A coaxial fused wire additive manufacturing electron gun device

Abstract

This invention provides a coaxial filament additive manufacturing electron gun device, belonging to the field of additive manufacturing technology. It includes an annular bulk field emission cathode, a grid, an anode, and a focusing coil arranged coaxially from top to bottom along an axis. The annular bulk field emission cathode, grid, anode, and focusing coil form a cavity. The annular bulk field emission cathode has a hole, and a guide wire head extends into the cavity through the hole and is coaxially arranged with the annular bulk field emission cathode. A guide wire tube is disposed inside the guide wire head, and metal wire enters the cavity through the guide wire tube and the guide wire head. The annular bulk field emission cathode and grid are connected to a negative high-voltage power supply, and the anode is grounded. This device achieves real-time control of the electron gun beam in coaxial filament additive manufacturing, reduces the structural complexity of the electron gun, and improves the stability of the electron gun.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, specifically to an electron gun device for coaxial filament additive manufacturing of filament bundles. Background Technology

[0002] Currently, the application of large-scale integrated titanium and aluminum alloy structural components in aircraft is increasing, and their low-cost and efficient manufacturing has become a new challenge for the development of aerospace manufacturing technology. Arc welding additive manufacturing suffers from porosity defects in aluminum alloy manufacturing, leading to a decrease in the mechanical properties of the formed parts. Furthermore, due to aluminum's high reflectivity to lasers, laser additive manufacturing cannot be applied to the manufacturing of aluminum alloy wires. Therefore, electron beam welding additive manufacturing has significant advantages in the integrated forming of aluminum alloy structural components, making it suitable for the rapid prototyping of internal frames, reinforcing ribs, and panel structures.

[0003] Existing coaxial fused wire additive manufacturing electron gun devices generate electrons at the cathode by producing plasma from gas under high pressure. Positive ions in the plasma bombard the cathode surface under the influence of an electric field, generating secondary electrons. These secondary electrons and the electrons from the plasma together form the electron beam source. This method has the following drawbacks: 1) Because there are two electron sources, higher requirements are placed on beam stability. In actual operation, a problem with either beam source will cause the electron gun to malfunction. 2) Due to the thermal effect of the positive ion bombardment, an additional water-cooling channel needs to be designed for the cathode, increasing the complexity of the electron gun. 3) In beam control, the beam size needs to be controlled by adjusting the gas intake, requiring an additional real-time beam detection and feedback system. 4) Because there is a delay in adjusting the gas intake, real-time control of the beam size cannot be achieved. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides an electron gun device for coaxial filament additive manufacturing of filament bundles. This device realizes real-time control of the electron gun beam in coaxial filament additive manufacturing of filament bundles, reduces the structural complexity of the electron gun, and improves the stability of the electron gun.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a coaxial fused wire additive manufacturing electron gun device, comprising an annular bulk field emission cathode, a grid, an anode, and a focusing coil arranged coaxially from top to bottom along an axis. The annular bulk field emission cathode, grid, anode, and focusing coil form a cavity with a hollow structure. The annular bulk field emission cathode has a hole, and a guide wire head extends into the cavity from the hole in the annular bulk field emission cathode and is coaxially arranged with the annular bulk field emission cathode. A guide wire tube is disposed inside the guide wire head, and a metal wire enters the cavity through the guide wire tube and the guide wire head. The annular bulk field emission cathode and grid are connected to a negative high-voltage power supply, and the anode is grounded.

[0006] Furthermore, the annular bulk field emission cathode includes a cathode base and an array of annular bulk field emission cathodes. The cathode base has holes, and the array of annular bulk field emission cathodes is connected around the holes in the cathode base and is positioned facing the anode. The array of annular bulk field emission cathodes is a regular N-sided array cathode composed of multiple bulk graphene field emission cathodes or bulk graphene / carbon nanotube composite field emission cathodes, where N > 3.

[0007] Furthermore, N bulk field emission cathodes are connected along the height direction to form an array-type ring-shaped bulk field emission cathode. The height of each bulk field emission cathode in the array-type ring-shaped bulk field emission cathode is 10mm-15mm, the width is 2mm-4mm, the thickness is 300μm-500μm, and the emission current is 0mA-10mA.

