Design method for spinning sectioning mandrel of thin-wall curved generatrix piece with spiral inner rib

Abstract

The invention discloses a design method of a spinning sectioning mandrel for a thin-wall curved generatrix piece with a spiral inner rib. In the core mold for spinning the part with the spiral inner rib, a split core mold is arranged on the outer circumferential surface of a main core mold in a sleeving manner, and the end face of the tail end of the split core mold is attached to the surface of a base of the main core mold; the clamping block is sleeved on the outer circumferential surface of the tail end of the split core mold; and the main core mold and the split core molds are connected together by bolts through round holes in the end surfaces of the heads of the split core molds. The split core mold is formed by combining m active core mold petals and n passive core mold petals. The outer diameter of the split core mold is the same as the maximum diameter of the inner surface of a workpiece; axial key grooves are formed in the inner surfaces of the driving core mold petals and the driven core mold petals; and the inner surface of the split core mold is in clearance fit with the outer surface of the main core mold. According to the spinning forming method, smooth spinning forming of the thin-wall curved generatrix piece with the spiral inner rib is guaranteed, the production period is shortened, the production efficiency is improved, the production cost is reduced, the labor intensity is reduced, and the forming quality and the forming precision of the workpiece are improved.

Description

Technical Field

[0001] The present invention relates to the field of spin forming processing, and specifically to a design method for a split core mold for spinning a thin-walled curved generatrix part with spiral internal ribs. Background Art

[0002] After decades of development, spin forming technology is currently playing an increasingly important role in the near-net forming of thin-walled, complex-shaped, and lightweight integral components. Large complex curved generatrix thin-walled components are a type of parts commonly used in the aerospace and ordnance industries, such as aircraft engine covers, integral rocket engine components, compressor cones, and liner cones in the ordnance industry. With the development of high-tech industries such as aerospace, it is required to improve the strength and stiffness of such parts without affecting the external aerodynamic performance, so as to optimize the overall performance of aircraft, rockets, missiles, etc. For this purpose, it is necessary to design reinforcing internal ribs inside these parts. Among them, the structure with spiral reinforcing internal ribs is a typical representative. However, this complex curved generatrix thin-walled structure with spiral internal ribs poses a great challenge to the design of the forming core mold structure for large components.

[0003] Northwestern Polytechnical University disclosed a mandrel for spinning parts with spiral internal ribs and a demolding method in the invention creation with the application number 201811188626.4, which is mainly used for the spinning forming and demolding of large thin-walled cylindrical parts with spiral ribs. Since the cross-section of the spiral rib is an isosceles trapezoid, the mandrel can move radially along the cylindrical part and be separated radially during demolding. However, for thin-walled curved generatrix parts with spiral internal ribs, since the cross-section of the internal rib is semi-circular and the diameter of the internal rib is different at different cross-sections, it is impossible to demold by moving radially and axially along the workpiece. At the same time, this device is designed for the spinning forming of cylindrical parts and is not suitable for the spinning forming of large thin-walled curved generatrix parts. Northwestern Polytechnical University disclosed a spinning mandrel for large complex curved generatrix thin-walled components with transverse internal ribs in the invention creation with the application number 201010535565.1. Northwestern Polytechnical University disclosed a mandrel for spinning parts with transverse internal ribs and a forward demolding method in the invention creation with the application number 201110154935.1; Northwestern Polytechnical University disclosed a mandrel for spinning parts with transverse internal ribs and a backward demolding method in the invention creation with the application number 201110154980.7; Northwestern Polytechnical University disclosed a mandrel for spinning parts with transverse internal ribs and a demolding method in the invention creation with the application number 201110310989.2. In the above-mentioned invention creations, they all focus on how to demold the thin-walled curved generatrix components with transverse internal ribs. At the mandrel corresponding to the transverse internal rib section, a detachable clamping plate is composed of multiple shorter clamping blocks. After the clamping plate is disassembled, it can ensure that the spinning part with transverse internal ribs is taken out from the spinning mandrel. However, the above-mentioned inventions all aim at thin-walled curved generatrix components with transverse internal ribs. Compared with the spinning part with transverse internal ribs, for the spinning part with spiral internal ribs, since the internal rib is distributed in a spiral on the inner surface of the workpiece, the detachable part of the mandrel cannot rotate circumferentially like the clamping block in the above-mentioned existing inventions to demold; at the same time, the above-mentioned inventions are only applicable to the demolding of spinning parts with local shorter transverse internal ribs, and the clamping blocks should not be too long. The internal ribs of the spinning part with spiral internal ribs are distributed axially almost throughout the length of the workpiece, resulting in the inapplicability of the existing mandrel design and demolding method. Therefore, there is an urgent need for a spinning mandrel for large thin-walled curved generatrix components with spiral internal ribs that can realize the rapid installation and demolding of the mold, and can realize the rapid demolding of the workpiece without removing the main mandrel from the machine tool. Summary of the Invention

