Electrohydrodynamic additive manufacturing device and printing method for metallic materials

Abstract

The application relates to a kind of electrohydrodynamic additive manufacturing device and printing method for metal material, manufacturing device includes air pressure sensing and distribution system, three-dimensional displacement mechanism, substrate, annular electrode, metal material storage device, high-voltage direct-current power supply and control system;Substrate and metal material storage device are arranged on three-dimensional displacement mechanism;Substrate and annular electrode are connected with the negative pole of high-voltage direct-current power supply, and metal material storage device is connected with the positive pole of high-voltage direct-current power supply;The inside of metal material storage device is communicated with air pressure sensing and distribution system.The manufacturing device adopts the mode that annular electrode and substrate electrode are combined, organic solvent is used as the matrix of metal powder solution, and the printing process is stacked and deposited layer by layer, so that electrohydrodynamic 3D printing of metal material is realized.

Description

Technical Field

[0001] This invention relates to the fields of metal additive manufacturing and metal powder metallurgy, and particularly to an electrofluid additive manufacturing apparatus and printing method for metal materials. Background Technology

[0002] Electrohydrodynamic (EHDM) devices are used for micro / nano-scale printing of organic solutions and for micro / nano-scale additive manufacturing. By applying a strong electrostatic field at the capillary opening, the meniscus of the solution is deformed under the influence of the electric field, ultimately forming a stable, extremely fine conical jet emission pattern. This conical jet is then used to achieve a series of printing and additive manufacturing processes. Currently, EHDM processes are mostly used for micro / nano-scale printing of organic solutions and sols. In the additive manufacturing of metallic materials, only planar circuit printing using EHDM technology is available, leaving a technological gap in the 3D printing of metallic materials. Summary of the Invention

[0003] To address the technological gap in electrofluid additive manufacturing for 3D printing of metal materials, this invention provides an electrofluid additive manufacturing apparatus for metal materials. It employs a combination of a ring electrode and a substrate electrode. A ring electrode is coaxially arranged below the capillary, with the same potential as the substrate. This maintains the stability of the conical jet and increases the height of the printed part. Furthermore, setting the substrate and the ring electrode to the same potential, or with the substrate potential slightly lower than the ring electrode potential, can to some extent prevent the conical jet from spraying out, thus enabling electrofluid 3D printing of metal materials.

[0004] The technical solution of the present invention is: an electrofluid additive manufacturing apparatus for metallic materials, comprising a pressure sensing and distribution system, a three-dimensional displacement mechanism, a substrate, a ring electrode, a metallic material storage device, a high-voltage DC power supply, and a control system; the substrate and the metallic material storage device are disposed on the three-dimensional displacement mechanism; the substrate and the ring electrode are connected to the negative terminal of the high-voltage DC power supply, and the metallic material storage device is connected to the positive terminal of the high-voltage DC power supply; the interior of the metallic material storage device is connected to the pressure sensing and distribution system.

[0005] Furthermore, the air pressure sensing and distribution system includes an air compressor, a precision pressure reducing valve, and an air delivery pipeline. The high-pressure gas output by the air compressor is reduced in pressure by the precision pressure reducing valve and then input into the metal material storage device to achieve pressurization of the high-temperature resistant injection cylinder and on-demand extrusion of the metal material.

[0006] Furthermore, the metal material storage device includes a capillary printhead, a high-temperature resistant injection cylinder, a heating jacket, a sealing element, and a temperature control device. The capillary printhead is installed at the nozzle of the high-temperature resistant injection cylinder, the heating jacket and temperature control device are arranged outside the high-temperature resistant injection cylinder, and the interior of the high-temperature resistant injection cylinder is connected to the air pressure sensing and distribution system; the sealing element is arranged at the tail end of the high-temperature resistant injection cylinder.

[0007] Furthermore, an air inlet is provided at the center of the seal, and the air inlet is connected to the air supply pipeline of the air pressure sensing and distribution system.

