Microgravity metal fuse additive melt directional transfer and liquid bridge transition maintenance device and method

Abstract

The present invention provides a microgravity metal fuse additive melt directional transfer and liquid bridge transition maintenance device and method. A forming substrate is mounted on a multi-axis motion platform; the multi-axis motion platform customizes a three-dimensional motion trajectory based on three-dimensional data used in additive manufacturing. Two current clamps are fixed between the metal wire and the forming substrate, respectively. A DC power supply forms a current path between the metal wire and the forming substrate, and an ammeter is connected in series in the current path. Electromagnetic coils are arranged circumferentially around the metal wire, and magnetic rods are connected to the electromagnetic coils and distributed symmetrically on both sides of the end of the metal wire. An AC power supply provides an alternating electric field for the electromagnetic coils. A wire feeding mechanism and a drive motor feed the metal wire into the range of the laser light source at a constant speed. The laser acts on the forming substrate, forming a liquid molten pool on the forming substrate. The metal wire and the forming substrate form a liquid bridge connection pattern through the liquid melt. This invention can reduce porosity defects in components.

Description

Technical Field

[0001] The present invention relates to the field of laser additive manufacturing in a space microgravity environment, and in particular to a device and method for directional transfer of a metal fuse additive melt and liquid bridge transition. Background Art

[0002] Metal fused filament additive manufacturing under microgravity is one of the most effective ways to manufacture in situ in space. -2 g~10 -5 The flow behavior caused by gravity virtually disappears. Therefore, the flow behavior of fluids in microgravity differs significantly from that in terrestrial environments. In fused filament additive manufacturing (FAM), the method by which the metal wire enters the substrate molten pool is a key factor affecting formability, directly determining the surface morphology and mechanical properties of the finished part. In terrestrial FAM, the transition between the wire and the molten pool occurs primarily through liquid bridge and droplet transitions. When the filler metal wire transitions into the molten pool in the form of molten droplets, process stability is significantly disrupted, resulting in poor forming quality. Furthermore, in the absence of gravity, surface tension becomes the primary driving force for droplet transfer. Unconstrained by gravity, droplets may creep back along the wire, preventing them from being transported to the molten pool in a targeted manner. Furthermore, this creep can clog the wire feed nozzle, leading to forming failure. In the liquid bridge transition mode, melting occurs within a very small distance from the wire tip, allowing the wire to continuously enter the molten pool through the melt. Furthermore, in the liquid bridge transition mode, the melt entering the molten pool does not cause additional impact on the molten pool, ensuring the stability of the molten pool and the forming process. Therefore, how to maintain the liquid bridge transition mode between the metal wire and the molten pool and maintain the stability of the liquid bridge in the fused filament additive process under a microgravity environment is a key factor in determining the success and quality of the forming.

