Machining method and die structure for flame tube cap cover with inwards-turned special-shaped hole

Abstract

The invention discloses a machining method and a mold structure for a flame tube cap cover with an inwards-turned special-shaped hole, and belongs to the technical field of metal plate forming. The method comprises the steps of laser blanking, pre-stretching, heat treatment, hydroforming and machining. Wherein the pre-stretching process and the liquid-filling forming process are continuously completed on the same set of composite die, specifically, the main body molded surface of the part is firstly stretched and formed, then high-pressure liquid is injected into a closed cavity, the special-shaped convex hull with the space angle is formed at a time through liquid pressure, and the main body molded surface is synchronously corrected. The die integrates stretching and liquid filling functions, a convex structure corresponding to the special-shaped convex hull and a hydraulic runner are arranged on the molded surface of a concave die of the die, and a convex die is provided with a groove matched with the convex die and an elastic blank holder assembly. The functions of multiple sets of traditional dies are integrated, the tool cost is remarkably reduced, meanwhile, the forming precision and the wall thickness uniformity of the complex special-shaped inward flanging hole are guaranteed through hydroforming, and parts are stable in quality and good in consistency.

Description

A method for processing an inwardly shaped flame tube cap and a mold structure Technical Field

[0001] This invention relates to the field of sheet metal forming technology, specifically to a method for processing an inwardly shaped flame tube cap and a mold structure. Background Technology

[0002] The flame tube cap is one of the main components of the engine flame tube. The main body of the part is a ring-shaped part with 20 irregularly shaped holes. The holes are oriented inwards and are irregularly shaped holes composed of φ6 and φH. The axis of the holes forms an angle α2 with the axis of the part. The height of the holes is H, and the center circle size of the holes is φ1. The main body surface of the part is formed by a smooth transition of the radius. The inner diameter of the part is φ2, and the outer diameter is φ5. The two-dimensional dimensions of the part are shown in Figure 1, and the three-dimensional structure is shown in Figure 2. Traditionally, similar parts are processed by stretching to form the main body surface, followed by punching, flanging, and turning. Traditional forming processes require at least three sets of molds, which are costly. After flanging, the holes are irregularly shaped and form an angle α2 with the axis of the part, making the design of the flanging molds difficult and resulting in unsatisfactory results that require correction.

[0003] While some advanced stamping forming methods exist in the prior art, such as the stamping forming method and mold for aerospace sheet metal parts with V-shaped flanges disclosed in Chinese invention patent CN105290227B, which can complete the forming and flanging of the V-shaped flange edge in one step through the coordinated work of upper and lower dies with specific structures, saving processes, this method is mainly aimed at parts with V-shaped flange characteristics. Its mold structure and forming principle do not solve the unique forming difficulties of irregularly shaped inward flanging holes at an angle to the axis in parts such as flame tube caps. Therefore, there is an urgent need for a targeted processing method and mold to effectively ensure the forming accuracy and quality of irregularly shaped flanging holes while reducing tooling costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method and mold structure for processing flame tube caps with inward-turning irregular holes. The method is reliable and effective, and can effectively ensure the dimensional accuracy of the parts.

[0005] The technical solution of this invention: A method for processing an inwardly shaped flame tube cap, comprising the following steps: Step 1: Laser blanking, cutting the sheet metal into a circular blank of a predetermined size; Step 2: Pre-stretching, placing the circular blank in a mold and stretching it to form the main body surface of the part; Step 3: Heat treatment, performing solution treatment on the pre-stretched part to eliminate forming stress; Step 4: Liquid filling forming, placing the heat-treated part back into the mold, injecting high-pressure liquid into the sealed cavity, using the liquid pressure to form an irregular convex bump on the main body surface, and simultaneously correcting the main body surface; Step 5: Machining the upper end face of the irregular convex bump to obtain an irregularly shaped folded hole, to achieve the final size and shape requirements.

[0006] Furthermore, the pre-stretching described in step S2 and the liquid filling forming described in step S4 are completed continuously on the same liquid filling forming equipment using the same set of composite molds that combine stretching and liquid filling functions.

[0007] Furthermore, after the orthodontic procedure, fluorescence detection is performed, and a perforation operation is performed on the irregular convex hull to obtain an irregular perforation.

