Multi-electron gun, multi-electron emission device and additive manufacturing equipment

Abstract

The invention belongs to the technical field of additive manufacturing, and discloses a multi-electron gun, a multi-electron emission device and additive manufacturing equipment. The multi-electron gun comprises a cathode assembly and an anode assembly which are sequentially and coaxially centered at intervals from top to bottom, the cathode assembly comprises a first cathode and a plurality of second cathodes arranged around the first cathode, the first cathode can emit first electrons, and the plurality of second cathodes can emit a plurality of second electrons; the anode assembly comprises an anode plate, a multi-gate structure and an outlet, the anode plate is used for attracting a first electron and a plurality of second electrons, the multi-gate structure comprises a first gate and a second gate, the first gate is used for regulating the first electron to form a first electron beam, and the second gate is used for regulating the plurality of second electrons to form a plurality of second electron beams; the first electron beam and the plurality of second electron beams are emitted from the outlet to form a total electron beam. The energy of the first electron beam and the second electron beams can be modulated, so that the temperature of the molten pool is more stable.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly to a multi-electron gun, a multi-electron emission device and an additive manufacturing equipment. Background Art

[0002] The electron beam selective melting metal additive manufacturing technology uses an electron beam as an energy source to manufacture solid components by layer-by-layer melting of metal powder in a vacuum environment. Due to the high power of the electron beam and the high absorption rate of the material to the electron beam energy, the manufactured parts have the characteristics of high density, low oxygen content, low thermal stress, not easy to deform and crack, high printing efficiency, high material utilization rate, etc., and are widely used in the fields of medical treatment, aerospace, etc.

[0003] At present, when the current electron gun forms refractory metal materials such as tungsten, molybdenum, tantalum, and niobium, it lacks the function of regulating the temperature field and stress field near the molten pool. To reduce the thermal stress of the material, the preheating temperature used is high, usually at the recrystallization temperature of the refractory metal material, resulting in coarse grains of the manufactured parts; during the forming process, the molten pool is unstable, the temperature gradient is high, and pores, spatter, cracks, etc. are likely to occur, resulting in the quality of the manufactured parts not meeting the application requirements.

[0004] Therefore, it is necessary to provide a multi-electron gun, a multi-electron emission device and an additive manufacturing equipment to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-electron gun, a multi-electron emission device and an additive manufacturing equipment, wherein the total electron beam includes a first electron beam with adjustable energy and a plurality of second electron beams surrounding the first electron beam, so that the temperature of the molten pool is more stable and the preheating temperature can be reduced.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] A multi-electron gun includes:

[0008] A cathode assembly and an anode assembly which are coaxially centered and arranged at intervals from top to bottom in sequence;

[0009] The cathode assembly includes a first cathode and a plurality of second cathodes arranged around the first cathode, the first cathode can emit a first electron, and the plurality of second cathodes can emit a plurality of second electrons;

[0010] The anode assembly includes an anode plate, a multi-grid structure, and an outlet. The anode plate is configured to attract the first electrons and a plurality of the second electrons. The multi-grid structure includes a first grid and a second grid. The first grid is used to regulate the first electrons to form a first electron beam, and the second grid is used to regulate a plurality of the second electrons to form a plurality of second electron beams. The first electron beam and the plurality of second electron beams are emitted from the outlet to form a total electron beam.

[0011] Preferably, the cathode assembly further includes:

[0012] A cathode tray having a plurality of accommodation through-holes, and the first cathode and a plurality of the second cathodes are respectively accommodated in the plurality of accommodation through-holes of the cathode tray.

[0013] Preferably, a plurality of first through-holes are formed in the anode plate, and the first cathode and a plurality of the second cathodes are respectively aligned with the plurality of first through-holes.

[0014] Preferably, the anode assembly further includes a plurality of shielding coils. The plurality of shielding coils are disposed on a side of the anode plate facing the cathode assembly, and the plurality of shielding coils respectively surround the plurality of first through-holes.