[0008] Furthermore, the distance between the bottom end face of the array-type annular block field emission cathode and the top end face of the gate is 0.2mm-1mm, and the distance between the gate and the anode is 5mm-10mm.

[0009] Furthermore, the bulk graphene field emission cathode is prepared by cold pressing high-quality graphene, and the bulk graphene / carbon nanotube composite field emission cathode is prepared by mixing carbon nanotubes and high-quality graphene and then cold pressing. The high-quality graphene refers to graphene powder with 2-5 layers, a defect ratio of 0.08-0.2, and a C / O atomic ratio of 32.25-76.92.

[0010] Furthermore, the guide wire head has a frustum structure, with the smaller diameter end of the guide wire head extending into the chamber from the arrayed annular block field emission cathode and coaxially arranged with the arrayed annular block field emission cathode.

[0011] Furthermore, the negative high voltage range of the annular bulk field emission cathode is 30kV-60kV, and the negative high voltage of the gate connection is 0kV-5kV lower than that of the annular bulk field emission cathode.

[0012] Furthermore, the gate and anode are membrane aperture electrodes, with an outer diameter of 20mm-40mm, an inner diameter of 4mm-8mm, and a thickness of 1mm-3mm; an outer diameter of 20mm-40mm, an inner diameter of 6mm-10mm, and a thickness of 1mm-3mm; the focusing coil has 2000 turns and a focusing current of 0A-2A.

[0013] Furthermore, the annular bulk field emission cathode, grid, anode, and focusing coil are connected by insulating ceramic.

[0014] Furthermore, the cathode base, grid, and anode are made of stainless steel or aluminum alloy, and the guide wire head is an insulating ceramic component.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] This invention provides a coaxial filament additive manufacturing electron gun device, in which electron generation mainly relies on the field emission effect of the annular bulk field emission cathode, belonging to the cold cathode electron emission mode. Therefore, no additional cooling channel is required at the cathode, resulting in a simpler electron gun structure. Furthermore, since the electron source of this invention is solely the field emission cathode, the stability of the electron gun is significantly improved compared to other types of coaxial filament electron guns. Moreover, this invention uses a grid between the anode and cathode to form a three-stage electron gun. Beam current control can be achieved by changing the grid voltage. Compared to two-stage gas discharge electron guns, the beam current control of this invention has no delay, resulting in more efficient control. In summary, the coaxial filament electron gun proposed in this invention has the advantages of simple structure, stability, and high efficiency.

[0017] The array-type annular block field emission cathode and the wire guide head of the present invention are coaxially arranged to achieve coaxial wire feeding. During the forming process, there is no thermal shadow area in the wire, the part forming quality is good, and the path planning in the part forming process is simpler than that of bypass wire feeding. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an electron gun device for coaxial fused wire additive manufacturing of filament bundles according to the present invention.

[0019] Figure 2 This is a schematic diagram of the annular bulk field emission cathode of the present invention.

[0020] In the attached diagram: 1. Metal wire, 2. Guide tube, 3. Guide head, 4. Cathode base, 5. Arrayed ring-shaped bulk field emission cathode, 6. Grid, 7. Anode, 8. Focusing coil, 9. Insulating ceramic. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] like Figure 1As shown, the present invention proposes a coaxial fused wire additive manufacturing electron gun device, including a metal wire 1, a wire guide tube 2, a wire guide head 3, an annular bulk field emission cathode, a grid 6, an anode 7, and a focusing coil 8. The annular bulk field emission cathode, grid 6, anode 7, and focusing coil 8 are arranged coaxially from top to bottom along the axis and form a cavity.

[0023] The annular bulk field emission cathode includes a cathode base 4 and an array-type annular bulk field emission cathode 5. The array-type annular bulk field emission cathode 5 is connected around the holes of the cathode base 4 and is positioned facing the anode 7. The cathode base 4 is connected to a negative high-voltage power supply interface, and the anode 7 is grounded.

