A continuous feeding device for metal micro-droplet additive and a micro-droplet generation control method

Abstract

The application discloses a continuous feeding device for metal micro-droplet additive and a micro-droplet generation control method, adopts a double-wire pulse current arc starting fuse mode, realizes continuous feeding in the device by using an indirect electric arc fuse mode, and controls extrusion of metal micro-droplets by using gas pressure change in the device caused by the indirect electric arc. On the basis of metal micro-droplet additive, a synchronous control wire feeder is applied to realize the work of improving the fuse speed, synchronously supplementing raw materials, and extruding additive by using gas pressure change, effectively optimizes the process flow of metal additive manufacturing, and improves the working efficiency and working performance of metal additive manufacturing.

Description

Technical Field

[0001] This invention relates to the field of feeding and discharging control methods in metal droplet additive manufacturing technology, and particularly to a continuous feeding device and droplet generation control method for metal droplet additive manufacturing. Background Technology

[0002] Metal droplet additive manufacturing is an advanced manufacturing technology that constructs metal parts layer by layer by precisely controlling the generation, transport, and deposition of tiny metal droplets. Compared to traditional metal additive manufacturing methods, metal droplet additive manufacturing offers advantages such as high material utilization, high forming efficiency, multi-material manufacturing, and customized construction. It can achieve higher precision and more complex structures. With continuous technological development and improvement, its application scope will continue to expand, demonstrating enormous potential in multiple high-precision manufacturing fields.

[0003] Currently, metal droplet additive manufacturing technology employs eddy current heating to melt metal: metal raw materials are fed into a heating device with multiple turns of energized solenoid coils. The eddy current effect melts the metal wire, which is then stored in a discharge device. Inert gas is then introduced into the discharge device to control the pressure, causing the molten material to be extruded into droplets for stacking and printing. This method features concentrated energy and good controllability. However, this additive manufacturing method is highly dependent on the melting of the metal raw material by the molten wire device. The molten wire process is time-consuming and cannot allow for real-time replenishment of the molten material during the additive manufacturing process. Furthermore, simultaneous pressurized discharge while melting the metal raw material is not suitable, as this not only makes it difficult to control the droplet ejection but also reduces additive manufacturing efficiency.

[0004] WAAM (Wire Arc Additive Manufacturing) is a digital manufacturing technology developed from welding technology, using an electric arc as the energy carrier and metal wire as the filler material. WAAM uses an electric arc as the heat source to focus energy and melt the metal material. Its advantages include high material utilization, high forming efficiency, low equipment cost, and virtually no limitations on simple forming dimensions, making it suitable for printing and manufacturing products using metal composite wires (such as Ti, Ni, and Steel). Summary of the Invention

[0005] This invention designs a technique based on metal droplet additive manufacturing, utilizing pulse voltage arc-starting fuse technology in WAAM, which enables simultaneous melting of the fuse, continuous replenishment of raw materials, and pressurized discharge during the droplet additive manufacturing process. The invention also designs a device technical solution, aiming to improve the working efficiency and performance of metal droplet additive manufacturing.

[0006] This invention provides a continuous feeding device and a microdroplet generation control method for metal additive manufacturing by introducing a pulsed current into a double-stranded metal wire to induce an electric arc and melt it. This method can effectively improve the melting speed of the wire to optimize feeding. When the pulsed current acts on the wire, a wire feeder is used to simultaneously transport the wire into the device to achieve the purpose of synchronously replenishing raw materials. When the pulsed current acts on the wire, high temperature is generated, the temperature inside the device cavity increases sharply, and the air pressure is higher than the external air pressure, thereby extruding the molten metal from the device and achieving synchronous feeding and discharging. An eddy current heating device wrapped around the wire device is used to maintain the temperature inside the device and ensure that the molten metal is in a flowable liquid state.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A continuous feeding device for metal droplet additive manufacturing includes a welding wire feeder 5, a welding power source 3, and a metal droplet additive manufacturing device 4; both the welding power source 3 and the welding wire feeder 5 are connected to the metal droplet additive manufacturing device 4; there are two welding wire feeders 5, which feed wire into the metal droplet additive manufacturing device 4 respectively to form a double-strand metal wire.

