Forming die and forming method for aviation sheet metal heat shield part

Abstract

The invention relates to an aviation sheet metal heat shield part forming die and a forming method, and belongs to the technical field of aviation manufacturing sheet metal forming. The invention discloses an aviation sheet metal heat shield part forming die and a forming method. The forming die comprises a drawing die and a hydraulic die. The drawing die is used for forming a semi-finished product part and comprises a female die, a male die, a blank holder, an ejector block, an upper die plate and a lower die plate, the female die and the ejector block are respectively connected with the upper die plate, the male die and the blank holder are respectively connected with the lower die plate, a part combination blank is arranged between the male die and the ejector block, and the blank holder tightly presses the part combination blank. The hydraulic die is used for forming a final part finished product and comprises a hydraulic female die, a hydraulic male die and a cover plate, during hydraulic forming, the cover plate presses the web face of a semi-finished part, the semi-finished part is completely attached to the hydraulic female die and the hydraulic male die, and the final part finished product is obtained after trimming. The invention has the following advantages: the production efficiency of parts is improved; the qualified rate of parts is high; and the production efficiency is obviously improved.

Description

A forming mold and forming method for aerospace sheet metal heat shield parts Technical Field

[0001] This invention relates to a forming mold and forming method for aerospace sheet metal heat shield parts, belonging to the field of aerospace manufacturing sheet metal forming technology. Background Technology

[0002] Heat shields are important components at the exhaust heat end of aircraft or missiles, used to isolate high temperatures and protect other parts of the cabin. The surface structure of this component is relatively complex, usually composed of multiple curved surfaces, with many free-form surfaces, and exhibiting an asymmetrical structure. At the same time, the internal depth of the component is inconsistent, and the deformation process of the component is extremely complex.

[0003] Currently, the forming process of this part adopts the process method of "drop forming + manual correction". The forming device is a drop hammer mold and a hand-made mold. The part is drop formed on the drop hammer mold, mainly for forming the outline of the part. Then, it is manually corrected on the hand-made mold to ensure the final mold and shape accuracy of the part. However, the following defects are prone to occur in the drop forming process: (1) The pass rate is low and the surface quality of the part is poor. Usually, the structure of the heat insulation cover part is inconsistent in depth and the shape of the part is irregular. The uneven force during the drop forming process causes wrinkles of different sizes to appear in the part, and even cracks in some areas; (2) The drop hammer mold is made of lead-zinc mold, which is expensive. If the production volume of parts is large, a large number of parts will be easily worn in contact with the drop hammer mold during the continuous drop forming process. In addition to seriously affecting the surface quality and forming accuracy of the parts after forming, the subsequent drop hammer maintenance cost is high. After the parts are formed by drop forming, there are many wrinkled areas. The manual wrinkle removal work is labor-intensive, and there are some wrinkles in some areas that cannot be completely eliminated, which affects the appearance and surface quality of the parts and the production efficiency is low. (3) The time cycle for manual correction after the drop forming of a single part is long, which seriously restricts the production and delivery of parts.

[0004] Therefore, although the subsequent use of "bed plate drop forming process + self-made template for manual correction" to optimize the part forming can improve the material flow to a certain extent and reduce the wrinkling area compared with the previous stage, the deformation of the heat insulation cover parts is extremely complex and the stress at each position is different. The subsequent manual hammering correction operation at different positions of the parts is still required, which will affect the fatigue strength and other properties of the material, and the time cycle is long. Summary of the Invention

[0005] The purpose of this invention is to provide a forming mold for aerospace sheet metal heat shield parts, which can improve the pass rate and production efficiency of heat shield sheet metal parts, ensure that the parts fit the mold after forming, eliminate wrinkles after forming and reduce costs; at the same time, reduce the amount of manual correction and reduce the labor intensity of operators.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a forming mold for aerospace sheet metal heat insulation cover parts, the forming mold including a drawing mold and a hydraulic mold; the drawing mold is used for forming semi-finished parts, and includes a die, a punch, a pressure ring, an ejector block, an upper template and a lower template, the die and the ejector block are respectively connected to the upper template, the punch and the pressure ring are respectively connected to the lower template, the part assembly blank is placed between the punch and the ejector block, and the pressure ring presses the part assembly blank; the hydraulic mold is used for forming the final finished part, and includes a hydraulic die, a hydraulic punch and a cover plate, during hydraulic forming, the cover plate presses the web surface of the semi-finished part, the semi-finished part is completely fitted to the hydraulic die and the hydraulic punch, and after trimming, the final finished part is obtained.

