Laser continuous liquid interface additive manufacturing method and device for rod piece

Abstract

The invention discloses a laser continuous liquid interface additive manufacturing method and device for a rod piece, and the method comprises the steps: horizontally arranging a substrate for bearing a workpiece, and enabling a wire material to be perpendicular to the substrate from the upper part; the emergent angle of the laser excitation device is adjusted, so that the emitted laser obliquely irradiates the wire; starting a laser excitation device, wherein the laser power excited by the laser excitation device is P; the wire is fed downwards at the speed of V1, the substrate moves at the speed of V2, and the laser irradiation position is kept unchanged, so that the wire is melted between the substrate or the formed rod piece and the tail end of the wire to form a continuous liquid interface; and the wire is fed downwards at the speed V1, the substrate moves at the speed V2, and the laser power irradiation position is kept unchanged until the rod piece reaches the target length. And melting the wire through laser to enable the wire to form a continuous liquid interface between the base plate or the formed rod piece and the tail end of the wire so as to manufacture the rod piece.

Description

Technical Field

[0001] The present invention relates to the field of laser additive manufacturing technology, and in particular to a method and device for manufacturing a rod by using laser additive manufacturing technology in a space environment. Background Art

[0002] Additive manufacturing technology overcomes the large amount of waste of raw materials in traditional "removal of materials" manufacturing. At the same time, it has the advantages of rapid prototyping, grain refinement, and uniform structure. It has become the first choice for rapid prototyping technology of complex structural parts.

[0003] Generally speaking, most of the current additive manufacturing of rods is generally based on arc fuse additive point by point manufacturing to achieve additive manufacturing of rod-shaped structures, especially in the field of construction, which mainly uses CMT arc additive, with the heat source being arc, the material form being wire, and the wire transition being short-circuit transition, to achieve point-by-point manufacturing of rod units, and at the same time expand to the spatial free forming of complex frames / lattices / trusses and other structures based on rod units.

[0004] However, in actual production, it was found that, on the one hand, the rods manufactured point by point by arc fuse additive manufacturing not only have large internal stress but also poor surface quality; on the other hand, arc fuse additive manufacturing point by point is not suitable for rod manufacturing in a space environment. Summary of the invention

[0005] In view of this, the present invention provides a laser continuous liquid interface additive manufacturing method and device for rods, which uses laser melting of wire to form a continuous liquid interface to replace the existing point-by-point additive manufacturing method for manufacturing rods, thereby improving the surface accuracy of the rods and being more suitable for rod manufacturing in space environments.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: The first aspect of the present invention is to provide a laser continuous liquid interface additive manufacturing method for a rod, the additive manufacturing method is based on an additive manufacturing device for a rod, the additive manufacturing device comprises: a horizontally arranged substrate for carrying a workpiece, a wire feeding device located directly above the substrate for feeding a wire in a direction perpendicular to the substrate, and a laser excitation device for exciting laser melting of the wire, the additive manufacturing device also comprises: a monitoring system for monitoring the melting state of the wire, the monitoring system comprising an image acquisition device and a displacement sensor; the additive manufacturing method comprises the steps of: The substrate for carrying the workpiece is horizontally arranged, and the wire is perpendicular to the substrate from above; the emission angle of the laser excitation device is adjusted so that the emitted laser is irradiated obliquely on the wire; Turn on the laser excitation device, the laser power excited by the laser excitation device is P; the wire is fed downward at a speed V1, the substrate moves at a speed V2, and the laser irradiation position remains unchanged, so that the wire is melted between the substrate or the formed rod and the end of the wire to form a continuous liquid interface; The wire is fed downward at a speed of V1, the substrate is moved at a speed of V2, and the laser power irradiation position remains unchanged until the rod reaches the target length; Wherein, the laser power P is 140~160W; When the speed V1 is 4~6mm / s, the speed V2 is 0.3~0.6mm / s; When the speed V1 is 6.5~8.5mm / s, the speed V2 is 0.7~1.2mm / s; When the speed V1 is 9~11mm / s, the speed V2 is 1~2.25mm / s; The image acquisition device acquires images periodically or in real time and sends them to the host computer. The host computer processes the images acquired by the image acquisition device to obtain the current state of the liquid bridge. The host computer corrects the wire feeding speed or the movement speed of the substrate according to the current state of the liquid bridge. The host computer processes the image acquired by the image acquisition device to obtain the current state of the liquid bridge, and the host computer corrects the wire feeding speed or the movement speed of the substrate according to the current state of the liquid bridge, specifically including: The host computer performs image processing to obtain the current thickness or width of the liquid bridge, and compares it with the thickness or width of the liquid bridge obtained in the previous cycle, or the average thickness or width in the previous time period; If it becomes smaller, the current wire feeding speed and substrate moving speed are obtained through the displacement sensor, and it is determined whether the wire feeding speed and substrate moving speed are within the preset threshold range. If they are not within the preset threshold range, the wire feeding speed and / or substrate moving speed are adjusted to within the preset threshold range; If it becomes larger, reduce the wire feeding speed or increase the substrate moving speed to keep it within the preset range; When the preset threshold range of the wire feeding speed is 4~6mm / s, the preset threshold range of the substrate moving speed is 0.3~0.6mm / s; or, when the preset threshold range of the wire feeding speed is 6.5~8.5mm / s, the preset threshold range of the substrate moving speed is 0.7~1.2mm / s; when the preset threshold range of the wire feeding speed is 9~11mm / s, the preset threshold range of the substrate moving speed is 1~2.25mm / s.