[0003] Porosity is an inevitable defect within additively manufactured components due to factors such as gas entrapment or the inability of gases to escape from the melt pool during the manufacturing process. However, in a microgravity environment, the absence of gravity restrains the flow, causing gases within the melt pool to remain trapped within the melt and unable to escape easily. Porosity is one of the most common defects in additively manufactured components, causing stress concentration and a sharp decline in component performance. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems encountered in the additive manufacturing of fused metal in a microgravity environment, the present invention provides a microgravity metal fused additive melt directional transfer and liquid bridge transition maintenance device and method, which utilizes the recoil pressure generated by metal vapor, the pre-pressure between the metal wire and the forming substrate, and the dynamic wire feeding method to effectively promote the directional transport of the metal melt to the molten pool under the condition of no gravity constraint. At the same time, the electromagnetic force and Lorentz force generated by the alternating magnetic field and the constant electric field are used to form an electromagnetic stirring effect inside the molten pool, effectively discharging the gas in the molten pool during the process, reducing the porosity defects of the component, and further promoting the uniformity of the solidification structure and the refinement of the grains.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device includes a multi-axis motion platform, a forming substrate, an industrial control system, a laser source, a metal wire reel, a wire feeding mechanism and a drive motor, an insulating sleeve, a coaxial wire feeding and air feeding tube, a metal wire angle adjustment structure, a metal wire pressing mechanism, an air tube heating device, a DC power supply, a current clamp, an ammeter, a protective gas, a precision gas flow meter, an electromagnetic coil, a magnetic head, an electromagnetic coil fixing bracket, and an AC power supply; the forming substrate is installed on the multi-axis motion platform; the multi-axis motion platform customizes the three-dimensional motion trajectory path according to the three-dimensional data in additive manufacturing; two current clamps are respectively fixed on the metal wire and the forming substrate, and a current path is formed between the metal wire and the forming substrate through a DC power supply, and at the same time An ammeter is connected in series in the current path; an electromagnetic coil is arranged circumferentially around the metal wire, and magnetic rods are connected to the electromagnetic coils and distributed symmetrically on both sides of the end of the metal wire. The electromagnetic coils are fixedly connected to the coaxial wire feeding and air feeding pipes through an electromagnetic coil fixing frame; an AC power supply provides an alternating electric field to the electromagnetic coils, thereby generating an alternating magnetic field near the end of the metal wire; a wire feeding mechanism and a drive motor feed the metal wire into the range of the light spot emitted by the laser source at a constant quantity and speed; the laser emitted by the laser source acts within the range of the end of the metal wire, forming a liquid melt at the end of the metal wire; at the same time, the laser acts on the forming substrate, forming a liquid molten pool on the forming substrate; the metal wire and the forming substrate form a liquid bridge connection mode through the liquid melt.

[0007] Furthermore, during operation, the laser source and the metal wire are stationary.

[0008] Furthermore, a shielding gas is blown coaxially with the metal wire.

[0009] Furthermore, the shielding gas is an inert gas, which is ejected through a precision gas flow meter and a coaxial wire feeding and air feeding pipe; the coaxial wire feeding and air feeding pipe is heated by a gas pipe heating device, and the coaxial wire feeding and air feeding pipe transfers heat to the metal wire and the shielding gas through heat conduction, thereby achieving heating of the shielding gas and the metal wire.

[0010] Furthermore, the metal wire is stainless steel wire, aluminum alloy wire, titanium alloy wire, flux-cored welding wire, high / medium entropy alloy, amorphous alloy wire or metal composite material wire.

[0011] Furthermore, the metal wire angle adjustment structure adjusts the angle between the metal wire and the horizontal direction, and the angle range is 0-60 degrees.

[0012] Furthermore, the end of the metal wire is kept in contact with the forming substrate, and a pre-compression force is applied between the end of the metal wire and the forming substrate by the metal wire pressing mechanism to ensure good contact between the end of the metal wire and the forming substrate.

[0013] Furthermore, the industrial control system uses an ammeter to detect whether a closed current path is formed between the forming substrate and the metal wire; when the current on the ammeter is 0A, it indicates that the liquid bridge between the metal wire and the forming substrate is disconnected; in the working state where the liquid bridge is disconnected, the industrial control system increases the wire feeding length through the wire feeding mechanism and the drive motor; when there is a closed circuit in the path, the industrial control system adjusts the wire feeding speed to the normal process to ensure that the forming substrate and the metal wire maintain a stable liquid bridge connection.

[0014] The present invention also provides a method for directional transfer of metal fuse additive melt and liquid bridge transition maintenance in microgravity, comprising the following steps:

[0015] Step S1, adjusting the relative position of the laser source and the metal wire and the initial processing position of the forming substrate, forming a pre-pressure between the forming substrate and the metal wire by the metal wire pressing mechanism to ensure good contact between the metal wire and the forming substrate;

[0016] Step S2: Slice the data according to the three-dimensional model to be constructed, and ensure that the wire feeding is always parallel to the forming direction and kept at the front end of the forming direction through the multi-axis motion platform; ensure that the metal wire is in contact with the forming substrate;

[0017] Step S3: activating the shielding gas, laser source, DC power supply, AC power supply, wire feeding mechanism, and drive motor in sequence. After the metal wire contacts the forming substrate, a current path is generated between the metal wire and the forming substrate. The current is used as a control signal to start additive manufacturing according to the slice data of the three-dimensional model.

