Flanging Processing Method for Large Diameter Thin-Walled Cylinder Parts

Abstract

The present invention discloses a method for processing the bending of large-diameter thin-walled cylindrical parts, comprising the steps of material preparation, blanking, curling or rolling, welding, overall expansion, bending, and mold correction. In the present invention, overall expansion is adopted for the J-shaped outer flange structure and the cylinder to obtain a conical end face profile structure as the intermediate structure of the J-shaped structure, and then the conical structure is individually subjected to bending processing and mold correction processing to obtain the final J-shaped outer flange. The present invention solves the problem of welding deformation caused by traditional welding methods, avoids the problem that the contour of the J-shaped outer flange is not accurate enough and thus affects the subsequent assembly. The present invention also saves tooling costs and improves the quality of the profile forming.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing, and in particular relates to a reverse bending processing method for a large thin-walled cylindrical part. Background Art

[0002] The sheet metal parts on aircraft engines come in various shapes, ranging from small bracket-like parts to large cylinder-like parts. The structures and shapes of the parts also vary. In order to meet the assembly and performance requirements of the final product, the integrity of the part structure plays a key role.

[0003] like Figure 3 and Figure 4 The figure shows an "inner ring" component—a large-diameter, thin-walled sheet metal part with a J-shaped cross-section of length L1. The axial cross-section of the part is a cylindrical wave pattern. To ensure compatibility during later assembly and improve overall assembly quality, integral forming of this "inner ring" is crucial. The outer diameter of the J-shaped structure is ΦD, the outer diameter of the negative angle structure is Φd, and the outer diameter of the wave-shaped cylinder is ΦD1.

[0004] For this part, the traditional processing method is to use a segmented molding structure. Figure 4 The part is split at L2, formed into two parts, and then welded together using argon arc welding. However, this forming method is prone to uncontrollable welding deformation in the area near the weld, making it difficult to correct later. This results in poor part contour accuracy, especially in the J-shaped structure, which directly affects the assembly accuracy of the subsequent outer ring connection. Summary of the Invention

[0005] In response to the problems described in the background technology, the present invention aims to provide a method for bending large-diameter thin-walled cylindrical parts to solve the overall forming problem of similar parts, reduce the tooling and costs generated by multi-stage forming of parts, reduce the welding deformation of J-shaped external flanges in parts, and improve the surface processing quality of parts.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for flanging a large-diameter, thin-walled cylindrical part, wherein the large-diameter, thin-walled cylindrical part is a cylinder with a wavy circumferential surface, one end of the axial cross section of the cylinder has a J-shaped outer flange, and a negative angle is formed at the connection between the outer flange and the cylinder generatrix. The method comprises the following steps:

[0008] Step 1: Material preparation: Select a plate with the same thickness as the large-diameter thin-walled cylinder. Based on the cylindrical surface coaxial with the large-diameter thin-walled cylinder in the part drawing, take the generatrix length of the cylindrical surface plus the flattened length of the J-shaped outer flange and a margin as the plate width. Take the circumferential expansion length of the cylindrical surface plus a margin as the plate length.

[0009] Step 2: Cutting: Cut the plate according to the thickness, width and length determined in step 1, and then divide the plate into at least two equal pieces along the length direction;

[0010] Step 3, rolling or bending: rolling or bending the multiple plates in step 2 according to the same curvature;

[0011] Step 4: Welding: The multiple sheets that have been rolled or bent in step 3 are joined together to form a cylindrical or conical cylinder, and welding is performed at the joints.

[0012] Step 5: Overall bulging: placing the cylindrical body or the tapered cylindrical body into a bulging die, and using the bulging die to perform overall bulging forming on the cylindrical body, the obtained profile includes a circumferential wavy profile, a tapered end profile, a cylindrical profile connecting the circumferential wavy profile and the tapered end profile, and a negative angle feature between the cylindrical surface and the circumferential wavy profile, wherein the taper angle of the tapered end profile is A;

[0013] Step 6: Bending: Use a roller mold to bend the tapered end surface in step 5 to obtain a partial arc segment connected to the cylindrical surface in the J-shaped outer flange. The roller mold includes an upper roller and a lower roller with parallel rotating axes. The axial end surface of the lower roller has a chamfer for forming the partial arc segment of the J-shaped outer flange. The gap between the upper roller and the lower roller is used to accommodate the tapered end surface. The rotating axes of the upper roller and the lower roller are along the radial direction of the cylinder or the tapered cylinder, and move around the circumference of the cylinder or the tapered cylinder to perform bending.