[0007] Preferably, the angle between the laser and the wire is 20°-60°, and / or the wire is TC4 titanium alloy with a diameter of 0.4-1.2 mm.

[0008] Preferably, the laser excited by the laser excitation device is a circular laser beam, and the wire is located in the center of the circular laser beam.

[0009] Preferably, the image acquisition device is a high-speed camera; and the monitoring system also includes an infrared thermal imager.

[0010] A second aspect of the present invention is to provide a laser continuous liquid interface additive manufacturing device for a rod, comprising a horizontally arranged substrate for carrying the rod, a wire feeding device located directly above the substrate for feeding a wire in a direction perpendicular to the substrate, a laser excitation device for exciting laser melting of the wire, and a vertical driving mechanism for driving the substrate to move up and down; The vertical drive mechanism includes a lead screw, on which a trolley is provided that matches the lead screw thread, and the base plate is fixed on the trolley; it also includes a guide rod for guiding the trolley, and the lead screw is driven to rotate by a motor; It also includes a host computer and a monitoring system for monitoring the melting state of the wire material, wherein the monitoring system includes an image acquisition device and a displacement sensor; The host computer is used to perform image processing on the images collected by the image acquisition device to obtain the current state of the liquid bridge, and to correct the wire feeding speed or the movement speed of the substrate according to the current state of the liquid bridge; specifically, the host computer performs image processing to obtain the current thickness or width of the liquid bridge, and compares it with the thickness or width of the liquid bridge obtained in the previous cycle, or the average thickness or width in the previous time period; if it becomes smaller, the current wire feeding speed and substrate movement speed are obtained through the displacement sensor, and it is determined whether the wire feeding speed and substrate movement speed are within the preset threshold range. If not, the wire feeding speed and substrate movement speed are adjusted. The substrate moving speed is within a preset threshold range; if it increases, the wire feeding speed is reduced or the substrate moving speed is increased to make it within the preset range; when the preset threshold range of the wire feeding speed is 4~6mm / s, the preset threshold range of the substrate moving speed is 0.3~0.6mm / s; or, when the preset threshold range of the wire feeding speed is 6.5~8.5mm / s, the preset threshold range of the substrate moving speed is 0.7~1.2mm / s; when the preset threshold range of the wire feeding speed is 9~11mm / s, the preset threshold range of the substrate moving speed is 1~2.25mm / s.

[0011] Preferably, the wire feeding device comprises a capstan for receiving the wire material, a pair of wire feeding rollers are arranged side by side below the capstan; and a wire guide tube is vertically arranged below the wire feeding rollers.

[0012] Preferably, a straightener is provided between the capstan and the wire feeding roller.

[0013] Preferably, the wire feeding roller is driven by a DC motor, and the DC motor is controlled by a PID controller.