[0018] Step S4: During the processing, the industrial control system detects the current generated between the metal wire and the forming substrate. When the current is zero, the dynamic wire feeding amount program is started to increase the wire feeding amount so that the metal liquid bridge connection between the metal wire and the forming substrate is achieved. When the current value recovers, the dynamic wire feeding amount program is adjusted to the normal wire feeding amount process so that a stable liquid bridge connection is maintained between the metal wire and the forming substrate.

[0019] Step S5: After the current layer is processed, the wire feeding mechanism and the drive motor, DC power supply, laser source, and shielding gas are sequentially turned off; at the same time, the metal wire pressing mechanism moves upward to release the pre-pressure between the metal wire and the forming substrate, and the forming substrate is moved to the initial position of the next trajectory by the multi-axis motion platform;

[0020] Step S6: Repeat steps S1, S2, S3, S4 and S5 until the entire three-dimensional component is processed.

[0021] Furthermore, the flow rate of the protective gas is 0L / min~25L / min; the laser source is used to output pulsed laser or continuous laser, its maximum output power is 4000W, the pulse frequency is 10Hz~1000HZ, the laser pulse width is 2~50ms, and its scanning speed is 50mm / min~2000mm / min; the maximum output current of the DC power supply is 400A.

[0022] Beneficial effects:

[0023] 1. The present invention uses a laser source as its energy source. By adjusting the relative positions of the laser source and the metal wire and the initial processing position of the forming substrate, the end of the metal wire and the forming substrate are melted simultaneously. The recoil steam pressure generated by the instantaneous high energy is used to promote the directional transfer of the liquid melt generated by the melting of the metal wire end to the molten pool.

[0024] 2. The present invention uses the current of the closed circuit between the metal wire and the forming substrate as the control signal and adopts a closed-loop control method to dynamically adjust the wire feeding speed and length to ensure the stability of the liquid bridge formed between the metal wire and the molten pool.

[0025] 3. The present invention applies a forming pre-compression force between the end of the metal wire and the forming substrate. The pre-compression force ensures good bonding between the liquid melt at the end of the metal wire and the forming substrate.

[0026] 4. The present invention forms an alternating magnetic field around the molten pool. Under the action of the electric and magnetic fields, electromagnetic and Lorentz forces are generated within the molten pool, which dynamically stirs the molten pool and accelerates the floating of bubbles within the molten pool. This solves the problem of bubble overflow in the molten pool under microgravity, greatly reduces the internal porosity defects of metal additively manufactured components under microgravity, and improves the performance and printing quality of the formed parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device of the present invention.

[0028] Among them, the accompanying drawings are marked as: multi-axis motion platform 1, forming substrate 2, industrial control system 3, laser source 4, metal wire 5, metal wire reel 6, wire feeding mechanism and driving motor 7, insulating sleeve 8, coaxial wire feeding and air feeding pipe 9, metal wire angle adjustment structure 10, metal wire pressing mechanism 11, air pipe heating device 12, DC power supply 13, current clamp 14, ammeter 15, protective gas 16, precision gas flow meter 17, electromagnetic coil 18, magnetic head 19, electromagnetic coil fixing frame 20, AC power supply 21, liquid melt 22. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0030] like Figure 1 As shown, the microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device of the present invention includes a multi-axis motion platform 1, a forming substrate 2, an industrial control system 3, a laser source 4, a metal wire 5, a metal wire reel 6, a wire feeding mechanism and a driving motor 7, an insulating sleeve 8, a coaxial wire feeding and air feeding pipe 9, a metal wire angle adjustment structure 10, a metal wire pressing mechanism 11, an air pipe heating device 12, a DC power supply 13, a current clamp 14, an ammeter 15, a protective gas 16, a precision gas flow meter 17, an electromagnetic coil 18, a magnetic head 19, an electromagnetic coil fixing frame 20, and an AC power supply 21.

