CN115415670A - Laser continuous liquid interface additive manufacturing method and device for a rod - Google Patents

Abstract

The invention discloses a method and device for laser continuous liquid interface additive manufacturing of rods. The method includes: horizontally setting a substrate for carrying a workpiece, and making the wire perpendicular to the substrate from above; adjusting the emission of the laser excitation device angle, so that the emitted laser light is obliquely irradiated on the wire; the laser excitation device is turned on, and the laser power excited by the laser excitation device is P; the wire is fed downward at the speed V1, the substrate moves at the speed V2, and the laser irradiation position Keep the same, so that the wire melts to form a continuous liquid interface between the substrate or the formed rod and the end of the wire; the wire keeps feeding downward at a speed of V1, the substrate keeps moving at a speed of V2, and the laser power irradiation position continues to change change until the member reaches the target length. Rod fabrication is accomplished by laser melting the wire such that the wire forms a continuous liquid interface between the substrate or formed rod and the end of the wire.

Description

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

technical field

The invention relates to the technical field of laser additive manufacturing, in particular to a method and device for manufacturing rods using laser additive technology.

Background technique

Additive manufacturing technology overcomes the large waste of raw materials caused by traditional "material removal" manufacturing, and at the same time has the advantages of rapid prototyping, grain refinement, and uniform organization. It has become the first choice for rapid prototyping technology of complex structural parts.

Generally, most of the current additive manufacturing of rods is generally based on arc fuse additive point by point manufacturing to realize the additive manufacturing of rod-shaped structures, especially in the construction field, mainly using CMT arc additive, and the heat source is electric arc. The material form is wire, and the welding wire transition is a short-circuit transition, which realizes the manufacture of bar elements point by point, and at the same time extends to the space free forming of complex frame/lattice/truss structures based on bar elements.

However, in actual production, it is found that, on the one hand, the rods manufactured point by point by arc fuse additive not only have high internal stress, but also have poor surface quality; on the other hand, point by point additive manufacturing of arc fuse is not suitable for the space environment The following rods are manufactured.

Contents of the invention

In view of this, the present invention provides a laser continuous liquid interface additive manufacturing method and device for rods, which replaces the existing point-by-point additive method of manufacturing rods by laser melting wires to form a continuous liquid interface, and improves the strength of rods. The surface accuracy is more suitable for the manufacture of rods in the space environment.

In order to solve the above technical problems, the technical solution of the present invention is a laser continuous liquid interface additive manufacturing method using a rod, including:

Set the substrate used to carry the rods horizontally, and make the wire perpendicular to the substrate from above; adjust the exit angle of the laser excitation device so that the emitted laser light is obliquely irradiated 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 of V1, the substrate moves at a speed of V2, and the laser irradiation position remains unchanged, so that the wire is melted on the substrate or the formed rod Between the piece and the end of the wire to form a continuous liquid interface;

The wire keeps feeding downward at speed V1, the substrate keeps moving at speed V2, and the laser power irradiation position remains unchanged until the rod reaches the target length.

The principle of the present invention is to form a continuous liquid interface between the substrate and the end of the wire, or between the formed rod and the end of the wire, by laser melting the wire for rod manufacture. By reasonably controlling the wire feeding speed and the substrate moving speed, the liquid interface will not stop flowing and will not bind the wire.

As an improvement, the angle between the laser and the wire is 20°-60°. A reasonable layout can be realized by setting a reasonable inclination angle, thereby reducing the overall volume of the device to a certain extent.

As an improvement, the wire material is TC4 titanium alloy with a diameter of 0.4-1.2 mm.

As an improvement, the power P of the laser is 140-160W.

As an improvement, 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 When V1 is 9-11 mm/s, the speed V2 is 1-2.25 mm/s.

As a further improvement, the laser excited by the laser excitation device is a circular laser beam, and the filament is located in the middle of the circular laser beam. It makes the circumferential melting of the wire uniform, and facilitates the formation of a continuous liquid interface. Preferably, three laser beams or five laser beams are evenly distributed.

The present invention also provides a laser continuous liquid interface additive manufacturing device for rods, which includes a substrate horizontally arranged to carry rods, a wire feeding device located directly above the substrate for supplying wire materials in a direction perpendicular to the substrate, and A laser excitation device used to excite the laser to melt the filament.