[0014] Preferably, the monitoring system also includes an infrared thermal imager.

[0015] Preferably, the substrate and the wire feeding device are connected to a host computer, and the movement speed and the wire feeding speed are controlled by the host computer.

[0016] The benefit of the present invention lies in that: the present invention uses laser fusing to form a continuous liquid interface for additive manufacturing of rods. Compared with the existing point-by-point additive manufacturing method of rods, the finished product has high surface accuracy and high strength, and is more suitable for rod manufacturing in a space environment, especially the additive manufacturing of straight rods in a space environment.

[0017] Due to the influence of environmental factors such as gravity and temperature in space, the printing method is different from that on the ground, and the molding is more difficult. On the one hand, since it needs to be carried into the space environment, the equipment is required to be as simple and light as possible. Therefore, this application uses a laser (preferably a semiconductor laser with a wavelength of 808nm) to perform additive manufacturing of rods. Since the laser itself is small in size and light in weight, the additive manufacturing device as a whole is small in size and light in weight; on the other hand, the difficulty of using lasers for additive manufacturing of rods in a space environment lies in the coordination of the wire feeding speed and the substrate moving speed. If the wire feeding speed is too slow or the substrate moving speed is too fast, the liquid bridge between the end of the wire and the formed rod is very easy to break. If the wire feeding speed is too fast or the substrate moving speed is too slow, wire tying is likely to occur (for example, for additive manufacturing of straight rods or non-straight rods such as spiral rods, the vertical downward wire feeding speed is too fast, which will cause wire tying). Therefore, it is generally believed that the wire feeding speed shall not be less than 13mm / s and the substrate moving speed shall not be less than 3mm / s; on the other hand, the type and diameter of the wire will also affect the wire feeding speed and the substrate moving speed.TC4 titanium alloy is very suitable for making aerospace devices. After a lot of creative work, it was unexpectedly discovered that for 0.4-1.2mm (for a certain type of straight rod or a certain type of truss in space) TC4 titanium alloy wire, the total laser power is 140-160W (because in a microgravity environment such as space, heat is mainly dissipated in the form of thermal radiation, so the laser power cannot be too large, otherwise the large amount of heat generated cannot be dissipated in time, which will greatly affect the service life of the device. If a heat sink is set, the cost, volume and weight of the equipment will be greatly increased. Of course, the laser The total power cannot be too small, otherwise the wire will not be fully melted, which will cause the liquid bridge to break or wire bridging. Therefore, for the titanium alloy wire of this specific diameter, the optimal total laser power was found through creative labor. When the wire feeding speed is 4-6mm / s, if the substrate moving speed is greater than 0.6mm / s, due to the microgravity environment, under the action of surface tension, the melted wire forms droplets, which makes the liquid bridge formed between the end of the wire and the molten pool very easy to break, and then the rod manufacturing cannot continue. If the substrate moving speed is less than 0.3mm / s, wire bridging occurs; and when the wire feeding speed is 6.5-8. When the wire feeding speed is 5mm / s, if the substrate moving speed is greater than 1.2mm / s, due to the microgravity environment, under the action of surface tension, the melted wire forms droplets, so that the liquid bridge formed between the end of the wire and the molten pool is very easy to break, and then the rod manufacturing cannot continue. If the substrate moving speed is less than 0.7mm / s, wire tying occurs; and when the wire feeding speed is 9-11mm / s, if the substrate moving speed is greater than 2.25mm / s, due to the microgravity environment, under the action of surface tension, the melted wire forms droplets, so that the liquid bridge formed between the end of the wire and the molten pool is very easy to break, and then the rod manufacturing cannot continue. The rod manufacturing cannot be continued if the substrate moving speed is less than 1mm / s, wire tangling occurs; when the wire feeding speed is greater than 11mm / s, the wire cannot be melted in time, and the end of the wire will be deformed against the substrate and cannot be stably formed; when the wire feeding speed is less than 4mm / s, the end of the wire cannot form a stable connection with the molten pool, making it very easy to break the liquid bridge between the end of the wire and the molten pool, which causes the end of the wire to be melted to form droplets. In a microgravity environment, due to the effect of surface tension, the small droplets at the end of the wire will gradually become large droplets or liquid spheres, thereby interrupting the rod forming process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural principle diagram of the present invention.