[0015] Preferably, the anode plate has a cooling flow channel, and the cooling flow channel forms a liquid inlet and a liquid outlet on the surface of the anode plate.

[0016] Preferably, the first grid and the second grid are coaxially arranged. The first grid has a second through-hole, and the second grid has a third through-hole. The second through-hole is aligned with the first cathode, and the third through-hole is aligned with a plurality of the second cathodes.

[0017] Preferably, the first grid and the second grid are coaxially arranged. The first grid has a fourth through-hole, and the second grid has a fifth through-hole. The second grid further has a plurality of partitions, and the plurality of partitions divide the fifth through-hole into a plurality of sub-through-holes. The fourth through-hole is aligned with the first cathode, and the plurality of sub-through-holes are respectively aligned with a plurality of the second cathodes.

[0018] A multi-electron emission device, comprising:

[0019] The multi-electron gun as described above;

[0020] A coil assembly coaxially arranged with the outlet of the multi-electron gun, and the coil assembly is used to regulate the total electron beam.

[0021] Preferably, the coil assembly includes a centering coil, an astigmatism coil, a focusing coil, and a deflection coil sequentially arranged from top to bottom.

[0022] An additive manufacturing device, comprising the multi-electron emission device as described above.

[0023] Advantages of the present invention:

[0024] This multi-electron gun includes a cathode assembly and an anode assembly that are coaxially centered and arranged at intervals from top to bottom in sequence. The cathode assembly includes a first cathode and a plurality of second cathodes arranged around the first cathode. The first cathode can emit first electrons, and the plurality of second cathodes can emit a plurality of second electrons. The anode assembly includes an anode plate, a multi-grid structure, and an outlet. The anode plate is used to attract the first electrons and the plurality of second electrons. The multi-grid structure includes a first grid and a second grid. The first grid is used to regulate the first electrons to form a first electron beam, and the second grid is used to regulate the plurality of second electrons to form a plurality of second electron beams. The first electron beam and the plurality of second electron beams are emitted from the outlet to form a total electron beam.

[0025] The first electrons and a plurality of second electrons surrounding the first electrons are generated by the cathode assembly. The anode plate is used to attract the first electrons and the plurality of second electrons. The first grid in the multi-grid structure is used to regulate the first electrons to form a first electron beam, and the second grid in the multi-grid structure is used to regulate the plurality of second electrons to form a plurality of second electron beams. The first electron beam and the plurality of second electron beams are emitted from the outlet to form a total electron beam, and the total electron beam hits the processing platform to form a total beam spot. It can be understood that in the total electron beam, a plurality of second electron beams are all arranged around the first electron beam, and the total beam spot also includes a first beam spot located at the center and a second beam spot surrounding the first beam spot. By applying different voltages to the first grid and the second grid, the first electron beam and the second electron beam have different currents, so that the areas, energies, and shapes of the first beam spot and the second beam spot are different, and the temperature field and stress field at the first beam spot and the second beam spot can be regulated. Among them, the energy of the first beam spot is relatively high and is used to melt metal powder to form a molten pool. A plurality of second beam spots are used for preheating, sintering, and thermal compensation to reduce the preheating temperature of refractory metal materials during printing and prevent recrystallization of refractory metals. A plurality of second beam spots are arranged around the outer periphery of the first beam spot, so that the molten pool is stable during the forming process, the temperature gradient is low, and it is not easy to generate pores, splashes, cracks, etc., thereby ensuring that the quality of the manufactured part can meet the application requirements.