As another further improvement, the base plate is driven to move up and down by a vertical drive mechanism; the vertical drive mechanism includes a lead screw, and a trolley threaded with the lead screw is provided on the lead screw, and the base plate is fixed On the trolley; it also includes a guide rod guiding the trolley, and the screw is driven to rotate by the motor. The base plate moves up and down through the rotation of the lead screw, which has high precision and is easy to control, which is beneficial to the manufacture of straight rod parts.

As an improvement, the wire feeding device includes a capstan for accommodating the wire material, a pair of wire feeding rollers are arranged side by side under the capstan, and a wire guide tube is vertically arranged under the wire feeding rollers.

As an improvement, a straightener is arranged between the capstan and the wire feeding roller. The wire is straightened before feeding, so that the wire feeding amount and wire feeding direction are more accurate.

As an improvement, the wire feeding roller is driven by a DC motor, and the DC motor is controlled by a PID controller. The wire feeding speed is automatically controlled by PID to keep the wire melted and form a continuous liquid interface.

As an improvement, a monitoring system for monitoring the melting state of the wire is also included, and the monitoring system includes a high-speed camera, an infrared thermal imager and a displacement sensor. The monitoring system is used to monitor the melting state of the wire and the situation of the liquid interface, and feedback the situation so as to facilitate the adjustment of the wire feeding speed and the moving speed of the substrate.

As an improvement, the base plate and the wire feeding device are connected with a host computer, and the host computer controls the movement speed and the wire feeding speed. The upper computer adjusts the movement speed of the substrate and the wire feeding speed according to the information fed back by the monitoring system, so as to ensure the formation of a continuous liquid interface.

The advantage of the present invention is that: the present invention uses laser fuses to form a continuous liquid interface for additive manufacturing of rods. Compared with the existing point-by-point additive rod manufacturing method, the finished product has high surface precision and high strength, and It is more suitable for the manufacture of rods in the space environment, especially the additive manufacturing of straight rods in the space environment.

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, because it needs to be carried to the space environment, it requires the equipment to be as simple and light as possible. Therefore, this application Lasers (preferably semiconductor lasers with a wavelength of 808nm) are used for the additive manufacturing of rods. Because the laser itself is small in size and light in weight, the overall volume of the additive manufacturing device is small and light in weight; The difficulty of laser additive manufacturing of rods lies in the coordination of wire feeding speed and 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 will be very large. It is easy to break, and if the wire feeding speed is too fast or the substrate moving speed is too slow, it is easy to cause wire binding (for example, for the additive manufacturing of non-straight rod parts such as straight rods or spirals, the speed of vertically downward wire feeding is too high. Faster will lead to stringing), therefore, it is generally considered that the wire feeding speed should not be less than 13mm/s, and the substrate moving speed should 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 substrate moving speed . TC4 titanium alloy is very suitable for making aerospace devices. After a lot of creative work, it was unexpectedly found that: TC4 for 0.4-1.2mm (for a certain type of straight rod or a certain type of truss in space) Titanium alloy wire, the total laser power is 140-160W (because in the microgravity environment such as space, the heat is mainly dissipated in the form of thermal radiation, so the laser power should not be too large, otherwise the large heat will be generated and cannot be dissipated in time. It affects the service life of the device. If the heat sink is installed, the cost of the equipment and its own volume and weight will be greatly increased. Of course, the total power of the laser should not be too small, otherwise the melting of the wire will not be sufficient, resulting in a liquid bridge. Therefore, for the specific diameter of titanium alloy wire, find the best total laser power through creative work), and 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 liquid droplets, so that the liquid bridge formed between the end of the wire and the molten pool is easily broken, and the bar manufacturing cannot continue. If the substrate moves If the speed is less than 0.3mm/s, there will be stringing; when the wire feeding speed is 6.5-8.5mm/s, if the substrate moving speed is greater than 1.2mm/s, due to the microgravity environment, under the action of surface tension, it will be melted The wire formed by the droplet, so that the liquid bridge formed between the end of the wire and the molten pool is very easy to break, so that the bar cannot be manufactured. If the moving speed of the substrate is less than 0.7mm/s, there will be wire binding; and when the wire is fed When the speed is 9-11mm/s, if the moving speed of the substrate 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 gap between the end of the wire and the molten pool The formed liquid bridge is very easy to break, which makes it impossible to continue to manufacture rods. If the moving speed of the substrate is less than 1mm/s, stringing will occur;

However, 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, making it impossible to form stably; and when the wire feeding speed is less than 4mm/s, the end of the wire cannot be melted with the melt The pool forms a stable connection, so that the liquid bridge between the end of the wire and the molten pool is easily broken, which makes the end of the wire melted to form droplets, and in a microgravity environment, due to the effect of surface tension, the wire Small droplets at the end will gradually become larger droplets or globules, which will interrupt the bar forming process.