[0031] The forming substrate 2 is mounted on a multi-axis motion platform 1, which enables multi-degree-of-freedom motion of the forming substrate 2 in space. The multi-axis motion platform 1 customizes the three-dimensional motion trajectory based on the three-dimensional data used in additive manufacturing. A laser source 4 is fixed above the forming substrate 2, allowing the beam emitted by the laser source 4 to illuminate the upper surface of the forming substrate 2. The energy accumulated by the laser source 4 on the forming substrate 2 forms a molten pool of liquid metal within the laser spot. A metal wire 5, a wire feed mechanism and drive motor 7, and a coaxial wire and air feed pipe 9 are mounted laterally to the laser source 4 via a wire angle adjustment structure 10. The wire feed mechanism and drive motor 7 drive the metal wire 5 through the coaxial wire and air feed pipe 9 into the laser spot range of the laser source 4, where it contacts the forming substrate 2. A wire reel 6 is fixed to the wire feed mechanism and drive motor 7 at the inlet end of the wire 5, providing a continuous supply of metal wire 5 for the present invention.

[0032] There are two current clamps 14, one of which is fixed to the forming base plate 2, while the other maintains contact with the metal wire 5 via a contact piece. A current path is formed between the metal wire 5 and the forming base plate 2 via a DC power supply 13, and an ammeter 15 is connected in series in the current path. An insulating sleeve 8 is coaxially installed inside the coaxial wire and air feed tube 9, between the metal wire 5 and the coaxial wire feed tube 9. The function of the insulating sleeve 8 is to insulate the electric field generated by the DC power supply 13 from components such as the metal wire angle adjustment structure 10, the metal wire clamping mechanism 11, the air pipe heating device 12, and the electromagnetic coil fixing frame 20.

[0033] Electromagnetic coils 18 are arranged circumferentially around the metal wire 5. Magnetic rods 19 are connected to the electromagnetic coils 18 and are symmetrically positioned on either side of the ends of the metal wire 5. The electromagnetic coils 18 are fixedly connected to the coaxial wire and air feed tube 9 via an electromagnetic coil mounting bracket 20. An AC power supply 21 provides an alternating electric field to the electromagnetic coils 18, thereby generating an alternating magnetic field near the ends of the metal wire 5.

[0034] The present invention can realize additive manufacturing of metal fuses in a microgravity environment. During the additive manufacturing process, the laser source 4 and the metal wire 5 are fixed, and multi-degree-of-freedom movement in space is achieved through the multi-axis motion platform 1.

[0035] The present invention is designed to blow the shielding gas 16 coaxially with the metal wire 5. The shielding gas 16 mainly plays two roles: (1) the shielding gas blown coaxially with the metal wire 5 can cover the liquid metal pool on the forming substrate 2 to prevent the liquid metal pool from being oxidized; (2) the shielding gas blown coaxially with the metal wire 5 generates a thrust along the wire axis on the end liquid melt 22 of the metal wire 5, thereby promoting the directional transfer of the end liquid melt 22 to the liquid metal pool on the forming substrate 2, and reducing the problem of the end liquid melt 22 creeping back along the wire.

[0036] Preferably, the shielding gas 16 is an inert gas, and a precision gas flow meter 17 is installed on the air flow path between the shielding gas 16 and the coaxial wire feeding air supply pipe 9, and the shielding gas 16 is coaxially ejected through the precision gas flow meter 17 and the coaxial wire feeding air supply pipe 9.

