A wire bundle coaxial fusing filament additive manufacturing apparatus based on a field emission cathode

Abstract

This invention provides a coaxial field emission cathode (FET) based filament additive manufacturing equipment, comprising a coaxial FET electron gun, a three-dimensional motion platform, and a control system disposed in a vacuum chamber. The FET electron gun is positioned above the three-dimensional motion platform, with its outlet facing the forming substrate on the platform. The control system is connected to the vacuum chamber, the FET electron gun, and the three-dimensional motion platform to control the filament feed rate, emission current, and beam size of the FET electron gun, as well as the direction of motion of the three-dimensional motion platform and the vacuum level in the vacuum chamber. The additive manufacturing equipment of this invention has a simple structure, is easy to control, and produces high-quality formed parts.

Description

Technical Field

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

[0002] Compared with 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 machinery. Currently, common electron beam fusion additive manufacturing equipment mainly includes bypass wire feeding devices based on hot cathode electron guns and coaxial wire bundle additive manufacturing equipment based on cold cathode gas discharge electron guns.

[0003] In existing technologies, electron beam bypass wire feeding additive manufacturing equipment based on hot cathodes suffers from problems such as scanning directionality, defocusing sensitivity, and uneven heating. In actual molding, a four-axis motion mechanism (three-axis motion plus a rotary mechanism) needs to be designed to achieve part forming. Compared with the control system of three-axis motion, the control system of four-axis motion is inevitably more difficult.

[0004] The coaxial additive manufacturing device based on a cold cathode gas discharge electron gun solves the problems of scanning directionality, defocusing sensitivity, and uneven heating in hot cathode bypass wire feeding, and realizes the "bridging" transition of metal droplets. However, since the electron gun requires cooling water and gas passages, additional mechanical structures need to be designed in the additive manufacturing equipment to ensure the smooth flow of these passages, which increases the complexity of the mechanical structure and control system. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a coaxial fused wire additive manufacturing equipment based on a field emission cathode, which has a simple structure, is easy to control, and produces large-sized molded parts.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a coaxial field emission cathode-based filament additive manufacturing equipment, comprising a coaxial field emission cathode electron gun, a three-dimensional motion platform, and a control system disposed in a vacuum chamber. The coaxial field emission cathode electron gun is disposed above the three-dimensional motion platform, with its outlet facing the forming substrate on the three-dimensional motion platform. The control system is connected to the vacuum chamber, the coaxial field emission cathode electron gun, and the three-dimensional motion platform to control the filament feed rate, emission current, and beam size of the coaxial field emission cathode electron gun, control the motion direction of the three-dimensional motion platform, and control the vacuum level in the vacuum chamber.

[0007] The coaxial field emission cathode electron gun uses a ring-shaped bulk field emission cathode.

[0008] Furthermore, the control system includes a filament coaxial electron gun control system, a forming control system, and a vacuum control system. The filament coaxial electron gun control system is connected to the filament coaxial field emission cathode electron gun to control the filament feed amount and the size of the emission current beam spot of the filament coaxial field emission cathode electron gun. The forming control system is connected to the three-dimensional motion platform to control the motion direction of the three-dimensional motion platform. The vacuum control system is connected to the vacuum chamber to control the vacuum level in the vacuum chamber.

[0009] Furthermore, the coaxial field emission cathode electron gun includes a wire guide head, a wire guide nozzle, a wire feeder, and a cavity. The cavity consists of an annular bulk field emission cathode, a grid, an anode, and a focusing coil arranged coaxially from top to bottom along the axis. The focusing coil is located at the outlet of the anode. The wire guide head has a frustum-shaped structure, with the smaller diameter end of the wire guide head passing through the annular bulk field emission cathode and extending into the cavity, and being coaxially arranged with the annular bulk field emission cathode. The wire guide nozzle is located inside the wire guide head. The wire feeder is used to feed the metal wire into the cavity through the wire guide nozzle and the wire guide head.