[0008] Furthermore, the annular electrode is installed between the capillary printhead and the substrate, and is coaxially mounted with the capillary printhead in the vertical direction.

[0009] Furthermore, the three-dimensional displacement mechanism includes a two-dimensional displacement platform and a vertical displacement mechanism. The two-dimensional displacement platform is formed by orthogonally splicing two one-dimensional lead screw mechanisms.

[0010] Furthermore, the two-dimensional displacement platform is connected to the substrate; the vertical displacement mechanism is connected to the metal material storage device.

[0011] On the other hand, the present invention provides an electrofluid printing method for metallic materials, characterized by comprising the following steps: preparing a metal solution; generating a metal solution conical jet using the aforementioned electrofluid additive manufacturing apparatus for metallic materials; printing a blank using the metal solution conical jet; and performing post-processing on the blank.

[0012] Further, weigh out a certain mass ratio of organic solvent and metal powder, heat the organic solvent to a molten state, and mix it thoroughly with the metal powder to form a metal solution.

[0013] Furthermore, air pressure is applied to the metal material storage device through an air pressure sensing and distribution system, and a positive electric field is applied between the metal material storage device, the annular electrode, and the substrate to generate a stable metal solution conical jet. The substrate makes a specified displacement movement according to the printing process. After the metal solution conical jet is ejected, it contacts the substrate and solidifies, realizing the layer-by-layer printing of the blank. The printed blank is wrapped with sintering powder and undergoes a multi-stage heating process in a vacuum sintering furnace. The organic solvent in the blank undergoes evaporation and thermal decomposition, and the copper powder undergoes a remelting process to complete the sintering and solidification of the blank.

[0014] The present invention has the following beneficial effects:

[0015] (1) The printing resolution is high, and the size of the Taylor cone jet formed by the metal solution at the capillary opening is much smaller than the inner diameter of the capillary.

[0016] (2) The electrofluid additive manufacturing equipment and printing process are simple. The electrofluid additive manufacturing equipment can be modified to be suitable for 3D additive manufacturing of metal materials.

[0017] (3) Compared with traditional flat plate electrodes, ring electrodes effectively avoid the discharge phenomenon between electrodes, and the generated cone jet is more stable.

[0018] (4) Organic solvents are used as the matrix of metal powder solutions. During the printing process, they are stacked and deposited layer by layer, which solves the problem that traditional electrohydrodynamic printing processes cannot print the three-dimensional structure of metal materials. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the electrofluid additive manufacturing apparatus for metallic materials according to the present invention.

[0020] Figure 2 This is a cross-sectional view of the metal material storage device of the present invention.

[0021] Figure 3 This is a flow chart of the temperature control process for the post-processing of the blank in this invention.

[0022] The above figures include the following reference numerals:

[0023] 10-Two-dimensional displacement platform; 20-Substrate; 30-Ring electrode; 40-Printed part; 50-Metal material storage device; 60-High voltage DC power supply; 51-Capillary print head; 52-Seal; 53-Air inlet; 54-High temperature resistant injection cylinder; 55-Heating jacket. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Example 1

[0028] To address the technological gap in electrofluid additive manufacturing for 3D printing of metal materials, this invention provides an electrofluid additive manufacturing apparatus for metal materials. Traditional electrofluid printing is mostly used for two-dimensional planar printing, primarily because the electrode structure of the device used to generate the solution conical jet limits the printing height. Maintaining a stable, strong electric field between the capillary and the substrate requires a constant spacing, thus the printing height cannot exceed the distance between the substrate and the capillary. To solve this problem, this invention employs a combination of a ring electrode and a substrate electrode. A ring electrode is coaxially arranged below the capillary, with the same potential as the substrate. This maintains the stability of the conical jet while increasing the height of the printed part. Furthermore, setting the substrate and the ring electrode to the same potential, or with the substrate potential slightly lower than the ring electrode potential, can to some extent prevent the conical jet from spraying outwards.

