Machining and positioning method for curved surface carbon-carbon composite material grid electrode with accurately centered array holes

Abstract

The invention relates to a curved-surface carbon-carbon composite material grid processing and positioning method for accurately centering array holes, belongs to the related technical field of machining, mounting and positioning, and relates to the curved-surface carbon-carbon composite material grid processing and positioning method for accurately centering the array holes. According to the method, two sets of special clamps are adopted for positioning, clamping and machining the grid electrode assembly containing the acceleration grid and the screen grid. Firstly, a special clamp is used for positioning and machining positioning holes and mounting holes, then a special clamp II array hole machining clamp is used for replacing, and positioning pin holes with the same relative positions are cut in a bottom plate according to the accurate relative positions of the machined positioning holes of the grid electrode. And executing an array hole processing program to ensure the centering property of the two gate array holes. And finally, executing a removing program of the redundant material at the edge of the grid to complete all processing of the curved-surface grid assembly. According to the method, accurate centering and stable positioning of laser processing of the grid electrode assembly are achieved, and the problems of positioning deviation caused by curved surface configuration and difficulty in controlling the centering performance of array holes are effectively solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mechanical processing installation positioning, and relates to a curved surface carbon-carbon composite material grid processing positioning method for precise centering of an array hole. BACKGROUND

[0002] As an advanced aerospace propulsion technology, the ion electric propulsion system plays a key role in satellite orbit control and attitude adjustment due to its high specific impulse, precise control, and long service life. The mechanical manufacturing precision of the grid assembly in the ion optical system of the ion electric propulsion system has a direct impact on the service performance of the entire system, reflected in thrust, specific impulse, and service life. The high ion sputtering resistance, low thermal expansion coefficient, and high temperature resistance of carbon-carbon composite material make it one of the best choices for grid assembly materials, and it is becoming the main application material for grid assembly of ion electric propulsion systems. The grid assembly has the core characteristics of dense array holes, ultra-thin structure, and strong anisotropy, and is a typical difficult-to-machine structure. The machining quality directly becomes one of the key bottlenecks restricting the service performance of the ion electric propulsion system grid assembly. Laser processing has the advantages of non-contact, high precision, and strong processing flexibility, and is used for precise machining of the dense array hole structure of the grid assembly.

[0003] The processing characteristics of the curved surface grid assembly are unique. The high-density array holes on the acceleration grid and screen grid serve as ion acceleration channels, and the centering of the array holes directly affects the ion acceleration effect. Therefore, the centering precision of the grid array holes is required to be high. The existing technical document, the invention patent with the patent number CN119175462A "Positioning device for femtosecond laser processing of curved surface workpiece" by Yang Yan, adopts an elastic mounting mechanism and a synchronous rotating mechanism to realize stable positioning and attitude adjustment of the curved surface workpiece, which can solve the problems of unstable positioning and processing deviation in the femtosecond laser processing of the curved surface workpiece. However, for special workpiece processing conditions such as grid assembly grid plates and other two parts with high-precision centering requirements, no targeted consideration has been made, and the processing demand cannot be fully met. SUMMARY

[0004] This invention addresses the alignment requirements of curved grid array holes in ion optics systems of ion electric thrusters by providing a method for precisely aligning curved carbon-carbon composite grids during machining. Taking a typical grid assembly comprising a screen grid and an acceleration grid as an example, the method first prepares a high-precision positioning circle on the base plate of a dedicated fixture for machining the functional holes of the grid, with a diameter equal to the largest spherical circle diameter of the curved grid surface region. During clamping, the largest spherical circle of the grid is positioned in the machine tool coordinate system by engaging with this positioning circle. Then, based on the designed positional relationship between the largest spherical circle of the grid and the functional holes, the machining coordinates of the functional holes are obtained. After machining the two grid mounting holes and the positioning holes respectively using an additional program, the fixture is changed to machine the array holes. This dedicated machining fixture, based on the precise relative positions of the machined positioning holes on the base plate, laser-cuts positioning pin holes with the same relative positions. By engaging the grid positioning holes with the fixture positioning pin holes, the machining coordinates of the array holes can be obtained based on the designed positional relationship between the array holes and the positioning holes. Using a "one-face, two-pin" positioning method, the acceleration gate or screen gate is clamped and the array hole machining program is executed to ensure the alignment of the two gate array holes. After the machining of a single gate array hole is completed, the edge redundant material is removed, and then the other gate is replaced to perform array hole and redundant material machining, thereby completing the entire machining of the curved gate assembly.