Description of drawings

Fig. 1 is the structure schematic diagram of the present invention.

2A and 2B are rods manufactured by the existing point-by-point additive manufacturing method.

Fig. 2C is a rod made by the present invention.

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

detailed description

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with specific embodiments.

Herein, the use of suffixes such as 'module', 'part' or 'unit' for denoting elements is only to facilitate description of the present invention and has no specific meaning by itself. Therefore, 'module', 'part' or 'unit' may be used in combination.

Herein, the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "another end" etc. are based on The orientation or positional relationship shown in the drawings is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as Limitations on the Invention.

Herein, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

In this article, unless otherwise clearly specified and limited, the terms "installed", "set with", "connected", etc. should be interpreted in a broad sense, such as "connected", which can be a fixed connection or a detachable connection, or Integral connection; it can be mechanical connection or electrical connection; it can be direct connection or indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

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

In this paper, the term "liquid bridge" refers to the rapid melting of the metal wire by the laser to make it a metal melt (liquid), and under the action of the substrate movement, etc., the unfused wire, that is, the end of the wire and the existing metal on the substrate The formed rods are connected in the form of metal melt. The additive manufacturing forming process is accompanied by physical phase transitions such as liquid bridge formation and solidification into rods (solids).

In this paper, the term "stringing" refers to the phenomenon that the solid metal wire material cannot be completely melted and piled up due to the excessive feeding amount.

As shown in Figure 1, the present invention provides a laser continuous liquid interface additive manufacturing device for rods, including a substrate 1 horizontally arranged for carrying rods, located directly above the substrate 1 for feeding in a direction perpendicular to the substrate 1 A wire feeding device for the wire material 103, and a laser excitation device 2 for exciting the laser to melt the wire material 103.

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, and the lead screw 10 is provided with a trolley 11 threadedly fitted with the lead screw 10, the The base plate 1 is fixed on the trolley 11; it also includes a guide rod (not shown in the figure) guiding the trolley 11, and the screw 10 is driven to rotate by the motor. Of course, other ways can also be used to drive the substrate 1 to move, such as slide rail sliders, oil cylinders, etc., as long as the substrate 1 can be driven up and down and precisely controlled.

In some other embodiments, in order to manufacture helical and other non-straight rods, the base plate can also move along XCY three directions.

In other embodiments, in order to manufacture the space truss structure, the robot arm can also be combined with the laser and the wire to move, and when the robot arm moves to the target position with the laser and the wire, the corresponding position can be achieved by moving the substrate manufacture of rods.

The wire feeding device specifically includes a capstan 4 for accommodating the wire material 103 , a pair of wire feeding rollers 3 are arranged side by side under the capstan 4 , and a wire guide tube 6 is vertically arranged under the wire feeding rollers 3 . In addition, in order to ensure the alignment of the wire, a straightener 5 is provided between the capstan 4 and the wire feeding roller 3 . The wire feeding roller 3 clamps the wire material, and pulls the wire material 103 from the capstan 4 by rotating 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, and the wire feeding speed is adjusted according to the melting condition.

The laser excitation device 2 in the present invention is a ring-type laser excitation device, which can excite multiple laser beams 102 uniformly arranged on the circumference, and melt the wire 103 from multiple directions at the same time to ensure the uniformity of the wire 103 melting.

In order to monitor the melting of the wire, the present invention is also equipped with a monitoring system, including a high-speed camera 7, an infrared thermal imager 8 and a displacement sensor 9, for monitoring parameters such as the continuity and temperature 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 moving speed of the substrate 1 are adjusted through the data monitored by the monitoring system to ensure the formation of the continuous liquid interface 101 .