[0029] An electrofluid additive manufacturing apparatus for metallic materials includes a pressure sensing and distribution system, a three-dimensional displacement mechanism, a substrate 20, a ring electrode 30, a metallic material storage device 50, a high-voltage DC power supply 60, and a control system.

[0030] The air pressure sensing and distribution system includes an air compressor, a precision pressure reducing valve, and an air delivery pipeline. The high-pressure gas output from the air compressor is reduced in pressure by the precision pressure reducing valve and then input into the metal material storage device 50 to achieve pressurization of the high-temperature resistant injection cylinder 54 and on-demand extrusion of the metal solution.

[0031] The three-dimensional displacement mechanism includes a two-dimensional displacement platform 10 and a vertical displacement mechanism (used to control the print head to move in the vertical direction).

[0032] The two-dimensional displacement platform 10 includes two one-dimensional lead screw mechanisms, which are installed perpendicularly to each other and connected to the servo controller and the host computer respectively. The two-dimensional displacement platform 10 is connected to the base plate 20, which can drive the base plate 20 to move in a plane. The base plate 20 is a thin copper metal plate and is connected to the negative terminal of the high voltage DC power supply 60.

[0033] The metal material storage device 50 includes a capillary printhead 51, a high-temperature resistant injection cylinder 54, a heating jacket 55, a sealing element 52, and a temperature control device. The high-temperature resistant injection cylinder 54 has a matching capillary printhead 51 installed at its nozzle. The heating jacket 55 and temperature control device are wrapped around the outside of the high-temperature resistant injection cylinder 54, and its tail end is connected to a pressure sensing and distribution system. A sealing element 52 is provided at the tail end of the high-temperature resistant injection cylinder 54. After removing the sealing element 52, printing material can be filled into the high-temperature resistant injection cylinder 54. An air inlet 53 is located at the center of the sealing element 52, connected to an air supply pipeline, and has good airtightness. The internal air pressure of the high-temperature resistant injection cylinder 54 is increased by external air supply, enabling on-demand extrusion of the molten metal. The inner diameter of the capillary nozzle 51 connected to the high-temperature resistant injection cylinder 54 is 250µm to 500µm. Driven by the internal air pressure of the high-temperature resistant injection cylinder 54, the molten metal is extruded from the needle of the capillary printhead 51.

[0034] The capillary printhead 51, made of metal, is connected to the positive terminal of the high-voltage DC power supply 60, and the entire syringe and metal solution are at a high potential. Due to the different inner diameters of the selected capillary printheads 51, the DC voltage required during printing also varies, ranging from 3KV to 5KV.

[0035] The annular electrode 30 is connected to the negative terminal of the high-voltage DC power supply 60. The annular electrode 30 is installed between the capillary printhead 51 and the substrate 20, and is coaxially mounted with the capillary printhead 51 in the vertical direction. The metal material storage device 50 is mounted on the vertical displacement mechanism, and the capillary printhead 51 is moved in the vertical direction through a servo motor driver and a host computer. At the same time, the capillary printhead 51 and the annular electrode 30 maintain a fixed relative position and remain coaxial during the printing process, with a constant height difference.

[0036] The high-voltage DC power supply is a low-power high-voltage power supply that can achieve DC voltage output from 0 to 10KV.

[0037] The control system includes a host computer, servo motor drivers, and 3D printing control software. Through pre-programming, operation instructions are converted into machine code, enabling real-time operation control.

[0038] The vacuum sintering furnace supports a vacuum sintering temperature of 1200℃ and can achieve multi-segment temperature timing control.

[0039] Example 2

[0040] A method for electrofluid printing of metallic materials includes the following steps:

[0041] (1) Preparation of metal solution

[0042] Weigh out an organic solvent and metal powder in a certain mass ratio, heat the organic solvent to a molten state, and mix it thoroughly with the metal powder to form a metal solution.