[0005] The technical solution adopted in this invention is a method for machining and positioning curved carbon-carbon composite gates with precise alignment of array holes. This method uses two sets of specialized fixtures to position, clamp, and machine the gate assembly containing the acceleration gate and the screen gate. The acceleration gate and the screen gate have the same structure except for the diameter of the gate holes. The specialized fixture I for machining the functional holes of the curved gate assembly consists of a cover plate I1, a base plate I2, and fixing feet I3; the cover plate I1 has 12 fixing holes I arranged circumferentially. 11 It is connected and fixed to the base plate I2 with bolts; the upper surface of the base plate I2 is flat, and there are 12 fixing holes evenly distributed around its circumference. 21 and countersunk screw hole I 22 Processed with an arc-shaped hollowed-out clearance structure I 23 And the positioning circle I processed by laser 24 The bottom surface of the base plate has radial reinforcing ribs I. 25 and circular reinforcing rib plate I 26 The fixed support leg I3 has a fixing hole I machined on it. 31 ;

[0006] The special fixture II for machining array holes of curved gate components consists of a cover plate II1, a base plate II2, and fixing feet II3, and is used for machining array holes and redundant materials; the cover plate II1 has 12 fixing holes II evenly distributed around its circumference. 11 It is connected and fixed to the base plate I2 with bolts; the upper surface of the base plate II2 is flat, with 12 fixing holes II evenly distributed around its circumference. 21 and countersunk screw hole II22 Processed with a bottom plate with a circular hollow structure II 23 The left positioning pin hole II of the base plate was machined using laser. 24 Right locating pin hole II on the base plate 25 The lower surface has radial reinforcing ribs II. 26 and circular reinforcing rib plate II 27 The fixed support foot II3 is machined with fixed support foot fixing holes II. 31 By cooperating with the gate positioning hole and the fixture positioning pin hole, the array hole machining coordinates are obtained according to the designed positional relationship between the array hole and the positioning hole.

[0007] The specific process steps of the positioning method are as follows:

[0008] Step 1: Preparation of the positioning circle for the special fixture I for machining functional holes

[0009] A positioning circle I is laser-cut on the base plate I2 of the special fixture I for machining functional holes. 24 Its diameter is the maximum spherical circle diameter φ1 of the gate surface region, that is, the outer circle diameter formed by the intersection of the curved surface and the plane. In the laser cutting program, the line connecting the starting position of the laser cutting head and the center of the positioning circle is set to be parallel to the X-axis of the machine tool, and the entire positioning circle is located on the -X side of the cutting starting point. Let the starting coordinates of the positioning circle machining be (x0, y0), where x0 is the starting point of the X-axis when the machine tool is machining the positioning circle, and y0 is the starting point of the Y-axis when the machine tool is machining the positioning circle; the laser beam diameter is d, then the coordinates of the center of the positioning circle are:

[0010] (x0-φ1 / 2+d / 2,y0)(1)

[0011] Step 2: Gate Functional Hole Fabrication

[0012] The acceleration grid or screen grid is installed with its inverted curved surface facing down between the base plate I2 and cover plate I1 of the special fixture I for machining functional holes, and the positioning circle I is used for machining. 24 The largest spherical circle of the gate is positioned, and the machining coordinates of the gate functional hole are obtained according to the designed positional relationship between the spherical circle and the gate functional hole. The gate functional hole is then positioned and machined. The gate functional holes are divided into two types: positioning holes and mounting holes. The center of the positioning hole is located on a circle with a diameter of φ2, and there are two positioning holes, 13 and 14, on the left and right, with a diameter of φ4=1mm. The center of the mounting hole is located on a circle with a diameter of φ3. The circles corresponding to φ2 and φ3 are concentric with the aforementioned largest spherical circle.

