Variable-diameter inner half pipe curved surface multi-point positioning clamping numerical control milling clamp

Abstract

The invention discloses a variable-diameter inner half pipe curved surface multi-point positioning clamping numerical control milling clamp which comprises a small-end positioning plate and a large-end positioning plate which are obliquely arranged, and the surfaces where the small-end positioning plate and the large-end positioning plate are located are perpendicular to each other; small-end adjustable clamping plates capable of moving in the inclination direction of the small-end positioning plate are arranged on the two sides of the small-end positioning plate, large-end adjustable clamping plates capable of moving in the inclination direction of the large-end positioning plate are arranged on the two sides of the large-end positioning plate, and a fixed clamping plate is arranged at the position, close to the edge of the small-end positioning plate, of the center of the large-end positioning plate. Wherein the small end positioning plate is used for placing a small end of an inner half pipe blank; the large end positioning plate is used for placing the large end of the inner half pipe blank; the small-end adjustable clamping plate is used for clamping the small end of the inner half pipe blank, the large-end adjustable clamping plate is used for clamping the large end of the inner half pipe blank, and the fixed clamping plate is used for clamping the inner wall of the top of the large end of the inner half pipe blank. The problems that in the prior art, an inner half pipe machining clamp is difficult to adapt to blanks in different states, and time and labor are consumed in the clamping process are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerospace machining, and particularly relates to a numerically controlled milling fixture for multi-point positioning and clamping of a variable-diameter inner semi-tube curved surface.

Background Art

[0002] The gas inner semi-tube is an important structural component in an aerospace liquid rocket engine. It is used in a harsh environment and is made of a superalloy material. Its blank is forged from a sheet material with a thickness of 17 mm, with low precision and poor consistency. There are no accurate features available as positioning references. After machining and forming, the thinnest part of the part is only 6 mm, and the heat treatment states of different batches of sheet materials vary greatly. The residual stress inside the blank is uneven, resulting in a large difference between the blank and the model. This poses high requirements for subsequent part curved surface machining. Relying solely on three profiling clamping plates for positioning and clamping cannot meet the requirements of precise and efficient machining. During machining, a fixture is needed to ensure that the semi-tube is in the correct position and clamped, preventing position changes and workpiece deformation caused by fixture loosening due to cutting force and vibration during the machining process. The semi-tube machining fixtures in the prior art generally have difficulty adapting to blanks in different states, and the clamping process is time-consuming and laborious, making it difficult to meet the actual machining requirements and affecting the bending pipe machining efficiency and machining quality. Due to the weight of the inner semi-tube blank being about 20 kg, small size, and large wall thickness, the loading, unloading, and scribing processes in conventional numerically controlled milling are complex. Moreover, the edges of the large end and small end are rough edges after cutting, causing difficulties in clamping. This also increases the labor intensity, safety risks, rejection rate, and non-conforming rate of the parts.

Summary of the Invention

[0003] The purpose of the present invention is to provide a numerically controlled milling fixture for multi-point positioning and clamping of a variable-diameter inner semi-tube curved surface to solve the problems that the inner semi-tube machining fixtures in the prior art are difficult to adapt to blanks in different states, cannot guarantee the positioning accuracy, and have a large cutting resistance for the clamped blank.

[0004] The present invention adopts the following technical solutions: A numerically controlled milling fixture for multi-point positioning and clamping of a variable-diameter inner semi-tube curved surface, based on an inner semi-tube blank, and the two ends of the inner semi-tube blank are divided into a large end and a small end according to the size of the opening;

[0005] The machining fixture includes: a small-end positioning plate and a large-end positioning plate that are inclined. The extension lines of the two intersect to form an inverted V shape. Both the small-end positioning plate and the large-end positioning plate are polygonal plate structures, and the shape of the polygonal structure matches the inner wall shape of the corresponding large end or small end of the inner semi-tube blank. The planes where the small-end positioning plate and the large-end positioning plate are located are perpendicular to each other;

