Integral lip thermoforming process

Abstract

A one-piece thermoforming process for lip edges reduces the risk of thinning and cracking in the finished product. The process includes providing a mold, comprising a punch and a die, the punch being designed according to the inner surface shape of the lip edge, and the die being designed according to the outer surface of the lip edge; selecting an annular blank; heating the blank to 20°C-40°C below the solution state and holding it at that temperature; transferring the blank to the die, where the punch pre-stamps the blank until the pre-stamping position is reached, forming a shallow cavity structure for the lip edge, i.e., the initial blank; removing the initial blank, heating it to the solution state and holding it at that temperature; transferring the initial blank to the die, where the punch performs a second stamping operation until the pre-stamping position is reached, forming a deep cavity structure for the lip edge, i.e., the final blank; and machining the final blank to the finished product dimensions.

Description

Technical Field

[0001] This invention relates to a forming and manufacturing process for integral lips, and more particularly to a thermoforming process for integral lips. Background Technology

[0002] The air intake lip is a crucial component of the aircraft engine nacelle air intake, characterized by high curvature, large size (maximum outer diameter exceeding 2000mm, cross-sectional depth exceeding 250mm), and high drawing ratio. Its cross-section is typically C-shaped or V-shaped, located at the very front of the engine, serving functions such as airflow rectification, anti-icing, protection against electric shock, and protection against bird strikes. These structural characteristics necessitate high requirements for thickness, surface profile, and surface roughness. Currently, the manufacturing process for large-sized air intake lips often involves segmented forming followed by riveting or welding. Segmented forming presents the following problems: 1) Riveting or welding reduces the dimensional accuracy and mechanical properties of the joint, while also increasing the weight of the part; 2) Uneven stress distribution during forming leads to severe springback and wrinkling after forming, deviating from the required profile accuracy and ultimately affecting the aerodynamic performance of the part.

[0003] The quality of integrally formed lips is significantly higher than that of segmented forming. Currently, a process for preparing integral lips using liquid-filled deep drawing has also emerged. This process is a cold process, and the material has low plasticity during forming, making it prone to thinning and cracking. At the same time, in order to ensure hydraulic adjustment during the forming process, the hydraulic equipment is generally designed to be complex, with high equipment costs, which is not conducive to mass production. Summary of the Invention

[0004] The purpose of this invention is to provide an integral lip thermoforming process, which makes the finished product less prone to thinning and cracking.

[0005] According to an embodiment of the present invention, the integral lip thermoforming process includes the following steps:

[0006] A mold is provided, the mold including a punch and a die, the punch being set according to the inner surface shape of the lip, and the die being set according to the outer surface of the lip;

[0007] Select ring-shaped billet;

[0008] Heat the billet to 20℃-40℃ below the solution state and hold it at that temperature;

[0009] The blank is transferred to the die cavity, and the punch pre-punches the blank. Once the pre-punching position is reached, the punching stops, forming a shallow cavity structure with a lip, which is the initial blank.

[0010] Remove the initial preform, heat it to a solution state and hold it at that temperature;

[0011] The initial blank is transferred to the die, and the punch performs a second stamping on the initial blank. After reaching the pre-stamping position, the stamping stops, forming a deep cavity structure with a lip, which is the final blank.

[0012] Process the final blank to the finished product size.

[0013] In one or more embodiments, during the pre-stamping and secondary stamping processes, the die and punch do not require mold heating, and a cooling medium is circulated at the base where the mold is installed, so that the blank achieves a quenching effect during the stamping process.

[0014] In one or more embodiments, the blank is made of aluminum alloy.

[0015] In one or more embodiments, the blank is a 2219 aluminum alloy sheet or a 2618 aluminum alloy sheet.

[0016] In one or more embodiments, the pre-stamping amount is characterized in that the pre-stamping amount does not exceed 1 / 3 of the total depth of the lip.

[0017] In one or more embodiments, the outer ring diameter of the blank is no more than 3200 mm, the inner ring diameter is no more than 310 mm, and the thickness is no less than 2 mm.

[0018] In one or more embodiments, the time for each transfer of the blank does not exceed 10 seconds, and the time for each stamping does not exceed 5 seconds.

[0019] In one or more embodiments, the lip is the air intake lip of an aircraft engine nacelle air intake.

[0020] The aforementioned process is for lip parts with a large cross-sectional depth. It adopts a "two-step stamping" process, with a solution treatment added between the two stamping steps. This can homogenize the microstructure, accelerate stress distribution, and avoid the problems of wrinkling on the sidewalls, excessive thinning at the bottom, or even cracking that are common with traditional one-step stamping. Attached Figure Description

[0021] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0022] Figure 1 This is a flowchart of the thermoforming process for an integral intake duct lip.

[0023] Figure 2 This is a schematic diagram of a ring-shaped billet.

[0024] Figure 3 This is a schematic diagram of the mold.

