Process method for two-pass pressing of concave-convex thin-wall disc rubber bag

Abstract

The concave-convex thin-wall disc rubber bag two-pass press forming process method is suitable for machining parts through rubber bag forming equipment and comprises the steps that a round plate, a die with a concave-convex molded surface and an annular steel die are machined, and the rubber bag forming equipment conducts first-pass rubber bag press forming on the round plate to form preformed parts; the pre-formed part is subjected to annealing process treatment so as to eliminate residual stress generated by first-pass pressing, and a round hole is cut in the central area of the pre-formed part after annealing; and the cut preformed part is subjected to second-pass rubber bag pressing, the resistance of the preformed part flowing into the concave cavity in the second-pass pressing process can be reduced through the round holes, part cutting is conducted after second-pass pressing to form the final part, and the machining efficiency is improved through the technology.

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 process method for rubber bladder two-pass forming of concave-convex thin-walled discs. Background Art

[0002] The aerospace field contains a large number of sheet metal parts. Concave-convex thin-walled discs are a typical type of component among them. Due to the complex concave-convex surface features of such components, traditional steel die stamping forming methods require multiple sets of dies to be formed in multiple times, resulting in problems such as many processing procedures and long production cycles. The rubber bladder forming process is a soft die forming method that uses the pressure of the rubber bladder liquid chamber to provide the active forming force, and the rubber pad as the force transmission medium, so that the metal sheet gradually fits the rigid die under the action of the pressure of the rubber bladder liquid chamber, thereby obtaining the shape of the part.

[0003] Due to the large depth of the concave cavity of the concave-convex thin-walled disc parts, excessive thinning or even cracking defects are extremely likely to occur on the side walls of the concave-convex surface during the rubber bladder forming process. And because the width of the bottom of the concave cavity of the part is small and there are small round corner features, while the thickness of the rubber pad is large, it is difficult for the sheet metal to fit the bottom of the concave cavity of the die under the action of the rubber pad. The traditional methods are as follows:

[0004] Publication No. (CN114247810B) discloses a forming die and a forming method for rubber bladder forming of an annular reverse bent part. Aiming at the problem that wrinkling defects are likely to occur during the rubber bladder forming process of the part's reverse bent structure, a two-pass forming method is proposed. In the first pass forming, a steel die is used to press the outer edge of the sheet metal to suppress wrinkling defects during the outer side bending process. In the second pass forming, the steel die moves to form the inner side bend and correct the joint surface of the inner and outer side bends. However, the two-pass forming method is to separately form the outer side bend and the inner side bend of the part to avoid wrinkling defects when forming the two bend structures of the part at one time. For the rubber bladder forming process of the concave-convex thin-walled disc, its main problems are excessive thinning and cracking of the material deformation during the forming process caused by the large depth of the concave cavity of the part, and the difficulty of the sheet metal fitting the bottom of the concave cavity of the die due to the narrow bottom of the concave cavity of the part. Moreover, this method adds two additional sets of dies in the first and second pass formings, greatly increasing the tooling manufacturing cost and installation time.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a process method for rubber bladder two-pass forming of concave-convex thin-walled discs, to solve the problems of excessive thinning and cracking and non-fitting die defects that are likely to occur during the part forming process, so as to achieve high-efficiency and high-quality forming manufacturing of such parts. There are many technical beneficial effects of the technical solution of this case, as introduced below:

[0007] A process method for two-pass rubber bladder forming of a concave-convex thin-walled disc rubber bladder, applicable to the processing of parts by a rubber bladder forming device. The process method includes:

[0008] S1: Process a circular blank, a mold with a concave-convex surface, and an annular steel mold. Among them, arc-shaped notches evenly distributed circumferentially are cut on the outer edge of the circular blank. The annular steel mold can be placed inside the concave-convex surface of the mold, and the mold is installed on the workbench of the rubber bladder forming device;

[0009] S2: The rubber bladder forming device performs the first-pass rubber bladder forming on the circular blank. Among them,

[0010] Place the circular blank on the mold and position it. A rubber pad is laid above the circular blank;

[0011] Increase the pressure of the rubber bladder chamber of the rubber bladder forming device. Under the action of the pressure of the rubber bladder chamber, the rubber pad deforms the circular blank, gradually fitting the concave-convex surface of the mold. After the pressure of the rubber bladder chamber reaches the set value P1, relieve the pressure and retrieve the part to form a preformed part;

[0012] S3: Perform an annealing process on the preformed part to eliminate the residual stress generated by the first-pass forming and reduce the cold work hardening of the part. After annealing, cut a round hole in the central area of the preformed part;

[0013] S4: Perform the second-pass rubber bladder forming on the preformed part after cutting. The round hole can reduce the resistance of the preformed part flowing into the concave cavity during the second-pass forming. After the second-pass forming, perform partial cutting to form the final part.