[0004] To solve the problem that the mandrel structure in the prior art cannot meet the requirements of spinning forming and demolding difficulties of thin-walled curved generatrix components with spiral internal ribs, the present invention proposes a design and demolding method for a split mandrel for spinning thin-walled curved generatrix parts with spiral internal ribs.

[0005] The core die for the spinning of the part with spiral internal ribs proposed by the present invention comprises a main core die, a split core die and a clamping block. Among them: the split core die is sleeved on the outer circumferential surface of the main core die, and the end face of the tail end of the split core die is attached to the bottom surface of the main core die; the clamping block is sleeved on the outer circumferential surface of the end face of the tail end of the split core die and is attached to the bottom surface of the main core die.

[0006] There is a threaded hole at the center of the end face of the head of the main core die body. When the workpiece is clamped, the workpiece, the split core die and the main core die body can be connected together by bolts. The outer circumferential surface of the base of the main core die body is evenly distributed with convex keys, which can form a clearance fit with the key grooves on the inner circumferential surface of the tail end of the split core die. There is a circular groove at the center of the bottom surface of the main core die body, and there are evenly distributed connecting holes around the circular groove, so that a chuck for connecting the main core die with the spinning machine is formed at this end.

[0007] The split core die is composed of 2 active core die segments and 2 passive core die segments. The outer diameter of the split core die is the same as the maximum diameter of the inner surface of the workpiece; the inner surfaces of the passive core die segments are evenly distributed with axial key grooves; the inner surface of the split core die and the outer surface of the main core die are in clearance fit.

[0008] The outer circumferential surface of the split core die is evenly distributed with spiral grooves, and the starting point of the spiral groove is 20 mm away from the end face of the head of the split core die, and the ending point is 10 mm away from the end face of the tail of the split core die; the spiral groove starts to rotate clockwise along the spiral line direction, and the cross-section of the spiral groove gradually increases from a semi-circular cross-section with a diameter of 8 mm at the starting point to a semi-circular cross-section with a diameter of 20 mm at the ending point, and the depth of the whole spiral groove shows a gradually deepening state.

[0009] The active core die segment and the passive core die segment of the split core die are combined into an end face with a round hole at the end face of the head of the split core die. The diameter of the round hole and the maximum displacement of the split core die along the radial direction should be greater than the maximum depth of the rib groove of the split core die to ensure that the split core die can be taken out smoothly after the workpiece is processed.

[0010] When the active core die segment and the passive core die segment are combined into the split core die, the active core die segment and the passive core die segment are arranged at intervals. Looking from the end face of the head of the split core die, the inner surface and the outer surface of the active core die segment are both arc surfaces, and the two sides are parallel and equal, so that the chord length of the inner arc of the active core die segment is equal to the chord length of the outer arc.

[0011] Looking from the end face of the head of the split core die, the cross-section of each passive core die segment is fan-shaped, and its inner surface and outer surface are both arc surfaces; the angles of the two sides of each passive core die segment need to meet the following requirements: the extension lines of the two sides of each passive die segment form an included angle of 180°.

[0012] There are two clamping blocks. The inner surface of the clamping block is an arc surface that fits the outer surface of the split core mold. There is a convex block with a threaded hole at both ends of the clamping block, which facilitates the fastening connection of the two clamping blocks through bolts.