[0024] The array-type ring-shaped bulk field emission cathode 5 is a regular N-sided array cathode (N>3) composed of bulk graphene field emission cathodes or bulk graphene / carbon nanotube composite field emission cathodes. The regular N-sided array cathode is obtained by connecting N bulk field emission cathodes along the length direction.

[0025] The guide wire head 3 has a frustum structure. The smaller diameter end of the guide wire head 3 extends into the above-mentioned chamber from the arrayed annular block field emission cathode 5 and is coaxially arranged with the arrayed annular block field emission cathode 5. The guide wire tube 2 is arranged inside the guide wire head 3. The metal wire 1 enters the above-mentioned chamber through the guide wire tube 2 and the guide wire head 3 to achieve coaxial wire feeding.

[0026] The focusing coil 8 is located at the beam outlet of the anode 7 and is used to focus the electron beam into a high-energy-density electron beam spot.

[0027] Preferably, the bulk graphene field emission cathode is mainly prepared by cold pressing high-quality graphene; the bulk graphene / carbon nanotube composite field emission cathode is mainly prepared by cold pressing a certain proportion of carbon nanotubes and high-quality graphene. High-quality graphene refers to graphene powder with 2-5 layers, a defect ratio of 0.08-0.2, and a C / O atomic ratio of 32.25-76.92.

[0028] Preferably, the height of a single bulk field emission cathode is 10mm-15mm, the width is 2mm-4mm, the thickness is 300μm-500μm, and the emission current is 0mA-10mA.

[0029] Preferably, the negative high voltage range of the annular bulk field emission cathode connection is 30kV-60kV, and the negative high voltage of the grid connection is 0-5kV lower than that of the annular bulk field emission cathode.

[0030] Preferably, the anode 7 and the gate electrode 6 are membrane aperture electrodes. The outer diameter of the anode 7 is 20mm-40mm, the inner diameter is 6mm-10mm, and the thickness is 1mm-3mm. The outer diameter of the gate electrode 6 is 20mm-40mm, the inner diameter is 4mm-8mm, and the thickness is 1mm-3mm.

[0031] Furthermore, the distance between the bottom end face of the array-type annular block field emission cathode 5 and the top end face of the gate is 0.2mm-1mm, and the distance between the gate 6 and the anode 7 is 5mm-10mm.

[0032] Furthermore, the focusing coil 8 has 2000 turns and a focusing current of 0A-2A, and the beam size is controlled by controlling the focusing current.

[0033] Furthermore, the cathode base 4, the grid 6, the anode 7 and the focusing coil 8 are connected by an insulating ceramic 9 to prevent electric field breakdown. The insulating ceramic 9 has a withstand voltage of 60kV.

[0034] Furthermore, the guide wire head 3 is an insulating ceramic component with a withstand voltage of up to 60kV.

[0035] Furthermore, the cathode base 4, the grid 6, and the anode 7 are made of either stainless steel or aluminum alloy.

[0036] In summary, the present invention provides a coaxial fused wire additive manufacturing electron gun device. This device uses an array of ring-shaped bulk field emission cathodes composed of bulk graphene field emission cathodes or bulk graphene / carbon nanotube composite field emission cathodes to achieve coaxial filament transport. Because it utilizes the field emission effect of the bulk graphene field emission cathode, no cooling channel is required within the electron gun, simplifying its structure. Furthermore, beam current control of the electron gun only requires changing the grid voltage, further reducing the complexity of electron gun control.

[0037] like Figure 2 As shown, the electron gun device for coaxial filament additive manufacturing of the present invention is used as follows:

[0038] A decagonal ring-shaped bulk field emission cathode is formed by assembling a bulk graphene field emission cathode or a bulk graphene / carbon nanotube composite cathode, and then connected to a cathode base 4. This is then coaxially connected to a grid 6, anode 7, wire guide 3, focusing coil 8, and insulating ceramic 9 to form a wire bundle coaxial electron gun. The electron gun is then placed in a 5*10... -4 In the vacuum chamber of Pa, the annular bulk field emission cathode and grid of the electron gun are connected to a high-voltage power supply, while the electron gun anode and vacuum chamber are grounded. After the high voltage is turned on, electrons form an annular electron beam at the anode outlet. The filament is fed along the guide tube, and the focal point is adjusted by adjusting the current of the focusing coil. The beam current is adjusted by adjusting the grid voltage to meet different process requirements.

