Method for controlling outer edge wrinkling in concave-convex thin-wall disc rubber bag pressing

Abstract

The control method for outer edge wrinkling in concave-convex thin-wall disc rubber bag pressing comprises the steps that according to the designed shape and size of a concave-convex thin-wall disc part, the size used for forming a circular plate is inversely calculated, process allowance is added to the outer edge of the plate, and arc-shaped notches evenly distributed in the annular direction are cut in the process allowance of the outer edge of the plate; according to the shape and size of the concave-convex thin-wall disc part, a rigid mold with a concave-convex molded surface is manufactured in a matched mode, and the circular plate is laid on the rigid mold and is positioned, aligned and fixed; a circular rubber pad is selected and laid on the circular plate, rubber bag forming equipment is started, a rubber bag liquid chamber of the rubber bag forming equipment is gradually pressurized, and the rubber pad enables the circular plate to deform under the action of the pressure of the rubber bag liquid chamber and is gradually attached to the concave-convex molded surface on the rigid mold below; and after the pressure P of the rubber bag liquid chamber reaches a set value, the part is taken out through pressure relief, and the machining efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of rubber bladder hydroforming of aerospace sheet metal parts, and particularly relates to a method for controlling the wrinkling of the outer edge during the rubber bladder pressing of a concave-convex thin-walled disc. Background Art

[0002] The aerospace field contains a large number of sheet metal parts. The concave-convex thin-walled disc is a typical type of component among them. Due to the complex concave-convex surface features of this type of component, the traditional steel die stamping forming method requires multiple sets of dies to be formed in multiple times, which has problems such as many processing procedures and long production cycles. The rubber bladder pressing process is a soft die forming method that uses the pressure of the rubber bladder liquid chamber to provide the active forming force, so that the metal sheet gradually fits the rigid die under the action of the liquid chamber pressure, and then obtains the shape of the part. It has the advantages of high forming efficiency, good surface quality of the part, and low manufacturing cost of the tooling, and is an advantageous technical method for the high-efficiency and high-quality forming of concave-convex thin-walled discs.

[0003] During the rubber bladder pressing process of thin-walled sheet metal parts, wrinkling defects are extremely likely to occur, which affects the forming quality of the parts. The traditional processing methods for controlling the wrinkling of thin-walled sheet metal parts during rubber bladder pressing are as follows:

[0004] 1. The method for controlling the wrinkling phenomenon during the rubber bladder forming of parts with convex bent edge features disclosed in (CN112828118B) proposes to add a control block that fits the side wall of the tooling on one side of the convex bent edge of the forming tooling to increase the circumferential support force during the deformation of the part, thereby preventing the part from wrinkling. However, this method of adding a control block to suppress wrinkling is only applicable to the rubber bladder pressing process of parts with convex bent edge features and is not applicable to the rubber bladder pressing of concave-convex thin-walled discs.

[0005] 2. For the forming process of thin-walled sheet metal parts with a blank holding function, setting draw beads on the die or blank holder in contact with the sheet metal is also an effective method for controlling part wrinkling. A method for controlling the wrinkling of the sheet metal during the fluid filling forming process disclosed in (CN115945572A) changes the traditional draw beads into a dot matrix distribution of small pits to meet the wrinkling control requirements of deep cavity parts during fluid filling forming. However, the design of draw beads or dot matrix pits needs to cooperate with the blank holding force to play a role in suppressing wrinkling. In the rubber bladder pressing process, the blank holding force increases gradually from zero with the pressure of the rubber bladder liquid chamber and is relatively small. Therefore, the design of draw beads or dot matrix pits cannot effectively suppress the occurrence of wrinkling in the rubber bladder pressing process. Moreover, the material of the concave-convex thin-walled disc is prone to thinning during the later stage of rubber bladder pressing, and the design of draw beads or dot matrix pits increases the resistance of the material to flow inward, which is extremely likely to cause excessive thinning or even cracking defects of the material during the later stage of pressing.

[0006] In the invention patent of (CN114247810B), a forming die and a forming method for a rubber bladder pressing annular parts with opposite-direction bent edges are disclosed. Aiming at the problem that wrinkles are likely to occur in the process of rubber bladder pressing for parts with opposite-direction bent edges, it is proposed to use a steel die to press the outer edge of the sheet metal during the pressing process to inhibit the occurrence of wrinkling defects during the outer edge bending process; however, the method of using a steel die to press the outer edge of the sheet metal requires continuous adjustment of the pressing force of the steel die. When the pressing force is too small, it cannot play a role in suppressing wrinkles, and when the pressing force is too large, the resistance to the inward flow of the material will increase sharply, which is extremely likely to cause excessive thinning or even cracking defects of the material in the later stage of pressing.

