Method for forming apertures in a spherical carbon-carbon grid laser array for an ion thruster

Abstract

The application relates to the technical field of electric propulsion, in particular to a laser array hole forming method for a spherical carbon-carbon grid of an ion thruster, which comprises the following steps: step 1: fixing the spherical carbon-carbon grid on a laser processing workbench through a combined tool; step 2: scanning and fitting the spherical profile parameters of the carbon-carbon grid; step 3: carrying out fan-shaped partitioning on the spherical carbon-carbon grid, selecting one fan-shaped partitioning, and carrying out laser hole forming through a laser processing device; and step 4: rotating and arraying and splicing all information in the selected fan-shaped partitioning along an axial direction, and sequentially completing laser hole forming processing in the remaining fan-shaped partitionings. The application innovatively adopts the laser hole forming mode of fan-shaped partitioning and rotating arraying in combination with the special thin-walled curved multi-hole structure characteristics of the grid of the ion thruster and the carbon-carbon material characteristics, greatly simplifies the planning of the laser processing track, simultaneously, can eliminate the stepping error, and effectively guarantees the position precision of the grid holes.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electric propulsion, in particular to a method for forming holes in a laser array of a spherical carbon-carbon grid of an ion thruster. BACKGROUND

[0002] The ion thruster has the technical advantages of high specific impulse and precisely adjustable thrust, and has been widely used in the fields of space power, such as the north-south position keeping of a geosynchronous orbit satellite, the drag compensation of a low-orbit satellite, the attitude control and orbit transfer of a spacecraft, and the main propulsion of an interstellar probe.

[0003] The grid is a key component of the ion thruster, has a multi-hole thin-wall structure, forms an electrostatic field through a voltage difference between grids, focuses and accelerates ion beams generated after the ionization of working gas in a discharge chamber, and thus generates thrust; the grid generally adopts a spherical structure to ensure the consistency of the deformation direction of the grids in a thermal cycle condition and a mechanical environment, but the adoption of the spherical structure obviously increases the divergence of the beam, resulting in the loss of the thrust of the ion thruster; in order to offset the beam divergence caused by the spherical structure and make the trajectory of a single-hole beam close to the axial direction, a certain offset, generally less than 0.5%, needs to be made to the hole center distance of one of the grids, so that the grid assembly has a certain offset between the center axes of the holes of the grids.

[0004] At present, most of the grid materials at home and abroad adopt metal molybdenum, and through mature processes such as mask etching, spherical molding and high-temperature shaping, high-precision processing of the grid holes can be realized, but there is significant thermal deformation and sputtering corrosion in the working process, which limits the improvement of the reliability and service life of the ion electric propulsion. The carbon-carbon material has excellent thermal stability and ion sputtering resistance, and is an ideal grid material, which has been used as a raw material for the grid of the ion thruster in the United States, Japan and the United Kingdom.

[0005] However, the manufacturing process of the carbon-carbon grid is quite different from that of the metal molybdenum grid, and cannot be directly inherited, mainly in the problem of hole forming of the spherical carbon-carbon grid. The traditional processing method of the spherical carbon-carbon grid is prone to problems such as burrs, material delamination and fiber tearing. In view of the problem, in the patent CN109227740B “A hole forming method for a carbon grid assembly of an ion thruster”, a stepped drill bit and high-pressure liquid nitrogen cooling drilling are used to realize the mechanical processing of paired drilling of the carbon grid assembly in one clamping, but the method does not consider the “compensation” design of the spherical grid, and it is difficult to meet the requirement of beam focusing in the engineering application of the spherical carbon-carbon grid.