[0014] Compared with the prior art, the technical solution provided by the present invention includes the following beneficial effects:

[0015] The method of the present invention can effectively avoid the defects of excessive thinning and cracking and non-conforming mold fitting of the part during the forming process by two-pass rubber bladder forming, annealing the preformed part of the first pass, machining a round hole, and adding an annular steel mold adapted to the concave cavity of the target part during the second-pass forming, and realize the efficient and high-quality forming manufacturing of this type of part. Description of the Drawings

[0016] 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 the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1Structural schematic diagrams of parts, molds, and annular steel membranes for the process of the present invention;

[0018] Figure 2 Schematic diagram of the first press forming in the process of the present invention;

[0019] Figure 3 Schematic diagram of the second press forming in the process of the present invention, wherein

[0020] 1. Concave-convex thin-walled disc part; 2. Circular blank; 3. Mold; 4. Annular steel mold; 5. Preformed part; 6. Rubber pad. Specific implementation manners

[0021] The following illustrates the implementation manners of the present invention through specific specific examples. 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 a part of the embodiments of the present invention, rather than all the embodiments. The present invention can also be implemented or applied through other different specific implementation manners. 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. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0022] In addition, in the following description, specific details are provided for the purpose of thorough understanding of the examples. However, those skilled in the art will understand that the aspects can be practiced without these specific details. To make those skilled in the art better understand the solution of the present invention, the following further describes the present invention in detail in conjunction with the drawings and specific implementation manners. The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can 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 of" is two or more.

[0023] As Figures 1 to 3 shown, the process method of two-pass press forming of a concave-convex thin-walled disc rubber bladder is applicable to the processing of parts by a rubber bladder forming device. This process method includes

[0024] S1: Process a circular blank, a mold with concave-convex surfaces, and an annular steel mold. Among them, arc-shaped notches evenly distributed circumferentially are cut on the outer edge of the circular blank. The annular steel mold can be placed inside the concave-convex surface of the mold. The mold is installed on the workbench of the rubber bladder forming equipment. Preferably, the size of the circular blank for forming is calculated inversely according to the shape and size of the designed concave-convex thin-walled disc part. The inverse calculation is carried out, for example, by using simulation software. Process allowance is added to the outer edge of the blank, and arc-shaped notches evenly distributed circumferentially are cut on the outer edge of the process allowance. The arc-shaped notches are used to reduce the circumferential compressive stress at the outer edge of the blank during the rubber bladder pressing process. After overall forming, cutting is carried out according to actual requirements.

[0025] S2: The rubber bladder forming equipment performs the first-pass rubber bladder pressing on the circular blank. Among them,

[0026] Place the circular blank on the mold and position it. A rubber pad is laid above the circular blank;

[0027] Increase the pressure in the rubber bladder chamber of the rubber bladder forming equipment. 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-convex surface of the mold. After the pressure in the rubber bladder chamber reaches the set value P1, relieve the pressure and retrieve the part to form a preformed part.

[0028] S3: Perform an annealing process on the preformed part to eliminate the residual stress generated by the first-pass pressing and relieve the cold work hardening of the part. After annealing, a round hole is cut in the central area of the preformed part. Preferably, the diameter of the round hole is 0.5 - 0.8 times the diameter of the round hole at the top of the concave-convex thin-walled disc part, which can increase the bonding force.

[0029] For the preformed part after cutting, perform the second-pass rubber bladder pressing. The round hole can reduce the resistance of the preformed part flowing into the concave cavity during the second-pass pressing. After the second-pass pressing, perform partial cutting to form the final part. Among them, the second-pass rubber bladder pressing of the preformed part after cutting includes,

[0030] The second-pass rubber bladder pressing of the preformed part includes,

[0031] Place the preformed part with the cut round hole on the mold, place the annular steel mold on the preformed part, and lay a rubber pad above the annular steel mold;

[0032] Gradually increase the pressure in the rubber bladder chamber. Under the action of the pressure in the rubber bladder chamber, the rubber pad causes the annular steel mold to move downward. At the same time, the preformed part deforms under the action of the annular steel mold and gradually conforms to the concave cavity of the mold;

[0033] When the pressure in the rubber bladder chamber reaches the set value P2, hold the pressure for 0.5 - 2 minutes to make the preformed part completely conform to the mold under the action of the annular steel mold.