[0013] The coordinates of the centers of the two positioning holes are as follows:

[0014] (x0-φ1 / 2+d / 2+φ2 / 2,y0)(2)

[0015] (x0-φ1 / 2+d / 2-φ2 / 2,y0)(3)

[0016] The coordinates of the center of the mounting hole with the largest X-coordinate value are:

[0017] (x0-φ1 / 2+d / 2+φ3 / 2,y0)(4)

[0018] After all the functional holes of this single gate are processed, another gate is replaced for array hole processing.

[0019] Step 3: Preparation of locating pin holes for special fixture II for array hole machining

[0020] Replacement of special fixture for machining functional holes A special fixture II for array hole machining is used for array hole machining. The acceleration gate or screen gate is mounted with its curved surface facing upward between the base plate II2 and the cover plate II1 of the special fixture II for functional hole machining. Based on the actual relative position of the already machined gate positioning holes, two positioning pin holes II, one on the left and one on the right, are prepared on the base plate II2. 24 II 25 The diameter of the positioning hole is φ4. During processing, the positioning pin hole with the larger X coordinate value in the machine tool coordinate system is processed first. The starting point of laser cutting is set on the extension line of the line connecting the centers of the two positioning pin holes. Let the processing starting coordinates be (x1, y1), where x1 is the starting point of the X axis when the machine tool processes the positioning pin hole, and y1 is the starting point of the Y axis when the machine tool processes the positioning pin hole.

[0021] The coordinates of the centers of the two locating pin holes are as follows:

[0022] (x1-φ4 / 2+d / 2,y1)(5)

[0023] (x1-φ4 / 2-φ2+d / 2,y1)(6)

[0024] The line connecting the centers of the two locating pin holes is parallel to the X-axis of the machine tool.

[0025] Step 4: Gate array via fabrication

[0026] The accelerated gate or screen gate with completed functional hole machining is installed between the base plate II2 and cover plate II1 of the special fixture for array hole machining for processing. Through the cooperation between the positioning pin hole of the fixture and the gate positioning hole, the center coordinates of the hole at the center of the entire array hole can be determined as follows:

[0027] (x1-φ4 / 2-φ2 / 2+d / 2,y1)(7)

[0028] Based on the relative position of the central hole and other holes in the array, the spatial coordinates of all holes in the array are obtained for machining. The positioning holes of the two gates and the positioning pin holes on the fixture are matched in a "one-sided two-pin" manner to ensure that the array holes of the acceleration gate and the screen gate have precise alignment.

[0029] Execute the array aperture fabrication procedure to complete the fabrication of this single gate array aperture.

[0030] Step 5: Remove redundant material at the edges

[0031] After the gate array aperture is fabricated, a processing procedure is executed to remove redundant material from its edges.

[0032] If the outer diameter of the gate is φ5, then the starting coordinates of the cutting head when laser cutting redundant material are:

[0033] (x1-φ4 / 2-φ2 / 2+φ5 / 2+d,y1)(8)

[0034] The processing procedure is executed, and laser cutting is performed to remove redundant material at the edge of the gate.

[0035] After completing the processing of the single gate array aperture and edge redundancy material, replace the other gate and process the array aperture and edge redundancy material to complete all processing requirements for both gates.

[0036] The beneficial effects of this invention are as follows: Two sets of specially designed fixtures were developed to address the precision machining requirements for the array hole alignment of curved carbon-carbon composite gate components. These fixtures enable precise alignment and stable positioning during laser processing of the gate components, effectively solving the technical challenges of positioning offset caused by curved surface configurations and the difficulty in controlling array hole alignment. This fully meets the stringent requirements for array hole alignment in gate components. Consequently, it significantly improves the stability and reliability of the gate components during on-orbit operation, providing strong technical support for the laser precision manufacturing of high-performance gate components. Both gates are positioned using a "one-face, two-pin" method, satisfying the alignment requirements of the gate array holes, thereby improving the service performance of the gate components and extending their on-orbit lifespan. Attached Figure Description

[0037] Figure 1 Flowchart of a method for machining and positioning curved carbon-carbon composite gates for precise alignment of array apertures;

[0038] Figure 2 A top-view axonometric drawing of the overall assembly when using special fixture I to position and machine the functional holes of the screen.