[0007] In view of this, the present invention is particularly proposed. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for controlling the outer edge wrinkling in the rubber bladder pressing of concave-convex thin-walled discs, so as to realize the efficient and high-quality forming and manufacturing of such parts. There are many technical beneficial effects of the technical solution of this case, as introduced below:

[0009] A method for controlling the outer edge wrinkling in the rubber bladder pressing of concave-convex thin-walled discs, which is applicable to the processing of parts by a rubber bladder forming device. The control method includes:

[0010] Step S1: Calculate the size of the circular sheet metal used for forming according to the shape and size of the designed concave-convex thin-walled disc part, and add a process allowance to the outer edge of the sheet metal, and cut circumferentially evenly distributed arc-shaped notches on the process allowance of the outer edge of the sheet metal. The arc-shaped notches are used to reduce the circumferential compressive stress at the outer edge of the sheet metal during the rubber bladder pressing process;

[0011] Step S2: Manufacture a rigid die with a concave-convex surface according to the shape and size of the concave-convex thin-walled disc part, and install the rigid die on the processing platform of the rubber bladder forming device for debugging;

[0012] Step S3: Lay the circular sheet metal on the rigid die and perform positioning, alignment and fixation;

[0013] Step S4: Select a circular rubber pad and lay it on the circular sheet metal. The circular rubber pad is used to transfer the pressure of the rubber bladder liquid chamber and protect the arc-shaped notches;

[0014] Step S5: Start the rubber bladder forming device, and the rubber bladder liquid chamber of the rubber bladder forming device is gradually pressurized. Under the action of the pressure of the rubber bladder liquid chamber, the rubber pad causes the circular sheet metal to deform and gradually fit the concave-convex surface on the lower rigid die;

[0015] Step S6: After the pressure P of the rubber bladder liquid chamber reaches the set value, release the pressure and take out the part.

[0016] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0017] The method of the present invention is to process an arc-shaped notch on the sheet metal to prevent wrinkling defects during the sheet metal forming process. Compared with the traditional method of suppressing wrinkling by die design, it is simpler and more convenient, can avoid the problem of repeatedly modifying the die due to inappropriate die design, thereby reducing the repair processing cost of the die, and significantly shortening the trial production cycle of parts. Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of a circular sheet metal with circumferentially uniformly distributed arc-shaped notches;

[0020] Figure 2 It is a flowchart of the control method of the present invention;

[0021] Figure 3 It is a schematic diagram of the rubber bladder pressing process of a concave-convex thin-walled disc, where,

[0022] 1. Circular sheet metal; 2. Rigid die; 3. Circular rubber pad. Detailed Embodiments

[0023] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0024] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the aspects can be practiced without these specific details. To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0025] As Figures 1 to 3 shown in the control method for preventing wrinkling at the outer edge of the concave-convex thin-walled disc rubber bladder press forming, which is applicable to the processing of parts by rubber bladder forming equipment. The control method includes,

[0026] Step S1: According to the shape and size of the designed concave-convex thin-walled disc part, inversely calculate (using sheet metal simulation software) the size of the circular blank for forming, and add a process margin to the outer edge of the blank. And cut circumferentially evenly distributed arc-shaped notches on the process margin at the outer edge of the circular blank. The arc-shaped notches are used to reduce the circumferential compressive stress at the outer edge of the blank during the rubber bladder press forming process. That is, the arc-shaped notches can absorb the circumferential compressive stress through deformation during the press forming process, thereby reducing the wrinkling tendency of the thin-walled circular blank. Specifically, cutting the circumferentially evenly distributed arc-shaped notches on the outer edge of the blank includes,

[0027] Cutting circumferentially evenly distributed arc-shaped notches on the process margin at the outer edge of the blank. Among them, the depth h of the arc-shaped notch is 0.05 - 0.15 times the radius R of the circular blank, and the radius y of the arc-shaped notch is 1 - 2 times the depth h of the arc-shaped notch, and the number n of the arc-shaped notches is 10 - 20, and they are evenly distributed circumferentially along the outer edge of the process margin. By cutting circumferentially evenly distributed arc-shaped notches on the outer edge of the thin-walled circular blank, the circumferential compressive stress at the outer edge of the blank during the rubber bladder press forming process is reduced, thereby preventing the appearance of wrinkling defects at the outer edge of the blank during the rubber bladder press forming process. The arc-shaped notches can not only prevent the appearance of wrinkling defects during the blank forming process, but also reduce the frictional force between the blank and the mold, thereby reducing the resistance to the inward flow of the material and avoiding the occurrence of excessive thinning or even cracking defects due to excessive resistance to the inward flow of the material.