[0007] Preferably, the component assembly includes component raw materials and scrap materials; the number of component raw materials is two, the two have the same structure and are arranged opposite each other on both sides of the scrap materials.

[0008] Preferably, the length of the scrap material accounts for 1 / 4 to 1 / 3 of the maximum external length of the part's raw material.

[0009] Preferably, pin positioning holes are provided in the middle area of ​​the part assembly blank, at the corresponding positions of the punch and the ejector block.

[0010] Preferably, the pressure ring adopts an integral design, and its outer dimensions cover the assembly of the parts and the raw material.

[0011] Preferably, the punch, die, and pressure ring are made of Cr12MoV material.

[0012] Preferably, the hydraulic mold adopts a contour positioning method.

[0013] Preferably, the hydraulic die is used to process the dotted lines on the edge of the part using a CNC machine tool.

[0014] Another objective of this invention is to provide a forming method for aerospace sheet metal heat shield parts, which uses the forming mold as described above and includes the following steps: (1) According to the product digital model, the maximum outline of multiple unclosed free-form surfaces of the combined parts is segmented and unfolded using relevant software; the data after each segment is unfolded is closed and linearly connected to obtain complete unfolded data and the final blanking size of the part is obtained; (2) According to the unfolded dataset, a "unfolded blank template" is made, and after the blank of the part is cut into blanks using the combined blank method, a deep drawing die is installed, the combined blank of the part is placed on the deep drawing die punch, and the combined blank of the part is pressed with a pressure ring; (3) The machine tool is started, and after the outline of the combined blank of the part is completely fitted with the mold, a semi-finished part is finally obtained; (4) The semi-finished part is placed on the hydraulic die, the cover plate is pressed against the web surface of the semi-finished part, and hydraulic forming is performed. After the hydraulic punch and hydraulic die are completely closed, the semi-finished part is completely fitted with the hydraulic die and hydraulic punch, the part is directly taken out, and the part outline is directly trimmed along the initial imprint of the hydraulic forming to obtain the final finished part.

[0015] Compared with the prior art, the present invention has the following advantages: 1. By adopting combined blank forming, the previous single-part forming is changed. On the one hand, the material forming fluidity is improved, ensuring the forming quality of the parts; on the other hand, the dual-part combined forming improves the production efficiency of the parts and ensures timely delivery of the parts; 2. The surface quality of the formed parts is good, the pass rate is high, and no wrinkling or cracking defects are generated; 3. The production efficiency is significantly improved, and the amount of manual correction by workers is significantly reduced. After correction by using hydraulic molds, all parts are molded, and the parts do not need to be manually corrected by hand molds; 4. It can provide important guidance for the subsequent forming of heat insulation cover parts and mold design. Attached Figure Description