[0006] On both sides of the top surface of the small-end positioning plate, there are small-end adjustable clamping plates that can move along its inclined direction. On both sides of the top surface of the large-end positioning plate, there are large-end adjustable clamping plates that can move along its inclined direction. Near the edge of the small-end positioning plate at the center of the top surface of the large-end positioning plate, there is a fixed clamping plate;

[0007] Among them, the small end of the inner half pipe blank is placed on the small end positioning plate, and the small end positioning plate is parallel to the surface where the small end of the inner half pipe blank is located; the large end of the inner half pipe blank is placed on the large end positioning plate, and the large end positioning plate is parallel to the surface where the large end of the inner half pipe blank is located; the small end adjustable clamping plate is used to clamp the inner walls on both sides of the small end of the inner half pipe blank, the large end adjustable clamping plate is used to clamp the inner walls on both sides of the large end of the inner half pipe blank, and the fixed clamping plate is used to clamp the top inner wall of the large end of the inner half pipe blank.

[0008] Furthermore, each small end adjustable clamping plate includes: a small end adjustable support block, the small end adjustable support block is connected to the waist-shaped hole on the small end positioning plate through a bolt, and the extending direction of the waist-shaped hole is the same as the extending direction of the small end positioning plate; it also includes a small end adjustable support block pressing plate, the small end adjustable support block pressing plate is detachably connected to the small end adjustable support block through a bolt and is used to clamp the outer wall of the inner half pipe blank; the surfaces of the small end support plate and the small end adjustable support block that are in contact with the inner half pipe blank are both profiling surfaces of the theoretical model.

[0009] Furthermore, each large end adjustable clamping plate includes: a large end adjustable support block, the large end adjustable support block is connected to the waist-shaped hole on the large end positioning plate through a bolt, and the extending direction of the waist-shaped hole is the same as the extending direction of the large end positioning plate; it also includes a large end adjustable support block pressing plate, the large end adjustable support block pressing plate is detachably connected to the large end adjustable support block through a bolt and is used to clamp the outer wall of the inner half pipe blank; the surfaces of the large end adjustable support block pressing plate and the large end adjustable support block that are in contact with the inner half pipe blank are both profiling surfaces of the theoretical model.

[0010] Furthermore, the fixed clamping plate includes a large end fixed support block, the large end fixed support block is fixedly connected to the center of the top surface of the large end positioning plate near the edge of the small end positioning plate; it also includes a large end fixed support block pressing plate, the large end fixed support block pressing plate is detachably connected to the large end fixed support block through a bolt and is used to clamp the outer wall of the inner half pipe blank; the surfaces of the large end fixed support block pressing plate and the large end fixed support block that are in contact with the inner half pipe blank are both profiling surfaces of the theoretical model.

[0011] Furthermore, a cam connection column mounting block is arranged below the connecting plate, and a cam connection column is arranged through the cam connection column mounting block; the axis direction of the cam connection column is perpendicular to the extending direction of the connecting plate, and cams are connected to both ends of the cam connection column; it is used to rotate following the rotation of the cam connection column to contact the side wall of the inner half pipe blank and complete the leveling of the inner half pipe blank.

[0012] Further, the bottoms of the small-end positioning plate and the large-end positioning plate are connected to an H-shaped support frame. The H-shaped support frame includes a small-end support plate connected to the small-end positioning plate and vertically arranged, a large-end support plate connected to the large-end positioning plate and vertically arranged, and a connecting plate connected between the small-end support plate and the large-end support plate.

[0013] Further, it also includes two springs, and both ends of each spring are connected between the cam and the connecting plate.

[0014] The beneficial effects of the present invention are as follows: In order to greatly improve the processing quality and efficiency of the gas bend pipe, eliminate the problems of difficult numerical control processing and easy out-of-tolerance of large curved surface parts made of superalloy caused by poor consistency of the forging quality of the bend pipe blank, shorten the part processing cycle, reduce the part processing cost, and reduce the labor intensity of the operator, the present invention provides a design method for a processing fixture for the inner half pipe. This fixture design method adapts to the structural dimension characteristics of the part and combines adjustable support design, greatly eliminating the deformation after the inner half pipe is processed.