[0010] Furthermore, the annular bulk field emission cathode includes a cathode base and an annular array cathode. The annular array cathode is connected around the holes in the cathode base and is positioned facing the anode. The distance between the bottom end face of the annular array 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. The cathode base is connected to a negative high-voltage power supply interface, and the anode is grounded.

[0011] Furthermore, the coaxial electron gun control system includes a wire feeding control system, a high-voltage power supply control system, and a focusing control system. The wire feeding control system is connected to the wire feeder to control the wire feeder to feed the metal wire into the coaxial field emission cathode electron gun. The output of the high-voltage power supply control system is connected to the cathode base, grid, and anode via a high-voltage cable to control the emission current by adjusting the grid voltage. The focusing control system is connected to the focusing coil and the high-voltage power supply control system via a control circuit to adjust the focusing coil current by reading the cathode and grid voltage signals to achieve beam spot size control.

[0012] Furthermore, the forming control system includes a motion control system, which is connected to a three-dimensional motion platform to control the motion of the three-dimensional motion platform based on the slicing path of the forming part to achieve additive manufacturing of the part.

[0013] Furthermore, a vacuum gauge and a vacuum pump assembly are installed in the vacuum chamber. The vacuum control system is connected to the vacuum gauge and the vacuum pump assembly to detect the vacuum level of the vacuum chamber through the vacuum gauge and to control the vacuum level of the vacuum chamber through the vacuum pump assembly.

[0014] Furthermore, the three-dimensional motion platform includes the X-stage, Y-stage, and Z-stage.

[0015] Furthermore, the annular array cathode is a regular N-sided array cathode composed of bulk graphene field emission cathodes or bulk graphene / carbon nanotube composite field emission cathodes, where N>3. N bulk field emission cathodes are connected along their length to obtain the regular N-sided array cathode. The bulk graphene field emission cathode is formed by cold pressing high-quality graphene; the bulk graphene / carbon nanotube composite field emission cathode is formed by cold pressing a mixture 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. 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 5mA-10mA.

[0016] Furthermore, the negative high voltage range of the ring-shaped 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 ring-shaped bulk field emission cathode.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] This invention provides a coaxial filament additive manufacturing apparatus based on a field emission cathode, comprising a coaxial field emission cathode electron gun. Compared with bypass filament feeding additive manufacturing equipment, the use of a three-axis motion control mechanism reduces the complexity of the motion control system during part forming. Furthermore, since the electron gun structure itself is coaxial, a complex alignment device is not required. Compared with coaxial filament additive manufacturing equipment based on a cold cathode gas discharge electron gun, the use of a field emission cathode eliminates the need for additional cooling water and gas passages in the electron gun structure, significantly simplifying the mechanical structure and control system complexity of the forming equipment. This results in a smaller electron gun structure and, under the same vacuum chamber size, a larger formed part size can be obtained. The coaxial filament additive manufacturing apparatus proposed in this invention has the advantages of simple structure and large formed part size.

[0019] Furthermore, the present invention provides a coaxial filament additive manufacturing equipment based on a field emission cathode. Compared with existing coaxial filament additive manufacturing equipment, the electron gun acceleration voltage of the present invention is 30-60kV, which will result in a very deep molten pool during the forming process, thus helping to improve the quality of the formed parts.

[0020] Furthermore, the present invention provides a coaxial fused wire additive manufacturing device based on a field emission cathode. Since there is no additional water cooling or gas passage connection to the vacuum chamber, the vacuum control system is also easier to control to maintain the vacuum level.

[0021] Furthermore, this invention adjusts the beam current by reading the gate voltage signal, eliminating the need for a complex feedback control module and making the control more efficient. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a coaxial fused wire additive manufacturing equipment based on a field emission cathode according to the present invention.

[0023] Figure 2 This is a schematic diagram of the annular array cathode of the present invention.