[0016] Figure 1 is a schematic diagram of a typical heat insulation cover skin part structure in an embodiment of the present invention; Figure 2 is a schematic diagram of the part assembly blank structure in an embodiment of the present invention; Figure 3 is a schematic diagram comparing the segmented unfolded blank template and the outline (unfolded) template structure in an embodiment of the present invention; Figure 4 is a schematic diagram of the deep drawing die assembly structure in an embodiment of the present invention; Figure 5 is a schematic diagram of the punch and pressure ring assembly structure in an embodiment of the present invention; Figure 6 is a schematic diagram of the pressure ring structure in an embodiment of the present invention; Figure 7 is a schematic diagram of the top block structure in an embodiment of the present invention; Figure 8 is a schematic diagram of the punch structure in an embodiment of the present invention; Figure 9 is a schematic diagram of the die decoupling strand in an embodiment of the present invention; Figure 10 is a schematic diagram of the hydraulic punch and cover plate structure in an embodiment of the present invention; Figure 11 is a schematic diagram of the hydraulic punch structure in an embodiment of the present invention; Figure 12 is a schematic diagram of the cover plate structure in an embodiment of the present invention; Figure 13 is a schematic diagram of the hydraulic die structure in an embodiment of the present invention; In Figure 2, 1 (1), 1 (2) - part blank; 2 - scrap material; 3 - pin positioning hole; In Figure 3, 4 - unfolded blank template; 5 - outline (unfolded) template; Schematic diagrams of different areas of parts a1, a2, b1, b2, c1, c2, e1, e2, and d; In Figure 4, 6-top block; 7-upper template; 8-die; 9-pressure ring; 10-lower template; 11-part assembly blank; 12-punch; In Figure 5, 13-pin hole; In Figure 7, 14-pin hole; In Figure 8, 15-pin hole; In Figure 10, 16-cover plate; 17-hydraulic punch; In Figure 13, 18-hydraulic die. Detailed Implementation

[0017] It should be noted that the terms "upper," "lower," "left," "right," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0018] The invention will be further described in detail below with reference to Figures 1-13: A forming mold and forming method for aerospace sheet metal heat insulation cover parts. The forming mold design uses a "deep drawing mold + hydraulic mold" to replace the previous "drop hammer mold + hand-made mold" device. The deep drawing mold is used for precise forming of the part's shape, and the hydraulic mold is used for part correction. The forming method is "deep drawing + hydraulic forming". Deep drawing is mainly used for precise forming of the part's shape, and hydraulic forming is used for part correction. The part can be formed in only one deep drawing process to ensure that the part's shape fits the mold, further achieving the requirement of precise forming. After deep drawing, the part is corrected by hydraulic forming, which avoids the quality difference in the manual correction process and greatly improves the forming efficiency. At the same time, the part is formed by combining blanks. By designing to use unfolded blank templates for blank cutting and then combining them, it is beneficial to material forming and provides forming quality and forming efficiency.

[0019] As a preferred embodiment of this example, 1. Determining the size of the part blank: As shown in Figures 1-3, the part blank forming and blanking method adopts a combined unfolding blank template method, changing the previous method of drawing a single part in a drawing die, that is, forming two parts simultaneously. As shown in Figure 3, unfolding blank template 4 and outline (unfolding) template 5, where a1, a2, b1, b2, c1, c2, e1, e2 and d are schematic diagrams of unfolding different areas of the part. On the one hand, it can avoid material waste and also facilitate the better forming of the part material in the mold, improve the forming quality and forming efficiency; on the other hand, it can make the excess scrap of the part flow to the middle area, ensure that it can be further attached to the mold during the deep drawing process, and reduce the amount of wrinkling on the edge of the part; the design of the scrap area in the middle area of ​​the part assembly blank: as shown in Figure 2, the part assembly blank includes part blank, scrap 2 and pin positioning hole 3; there are two part blanks, namely part blank 1 (1) and part blank 1 (2), which have the same structure and are set on both sides of scrap 2. That is to say, scrap 2 is located in the middle area of ​​the two part blanks, and the pin positioning hole 3 is opened in its center position; by forming the assembly blank, in order to improve the forming fluidity of the part blank in the deep drawing mold, the design of the middle scrap corner area can further ensure the deep drawing effect. The length of the middle scrap is about 1 / 4-1 / 3 of the maximum external length of the part, that is, L1=(1 / 4-1 / 3)L.