[0015] The positioning method of the present invention is to accurately position the inner half pipe blank through the process reference line, and the clamping of the large end and the small end is realized by the profiling pressing mechanism adapting to the size change of the blank. The rigidity enhancement device of the present invention includes a cam connecting column, a cam and a spring, and dynamically adjusts the intermediate area support through the rigidity enhancement device to suppress processing vibration. The auxiliary device of the present invention includes a cam connecting column mounting block and a connecting plate, and realizes the rapid connection and rigidity strengthening of the fixture and the blank through the auxiliary device.

[0016] When processing the inner gas bend pipe blank of medium and large-sized free-form surfaces in the aerospace field, using the new numerical control milling machine tooling fixture structure of the present invention, draw corresponding 0° reference line and 90° reference line in the inner half pipe large end and small end marking design drawing, select them as the process reference lines, and perform multi-point positioning on the inner half pipe blank with reference to their positions, that is, use multiple clamping blocks at both ends and use a cam connected by a spring on the side for floating positioning.

[0017] Advantages of using multi-point positioning:

[0018] First, due to the dimensional errors brought by springback and thermal expansion and contraction during the forging process of the blank, the forming accuracy of the inner half pipe blank is poor. The deviation between the actual blank and the theoretical model may exceed 5 mm. Even blanks of the same batch have different shapes and show personalized dimensional states, which is the main reason for easy out-of-tolerance in processing. By using multi-point positioning, the adjustable clamping blocks at both ends can be adjusted according to the actual state of the blank, and the cam and the spring can also support side floating, thus ensuring the clamping of blanks in different states.

[0019] Second, the span between the two end faces of the workpiece is relatively large, and the part is prone to deformation during cutting. By positioning at both ends, the system rigidity can be improved to resist stress deformation. Moreover, the finished product has a variable wall thickness structure, so the material removal amounts in different machining areas are different. The cutting resistance is large at the part with a large material removal amount. By using multi-point positioning, the floating of the cam and the spring can overcome the cutting resistance during machining. Combining with positioning at both ends can suppress the vibration of the workpiece, avoid displacement, and ensure product quality.

[0020] Position the inner half-tube blank with reference to its position. Positioning at both ends has two advantages: First, the span between the two positioning references is long, and the positioning accuracy is high, which can meet the machining accuracy requirements of the part. Second, by positioning at both ends, the system rigidity is high, the machining process is stable, and supports can be added in the middle to improve the system rigidity, which can effectively solve the problems of low machining efficiency and out-of-tolerance of the workpiece, and greatly shorten the machining cycle of the medium-sized inner half-tube.

Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a numerically controlled milling fixture for multi-point positioning and clamping of the variable-diameter inner half-tube curved surface of the present invention;

[0022] Figure 2 It is a three-dimensional structural diagram of a numerically controlled milling fixture for multi-point positioning and clamping of the variable-diameter inner half-tube curved surface of the present invention from one perspective;

[0023] Figure 3 It is a three-dimensional structural diagram of a numerically controlled milling fixture for multi-point positioning and clamping of the variable-diameter inner half-tube curved surface of the present invention from another perspective;

[0024] Figure 4 It is a schematic diagram of the installation relationship between a numerically controlled milling fixture for multi-point positioning and clamping of the variable-diameter inner half-tube curved surface of the present invention and the inner half-tube blank;

[0025] Figure 5 It is a schematic diagram of the reference line of the inner half-tube blank of the present invention.

[0026] Among them, 1. Small-end positioning plate, 2. Small-end support plate, 3. Connecting plate, 4. Bottom plate, 5. Small-end adjustable support block pressing plate, 6. Small-end adjustable support block, 7. Cam connecting column mounting block, 8. Cam connecting column, 9. Cam, 10. Large-end adjustable support block pressing plate, 11. Large-end adjustable support block, 12. Large-end support plate, 13. Large-end positioning plate, 14. Large-end fixed support block, 15. Large-end fixed support block pressing plate, 16. Spring, 17. Inner half-tube blank.