[0043] In this embodiment, polyethylene glycol crystals and copper powder are weighed at a mass ratio of 3.5:1. The copper powder has a particle diameter of 500 nm. The polyethylene glycol crystals are heated to a molten state and thoroughly mixed with the copper powder. After stirring evenly, the prepared metal solution is transferred to the metal material storage device 50 in the electrohydrocarbon additive manufacturing apparatus.

[0044] (2) Using the electrohydrodynamic additive manufacturing apparatus in Example 1 to generate a metal solution cone jet

[0045] Open the heating jacket 55 outside the metal material storage device 50 to keep the metal solution in the high temperature resistant injection cylinder 54 at around 100°C and maintain the molten state of the metal solution.

[0046] Install the sealing element 52 at the tail of the metal material storage device 50, insert the air pipe into the air inlet 53 on the sealing element 52 and complete the seal, provide compressed gas through the air compressor, output low-pressure gas through the precision pressure reducing valve, and input it into the high-temperature resistant injection cylinder 54 for pressurization through the air inlet 53. By gradually increasing the output air pressure of the precision pressure reducing valve, adjust the pressure value inside the high-temperature resistant injection cylinder 54 so that the internal metal solution reaches the critical extrusion state. After observing that a crescent-shaped liquid surface appears at the tip of the capillary print head 51 and remains stable, fix the output pressure value of the pressure reducing valve.

[0047] Turn on the high-voltage DC power supply 60, apply a positive electric field between the capillary printing nozzle 51, the ring electrode 30, and the substrate 20, and gradually increase the output voltage until the metal solution meniscus at the tip of the capillary printing nozzle 51 bends and contracts into a Taylor cone shape under the action of the electric field force, and a stable cone jet jet mode is achieved. Then stabilize the output voltage value of the high-voltage DC power supply 60.

[0048] (3) Printing blanks using a metal solution cone jet printing method

[0049] The substrate 20 is mounted on the two-dimensional displacement platform 10 below the capillary printing nozzle 51. The substrate 20 performs a specified displacement movement according to the printing process. After the metal solution is ejected in a cone jet, it contacts the substrate 20 and solidifies, thereby realizing the layer-by-layer printing of the blank.

[0050] After the molten metal cone jet stabilizes, an extremely fine molten metal cone jet can be observed ejected from the tip of the capillary print head 51. The molten metal cone jet solidifies immediately upon contact with the substrate 20, realizing the 3D printing of the blank. Combined with the 3D printing software in the host computer planning the printing path, the three-dimensional displacement mechanism is driven to perform the specified movement through the servo motor driver. In this device, the two-dimensional displacement platform 10 at the bottom is the main one performing the specified movement. The substrate 20 and the capillary print head 51 continuously undergo relative displacement. The molten metal cone jet will print layer by layer on the forming substrate 20 and stack up to form a complete three-dimensional part model 40.

[0051] (4) Post-processing of the blanks

[0052] The printed blank is wrapped with sintering powder and undergoes a multi-stage heating process in a vacuum sintering furnace. The organic solvent in the blank undergoes evaporation and thermal decomposition, while the copper powder undergoes a remelting process, thus completing the sintering and solidification of the blank.

[0053] Once the three-dimensional displacement mechanism stops moving, i.e., printing is complete, turn off the high-voltage DC power supply 60 and the precision pressure reducing valve. The conical jet at the tip of the capillary print head 51 will then disappear. Remove the printed part 40. At this point, the printed part 40 is a blank containing organic solvent and requires further post-processing.

[0054] After the printed part 40 is tightly coated with sintering powder, it is placed in a ceramic crucible and then placed in a vacuum sintering furnace for degreasing and sintering post-treatment. The specific process flow is as follows: Figure 3 As shown, the temperature inside the vacuum furnace is initially raised from room temperature to 297°C and held at 297°C for 2 hours to ensure complete evaporation and pyrolysis of the polyethylene glycol organic solvent. The furnace temperature is then further increased to 900°C and held at 900°C for 0.5 hours, after which the part cools with the furnace. Once cooled, the metal part encased in sintering powder is removed, and any remaining sintering powder residue is removed from the surface to obtain the final 3D printed metal part.