[0025] Figure 4This is a schematic diagram showing the different forms of the blank in the thermoforming process. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0027] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0028] Figure 3 The mold used for thermoforming is shown, which includes a punch 1, a die 2 and a blank holder structure not shown in the figure. The punch 1 is designed according to the shape of the inner surface of the lip, fixed on the upper base of the press, and a blank holder allowance is reserved. The die 2 is designed according to the outer surface of the lip, fixed on the lower base of the press, and a blank holder allowance is reserved.

[0029] like Figure 1 The process flow diagram shown takes the thermoforming of an integral intake duct lip as an example. This thermoforming process can also be used for similar lip-type parts, and includes the following steps:

[0030] 1. The raw material is aluminum alloy sheet, which is cut into a ring-shaped billet. The outer diameter of the billet does not exceed 3200mm, the inner diameter does not exceed 310mm, and the thickness is not less than 2mm. The billet 3... Figure 2 As shown in the image.

[0031] 2. First, heat the billet to 480℃-500℃ (20℃-40℃ below solution temperature) and hold for 0.2-0.5 hours. Then transfer it to the installed die, with a transfer time not exceeding 10 seconds. The shape of the billet before pre-stamping is as follows: Figure 4 As shown in 3a.

[0032] 3. After the blank is transferred to the correct position, a first-step stamping is performed. The main hydraulic cylinder connected to the punch is activated, causing the punch to stamp the blank. Stamping stops once the preset position is reached. The downward pressure does not exceed 1 / 3 of the total depth of the lip, initially forming a shallow cavity structure of the lip and creating the initial blank. The stamping time does not exceed 5 seconds. The pre-stamped blank is as follows: Figure 4 As shown in 3b.

[0033] 4. Remove the initial blank, heat it to 520℃-540℃ (solution state) according to the specifications and keep it at that temperature for 0.5-1h. Then transfer it to the installed die, and the transfer time should not exceed 10s.

[0034] 5. After the blank is transferred to the correct position, a second stamping is performed. The main hydraulic cylinder connected to the punch is activated, causing the punch to press the blank until the preset position is reached. The pressing amount is the total depth of the part, forming a deep cavity structure with a lip, thus creating the final blank. The stamping time should not exceed 5 seconds. The final blank is as follows: Figure 4 As shown in 3c.

[0035] 6. Finally, cut off the edge material and machine the inner and outer surfaces to the finished size.

[0036] Compared with the prior art, the aforementioned embodiments have the following beneficial effects:

[0037] 1. Compared with the traditional segmented process, the lip prepared by the integral thermoforming process can reduce the weight by more than 5kg. In addition, the dimensional accuracy tolerance of the surface can reach 14mm, and the mechanical properties are improved by 20% compared with riveting or welding at the interface.

[0038] 2. The use of integral thermoforming process to replace the traditional segmented process can ensure that the blank is subjected to uniform stress in all parts, and reduce the serious springback and wrinkling phenomenon after forming.

[0039] 3. Compared with the liquid-filled deep drawing process, the above-mentioned implementation method is a hot process, and the material has higher plasticity during forming, making it less prone to thinning and cracking.

[0040] 4. The "two-step stamping" process is used for forming. The solution treatment is added between the two stamping steps, which can homogenize the structure, accelerate the stress distribution, and avoid the problems of wrinkling on the sidewalls, thinning of the bottom, or even cracking caused by traditional one-step stamping.

[0041] In a preferred embodiment, during the pre-stamping and secondary stamping processes, the die and punch do not require mold heating, and a cooling medium is circulated at the base where the mold is installed, so that the blank achieves a quenching effect during the stamping process.

[0042] When using different materials for the aforementioned thermoforming process of lip-type parts, some parameters can be adjusted. For example, the amount of pre-stamping may not exceed 1 / 3 of the total lip depth, and the outer ring diameter, inner ring diameter, and thickness of the blank may be limited to the aforementioned specific values.

[0043] Example 1:

[0044] (1) The raw material used is 2219 aluminum alloy ring blank, with a maximum diameter of 3200mm, a minimum diameter of 310mm, and a thickness of 2.5mm.

[0045] (2) First, heat the billet to 480°C and keep it at that temperature for 0.4 hours according to the specifications. Then transfer it to the installed die. The transfer time is 8 seconds.

[0046] (3) After the blank is transferred to the position, a step of stamping is performed. The main hydraulic cylinder connected to the punch is started so that the punch can stamp the blank. After reaching the preset position, the stamping stops. The pressing amount is 1 / 3 of the total depth of the part, and a shallow cavity structure of the lip is initially formed to form the initial blank. The stamping time is 4s.

[0047] (4) Take out the initial blank, heat it to 520℃ according to the specification and keep it at that temperature for 0.6h, and then transfer it to the installed die. The transfer time is 6s.

[0048] (5) After the blank is transferred to the position, the second-step stamping is carried out. The main hydraulic cylinder connected to the punch is started so that the punch can stamp the blank. After reaching the preset position, the stamping is stopped. The amount of pressure is the total depth of the part, forming a deep cavity structure of the lip, forming the final blank. The stamping time is 4s.