Claims

1. A coaxial fused wire additive manufacturing electron gun device, characterized in that, The device includes an annular bulk field emission cathode, a grid (6), an anode (7), and a focusing coil (8) arranged coaxially from top to bottom along the axis. The annular bulk field emission cathode, grid (6), anode (7), and focusing coil (8) form a cavity with a cavity. The annular bulk field emission cathode has a hole. The guide wire head (3) extends into the cavity from the hole on the annular bulk field emission cathode and is coaxially arranged with the annular bulk field emission cathode. The guide wire tube (2) is arranged inside the guide wire head (3). The metal wire (1) enters the cavity through the guide wire tube (2) and the guide wire head (3). The annular bulk field emission cathode and grid (6) are connected to a negative high voltage power supply, and the anode (7) is grounded. The annular bulk field emission cathode includes a cathode base (4) and an array-type annular bulk field emission cathode (5). The cathode base (4) has holes. The array-type annular bulk field emission cathode (5) is connected around the holes of the cathode base (4) and is positioned towards the anode (7). The array-type annular bulk field emission cathode (5) is a regular N-sided array cathode composed of multiple bulk graphene field emission cathodes or bulk graphene / carbon nanotube composite field emission cathodes, where N>3. The bulk graphene field emission cathode is prepared by cold pressing high-quality graphene, and the bulk graphene / carbon nanotube composite field emission cathode is prepared by mixing carbon nanotubes and high-quality graphene and then cold pressing. The high-quality graphene refers to graphene powder with 2-5 layers, a defect ratio of 0.08-0.2, and a C / O atomic ratio of 32.25-76.

92.

2. The electron gun device for coaxial filament additive manufacturing according to claim 1, characterized in that, N bulk field emission cathodes are connected along the height direction to form an array-type ring bulk field emission cathode (5). The height of a single bulk field emission cathode in the array-type ring bulk field emission cathode (5) is 10mm-15mm, the width is 2mm-4mm, the thickness is 300μm-500μm, and the emission current is 0mA-10mA.

3. The electron gun device for coaxial filament additive manufacturing according to claim 1, characterized in that, The distance between the bottom end face of the array-type annular block field emission cathode (5) and the top end face of the gate (6) is 0.2mm-1mm, and the distance between the gate (6) and the anode (7) is 5mm-10mm.

4. The electron gun device for coaxial filament additive manufacturing according to claim 1, characterized in that, The guide wire head (3) has a frustum structure. The smaller diameter end of the guide wire head (3) extends from the arrayed annular block field emission cathode (5) into the chamber and is coaxially arranged with the arrayed annular block field emission cathode (5).

5. The electron gun device for coaxial filament additive manufacturing according to claim 1, characterized in that, The negative high voltage range of the annular block field emission cathode is 30kV-60kV, and the negative high voltage of the gate (6) is 0kV-5kV lower than that of the annular block field emission cathode.

6. The electron gun device for coaxial filament additive manufacturing according to claim 1, characterized in that, The gate (6) and anode (7) are membrane holes. The outer diameter of the gate (6) is 20mm-40mm, the inner diameter is 4mm-8mm, and the thickness is 1mm-3mm. The outer diameter of the anode (7) is 20mm-40mm, the inner diameter is 6mm-10mm, and the thickness is 1mm-3mm. The number of turns of the focusing coil (8) is 2000, and the focusing current is 0A-2A.

7. The electron gun device for coaxial filament additive manufacturing according to claim 1, characterized in that, The annular block field emission cathode, grid (6), anode (7) and focusing coil (8) are connected by insulating ceramic (9).

8. The electron gun device for coaxial filament additive manufacturing according to claim 1, characterized in that, The cathode base (4), grid (6), and anode (7) are made of stainless steel or aluminum alloy, and the guide wire head (3) is an insulating ceramic part.

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