[0039] In the diagram, Ⅰ1—cover plate, Ⅰ 11 —Cover plate fixing hole, Ⅰ2—Base plate, Ⅰ3—Fixing support foot, Ⅰ 31 —Fixed support foot fixing hole, 1—Screen grid, 11—Screen grid large mounting hole, 12—Screen grid small mounting hole, 13—Screen grid left positioning hole, 14—Screen grid right positioning hole.

[0040] Figure 3 Special fixture I is used for positioning and machining the functional holes of the screen. Figure 2 Right-side partial sectional view. In the figure, Ⅰ1—cover plate, Ⅰ11 —Cover plate fixing holes, Ⅰ2—Base plate, Ⅰ 22 —Counterhead screw hole, Ⅰ3—Fixed support leg, Ⅰ 31 —Fixed support feet fixing holes, 1—Screen grid, 11—Screen grid large mounting holes.

[0041] Figure 4 A top-view axonometric drawing of the overall assembly when using special fixture II to position and process the holes of the screen array.

[0042] In the diagram, Ⅱ1—cover plate, Ⅱ 11 —Cover plate fixing hole, Ⅱ2—Base plate, Ⅱ3—Fixing support foot, Ⅱ 31 —Fixed support foot fixing hole, 1—Screen grid, 11—Screen grid large mounting hole, 12—Screen grid small mounting hole, 13—Screen grid left positioning hole, 14—Screen grid right positioning hole.

[0043] Figure 5 When using special fixture II for positioning and machining screen array holes Figure 4 Right view partial sectional view.

[0044] In the diagram, Ⅱ1—cover plate, Ⅱ 11 —Cover plate fixing holes, Ⅱ2—Base plate, Ⅱ 22 —Counterhead screw hole, Ⅱ3—Fixing support foot, Ⅱ 31 —Fixed support feet fixing holes, 1—Screen grid, 11—Screen grid large mounting holes.

[0045] Figure 6 Top view of the curved gate grid. In the figure, φ1—diameter of the largest spherical circle in the curved gate area, φ2—diameter of the circumference where the center of the positioning hole is located, φ3—diameter of the circumference where the center of the mounting hole is located, φ4—diameter of the positioning pin hole, φ5—outer contour diameter, 1—grid, 11—large mounting hole of the grid, 12—small mounting hole of the grid, 13—left positioning hole of the grid, 14—right positioning hole of the grid, 1 A —The hole at the very center of the entire array of holes in the screen.

[0046] Figure 7 Top-view axonometric view of a special fixture for machining functional holes, where I1—cover plate, I... 11 —Cover plate fixing holes, Ⅰ2—Base plate, Ⅰ 23 —Arc-shaped hollowed-out clearance structure, Ⅰ 24 —Base plate positioning circle, Ⅰ3—Fixed support foot, Ⅰ3—Fixed support foot fixing hole.

[0047] Figure 8 Axonometric view of the base plate of the special fixture for machining functional holes (I). In the figure, I2—base plate, I... 21 —Base plate fixing holes, Ⅰ 23 —Arc-shaped hollowed-out clearance structure, Ⅰ 24 —Base plate positioning circle, Ⅰ 25—Radial reinforcing ribs, I 26 — Circular reinforcing rib plate.

[0048] Figure 9 Top-view axonometric drawing of the special fixture II for machining array holes. In the drawing, II1—cover plate, II 11 —Cover plate fixing holes, Ⅱ2—Base plate, Ⅱ 23 — Circular hollowed-out clearance structure, II 24 —Left positioning pin hole of base plate, II 25 —Right positioning pin hole on base plate, Ⅱ3—Fixed support foot, Ⅱ 31 —Fixing holes for the fixed support legs.

[0049] Figure 10 Axonometric view of the base plate of the special fixture II for machining array holes.