[0034] Furthermore, the lower surface profile of the annular steel mold coincides with the bottom profile of the concave cavity of the concave-convex thin-walled disc part, and the thickness of the annular steel mold is 0.4 - 0.6 times the depth of the concave cavity of the concave-convex thin-walled disc part.

[0035] In summary, this process method can not only effectively avoid the defects of excessive thinning and cracking of parts and non-conforming to the mold, but also has good versatility, simple mold structure, the advantages of convenient operation and low technical level requirements for process personnel, which is conducive to popularization and application in the field of rubber bladder forming manufacturing of sheet metal parts.

[0036] The embodiment provides a two-pass rubber bladder pressing process method for a concave-convex thin-walled disc. This method is pressed in two passes. After the first pass of pressing, the preformed part is annealed to eliminate residual stress and reduce cold work hardening, and a round hole is opened at the top of the preformed part to reduce the resistance of the material flowing into the concave cavity during the second pass of pressing. The two comprehensive measures avoid excessive thinning and cracking of the sheet metal during the pressing process. During the second pass of pressing, an annular steel mold adapted to the concave cavity of the target part is added above the preformed part, and the pressure is maintained for 0.5 - 2 minutes after the rubber bladder chamber pressure reaches the set value, so that the sheet metal completely fits the concave cavity of the concave-convex surface mold under the action of the annular steel mold.

[0037] Taking a certain type of part as an example for illustration, as follows:

[0038] Step S1: Design and manufacture the sheet metal and tools required for the two-pass rubber bladder pressing of the concave-convex thin-walled disc

[0039] As Figure 1 shown, according to the shape of the concave-convex thin-walled disc part 1, a circular sheet metal 2 with circumferentially uniformly distributed arc-shaped notches, a concave-convex surface mold 3 and an annular steel mold 4 are designed and manufactured;

[0040] The lower surface profile of the annular steel mold 4 is the same as the bottom profile of the concave cavity of the concave-convex thin-walled disc part 1, and the thickness of the annular steel mold 4 is 0.4 - 0.6 times the depth of the concave cavity of the concave-convex thin-walled disc part 1.

[0041] Step S2: Perform the first-pass rubber bladder pressing to obtain a preformed part 5. As Figure 2 shown, the concave-convex surface mold 3 is installed and fixed on the workbench of the rubber bladder forming equipment, then the circular sheet metal 2 is placed on the concave-convex surface mold 3 and positioned, and a rubber pad 6 is laid above the circular sheet metal 2; the rubber bladder chamber pressure is gradually increased, and the rubber pad 6 deforms the circular sheet metal 2 under the action of the rubber bladder chamber pressure and gradually fits the lower concave-convex surface mold 3; when the rubber bladder chamber pressure reaches the set value P1, the pressure is released to obtain the preformed part 5.

[0042] Step S3: Anneal the preformed part 5 and cut a round hole at its top. Anneal the preformed part 5 obtained by the first-pass rubber bladder forming to eliminate the residual stress generated by the first-pass forming and relieve the cold work hardening of the part. Then, cut a round hole at the top of the preformed part 5. The diameter of the round hole cut at the top of the preformed part 5 is 0.5 - 0.8 times the diameter of the round hole at the top of the concave-convex thin-wall disc part 1.

[0043] Step S4: Perform the second-pass rubber bladder forming and cut to obtain the concave-convex thin-wall disc part. As Figure 3 shown, place the preformed part 5 that has been annealed and has a round hole cut at its top on the concave-convex surface die 3. Then, place the annular steel die 4 on the preformed part 5, and lay a rubber pad 6 above the annular steel die 4; gradually increase the pressure in the rubber bladder chamber. Under the action of the pressure in the rubber bladder chamber, the rubber pad 6 makes the annular steel die 4 move downward, and at the same time makes the preformed part 5 deform under the action of the annular steel die 4 and gradually fit the concave cavity of the concave-convex surface die 3; when the pressure in the rubber bladder chamber reaches the set value P2, hold the pressure for 0.5 - 2 minutes to make the preformed part 5 completely fit the concave-convex surface die 3 under the action of the annular steel die 4; after the pressure holding ends, relieve the pressure in the rubber bladder chamber and take out the formed part, and then cut off the excess parts of the round hole and the outer edge notch at the top of the part to finally obtain the concave-convex thin-wall disc part 1.