[0014] Step 7, correction: Use a mold that is consistent with the J-shaped outer flange profile and has a negative angle feature to correct the J-shaped outer flange to obtain the accurate shape of the J-shaped outer flange.

[0015] Furthermore, in the step 1, the distances from the generatrix of the cylindrical surface to the crests and troughs of the wavy profile on the circumferential surface of the large-diameter thin-walled cylindrical part are equal.

[0016] Furthermore, in step 2, the plate is divided into three equal pieces along the length direction.

[0017] Furthermore, in step five, the expansion mold includes a male mold for the inner surface and a female mold for the outer surface, and both the male mold and the female mold are composed of multiple identical expansion petals, wherein the male mold is slidably connected to multiple inclined tracks distributed on the first circumference, and the female mold is slidably connected to multiple inclined tracks distributed on the second circumference, and the first circumference is concentric and coplanar with the second circumference and is located inside the second circumference.

[0018] Furthermore, in step five, the taper angle A is set to 135°.

[0019] Furthermore, the step between step five and step six also includes a trimming process, in which the large end of the tapered end surface is cut to obtain the accurate length of the J-shaped outer flange.

[0020] Compared with the traditional processing method, the advantages of the present invention include the following aspects:

[0021] 1. It saves the cost of tooling and rough materials and simplifies the mold structure. In step six of the present invention, a bending process is adopted, and the bending is to extend and bend the sheet material through a roller mold, which is not a conventional flanging mold or bulging mold. The roller mold is small in size, low in cost, short in processing time, relatively small in deformation, and not prone to cracking problems. Compared with bulging molds or flanging molds that are larger than large-diameter thin-walled cylindrical parts, the cost of roller molds is almost negligible. The tapered end face profile on the rough material saves the rough material cost compared to traditional bulging or flanging, which has a high probability of causing cracking at the bend and making the parts scrapped.

[0022] 2. The parts processed by the present invention are integrally formed structures, which avoid the segmented welding of the J-shaped outer flange and the wavy cylinder in the parts, thereby avoiding welding deformation of the parts and improving the strength and surface quality of the parts.

[0023] 3. This invention ensures the compatibility of parts in later assembly and improves the overall performance of the assembly. Since the J-shaped outer flange and the wavy cylinder are integrally expanded, and the roller bending and tire correction are used, the J-shaped outer flange has precise dimensions, which is beneficial to the subsequent assembly process.

[0024] 4. The present invention shortens the processing cycle. Traditional processing methods mainly involve piece-by-piece forming (the J-shaped outer flange and the wavy cylinder are formed independently), welding after forming, and correction after welding. The processing method of the present invention uses direct expansion after welding. Compared with traditional processing methods, the welding is flat-plate welding (traditional welds have a wavy structure) and one less forming step (the traditional J-shaped outer flange and the wavy cylinder are formed independently, while the integral forming method of the present invention has one more forming step), which greatly shortens the processing cycle.

[0025] At present, the processing method and the mold of the present invention have been used on site and have achieved the purpose and requirements of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of splicing multiple plates into a cylindrical body in the processing method of the present invention;

[0027] Figure 2 Schematic diagram of the cylinder after overall expansion in the present invention;

[0028] Figure 3 It is a schematic diagram of a large diameter thin-walled cylindrical part;

[0029] Figure 4 yes Figure 3 A magnified schematic diagram of the local area F in the middle;

[0030] Figure 5 This is a schematic diagram of the plate size calculation in the material preparation step of the processing method of the present invention;

[0031] Figure 6 It is a schematic diagram of the bending roller;

[0032] Figure 7 It is a schematic diagram of the bending process;

[0033] Figure 8 This is a schematic diagram of a curved-edge tire. DETAILED DESCRIPTION

[0034] The present invention is further described below with reference to the accompanying drawings and specific embodiments. However, it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various modifications, substitutions and changes made according to common technical knowledge and customary means in the field are included in the scope of the present invention.

[0035] The core principle of the present invention's processing method for "inner ring" parts is to use an expansion die to form the wavy structure of the part's main body and a preformed structure before the J-shaped structure is bent. Then, through roller bending and mold correction, the preformed structure is formed into a J-shaped outer bend in one step. In simple terms, the implementation of this core principle includes the following steps:

[0036] (1) Process the required plate with the same thickness as the final large-diameter thin-walled cylindrical part (for example, 0.6 mm) into a cylindrical or conical structure, such as Figure 1 It is a cylindrical structure with a diameter of Φ and a height of h.