[0026] The total electron beam emitted by this multi-electron gun has a first electron beam located at the center and a plurality of second electron beams arranged around the outer periphery of the first electron beam, and the energies of the first electron beam and the second electron beam can be modulated respectively through the multi-grid structure, so that the total beam spot formed by irradiating the processing platform with the total electron beam can not only meet the requirements of melting and forming, but also meet the requirements of large-area preheating, sintering, and thermal compensation, thereby being able to reduce the preheating temperature of refractory metal materials during printing, making the temperature of the molten pool more stable, and ensuring the quality of the manufactured part. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the structure of the multi-electron gun provided in the first embodiment of the present invention Figure 1 ;

[0028] Figure 2 It is a schematic diagram of the structure of the multi-electron gun (with the cathode assembly hidden) provided in the first embodiment of the present invention Figure 2 ;

[0029] Figure 3 It is a schematic diagram of the structure of the multi-grid structure provided in the first embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of the structure of the multi-electron gun provided in the second embodiment of the present invention;

[0031] Figure 5 It is a schematic diagram of the structure of the multi-grid structure provided in the second embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of the total beam spot generated by the multi-electron gun provided in the first embodiment of the present invention;

[0033] Figure 7 It is a schematic diagram of the total beam spot generated by the multi-electron gun provided in the second embodiment of the present invention;

[0034] Figure 8 It is a multi-electron emission device provided in the third embodiment of the present invention and an additive manufacturing equipment provided in the fourth embodiment.

[0035] In the figure:

[0036] 1. Multi-electron gun; 11. Cathode assembly; 111. First cathode; 112. Second cathode; 113. Cathode tray; 1131. Accommodating through hole; 12. Anode assembly; 121. Anode plate; 1211. First through hole; 122. Multi-grid structure; 1221. First grid; 1222. Second grid; 1223. Second through hole; 1224. Third through hole; 1225. Fourth through hole; 1226. Partition; 1227. Sub-through hole; 123. Shielding coil; 124. Accelerating member; 1241. Outlet;

[0037] 21. Centering coil; 22. Astigmatism coil; 23. Focusing coil; 24. Deflection coil;

[0038] 3. Housing; 31. Vacuum chamber;

[0039] 4. Processing platform. Detailed implementation manners

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only for explaining the present invention, rather than limiting the present invention. In addition, it should be noted that for the sake of description, only the parts related to the present invention are shown in the drawings, rather than all the structures.

[0041] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected", and "fixed" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0042] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over", and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "under", and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the horizontal height of the first feature is lower than that of the second feature.

[0043] In the description of this embodiment, the orientation or positional relationships such as "above", "below", "right", etc. are based on the orientation or positional relationships shown in the drawings. It is only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meanings.

[0044] Embodiment 1

[0045] At present, when forming refractory metal materials such as tungsten, molybdenum, tantalum, and niobium, the current electron gun lacks the function of regulating the temperature field and stress field near the molten pool, resulting in a high preheating temperature, usually at the recrystallization temperature of the refractory metal material, which causes the grains of the workpiece to be coarse; during the forming process, the molten pool is unstable, the temperature gradient is high, and it is easy to generate pores, splashes, cracks, etc., resulting in the quality of the workpiece not meeting the application requirements.

[0046] To solve the above problems, as Figures 1-3As shown in the figure, this embodiment provides a multi-electron gun 1. The multi-electron gun 1 includes a cathode assembly 11 and an anode assembly 12 that are coaxially centered and arranged at intervals from top to bottom. The cathode assembly 11 includes a first cathode 111 and a plurality of second cathodes 112 arranged around the first cathode 111. The first cathode 111 can emit first electrons, and the plurality of second cathodes 112 can emit a plurality of second electrons. The anode assembly 12 includes an anode plate 121, a multi-grid structure 122, and an outlet 1241. The anode plate 121 is used to attract the first electrons and the plurality of second electrons. The multi-grid structure 122 includes a first grid 1221 and a second grid 1222. The first grid 1221 is used to regulate the first electrons to form a first electron beam, and the second grid 1222 is used to regulate the plurality of second electrons to form a plurality of second electron beams. The first electron beam and the plurality of second electron beams are emitted from the outlet 1241 to form a total electron beam.