[0050] In the diagram, Ⅱ2—base plate, Ⅱ 21 —Base plate fastening holes, II 24 —Left positioning pin hole of base plate, II 25 —Right positioning pin hole on base plate, II 26 —Radial reinforcing ribs, II 27 — Circular reinforcing rib plate. Detailed Implementation

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the technical solutions and accompanying drawings.

[0052] Appendix Figure 1This invention relates to a method and fixture flowchart for positioning curved carbon-carbon gates to ensure the centering of array holes. Using laser processing as an example, this invention proposes a systematic positioning method and designs two sets of dedicated fixtures to complete the precision machining of curved gate components, based on the high-precision requirements for the centering of the gate array holes. The method first prepares a high-precision positioning circle on the base plate of the dedicated fixture for machining functional holes, with a diameter equal to the largest spherical circle diameter of the gate curved surface region. The spherical circle refers to the intersection circle formed by the intersection of a sphere and a plane. The functional holes include positioning holes and mounting holes. During clamping, both largest spherical circles of the gates mate with this positioning circle. Based on the positional relationship between the largest spherical circles of the gates and the functional holes, the machining coordinates of the two gate functional holes are obtained, and the program is executed to complete the machining of the two gate mounting holes and positioning holes respectively. Afterwards, the machine is switched to a dedicated fixture for array hole machining. Based on the precise relative positions of the pre-machined positioning holes on the base plate, left and right positioning pin holes with identical relative positions are cut. Through the cooperation between the gate positioning holes and the fixture positioning pin holes, the machining coordinates of the array holes are obtained according to the relative positional relationship between the array holes and the positioning holes. Using a "one-face, two-pin" positioning method, the acceleration gate or screen gate is clamped, and the array hole machining program is executed to ensure the alignment of the two gate array holes. After the machining of a single gate array hole is completed, edge redundancy material removal is performed. Then, the other gate is replaced, and the array hole and redundancy material machining are performed, thus completing the entire machining of the curved gate assembly.

[0053] This method employs two sets of specialized fixtures to position, clamp, and process the gate assembly containing the acceleration gate and the screen gate. The acceleration gate and the screen gate are structurally identical except for the diameter of the gate holes. The specialized fixture I used for processing the functional holes of the curved gate assembly consists of a cover plate I1, a base plate I2, and fixing feet I3; the cover plate I1 has 12 circumferentially arranged fixing holes I. 11 It is connected and fixed to the base plate I2 with bolts; the upper surface of the base plate I2 is flat, and there are 12 fixing holes evenly distributed around its circumference. 21 and countersunk screw hole I 22 Processed with a ring-shaped hollow relief structure I 23 And the positioning circle I processed by laser 24 The bottom surface of the base plate has radial reinforcing ribs I. 25 and circular reinforcing rib plate I 26 The fixed support leg I3 has a fixing hole I machined on it. 31 For the structure of special fixture I, please refer to [reference needed]. Figure 7 , 8 .

[0054] The special fixture II for machining array holes of curved gate components consists of a cover plate II1, a base plate II2, and fixing feet II3, and is used for machining array holes and redundant materials; the cover plate II1 has 12 fixing holes II evenly distributed around its circumference. 11It is connected and fixed to the base plate I2 with bolts; the upper surface of the base plate II2 is flat, with 12 fixing holes evenly distributed around its circumference. 21 and countersunk screw hole I 22 Processed with a bottom plate with a circular hollow structure II 23 The left positioning pin hole II of the base plate was machined using laser. 24 Right locating pin hole II on the base plate 25 The lower surface has radial reinforcing ribs II. 26 and circular reinforcing rib plate II 27 The fixed support foot II3 is machined with fixed support foot fixing holes II. 31。 For the specific structure of the special fixture II for machining curved gate assembly array holes, please refer to [link / reference]. Figure 9 , 10 By cooperating with the gate positioning hole and the fixture positioning pin hole, the machining coordinates of the array hole are obtained according to the designed positional relationship between the array hole and the positioning hole.

[0055] The specific process steps of the positioning method are as follows:

[0056] Taking a typical gate assembly as an example, it includes the processing of an acceleration gate and a screen gate. First, the gate functional hole is processed, and then the gate array hole is processed and the edge redundant material is removed.

