A bypass wire-fed additive manufacturing system based on a field emission cathode

Abstract

This invention discloses a bypass wire feeding additive manufacturing system based on a field emission cathode, comprising an electron gun employing a field emission bulk cathode disposed in a vacuum chamber, a forming substrate disposed at the electron beam exit direction of the electron gun, a wire feeder disposed between the electron gun and the forming substrate, the wire feeder being fixed to the side wall of the vacuum chamber, the electron gun being connected to an electron gun control system for controlling the electron gun's opening and closing, beam current adjustment, electron beam focusing, deflection, and astigmatism correction functions, the wire feeder being connected to the wire feeding control system for bypassing and feeding metal wire onto the forming substrate, the forming substrate being connected to a motion control system for controlling the movement direction of the forming substrate, and the vacuum chamber being connected to a vacuum control system for controlling the vacuum level of the vacuum chamber. This invention uses a field emission cathode to avoid changes in the magnetic field around the electron gun caused by cathode heating, thus avoiding the need for additional heating and cooling equipment and helping to reduce the complexity of the equipment structure and control system.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, specifically to a bypass wire feeding additive manufacturing system based on a field emission cathode. Background Technology

[0002] Compared with electric arc fusion and laser fusion additive manufacturing technologies, electron beam fusion additive manufacturing technology has significant advantages in the high-quality, high-efficiency and rapid manufacturing of large metal components, and is mainly used in the internal frame, reinforcing ribs and wall panel structures of the machine body.

[0003] Currently, common electron beam fused wire additive manufacturing equipment primarily uses hot cathodes, represented by tungsten and lanthanum hexaboride. The cathode is heated primarily through direct or indirect heating. Direct heating involves passing an electric current across the cathode, utilizing Joule heating to raise it to a specified temperature. In this method, fluctuations in the heating current can cause changes in the magnetic field around the electron gun, affecting the beam shape and consequently the molding quality. Indirect heating primarily uses lasers or electron beams to bombard the cathode to a specified temperature. While this avoids the problems of direct heating, it introduces additional heating equipment outside the electron gun, increasing the equipment cost. Regardless of whether direct or indirect heating is used, a cooling path is needed to cool the surrounding clamping base and grid, increasing the complexity of the equipment's mechanical structure. Furthermore, an additional heating control system must be designed. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a bypass wire feeding additive manufacturing system based on a field emission cathode, wherein the electron gun cathode adopts a field emission cathode, avoiding changes in the magnetic field around the electron gun caused by cathode heating, eliminating the need for additional heating and cooling equipment, and helping to reduce the complexity of the equipment structure and control system.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a bypass wire feeding additive manufacturing system based on a field emission cathode, comprising an electron gun employing a field emission bulk cathode, the electron gun being disposed in a vacuum chamber, a forming substrate being disposed in the direction of the electron beam exit of the electron gun, a wire feeder being disposed between the electron gun and the forming substrate, the wire feeder being fixed on the side wall of the vacuum chamber, the electron gun being connected to an electron gun control system for controlling the opening and closing of the electron gun, beam current adjustment, electron beam focusing, deflection, and astigmatism correction functions, the wire feeder being connected to the wire feeding control system for transporting metal wire from the bypass onto the forming substrate, the forming substrate being connected to a motion control system for controlling the movement direction of the forming substrate, and the vacuum chamber being connected to a vacuum control system for controlling the vacuum level of the vacuum chamber to reach the required working vacuum level.

[0006] Furthermore, the electron gun includes, from top to bottom, a cathode base, a field emission block cathode, a grid, an anode, a dissipation coil, a deflection coil, and a focusing coil, all coaxially mounted. The field emission block cathode is vertically arranged on the central axis of the cathode base on the side facing the anode.

[0007] Furthermore, the field emission bulk cathode is a bulk graphene field emission cathode or a bulk graphene / carbon nanotube composite field emission cathode.

[0008] Furthermore, the bulk graphene field emission cathode is prepared by cold pressing high-quality graphene; the bulk graphene / carbon nanotube composite field emission cathode is prepared by cold pressing a mixture of carbon nanotubes and high-quality graphene.

[0009] Furthermore, 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 negative high voltage applied to the field emission block cathode is 30kV-60kV, the negative high voltage applied to the grid is 0kV-5kV lower than that of the cathode base, the anode is grounded, and the vacuum chamber is grounded.