[0008] A processing apparatus for implementing a processing method includes a lower template, a die fixedly mounted on the lower template, the working surface of the die being adapted to the main body surface of the part, and having a protrusion structure corresponding to the position of the irregular protrusion of the part, the die having a flow channel communicating with an external liquid pressurization system, the flow channel having an inlet and an outlet; it also includes a punch mounted above the die, the punch having a groove, which can perform mold closing and mold opening movements relative to the die; and a pressure ring assembly, including an outer pressure ring and an inner pressure ring, used to press the flange edge of the blank or part during the forming process.

[0009] Furthermore, it also includes an upper template and a guiding mechanism. The punch is connected to the upper fixed plate. The guiding mechanism includes a guide post disposed between the lower template and the upper fixed plate, and a positioning post is disposed on the upper fixed plate.

[0010] Furthermore, a support column assembly is connected above the outer pressure ring, and the inner pressure ring is connected to an elastic element via a connecting plate to provide a buffered pressure force.

[0011] Furthermore, the elastic element is a spring, and the connecting plate is connected to the upper fixed plate through the spring.

[0012] Furthermore, the punch has an annular structure, and its lower end face is provided with a groove that matches the protruding structure on the die.

[0013] Furthermore, the protrusions on the die are evenly distributed circumferentially, and the cavity below them is connected to the inlet and outlet through a flow channel.

[0014] Furthermore, the end point of the downward stroke of the punch and the die press together to form a closed cavity for stretching and forming the main body surface of the part; in this state, high-pressure liquid is injected into the closed space surrounded by the part, the punch and the die through the liquid inlet to perform the liquid filling forming process.

[0015] The beneficial effects of this invention are: This invention uses a set of molds to form parts, which saves the number of molds, greatly reduces tooling costs, and at the same time ensures the surface quality of the parts. The processing method is more reliable, and the processed parts have better consistency and higher quality. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the accompanying drawings used in the description of the embodiments 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 these drawings without creative effort.

[0017] Figure 1 is a plan view of the cap; Figure 2 is a BB section view of Figure 1; Figure 3 is a three-dimensional diagram of the cap; Figure 4 is a schematic diagram of the blank used to prepare the cap; Figure 5 is a schematic diagram of the mold structure; Figure 6 is an AA section view of Figure 5; Figure 7 is a schematic diagram of the die structure; Figure 8 is an AA section view of Figure 7; Figure 9 is a schematic diagram of the punch structure; Reference numerals: 1—lower template, 2—die, 3—punch, 4—outer pressure ring, 5—inner pressure ring, 6—connecting plate, 7—guide post, 8—first support post assembly, 9—second support post assembly, 10—upper template, 11—upper fixing plate, 12—positioning post, 13—spring, 14—bolt. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0019] Example 1: Referring to Figures 5 to 9, a composite mold device for forming an inwardly shaped flame tube cap is provided. This device integrates stretching and fluid filling forming functions, and its core structure includes a forming execution module, a pressing and guiding module, and a hydraulic system interface.

[0020] The forming execution module is the core of part forming, consisting of upper and lower working elements. The lower part is a die 2 fixedly mounted on the lower template 1 and secured with screws. The upper working surface of the die 2 is strictly adapted to the final body surface of the part, used to form the main contour of the part in the pre-stretching process. In particular, multiple protrusions are evenly distributed circumferentially on the surface of the die 2 (see Figures 7 and 8). The position, shape, and inclination angle of these protrusions correspond one-to-one with the 20 irregular protrusions required for the part, which is crucial for forming the protrusions in the subsequent liquid filling forming process. The die 2 has a flow channel machined inside, which connects to an external ultra-high pressure liquid pressurization system. This flow channel has an inlet and an outlet for injecting and discharging the pressure-transmitting medium into the sealed cavity during liquid filling forming.

[0021] The upper part is the punch 3, which mates with the die 2. It is connected to the upper template 10 via the upper fixed plate 11 and can perform vertical closing and opening movements relative to the die 2 under the drive of the press. The punch 3 is designed as a ring structure, and its lower end face has an annular groove that precisely matches the protrusion on the die 2, as shown in Figure 9. When the punch 3 descends to its end point and presses against the die 2, the two together form a closed cavity for stretching and forming the main body surface of the part. At the same time, the part, the punch 3, and the die 2 will also jointly form a sealed space that can be injected with high-pressure liquid.

[0022] To ensure uniform flow of the sheet metal during stretching, prevent wrinkling, and guarantee sealing during liquid filling, the device is equipped with a dual pressure ring assembly. This includes an outer pressure ring 4 and an inner pressure ring 5, which work together to press the annular flange edge of the blank or part during forming. The inner pressure ring 5 is connected to a set of springs 16 via a connecting plate 6. The other end of each spring 16 is fixed to the upper fixed plate 11, forming an elastic pressure system that provides flexible, buffered pressure force to accommodate different sheet thicknesses and compensate for equipment parallelism errors.