Based on the above-mentioned device, the present invention also provides a laser continuous liquid interface additive manufacturing method for rods, including:

In the first step, the substrate for carrying the workpiece is set horizontally, 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 light is obliquely irradiated 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 on the substrate. Or a continuous liquid interface is formed between the formed rod and the end of the wire. The liquid material after the wire has melted has a certain surface tension to bridge between the end of the wire and the substrate or formed rod.

In the third step, the wire keeps feeding downward at the speed V1, the base plate keeps moving at the speed V2, and the irradiation position of the laser power remains unchanged until the rod reaches the target length. If the wire feeding speed and the speed of substrate movement can be well controlled, the liquid material will not be broken. When the lower liquid material cools to a solid state to form a rod, the upper wire is melted into a liquid state again and again to form a complete rod. .

As a specific embodiment, the present invention selects wire material to be TC4 titanium alloy, and its diameter is 0.4～1.2mm; The power P of described laser is 140～160W; When velocity V1 is 4～6mm/s, velocity 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 of certain parameters such as wire material and laser power, in order to ensure the formation of a continuous liquid interface, it is necessary to well control the speed of wire feeding and substrate movement. If the base plate moves too fast or the wire feed rate is too slow, the liquid interface breaks and the rod fails. If the base plate moves too slowly or the wire feeding speed is too fast, if the wire is not melted in time, it will push against the base plate or the formed layer of the workpiece, resulting in wire binding.

In some embodiments, in order to ensure the continuity of the liquid bridge, in the above third step, the above monitoring system is also 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 focal position of the high-speed camera.

After the image acquisition device collects the image periodically or in real time, it sends it to the upper computer, and the upper computer performs image processing on the image collected by the image acquisition device to obtain the current state of the liquid bridge. The upper computer according to the current state of the liquid bridge Correct wire feed speed or substrate movement speed. 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 according to the pixel value; furthermore, the image can also be preprocessed to increase The clarity of the image, thereby improving the accuracy of the corresponding data of the liquid bridge), and comparing 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 (presettable) , if it becomes smaller, it means that the liquid bridge has a risk of breaking, then correct the current wire feeding speed and/or substrate moving speed (specifically, obtain the current wire feeding speed and substrate moving speed through the displacement sensor, and judge the wire feeding speed and substrate moving speed Whether the moving speed of the substrate is within the above-mentioned preset threshold range, if not within the preset threshold range, adjust the wire feeding speed and/or the substrate moving speed to the above-mentioned preset threshold range) to ensure that the liquid bridge is continuous; correspondingly, If it becomes larger, it means that there is a risk of wire binding, 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).

Of course, in some other embodiments, 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 liquid bridge fracture) can also be trained in advance to determine whether the liquid bridge has A prediction model of fracture risk, so that the above-mentioned captured image data is input into the prediction model for prediction, so as to obtain a prediction result, so that the corresponding wire feeding speed or substrate movement speed can be adjusted according to the prediction result.

Furthermore, in order to ensure the connection between the formed rod and the substrate in a microgravity environment, before performing the first step above, the end of the wire and the substrate are welded together, so as to avoid the initial stage of manufacturing. The effect of tension makes it difficult for the melt at the end of the wire to connect to the substrate.

In order to prove the surface progress and performance advantages of the rods produced by the method of the present invention in a microgravity environment, a control test was done, that is, using TC4 titanium alloy wires with a length of 0.8-1mm and a diameter of 0.8mm, respectively using resistance heating and hot melting Product forming, arc stagnation deposition forming and the above-mentioned laser fuse additive manufacturing method to manufacture straight rods, wherein, in the laser fuse additive manufacturing process, the total laser power P is 150W, and the wire feeding speed V1 is 7mm/s. The moving speed (that is, the falling speed) V2 of the substrate is 1.2 mm/s. The results of straight rods obtained by the three methods are shown in Fig. 2A-Fig. 2C respectively.

Among them, FIG. 2A and FIG. 2B respectively show the rod manufactured by the wire resistance heating point-by-point additive method and the rod manufactured by the arc stagnation deposition additive method. Fig. 2C is a rod made by the apparatus 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 point-by-point additive manufacturing rod. In addition, it has been tested that the tensile strength of the rod manufactured by TC4 titanium alloy additive in the present invention exceeds 900 MPa, which is equivalent to the strength of the forging.