[0037] The gas pipe heating device 12 is mounted on the coaxial wire feeding gas pipe 9. The gas pipe heating device 12 can heat the coaxial wire feeding gas pipe 9. When the shielding gas 16 and the metal wire 5 pass through the heated coaxial wire feeding gas pipe 9, their temperature increases. The gas pipe heating device 12 can heat the shielding gas 16 and the metal wire 5. Heating the shielding gas 16 can reduce the convective cooling effect of the shielding gas 16 on the liquid metal molten pool formed on the forming substrate 2, thereby preventing the molten pool temperature from being too low, resulting in discontinuous fusion and reduced laser energy utilization. Heating the metal wire 5 can increase the temperature of the metal wire at a certain position away from the end, thereby reducing the temperature gradient between the solid metal wire 5 and the liquid melt 22 at the end of the metal wire, thereby reducing the surface tension effect on the liquid melt 22 creeping back along the wire.

[0038] Preferably, the metal wire 5 includes, but is not limited to, stainless steel wire, aluminum alloy wire, titanium alloy wire, flux-cored welding wire, high / medium entropy alloy, amorphous alloy wire, and metal composite wire. The angle between the metal wire 5 and the horizontal direction is adjusted by the metal wire angle adjustment structure 10, preferably within a range of 0° to 60°. The wire feeding mechanism and drive motor 7 can deliver the metal wire 5 at a constant speed and in a quantitative manner to the range of the laser light source 4.

[0039] Preferably, the wire feeding mechanism and the drive motor 7 can achieve quantitative adjustment of the wire feeding speed. In the present invention, the end of the metal wire 5 is kept in contact with the forming substrate 2. The metal wire pressing mechanism 11 is installed above the coaxial wire feeding and air feeding tube 9. The metal wire pressing mechanism 11 applies a pre-compression force between the end of the metal wire 5 and the forming substrate 2 to ensure good contact between the end of the metal wire 5 and the forming substrate 2. Preferably, the wire feeding mechanism and the drive motor 7 are used to achieve metal wire feeding with a wire diameter of 0.1mm to 10mm.

[0040] Preferably, the laser light emitted by the laser source 4 acts within the end region of the metal wire 5, forming a liquid melt 22 at the end of the metal wire 5. Simultaneously, the laser light acts on the forming substrate 2, forming a liquid molten pool on the forming substrate 2. The metal wire 5 and the forming substrate 2 are connected in a liquid bridge mode via the liquid melt 22.

[0041] Preferably, the industrial control system 3 can detect whether a closed current path is formed between the forming substrate 2 and the metal wire 5 using an ammeter 15. When the current measured by the ammeter 15 is 0A, the liquid bridge between the metal wire 5 and the forming substrate 2 is disconnected. When the liquid bridge is disconnected, the industrial control system 3 increases the wire feed length via the wire feed mechanism and the drive motor 7, ensuring a stable liquid bridge connection between the forming substrate 2 and the metal wire 5.

[0042] The present invention also provides a method for directional transfer of metal fuse additive melt and liquid bridge transition maintenance in microgravity, comprising the following steps:

[0043] Step S1, manufacturing preparation: adjusting the relative position of the laser and the metal wire 5 and the initial processing position of the forming substrate 2, and forming a pre-pressure between the forming substrate 2 and the metal wire 5 by the metal wire pressing mechanism 11 to ensure good contact between the metal wire 5 and the forming substrate 2;

[0044] Step S2, data preparation: Data slicing is performed according to the three-dimensional model to be constructed, and the multi-axis motion platform 1 is used to ensure that the wire 5 is always parallel to the forming direction and kept at the front end of the forming direction; and the metal wire 5 is ensured to be in contact with the forming substrate 2;