[0044] In one embodiment, the diameter of the round hole at the top of the concave-convex thin-wall disc part 1 is 80 mm, the diameter of the round hole cut at the top of the preformed part 5 is 60 mm, the depth of the concave cavity of the concave-convex thin-wall disc part 1 is 61 mm, the thickness of the annular steel die 4 is 30 mm, the set value P1 of the pressure in the rubber bladder chamber in the first-pass rubber bladder forming is 20 MPa, the set value P2 of the pressure in the rubber bladder chamber in the second-pass rubber bladder forming is 35 MPa, and the pressure is held for 1 minute.

[0045] 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 in this technical field, without departing from the principle of the invention, several improvements and modifications can 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 two-step forming process for a concave-convex thin-walled disc rubber bag, suitable for processing parts by rubber bag forming equipment, characterized in that: The process comprises: S1: Processing a circular plate, a mold with a concave-convex surface and an annular steel mold, wherein the outer edge of the circular plate is cut with arc-shaped notches evenly distributed in the circumferential direction, the annular steel mold can be placed in the concave-convex surface of the mold, and the mold is installed on a workbench of a rubber bag forming device; S2: The rubber bag forming device performs the first rubber bag pressing on the circular sheet, wherein: The circular sheet is placed on a mold and positioned, and a rubber pad is laid on top of the circular sheet; The pressure of the rubber bag liquid chamber of the rubber bag forming device is increased, and the rubber pad deforms the circular sheet under the action of the pressure of the rubber bag liquid chamber, and gradually fits the concave and convex surface of the mold. When the pressure of the rubber bag liquid chamber reaches the set value P1, the pressure is released and the part is retrieved to form a preformed part; S3: performing an annealing process on the preformed part to eliminate the residual stress generated by the first press forming and reduce the cold work hardening of the part, and cutting a circular hole in the central area of ​​the preformed part after annealing; S4: The preformed part after cutting is subjected to a second rubber bag pressing process, wherein the circular hole can reduce the resistance of the preformed part to flow into the concave cavity during the second pressing process, and a partial cutting is performed after the second pressing process to form a final part.

2. The process according to claim 1, characterized in that: The arc notches uniformly distributed in the circumferential direction cut on the outer edge of the sheet in S1 include: The dimensions of the circular sheet material are calculated inversely according to the shape and dimensions of the designed concave-convex thin-walled disc part, and a process allowance is added to the outer edge of the sheet material, and arc notches uniformly distributed in the circumferential direction are cut on the outer edge of the process allowance. The arc notches are used to reduce the circumferential compressive stress on the outer edge of the sheet material during the rubber bag pressing process.

3. The process according to claim 2, characterized in that: The lower surface contour of the annular steel mold coincides with the bottom contour of the concave cavity of the concave-convex thin-walled disc part, and the thickness of the annular steel mold is 0.4-0.6 times the depth of the concave cavity of the concave-convex thin-walled disc part.

4. The process according to claim 3, characterized in that: The diameter of the circular hole in S3 is 0.5-0.8 times the diameter of the circular hole at the top of the concave-convex thin-walled disc part.

5. The process according to claim 3, characterized in that: The second rubber bag forming of the preformed part after cutting in S4 includes: Placing the preformed part with the circular hole cut out on the mold, placing the annular steel mold on the preformed part, and laying a rubber pad on the annular steel mold; The pressure in the rubber sac fluid chamber is gradually increased, and the rubber pad moves the annular steel mold downward under the action of the pressure in the rubber sac fluid chamber. At the same time, the preformed part is deformed under the action of the annular steel mold and gradually fits the concave cavity of the mold.

6. The process according to claim 3, characterized in that: When the pressure of the rubber bag liquid chamber reaches the set value P2, the pressure is maintained for 0.5-2 minutes, so that the preformed part is completely fitted into the mold under the action of the annular steel mold.

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