[0047] The first electrons and a plurality of second electrons surrounding the first electrons are generated by the cathode assembly 11. The anode plate 121 is used to attract the first electrons and the plurality of second electrons. The first grid 1221 in the multi-grid structure 122 regulates the first electrons to form a first electron beam, and the second grid 1222 in the multi-grid structure 122 regulates the second electrons to form a second electron beam. The first electron beam and the plurality of second electron beams are emitted from the outlet 1241 to form a total electron beam. As Figure 6 shown, the total electron beam hits the processing platform 4 to form a total beam spot.

[0048] It can be understood that in the total electron beam, a plurality of second electron beams all surround the first electron beam. The total beam spot also includes a first beam spot located at the center and a second beam spot surrounding the first beam spot. By applying different voltages to the first grid 1221 and the second grid 1222, the first electron beam and the second electron beam have different currents, so that the areas, energies, and shapes of the first beam spot and the second beam spot are different, and the temperature field and stress field at the first beam spot and the second beam spot can be regulated. Among them, the energy of the first beam spot is relatively high and is used to melt metal powder to form a molten pool. A plurality of second beam spots are used for preheating, sintering, and thermal compensation to reduce the preheating temperature of refractory metal materials during printing and prevent recrystallization of refractory metals. A plurality of second beam spots are arranged around the outer periphery of the first beam spot, so that the molten pool is stable during the forming process, the temperature gradient is low, and it is not easy to generate pores, splashes, cracks, etc., thereby ensuring that the quality of the workpiece can meet the application requirements.

[0049] The total electron beam emitted by this multi-electron gun 1 has a first electron beam located at the center and several second electron beams surrounding the outer periphery of the first electron beam, and the energies of the first electron beam and the second electron beams can be modulated respectively through the multi-grid structure 122, so that the total beam spot formed by irradiating the processing platform 4 with the total electron beam can not only meet the requirements of melting and forming, but also meet the requirements of large-area preheating, sintering, and thermal compensation, thereby being able to reduce the preheating temperature of refractory metal materials during printing, making the temperature of the molten pool more stable, and ensuring the quality of the workpiece.

[0050] In this embodiment, the size of the first beam spot is 50μm - 200μm, and the size of the total beam spot is greater than 2mm. The specific size is determined according to actual printing needs, and this embodiment does not limit it.

[0051] Specifically, as Figure 1 shown, the cathode assembly 11 further includes a cathode tray 113, and the cathode tray 113 has a number of accommodation through-holes 1131. The first cathode 111 and several second cathodes 112 are respectively accommodated in the number of accommodation through-holes 1131 of the cathode tray 113. The cathode tray 113 provides a stable support platform for the first cathode 111 and several second cathodes 112, ensuring the stability of the first cathode 111 and several second cathodes 112, and guaranteeing the emission accuracy of the first electrons and the second electrons.

[0052] Specifically, as Figure 1 shown, a number of first through-holes 1211 are formed on the anode plate 121, and the first cathode 111 and several second cathodes 112 respectively face the number of first through-holes 1211. The anode plate 121 can attract the first electrons and the second electrons, and enables the first electrons and the several second electrons generated by the first cathode 111 and the several second cathodes 112 to pass through different first through-holes 1211 respectively, so as to form a first electron beam and several second electron beams in the subsequent multi-grid structure 122.

[0053] In this embodiment, as Figure 1 、 Figure 2 shown, the anode assembly 12 further includes a number of shielding coils 123. The number of shielding coils 123 is arranged on the side of the anode plate 121 facing the cathode assembly 11, and the number of shielding coils 123 respectively surround the number of first through-holes 1211. The shielding coils 123 can generate a magnetic field to deflect the first electrons or the second electrons, so that both the first electrons and the several second electrons can be emitted from the corresponding first through-holes 1211, preventing interference between the first electrons and the several second electrons, and avoiding the first electrons or the several second electrons hitting the anode plate 121 and losing energy or damaging the anode plate 121.