[0023] Guiding and positioning are achieved by guide pillars 7, which are fixed to the lower template 1 and pass through guide holes on the upper fixed plate 11 to ensure the alignment accuracy of the punch 3 and the die 2. In addition, the upper fixed plate 11 is also provided with positioning pillars 12 for assisting in mold installation and positioning on the press. The first support pillar assembly 8 is connected above the outer blank holder 4 to transmit the blank holder force applied by the press, and a second support assembly is also provided between the punch 3 and the upper fixed plate.

[0024] The device operates in two consecutive stages, both completed on the same liquid-filling forming machine: Pre-stretching stage: A circular blank is placed on the die 2, and its flange edge is pressed together by the outer pressure ring 4 and the inner pressure ring 5. The press drives the upper die section downwards, closing the punch 3 with the die 2, stretching the flat blank into a cup-shaped part with the main body profile.

[0025] Liquid filling and forming stage: Keeping the punch 3 and die 2 closed, ultra-high pressure liquid is injected into the sealed cavity formed by the part, punch 3, and die 2 through the liquid inlet of die 2. The liquid pressure causes the wall of the part, which has already been formed, to fit tightly against the surface of die 2, achieving surface finishing; at the same time, guided by specific protrusions on die 2, the high pressure liquid causes local expansion of the part wall material, precisely forming an irregularly shaped protrusion with an angled axis. This process utilizes the uniform and flexible characteristics of fluid pressure to complete the protrusion forming and the correction of the main body surface in one go, solving the problems of easy cracking and inaccurate surface of traditional mechanical flanging.

[0026] Example 2: Complete process flow for processing the inward-turned irregular-shaped flame tube cap using the device described in Example 1. The forming method steps are as follows: Step 1: Laser blanking. Using a specific sheet material with a thickness of 1.2mm, and based on the simulation-optimized unfolded shape, a circular blank of the required size is cut out using a laser cutting machine, as shown in Figure 4. This method has high blanking accuracy and no mold consumption.

[0027] Step 2: Pre-stretching. The circular blank obtained from laser cutting is placed in the composite mold of Example 1. The liquid filling forming equipment is started to perform the pre-stretching process, forming the main body surface of the part (i.e., the basic annular cap shape). This step is completed by the closing of the punch 3 and the die 2 of the mold.

[0028] Step 3: Heat treatment. The pre-stretched parts are solution treated. The purpose is to completely eliminate the work hardening and internal stress generated during the pre-stretching process, restore the material's plasticity, and provide a good material condition for the subsequent challenging liquid filling and bulging process. This is crucial for ensuring uniform wall thickness and forming limits.

[0029] Step 4: Liquid Filling and Forming. The heat-treated parts are placed back into the same cavity of the same mold. After mold closing, ultra-high pressure liquid is injected into the sealed cavity through the hydraulic channel of the mold. Under the action of high pressure liquid, the wall of the part undergoes plastic deformation: on the one hand, the main surface of the part is further corrected, and the mold fitting accuracy is greatly improved; on the other hand, under the constraint of specific protrusion structures on the die 2, 20 irregular protrusions at an angle α2 to the axis are bulged into the outer wall of the part. This step completes the surface correction and irregular feature forming in one go on the same equipment and tooling.

[0030] Step 5: Machining. The upper surface of the irregular convex bulge obtained after fluid filling and forming is CNC turned or milled to remove the top material, ultimately forming an irregular shaped hole that meets the φ6 and φH size requirements. At the same time, the final contour dimensions such as the inner and outer circles of the part are machined.

[0031] Step 6, Fluorescence detection: Perform fluorescence penetration testing on the finished parts to ensure that there are no defects such as cracks during the forming and processing of the parts, and to ensure the reliability of the final product quality.

