are lowered synchronously, and the fluid pressure is controlled so that the blank in the annular sunken surface area generates single-sided flexible friction with the blank holder in a uniform loading environment to complete the deep drawing of the part;

[0018] 4) Parts unloading: First, remove the die load and release the pressure instantly when the blank holder is stationary, so that the drawn part can be separated from the die under the pressure generated by the remaining fluid in the pipeline, and then raise the die and the blank holder in sequence to separate the part from the punch.

[0019] As a further solution of the present invention, the following steps are also included: before the unfolded blank is positioned, an ultra-thin plastic film having the same shape as the unfolded blank is covered on the lower surface; after the unfolded blank is positioned, a thickened plastic film is covered on the upper surface of the unfolded blank.

[0020] As a further solution of the present invention: the ultra-thin plastic film covering the lower surface of the unfolded blank has single-sided adhesion, and the adhesive surface is attached to the unfolded blank. The thickened plastic film covering the upper surface of the unfolded blank is ring-shaped, and its inner and outer contours are respectively pressed under the inner sealing ring and the outer sealing ring.

[0021] As a further solution of the present invention: in the step 2), when the blank is unfolded and pressed, the static load of the blank holder is not less than 3 times the blank holder load of the rigid blank holder during deep drawing; in the step 3), during deep drawing, the dynamic load of the blank holder is not less than 5 times the product of the projection area of ​​the annular sunken surface of the blank holder and the maximum pressure of the fluid.

[0022] As a further solution of the present invention: in the step 3), during deep drawing, the recommended unit blank holding force of the annular sunken surface of the blank holding ring corresponding to the upper surface of the unfolded blank is 10 to 30 MPa.

[0023] As a further solution of the present invention: in the step 4), when the part is unloaded after deep drawing, the hydraulic source connected to the pressurized pipeline is first closed; then the die is appropriately raised to remove the load and release the pressure. When releasing the pressure, the height of the die rises 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 beneficial effects of this application are:

[0025] 1. The deep drawing die of the present application can realize single-sided flexible friction edge pressing deep drawing, which can improve the lubrication effect of the flange edge by several times compared with the traditional double-sided contact rigid edge pressing die, making it easier to use a higher edge pressure load to improve the surface quality of the drawn part.

[0026] 2. The manufacturing of the drawing die in this application only requires partial matching between the die and the edge area of ​​the blank holder, and the pressing surface area only requires one side of the blank holder to ensure accuracy; 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 deep drawing die of this application uses high-pressure liquid to load the flange edge of the part, and the gap between the die and the blank holder corresponding to the effective pressing area is greater than the thickness of the blank; compared with the traditional double-sided contact rigid blank holder die, it can completely eliminate the common problem of easy deformation of the die in a high-load environment and concentrated blank holder load.

[0028] 4. The drawing die and forming method adopted in this application can simultaneously meet the requirements of high pressure side load and high lubrication effect drawing engineering application; it has significant advantages such as easy implementation and strong versatility.

[0029] The present application is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] In the attached picture:

[0032] Figure 1 This is a schematic diagram of the typical parts structure applicable to this application;

[0033] Figure 2 A schematic diagram of the drawing die and forming principle of a typical part applicable to this application;

[0034] Figure 3 This is a schematic diagram of the die structure of a typical part drawing die applicable to this application;

[0035] Figure 4 This is a schematic diagram of the punch structure of a typical part drawing die applicable to this application;

[0036] Figure 5This is a schematic diagram of the blank holder structure of a typical part drawing die applicable to this application;

[0037] Figure 6 Schematic diagram of the blank pressing principle before deep drawing of a typical part applicable to this application.

[0038] Explanation of the reference numerals in the figure: 1. Part, 2. Flange, 3. Root fillet, 4. Die, 5. Blank holder, 6. Punch, 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 drain hole, 14. Pressurization pipeline, 15. Pressure relief pipeline, 16. Sunken surface, 17. Zero gap matching surface, 18. Unfolded blank. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] First, we introduce the defects of traditional deep drawing process for typical parts applicable to this application:

[0041] See attached Figure 1 The rectangular box with a widened flange 2 is one of the representative parts 1 applicable to this application. Due to the irregular structure of part 1, the flange 2 is prone to obvious thickening differences in various areas during the drawing process, and the load of the die on the flange 2 is all concentrated in the area with large thickness. The traditional rigid edge pressing drawing die and forming method are limited by many factors such as the distribution of blank thickness deviation, the manufacturing matching accuracy of the die flange 2 area, and the difference in die load deformation. It is difficult to ensure uniform pressure in various areas of the flange 2. The deep drawing of parts with irregular shapes and flanges always faces the common problem of the contradiction between the increase in edge pressing load and the concentration of load deformation, which seriously restricts the improvement of forming depth and quality.