The above are only preferred implementations of the present invention, and it should be noted that the above preferred implementations should not be regarded as limiting the present invention, and the scope of protection of the present invention should be based on the scope defined in the claims. For those skilled in the art, without departing from the spirit and scope of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (10)

1. A laser continuous liquid interface additive manufacturing method of a rod, characterized in that the additive manufacturing method is based on an additive manufacturing apparatus of a rod, the additive manufacturing apparatus comprising: the additive manufacturing method comprises the following steps of horizontally arranging a substrate for bearing a workpiece, a wire feeding device which is positioned right above the substrate and used for feeding wires in a direction vertical to the substrate, and a laser excitation device used for exciting laser to melt the wires, wherein the additive manufacturing method comprises the following steps:

horizontally arranging a substrate for bearing a workpiece, and vertically arranging a wire material to the substrate from the upper part; adjusting the emergence angle of the laser excitation device to enable the emitted laser to irradiate the wire obliquely;

starting a laser excitation device, wherein the laser power excited by the laser excitation device is P; the wire is fed downwards at a speed V1, the substrate moves at a speed V2, and the laser irradiation position is kept unchanged, so that the wire is melted between the substrate or a formed rod and the tail end of the wire to form a continuous liquid interface;

the wire material is fed downwards at a speed V1, the substrate is moved at a speed V2, and the laser power irradiation position is continuously unchanged until the rod reaches the target length;

wherein the power P of the laser is 140-160W;

when the speed V1 is 4-6mm/s, the speed V2 is 0.3-0.6 mm/s;

when the speed V1 is 6.5-8.5mm/s, the speed V2 is 0.7-1.2 mm/s;

when the speed V1 is 9 to 11mm/s, the speed V2 is 1 to 2.25mm/s.

2. The method of claim 1, wherein the rod comprises: the included angle between the laser and the wire is 20-60 degrees, and/or the wire is TC4 titanium alloy with the diameter of 0.4-1.2 mm.

3. The method of claim 1, wherein the laser continuous liquid interface additive manufacturing method comprises: the laser excited by the laser excitation device is a circular laser beam, and the wire is positioned in the center of the circular laser beam.

4. The method of claim 1, wherein the laser continuous liquid interface additive manufacturing method comprises: the additive manufacturing apparatus further comprises: the monitoring system is used for monitoring the melting state of the wire material and comprises a high-speed camera, a thermal infrared imager and a displacement sensor; correspondingly, the additive manufacturing method further comprises the steps of: and the upper computer respectively adjusts the movement speed and the wire feeding speed of the substrate and the wire feeding device according to the monitoring data acquired by the monitoring system.

5. A device for manufacturing a rod piece by laser continuous liquid interface additive is characterized in that: comprises a substrate horizontally arranged for bearing a rod piece, a wire feeding device positioned right above the substrate and used for feeding wires in a direction vertical to the substrate, a laser excitation device used for exciting laser to melt the wires, and a vertical driving mechanism used for driving the substrate to move up and down, wherein,

the vertical driving mechanism comprises a lead screw, a trolley in threaded fit with the lead screw is arranged on the lead screw, and the substrate is fixed on the trolley; the trolley is characterized by further comprising a guide rod for guiding the trolley, and the lead screw is driven to rotate by the motor.

6. The laser continuous liquid interface additive manufacturing device of the rod piece according to claim 5, wherein: the wire feeding device comprises a winch for accommodating wires, and a pair of wire feeding rollers are arranged below the winch side by side; and a wire guide pipe is vertically arranged below the wire feeding roller.

7. The apparatus of claim 5, wherein: and a straightener is arranged between the winch and the wire feeding roller.

8. The laser continuous liquid interface additive manufacturing device of a rod piece according to claim 6, wherein: the wire feeding roller is driven by a direct current motor, and the direct current motor is controlled by a PID controller.

9. The laser continuous liquid interface additive manufacturing device of the rod piece according to claim 5, wherein: the wire melting monitoring system is used for monitoring the melting state of the wire, and comprises a high-speed camera, a thermal infrared imager and a displacement sensor.

10. The laser continuous liquid interface additive manufacturing device of a rod piece according to claim 9, wherein: the substrate and the wire feeding device are connected with an upper computer, and the upper computer controls the movement speed and the wire feeding speed.

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