[0057] Step 1: Preparation of the positioning circle for the special fixture for machining functional holes

[0058] Laser-cut positioning circle I on base plate I2 of special fixture for machining functional holes. 24 Its diameter is set to the maximum spherical circle diameter φ1 of the gate surface region, that is, the outer circle diameter formed by the intersection of the curved surface and the plane.

[0059] The maximum spherical circle diameter of the curved area of ​​the gate assembly, i.e., the outer circle diameter of the upper surface where the curved surface intersects the plane, is φ1=80mm. A positioning circle with the same diameter of 80mm is laser-cut on the fixture base plate. See Appendix. Figure 6 .

[0060] In the laser cutting program, the line connecting the starting position of the laser cutting head and the center of the positioning circle is set to be parallel to the X-axis of the machine tool, and the entire positioning circle is located on the -X side of the cutting starting point. Let the starting coordinates of the positioning circle machining be (x0, y0), where x0 is the starting point of the X-axis when the machine tool is machining the positioning circle, and y0 is the starting point of the Y-axis when the machine tool is machining the positioning circle.

[0061] If the laser beam diameter d = 70 μm, then the coordinates of the center of the positioning circle are:

[0062] (x0-39.965,y0)

[0063] Step 2: Gate Functional Hole Fabrication

[0064] The acceleration grid or screen grid is installed with its inverted curved surface facing down between the base plate I2 and cover plate I1 of the special fixture I for machining functional holes for processing. See [reference needed]. Figure 2 , 3 The gate functional holes are machined using a special fixture I for functional hole machining. Based on the previously prepared positioning circle, the largest spherical circle of the gate is positioned. Then, according to the designed positional relationship between the spherical circle and the gate functional hole, the machining coordinates of the gate functional hole are obtained, and the positioning machining of the gate functional hole is performed. The gate functional holes are divided into two categories: positioning holes and mounting holes. The positioning holes are located on a circle with a diameter of φ2 = 82 mm, with two positioning holes on the left and right. The mounting holes are located on a circle with a diameter of φ3 = 88 mm, and the circles corresponding to φ2 and φ3 are concentric with the aforementioned spherical circle. See Appendix. Figure 6 , 7 8.

[0065] The coordinates of the centers of the two positioning holes are as follows:

[0066] (x0+1.035,y0)

[0067] (x0-80.965,y0)

[0068] The coordinates of the center of the mounting hole with the largest X-coordinate value are:

[0069] (x0+4.035,y0)

[0070] After completing the fabrication of this gate functional hole, replace it with another gate and fabricate its functional hole. After completing the fabrication of both gate functional holes, perform gate array hole and edge redundant material removal processing.

[0071] Step 3: Preparation of locating pin holes for special fixture II for array hole machining

[0072] Replace the special fixture for machining functional holes with special fixture II for machining array holes. Mount the acceleration grid or screen grid with its curved surface facing upwards between the base plate II2 and cover plate II1 of special fixture II for machining. See attached document. Figure 4 , 5 Based on the actual relative positions of the already machined gate positioning holes, two positioning pin holes II with the same relative positions are prepared on the fixture base plate II2. 24 II 25 The positioning holes of the two gates and the positioning pin holes on the fixture are matched in a "one-sided two-pin" manner to ensure precise alignment of the array holes of the acceleration gate and the screen gate. The positioning hole diameter of the acceleration gate and the screen gate of the gate assembly is φ4=1mm.

[0073] The line connecting the centers of the locating pin holes is parallel to the X-axis of the machine tool. During machining, the locating pin hole with the larger X-coordinate value in the machine tool coordinate system is machined first. The starting point of laser cutting is set on the extension line connecting the centers of the two locating pin holes. Let the machining starting coordinates be (x1, y1), where x1 is the starting point of the X-axis when machining the locating pin hole, and y1 is the starting point of the Y-axis when machining the locating pin hole.