[0055] The electrofluid 3D printing method of the present invention combines electrofluid melt printing technology and powder metallurgy technology. By preparing a metal solution with a certain melting point, a metal solution cone jet is formed using an electrofluid additive manufacturing device and applied to the 3D printing of metal parts. Within a suitable temperature range, the metal solution cone jet can achieve a liquid-to-solid transformation during the printing process, realizing the layer-by-layer deposition of materials, thereby achieving the effect of 3D printing.

[0056] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An electrofluid additive manufacturing apparatus for metallic materials, characterized in that: It includes a pressure sensing and distribution system, a three-dimensional displacement mechanism, a substrate (20), a ring electrode (30), a metal material storage device (50), a high-voltage DC power supply (60), and a control system; The substrate (20) and the metal material storage device (50) are mounted on the three-dimensional displacement mechanism; The substrate (20) is connected to the negative terminal of the high voltage DC power supply (60), the ring electrode (30) is connected to the negative terminal of the high voltage DC power supply (60), and the metal material storage device (50) is connected to the positive terminal of the high voltage DC power supply (60). The air pressure sensing and distribution system includes an air compressor, a precision pressure reducing valve, and an air delivery pipeline; The interior of the metal material storage device (50) is connected to the air pressure sensing and distribution system; The metal material storage device (50) includes a capillary printhead (51), a high-temperature resistant injection cylinder (54), a heating jacket (55), a sealing element (52), and a temperature control device. The capillary printhead (51) is installed at the nozzle of the high-temperature resistant injection cylinder (54). The heating jacket (55) and the temperature control device are arranged outside the high-temperature resistant injection cylinder (54). The interior of the high-temperature resistant injection cylinder (54) is connected to the air pressure sensing and distribution system. The sealing element (52) is arranged at the tail of the high-temperature resistant injection cylinder (54). An air inlet (53) is arranged in the center of the sealing element (52). The air inlet (53) is connected to the air supply pipeline of the air pressure sensing and distribution system. The high-pressure gas output from the air compressor is reduced in pressure by a precision pressure reducing valve and then input into the metal material storage device (50) to increase the pressure of the high-temperature resistant injection cylinder (54) and extrude the metal material as needed. The annular electrode (30) is installed between the capillary printhead (51) and the substrate (20), and is coaxially mounted with the capillary printhead (51) in the vertical direction. The three-dimensional displacement mechanism includes a two-dimensional displacement platform (10) and a vertical displacement mechanism. The two-dimensional displacement platform (10) is formed by two one-dimensional lead screw mechanisms orthogonally spliced ​​together. The two-dimensional displacement platform (10) is connected to the substrate (20). The vertical displacement mechanism is connected to the metal material storage device (50).

2. A method for electrofluid printing of metallic materials, characterized in that: Includes the following steps: Weigh out an organic solvent and metal powder in a certain mass ratio, heat the organic solvent to a molten state, and mix it thoroughly with the metal powder to form a metal solution; A metal solution cone jet is generated using the electrofluid additive manufacturing apparatus for metallic materials as described in claim 1; Using a metal molten metal cone jet to print blanks; Post-processing of the blank parts.

3. The electrofluid printing method for metallic materials according to claim 2, characterized in that: Air pressure is applied to the metal material storage device (50) through an air pressure sensing and distribution system; A positive electric field is applied between the metal material storage device (50) and the ring electrode (30), and a positive electric field is applied between the metal material storage device (50) and the substrate (20) to generate a stable metal solution cone jet. The substrate (20) makes a specified displacement movement according to the printing process. After the metal solution cone jet is ejected, it contacts the substrate (20) and solidifies, realizing the layer-by-layer printing of the blank. The printed blank is wrapped with sintering powder and undergoes a multi-stage heating process in a vacuum sintering furnace. The organic solvent in the blank undergoes evaporation and thermal decomposition, and the metal powder undergoes a remelting and solidification process to complete the sintering and solidification of the blank.

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