[0009] The metal droplet additive manufacturing apparatus 4 includes a three-axis movable printing platform 2, a high-frequency generator, a wire melting device, and a control circuit 1. A welding power supply 3 is connected to the high-frequency generator and then to the wire melting device to generate a periodic pulsed current. The control circuit 1 is connected to the printing platform 2, the welding power supply 3, and the welding wire feeder 5. The control circuit 1 includes motion control of the printing platform 2, quantitative control of the pulsed current, and quantitative control of the wire feeding speed of the wire feeder 5. The three-axis movable printing platform 2 faces the wire melting device, and two strands of metal wire are fed into the wire melting device for fusion welding.

[0010] The fusion device includes a energized heat-insulating device 7 composed of a multi-turn energized solenoid coil, a metal wire inlet 6 equipped with a protective electrode, and a protective gas filled therein. The energized heat-insulating device 7 is located outside the fusion device. The double-stranded metal wire is fed into the fusion device through the metal wire inlet 6. A periodic pulsed current is used. When the current is high, the double-stranded metal wire ignites and melts, and the temperature and pressure inside the cavity rise rapidly. When the current is low, the double-stranded metal wire continues to melt due to residual heat, and the temperature inside the cavity decreases gradually. The wire feeding speed of the dual wire feeder changes periodically with the pulsed current. When the current is low, the wire is fed slowly to avoid the welding wire connecting and sticking at the arc initiation point due to slow melting. When the current is high, a higher wire feeding speed is used to ensure that welding wire can be replenished in time when the melting is fast.

[0011] Furthermore, the fuse device uses high-temperature resistant insulating materials, such as ceramic metal, to ensure the high-temperature fuse process and the temporary preservation of the molten raw material within the cavity.

[0012] Furthermore, the metal wire inlet 6 of the fusion device is equipped with a sealing plug made of high-temperature resistant insulating material to isolate the gas inside the cavity from the atmosphere, ensuring the airtightness and stability of the fusion device. This ensures that when the dual welding wires are ignited and fused, the gas pressure inside the cavity can increase, extruding the temporarily stored molten material for printing. These three features work together to achieve the effect of simultaneous fusion and material output, thereby enabling the continuous feeding technology of metal microdroplet additive manufacturing.

[0013] Furthermore, the control circuit enables three-dimensional six-axis motion control of the printing platform, thereby controlling the shape of the printed product; it also enables quantitative control of the pulse current and wire feeding speed, ensuring both wire melting efficiency and process safety; the pulse current is set to 100A at high level and 20A at low level, with a period of 200ms, and each level occupies 100ms; the pulse voltage is generated by a high-frequency generator.

[0014] A continuous feeding method for metal droplet additive manufacturing involves a welding power source supplying a periodically dynamically changing pulsed current to a double-stranded metal wire. The double-stranded metal wire ignites an arc and undergoes melting in a wire melting device. While the molten material is temporarily stored, the high temperature caused by the electric arc raises the internal pressure to a level greater than the external atmospheric pressure, expelling the molten material. A circuit-controlled printing platform carrying a welding base plate moves along a trajectory according to the printing target, achieving a continuous droplet printing effect.

[0015] The beneficial effects of this invention are:

[0016] (1) The present invention utilizes a dynamically controlled printing platform to enable the production of additive products with different shapes and designs.

[0017] (2) The present invention improves the workflow and functionality of metal additive manufacturing, and enables simultaneous material replenishment and discharge. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Other features, objects, and advantages of this invention will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0019] Figure 1 This is a schematic diagram of the apparatus for implementing the additive manufacturing method designed in this invention.

[0020] Figure 2 This is a partially enlarged schematic diagram of a special fused wire device for implementing metal additive manufacturing according to the present invention.