[0024] In the attached diagram: 1-Electron gun; 101-Wire guide head; 102-Wire guide nozzle; 103-Cathode base; 104-Grid; 105-Anode; 106-Focusing coil; 107-Annular array cathode; 108-Insulating ceramic; 109-Wire feeder; 110-Metal wire;

[0025] 2-Control system; 20-Filament coaxial electron gun control system; 21-Forming control system; 22-Vacuum control system; 201-Filament feeding control system; 202-High voltage power supply control system; 203-Focusing control system; 210-Motion control system; 220-Vacuum gauge; 221-Vacuum pump assembly; 211-X stage; 212-Y stage; 213-Z stage; 214-Forming substrate;

[0026] 3-Vacuum chamber. Detailed Implementation

[0027] 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.

[0028] like Figure 1As shown, this invention provides a coaxial filament additive manufacturing apparatus based on a field emission cathode, comprising a vacuum chamber 3, which is grounded, a three-dimensional motion platform disposed within the vacuum chamber 3, a forming substrate 214 disposed on the three-dimensional motion platform, a coaxial field emission cathode electron gun 1 disposed above the three-dimensional motion platform within the vacuum chamber 3, with the outlet of the coaxial field emission cathode electron gun 1 facing the forming substrate 214, and the coaxial field emission cathode electron gun 1, the vacuum chamber 3, and the three-dimensional motion platform are all electrically connected to a control system 2 to control the filament feed rate and emission current beam size of the coaxial field emission cathode electron gun 1, control the movement direction of the three-dimensional motion platform, and control the vacuum level in the vacuum chamber 3.

[0029] The coaxial field emission cathode electron gun 1 includes: a wire guide head 101, a wire guide nozzle 102, an annular bulk field emission cathode, a grid 104, an anode 105, a focusing coil 106, an insulating ceramic 108, and a wire feeder 109. The annular bulk field emission cathode, grid 104, anode 105, and focusing coil 106 are coaxially arranged from top to bottom along an axis, and the cathode base 103, grid 104, anode 105, and focusing coil 106 are connected by the insulating ceramic 108 to form a [missing information - likely a specific structure or feature]. The cavity contains a focusing coil 106 located at the beam exit of the anode 105 to focus the electron beam into a high-energy-density electron beam spot. The guide wire head 101 has a frustum-shaped structure. The smaller diameter end of the guide wire head 101 passes through the annular bulk field emission cathode and extends into the cavity, and is coaxially arranged with the annular bulk field emission cathode. The guide wire nozzle 102 is located inside the guide wire head 101. The wire feeder 109 feeds the metal wire 110 into the cavity through the guide wire nozzle 102 and the guide wire head 101, achieving coaxial wire feeding.

[0030] The annular block field emission cathode includes a cathode base 103 and an annular array cathode 107. The annular array cathode 107 is connected around the holes of the cathode base 103 and is positioned towards the anode 105. The cathode base 103 is connected to a negative high-voltage power supply interface, and the anode 105 is grounded.

[0031] Preferably, the annular array cathode 107 is a regular N-sided array cathode composed of bulk graphene field emission cathodes or bulk graphene / carbon nanotube composite field emission cathodes (N>3), and N bulk field emission cathodes are connected along the length direction to obtain a regular N-sided array cathode.

[0032] 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. 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 5mA-10mA.

[0033] Preferably, the negative high voltage range of the annular bulk field emission cathode is 30kV-60kV, and the negative high voltage of the gate 104 is 0-5kV lower than that of the annular bulk field emission cathode.

[0034] Preferably, the anode 105 and the gate 104 are membrane aperture electrodes; the distance between the bottom end face of the annular array cathode 107 and the top end face of the gate is 0.2mm-1mm, and the distance between the gate 104 and the anode 105 is 5mm-10mm; the focusing coil 106 has 2000 turns and a focusing current of 0A-2A, and the beam size is controlled by controlling the focusing current; to avoid electric field breakdown, the insulating ceramic 108 has a withstand voltage of 60kV; the guide wire head 101 is an insulating ceramic component with a withstand voltage of up to 60kV.