[0013] The demoulding process of the core mold for spinning the component with spiral internal ribs proposed by the present invention is as follows:

[0014] Step 1: Loosen and withdraw the tailstock of the spinning machine tool, remove the fastening bolts connecting the two clamping blocks, and take out the two clamping blocks.

[0015] Step 2: Remove the fastening bolts at the end face of the head of the main core mold, move the split core mold and the workpiece as a whole axially towards the direction of the tailstock of the machine tool, and take them out and place them on the support frame.

[0016] Step 3: The first active core mold segment first translates along the center direction of the inner circumferential surface at the tail of the split core mold so that the spiral groove on the outer surface of the split core mold is separated from the spiral rib on the inner surface of the workpiece, and then the active core mold segment is taken out along the axis of the split core mold; similarly, the second active core mold segment is taken out.

[0017] Step 4: After taking out all the active core mold segments, the first passive core mold segment first translates along the center direction of the inner circumferential surface at the tail of the split core mold so that the spiral groove on the outer surface of the split core mold is separated from the spiral internal rib on the inner surface of the workpiece, and then the first passive core mold segment is taken out along the axis of the split core mold; similarly, the second passive core mold segment is taken out.

[0018] Through the above steps, the problem that the component with spiral internal ribs and large thin-walled curved generatrix cannot be demoulded after spinning forming can be satisfactorily solved.

[0019] Since the split core mold in the present invention is a hollow shell and the circumferential uniform splitting and key connection technology is adopted for it, and a demoulding space is reserved at both ends of the split core mold, the installation of the spinning forming mold for the component with spiral internal ribs and large thin-walled curved generatrix and the demoulding of the workpiece can be conveniently realized; the main core mold and the split core mold adopt the key connection technology, which greatly reduces the difficulty of installation and disassembly of the split core mold; because a demoulding space is reserved at both ends of the split core mold, the split core mold and the workpiece can be taken out together from the main core mold and then the workpiece is demoulded, avoiding the influence on the accuracy of the machine tool during demoulding on the spinning machine tool; the main core mold is installed on the spinning machine tool and does not need to be reinstalled or disassembled during the subsequent workpiece demoulding and mold installation processes, reducing the labor intensity of workers and shortening the production cycle of the workpiece and improving the production efficiency. Brief Description of the Drawings

[0020] Figure 1 is the structural schematic diagram of the present invention;

[0021] Figure 2 is the cross-sectional view of the main core mold;

[0022] Figure 3 is the front view of the first active core die lobe;

[0023] Figure 4 is the front view of the first passive core die lobe;

[0024] Figure 5 is the top view of the split core die;

[0025] Figure 6 is the schematic diagram of the clamping block; wherein:

[0026] 1. Main core die; 2. Split core die; 3. Clamping block; 4. Main core die body; 5. Convex key; 6. Spiral groove; 7. First active core die lobe; 8. First passive core die lobe; 9. Second active core die lobe; 10. Second passive core die lobe; 11. Keyway. Specific implementation mode

[0027] This embodiment is a combined split die used in the spinning forming of large and complex curved generatrix thin-walled components with spiral internal ribs. This embodiment includes a main core die 1, a split core die 2, and a clamping block 3. Wherein: The split core die 2 is sleeved on the circumferential surface of the core die body of the main core die 1, and the end face of the tail end of the split core die is attached to the bottom surface of the main core die; The clamping block 3 is sleeved on the outer circumferential surface of the tail end of the split core die and the two clamping blocks are connected with fastening bolts. In this embodiment, there are three spiral grooves 6 on the outer circumferential surface of the core die body of the split core die 2, and the starting point of the spiral groove is 20 mm away from the head end face of the split core die, and the ending point is 10 mm away from the tail end face of the split core die; The cross-section of the three spiral grooves gradually changes from a semi-circular cross-section with a diameter of 8 mm to a semi-circular cross-section with a diameter of 20 mm, and the pitch of every two adjacent spiral lines starting from the starting point is 15 mm and 20 mm respectively.

[0028] The outer circumferential surface of the base of the main core die body is evenly distributed with convex keys for cooperating with the passive core die lobes. There is a groove for cooperating with the machine tool spindle at the center of the bottom surface of the main core die body; A plurality of threaded holes are evenly distributed around the groove for fixedly connecting the main core die with the machine tool spindle. There is a threaded hole at the center of the head end face of the main core die body, and the workpiece, the split core die and the main core die can be fixedly connected through bolts.