[0021] Figure 3 This is a diagram showing the regular changes in current through the two welding wires, as implemented in this invention.

[0022] Reference numerals: 1. Control circuit; 2. Printing platform; 3. Welding power source; 4. Metal droplet additive manufacturing device; 5. Welding wire feeder; 6. Metal wire inlet; 7. Power-on heat preservation device; 8. Discharge port and metal droplets; 9. Molten metal; 10. Electric arc. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. The following embodiments will help those skilled in the art to further understand this invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of this invention. These all fall within the protection scope of this invention.

[0024] A continuous feeding device for metal droplet additive manufacturing includes a welding wire feeder 5, a welding power source 3, and a metal droplet additive manufacturing device 4; both the welding power source 3 and the welding wire feeder 5 are connected to the metal droplet additive manufacturing device 4; there are two welding wire feeders 5, which feed wire into the metal droplet additive manufacturing device 4 respectively to form a double-strand metal wire.

[0025] The metal droplet additive manufacturing apparatus 4 includes a three-axis movable printing platform 2, a high-frequency generator, a wire melting device, and a control circuit 1. A welding power supply 3 is connected to the high-frequency generator and then to the wire melting device to generate a periodic pulsed current. The control circuit 1 is connected to the printing platform 2, the welding power supply 3, and the welding wire feeder 5. The control circuit 1 includes motion control of the printing platform 2, quantitative control of the pulsed current, and quantitative control of the wire feeding speed of the wire feeder 5. The three-axis movable printing platform 2 faces the wire melting device, and two strands of metal wire are fed into the wire melting device for fusion welding.

[0026] The fusion device includes a energized heat-insulating device 7 composed of a multi-turn energized solenoid coil, a metal wire inlet 6 equipped with a protective electrode, and a protective gas filled therein. The energized heat-insulating device 7 is located outside the fusion device. The double-stranded metal wire is fed into the fusion device through the metal wire inlet 6. A periodic pulsed current is used. When the current is high, the double-stranded metal wire ignites and melts, and the temperature and pressure inside the cavity rise rapidly. When the current is low, the double-stranded metal wire continues to melt due to residual heat, and the temperature inside the cavity decreases gradually. The wire feeding speed of the dual wire feeder changes periodically with the pulsed current. When the current is low, the wire is fed slowly to avoid the welding wire connecting and sticking at the arc initiation point due to slow melting. When the current is high, a higher wire feeding speed is used to ensure that welding wire can be replenished in time when the melting is fast.

[0027] The molten metal 9 is discharged through the bottom of the molten wire device as an outlet and metal droplets 8, and is formed on the printing platform 2.

[0028] Example

[0029] The device is assembled as follows: a 100*250 (cm) general welding workbench, equipped with a three-axis movable printing platform and its moving servo motor, plus low carbon steel grippers to fix the welding wire device on the main workbench; a fixing frame is provided on the outside of the main workbench to fix the general welding power supply and high frequency generator, which are respectively connected to the double welding wire and the spiral coil; in addition, two wire feeders are provided.

[0030] The specific process of this method is as follows:

[0031] Step 1: Lead the two metal wires from the two wire feeders to the wire feeding inlet of the fuse device, introduce protective gas into the fuse device cavity, and control the printing platform to move to the initial design position through the control circuit to prepare for printing.

[0032] Step Two: Controlled by the designed control circuit, the pulse current generated by a general welding power supply and a high-frequency generator is activated, initiating the bimetallic wire melting process. This is followed by automatic wire feeding, controlled by the circuit: a high-level (100A) bimetallic wire melts rapidly, causing a surge in internal gas pressure and faster wire feeding; a low-level (20A) bimetallic wire melts more slowly, causing gas rebound within the cavity and slower wire feeding. This process achieves material replenishment, wire melting, and material discharge.

[0033] Step 3: Control the printing platform to move and print according to the designed product plan.

[0034] Step 4: Follow the process to complete the additive manufacturing of the product.