[0042] Next, we introduce the mold technology solutions for typical parts applicable to this application:

[0043] In order to solve the above problems existing in the deep drawing of irregular parts with existing rigid blank holding technology, refer to the attached Figure 2 To Attachment Figure 6 The main technical solutions of the drawing die in this application are as follows:

[0044] A drawing die with adjustable pressure and flexible blank holder loading, the drawing die comprises a die 4, a blank holder ring 5, and a punch 6; the die 4 has a profile that matches the outer surface of a part 1, and the profile matching part is the root fillet 3 of the part and the adjacent areas on both sides. The upper surface of the blank holder ring 5 is provided with an annular sunken surface 16 whose outer contour matches the shape of the unfolded blank 18, and the inner contour of the sunken surface 16 matches the root of the outer wall of the 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 contour of the sunken surface 16 of the blank holder ring. The die 4 and the blank holder ring 5 seal the adjustable pressure fluid medium on the unfolded blank 18, so that the surface of the unfolded blank 18 corresponding to the annular sunken surface 16 is in a uniform and flexible compression state, and the unfolded blank 18 is deep-drawn into the part 1 on the punch 6.

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

[0046] First, in order to achieve the sealing of flange side 2 during deep drawing and take into account the effective pressure load, it can be freely adjusted as needed. Figure 2 , Attachment Figure 6 An inner sealing groove 8 and an inner sealing ring 9 are provided on the lower surface of the die 4 near the fillet 3 at 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 sunken surface 16 of the blank holder ring 5, a filling hole 12 and a drainage hole 13 are provided between the inner sealing ring 9 and the outer sealing ring 11, the filling hole 12 is connected to the hydraulic source through a pressurizing pipeline 14, and the drainage hole 13 is connected to the 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] Second, in order to prevent the pressure ring 5 from being deformed under high load conditions and to improve the sealing effect, refer to the attached Figure 2 The die 4 and the blank holder 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 mold is to prevent the blank holder 5 from being deformed due to excessive load.

[0048] Third, in order to achieve uniform pressure edge load and ultra-high lubrication effect, refer to the attached Figure 2 , Attachment Figure 5 , the matching gap between the die 4 and the blank holder 5 in the annular depressed surface 16 of the blank holder>the depth of the annular depressed surface 16≥the thickness of the unfolded blank 18; when the matching gap in the depressed surface 16 is greater than the thickness of the sheet material, even if the blank holder 5 is deformed, the unfolded blank 18 only has single-sided flexible friction contact with the blank holder 5.

[0049] To sum up, the biggest difference between the drawing die of the present application and the traditional drawing die is that: the friction between the upper surface of the sheet and the die 4 is almost negligible, and only the pressure ring 5 and the sheet produce single-sided flexible friction; and the pressure ring 5 is not easy to deform under high pressure, and even if it is deformed, it will not affect the load uniformity, and its lubrication effect can be improved several times, and even the improvement effect can reach several times.

[0050] Next, we will introduce the use of this application's drawing die to form typical parts:

[0051] Refer to the attached method for using the above-mentioned adjustable pressure flexible edge loading drawing die to form parts. Figure 1 To Attachment Figure 6 The main implementation steps are as follows:

[0052] 1) Preparation for blank positioning: Raise the blank holder 5 so that the lowest point of its upper surface is higher than the top of the working surface of the punch 6, and place the unfolded blank 18 inside the outer contour of the annular sunken surface 16 of the blank holder 5.

[0053] 2) Blank pressing: first lower the die 4 so that it and the stationary pressure ring 5 pre-press the upper surface of the unfolded blank 18, then fill the fluid medium from the liquid filling hole 12 of the die 4 and increase the pressure to a predetermined pressure, so that the annular sunken surface 16 area corresponding to the upper surface of the unfolded blank 18 in the pressure ring 5 is in a flexible pressing state.