[0045] Step S3, starting processing: the shielding gas 16, the laser source 4, the DC power supply 13, the AC power supply 21, the wire feeding mechanism, and the drive motor 7 are sequentially started. After the metal wire 5 contacts the forming substrate 2, a current path is generated between the metal wire 5 and the forming substrate 2. The current generation is used as a control signal, i.e., processing is started after the current is generated, thereby starting additive processing according to the slice data of the three-dimensional model;

[0046] Step S4, in-process monitoring: During the processing, the industrial control system 3 detects the current generated between the metal wire 5 and the forming substrate 2. When the current is zero, the dynamic wire feeding amount program is started, and the wire feeding amount is increased to make the metal bridge between the metal wire and the forming substrate connected; when the current value recovers, the dynamic wire feeding amount program is adjusted to the normal wire feeding amount process, so that a stable liquid bridge connection is maintained between the metal wire and the forming substrate;

[0047] Step S5, completion of current layer processing: After completion of current layer processing, the wire feeding mechanism and drive motor 7, DC power supply 13, laser source 4, and shielding gas 16 are sequentially turned off; simultaneously, the metal wire pressing mechanism 11 moves upward, releasing the pre-pressure between the metal wire 5 and the forming substrate 2, and the multi-axis motion platform 1 moves the forming substrate 2 to the initial position of the next trajectory;

[0048] Step S6: Repeat steps S1, S2, S3, S4 and S5 until the entire three-dimensional component is processed.

[0049] Preferably, the flow rate of the protective gas 16 is 0 L / min to 25 L / min.

[0050] Preferably, the laser source 4 is used to output pulsed laser or continuous laser, with a maximum output power of 4000W, a pulse frequency of 10Hz~1000HZ, a laser pulse width of 2~50ms, and a scanning speed of 50mm / min~2000mm / min; the maximum output current of the DC power supply 13 is 400A.

Claims

1. Microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device, characterized in that: It includes a multi-axis motion platform, forming substrate, industrial control system, laser source, wire reel, wire feeding mechanism and drive motor, insulating sleeve, coaxial wire feeding and air feeding tube, wire angle adjustment structure, wire clamping mechanism, air tube heating device, DC power supply, current clamp, ammeter, shielding gas, precision gas flow meter, electromagnetic coil, magnetic head, electromagnetic coil fixing bracket, and AC power supply. The forming substrate is mounted on the multi-axis motion platform. The multi-axis motion platform customizes the 3D motion trajectory path according to the 3D data used in additive manufacturing. Two current clamps are fixed on the metal wire and the forming substrate respectively, and a current path is formed between the metal wire and the forming substrate through a DC power supply, and an ammeter is connected in series in the current path; electromagnetic coils are arranged circumferentially around the metal wire, and magnetic rods are connected to the electromagnetic coils and distributed symmetrically on both sides of the end of the metal wire. The electromagnetic coils are fixedly connected to the coaxial wire feeding and air feeding pipes through electromagnetic coil fixing frames; the AC power supply provides an alternating electric field to the electromagnetic coils, thereby generating an alternating magnetic field near the end of the metal wire; the wire feeding mechanism and the drive motor feed the metal wire into the range of the light spot emitted by the laser source at a constant quantity and speed; the laser emitted by the laser source acts within the end range of the metal wire, forming a liquid melt at the end of the metal wire; at the same time, the laser acts on the forming substrate, forming a liquid molten pool on the forming substrate; the metal wire and the forming substrate form a liquid bridge connection mode through the liquid melt; Electromagnetic coils are arranged circumferentially around the metal wire, and magnetic rods are connected to the electromagnetic coils and distributed symmetrically on both sides of the end of the metal wire. An AC power supply provides an alternating electric field to the electromagnetic coils, thereby generating an alternating magnetic field near the end of the metal wire. The end of the metal wire is kept in contact with the forming substrate, and a pre-compression force is applied between the end of the metal wire and the forming substrate by the metal wire pressing mechanism to ensure good contact between the end of the metal wire and the forming substrate.

2. The microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device according to claim 1 is characterized in that: During operation, the laser source and the metal wire are stationary.

