Continuous material supplementing device for metal microdroplet additive and microdroplet generation control method

Abstract

The invention discloses a continuous material supplementing device for metal microdroplet additive materials and a microdroplet generation control method, the continuous material supplementing in the device is realized by adopting a double-wire pulse current arcing fuse mode and an indirect arc fuse mode, and meanwhile, the extruded metal microdroplets are controlled by utilizing the air pressure change in the device caused by indirect arc. On the basis of metal microdroplet additive manufacturing, a synchronously-controlled wire feeding machine is applied, work of increasing the wire fusing speed, synchronously supplementing raw materials and extruding the additive through air pressure changes is achieved in a matched mode, the technological process of metal additive manufacturing is effectively optimized, and the working efficiency and working performance of metal additive manufacturing are improved.

Description

Technical Field

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

[0002] Metal droplet additive manufacturing technology is an advanced manufacturing technology that builds metal parts layer by layer by precisely controlling the generation, transmission and deposition of tiny metal droplets. Compared with traditional metal additive manufacturing methods, metal droplet additive manufacturing technology has high material utilization, high molding efficiency, can be used for multi-material manufacturing and customized construction, and can achieve higher precision and more complex structures. With the continuous development and improvement of technology, its application scope will continue to expand and show great potential in multiple high-precision manufacturing fields.

[0003] At present, the metal droplet additive technology adopts the technology of eddy current heating molten metal: the metal raw material is transported to a heating device with multiple turns of energized spiral coils, and the metal wire is melted and stored in the discharge device by the eddy current effect. Then, the inert gas is filled into the discharge device to control the air pressure to extrude the molten material to form droplets for stacking printing. It has the characteristics of concentrated energy and good controllability. This additive method is extremely dependent on the melting of the filled metal raw material by the fuse device. However, the fuse process is time-consuming and cannot achieve real-time replenishment of the melt during the additive process. In addition, it is not suitable to pressurize and discharge the material at the same time as the melting of the metal raw material. This not only makes it difficult to control the droplet injection, but also reduces the additive efficiency.

[0004] WAAM (Arc Fuse Additive Manufacturing) is a digital manufacturing technology developed from welding technology, using arc as the energy beam and metal wire as the filling material. WAAM uses arc as the heat source and focuses the energy of metal materials to melt them. The advantages of this fuse technology are high material utilization, high molding efficiency, low equipment cost, and basically no restrictions on the size of simple molding. It is suitable for printing and manufacturing of metal synthetic wire products (such as Ti, Ni, Steel, etc.). Summary of the invention

[0005] The present invention designs a technology based on the metal droplet additive technology, which utilizes the pulse voltage arc fuse technology in WAAM, which can realize the simultaneous operation of fuse, continuous raw material replenishment, and pressurized discharge in the droplet additive process, and designs a device technical solution, aiming to improve the working efficiency and working performance of metal droplet additive manufacturing.

[0006] The present invention provides a continuous feeding device for metal additives and a method for controlling droplet generation by passing a pulse current through a double-strand metal wire to cause arc melting. The method can effectively increase the speed of the fuse to achieve the purpose of optimizing the feeding. When the pulse current acts on the fuse, a wire feeder is used to synchronously transport the wire into the device to achieve the purpose of synchronously replenishing the raw materials. When the pulse current acts on the fuse, high temperature is generated, the temperature in the cavity of the device suddenly increases, and the air pressure is higher than the external air pressure, thereby squeezing the molten metal out of the device to achieve synchronous feeding and discharging. The eddy current heating device wrapped around the fuse device is used to maintain the temperature in the device to ensure that the molten metal is in a flowable liquid state.

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

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

[0009] The metal droplet additive manufacturing device 4 includes a three-axis movable printing platform 2, a high-frequency generator, a fuse device and a control circuit 1; the welding power source 3 is connected to the high-frequency generator and then to the fuse device to form a periodic pulse current, and the control circuit 1 is respectively connected to the printing platform 2, the welding power source 3 and the welding wire feeder 5; the control circuit 1 includes motion control of the printing platform 2, quantitative control of the pulse current and quantitative control of the wire feeding speed of the wire feeder 5. The three-axis movable printing platform 2 is directly opposite to the fuse device, and the double-strand metal wire is fed into the fuse device for melting welding;

[0010] The fuse device comprises an energized heat-insulating device 7 composed of a plurality of turns of energized spiral coils, a metal wire inlet 6 equipped with a protective electrode and a protective gas filled therein; the energized heat-insulating device 7 is arranged outside the fuse device, and a double-strand metal wire is fed into the fuse device through the metal wire inlet 6, and a periodic pulse current is adopted. When the electric level is high, the double-strand metal wire starts arcing and melts, and the air temperature and pressure in the cavity rise rapidly; when the electric level is low, the double-strand metal wire continues to melt by the residual heat, and the air temperature in the cavity is moderately decreased; the wire feeding speed of the double wire feeder changes with the same cycle as the pulse current, and the wire is fed slowly when the electric level is low to avoid the phenomenon that the arc starting point of the welding wire is connected and sticks due to slow melting, and a higher wire feeding speed is used when the current is large to ensure that the welding wire can be replenished in time when the fuse 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 material in the cavity.