[0029] The split core die is an elliptical shell and is composed of a first active core die lobe, a second active core die lobe,..., an m-th active core die lobe and a first passive core die lobe, a second passive core die lobe,..., an n-th passive core die lobe. In this embodiment, m = n = 2, and there are a total of 4 core die lobes.

[0030] The outer diameter of the split core die is the same as the maximum diameter of the inner surface of the workpiece; And there is a clearance fit between the 6 axial keyways evenly distributed on the inner circumferential surface of the tail end of the split core die and the 6 axial convex keys evenly distributed on the outer circumferential surface of the base of the main core die.

[0031] The four core die segments are as follows Figure 5 shown, where two of the core die segments are active core die segments, namely the first active core die segment 7 and the second active core die segment 9; the other two core die segments are passive core die segments, namely the first passive core die segment 8 and the second passive core die segment 10. When combined, the active core die segments and the passive core die segments are arranged at intervals.

[0032] The structures of the active core die segments are the same. In this embodiment, the first active core die segment 7 is taken as an example for description.

[0033] At the end cross-section of the first active core die segment 7, both the inner surface and the outer surface are arc surfaces, and the two side surfaces are parallel and equal, so that the chord length of the inner arc at the end cross-section of the first active core die segment is equal to the chord length of the outer arc.

[0034] The structures of the passive core die segments are the same. In this embodiment, the first passive core die segment 8 is taken as an example for description.

[0035] The cross-section at the end of the first passive core die segment is fan-shaped, and both its inner surface and outer surface are arc surfaces; the angles of the two side edges need to meet the following requirements: the extension lines of the two sides of the first passive die segment form an included angle of 180°.

[0036] There are two clamping blocks. The inner surface of the clamping block is an arc surface that fits the outer surface of the split core die. There is a convex block with a threaded hole at both ends of the clamping block, so that the two clamping blocks can be firmly connected by bolts.

[0037] This embodiment is a demolding method using the spinning core die

[0038] During the spinning forming process, the workpiece, the split die and the main core die are firmly connected by tightening bolts and then fixed by the tailstock. Under the action of the spinning wheel, the thickness of the workpiece is reduced and increased, and at the same time, a part of the material is filled into the spiral groove 6 of the split core die 2. After the spinning forming is completed, the ribs of the thin-walled curved generatrix workpiece with spiral internal ribs are stuck in the spiral groove of the split core die 2.

[0039] The specific steps for demolding the workpiece are as follows

[0040] Step 1: Loosen and withdraw the tailstock of the spinning machine tool, remove the tightening bolts connecting the two clamping blocks 4, and take out the two clamping blocks 4.

[0041] Step 2: Remove the tightening bolts, and move the split core die and the workpiece as a whole along the axial direction of the tailstock of the machine tool and take them out.

[0042] Step 3: Translate the 2 active split dies along the direction of the center of the inner circumferential surface at the tail of the split core die in turn, so that the spiral groove on the outer surface of the split core die is separated from the spiral rib on the inner surface of the workpiece, and then translate along the axial direction of the split core die to take out the active die segment.

[0043] Step 4: After all the active valve core molds are completely removed, two passive split core molds will be sequentially translated along the center direction of the inner circumferential surface at the tail of the split core mold so that the spiral grooves on the outer surface of the split core mold are separated from the spiral ribs on the inner surface of the workpiece. After all the passive core mold segments are taken out, the workpiece can be smoothly demolded.

Claims

1. A mandrel for spinning with a spiral inner rib member, comprising a main mandrel, a split mandrel and a clamping block; wherein: The split mandrel is sleeved on the outer circumferential surface of the main mandrel, and the end face of the tail end of the split mandrel is fitted with the surface of the main mandrel base; the clamping block is sleeved on the outer circumferential surface of the tail end of the split mandrel; the end face of the head of the split mandrel is connected to the main mandrel body by bolts; the split mandrel is composed of m active mandrel segments and n passive mandrel segments; the outer diameter of the split mandrel is the same as the maximum diameter of the inner surface of the workpiece; the inner surfaces of the active mandrel segments and the passive mandrel segments both have axial key grooves; there is a clearance fit between the inner surface of the split mandrel and the outer surface of the main mandrel; m = n = 4.

