A semi-open precision thermoforming die and forming method for a thin-walled part with a taper

Abstract

A precision thermoforming mold and forming method for a semi-open, tapered, thin-walled part is disclosed. The forming mold includes a lower template, a punch, and a die. The punch is fixedly connected to the lower template. A material support plate is provided above the lower template, and a square hole in the center of the material support plate is movably fitted onto the outer circumferential surface of the punch. The top surface of the punch is semi-cylindrical in the middle and semi-conical at both ends, with downwardly extending strip grooves on the semi-conical surfaces. The die has an inwardly concave surface that matches the top surface of the punch, and punch inserts are provided at both ends of the die, extending downward and inserting into the strip grooves. Ejector pin holes are provided on the lower template. The punch inserts are used to reverse-stretch part of the material at both tapered ends into the strip grooves. Finally, the mold is closed to obtain a thermoformed blank. This method effectively overcomes the problem of wrinkling in the tapered section of the part during forming.

Description

Technical Field

[0001] This invention relates to the field of mold technology for machining parts for aero-engines, and in particular to a precision thermoforming mold and forming method for a semi-open, tapered, thin-walled part. Background Technology

[0002] Combination Figure 1 , Figure 2 The diagram shows the structure of a semi-open conical thin-walled part. This semi-open conical skin is an important component of an aero-engine. The middle section of the part is a nearly 1 / 4 cylindrical shape with flanges, and the two ends are nearly 1 / 4 conical cylindrical shapes with flanges. The part has a relatively complex structure and is made of titanium alloy. The conventional processing method for this part is to first hot press out the cylindrical conical main structure and then weld three flanges (the three flanges are the flanges at the cylindrical section and the flanges at the conical sections at both ends). This method has significant drawbacks, mainly: (1) During the pressing process, due to the complex structure of the part, the blank cannot be positioned, and the surface cannot be well controlled; (2) The two ends of the part are conical, and excessive material is fed to the two ends of the part during pressing, resulting in severe wrinkling. The wrinkled areas are mainly located at the ends of the cones, specifically as follows: Figure 3 As shown. Furthermore, given that the material is titanium alloy, wrinkling is difficult to correct, resulting in a high scrap rate. Also, the three flange sections are welded on after the main body is formed, which does not meet the product design drawings' requirements for the number of welds. Currently, there is no mature thermoforming technology or experience for similar parts.

[0003] In the prior art, patent application CN104001811A discloses a thermoforming mold and forming method for TC4 titanium alloy angular thin-walled parts; patent application CN111745027A discloses a forming method for saddle-shaped skin parts; and patent application CN107649590A discloses a skin stretching mold and its stretching method. However, the mold structures used in the above-mentioned prior art patents cannot solve the problems of wrinkling at the end of the cone during the forming of a semi-open conical skin, as well as the problem of the material not being positioned. Summary of the Invention

[0004] The main objective of this invention is to provide a precision thermoforming mold and forming method for semi-open tapered thin-walled parts, aiming to solve the aforementioned technical problems.

[0005] To achieve the above objectives, the present invention proposes a precision thermoforming mold for semi-open conical thin-walled parts, comprising a lower template, a punch, and a die. The punch is fixedly connected to the lower template. A support plate is provided above the lower template, and the square hole in the middle of the support plate is movably fitted onto the outer circumferential surface of the punch. The top surface of the punch is semi-cylindrical in the middle and semi-conical at both ends, with a downwardly extending strip groove provided on the semi-conical surface. The die has an inwardly concave surface that matches the top surface of the punch, and punch inserts are provided at both ends of the die, extending downward and inserted into the strip groove. An ejector pin hole is provided on the lower template.

[0006] Preferably, the bottom surface of the die extends outward from both sides of the concave surface edge to form an extension surface.

[0007] Preferably, a positioning boss is provided on the top edge of the material support plate, so that the top surface of the material support plate forms a positioning cavity.

[0008] Preferably, a mounting block is integrally formed on the top of the punch insert, and a recess is provided on the top surface of the die. The mounting block is fixed in the recess by a first screw and a first cylindrical pin.

[0009] Preferably, the punch and the lower template are fastened together by a second screw and a second cylindrical pin.

[0010] Preferably, lifting shafts are provided at both ends of the lower template, and lifting bolts are provided at both ends of the concave mold.

[0011] Preferably, the lower end face of the punch insert is inclined, and the inclination direction is consistent with that of the semi-conical surface at the top of the punch.