[0037] (2) Place the cylindrical raw material into the bulging die with internal expansion and external contraction to form the main body surface and form the intermediate structure of the part, such as Figure 2 The intermediate structure includes three features: the first is the circumferential wavy surface, the second is the tapered end face profile (taper angle is A), and the third is the negative angle.

[0038] (3) Figure 2 The tapered end surface is used as the bending part to perform roller bending and tire correction to form a J-shaped outer flange. Figure 3 .

[0039] The method for processing a large-diameter thin-walled cylindrical part of the present invention mainly comprises the following steps:

[0040] Step 1, material preparation: select a plate with the same thickness as the large diameter thin wall cylinder part, based on the cylindrical surface coaxial with itself in the part drawing of the large diameter thin wall cylinder part, such as Figure 5 As shown, a cylindrical surface with a generatrix located between the peak and the trough of the wavy profile on the circumferential surface of the cylindrical surface is selected. The width of the plate is obtained by adding the generatrix length of the cylindrical surface plus the length of the J-shaped outer flange structure after flattening (straightening) plus a margin. The length of the plate is obtained by adding the circumferentially expanded length of the cylindrical surface plus a margin.

[0041] Step 2: Processing of the raw material: Cut the material according to the thickness, width and length of step 1 to obtain a plate, then divide the plate into 3 equal pieces along the length direction, roll each plate into a circle and weld it to form Figure 1 The cylindrical raw material (width is h, diameter is Φ) is formed by rolling and welding three rectangular plates;

[0042] Step 3: Use Figure 2 The bulging female mold and the male mold with the same inner and outer surfaces will Figure 1 The cylindrical wool is formed into Figure 2 The bulging die is formed by a plurality of radially movable bulging petals (the bulging petals corresponding to the male die are squeezed from the inside to the outside along the radial direction, and the bulging petals corresponding to the female die are squeezed from the outside to the inside along the radial direction, and the male and female dies are combined to form) to bulge the inner and outer surfaces of the cylindrical raw material. Figure 3 and Figure 4 As shown, the outer surface of the part not only finally reverses the bend, but also has a negative angle near the bend (that is, the surface shrinks inward, which can also be understood as the inner diameter becoming smaller inward). Due to the existence of the negative angle, the female mold of the outer surface cannot adopt an integral structure when the part is reversely bent. The present invention makes the female mold of the outer surface into a petal structure (for example, the female mold is made into 3 petals or multiple petals, and an outer hoop is used for limiting the position, refer to Chinese invention patent CN117260278A, 2023.12.22, aircraft engine lobe mixer processing method and outer expansion petal design in bulging mold), and cooperates with the male mold to facilitate the placement of the cylinder into the mold before bulging, and facilitate the removal of the part after bulging, thereby solving the problem of the part being unable to be removed due to the existence of the negative angle. Figure 2The taper angle A in the figure is a difficult point in the design of the bulging die and the determination of the blank. The calculation and value of this angle are related to whether the part can be formed into the final part and whether the blank is usable. If the taper angle A is too large, it will be difficult or impossible to form the final bend of the part; if the taper angle A is too small, the blank cannot be placed in the bulging die, and the semi-finished part will eventually have poor molding quality due to the excess material. When selecting the value, the blank and the forming distance should be comprehensively considered, and the taper angle A should be selected. Figure 4 The middle tangent position (the arc of the J-shaped outer flange) and 135° are formed after forming. Figure 2 The uppermost tapered end face profile;

[0043] Step 4: Figure 6 , is a roller die used for bending, which consists of an upper roller, a lower roller (H in the figure is the axial length of the upper roller and the lower roller) and a baffle (the baffle is at Figure 6 The left end face of the lower roller in the figure has a chamfer R, which is used to bend the conical end face to form a partial arc. When bending the edge, the conical end face is inserted into the gap between the upper roller and the lower roller to keep Figure 6 The middle H direction (rotation axis direction) along the radial direction of the cylinder makes the upper roller and the lower roller circle around the conical end surface. The conical end surface is deformed and bent under the extrusion of the upper roller, the lower roller and the chamfer R, thereby Figure 7 The OM segment bending forming in the middle left figure is Figure 7 The shape shown in the middle diagram (i.e., the arc forming the OL segment);

[0044] Step 5, finally pass Figure 8 The mold shown corrects the final fit of the flange of the part, that is, the molded Figure 7 The LM segment in the center-right image ultimately forms a J-shaped flange. The mold's profile includes the cylindrical surface of the cylinder, the J-shaped flange, and negative angle features (the thick black line represents the J-shaped flange, and the thin line is the mold outline, which partially covers the mold outline). The J-shaped flange serves as a connection to the outer ring during assembly. Its molding quality and whether the part deforms are closely related to its compatibility with the outer ring during assembly.