[0012] Furthermore, the metal wire inlet 6 of the fuse device is equipped with a sealing plug made of high temperature resistant insulating material to isolate the gas in the cavity from the atmosphere, ensuring the airtightness and stability of the fuse device, and ensuring that when the double welding wires start the fuse, the pressure in the cavity can be increased and the temporarily stored molten material can be squeezed out for printing. The three characteristics are combined to achieve the effect of synchronous fusing and material discharging, and thus the technology of continuous feeding of metal droplet additives can be realized.

[0013] Furthermore, the control circuit realizes three-dimensional six-directional motion control of the printing platform, thereby controlling the shape of the printed product; realizes quantitative control of the pulse current and wire feeding speed, ensuring the efficiency of the fuse while ensuring the safety of the process; the high level of the pulse current is set to 100A, the low level is 20A, the period is 200ms, and the high and low levels each occupy 100ms; the pulse voltage is generated by the high-frequency generator.

[0014] A continuous feeding method for metal droplet additive manufacturing, wherein a welding power source supplies a periodically dynamically changing pulse current to a double-strand metal wire, causing the double-strand metal wire to arc and melt in a fuse device; while the molten material is temporarily stored, the arc causes a high temperature, causing the air pressure in the cavity to rise to a level greater than the external atmospheric pressure, thereby squeezing out the molten material; a circuit-controlled printing platform carrying a welding base plate moves along a trajectory according to a printing target, thereby achieving a continuous droplet printing effect.

[0015] Beneficial results of the present invention:

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

[0017] (2) The present invention improves the workflow optimization and functional optimization of metal additive manufacturing, and realizes the simultaneous feeding and discharging of materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, purposes and advantages of the present invention will become more obvious:

[0019] Figure 1 It is a schematic diagram of a device for implementing the additive method designed by the present invention.

[0020] Figure 2 It is a partially enlarged schematic diagram of a special fuse device for implementing metal additive manufacturing in the present invention.

[0021] Figure 3 It is a diagram of the regularly changing current passing through the double welding wires implemented by the present invention.

[0022] Figure numerals: 1. control circuit, 2. printing platform, 3. welding power supply, 4. metal droplet additive manufacturing device, 5. welding wire feeder, 6. metal wire inlet, 7. power-on insulation device, 8. discharge port and metal droplets; 9. metal melt; 10. electric arc. DETAILED DESCRIPTION

[0023] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

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

[0025] The metal droplet additive manufacturing device 4 includes a three-axis movable printing platform 2, a high-frequency generator, a fuse device and a control circuit 1; the welding power source 3 is connected to the high-frequency generator and then to the fuse device to form a periodic pulse current, and the control circuit 1 is respectively connected to the printing platform 2, the welding power source 3 and the welding wire feeder 5; the control circuit 1 includes motion control of the printing platform 2, quantitative control of the pulse current and quantitative control of the wire feeding speed of the wire feeder 5. The three-axis movable printing platform 2 is directly opposite to the fuse device, and the double-strand metal wire is fed into the fuse device for melting welding;

[0026] The fuse device comprises an energized heat-insulating device 7 composed of a plurality of turns of energized spiral coils, a metal wire inlet 6 equipped with a protective electrode and a protective gas filled therein; the energized heat-insulating device 7 is arranged outside the fuse device, and a double-strand metal wire is fed into the fuse device through the metal wire inlet 6, and a periodic pulse current is adopted. When the electric level is high, the double-strand metal wire starts arcing and melts, and the air temperature and pressure in the cavity rise rapidly; when the electric level is low, the double-strand metal wire continues to melt by the residual heat, and the air temperature in the cavity is moderately decreased; the wire feeding speed of the double wire feeder changes with the same cycle as the pulse current, and the wire is fed slowly when the electric level is low to avoid the phenomenon that the arc starting point of the welding wire is connected and sticks due to slow melting, and a higher wire feeding speed is used when the current is large to ensure that the welding wire can be replenished in time when the fuse is fast.

[0027] The molten metal 9 is discharged through the discharge port and metal droplets 8 at the bottom of the fuse device and is formed on the printing platform 2 .