[0012] Preferably, the lower end face of the punch insert is set as an arc-shaped surface, and the arc-shaped surface smoothly transitions with the two sides of the punch insert.

[0013] Preferably, multiple relief grooves are provided on the bottom surface of the lower template.

[0014] On the other hand, the present invention also proposes a precision thermoforming method for semi-open tapered thin-walled parts, using the above-mentioned thermoforming mold, including the following steps:

[0015] Step S1: Fix the lower template on the lower platform of the thermoforming machine, fix the cavity mold on the upper platform of the thermoforming machine, and then close the mold and shut the oven door of the thermoforming machine;

[0016] Step S2: After heating to the set molding temperature, punch holes in the thermoforming machine oven door, use the ejector pin of the thermoforming machine to pass through the ejector pin hole of the lower template to lift the support plate, place the flat blank on the support plate and position it; the die descends to press the blank, close the oven door, and perform segmented multiple pressing, using the punch insert to reverse stretch part of the blank at both ends of the cone into the strip groove; finally close the mold to obtain the thermoformed blank, the thermoformed blank has flange edges on both sides, and forms a reverse stretched concave part in the semi-conical part;

[0017] Step S3: Cut along the position of the thermoformed blank near the concave part, then laser drill holes in the flange edge and cut its edge; finally, two semi-open tapered thin-walled parts are obtained.

[0018] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0019] (1) To address the problem of complex part structures and difficulty in positioning the blank, this invention utilizes a forming mold to form a thermoformed blank from a single sheet of material in one step. This thermoformed blank has a profile portion and flange portions on both sides. Specifically, the stretched thermoformed blank has flange portions on both sides, a semi-circular portion in the middle, and semi-conical portions at both ends of the semi-circular portion. After cutting, two parts can be obtained. Since the profile portion and flange portion can be obtained from a single sheet of material during the forming process, the problem of positioning difficulties caused by first hot-pressing the cylindrical or conical main structure and then welding the three flange portions in the prior art is effectively overcome. At the same time, since a single sheet of material is used for forming, there is no weld seam problem.

[0020] (2) In response to the problem of wrinkling in the conical section of the part, the thermoforming mold structure of the present invention is provided with a punch insert for reverse stretching, which can pull the excessive material of the conical section into the strip groove of the punch during stretching, thereby eliminating the wrinkling problem.

[0021] (3) The thermoforming mold provided by the present invention has a positioning boss on the top edge of the support plate, so that the top surface of the support plate forms a positioning cavity, which can effectively solve the problem of positioning flat blanks; during the pressing process, the extension surface of the die and the top surface of the support plate clamp the flat blank together, which can ensure uniform force during the forming process.

[0022] (4) By using the precision thermoforming mold and forming method for semi-open tapered thin-walled parts provided by the present invention, two semi-open tapered thin-walled parts can be obtained after one-time forming and cutting, which effectively improves the processing efficiency of semi-open tapered thin-walled parts. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a structural schematic diagram of a semi-open, tapered, thin-walled part.

[0025] Figure 2 for Figure 1 A rotated view along direction A;

[0026] Figure 3 This is a schematic diagram illustrating the wrinkling process at the end of a cone using existing molding techniques.

[0027] Figure 4 This is a schematic diagram of a precision thermoforming mold for semi-open tapered thin-walled parts provided by the present invention;

[0028] Figure 5 for Figure 4 A partial sectional view of FF;

[0029] Figure 6 This is a schematic diagram of the punch structure in this invention;

[0030] Figure 7 This is a schematic diagram of a thermoformed blank.

[0031] Figure 8 for Figure 7 GG View.

[0032] Explanation of reference numerals: 1. Lower template; 101. Ejector pin hole; 102. Lightening groove; 2. Punch; 201. Strip groove; 3. Material support plate; 301. Positioning boss; 4. Die; 401. Extension surface; 5. Lifting shaft; 6. Punch insert; 601. Mounting block; 602. Arc-shaped surface; 7. First screw; 8. Lifting bolt; 9. Second screw; 10. First cylindrical pin; 11. Second cylindrical pin; 12. Thermoformed blank; 1201. Flange edge; 1202. Inner recess. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0035] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0036] Combination Figures 1 to 2 The diagram shows a structural schematic of a semi-open, tapered, thin-walled component. This semi-open, tapered skin is a crucial component of an aero-engine. The middle section of the component is a nearly quarter-cylinder shape with flanges, while both ends are nearly quarter-conical cylinders with flanges. The component has a relatively complex structure and is made of titanium alloy. Figure 3 The diagram shows a process of wrinkling the end of a cone using existing molding techniques.