[0019] Figure 2A , 2B Rods manufactured using the existing point-by-point additive manufacturing method.

[0020] Figure 2C A rod manufactured according to the present invention.

[0021] Markings in the figure: 1 substrate, 2 laser excitation device, 3 wire feeding roller, 4 capstan, 5 straightener, 6 wire guide tube, 7 high-speed camera, 8 infrared thermal imager, 9 displacement sensor, 10 lead screw, 11 trolley, 100 formed rod, 101 continuous liquid interface, 102 laser, 103 wire. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0023] Herein, suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings by themselves. Therefore, "module", "component" or "unit" can be used mixedly.

[0024] In this document, the terms "upper", "lower", "inside", "outside", "front end", "rear end", "both ends", "one end", "the other end", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] Herein, the terms “first” and “second” are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0026] In this document, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In this article, the term "continuous liquid interface" means that under the action of laser, the transition form between the end of the metal wire and the molten pool is always in a liquid bridge transition state, that is, the end of the wire and the molten pool are connected by a metal liquid bridge.

[0028] In this article, the term "liquid bridge" refers to the rapid melting of the metal wire by the laser to make it a molten metal (liquid), and under the action of the movement of the substrate, the unmelted wire, that is, the end of the wire and the formed rod on the substrate are connected in the form of a molten metal. The additive manufacturing process is a process accompanied by physical phase changes such as the formation of the liquid bridge and solidification into a rod (solid).

[0029] In this article, the term "wire binding" refers to the phenomenon that the solid metal wire is fed too much, resulting in incomplete melting and accumulation.

[0030] like Figure 1 As shown, the present invention provides a laser continuous liquid interface additive manufacturing device for a rod, comprising a horizontally arranged substrate 1 for supporting the rod, a wire feeding device located directly above the substrate 1 for feeding a wire 103 in a direction perpendicular to the substrate 1, and a laser excitation device 2 for exciting laser melting of the wire 103.

[0031] In some embodiments, the substrate 1 is driven to move up and down by a vertical drive mechanism; the vertical drive mechanism includes a lead screw 10, on which a trolley 11 is provided that is threadedly matched with the lead screw 10, and the substrate 1 is fixed on the trolley 11; it also includes a guide rod (not shown in the figure) for guiding the trolley 11, and the lead screw 10 is driven to rotate by a motor. Of course, other methods can also be used to drive the substrate 1 to move, such as a slide rail slider, a cylinder, etc., as long as it can drive the substrate 1 to move up and down and achieve precise control.

[0032] In other embodiments, in order to manufacture non-straight rods such as spiral rods, the substrate may also move along three directions of XCY.

[0033] In other embodiments, in order to manufacture a spatial truss structure, a robotic arm may be used to move the laser and the wire, and when the robotic arm moves the laser and the wire to the target position, the substrate is moved to manufacture the rods at the corresponding position.

[0034] The wire feeding device specifically includes a capstan 4 for storing the wire 103, a pair of wire feeding rollers 3 are arranged side by side below the capstan 4, and a wire guide tube 6 is vertically arranged below the wire feeding roller 3. In addition, in order to ensure the alignment of the wire, a straightener 5 is arranged between the capstan 4 and the wire feeding roller 3. The wire feeding roller 3 clamps the wire and pulls the wire 103 out of the capstan 4 by rotation to realize wire feeding. The wire feeding roller 3 is driven by a DC motor, and the DC motor is automatically controlled by PID control to adjust the wire feeding speed according to the melting condition.

[0035] The laser excitation device 2 in the present invention is a circular laser excitation device, which can excite multiple laser beams 102 to be evenly arranged in a circle, and melt the wire 103 from multiple directions at the same time to ensure the uniformity of melting of the wire 103.

[0036] In order to monitor the melting of the wire, the present invention is also provided with a monitoring system, including a high-speed camera 7, an infrared thermal imager 8 and a displacement sensor 9, for monitoring the continuity, temperature and other parameters of the liquid interface. In addition, in order to realize automatic control, the monitoring system, the wire feeding device and the substrate 1 are all connected to the host computer, and the wire feeding speed and the movement speed of the substrate 1 are adjusted by the data monitored by the monitoring system to ensure the formation of a continuous liquid interface 101.