Detailed Description of the Invention

[0027] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0028] The gas elbow is used as a gas pipeline for an engine. The diameters at both ends are different. The end with a larger diameter is the large end, and the end with a smaller diameter is the small end. The plane where the large end is located and the plane where the small end is located are perpendicular to each other. The gas elbow blank is divided into two parts along its axis to obtain an inner half-pipe blank and an outer half-pipe blank. The processed inner half-pipe and outer half-pipe are finally welded together to form an integral gas elbow.

[0029] For the inner half-pipe, its bending radius is R, and the bending radius is the radius of the circle where the intersecting edge of the inner half-pipe and the outer half-pipe is located. Based on the inner half-pipe, the present invention proposes a variable-diameter inner half-pipe surface multi-point positioning clamping numerical control milling fixture. Based on an inner half-pipe blank 17, the tooling of the present invention is dedicated to a specific pipe. Before designing the tooling, it will be matched and designed according to the various dimensions of the inner half-pipe blank 17.

[0030] As Figure 1 shown, the machining fixture includes: a small-end positioning plate 1 and a large-end positioning plate 13 which are inclined. The extension lines of the two intersect to form an inverted V shape. Both the small-end positioning plate 1 and the large-end positioning plate 13 are polygonal plate structures, and the shape of the polygonal structure matches the inner wall shape of the large end or small end of the corresponding inner half-pipe blank 17, so as to better support and position the large end or small end; the planes where the small-end positioning plate 1 and the large-end positioning plate 13 are located are perpendicular to each other.

[0031] The distance between the small-end positioning plate 1 and the large-end positioning plate 13 is adjusted according to the bending radius R of the inner half-pipe. For the selection of the distance, after the small end of the inner half-pipe blank is placed on the small-end positioning plate 1, the inclined plane where the small-end positioning plate 1 is located should coincide with the inclined plane where the 0° reference line of the theoretical model is located, and at the same time, the inclined plane where the large-end positioning plate 13 is located should coincide with the inclined plane where the 90° reference line of the theoretical model is located. Among them, the 0° reference line and the 90° reference line of the theoretical model of the inner half-pipe blank are as Figure 5 shown. The 0° reference line is located at 20 ± 1 mm near the small-end edge, and the 90° reference line is located at 20 ± 1 mm near the large-end edge.

[0032] On both sides of the top surface of the small-end positioning plate 1, there are small-end adjustable clamping plates that can move along its inclined direction. On both sides of the top surface of the large-end positioning plate 13, there are large-end adjustable clamping plates that can move along its inclined direction. Near the edge of the large-end positioning plate 13 close to the small-end positioning plate 1 at the center of the top surface, there is a fixed clamping plate. The small-end adjustable clamping plate is used to clamp the inner walls on both sides of the small end of the inner half-pipe blank 17, the large-end adjustable clamping plate is used to clamp the inner walls on both sides of the large end of the inner half-pipe blank 17, and the fixed clamping plate is used to clamp the inner wall at the top of the large end of the inner half-pipe blank 17.

[0033] In some embodiments, as Figure 2As shown, each small-end adjustable clamping plate includes: a small-end adjustable support block 6, which is connected to the waist-shaped hole on the small-end positioning plate 1 by bolts. The extending direction of the waist-shaped hole is the same as that of the small-end positioning plate 1. By moving in the waist-shaped hole, for example, a stroke adjustment of ±5 mm can be achieved; it also includes a small-end adjustable support block pressing plate 5, which is detachably connected to the small-end adjustable support block 6 by bolts and is used to clamp the outer wall of the inner half-tube blank 17; the pressing force generated between the two is perpendicular to the axis of the inner half-tube blank 17; the surfaces of the small-end support plate 2 and the small-end adjustable support block 6 that contact the inner half-tube blank 17 are both profiling surfaces of the theoretical model. The profiling surface mentioned in the present invention refers to a curved surface used to simulate or approximate the actual surface shape of the corresponding position of the inner half-tube blank.