[0006] And laser working is a kind of non-contact unconventional processing technology, with the characteristics of fast processing speed, high efficiency, no tool loss, high processing surface quality, etc., suitable for hard, brittle, soft and other materials for multi-quantity, high-density group hole processing, but the existing laser group hole processing is generally used for planar structure, and the orthogonal or ring trajectory processing scheme is generally adopted, and for spherical high-precision group hole processing, there are few reports, therefore, how to realize the high-quality, high-efficiency and high-precision hole forming of spherical carbon-carbon grid is extremely difficult. SUMMARY

[0007] The application provides a kind of ion thruster spherical carbon-carbon grid laser array hole forming method, solve the quality, efficiency and precision of existing spherical carbon-carbon grid hole forming technology do not meet the problem of engineering application.

[0008] In order to achieve the above purpose, the application provides a kind of ion thruster spherical carbon-carbon grid laser array hole forming method, including the following steps: step 1: the spherical carbon-carbon grid is fixed on the laser processing workbench through the combined tooling;Step 2: scan fitting carbon-carbon grid spherical profile parameters;Step 3: the spherical carbon-carbon grid is divided into sectors, and one of the sectors is selected, and laser hole forming is carried out by laser processing device;Step 4: all information in the selected sector is rotated and arrayed along the axis, and laser hole forming in the remaining sectors is completed in turn.

[0009] Further, in step 1, the combined tooling includes a spherical lining tooling, a bottom plate tooling and a clamp, wherein: the bottom plate tooling is arranged on the laser processing workbench;The spherical lining tooling is fixed above the bottom plate tooling;The spherical carbon-carbon grid is fixed above the spherical lining tooling by the clamp, and the spherical profile of the spherical lining tooling is consistent with the lower surface of the spherical carbon-carbon grid.

[0010] Further, the material of the spherical lining tooling is graphite, which matches the material of the spherical carbon-carbon grid.

[0011] Further, in step 2, the process of scanning and fitting the spherical profile parameters of the carbon-carbon grid is as follows: step 2.1: import the three-dimensional model of the spherical carbon-carbon grid;Step 2.2: according to the laser ranging principle, scan and collect the spherical coordinate information of the spherical carbon-carbon grid;Step 2.3: fit the measured coordinate information to the three-dimensional model to determine the spherical profile parameters of the spherical carbon-carbon grid.

[0012] Further, the laser processing device in step 3 includes a pulsed laser and an auxiliary inert gas flow device.

[0013] Further, in step 3, the process of fan-shaped partition laser hole forming on the spherical carbon-carbon grid is as follows: step 3.1: the spherical carbon-carbon grid is partitioned into fan-shaped partitions at an angle of 60°; step 3.2: according to the carbon-carbon grid profile parameters determined in step 2, the relative position of the pulsed laser and the spherical carbon-carbon grid is set; step 3.3: taking the arc length interval between adjacent grid hole centers as the step control amount, the "S" shaped processing track is adopted to radiate outward from the center of the spherical carbon-carbon grid to form laser holes.

[0014] Further, in step 4, all the information in the selected fan-shaped partition includes pulsed laser position parameter information, pulsed laser parameter information and pulsed laser processing track parameter information.

[0015] Further, in step 4, after laser hole forming is completed in each fan-shaped partition, the pulsed laser is controlled to return to the center of the spherical carbon-carbon grid, and the center grid hole structure size information is collected and compared to eliminate the step error of the pulsed laser.

[0016] The ion thruster spherical carbon-carbon grid laser array hole forming method provided by the application has the following beneficial effects:

[0017] The application combines the special thin-walled curved multi-hole structure characteristics of the ion thruster grid and the carbon-carbon material characteristics, and innovatively adopts the fan-shaped partition rotating array splicing laser hole forming method, which greatly simplifies the planning of the laser processing track, and at the same time, the step error can be eliminated, the position accuracy of the grid hole is effectively guaranteed, and the engineering application requirements of high-quality, high-efficiency and high-precision hole forming of the spherical carbon-carbon grid are met. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings constituting a part of the application are used to provide a further understanding of the application, so that other features, objects and advantages of the application become more apparent. The illustrative embodiment drawings of the application and their descriptions are used to explain the application, and do not constitute an improper limitation on the application. In the drawings:

[0019] Figure 1 is an assembly drawing of the spherical carbon-carbon grid and the combined tooling provided according to the embodiment of the application;

[0020] Figure 2 is a sectional view of the assembly of the spherical carbon-carbon grid and the combined tooling provided according to the embodiment of the application;

[0021] Figure 3 is an effect drawing of the fan-shaped partition and array hole forming of the spherical carbon-carbon grid provided according to the embodiment of the application;

[0022] Figure 4 is a schematic diagram of the laser processing track provided according to the embodiment of the application;

[0023] In the figure: 1 - spherical carbon-carbon gate, 2 - spherical lining tool, 3 - base plate tool, 4 - clamp, 5 - pulsed laser, 6 - auxiliary inert gas flow device. DETAILED DESCRIPTION

[0024] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", and the like indicate the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not intended to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0027] In addition, in addition to indicating the orientation or positional relationship, the above-mentioned part of the terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. For those skilled in the art, the specific meaning of these terms in the present application can be understood according to the specific circumstances.

[0028] In addition, the meaning of the term "a plurality of" should be two and more than two.

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0030] In existing technologies, molybdenum is generally used to fabricate gate components. Mature processes such as mask etching, spherical forming, and high-temperature setting are employed to achieve high-precision gate hole processing. However, significant thermal deformation and sputtering corrosion persist during operation, limiting the reliability and lifespan of ion propulsion. Carbon-carbon materials, with their excellent thermal stability and resistance to ion sputtering, have become a replacement for molybdenum and the preferred material for gate components. However, achieving hole formation on the carbon-carbon gate remains a challenge in its fabrication. While some methods for creating holes in carbon gate components are disclosed in existing technologies, they do not consider the "compensation" design for spherical gates, making it difficult to meet the beam focusing requirements in engineering applications of spherical carbon-carbon gates. Furthermore, the processing efficiency and accuracy are relatively low. The laser array hole formation method for spherical carbon-carbon gates in ion thrusters provided in this application adopts a fan-shaped partitioned rotating array splicing laser hole formation method. This not only simplifies the planning of the laser processing trajectory and improves the efficiency of gate hole processing but also eliminates step errors, effectively ensuring the positional accuracy of the gate holes. Specifically, the method includes the following steps:

[0031] Step 1: As Figures 1-2 As shown, the spherical carbon-carbon gate 1 is fixed on the laser processing worktable using a combination fixture. The combination fixture mainly includes a spherical inner liner fixture 2, a base plate fixture 3, and a clamp 4. The base plate fixture 3 is set on the laser processing worktable; the spherical inner liner fixture 2 is fixed above the base plate fixture 3; the spherical carbon-carbon gate 1 is fixed above the spherical inner liner fixture 2 by the clamp 4. The spherical contour of the spherical inner liner fixture 2 is consistent with the lower surface of the spherical carbon-carbon gate 1. The material of the spherical inner liner fixture 2 is graphite, which matches the material of the spherical carbon-carbon gate 1 to ensure material consistency.

[0032] Step 2: Scan and fit the spherical contour parameters of the carbon-carbon gate. The specific process is as follows:

[0033] Step 2.1: Import the 3D model of the spherical carbon-carbon gate 1;

[0034] Step 2.2: Based on the principle of laser ranging, scan and collect the spherical coordinate information of the spherical carbon-carbon grid 1;

[0035] Step 2.3: Fit the measured coordinate information into the three-dimensional model to determine the spherical profile parameters of the spherical carbon-carbon gate 1.

[0036] Step 3: As Figures 3-4 As shown, the spherical carbon-carbon gate 1 is divided into sector sections, and one sector section is selected for laser hole formation using a laser processing device. The laser processing device includes a pulsed laser 5 and an auxiliary inert gas flow device 6. The inert gas flow assists the laser processing, ensuring the effectiveness of the laser hole formation and guaranteeing the beam focusing of the gate hole. The specific process is as follows:

[0037] Step 3.1: The spherical carbon-carbon grid 1 is divided into sectors at an angle of 60°, and numbered in clockwise direction as 1, 3, 5 and 2, 4, 6, respectively.