[0045] In the present invention, Figure 7 As shown, after bulging, the tapered end surface can be trimmed to obtain the accurate size of the J-shaped outer flange (i.e. Figure 7 The length is OM in the middle right picture), so the J-shaped outer flange after bending and shaping does not need to be trimmed, ensuring the accuracy of subsequent assembly.

[0046] Any matters not described in detail in the present specification are prior art known to those skilled in the art. Although the above description of the present invention is based on illustrative embodiments to facilitate understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. As long as various modifications are within the spirit and scope of the present invention as defined and determined by the appended claims, such modifications will be obvious to those skilled in the art, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. A method for flanging a large-diameter, thin-walled cylindrical part, wherein the large-diameter, thin-walled cylindrical part is a cylinder with a wavy circumferential surface, one end of the axial cross section of the cylinder has a J-shaped outer flange, and the connection between the outer flange and the cylinder generatrix has a negative angle, characterized in that: The processing method comprises the following steps: Step 1: Material Preparation: Select a plate with the same thickness as the large-diameter thin-walled cylindrical part. Based on the cylindrical surface coaxial with itself in the part drawing of the large-diameter thin-walled cylindrical part, select a cylindrical surface with a generatrix midway between the peaks and troughs of the wavy contour of the cylindrical surface. The width of the plate is the length of the generatrix of the cylindrical surface plus the flattened length of the J-shaped outer flange and an allowance. The length of the plate is the circumferentially expanded length of the cylindrical surface plus an allowance. Step 2: Cutting: Cut the plate according to the thickness, width and length determined in step 1, and then divide the plate into at least two equal pieces along the length direction; Step 3, rolling or bending: rolling or bending the multiple plates in step 2 according to the same curvature; Step 4: Welding: The multiple sheets that have been rolled or bent in step 3 are joined together to form a cylindrical or conical cylinder, and welding is performed at the joints. Step 5: Overall bulging: placing the cylindrical body or the tapered cylindrical body into a bulging die, and using the bulging die to perform overall bulging forming on the cylindrical body, the obtained profile includes a circumferential wavy profile, a tapered end profile, a cylindrical profile connecting the circumferential wavy profile and the tapered end profile, and a negative angle feature between the cylindrical surface and the circumferential wavy profile, wherein the taper angle of the tapered end profile is A; Step 6: Bending: Use a roller mold to bend the tapered end surface in step 5 to obtain a partial arc segment connected to the cylindrical surface in the J-shaped outer flange. The roller mold includes an upper roller and a lower roller with parallel rotating axes. The axial end surface of the lower roller has a chamfer for forming the partial arc segment of the J-shaped outer flange. The gap between the upper roller and the lower roller is used to accommodate the tapered end surface. The rotating axes of the upper roller and the lower roller are along the radial direction of the cylinder or the tapered cylinder, and move around the circumference of the cylinder or the tapered cylinder to perform bending. Step 7, correction: Use a mold that is consistent with the J-shaped outer flange profile and has a negative angle feature to correct the J-shaped outer flange to obtain the accurate shape of the J-shaped outer flange.

2. The method for flanging a large-diameter, thin-walled cylindrical part according to claim 1, characterized in that: In the step 1, the distances from the generatrix of the cylindrical surface to the crests and troughs of the wavy profile on the circumferential surface of the large-diameter thin-walled cylindrical part are equal.

3. The method for flanging a large-diameter, thin-walled cylindrical part according to claim 1, wherein: In the step 2, the plate is divided into three equal pieces along the length direction.

4. The method for flanging a large-diameter, thin-walled cylindrical part according to claim 1, characterized in that: In step five, the expansion mold includes a male mold for the inner surface and a female mold for the outer surface, and both the male mold and the female mold are composed of multiple identical expansion petals, wherein the male mold is slidably connected to multiple inclined tracks distributed on the first circumference, and the female mold is slidably connected to multiple inclined tracks distributed on the second circumference, and the first circumference is concentric and coplanar with the second circumference and is located inside the second circumference.

5. The method for flanging a large-diameter, thin-walled cylindrical part according to claim 1, characterized in that: In step 5, the taper angle A is set to 135°.

6. The method for flanging a large-diameter, thin-walled cylindrical part according to claim 1, characterized in that: The process between step five and step six also includes trimming, in which the large end of the tapered end face is cut to obtain the accurate length of the J-shaped outer flange.

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