[0049] (6) Finally, the edge material is removed and the inner and outer surfaces are machined to the finished size.

[0050] Example 2:

[0051] (1) The raw material used is 2618 aluminum alloy ring billet with a maximum diameter of 3000mm, a minimum diameter of 290mm, and a thickness of 2.5mm.

[0052] (2) First, heat the billet to 500℃ and keep it at that temperature for 0.2h according to the specifications, and then transfer it to the installed die. The transfer time is 8s.

[0053] (3) After the blank is transferred to the position, a step of stamping is performed. The main hydraulic cylinder connected to the punch is started so that the punch can stamp the blank. After reaching the preset position, the stamping stops. The pressing amount is 1 / 4 of the total depth of the part, and a shallow cavity structure of the lip is initially formed to form the initial blank. The stamping time is 4s.

[0054] (4) Take out the initial blank, heat it to 540℃ according to the specification and keep it at that temperature for 0.8h, and then transfer it to the installed die. The transfer time is 6s.

[0055] (5) After the blank is transferred to the position, the second-step stamping is carried out. The main hydraulic cylinder connected to the punch is started so that the punch can stamp the blank. After reaching the preset position, the stamping is stopped. The amount of pressure is the total depth of the part, forming a deep cavity structure of the lip, forming the final blank. The stamping time is 4s.

[0056] (6) Finally, the edge material is removed and the inner and outer surfaces are machined to the finished size.

[0057] Example 3:

[0058] (1) The raw material used in this scheme is 2618 aluminum alloy ring billet with a maximum diameter of 2900mm, a minimum diameter of 290mm, and a thickness of 2.5mm.

[0059] (2) First, heat the billet to 490°C and keep it at that temperature for 0.3 hours according to the specifications. Then transfer it to the installed die. The transfer time is 8 seconds.

[0060] (3) After the blank is transferred to the position, a step of stamping is performed. The main hydraulic cylinder connected to the punch is started so that the punch can stamp the blank. After reaching the preset position, the stamping stops. The pressing amount is 1 / 5 of the total depth of the part, and a shallow cavity structure of the lip is initially formed to form the initial blank. The stamping time is 3s.

[0061] (4) Take out the initial blank, heat it to 510℃ according to the specification and keep it at that temperature for 0.7h, and then transfer it to the installed die. The transfer time is 6s.

[0062] (5) After the blank is transferred to the position, the second-step stamping is carried out. The main hydraulic cylinder connected to the punch is started so that the punch can stamp the blank. After reaching the preset position, the stamping is stopped. The amount of pressure is the total depth of the part, forming a deep cavity structure of the lip, forming the final blank. The stamping time is 5s.

[0063] (6) Finally, the edge material is removed and the inner and outer surfaces are machined to the finished size.

[0064] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A process for the production of an integral lip thermoformed, characterized in that, The method comprises the following steps: providing a mold comprising a male die and a female die, the male die being arranged according to the inner surface shape of the lip, and the female die being arranged according to the outer surface of the lip; selecting an annular blank; heating the blank to 20-40 ℃ below the solid solution state and keeping the temperature; transferring the blank to the female die, and pre-stamping the blank by the male die, stopping the stamping when the pre-stamping position is reached, and forming a shallow cavity structure of the lip, i.e. an initial parison; taking out the initial parison, heating it to the solid solution state and keeping the temperature; transferring the initial parison to the female die, and secondarily stamping the initial parison by the male die, stopping the stamping when the pre-stamping position is reached, and forming a deep cavity structure of the lip, i.e. a final parison; processing the final parison to the size of the finished product.

2. The integral lip thermoforming fabrication process of claim 1 wherein, During the pre-stamping and secondary stamping, the female die and the male die do not need to be heated, and a cooling medium is passed through the base on which the mold is installed, so that the blank is quenched during the stamping process.

3. The integral lip thermoforming fabrication process of claim 1 wherein, The blank is made of an aluminum alloy material.

4. The integral lip thermoforming fabrication process of claim 1 wherein, The blank is made of 2219 aluminum alloy plate or 2618 aluminum alloy plate.

5. The integral lip thermoforming fabrication process of any one of claims 1 to 4, wherein, The pre-stamping amount is not more than 1 / 3 of the total depth of the lip.

6. The integral lip thermoforming fabrication process of claim 1 wherein, The outer ring diameter of the blank is not more than 3200 mm, the inner ring diameter is not more than 310 mm, and the thickness is not less than 2 mm.

7. The integral lip thermoforming fabrication process of claim 1 wherein, The time for transferring the blank each time is not more than 10 s, and the stamping time each time is not more than 5 s.

8. The integral lip thermoforming fabrication process of claim 1 wherein, The lip is an air inlet lip of an air inlet duct of an aircraft engine nacelle.

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