[0035] Two welding wires, fed by two wire feeders, enter the discharge device through the wire inlet. Under the guidance of the control system, the wire feeders feed the wires at a set speed. Power is supplied to the two welding wires as follows: Figure 3 A regularly changing current is generated and an arc is formed in the fuse device. The molten material is stored in the fuse device and kept warm by the eddy current of the energized solenoid coil. When the current reaches 100A, the air pressure in the fuse device surges, causing the stored molten material to be discharged from the outlet.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A continuous feeding device for metal microdroplet additive manufacturing, characterized in that, It includes a welding wire feeder, a welding power source, and a metal droplet additive manufacturing device; both the welding power source and the welding wire feeder are connected to the metal droplet additive manufacturing device; there are two welding wire feeders, which feed wire into the metal droplet additive manufacturing device to form a double-strand metal wire. The metal droplet additive manufacturing apparatus includes a three-axis movable printing platform, a high-frequency generator, a wire melting device, and a control circuit. A welding power source is connected to the high-frequency generator and then to the wire melting device to generate a periodic pulsed current. The control circuit is connected to the printing platform, the welding power source, and the wire feeder. The control circuit includes motion control of the printing platform, quantitative control of the pulsed current, and quantitative control of the wire feeder's feed speed. The three-axis movable printing platform faces the wire melting device, and two strands of metal wire are fed into the wire melting device for fusion welding. The fuse device includes an energized heat-insulating device composed of a multi-turn energized solenoid coil, a metal wire inlet equipped with a protective electrode, and a protective gas filled therein; the energized heat-insulating device is located outside the fuse device, and the double-stranded metal wire is fed into the fuse device through the metal wire inlet. A periodic pulsed current is used. When the current is high, the double-stranded metal wire arcs and melts, and the temperature and pressure inside the cavity rise rapidly. When the current is low, the double-stranded metal wire continues to melt by relying on the residual heat, and the temperature inside the cavity is gradually reduced. The wire feeding speed of the dual wire feeder changes periodically with the pulse current. When the current is low, the wire is fed slowly to avoid the welding wire from connecting and sticking together at the arc initiation point due to slow melting. When the current is high, a higher wire feeding speed is used to ensure that welding wire can be replenished in time when the melting is fast.

2. The continuous feeding device for metal microdroplet additive manufacturing according to claim 1, characterized in that, The fuse device uses high-temperature resistant insulating materials to ensure the high-temperature fuse process and the temporary preservation of the molten raw material inside the cavity.

3. The continuous feeding device for metal microdroplet additive manufacturing according to claim 1, characterized in that, The metal wire inlet of the fuse device is equipped with a sealing plug made of high-temperature resistant insulating material to isolate the gas inside the cavity from the atmosphere, ensuring the airtightness and stability of the fuse device, and ensuring that when the double welding wires start arcing and fuse, the gas pressure inside the cavity can be increased and the temporarily stored molten material can be squeezed out for printing.

4. The continuous feeding device for metal microdroplet additive manufacturing according to claim 1, characterized in that, The control circuit enables three-dimensional six-axis motion control of the printing platform, thereby controlling the shape of the printed product; it also enables quantitative control of the pulse current and wire feeding speed, ensuring both wire melting efficiency and process safety; the pulse current is set to 100A at high level and 20A at low level, with a period of 200ms, and each level occupies 100ms; the pulse voltage is generated by a high-frequency generator.

5. A continuous feeding method for additive manufacturing of metal microdroplets using the apparatus described in any one of claims 1-4, characterized in that, The welding power source passes a periodically and dynamically changing pulsed current into the twin-strand metal wire, causing the twin-strand metal wire to ignite an arc and undergo melting changes in the wire melting device; while the molten material is temporarily stored, the electric arc causes high temperature, which increases the gas pressure inside the cavity to be greater than the external atmospheric pressure, thus squeezing out the molten material; The circuit-controlled printing platform supports the welding base plate, which moves along a trajectory according to the printing target to achieve continuous droplet printing.

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