[0034] In some embodiments, as Figure 3 shown, each large-end adjustable clamping plate includes: a large-end adjustable support block 11, which is connected to the waist-shaped hole on the large-end positioning plate 13 by bolts. The extending direction of the waist-shaped hole is the same as that of the large-end positioning plate 13. By moving in the waist-shaped hole, for example, a stroke adjustment of ±5 mm can be achieved; it also includes a large-end adjustable support block pressing plate 10, which is detachably connected to the large-end adjustable support block 11 by bolts and is used to clamp the outer wall of the inner half-tube blank 17; the pressing force generated between the two is perpendicular to the axis of the inner half-tube blank 17; the surfaces of the large-end adjustable support block pressing plate 10 and the large-end adjustable support block 11 that contact the inner half-tube blank 17 are both profiling surfaces of the theoretical model.

[0035] In some embodiments, the fixed clamping plate includes a large-end fixed support block 14, which is fixedly connected to the center of the top surface of the large-end positioning plate 13 near the edge of the small-end positioning plate 1; it also includes a large-end fixed support block pressing plate 15, which is detachably connected to the large-end fixed support block 14 by bolts and is used to clamp the outer wall of the inner half-tube blank 17; the surfaces of the large-end fixed support block pressing plate 15 and the large-end fixed support block 14 that contact the inner half-tube blank 17 are both profiling surfaces of the theoretical model.

[0036] In some embodiments, a cam connection column mounting block 7 is provided below the connecting plate 3. A cam connection column 8 passes through the cam connection column mounting block 7. The cam connection column mounting block 7 is provided with a clearance fit hole, allowing the cam connection column 8 to rotate freely and be axially fixed; the axis direction of the cam connection column 8 is perpendicular to the extending direction of the connecting plate 3. Both ends of the cam connection column 8 are connected with cams 9; the contour of the cam 9 is involute, which is used to rotate following the rotation of the cam connection column 8 to contact the side wall of the inner half-tube blank 17. Adjusting to make both sides contact the cam 9 realizes the leveling of the inner half-tube blank 17.

[0037] In some embodiments, the bottoms of the small-end positioning plate 1 and the large-end positioning plate 13 are connected to an H-shaped support frame, which includes a small-end support plate 2 that is vertically arranged and connected to the small-end positioning plate 1, a large-end support plate 12 that is vertically arranged and connected to the large-end positioning plate 13, and a connecting plate 3 connected between the small-end support plate 2 and the large-end support plate 12.

[0038] In some embodiments, there are also two springs 16. Both ends of each spring 16 are connected by screws between the cam 9 and the connecting plate 3, which helps to align the semi-finished blank and reduce the chatter between the cutting tool and the workpiece during machining.

[0039] In the present invention, according to the precise dimensions of the pre-machined inner half-tube, the dimensions and positions of the various components of a variable-diameter inner half-tube curved surface multi-point positioning and clamping CNC milling fixture of the present invention are designed, and a machining fixture is made according to these dimensions. Then, the machining fixture is used to fix the inner half-tube blank to be machined to complete subsequent precision CNC machining. The usage method of a variable-diameter inner half-tube curved surface multi-point positioning and clamping CNC milling fixture of the present invention specifically includes the following content:

[0040] Refer to Figure 1 , first, the large-end support plate 12 and the small-end support plate 2 are positioned by pins and connected by screws, and are respectively installed at both ends of the bottom plate 4; the connecting plate 3 is installed between the large-end support plate 12 and the small-end support plate 2, positioned by pins and connected by screws; the cam connecting column mounting block 7 is installed at the front end of the connecting plate 3; the corresponding large-end support plate 12, large-end adjustable support block 11, large-end adjustable support block pressing plate 12, large-end fixed support block 14, large-end fixed support block pressing plate 15 and screws are installed on the large-end positioning plate 13; the corresponding small-end support plate 2, small-end adjustable support block 6, small-end adjustable support block pressing plate 5 and screws are installed on the small-end positioning plate 1; the cam connecting column mounting block 7 is installed on the connecting plate 3; the cam connecting column 8 is inserted into the round hole in the cam connecting column mounting block 7; the cams 9 are installed on both sides of the cam connecting column and leveled to align the two cams; the springs 16 are installed and tightened to pull the cams.