[0037] Combination Figures 4 to 8 The image shows a specific embodiment of a precision thermoforming mold and forming method for a semi-open tapered thin-walled part provided by the present invention.

[0038] On the one hand, this embodiment provides a precision thermoforming mold for semi-open tapered thin-walled parts, such as... Figures 4 to 6 As shown, the thermoforming mold includes a lower template 1, a punch 2, and a die 4. The punch 2 is fixedly connected to the lower template 1. A material support plate 3 is provided above the lower template 1, and the square hole in the middle of the material support plate 3 is movably fitted onto the outer peripheral surface of the punch 2. The top surface of the punch 2 is semi-cylindrical in the middle and semi-conical at both ends. A downwardly extending strip groove 201 is provided on the semi-conical surface. The die 4 is provided with an inwardly concave surface that matches the top surface of the punch 2. Punch inserts 6 are provided at both ends of the die 4. The punch inserts 6 extend downward and are inserted into the strip groove 201. An ejector pin hole 101 is provided on the lower template 1.

[0039] Combination Figure 5 As shown, in order to increase the pressing effect of the flange edge of the part during part forming, the bottom surface of the die 4 extends outward from both sides of the concave surface edge to form an extension surface 401.

[0040] Combination Figure 4 and Figure 5 As shown, in order to facilitate the placement of the blank during molding, a positioning boss 301 is provided on the top edge of the support plate 3, so that the top surface of the support plate 3 forms a positioning cavity.

[0041] Combination Figure 4 and Figure 5 As shown, to facilitate the installation of the punch insert 6, an mounting block 601 is integrally formed on the top of the punch insert 6. A recess is provided on the top surface of the die 4. The mounting block 601 is fixed in the recess by the first screw 7 and the first cylindrical pin 10. After passing through the die 4, the punch insert 6 extends downward into the strip groove 201 of the punch 2. The first cylindrical pin 10 serves to position the punch insert 6, and the first screw 7 serves to fasten the connection. Further, the punch 2 and the lower template 1 are fastened together by the second screw 9 and the second cylindrical pin 11. The second screw 9 serves to fasten the connection, and the second cylindrical pin 11 serves to position the punch 2.

[0042] Combination Figure 5 As shown, in order to facilitate the lifting of the mold, lifting shafts 5 are provided at both ends of the lower mold plate 1, and lifting bolts 8 are provided at both ends of the concave mold 4.

[0043] Combination Figure 4 As shown, the lower end face of the punch insert 6 is inclined, which is consistent with the inclination direction of the semi-conical surface at the top of the punch 2. When the flat blank is stretched in the reverse direction, in order to avoid excessive stretching of the semi-conical part, the lower end face of the punch insert 6 is inclined, so the surface stretched in the reverse direction is also inclined.

[0044] Combination Figure 5 As shown, in order to avoid large stress concentration on the lower end face of the flat blank on the punch insert 6 and to avoid breaking the blank during the reverse stretching process, the lower end face of the punch insert 6 is set as an arc surface 602, and the arc surface 602 smoothly transitions with the two sides of the punch insert 6.

[0045] Combination Figure 4 As shown, in order to reduce the weight of the lower template 1 and facilitate lifting, multiple weight-reducing grooves 102 are provided on the bottom surface of the lower template 1.

[0046] On the other hand, this embodiment also provides a precision thermoforming method for semi-open tapered thin-walled parts, using the above-mentioned thermoforming mold, including the following steps:

[0047] Step S1: Fix the lower template 1 on the lower platform of the thermoforming machine, fix the cavity mold 4 on the upper platform of the thermoforming machine, and then close the mold and shut the oven door of the thermoforming machine.

[0048] Step S2: After heating to the set molding temperature, punch a hole in the thermoforming machine oven door. Use the ejector pin of the thermoforming machine to pass through the ejector pin hole 101 of the lower template 1 to lift the support plate 3, and place the flat blank in the positioning cavity on the support plate 3 for positioning. The die 4 moves down to press the blank, the oven door is closed, and multiple segments are pressed down. The punch insert 6 is used to stretch the blank at both ends of the tapered part in the opposite direction into the strip groove 201. Finally, the mold is closed to obtain the thermoformed blank 12, as shown in the figure. Figure 7 , Figure 8 As shown, the thermoformed blank 12 has flange edges 1201 on both sides, and a reverse-stretched concave portion 1202 is formed in the semi-conical part.

