Metal microdroplet stable spraying control device and using method thereof

Abstract

The invention belongs to the technical field of uniform metal microdroplet spraying deposition forming, and discloses a metal microdroplet stable spraying control device and a using method thereof. The crucible is used for containing a pre-printed solid metal material and melt of the pre-printed solid metal material; the sealing cover is hermetically fixed at the top end of the crucible; the nozzle connecting piece is arranged at the bottom end of the crucible; the nozzle body is arranged in the center of the nozzle connecting piece, and a nozzle hole is formed in the center of the nozzle body; a hydrophobic and hydrophobic area interface is arranged at the preset position of the inner wall of the nozzle hole and used for dividing the inner wall of the nozzle hole into a first wall face area and a second wall face area. Wherein the first wall surface area is close to one side of the outlet end of the nozzle hole and is a non-wetting wall surface; the second wall surface area is far away from one side of the outlet end of the nozzle hole and is a wetting wall surface; the metal microdroplet jetting control assembly is arranged on the sealing cover and extends into the crucible; the stability of the liquid drop forming stage is improved, and therefore rapid, stable and uniform liquid drop spraying is achieved.

Description

Technical Field

[0001] This invention belongs to the field of uniform metal droplet jet deposition forming technology, and specifically relates to a stable jetting control device for metal droplets and its usage method. Background Technology

[0002] Uniform metal droplet jet deposition modeling technology, based on the discrete / stacking principle, achieves direct-write printing of fine parts by steadily jetting uniform metal microdroplets and depositing them point by point, line by line, and surface by surface. It has the advantages of a wide range of raw material selection, equipment integration, and high forming accuracy, and is an additive manufacturing and rapid repair technology with great development potential. However, when using existing metal droplet jetting devices, air bubbles entrained from the nozzle can seriously affect the stability of metal droplet formation, making it impossible to control the stability of metal droplet jetting, thus seriously affecting the printing process.

[0003] Currently, to control the stability of metal droplet ejection, experiments are conducted solely by adjusting back pressure or excitation wave signal parameters over extended periods to find a stable ejection range. For example, reference 1, "Li H, Yang W, Duan Y, et al. Residualoscillation suppression via waveform optimization for stable electrohydrodynamic drop-on-demand printing[J]. Additive Manufacturing, 2022," proposes a waveform optimization method to eliminate residual surface oscillations in electrohydrodynamic drop-on-demand printing. This method involves applying an additional small-amplitude pulse to the piezoelectric ceramic after the pulse period to optimize the waveform. The theoretical optimization scheme is determined using a damped oscillation theory model, resulting in a nearly 100% increase in the frequency of this inkjet printing technology compared to before optimization. Reference 2, "Zhou Y, Qi L, Lian H, et al. Effect of impinging behavior annular jet shielding gas and printing substrate on metal droplet stable ejection[J]. Additive Manufacturing, 2024," further illustrates this approach. The paper 84(000) proposes a method for jetting and depositing metal droplets in a low-oxygen environment using a protective gas, quantifies short-distance parameters, and discusses two airflow modes for airflow-based droplet printing. However, the paper also mentions that during short-distance droplet deposition, the protective gas exhibits a complex annular impingement flow, making it difficult to control the stability of high-temperature metal droplet jetting. Furthermore, the aforementioned methods are extremely labor-intensive, increasing experimental costs and forming time, making early-stage debugging of piezoelectric metal microdroplet jetting printing difficult and hindering part forming. Therefore, there is an urgent need to develop a rapid and stable metal microdroplet jetting control device to meet the requirements of uniform microdroplet jetting in various environments, providing a new method to improve the forming accuracy of complex parts. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present invention provides a metal microdroplet stable jetting control device and its usage method, so as to solve the technical problems that existing means of controlling the stability of droplet jetting are labor-intensive, increase experimental costs and forming time.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a stable metal droplet injection control device, including a crucible, a sealing cap, a metal droplet injection control assembly, a nozzle connector, and a nozzle body; The crucible is used to hold the pre-printed solid metal material and its molten metal; the sealing cap is sealed and fixed to the top of the crucible, and the nozzle connector is located at the bottom of the crucible; the nozzle body is located at the center of the nozzle connector, and the nozzle body has a nozzle hole at its center. A wetted / wetted area interface is provided at a predetermined position on the inner wall of the nozzle orifice. The wetted / wetted area interface is used to divide the inner wall of the nozzle orifice into a first wall surface area and a second wall surface area. The first wall surface area is the side closer to the outlet end of the nozzle orifice and is a non-wetting wall surface. The second wall surface area is the side farther away from the outlet end of the nozzle orifice and is a wetting wall surface. The metal droplet injection control assembly is disposed on the sealing cap and extends into the crucible; wherein the metal droplet injection control assembly is used to force the molten metal to form individual metal droplets at the nozzle body.

[0006] Furthermore, the nozzle body is made of graphite or ceramic material; the first wall area undergoes a predetermined hydrophobic surface treatment to form a non-wetting wall surface.