[0041] During use, assemble the fixture as described above.

[0042] Fix the bottom plate 4 to the CNC machine tool workbench by bolts, loosen the screws of each positioning block pressing plate and the set screws of the adjustable positioning block. After placing the bent tube blank at the corresponding position on the fixture, finely adjust the position. As Figure 4 and Figure 5 shown, align the 0° reference line of the inner half-tube blank with the upper surface of the small-end positioning plate 1, and align the 90° reference line with the upper surface of the large-end positioning plate 13, and make both side cams contact the blank groove, so as to achieve horizontal alignment of the half-tube workpiece;

[0043] Then adjust the positions of the adjustable support blocks on both sides to ensure good contact between each support block and the blank. Push the blank to make the profiling surface of the fixed support block 11 at the large end of its inner wall fit. Adjust the waist-shaped hole fixing screws of the adjustable support block 6 at the small end and the adjustable support block 11 at the large end. Slide the support blocks along the fixed small-end positioning plate 1 and the large-end positioning plate 13 to the contact position with the inner wall of the blank. Rotate the thread pair of the adjustable support block to finely adjust its extension amount, and lock the waist-shaped hole screws to ensure that the support blocks have no displacement. Install the pressing plates 5 for the adjustable support blocks at the small end and the pressing plates 10 for the adjustable support blocks at the large end in sequence and tighten the pressing plate screws.

[0044] Fine-tune the blank through the involute profile to level the two cams. After the machining is completed, loosen the locking screws of the pressing plates 5 for the adjustable support blocks at the small end, the pressing plates 10 for the adjustable support blocks at the large end, and the pressing plates 15 for the fixed support blocks at the large end to quickly disassemble the parts.

[0045] The inner half-pipe tooling design of the present invention meets the requirements of adaptive precision machining, greatly improving the finish machining quality of the workpiece; the optimized tooling design simplifies the machining process flow, reduces the operation difficulty of the operator, and can be machined in place at one time on a five-axis precision CNC machine, reducing the machining cost. The tooling design of the present invention adopts dynamic rigidity enhancement and vibration suppression technologies, greatly improving the machining accuracy of the under-supported parts of large-curvature thin-walled parts, and significantly reducing the machining chatter and tool breakage rate. The tooling clamping structure design of the present invention fits the curvature of the model, and the symmetric clamping design makes the pressure distribution uniform, avoiding machining deformation caused by local stress release; on the premise of facilitating loading and unloading, the overall tooling structure design fully meets the stiffness and strength requirements of machining.

Claims

1. A variable-diameter inner half-tube curved surface multi-point positioning and clamping numerical control milling fixture, characterized in that Based on an inner half-tube blank (17), both ends of the inner half-tube blank (17) are divided into a large end and a small end according to the size of the opening; The processing fixture includes: a small-end positioning plate (1) and a large-end positioning plate (13) which are inclined, and the extension lines of the two intersect to form an inverted V shape. Both the small-end positioning plate (1) and the large-end positioning plate (13) are polygonal plate structures, and the shape of the polygonal structure matches the inner wall outer shape of the corresponding large end or small end of the inner half-tube blank. The planes where the small-end positioning plate (1) and the large-end positioning plate (13) are located are perpendicular to each other; On both sides of the top surface of the small-end positioning plate (1), there are small-end adjustable clamping plates that can move along its inclined direction. On both sides of the top surface of the large-end positioning plate (13), there are large-end adjustable clamping plates that can move along its inclined direction. Near the edge of the small-end positioning plate (1) at the center of the top surface of the large-end positioning plate (13), there is a fixed clamping plate; Among them, the small-end positioning plate (1) is used to place the small end of the inner half-tube blank (17), and the small-end positioning plate (1) is parallel to the plane where the small end of the inner half-tube blank (17) is located; the large-end positioning plate (13) is used to place the large end of the inner half-tube blank (17), and the large-end positioning plate (13) is parallel to the plane where the large end of the inner half-tube blank (17) is located; the small-end adjustable clamping plates are used to clamp the inner walls on both sides of the small end of the inner half-tube blank (17), the large-end adjustable clamping plates are used to clamp the inner walls on both sides of the large end of the inner half-tube blank (17), and the fixed clamping plate is used to clamp the top inner wall of the large end of the inner half-tube blank (17).