[0020] 2. Part Drawing Die Design: As shown in Figure 4-9, the drawing die mainly consists of a die cavity 8, a punch 12, a blank holder 9, an ejector block 6, an upper die plate 7, a lower die plate 10, and several bolts or screws. The drawing die structure design preferentially adopts a single-action drawing die design, where the punch 12 and blank holder 9 are connected to the lower die plate 10 using screws and bolts, while the die cavity 8 and ejector block 6 are connected to the upper die plate 7 using screws and bolts. Besides being low-cost and easy to maintain, this structure, guided by the punch during the forming process of the heat shield part, ensures that the part's contour perfectly matches the die cavity in a single drawing process, further achieving the requirement of precise part forming.

[0021] Design and selection of blank holder 9: Based on the analysis of the part forming process, a rigid blank holder is preferred, and a combined blank holder structure is adopted. The external dimensions must ensure that the combined blank holder 11 is covered. To avoid wrinkling at the edge of the part due to different pressures from the blank holder during the deep drawing process caused by the different operating forces of the workers during the bolt connection between the blank holder 9 and the punch 12, a combined structure of the deep drawing punch and blank holder is designed. This eliminates the subjectivity of human operation and greatly improves production efficiency. The blank holder 9 adopts an integral design, that is, two blanks plus the scrap material are placed on the die 8 and move downward through the combined structure of the punch 12 and the blank holder 9. There is no need to design a draw bead structure, which simplifies the die structure and minimizes the wrinkling problem of the part. It can better ensure the material flow on the die and improve the deep drawing accuracy.

[0022] Pin hole position design: To further ensure the accurate forming of the part during the forming process and reduce the amount of wrinkling after deep drawing, a single pin hole is designed for positioning only in the middle area of ​​the part assembly blank 11, the punch, and the ejector block. In this embodiment, the pin positioning hole 3 (located in the center of the part assembly blank), pin hole 13 (located in the center of the punch and pressure ring assembly structure), pin hole 14 (located in the center of the ejector block), and pin hole 15 (located in the center of the punch) are positioned opposite each other and aligned at the same center. This ensures that the material of the part blank flows to the scrap area during the forming process, while other forming areas are in contact with the drawing die, resulting in less wrinkling in the part forming area and facilitating part forming.

[0023] The concave die 8 and the convex die 12 adopt a combined structural design, and the shape design is based on the shape structure design of the combined parts and the raw material.

[0024] Material selection and design: After the part forming blank adopts a combined blank structure, the part size is larger, which puts higher requirements on the use of the mold. Therefore, in order to ensure the stability of the part forming process, further reduce wrinkling and improve the service life of the mold, the punch, die and blank holder of the deep drawing die are preferably made of Cr12MoV, which has higher hardness and wear resistance than common MoCr cast iron. Other structures: The top block, upper template and lower template structure do not participate in the direct contact forming of the part, and can be made of common 45# steel.

[0025] 3. Hydraulic mold design for parts: As shown in Figure 10-13, the hydraulic forming mold for parts consists only of a hydraulic die 18, a hydraulic punch 17, and a cover plate 16; a. The hydraulic die with a cover plate is designed based on the product model of the part. Its main function is to ensure the manual shaping during the deep drawing process of the part, directly replacing the hand-made mold; b. By machining the dotted lines on the edge of the part using a CNC machine tool, the initial imprint of the part can be ensured after the part blank is formed. After hydraulic forming, the part shape only needs to be trimmed directly along the initial imprint of the hydraulic forming, avoiding manual trimming of the part shape and greatly improving the surface quality and production efficiency of the part.

[0026] c. The designed hydraulic forming mold uses contour positioning, eliminating the need for secondary positioning with pin holes and avoiding secondary forming of the part. This method increases the fatigue strength of the part and improves material properties. Simultaneously, contour positioning improves the forming accuracy of the part and further reduces the amount of subsequent manual correction.