[0028] Step S2: Fabricate a rigid mold with a concave-convex surface according to the shape and size of the concave-convex thin-walled disc part. The rigid mold is used for supporting and processing. The rigid mold is placed on the rubber bladder forming equipment to support the circular blank, and the rigid mold is installed on the processing platform of the rubber bladder forming equipment for debugging. Specifically,

[0029] The concave and convex surfaces on the rigid die are arranged in mirror symmetry. Preferably, the thickness or height of the concave and convex surfaces near the center of the rigid die is greater than that of the concave and convex surfaces far from the center of the rigid die.

[0030] Step S3: Place the circular blank on the rigid die and perform positioning, alignment, and fixation.

[0031] Step S4: Select a circular rubber pad and place it on the circular blank. The circular rubber pad is used to transfer the pressure of the rubber bladder chamber and protect the arc-shaped notch. Preferably, the radius B of the circular rubber pad is greater than the radius R of the circular blank, and it can cover the circular blank and the process allowance. On the one hand, the circular rubber pad protects the arc-shaped notch, and on the other hand, it transfers the pressure of the rubber bladder chamber.

[0032] Step S5: Start the rubber bladder forming equipment. The pressure in the rubber bladder chamber of the rubber bladder forming equipment gradually increases. Under the action of the pressure in the rubber bladder chamber, the rubber pad causes the circular blank to deform and gradually conform to the concave and convex surfaces on the lower rigid die.

[0033] Step S6: After the pressure P in the rubber bladder chamber reaches the set value, relieve the pressure and take out the part.

[0034] The method of the present invention has stronger versatility and better surface quality of the part compared with the traditional method of suppressing wrinkling by adding drawbeads on the die. Since there are drawbeads on the part after forming in the traditional method of suppressing wrinkling by adding drawbeads on the die, it affects the subsequent forming and assembly of the part. Therefore, it is mainly used for one-time forming. However, the arc-shaped notch in the present invention does not affect the subsequent forming and assembly, so it is also applicable to multiple forming, with stronger versatility. In addition, the surface of the part is prone to scratches and indentations due to the influence of the drawbeads in the traditional method of suppressing wrinkling by adding drawbeads, while this situation does not exist in the method of the present invention. Therefore, the surface quality of the part is better, and the arc-shaped notch is processed on the blank to prevent wrinkling defects during the blank forming process, which is simpler and more convenient than the traditional method of suppressing wrinkling relying on die design, can avoid the problem of repeated die repair due to inappropriate die design, and thus reduce the repair processing cost of the die and significantly shorten the trial production cycle of the part. Only need to cut out appropriate circumferentially evenly distributed arc-shaped notches on the outer edge of the blank, without adjusting the die and forming parameters, and the technical level requirements for process personnel are not high, which is conducive to the application and popularization of this method.

[0035] Illustrative examples

[0036] This embodiment provides a method for controlling wrinkling at the outer edge in the rubber bladder pressing of a concave-convex thin-walled disc, as Figure 1 shown. This method cuts out circumferentially evenly distributed arc-shaped notches on the outer edge of the thin-walled circular blank to reduce the circumferential compressive stress at the outer edge of the blank during the rubber bladder pressing process, thereby preventing wrinkling defects from occurring at the outer edge of the blank during the rubber bladder pressing process.

[0037] The implementation steps of the method of the present invention and the embossing and debossing thin-walled disc rubber bladder forming process are respectively as shown in Figure 2 and Figure 3 as follows. The specific process is as follows:

[0038] Step S1: According to the shape and size of the embossing and debossing thin-walled disc part, inversely calculate the size of the circular blank for forming, and appropriately increase the process allowance at the outer edge of the blank for cutting circumferentially uniformly distributed arc-shaped notches.

[0039] Step S2: Design the size and quantity of the arc-shaped notches circumferentially uniformly distributed on the outer edge of the circular blank, and cut out the designed circumferentially uniformly distributed arc-shaped notches on the outer edge of the circular blank to obtain a circular blank 1 with circumferentially uniformly distributed arc-shaped notches. The depth h of the arc-shaped notch is 0.05 - 0.15 times the radius R of the circular blank, the radius y of the arc-shaped notch is 1 - 2 times the depth h of the arc-shaped notch, the quantity n of the arc-shaped notches is 10 - 20, and they are uniformly distributed along the circumferential direction on the outer edge of the circular blank.