2. The multi-point positioning and clamping numerical control milling fixture for the variable-diameter inner half-tube curved surface according to claim 1, wherein Each small-end adjustable clamping plate includes: a small-end adjustable support block (6), and the small-end adjustable support block (6) is connected to the waist-shaped hole on the small-end positioning plate (1) through a bolt, and the extending direction of the waist-shaped hole is the same as the extending direction of the small-end positioning plate (1); it also includes a small-end adjustable support block pressing plate (5), and the small-end adjustable support block pressing plate (5) is detachably connected to the small-end adjustable support block (6) through a bolt for clamping the outer wall of the inner half-tube blank 17; the surfaces of the small-end support plate (2) and the small-end adjustable support block (6) that contact the inner half-tube blank (17) are both profiling surfaces of the theoretical model.

3. A variable-diameter inner half-tube curved surface multi-point positioning and clamping numerical control milling fixture according to claim 1 or 2, characterized in that, Each large-end adjustable clamping plate includes: a large-end adjustable support block (11), and the large-end adjustable support block (11) is connected to the waist-shaped hole on the large-end positioning plate (13) through a bolt, and the extending direction of the waist-shaped hole is the same as the extending direction of the large-end positioning plate (13); it also includes a large-end adjustable support block pressing plate (10), and the large-end adjustable support block pressing plate (10) is detachably connected to the large-end adjustable support block (11) through a bolt for clamping the outer wall of the inner half-tube blank (17); the surfaces of the large-end adjustable support block pressing plate (10) and the large-end adjustable support block (11) that contact the inner half-tube blank (17) are both profiling surfaces of the theoretical model.

4. The variable-diameter inner half-tube curved surface multi-point positioning and clamping numerical control milling fixture according to claim 3, wherein, The fixed splint includes a large-end fixed support block (14), and the large-end fixed support block (14) is fixedly connected to the center of the top surface of the large-end positioning plate (13) near the edge of the small-end positioning plate (1); it further includes a large-end fixed support block pressing plate (15), and the large-end fixed support block pressing plate (15) is detachably connected to the large-end fixed support block (14) by bolts and is used to clamp the outer wall of the inner half-tube blank (17); the surfaces of the large-end fixed support block pressing plate (15) and the large-end fixed support block (14) that contact the inner half-tube blank (17) are both profiling surfaces of the theoretical model.

5. A variable-diameter inner half-tube curved surface multi-point positioning and clamping numerical control milling fixture according to claim 1 or 2, characterized in that, A cam connection post mounting block (7) is provided below the connection plate (3), and a cam connection post (8) is provided through the cam connection post mounting block (7); the axial direction of the cam connection post (8) is perpendicular to the extending direction of the connection plate (3), and cams (9) are connected to both ends of the cam connection post (8); the cams (9) are used to rotate following the rotation of the cam connection post (8) to contact the side wall of the inner half-tube blank (17) and complete the leveling of the inner half-tube blank (17).

6. The multi-point positioning and clamping CNC milling fixture for the variable-diameter inner semi-tube curved surface according to claim 1 or 2, characterized in that, The bottoms of the small-end positioning plate (1) and the large-end positioning plate (13) are connected to an H-shaped support frame, and the H-shaped support frame includes a small-end support plate (2) that is vertically arranged and connected to the small-end positioning plate (1), and a large-end support plate (12) that is vertically arranged and connected to the large-end positioning plate (13), and a connection plate (3) is connected between the small-end support plate (2) and the large-end support plate (12).

7. The variable-diameter inner half-tube curved surface multi-point positioning and clamping numerical control milling fixture according to claim 6, characterized in that, It further includes two springs (16), and both ends of each spring (16) are connected between the cam (9) and the connection plate (3).

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