[0049] Step S3: Cut along the position of the thermoformed blank 12 near the concave part 1202, then laser drill holes in the flange edge 1201 and cut its edge; finally, two semi-open tapered thin-walled parts are obtained.

[0050] To address the problem of complex part structures and difficulty in positioning raw materials, this invention utilizes a forming mold to form a thermoformed blank 12 from a single sheet of material in a single process. This blank has a profiled portion and flange edges 1201 on both sides. Specifically, the stretched thermoformed blank 12 has flange edges 1201 on both sides, a semi-circular portion in the middle, and semi-conical portions at both ends of the semi-circular portion. A reverse-stretched concave portion 1202 is formed in the semi-conical portion. After cutting, two parts can be obtained. Since the profiled portion and flange edges 1201 can be obtained from a single sheet of material during the forming process, the problem of positioning difficulties arises in existing technologies that first hot-press out cylindrical and conical main structures and then weld three flange sections. Furthermore, using a single sheet of material eliminates the need for weld seams.

[0051] To address the problem of wrinkling in the conical portion of a part, the thermoforming mold structure of this invention includes a punch insert 6 for reverse stretching, which can pull excess material from the conical portion during stretching into the strip groove 201 of the punch 2, thus eliminating the wrinkling problem.

[0052] The thermoforming mold provided by this invention has a positioning boss 301 on the top edge of the support plate 3, which forms a positioning cavity on the top surface of the support plate 3, effectively solving the problem of positioning flat blanks. During the pressing process, the extension surface 401 of the die 4 and the top surface of the support plate 3 together clamp the flat blank, ensuring uniform force during molding.

[0053] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for precision thermoforming of a semi-open, tapered, thin-walled part, characterized in that: The thermoforming mold used includes a lower template (1), a punch (2), and a die (4). The punch (2) is fixedly connected to the lower template (1). A support plate (3) is provided above the lower template (1), and the square hole in the middle of the support plate (3) is movably fitted onto the outer circumferential surface of the punch (2). The top surface of the punch (2) is semi-cylindrical in the middle and semi-conical at both ends. A downwardly extending strip groove (201) is provided on the semi-conical surface. The die (4) is provided with an inwardly concave surface that matches the top surface of the punch (2). Punch inserts (6) are provided at both ends of the die (4). The punch inserts (6) extend downward and are inserted into the strip groove (201). A push rod hole (101) is provided on the lower template (1). Includes the following steps: Step S1: Fix the lower template (1) on the lower platform of the thermoforming machine, fix the die (4) on the upper platform of the thermoforming machine, and then close the mold and shut the oven door of the thermoforming machine; Step S2: After heating to the set molding temperature, open the oven door of the thermoforming machine, use the push rod of the thermoforming machine to pass through the push rod hole (101) of the lower template (1) to lift the support plate (3), place the flat blank on the support plate (3) and position it; the die (4) moves down to press the blank, close the oven door, and press down in sections multiple times, use the punch insert (6) to stretch the blank at both ends of the cone into the strip groove (201); finally close the mold to obtain the thermoformed blank (12), the thermoformed blank (12) has flange edges (1201) on both sides, and forms a reverse-stretched concave part (1202) in the semi-conical part; Step S3: Cut along the position of the thermoformed blank (12) near the concave part (1202), then laser drill holes in the flange edge (1201) and cut its edge; finally, two semi-open tapered thin-walled parts are obtained.

2. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: The bottom surface of the concave mold (4) extends outward from both sides of the concave surface edge to form an extension surface (401).

3. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: A positioning boss (301) is provided on the top edge of the material support plate (3), so that the top surface of the material support plate (3) forms a positioning cavity.

4. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: An mounting block (601) is integrally formed on the top of the punch insert (6), and a recess is provided on the top surface of the die (4). The mounting block (601) is fixed in the recess by the first screw (7) and the first cylindrical pin (10).

5. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: The punch (2) and the lower template (1) are fastened together by the second screw (9) and the second cylindrical pin (11).

6. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: Lifting shafts (5) are provided at both ends of the lower template (1), and lifting bolts (8) are provided at both ends of the die (4).

7. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: The lower end face of the punch insert (6) is inclined, which is consistent with the inclination direction of the semi-conical surface at the top of the punch (2).

8. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: The lower end face of the punch insert (6) is set as an arc surface (602), and the arc surface (602) smoothly transitions with the two sides of the punch insert (6).

9. The precision thermoforming method for a semi-open tapered thin-walled part as described in claim 1, characterized in that: Multiple light-reducing sinkholes (102) are provided on the bottom surface of the lower template (1).

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