[0035] The control system 2 includes a wire bundle coaxial electron gun control system 20, a forming control system 21, and a vacuum control system 22. The wire bundle coaxial electron gun control system 20 includes a wire feeding control system 201, a high-voltage power supply control system 202, and a focusing control system 203. The wire feeding control system 201 is connected to the wire feeder 109 to control the wire feeder 109 to feed the metal wire 110 into the wire bundle coaxial field emission cathode electron gun 1. The output terminal of the high-voltage power supply control system 202 is connected to the cathode base 103, the grid 104, and the anode 105 through a high-voltage cable to control the emission current by adjusting the grid voltage. The focusing control system 203 is connected to the focusing coil 106 and the high-voltage power supply control system 202 through a control circuit to adjust the focusing coil current by reading the cathode and grid voltage signals to achieve beam spot size control.

[0036] The molding control system 21 includes a motion control system 210, which is connected to a three-dimensional motion platform to control the motion of the three-dimensional motion platform based on the slicing path of the molded part to achieve additive manufacturing of the part.

[0037] The three-dimensional motion platform includes X worktable 211, Y worktable 212, and Z worktable 213.

[0038] The vacuum control system 22 is connected to the vacuum gauge 220 and the vacuum pump group 221 to detect the vacuum level of the vacuum chamber 3 through the vacuum gauge 220 and control the vacuum pump group 221 to evacuate the vacuum chamber 3 to achieve the required vacuum level.

[0039] Example 1

[0040] When using the coaxial fused wire additive manufacturing equipment based on a field emission cathode according to the present invention, the specific usage is as follows:

[0041] 1. Assembly of the filament-tethered coaxial field emission cathode electron gun:

[0042] A single bulk field emission cathode is selected with a height of 10 mm, a thickness of 300 μm, and a width of 3 mm. The cathode base diameter is 54 mm. A decagonal ring cathode is formed by assembling bulk graphene cathodes or bulk graphene / carbon nanotube composite cathodes, and then connected to the cathode base to obtain a ring-shaped bulk field emission cathode. Figure 2 As shown;

[0043] The annular bulk field emission cathode, grid 104, anode 105, and focusing coil 106 are arranged coaxially from top to bottom along the axis. The cathode base 103, grid 104, anode 105, and focusing coil 106 are connected by insulating ceramic 108 to form a cavity. The wire guide head 101 passes through the annular bulk field emission cathode and extends into the cavity and is coaxially arranged with the annular bulk field emission cathode. The wire guide nozzle 102 is disposed inside the wire guide head 101. The wire feeder 109 feeds the metal wire 110 into the cavity through the wire guide nozzle 102 and the wire guide head 101 to achieve coaxial wire feeding.

[0044] 2. Activate the filament coaxial electron gun control system 20, the molding control system 21, and the vacuum control system 22. The vacuum control system 22 controls the vacuum chamber 3 to reach the required vacuum level. The filament coaxial electron gun control system 20 controls the filament coaxial field emission cathode electron gun 1 to perform additive manufacturing on the molding substrate 214. The molding control system 21 controls the movement of the three-dimensional motion platform to drive the molding substrate 214 on it to move, thereby realizing the slicing path based on the molded part.