[0054] Specifically, the anode plate 121 has a cooling channel, and the cooling channel forms a liquid inlet and a liquid outlet on the surface of the anode plate 121. The coolant can enter the anode plate 121 through the liquid inlet, circulate through the cooling channel, and be discharged from the liquid outlet, which can effectively carry away the heat generated by the anode plate 121 during operation, avoid overheating of the anode plate 121, and extend the service life of the multi-electron gun 1.

[0055] In this embodiment, as Figure 3 shown, the first grid 1221 and the second grid 1222 are coaxially arranged. The first grid 1221 has a second through hole 1223, and the second grid 1222 has a third through hole 1224. The second through hole 1223 faces the first cathode 111, and the third through hole 1224 faces a plurality of second cathodes 112. By applying different voltages to the first grid 1221 and the second grid 1222, different electric fields are formed in the third through hole 1224 and the fourth through hole 1225, so as to regulate and control the formation of the first electron beam and the second electron beam with different currents. It should be noted that the currents of the plurality of second electron beams are the same, that is, the currents of the plurality of second electron beams can only be regulated as a whole.

[0056] Specifically, as Figure 1 、 Figure 2 shown, the anode assembly 12 further includes an accelerating member 124, and the accelerating member 124 includes an accelerating channel and an outlet 1241. The accelerating member 124 can accelerate the first electron beam and the second electron beam. The first electron beam and the second electron beam are accelerated by the accelerating channel and then emitted from the outlet 1241 to form a total electron beam.

[0057] Embodiment 2

[0058] As Figure 4 、 Figure 5 shown, this embodiment provides a multi-electron gun 1, whose structure is basically the same as that of the multi-electron gun 1 provided in Embodiment 1, and the difference lies in the structure of the second grid 1222, specifically:

[0059] The first grid 1221 and the second grid 1222 are coaxially arranged. The first grid 1221 has a fourth through hole 1225, and the second grid 1222 has a fifth through hole. The second grid 1222 also has a number of partitions 1226, and the number of partitions 1226 divides the fifth through hole into a number of sub-through holes 1227. The fourth through hole 1225 faces the first cathode 111, and the number of sub-through holes 1227 respectively face a number of second cathodes 112. By applying different voltages to the parts of the first grid 1221 and the second grid 1222 where each sub-through hole 1227 is located, different electric fields are formed in the fourth through hole 1225 and the number of sub-through holes 1227, so as to regulate and control the formation of a first electron beam and a second electron beam with different currents. It should be noted that the currents of the number of second electron beams can be the same or different, that is, the currents of the number of second electron beams can be regulated as a whole or separately. As Figure 7 shown, the total beam spot formed on the processing platform 4 by the total electron beam emitted by the multi-electron gun 1 in this embodiment.

[0060] Embodiment III

[0061] As Figure 8 shown, this embodiment provides a multi-electron emission device, including the multi-electron gun 1 and the coil assembly provided in Embodiment I or Embodiment II. The coil assembly is coaxially arranged with the outlet 1241 of the multi-electron gun 1, and the coil assembly 2 is used to regulate the total electron beam. The total electron beam required for the electron beam printing technology is generated by the multi-electron gun 1, and the total electron beam is regulated by the coil assembly 2 to adjust the parameters and trajectory of the total electron beam.

[0062] Specifically, the coil assembly 2 includes a centering coil 21, an astigmatism coil 22, a focusing coil 23, and a deflection coil 24 arranged in sequence from top to bottom. The centering coil 21 can correct the asymmetry of the total electron beam; the astigmatism coil 22 can correct the cross-sectional areas of the first electron beam and the number of second electron beams into a required shape, such as a standard circle, and eliminate the phase difference, so as to be able to reduce the beam diameter, so that the energy of the total electron beam can be better applied to the printing process; the focusing coil 23 is used to focus the total electron beam and reduce the diameter of the total beam spot; the deflection coil 24 is used to deflect the total electron beam, correct the bunching angle of the total electron beam, and make it accurately hit the processing platform 4 to improve the printing accuracy, thereby improving the quality of the workpiece.

[0063] Embodiment IV

[0064] As Figure 8 shown, this embodiment provides an additive manufacturing equipment, including the multi-electron emission device provided in Embodiment III.