[0074] The coordinates of the centers of the two locating pin holes are as follows:

[0075] (x1-0.465,y1)

[0076] (x1-82.465,y1)

[0077] Step 4: Gate array via fabrication

[0078] Based on the aforementioned positioning pin holes, and through the fit between the fixture positioning pin holes and the gate positioning holes, the coordinates of the center of the hole in the center of the entire array can be determined as follows:

[0079] (x1-41.465,y1)

[0080] Based on the relative positions of the central hole and other holes in the array, the spatial coordinates of all holes in the array are obtained for processing.

[0081] Execute the array aperture fabrication procedure to complete the fabrication of this single gate array aperture.

[0082] Step 5: Remove redundant material at the edges

[0083] Use the array hole machining special fixture II to execute the machining program to remove redundant material at the edges.

[0084] If the outer diameter of the gate is φ5=95mm, then the starting coordinate of the cutting head when laser cutting redundant material is:

[0085] (x1+6.07,y1)

[0086] The machining program is executed, and laser cutting is performed to remove redundant material from the edge of this gate. After the machining of the gate array aperture and edge redundant material is completed, the other gate is replaced and the array aperture and edge redundant material are machined, thus completing all machining requirements for both gates.

[0087] To prevent adhesion during machining of the outer array holes, the base plates of the two sets of dedicated fixtures have an arc-shaped hollow clearance structure at the fixture position corresponding to the gate curved surface-planar transition zone. The cover plate and the base plate are fixed with bolts to ensure that the "one side, two pins" positioning is not disturbed. To enhance the overall rigidity of the fixture base plate, two types of reinforcing ribs are distributed on the bottom surface of the base plate, see Appendix Figure 8 Appendix Figure 10 .

[0088] When the two gates of the gate assembly are in service in the ion thruster, the two gate array holes are precisely aligned and installed with a spacing of less than 1 mm to perform ion beam acceleration tasks.