[0038] Step 3.2: For the selected sector, the relative position of the pulsed laser 5 and the spherical carbon-carbon grid 1 is set according to the carbon-carbon grid profile parameters determined in step 2.

[0039] Step 3.3: The arc length between adjacent grid hole centers is used as the step control amount, and the "S" shaped machining track is adopted to radiate outward from the center of the spherical carbon-carbon grid 1.

[0040] Step 4: All information in the selected sector is rotated and arrayed along the axial direction, including the pulsed laser 5 position parameter information, the pulsed laser 5 parameter information, and the pulsed laser 5 machining track parameter information, etc. Then, the laser hole forming machining in the remaining sectors is completed in sequence according to the sector order of 1, 2, 3, 4, 5, 6, greatly simplifying the planning of the laser machining track. After completing the laser hole forming in each sector, the pulsed laser 5 is controlled to return to the center of the spherical carbon-carbon grid 1, and the center grid hole structure size information is collected and compared to eliminate the step error of the pulsed laser 5, effectively ensuring the position accuracy of the grid holes. Finally, the laser hole forming is completed in all sectors, realizing the machining and forming of the overall grid holes of the spherical carbon-carbon grid 1.

[0041] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of forming apertures in a spherically faced carbon-carbon grid for an ion thruster laser array, characterized by, The method comprises the following steps: Step 1: fixing the spherical carbon-carbon grid on the laser processing workbench through a combination tool, the combination tool comprising a spherical lining tool, a bottom plate tool and a clamp, wherein: The bottom plate tool is arranged on the laser processing workbench; The spherical lining tool is fixed above the bottom plate tool; The spherical carbon-carbon grid is fixed above the spherical lining tool through the clamp, and the spherical profile of the spherical lining tool is consistent with the lower surface of the spherical carbon-carbon grid; The material of the spherical lining tool matches the material of the spherical carbon-carbon grid; Step 2: scanning and fitting the spherical profile parameters of the spherical carbon-carbon grid, and the specific process is as follows: Step 2.1: importing a three-dimensional model of the spherical carbon-carbon grid; Step 2.2: according to the laser ranging principle, scanning and collecting the spherical coordinate information of the spherical carbon-carbon grid; Step 2.3: fitting the measured spherical coordinate information to the three-dimensional model to determine the spherical profile parameters of the spherical carbon-carbon grid; Step 3: dividing the spherical carbon-carbon grid into sectors, and selecting one sector, and performing laser hole forming through a laser processing device, and the specific process is as follows: Step 3.1: dividing the spherical carbon-carbon grid into sectors according to a 60° angle; Step 3.2: according to the spherical profile parameters determined in step 2, setting the relative position of the laser in the laser processing device and the spherical carbon-carbon grid; Step 3.3: taking the arc length interval of adjacent grid hole centers as the step control amount, and taking the "S" shaped processing track to perform laser hole forming from the center of the spherical carbon-carbon grid outward; Wherein, the laser is a pulse laser, and the laser processing device further comprises an auxiliary inert gas flow device; Step 4: rotating and arraying all information in the selected sector along the axial direction to sequentially complete the laser hole forming in the remaining sectors; All information in the selected sector includes pulse laser position parameter information, pulse laser parameter information and pulse laser processing track parameter information; Wherein, after completing the laser hole forming in each sector, the pulse laser is controlled to return to the center of the spherical carbon-carbon grid, the grid hole structure size information of the center of the spherical carbon-carbon grid is collected and compared, and the step error of the pulse laser is eliminated.

2. The method of claim 1, wherein the method further comprises: The material of the spherical lining tool is graphite.

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