[0027] Forming method of aviation sheet metal heat shield parts: (1) According to the product model, the maximum outline of multiple unclosed free-form surfaces of the combined parts is segmented and unfolded using relevant software. The data after each segment is unfolded is closed and linearly connected to obtain complete unfolded data and the final blanking size of the parts is obtained; (2) According to the unfolded dataset, a "unfolded blank template" 4 is made. After the blank of the part is cut using the part combination blank 11, the top block 6, upper template 7, die 8, pressure ring 9, lower template 10 and punch 12 in the deep drawing die are installed. The part combination blank 11 is placed in the drawing die. After the deep die punch 12, the blank material 11 of the part assembly is pressed with the pressure ring 9; (3) Start the machine tool, and after the outline of the blank material 11 of the part assembly is completely fitted with the mold, the semi-finished part is finally obtained; (4) Place the semi-finished part on the hydraulic die 18, press the cover plate 16 to the web surface of the semi-finished part, and perform hydraulic forming. After the hydraulic punch 17 and the hydraulic die 18 are completely closed, the semi-finished part is completely fitted with the hydraulic die 18 and the hydraulic punch 17. The part is directly taken out, and the part shape is directly trimmed along the initial imprint of hydraulic forming to obtain the final finished part.

Claims

1. A forming mold for an aerospace sheet metal heat shield part, characterized in that: The forming mold includes a drawing die and a hydraulic die. The drawing die is used for forming semi-finished parts and includes a die cavity, a punch, a blank holder, an ejector block, an upper template, and a lower template. The die cavity and the ejector block are connected to the upper template, and the punch and the blank holder are connected to the lower template. The part assembly blank is placed between the punch and the ejector block, and the blank holder presses the part assembly blank. The hydraulic die is used for forming the final finished part and includes a hydraulic die cavity, a hydraulic punch, and a cover plate. During hydraulic forming, the cover plate presses the web surface of the semi-finished part, and the semi-finished part is completely fitted to the hydraulic die cavity and the hydraulic punch. After trimming, the final finished part is obtained.

2. The forming mold for aerospace sheet metal heat shield parts according to claim 1, characterized in that: The component assembly includes component raw materials and scrap materials; there are two component raw materials, which have the same structure and are positioned opposite each other on both sides of the scrap materials.

3. The forming mold for aerospace sheet metal heat shield parts according to claim 2, characterized in that: The length of the scrap material accounts for 1 / 4 to 1 / 3 of the maximum outer length of the part's raw material.

4. The forming mold for aerospace sheet metal heat shield parts according to claim 1, characterized in that: Pin positioning holes are provided in the middle area of ​​the part assembly blank, at the corresponding positions of the punch and the ejector block.

5. The forming mold for aerospace sheet metal heat shield parts according to claim 1, characterized in that: The pressure ring adopts an integral design, and its outer dimensions cover the assembly of the parts and the raw material.

6. The forming mold for aerospace sheet metal heat shield parts according to claim 1, characterized in that: The punch, die, and blank holder are made of Cr12MoV material.

7. The forming mold for aerospace sheet metal heat shield parts according to claim 1, characterized in that: The hydraulic mold uses contour positioning.

8. The forming mold for aerospace sheet metal heat shield parts according to claim 1, characterized in that: Hydraulic dies are used to process dotted lines on the edges of parts using CNC machine tools.

9. A method for forming an aerospace sheet metal heat shield part, characterized in that: Using the forming mold as described in any one of claims 1-7, the following steps are included: (1) According to the product digital model, the maximum outer contour of multiple unclosed free-form surfaces of the combined parts is segmented and unfolded using relevant software; the data after each segment is unfolded is closed and linearly connected to obtain complete unfolded data and the final blanking size of the part is obtained; (2) Make a "developed blank template" based on the unfolded dataset. After the blank of the part is cut into the combined blank, install the drawing die, place the combined blank of the part on the drawing die punch, and press the combined blank of the part with the pressure ring; (3) Start the machine tool. After the outline of the combined blank of the part is completely fitted with the mold, the semi-finished part is finally obtained; (4) Place the semi-finished part on the hydraulic die, press the cover plate on the web surface of the semi-finished part, and perform hydraulic forming. After the hydraulic punch and hydraulic die are completely closed, the semi-finished part is completely fitted with the hydraulic die and hydraulic punch. Take out the part directly and trim the part shape directly along the initial imprint of hydraulic forming to obtain the final finished part.

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