[0011] Furthermore, the electron gun uses bypass wire feeding with a wire feeding angle ranging from 0° to 45°.

[0012] Furthermore, a three-dimensional motion platform is provided at the bottom of the molded substrate, and the motion control system is connected to the three-dimensional motion platform to control the movement of the three-dimensional motion platform.

[0013] Furthermore, the motion control system controls the movement of the three-dimensional motion platform based on the slicing path of the formed part.

[0014] Furthermore, the field emission bulk cathode has a height of 10mm-15mm, a width of 2mm-4mm, a thickness of 300μm-500μm, and an emission current of 0mA-20mA.

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

[0016] This invention provides a bypass wire feeding additive manufacturing system based on a field emission cathode. The electron gun cathode is a field emission cathode, which is a cold cathode emission mode. It eliminates the need for external heating equipment, a heating control system, and a cooling path for the cathode. This simplifies the electron gun structure, reduces the complexity of the control system, and helps lower equipment costs. Furthermore, the electron gun's magnetic field is free from external magnetic field interference, thus having no impact on the beam spot and resulting in greater equipment stability, which helps improve the quality of the formed parts. In summary, the bypass wire feeding additive manufacturing equipment based on a field emission cathode proposed in this invention has the advantages of simple structure, stability, and low cost.

[0017] The bulk graphene field emission cathode or bulk graphene / carbon nanotube composite field emission cathode of the present invention uses high-quality graphene as the electron emitter, fully utilizing the high electrical and thermal conductivity of graphene to accelerate Joule heat conduction, reduce ablation of the emission point, and achieve stable emission at high current (high current density). Preparation only requires adding graphene powder or a mixture of carbon nanotubes and high-quality graphene powder to a mold and applying pressure to form the cathode; no complex processing or high-temperature treatment is required during preparation, offering advantages such as speed, high efficiency, energy saving, and easy scalability. Attached Figure Description

[0018] Figure 1 A schematic diagram of a bypass wire feeding additive manufacturing device based on a field emission cathode.

[0019] In the attached diagram: 1. Electron gun; 10. Electron gun control system; 101. Cathode base; 102. Field emission bulk cathode; 103. Grid; 104. Anode; 105. Dissipation coil; 106. Deflection coil; 107. Focusing coil; 20. Wire feeding control system; 201. Wire feeder; 202. Metal wire; 3. Vacuum chamber; 30. Motion control system; 301. Molding substrate; 40. Vacuum control system. Detailed Implementation

[0020] 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.

[0021] like Figure 1 As shown, the present invention provides a bypass wire feeding additive manufacturing system based on a field emission cathode, comprising: an electron gun 1 connected to the top of a vacuum chamber 3; the electron gun 1 being composed of a cathode base 101, a field emission bulk cathode 102, a grid 103, an anode 104, a dissipation coil 105, a deflection coil 106, and a focusing coil 107 coaxially mounted from top to bottom; the cathode base 101, grid 103, anode 104, dissipation coil 105, deflection coil 106, and focusing coil 107 being connected by insulating ceramic; and a wire feeder 201 disposed between the electron gun 1 and the forming substrate 301, the wire feeder 201 being connected to the inner wall of the vacuum chamber 3 for bypass wire feeding.

[0022] Electron gun 1 and forming substrate 301 are disposed in vacuum chamber 3. Electron gun 1 is positioned above forming substrate 301 with its electron beam outlet facing forming substrate 301. Electron gun control system 10 is electrically connected to electron gun 1 to realize the functions of opening and closing electron gun 1, adjusting beam current, focusing electron beam, deflection, and astigmatism correction. Wire feeding control system 20 is electrically connected to wire feeder 201 to control wire feeder 201 to transport metal wire 202 to forming substrate 301. Motion control system 30 is connected to forming substrate 301 to control the movement direction of forming substrate 301. Vacuum control system 40 is connected to vacuum chamber 3 to control the vacuum level of vacuum chamber 3 to reach the required working vacuum level.

[0023] Preferably, the field emission bulk cathode 102 is a bulk graphene field emission cathode or a bulk graphene / carbon nanotube composite field emission cathode, with a cathode height of 10mm-15mm, a width of 2-4mm, a thickness of 300-500μm, and an emission current of 0-20mA.

[0024] 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.

[0025] Preferably, 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;

[0026] Preferably, the negative high voltage applied to the field emission block cathode 102 is 30-60kV, the negative high voltage applied to the grid 103 is 0-5kV lower than that of the cathode base 101, the anode 104 is grounded, and the vacuum chamber 3 is grounded.