Claims

1. A coaxial fused wire additive manufacturing apparatus based on a field emission cathode, characterized in that, The system includes a filament coaxial field emission cathode electron gun (1) installed in a vacuum chamber (3), a three-dimensional motion platform, and a control system (2). The filament coaxial field emission cathode electron gun (1) is positioned above the three-dimensional motion platform, with its outlet facing the molded substrate (214) on the three-dimensional motion platform. The control system (2) is connected to the vacuum chamber (3), the filament coaxial field emission cathode electron gun (1), and the three-dimensional motion platform to control the filament feed amount, emission current, and beam size of the filament coaxial field emission cathode electron gun (1), control the motion direction of the three-dimensional motion platform, and control the vacuum level in the vacuum chamber (3). The filament coaxial field emission cathode electron gun (1) adopts a ring-shaped bulk field emission cathode. The control system (2) includes a filament coaxial electron gun control system (20), a forming control system (21), and a vacuum control system (22). The filament coaxial electron gun control system (20) is connected to the filament coaxial field emission cathode electron gun (1) to control the filament feed amount, emission current, and beam size of the filament coaxial field emission cathode electron gun (1). The forming control system (21) is connected to the three-dimensional motion platform to control the motion direction of the three-dimensional motion platform. The vacuum control system (22) is connected to the vacuum chamber (3) to control the vacuum level in the vacuum chamber (3). The wire bundle coaxial electron gun control system (20) includes a wire feeding control system (201), a high-voltage power supply control system (202), and a focusing control system (203). The wire feeding control system (201) is connected to the wire feeder (109) to control the wire feeder (109) to feed the metal wire (110) into the wire bundle coaxial field emission cathode electron gun (1). The output end of the high-voltage power supply control system (202) is connected to the cathode base (103), the grid (104), and the anode (105) through a high-voltage cable to control the emission current by adjusting the grid voltage. The focusing control system (203) is connected to the focusing coil (106) and the high-voltage power supply control system (202) through a control circuit to adjust the focusing coil current by reading the cathode and grid voltage signals to achieve beam spot size control. The annular bulk field emission cathode includes a cathode base (103) and an annular array cathode (107). The annular array cathode (107) is connected around the holes of the cathode base (103) and is positioned facing the anode (105). The distance between the bottom end face of the annular array cathode (107) and the top end face of the gate is 0.2mm-1mm. The distance between the gate (104) and the anode (105) is 5mm-10mm. The cathode base (103) is connected to the negative high voltage power supply interface, and the anode (105) is grounded. The annular array cathode (107) is a regular N-sided array cathode composed of bulk graphene field emission cathodes or bulk graphene / carbon nanotube composite field emission cathodes, where N>3. The regular N-sided array cathode is obtained by connecting N bulk field emission cathodes along the length direction. The bulk graphene field emission cathode is obtained by cold pressing high-quality graphene. The bulk graphene / carbon nanotube composite field emission cathode is obtained 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. 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 5mA-10mA.

2. The coaxial fused wire additive manufacturing equipment based on a field emission cathode according to claim 1, characterized in that, The wire bundle coaxial field emission cathode electron gun (1) includes a wire guide head (101), a wire guide nozzle (102), a wire feeder (109), and a cavity. The cavity consists of an annular bulk field emission cathode, a grid (104), an anode (105), and a focusing coil (106) arranged coaxially from top to bottom along the axis. The focusing coil (106) is located at the outlet of the anode (105). The wire guide head (101) has a frustum structure. The smaller diameter end of the wire guide head (101) passes through the annular bulk field emission cathode and extends into the cavity, and is coaxially arranged with the annular bulk field emission cathode. The wire guide nozzle (102) is located inside the wire guide head (101). The wire feeder (109) is used to feed the metal wire (110) into the cavity through the wire guide nozzle (102) and the wire guide head (101).

3. The coaxial fused wire additive manufacturing equipment based on a field emission cathode according to claim 1, characterized in that, The molding control system (21) includes a motion control system (210), which is connected to a three-dimensional motion platform to control the motion of the three-dimensional motion platform based on the slice path of the molded part to realize the additive manufacturing of the part.

4. The coaxial fused wire additive manufacturing equipment based on a field emission cathode according to claim 1, characterized in that, A vacuum gauge (220) and a vacuum pump group (221) are installed in the vacuum chamber (3). The vacuum control system (22) is connected to the vacuum gauge (220) and the vacuum pump group (221) to detect the vacuum degree of the vacuum chamber (3) through the vacuum gauge (220) and control the vacuum pump group (221) to control the vacuum degree of the vacuum chamber (3).

5. The coaxial fused wire additive manufacturing equipment based on a field emission cathode according to claim 1, characterized in that, The three-dimensional motion platform includes the X worktable (211), the Y worktable (212), and the Z worktable (213).

6. The coaxial fused wire additive manufacturing equipment based on a field emission cathode according to claim 1, characterized in that, The negative high voltage range of the ring block field emission cathode is 30kV-60kV, and the negative high voltage of the gate (104) is 0-5kV lower than that of the ring block field emission cathode.

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