Claims

1. A method for processing and positioning a curved carbon-carbon composite gate with precise alignment of array holes, characterized in that, The method adopts two sets of special clamps to position and clamp and process the grid assembly provided with an accelerating grid and a screen grid; a special clamp (I) for processing a functional hole of the curved surface grid assembly is composed of a cover plate (I1), a bottom plate (I2) and a fixing support leg (I3); the cover plate (I1) is uniformly provided with 12 fixing holes (I 11 ) on the circumference and is connected and fixed with the bottom plate (I2) through bolts; the upper surface of the bottom plate (I2) is a plane and is uniformly provided with 12 fixing holes (I 21 ) and a countersunk screw hole (I 22 ); an arc-shaped hollow structure (I 23 ) is processed, and a positioning circle (I 24 ) is processed through laser; the lower surface is provided with a radial reinforcing rib (I 25 ) and a circular reinforcing rib plate (I 26 ); the fixing support leg (I3) is provided with a fixing hole (I 31 ). The special fixture (II) for machining array holes of curved gate components consists of a cover plate (II1), a base plate (II2), and fixed supports (II3), and is used for machining array holes and redundant materials; the cover plate (II1) has 12 fixed holes (II3) evenly distributed around its circumference. 11 ), and is fixed to the base plate (Ⅰ2) with bolts; the upper surface of the base plate (Ⅱ2) is flat, and 12 fixing holes (Ⅰ) are evenly distributed around the circumference. 21 ) and countersunk screw holes (Ⅰ 22 ), with a circular hollow structure on the bottom plate (II) 23 The left positioning pin hole (II) of the base plate was machined using laser technology. 24 ), right positioning pin hole on the base plate (II) 25 The lower surface has radial reinforcing ribs (II). 26 ) and circular reinforcing ribs (II) 27 The fixed support foot (Ⅱ3) is machined with a fixed support foot fixing hole (Ⅱ). 31 By cooperating with the gate positioning hole and the fixture positioning pin hole, the array hole machining coordinates are obtained according to the designed positional relationship between the array hole and the positioning hole; The specific process steps of the positioning method are as follows: Step 1: Preparation of positioning circle of special fixture for functional hole processing A positioning circle (I 24 ) is cut on the bottom plate (I2) of the fixture (I) by laser, and the diameter of the positioning circle is the maximum spherical circle diameter φ1 of the grid curved surface area, that is, the diameter of the outer circle formed by the intersection of the curved surface and the plane. In the laser cutting program, the line connecting the starting position of the laser cutting head and the center of the positioning circle is parallel to the machine tool X-axis, and the positioning circle is located on the -X side of the cutting starting point as a whole. The machining starting coordinates of the positioning circle are set as (x0, y0), wherein x0 is the starting point of the X-axis when the machine tool processes the positioning circle, and y0 is the starting point of the Y-axis when the machine tool processes the positioning circle. The laser beam diameter is d, and the center coordinates of the positioning circle are: (x0-φ1 / 2+d / 2,y0)(1) Step 2: Processing of gate functional hole The accelerating grid or screen grid is installed upside down with the curved surface facing down between the bottom plate (12) and the cover plate (11) of the fixture (1) for processing the functional hole, and the positioning circle (1 24 ) is used to position the maximum spherical circle of the grid, the processing coordinates of the grid functional hole are obtained according to the designed position relationship between the spherical circle and the grid functional hole, and the positioning processing of the grid functional hole is carried out; the grid functional hole is divided into two types of positioning holes and mounting holes, wherein the center of the positioning hole is located on the circumference with a diameter of φ2, there are left and right two positioning holes (13, 14) with a diameter of φ4=1mm; and the center of the mounting hole is located on the circumference with a diameter of φ3; the circles corresponding to φ2 and φ3 are concentric with the aforementioned maximum spherical circle; Then the center coordinates of the two positioning holes are respectively: (x0-φ1 / 2+d / 2+φ2 / 2,y0)(2) (x0-φ1 / 2+d / 2-φ2 / 2,y0)(3) The center coordinate of the mounting hole with the maximum X coordinate value is: (x0-φ1 / 2+d / 2+φ3 / 2,y0)(4) After completing the processing of all functional holes of this single gate, another gate is replaced for functional hole processing; Step 3: Preparation of positioning pin hole of special fixture for array hole processing The special fixture for functional hole machining is changed to a special fixture for array hole machining (II) for array hole machining; the acceleration grid or screen grid curved surface is installed upwardly between the bottom plate (II2) and the cover plate (II1) of the special fixture for functional hole machining (II) for machining, and according to the actual relative position of the machined grid positioning hole, left and right positioning pin holes (II 24 , II 25 ) are prepared on the bottom plate (II2), and the positioning hole diameter is φ4; during machining, the positioning pin hole with a larger X coordinate value in the machine tool coordinate system is machined first, and the starting point of laser cutting is arranged on the extension line of the center line of the two positioning pin holes; the machining starting coordinate is (x1, y1), wherein x1 is the starting point of the X axis when the machine tool machined the positioning pin hole, and y1 is the starting point of the Y axis when the machine tool machined the positioning pin hole; Then the center coordinates of the two positioning pin holes are respectively: (x1-φ4 / 2+d / 2,y1)(5) (x1-φ4 / 2-φ2+d / 2,y1)(6) The center line of the two positioning pin holes is parallel to the machine tool X axis; Step 4: Processing of gate array hole Through the cooperation between the fixture positioning pin hole and the gate positioning hole, it can be known that the center coordinate of the center hole in all array holes is: (x1-φ4 / 2-φ2 / 2+d / 2,y1)(7) According to the relative position of the center hole and other holes in the array, the spatial coordinates of all holes in the array are obtained for processing; The positioning holes of the two gates and the positioning pin holes on the fixture are cooperated in the "one side two pin" mode to ensure that the array holes of the acceleration grid and the screen grid have accurate centering property; Execute the array hole processing program to complete the array hole processing of this single gate; Step 5: Removal of edge redundant material After completing the array hole processing of this gate, execute the processing program to remove the edge redundant material; The diameter of the outer contour of the gate is φ5, and the starting coordinate of the cutting head when cutting the redundant material is: (x1-φ4 / 2-φ2 / 2+φ5 / 2+d,y1)(8) Execute the processing program to perform laser cutting and complete the removal of the edge redundant material of the gate; After completing the array hole and edge redundant material processing of this gate, another gate is replaced for array hole and edge redundant material processing to complete the processing requirements of the two kinds of gates.

Images