[0054] 3) Flexible blank holder drawing: The die 4 and the blank holder 5 are lowered synchronously, and the fluid pressure is controlled so that the expanded blank 18 in the annular sunken surface 16 area generates single-sided flexible friction with the blank holder 5 in a uniform loading environment to complete the deep drawing of the part 1.

[0055] 4) Part unloading: First, remove the load and pressure of the die 4 instantly when the blank holder 5 is stationary, so that the part 1 after drawing can be separated from the die 4 under the pressure generated by the remaining fluid in the pipeline, and then raise the die 4 and the blank holder 5 in turn to separate the part 1 from the punch 6.

[0056] The following aspects need to be emphasized for the technical points of using deep drawing dies:

[0057] First, before the unfolded blank 18 is positioned, an ultra-thin plastic film of the same shape is covered on the lower surface of the unfolded blank 18; after the unfolded blank is positioned, a thickened plastic film is covered on the upper surface of the unfolded blank 18. In terms of the preparation of the blank before deep drawing, it is also important to note that: the ultra-thin plastic film covering the lower surface of the unfolded blank 18 has single-sided adhesion, and the adhesive surface is attached to the unfolded blank 18; the thickened plastic film covering the upper surface of the unfolded blank 18 has a ring-shaped contour, and its inner and outer contours are respectively pressed under the inner sealing ring 9 and the outer sealing ring 11. The purpose of covering the unfolded blank 18 with a single-sided adhesive ultra-thin plastic film 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 upper surface of the unfolded blank 18 with a thickened plastic film is to make the unfolded blank 18 more sealed with the blank holder 5 as the fluid pressure increases.

[0058] Second, when the blank 18 is unfolded and pressed, the static load of the blank holder 5 is not less than 3 times the blank holder load of the rigid blank holder drawing; during deep drawing, the dynamic load of the blank holder 5 is not less than 5 times the product of the projection area of ​​the annular sunken surface 16 of the blank holder and the maximum pressure of the fluid. Regarding the flexible blank holder loading deep drawing, it should also be emphasized that the effective load of the liquid on the sheet is not equivalent to the real load of the blank holder 5. The real load of the blank holder 5 only affects the sealing and lubrication effect, and has no direct relationship with the drawing quality and depth limit of the part 1. The purpose of increasing the blank holder load is to ensure that the liquid high-pressure environment is absolutely sealed, and the improvement of sealing conditions is the guarantee for improving the lubrication effect.

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

[0060] Fourth, when the part 1 is unloaded after deep drawing, the hydraulic source connected to the pressurized pipeline 14 is first closed; then the die 4 is raised to remove the load and release the pressure. When releasing the pressure, the rising height of the die 4 is less than the difference between the thickness of the sealing ring and the depth of the sealing groove in the natural state. The purpose of controlling the rising height of the die 4 is to ensure that the part 1 is separated from the die 4 and to avoid large deformation of the flange edge 2 of the part due to force.

[0061] In summary, the biggest difference between the deep drawing method of the present application and the traditional deep drawing method is that it can completely avoid the common problem of concentrated edge pressure load in traditional deep drawing, and at the same time significantly improve the single-sided flexible friction lubrication effect; it is convenient to use high lubrication and high pressure edge load to simultaneously achieve the purpose of improving the depth limit and surface quality. So far, the purpose of the present invention has been achieved.

[0062] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flexible pressure-adjustable edge-loading drawing die, characterized in that: include: Concave mold, the concave mold surface matches the outer surface of the part, and the matching part of the mold surface is the root fillet of the part and the adjacent areas on both sides; A blank holder ring, wherein the upper surface of the blank holder ring is provided with an annular sunken surface whose outer contour matches the shape of the unfolded blank, and the inner contour of the sunken surface matches the root of the outer wall of the part; A punch, wherein the punch working surface matches the lower surface of the inner area of ​​the fillet at the root of the part, and the lower straight wall section of the punch working surface matches the inner contour of the sunken surface of the blank holder; The concave die and the blank holder seal the adjustable pressure fluid medium on the unfolded blank, so that the surface of the unfolded blank corresponding to the annular sunken surface is in a uniform flexible compression state, and the unfolded blank is deep-drawn into a part on the convex die.