[0037] Based on the above device, the present invention also provides a laser continuous liquid interface additive manufacturing method for a rod, comprising: The first step is to horizontally set the substrate for carrying the workpiece and place the wire perpendicular to the substrate from above; adjust the emission angle of the laser excitation device so that the emitted laser is irradiated obliquely on the wire; The second step is to turn on the laser excitation device, the laser power excited by the laser excitation device is P; the wire is fed downward at a speed of V1, the substrate moves at a speed of V2, and the laser irradiation position remains unchanged, so that the wire is melted to form a continuous liquid interface between the substrate or the formed rod and the end of the wire. The liquid material after the wire is melted has a certain surface tension that can bridge between the end of the wire and the substrate or the formed rod.

[0038] In the third step, the wire is fed downward at speed V1, the substrate is moved at speed V2, and the laser power irradiation position remains unchanged until the rod reaches the target length. If the wire feeding speed and substrate movement speed can be controlled well, the liquid material can be ensured to be continuous. When the liquid material below cools to a solid state to form a rod, the wire above is melted into a liquid again, and this process is repeated to form a complete rod.

[0039] As a specific embodiment, the present invention selects TC4 titanium alloy as the wire material, and its diameter is 0.4~1.2mm; the power P of the laser is 140~160W; when the speed V1 is 4~6mm / s, the speed V2 is 0.3~0.6mm / s; when the speed V1 is 6.5~8.5mm / s, the speed V2 is 0.7~1.2mm / s; when the speed V1 is 9~11mm / s, the speed V2 is 1~2.25mm / s. Under the premise that the parameters such as the wire material and the laser power are certain, in order to ensure the formation of a continuous liquid interface, it is necessary to control the wire feeding speed and the speed of the substrate movement well. If the substrate moves too fast or the wire feeding speed is too slow, the liquid interface will be disconnected, resulting in failure of rod manufacturing. If the substrate moves too slowly or the wire feeding speed is too fast, the wire material will not melt in time and will hit the substrate or the formed layer of the workpiece, resulting in wire tying.

[0040] In some embodiments, in order to ensure the continuity of the liquid bridge, in the third step, the monitoring system is used to detect the change of the liquid bridge. Specifically, a high-speed camera is used to collect images, and the laser focus is at the focus position of the high-speed camera.

[0041] After the image acquisition device acquires images periodically or in real time, it sends them to the host computer, which processes the images acquired by the image acquisition device to obtain the current state of the liquid bridge. The host computer corrects the wire feeding speed or the movement speed of the substrate according to the current state of the liquid bridge. For example, if the host computer performs image processing to obtain the current thickness or width of the liquid bridge (specifically, the thickness or width value of the liquid bridge can be calculated based on the pixel value; further, the image can be pre-processed to increase the clarity of the image, thereby improving the accuracy of the corresponding data of the liquid bridge), and compare it with the thickness or width of the liquid bridge obtained in the previous cycle, or the average thickness or width in the previous time period (which can be preset), if it becomes smaller, it means that the liquid bridge is at risk of breaking, and the current wire feeding speed and / or substrate moving speed is corrected (specifically, the current wire feeding speed and substrate moving speed are obtained through the displacement sensor, and it is determined whether the wire feeding speed and substrate moving speed are within the above-mentioned preset threshold range. If not within the preset threshold range, the wire feeding speed and / or substrate moving speed are adjusted to the above-mentioned preset threshold range) to ensure the continuity of the liquid bridge; accordingly, if it becomes larger, it means that there is a risk of wire tying, and the current wire feeding speed and / or substrate moving speed is corrected (for example, the wire feeding speed is reduced or the substrate moving speed is increased so that it is within the above-mentioned preset range).

[0042] Of course, in other embodiments, a prediction model for judging whether the liquid bridge has a risk of breaking may be obtained by pre-training with a large number of training samples (including image data of a normal liquid bridge, image data of a liquid bridge about to break, and image data of a broken liquid bridge), and then the above-mentioned captured image data may be input into the prediction model for prediction, thereby obtaining a prediction result, so that the corresponding wire feeding speed or substrate movement speed can be adjusted according to the prediction result.