3. The microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device according to claim 1, characterized in that: Blow shielding gas coaxially with the metal wire.

4. The microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device according to claim 1, characterized in that: The shielding gas is an inert gas, which is ejected through a precision gas flow meter and a coaxial wire feeding and air feeding pipe. The coaxial wire feeding and air feeding pipe is heated by a gas pipe heating device, and the coaxial wire feeding and air feeding pipe transfers heat to the metal wire and the shielding gas by heat conduction, thereby heating the shielding gas and the metal wire.

5. The microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device according to claim 1, characterized in that: The metal wire is stainless steel wire, aluminum alloy wire, titanium alloy wire, flux-cored welding wire, high / medium entropy alloy, amorphous alloy wire or metal composite material wire.

6. The microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device according to claim 1, characterized in that: The metal wire angle adjustment structure adjusts the angle between the metal wire and the horizontal direction, and the angle range is 0~60°.

7. The microgravity metal fuse additive melt directional transfer and liquid bridge transition holding device according to claim 1, characterized in that: The industrial control system uses an ammeter to detect whether a closed current path is formed between the forming substrate and the metal wire. When the current on the ammeter is 0A, it indicates that the liquid bridge between the metal wire and the forming substrate is disconnected. When the liquid bridge is disconnected, the industrial control system increases the wire feeding length through the wire feeding mechanism and the drive motor. When a closed circuit exists in the passage, the industrial control system adjusts the wire feeding speed to the normal process to keep the forming substrate and the metal wire in a stable liquid bridge connection.

8. The microgravity metal fuse additive melt directional transfer and liquid bridge transition maintenance method of the microgravity metal fuse additive melt directional transfer and liquid bridge transition maintenance device according to any one of claims 1 to 7, characterized in that: The steps include: Step S1, adjusting the relative position of the laser source and the metal wire and the initial processing position of the forming substrate, forming a pre-pressure between the forming substrate and the metal wire by the metal wire pressing mechanism to ensure good contact between the metal wire and the forming substrate; Step S2: Slice the data according to the three-dimensional model to be constructed, and ensure that the wire feeding is always parallel to the forming direction and kept at the front end of the forming direction through the multi-axis motion platform; ensure that the metal wire is in contact with the forming substrate; Step S3: activating the shielding gas, laser source, DC power supply, AC power supply, wire feeding mechanism, and drive motor in sequence. After the metal wire contacts the forming substrate, a current path is generated between the metal wire and the forming substrate. The current is used as a control signal to start additive manufacturing according to the slice data of the three-dimensional model. Step S4: During the processing, the industrial control system detects the current generated between the metal wire and the forming substrate. When the current is zero, the dynamic wire feeding amount program is started to increase the wire feeding amount so that the metal liquid bridge connection between the metal wire and the forming substrate is achieved. When the current value recovers, the dynamic wire feeding amount program is adjusted to the normal wire feeding amount process so that a stable liquid bridge connection is maintained between the metal wire and the forming substrate. Step S5: After the current layer is processed, the wire feeding mechanism and the drive motor, DC power supply, laser source, and shielding gas are sequentially turned off; at the same time, the metal wire pressing mechanism moves upward to release the pre-pressure between the metal wire and the forming substrate, and the forming substrate is moved to the initial position of the next trajectory by the multi-axis motion platform; Step S6: Repeat steps S1, S2, S3, S4 and S5 until the entire three-dimensional component is processed.

9. A microgravity metal fuse additive melt directional transfer and liquid bridge transition maintenance method according to claim 8, characterized in that: The flow rate of the protective gas is 0L / min~25L / min; the laser source is used to output pulsed laser or continuous laser, its maximum output power is 4000W, the pulse frequency is 10Hz~1000HZ, the laser pulse width is 2~50ms, and its scanning speed is 50mm / min~2000mm / min; the maximum output current of the DC power supply is 400A.

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