[0028] Example

[0029] The device is assembled as follows: a 100*250 (unit: cm) general welding workbench equipped with a three-axis movable printing platform and its mobile servo, plus a low-carbon steel clamp to fix the fuse device on the main workbench; the main workbench is equipped with a fixed frame to fix the general welding power supply and high-frequency generator, which are connected to double welding wires and spiral coils respectively; in addition, it is equipped with two wire feeders.

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

[0031] Step 1: Lead out the two strands of metal wires equipped by 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 designed initial position through the control circuit to prepare for printing.

[0032] Step 2: The designed control circuit controls the pulse current generated by the general welding power supply and the high-frequency generator, and the bimetallic wire fuses. Then the automatic wire feeding is turned on. The control circuit realizes: the high-level 100A bimetallic wire melts quickly, the gas pressure in the cavity surges, and the wire feeder feeds the wire faster; the low-level 20A bimetallic wire melts slowly, the gas in the cavity rebounds, and the wire feeder feeds the wire slowly. Then the material replenishment, fuse, and discharge are realized.

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

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

[0035] The two welding wires fed by the two wire feeders are fed into the discharge device through the wire inlet. Under the guidance of the control system, the wire feeders feed the wires according to the set speed plan. The power supply is fed into the two welding wires as follows. Figure 3 The current changes regularly and arcs the fuse in the fuse device. The molten material is stored in the fuse device and kept warm by the eddy current of the energized spiral coil. When the current reaches 100A, the gas pressure in the fuse device surges and the stored molten material is discharged from the discharge port.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A continuous feeding device for metal droplet additive, characterized in that: It comprises a welding wire feeder, a welding power source and a metal droplet additive manufacturing device; the welding power source and the welding wire feeder are both connected to the metal droplet additive manufacturing device; there are two welding wire feeders, which respectively feed wires into the metal droplet additive manufacturing device to form double-strand metal wires; The metal droplet additive manufacturing device comprises a three-axis movable printing platform, a high-frequency generator, a fuse device and a control circuit; the welding power source is connected to the high-frequency generator and then connected to the fuse device to form a periodic pulse current, and the control circuit is respectively connected to the printing platform, the welding power source and the welding wire feeder; the control circuit includes motion control of the printing platform, quantitative control of the pulse current and quantitative control of the wire feeding speed of the wire feeder; the three-axis movable printing platform is directly opposite to the fuse device, and the double-strand metal wire is fed into the fuse device for melting welding; The fuse device comprises an energized heat preservation device composed of multiple turns of energized spiral coils, a metal wire inlet equipped with a protective electrode, and a protective gas filled therein; the energized heat preservation device is arranged outside the fuse device, and a double-strand metal wire is sent to the inside of the fuse device through the metal wire inlet, and a periodic pulse current is adopted. When the electric level is high, the double-strand metal wire starts arcing and melts, and the air temperature and pressure in the cavity rise rapidly. When the electric level is low, the double-strand metal wire continues to melt by residual heat, and the air temperature in the cavity is moderately decreased; The wire feeding speed of the double wire feeder changes in the same cycle as the pulse current. The wire is fed slowly at a low level to avoid the phenomenon of the welding wires being connected and sticking at the arc starting point due to slow melting. When the current is high, a higher wire feeding speed is used to ensure that the welding wire can be replenished in time when the fuse is faster.

2. A continuous feeding device for metal droplet additive 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 material in the cavity.

3. A continuous feeding device for metal droplet additive 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 in the cavity from the atmosphere, thereby ensuring the airtightness and stability of the fuse device and ensuring that when the double welding wires start the fuse, the gas pressure in the cavity can be increased and the temporarily stored molten raw material can be squeezed out for printing.

4. A continuous feeding device for metal droplet additive according to claim 1, characterized in that: The control circuit realizes three-dimensional six-directional motion control of the printing platform, thereby controlling the shape of the printed product; realizes quantitative control of the pulse current and wire feeding speed, ensures the efficiency of the fuse and ensures the safety of the process; the high level of the pulse current is set to 100A, the low level is 20A, the cycle is 200ms, and the high and low levels each occupy 100ms; the pulse voltage is generated by the high-frequency generator.

5. A continuous feeding method for metal droplet additive using the device according to any one of claims 1 to 4, characterized in that: The welding power source feeds a periodically dynamically changing pulse current into the double-strand metal wire, and the double-strand metal wire arcs and melts in the fuse device; while the molten material is temporarily stored, the arc causes a high temperature, causing the gas pressure in the cavity to rise to a level greater than the external atmospheric pressure, squeezing out the molten material; The printing platform controlled by the circuit carries the welding base plate to move along the trajectory according to the printing target, achieving a continuous droplet printing effect.

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