[0065] Specifically, the additive manufacturing equipment further includes a housing 3 and the above-mentioned processing platform 4. The housing 3 has a vacuum chamber 31, and the processing platform 4 and at least part of the multi-electron emission device are located in the vacuum chamber 31 of the housing 3. The housing 3 provides the vacuum environment required for the electron beam printing technology, and the processing platform 4 provides the printing position.

[0066] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A multiple electron gun (1), characterized in that: include: A cathode assembly (11) and an anode assembly (12) are sequentially arranged coaxially and spaced from top to bottom; The cathode assembly (11) comprises a first cathode (111) and a plurality of second cathodes (112) arranged around the first cathode (111), the first cathode (111) being capable of emitting first electrons, and the plurality of second cathodes (112) being capable of emitting a plurality of second electrons; The anode assembly (12) comprises an anode plate (121), a multi-grid structure (122) and an outlet (1241); the anode plate (121) is used to attract the first electron and a plurality of the second electrons; the multi-grid structure (122) comprises a first grid (1221) and a second grid (1222); the first grid (1221) is used to regulate the first electron to form a first electron beam; the second grid (1222) is used to regulate a plurality of the second electrons to form a plurality of second electron beams; the first electron beam and the plurality of the second electron beams are emitted from the outlet (1241) to form a total electron beam.

2. The multiple electron gun (1) according to claim 1, characterized in that: The cathode assembly (11) further comprises: The cathode tray (113) has a plurality of accommodating through holes (1131), and the first cathode (111) and a plurality of the second cathodes (112) are accommodated one by one in the plurality of accommodating through holes (1131) of the cathode tray (113).

3. The multiple electron gun (1) according to claim 1, characterized in that: The anode plate (121) is provided with a plurality of first through holes (1211), and the first cathode (111) and a plurality of the second cathodes (112) are aligned with the plurality of first through holes (1211) one by one.

4. The multiple electron gun (1) according to claim 3, characterized in that: The anode assembly (12) further comprises a plurality of shielding coils (123), wherein the plurality of shielding coils (123) are arranged on a side of the anode plate (121) facing the cathode assembly (11), and the plurality of shielding coils (123) are arranged one by one correspondingly around the plurality of first through holes (1211).

5. The multiple electron gun (1) according to claim 1, characterized in that: The anode plate (121) has a cooling channel, and the cooling channel forms a liquid inlet and a liquid outlet on the surface of the anode plate (121).

6. The multiple electron gun (1) according to claim 1, characterized in that: The first grid (1221) and the second grid (1222) are coaxially arranged, the first grid (1221) has a second through hole (1223), the second grid (1222) has a third through hole (1224), the second through hole (1223) is opposite to the first cathode (111), and the third through hole (1224) is opposite to a plurality of the second cathodes (112).

7. The multiple electron gun (1) according to claim 1, characterized in that: The first grid (1221) and the second grid (1222) are coaxially arranged, the first grid (1221) has a fourth through hole (1225), the second grid (1222) has a fifth through hole, the second grid (1222) also has a plurality of partitions (1226), the plurality of partitions (1226) divide the fifth through hole into a plurality of sub-through holes (1227), the fourth through hole (1225) is opposite to the first cathode (111), and the plurality of sub-through holes (1227) are opposite to the plurality of second cathodes (112) one by one.

8. A multi-electron emission device, characterized in that: include: The multiple electron gun (1) according to any one of claims 1 to 7; A coil assembly is coaxially arranged with the outlet (1241) of the multiple electron gun (1), and the coil assembly is used to control the total electron beam.

9. The multi-electron emission device according to claim 8, characterized in that: The coil assembly comprises a centering coil (21), an astigmatism coil (22), a focusing coil (23) and a deflection coil (24) which are arranged in sequence from top to bottom.

10. An additive manufacturing device, characterized in that: Comprising the multi-electron emission device as claimed in claim 8.

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