[0027] Preferably, the wire feeder 201 has a wire feeding angle of 0 to 45°, and the wire feeder 201 transports the metal wire 202 onto the molding substrate 301 and is located at the center of the axis of the electron gun 1.

[0028] Preferably, a three-dimensional motion platform is provided at the bottom of the molding substrate 301, and the motion control system 30 is connected to the three-dimensional motion platform. The movement of the three-dimensional motion platform is controlled by the slicing path of the molding part, thereby realizing additive manufacturing on the molding substrate 301.

[0029] Example 1

[0030] After the vacuum control system 40 controls the vacuum level in the vacuum chamber 3 to reach the specified vacuum level, the wire feeding control system 20 controls the wire feeder 201 to transport the metal wire 202 to the specified position. Based on the preset electron gun parameters, the electron gun control system 10 controls the bypass wire feeding electron gun 1 to turn on and focus, emitting an electron beam. The motion control system 30 controls the movement of the three-dimensional motion platform based on the slicing path of the shaped part to realize the manufacturing of the part. After the manufacturing is completed, the electron gun control system 10 controls the bypass wire feeding electron gun 1 to stop emitting the beam. Then, the wire feeding control system 20 controls the wire feeder 201 to stop feeding the wire. After the part cools to room temperature, the vacuum is broken and the shaped part is taken out.

Claims

1. A bypass wire feeding additive manufacturing system based on a field emission cathode, characterized in that, The system includes an electron gun (1) employing a field emission bulk cathode (102), which is located in a vacuum chamber (3). A forming substrate (301) is positioned at the electron beam exit direction of the electron gun (1). A wire feeder (201) is positioned between the electron gun (1) and the forming substrate (301). The wire feeder (201) is fixed on the side wall of the vacuum chamber (3). The electron gun (1) is connected to an electron gun control system (10) for controlling the opening, closing, beam current adjustment, electron beam focusing, deflection, and astigmatism correction functions of the electron gun (1). The wire feeder (201) is connected to a wire feeding control system (20) for transporting the metal wire (202) from the bypass to the forming substrate (301). The forming substrate (301) is connected to a motion control system (30) for controlling the movement direction of the forming substrate (301). The vacuum chamber (3) is connected to a vacuum control system (40) for controlling the vacuum level of the vacuum chamber (3). The electron gun (1) includes a cathode base (101), a field emission bulk cathode (102), a grid (103), an anode (104), a dissipation coil (105), a deflection coil (106), and a focusing coil (107) that are coaxially mounted from top to bottom. The field emission bulk cathode (102) is vertically arranged on the central axis of the cathode base (101) on the side facing the anode (104). The field emission bulk cathode (102) is a bulk graphene field emission cathode or a bulk graphene / carbon nanotube composite field emission cathode. The bulk graphene field emission cathode was prepared by cold pressing high-quality graphene; the bulk graphene / carbon nanotube composite field emission cathode was prepared by cold pressing a mixture of carbon nanotubes and high-quality graphene. 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 bypass wire feeding additive manufacturing system based on a field emission cathode according to claim 1, characterized in that, The negative high voltage applied to the field emission block cathode (102) is 30kV-60kV, the negative high voltage applied to the grid (103) is 0kV-5kV lower than that of the cathode base (101), the anode (104) is grounded, and the vacuum chamber (3) is grounded.

3. The bypass wire feeding additive manufacturing system based on a field emission cathode according to claim 1, characterized in that, The electron gun (1) uses bypass wire feeding with a wire feeding angle of 0° to 45°.

4. The bypass wire feeding additive manufacturing system based on a field emission cathode according to claim 1, characterized in that, A three-dimensional motion platform is provided at the bottom of the molding substrate (301), and the motion control system (30) is connected to the three-dimensional motion platform to control the movement of the three-dimensional motion platform.

5. The bypass wire feeding additive manufacturing system based on a field emission cathode according to claim 4, characterized in that, The motion control system (30) controls the movement of the three-dimensional motion platform based on the slice path of the shaped part.

6. The bypass wire feeding additive manufacturing system based on a field emission cathode according to claim 1, characterized in that, The field emission bulk cathode (102) has a height of 10mm-15mm, a width of 2mm-4mm, a thickness of 300μm-500μm, and an emission current of 0mA-20mA.

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