[0043] Furthermore, in order to ensure the connection between the formed rod and the substrate in a microgravity environment, before executing the above-mentioned first step, the end of the wire is welded to the substrate, thereby avoiding the difficulty of the melt at the end of the wire to connect with the substrate due to the effect of surface tension in the microgravity environment in the initial stage of manufacturing.

[0044] In order to verify the surface progress and performance advantages of the rods manufactured by the method of the present invention in a microgravity environment, a control test was conducted, that is, TC4 titanium alloy wire with a length of 0.8-1mm and a diameter of 0.8mm was used to manufacture straight rods by resistance heating thermal deposition forming, arc stagnation deposition forming and the above-mentioned laser fuse additive manufacturing method. In the laser fuse additive manufacturing process, the total laser power P is 150W, the wire feeding speed V1 is 7mm / s, and the substrate moving speed (i.e., the descending speed) V2 is 1.2mm / s. The straight rods obtained by the three methods are as follows: Figure 2A-2C shown.

[0045] in, Figure 2A and Figure 2B They are rods manufactured by wire resistance heating point-by-point additive method and rods manufactured by arc stagnation deposition additive method respectively. Figure 2C The rod is manufactured by the device and method provided by the present invention. It can be clearly seen that the surface accuracy of the rod manufactured by the present invention is greatly improved compared with the existing rod manufactured by point-by-point additive manufacturing. In addition, according to tests, the tensile strength of the rod manufactured by TC4 titanium alloy additive manufacturing in the present invention exceeds 900MPa, which is equivalent to the strength of forged parts.

[0046] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A laser continuous liquid interface additive manufacturing method for a rod, characterized in that: The additive manufacturing method is based on an additive manufacturing device for a rod, the additive manufacturing device comprises: a horizontally arranged substrate for carrying a workpiece, a wire feeding device located directly above the substrate for feeding a wire in a direction perpendicular to the substrate, and a laser excitation device for exciting a laser melting wire. The additive manufacturing device also comprises: a monitoring system for monitoring the melting state of the wire, the monitoring system comprising an image acquisition device and a displacement sensor; the additive manufacturing method comprises the steps of: The substrate for carrying the workpiece is horizontally arranged, and the wire is perpendicular to the substrate from above; the emission angle of the laser excitation device is adjusted so that the emitted laser is irradiated obliquely on the wire; Turn on the laser excitation device, the laser power excited by the laser excitation device is P; the wire is fed downward at a speed V1, the substrate moves at a speed V2, and the laser irradiation position remains unchanged, so that the wire is melted between the substrate or the formed rod and the end of the wire to form a continuous liquid interface; The wire is fed downward at a speed of V1, the substrate is moved at a speed of V2, and the laser power irradiation position remains unchanged until the rod reaches the target length; Wherein, the laser power P is 140~160W; When the speed V1 is 4~6mm / s, the speed V2 is 0.3~0.6mm / s; When the speed V1 is 6.5~8.5mm / s, the speed V2 is 0.7~1.2mm / s; When the speed V1 is 9~11mm / s, the speed V2 is 1~2.25mm / s; The image acquisition device acquires images periodically or in real time and sends them to the host computer. The host computer processes the images acquired by the image acquisition device to obtain the current state of the liquid bridge. The host computer corrects the wire feeding speed or the movement speed of the substrate according to the current state of the liquid bridge. The host computer processes the image acquired by the image acquisition device to obtain the current state of the liquid bridge, and the host computer corrects the wire feeding speed or the movement speed of the substrate according to the current state of the liquid bridge, specifically including: The host computer performs image processing to obtain the current thickness or width of the liquid bridge, and compares it with the thickness or width of the liquid bridge obtained in the previous cycle, or the average thickness or width in the previous time period; If it becomes smaller, the current wire feeding speed and substrate moving speed are obtained through the displacement sensor, and it is determined whether the wire feeding speed and substrate moving speed are within the preset threshold range. If they are not within the preset threshold range, the wire feeding speed and / or substrate moving speed are adjusted to within the preset threshold range; If it becomes larger, reduce the wire feeding speed or increase the substrate moving speed to keep it within the preset range; When the preset threshold range of the wire feeding speed is 4~6mm / s, the preset threshold range of the substrate moving speed is 0.3~0.6mm / s; or, when the preset threshold range of the wire feeding speed is 6.5~8.5mm / s, the preset threshold range of the substrate moving speed is 0.7~1.2mm / s; when the preset threshold range of the wire feeding speed is 9~11mm / s, the preset threshold range of the substrate moving speed is 1~2.25mm / s.