2. The core die for spinning with a spiral internal rib member as claimed in claim 1, wherein: The outer circumferential surface of the split mandrel is evenly distributed with spiral grooves, and the starting point of the spiral groove is 20 mm away from the end face of the head of the split mandrel, and the ending point is 10 mm away from the end face of the tail of the split mandrel; the spiral groove starts to rotate clockwise along the spiral line direction, and the cross-section of the spiral groove gradually increases from a semi-circular cross-section with a diameter of 8 mm at the starting point to a semi-circular cross-section with a diameter of 20 mm at the ending point, and the depth of the whole spiral groove shows a gradually deepening state.

3. The spinning mandrel with a spiral internal rib member as claimed in claim 1, wherein: When the active mandrel segments and the passive mandrel segments are combined into a split mandrel, the active mandrel segments and the passive mandrel segments are arranged at intervals. Looking from the end face of the head of the split mandrel, both the inner surface and the outer surface of the active mandrel segment are arc surfaces, and the two sides are parallel and equal, so that the chord length of the inner arc of the active mandrel segment is equal to the chord length of the outer arc; the cross-section of each passive mandrel segment is fan-shaped, and both its inner surface and outer surface are arc surfaces; The angles of the two sides of each passive mandrel segment need to meet the following requirements: the extension lines of the two sides of each passive mandrel segment form an included angle of 180°.

4. The mandrel for spinning with a spiral internal rib member as claimed in claim 1, wherein: The outer circumferential surface of the base of the main mandrel body is evenly distributed with convex keys that cooperate with the passive mandrel segments; there is a groove in the center of the bottom surface of the main mandrel body that cooperates with the machine tool spindle; a plurality of threaded holes are evenly distributed around the groove for fixing the main mandrel to the machine tool spindle; there is a threaded hole in the center of the end face of the head of the main mandrel body, and the workpiece, the split mandrel and the main mandrel can be firmly connected by bolts.

5. The mandrel for spinning with a spiral internal rib member as described in claim 1, characterized in that: There are two clamping blocks, the inner surface of the clamping block is an arc surface that fits the outer surface of the split mandrel, and there is a convex block with a threaded hole at both ends of the clamping block, and the two clamping blocks are firmly connected to the outer surface of the split mandrel by bolts.

6. The core die for spinning with a spiral internal rib member as described in claim 2, wherein: There are three spiral grooves on the outer circumferential surface of the mandrel body of the split mandrel, the cross-section of the spiral groove is semi-circular, and the depth of the spiral groove gradually increases from 8 mm to 20 mm along the spiral line direction; the pitch of each adjacent two spiral lines starting from the starting point is 15 mm and 20 mm respectively.

7. A demolding method using the core mold for spinning with the spiral inner rib member described in claim 1, characterized in that, The specific steps are as follows: Step 1, loosen and withdraw the tailstock of the spinning machine tool, remove the fastening bolts connecting the two clamping blocks and take out the two clamping blocks; Step 2, remove the fastening bolts on the end face of the head of the main mandrel, move the split mandrel and the workpiece as a whole axially in the direction of the tailstock of the machine tool and take them out and place them on the support frame; Step 3, the first active mandrel segment first translates along the center direction of the inner circumferential surface of the tail of the split mandrel so that the spiral groove on the outer surface of the split mandrel is separated from the spiral rib on the inner surface of the workpiece, and then take out the active mandrel segment along the axis of the split mandrel; similarly take out the second active mandrel segment; Step 4, after all the active petal core molds are taken out, the first passive petal core mold is first translated along the center direction of the inner circumference of the tail of the petal core mold so that the spiral groove on the outer surface of the petal core mold is separated from the spiral inner ribs on the inner surface of the workpiece, and then the first passive core mold petal is taken out along the axial direction of the petal core mold, and the second passive core mold petal is taken out similarly, and the workpiece is successfully demolded.

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