[0032] The forming method and supporting equipment provided in this embodiment innovatively integrate the functions of multiple sets of molds, such as stretching molds, piercing molds, and correction molds required in traditional processes, into a single composite mold. This reduces the number of molds by more than two-thirds, significantly lowering tooling manufacturing and management costs. Liquid-filled forming utilizes the uniform force application of fluid pressure, resulting in smoother material flow. The formed irregularly shaped convex bulges have uniform wall thickness distribution, are free from mechanical friction scratches, and exhibit high surface accuracy. Simultaneously, the process incorporates heat treatment to eliminate stress and actively corrects the main body surface using the liquid-filling process, resulting in minimal springback, stable final dimensions, and excellent batch consistency. Traditional mechanical piercing is prone to cracking and inaccurate deformation for irregularly shaped holes with spatial angles along the axis. This method, through pre-forming the main body and high-pressure liquid expansion, gently forms the convex bulge feature, fundamentally avoiding the risk of cracking and perfectly achieving precise forming of complex irregularly shaped internal piercings.

[0033] The foregoing has provided a detailed description of the processing method and mold structure for an inwardly shaped flame tube cap provided by the present invention. Specific examples have been used to illustrate the structure and working principle of the invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for processing an inwardly shaped perforated flame tube cap, characterized in that: The process includes the following steps: Step 1: Laser blanking, cutting the sheet metal into circular blanks of a predetermined size; Step 2: Pre-stretching, placing the circular blanks in a mold and stretching them to form the main body surface of the part; Step 3: Heat treatment, performing solution treatment on the pre-stretched part to eliminate forming stress; Step 4: Liquid filling forming, placing the heat-treated part back into the mold, injecting high-pressure liquid into the sealed cavity, using the liquid pressure to form a shaped protrusion on the main body surface, and simultaneously correcting the main body surface; Step 5: Machining the upper surface of the shaped protrusion to obtain a shaped hole, to achieve the final size and shape requirements.

2. The method for processing the inward-turned irregular-shaped flame tube cap according to claim 1, characterized in that: The pre-stretching described in step S2 and the liquid filling forming described in step S4 are completed continuously on the same liquid filling forming equipment using the same set of composite molds that combine stretching and liquid filling functions.

3. The method for processing the inward-turned irregular-shaped hole flame tube cap according to claim 1, characterized in that: After the orthodontic treatment, fluorescence detection was performed, and a hole-making operation was performed on the irregular convex hull to obtain the irregular hole.

4. A processing apparatus for implementing the processing method according to any one of claims 1-3, characterized in that: The assembly includes a lower template (1), a die (2) fixedly mounted on the lower template (1), the working surface of the die (2) being adapted to the main body surface of the part, and having a protrusion structure corresponding to the irregular protrusion position of the part, the die (2) having a flow channel connected to an external liquid pressurization system, the flow channel having an inlet and an outlet; it also includes a punch (3) mounted above the die (2), the punch (3) having a groove, which can perform mold closing and mold opening relative to the die (2); and a pressure ring assembly, including an outer pressure ring (4) and an inner pressure ring (5), used to press the flange edge of the blank or part during the forming process.

5. The processing apparatus for the inverted irregular-shaped perforated flame tube cap according to claim 4, characterized in that: It also includes an upper template (10) and a guiding mechanism. The punch (3) is connected to the upper fixed plate (11). The guiding mechanism includes a guide post (7) set between the lower template (1) and the upper fixed plate (11). A positioning post (12) is set on the upper fixed plate (11).

6. The processing apparatus for the inward-turned irregular-shaped perforated flame tube cap according to claim 4, characterized in that: The outer pressure ring (4) is connected to a support column assembly (8) above it, and the inner pressure ring (5) is connected to an elastic element via a connecting plate (6) above it to provide a buffered pressure force.

7. The processing apparatus for the inverted irregular-shaped perforated flame tube cap according to claim 6, characterized in that: The elastic element is a spring (16), and the connecting plate (6) is connected to the upper fixed plate (11) through the spring (16).

8. The processing apparatus for the inward-turned irregular-shaped perforated flame tube cap according to claim 4, characterized in that: The punch (3) has an annular structure, and its lower end face is provided with a groove that matches the protruding structure on the die (2).

9. The processing apparatus for the inward-turned irregular-shaped perforated flame tube cap according to claim 4, characterized in that: The protrusions on the concave mold (2) are evenly distributed along its circumference, and the cavity below it is connected to the liquid inlet and liquid outlet through the flow channel.

10. The processing apparatus for the inverted irregular-shaped perforated flame tube cap according to claim 4, characterized in that: The end point of the downward stroke of the punch (3) is pressed together with the die (2) to form a closed cavity for stretching and forming the main body surface of the part; in this state, high-pressure liquid is injected into the closed space surrounded by the part, the punch (3) and the die (2) through the liquid inlet to perform the liquid filling forming process.

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