2. The laser continuous liquid interface additive manufacturing method for a rod in a space environment according to claim 1, characterized in that: The angle between the laser and the wire is 20°-60°, and / or the wire is TC4 titanium alloy with a diameter of 0.4-1.2 mm.

3. The laser continuous liquid interface additive manufacturing method for a rod according to claim 1, characterized in that: The laser excited by the laser excitation device is a circular laser beam, and the wire material is located in the middle of the circular laser beam.

4. The laser continuous liquid interface additive manufacturing method for a rod according to claim 1, characterized in that: The image acquisition device is a high-speed camera; the monitoring system also includes an infrared thermal imager.

5. A laser continuous liquid interface additive manufacturing device for a rod, characterized in that: It includes a horizontally arranged base plate for carrying a rod, a wire feeding device located directly above the base plate for feeding a wire material in a direction perpendicular to the base plate, a laser excitation device for exciting laser melting of the wire material, and a vertical driving mechanism for driving the base plate to move up and down; The vertical drive mechanism includes a lead screw, on which a trolley is provided that matches the lead screw thread, and the base plate is fixed on the trolley; it also includes a guide rod for guiding the trolley, and the lead screw is driven to rotate by a motor; It also includes a host computer and a monitoring system for monitoring the melting state of the wire material, wherein the monitoring system includes an image acquisition device and a displacement sensor; The host computer is used to perform image processing on the images collected by the image acquisition device to obtain the current state of the liquid bridge, and to correct the wire feeding speed or the movement speed of the substrate according to the current state of the liquid bridge; specifically, the host computer performs image processing to obtain the current thickness or width of the liquid bridge, and compares it with the thickness or width of the liquid bridge obtained in the previous cycle, or the average thickness or width in the previous time period; if it becomes smaller, the current wire feeding speed and substrate movement speed are obtained through the displacement sensor, and it is determined whether the wire feeding speed and substrate movement speed are within the preset threshold range. If not, the wire feeding speed and substrate movement speed are adjusted. The substrate moving speed is within a preset threshold range; if it increases, the wire feeding speed is reduced or the substrate moving speed is increased to make it within the preset range; when the preset threshold range of the wire feeding speed is 4~6mm / s, the preset threshold range of the substrate moving speed is 0.3~0.6mm / s; or, when the preset threshold range of the wire feeding speed is 6.5~8.5mm / s, the preset threshold range of the substrate moving speed is 0.7~1.2mm / s; when the preset threshold range of the wire feeding speed is 9~11mm / s, the preset threshold range of the substrate moving speed is 1~2.25mm / s.

6. The laser continuous liquid interface additive manufacturing device for a rod according to claim 5, characterized in that: The wire feeding device comprises a capstan for storing wire materials, a pair of wire feeding rollers are arranged side by side below the capstan, and a wire guide tube is vertically arranged below the wire feeding rollers.

7. The laser continuous liquid interface additive manufacturing device for a rod according to claim 6, characterized in that: A straightener is arranged between the capstan and the wire feeding roller.

8. The laser continuous liquid interface additive manufacturing device for a rod according to claim 6, characterized in that: The wire feeding roller is driven by a DC motor, and the DC motor is controlled by a PID controller.

9. The laser continuous liquid interface additive manufacturing device for a rod according to claim 5, characterized in that: The monitoring system also includes an infrared thermal imager.

10. The laser continuous liquid interface additive manufacturing device for a rod according to claim 9, characterized in that: The base plate and the wire feeding device are connected to a host computer, and the host computer controls the movement speed and the wire feeding speed.

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