2. The adjustable pressure flexible edge-loading drawing die according to claim 1 is characterized in that: The lower surface of the die is provided with an inner sealing groove and an inner sealing ring at the fillet near the root of the part, an outer sealing groove and an outer sealing ring are provided on the outer side of the annular sunken surface of the pressure ring, and a liquid filling hole and a liquid discharge hole are provided between the inner sealing ring and the outer sealing ring. The liquid filling hole is connected to the hydraulic source through a pressurized pipeline, and the liquid discharge hole is connected to the pressure control valve through a pressure relief pipeline.

3. The adjustable pressure flexible edge-holding loading drawing die according to claim 2 is characterized in that: The die and the blank holder are also provided with zero-gap matching profiles on the outer sides of the outer sealing groove and the outer sealing ring, and the zero-gap matching profiles match the extended supplementary surfaces of the outer surfaces of the flange edges of the parts.

4. The adjustable pressure flexible edge-holding loading drawing die according to any one of claims 1 to 3, characterized in that: The matching gap between the die and the blank holder in the annular depressed surface area of ​​the blank holder ring>the depth of the annular depressed surface≥the thickness of the unfolded blank.

5. A method for using a pressure-adjustable flexible edge-loading drawing die, wherein the pressure-adjustable flexible edge-loading drawing die according to claim 4 is used to perform deep drawing on a part, characterized in that: The steps include: 1) Preparation for positioning the unfolded blank: Raise the blank holder so that the lowest point of its upper surface is higher than the punch working surface, and place the unfolded blank inside the contour of the annular sunken surface of the blank holder; 2) Compressing the unfolded blank: firstly, the concave die is lowered so that it and the stationary blank holder ring pre-compress the upper surface of the unfolded blank, and then the fluid medium is filled from the liquid filling hole of the concave die and the pressure is increased to a predetermined pressure, so that the annular sunken surface area of ​​the blank holder ring corresponding to the upper surface of the unfolded blank is in a flexible and compressed state; 3) Flexible blank holder drawing: The die and blank holder are lowered synchronously, and the fluid pressure is controlled so that the blank in the annular sunken surface area generates single-sided flexible friction with the blank holder in a uniform loading environment to complete the deep drawing of the part; 4) Parts unloading: First, remove the die load and release the pressure instantly when the blank holder is stationary, so that the drawn part can be separated from the die under the pressure generated by the remaining fluid in the pipeline, and then raise the die and the blank holder in sequence to separate the part from the punch.

6. The method for using a pressure-adjustable flexible edge-holding loading drawing die according to claim 5 is characterized in that: The method also includes the following steps: before positioning the unfolded blank, covering the lower surface of the unfolded blank with an ultra-thin plastic film that matches its shape; after positioning the unfolded blank, covering the upper surface of the unfolded blank with a thickened plastic film.

7. The method for using a pressure-adjustable flexible edge-holding loading drawing die according to claim 6 is characterized in that: The ultra-thin plastic film covering the lower surface of the unfolded blank has single-sided adhesiveness, and the adhesive surface is attached to the unfolded blank. The thickened plastic film covering the upper surface of the unfolded blank is annular in shape, and its inner and outer contours are respectively pressed under the inner sealing ring and the outer sealing ring.

8. The method for using a pressure-adjustable flexible edge-holding loading drawing die according to claim 5, characterized in that: In the step 2), when the blank is unfolded and pressed, the static load of the blank holder is not less than 3 times the blank holder load of the rigid blank holder during deep drawing; in the step 3), during deep drawing, the dynamic load of the blank holder is not less than 5 times the product of the projected area of ​​the annular sunken surface of the blank holder and the maximum pressure of the fluid.

9. The method for using a flexible edge-pressing drawing die with adjustable pressure according to claim 8 is characterized in that: In the step 3), during deep drawing, the recommended unit blank holding force of the annular sunken surface of the blank holder corresponding to the upper surface of the unfolded blank is 10 to 30 MPa.

10. The method for using a pressure-adjustable flexible edge-holding loading drawing die according to claim 5, characterized in that: In step 4), when the part is unloaded after deep drawing, the hydraulic source connected to the pressurized pipeline is first closed; then the die is appropriately raised to remove the load and release the pressure. During the pressure release, the height of the die rises less than the difference between the thickness of the sealing ring in the natural state and the depth of the sealing groove.

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