[0040] Step S3: Design and manufacture a matching rigid mold 2 with embossing and debossing surfaces according to the shape and size of the embossing and debossing thin-walled disc part, and install the manufactured rigid mold 2 with embossing and debossing surfaces on the rubber bladder forming equipment for debugging.

[0041] Step S4: Place the circular blank 1 with circumferentially uniformly distributed arc-shaped notches on the rigid mold 2 with embossing and debossing surfaces for positioning.

[0042] Step S5: Place the circular rubber pad 3 on the circular blank 1 with circumferentially uniformly distributed arc-shaped notches. The radius B of the circular rubber pad 3 is greater than the radius R of the circular blank 1, so that the circular rubber pad 3 completely covers the circular blank 1.

[0043] Step S6: At the beginning of forming, the rigid mold 2 with embossing and debossing surfaces below remains stationary, the rubber bladder chamber above is gradually pressurized, and the middle circular rubber pad 3 causes the circular blank 1 with circumferentially uniformly distributed arc-shaped notches to deform under the pressure of the rubber bladder chamber and gradually fit the rigid mold 2 with embossing and debossing surfaces below.

[0044] Step S7: After the pressure P of the rubber bladder chamber reaches the set value, relieve the pressure and take out the part, and this forming is completed.

[0045] Preferably, the radius R of the circular blank is 330 mm, the depth h of the arc-shaped notch is 30 mm, the radius p of the arc-shaped notch is 40 mm, the quantity n of the arc-shaped notches is 12 and they are uniformly distributed along the circumferential direction on the outer edge of the circular blank, the radius B of the circular rubber pad is 400 mm, and the set value of the pressure P of the rubber bladder chamber is 20 Mpa.

[0046] The above has introduced the product provided by the present invention in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the invention, several improvements and modifications can still be made to the invention, and these improvements and modifications also fall within the protection scope of the claims of the invention.

Claims

1. A method for controlling the wrinkling at the outer edge during the embossing of a thin-walled concave-convex disc rubber bladder, applicable to the processing of parts by a rubber bladder forming device, characterized in that, The control method includes: Step S1: Calculate the size of the circular blank used for forming according to the shape and size of the designed concave-convex thin-walled disc part, add process allowance to the outer edge of the blank, and cut circumferentially evenly distributed arc-shaped notches on the process allowance at the outer edge of the circular blank. The arc-shaped notches are used to reduce the circumferential compressive stress at the outer edge of the blank during the rubber bladder forming process. Step S2: Manufacture a rigid mold with a concave-convex surface according to the shape and size of the concave-convex thin-walled disc part, and install the rigid mold on the processing platform of the rubber bladder forming equipment for debugging. Step S3: Lay the circular blank on the rigid mold and perform positioning, alignment, and fixation. Step S4: Select a circular rubber pad and lay it on the circular blank. The circular rubber pad is used to transfer the pressure of the rubber bladder liquid chamber and protect the arc-shaped notches. Step S5: Start the rubber bladder forming equipment. The rubber bladder liquid chamber of the rubber bladder forming equipment gradually increases the pressure. Under the action of the pressure of the rubber bladder liquid chamber, the circular blank deforms and gradually fits the concave-convex surface on the lower rigid mold. Step S6: After the pressure P of the rubber bladder liquid chamber reaches the set value, relieve the pressure and take out the part.

2. The control method according to claim 1, wherein The cutting of the circumferentially evenly distributed arc-shaped notches at the outer edge of the blank in S1 includes: Cutting circumferentially evenly distributed arc-shaped notches on the outer edge of the process allowance. Among them, the depth h of the arc-shaped notch is 0.05-0.15 times the radius R of the circular blank, the radius y of the arc-shaped notch is 1-2 times the depth h of the arc-shaped notch, and the number n of the arc-shaped notches is 10-20, and they are evenly distributed circumferentially along the outer edge of the process allowance.

3. The control method according to claim 1, characterized in that, The concave-convex surfaces on the rigid mold in S2 are arranged in mirror symmetry.

4. The control method according to claim 3, characterized in that The thickness or height of the concave-convex surface near the center of the rigid mold is greater than the thickness or height of the concave-convex surface far from the center of the rigid mold.

5. The control method according to claim 1, wherein The radius B of the circular rubber pad in S4 is greater than the radius R of the circular blank and can cover the circular blank and the process allowance.

6. The control method according to claim 1, wherein The pressure P of the rubber bladder liquid chamber in S6 is set to 20 Mpa.

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