[0007] Furthermore, the surface of the first wall region is provided with a micron-level hydrophobic coating; wherein the thickness of the micron-level hydrophobic coating is 50μm-100μm.

[0008] Furthermore, the ratio of the distance between the interface of the intimacy region and the inlet end of the nozzle orifice to the distance between the interface of the intimacy region and the outlet end of the nozzle orifice is 1:(0.2~1).

[0009] Furthermore, the metal droplet ejection control assembly includes a piezoelectric transducer, an excitation rod, an excitation plate, a signal generator, and a signal amplifier; The piezoelectric transducer is disposed above the sealing cover, the top end of the excitation rod is connected to the piezoelectric transducer, and the bottom end of the excitation rod extends coaxially into the interior of the crucible; the excitation plate is coaxially disposed inside the crucible and installed at the bottom end of the excitation rod. The output of the signal generator is connected to the input of the piezoelectric transducer via the signal amplifier. The signal generator is used to generate a preset excitation wave signal. The preset excitation wave signal is processed by the signal amplifier and then sent to the piezoelectric transducer.

[0010] Furthermore, the preset excitation wave signal is a negative voltage square wave signal.

[0011] Furthermore, it also includes a nitrogen storage tank; the sealing cover has a back pressure gas inlet, and the outlet of the nitrogen storage tank is connected to the back pressure gas inlet.

[0012] Furthermore, it also includes a heating assembly disposed around the outer perimeter of the crucible.

[0013] The present invention also provides a method of using a metal microdroplet stable injection control device, characterized in that it includes: The pre-printed solid metal material is added into the crucible and heated to melt the pre-printed solid metal material. During the printing process, the metal droplet jet control component is used to force the molten metal to form individual metal droplets at the nozzle body according to the preset excitation cycle. The component to be printed is formed by the deposition of individual metal droplets. Before printing begins and before each preset excitation cycle begins, the free surface of the molten metal in the nozzle orifice is at the interface between the hygroscopic and non-hygroscopic regions.

[0014] Furthermore, at the start of each preset excitation cycle, the metal droplet injection control component can drive the free surface of the molten metal in the nozzle orifice to move in the opposite direction to the outlet end of the nozzle orifice.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The metal droplet stable ejection control device provided by this invention divides the inner wall of the nozzle orifice into a wetted wall surface and a non-wetted wall surface, ensuring that the free liquid surface position of the molten metal in the nozzle orifice remains consistent at the beginning of each excitation cycle. This significantly improves the stability during the droplet formation stage, thereby achieving rapid, stable, and uniform droplet ejection and providing a stable foundation for direct-write printing of fine parts. Specifically, an affinity / reluctance interface is set at a preset position on the inner wall of the nozzle orifice, dividing the inner wall of the nozzle orifice into a non-wetted first wall surface region near the exit end and a wetted second wall surface region away from the exit end. Based on the principle that roughness and wettability generate different adhesion forces on the free liquid surface of the metal, the non-wetted wall surface generates a contractionary wall adhesion force on the liquid surface, while the wetted wall surface generates an outward expansion force. The improved wall adhesion ensures that after the excitation cycle, the liquid surface oscillates at the interface between the wetted and unwetted walls, ultimately stabilizing the liquid surface at the interface between the wetted and unwetted regions. Specifically, it ensures that the melt surface is unwetted around the nozzle, and after the spraying cycle, the liquid surface retracts into the nozzle, stabilizing at the interface between the wetted and unwetted regions. This achieves rapid, stable, and uniform droplet spraying, effectively improving droplet spraying stability. This invention solves the droplet spraying stability problem from a physical perspective by improving the nozzle body structure. It eliminates the need for lengthy adjustments to back pressure or excitation wave signals, significantly saving manpower and reducing experimental costs associated with the adjustment process. It also shortens molding time, improves production efficiency, and lowers overall production costs.

[0016] Furthermore, setting the ratio of the distance between the interface of the wet and dry regions and the inlet end of the nozzle orifice to the distance between the interface of the wet and dry regions and the outlet end of the nozzle orifice to 1:(0.2~1) can effectively balance the retraction effect of the non-wetting wall on the molten metal and the difficulty of spraying. When the ratio is too large, it will weaken the retraction effect of the non-wetting wall on the molten metal; while when the ratio is too small, it will increase the difficulty of spraying the molten metal out of the nozzle orifice.

[0017] Furthermore, the preset excitation wave signal adopts a negative voltage square wave signal, which can ensure that the excitation rod and excitation plate are displaced upward first and then the molten metal is extruded downward, reducing the influence of the excitation rod and excitation plate on the speed of forming molten metal droplets and the entrainment of gas in the nozzle.

[0018] Furthermore, by connecting the outlet of the nitrogen storage tank to the back pressure inlet on the sealing cap, the back pressure effect of nitrogen on the surface of the molten metal is utilized, thereby enabling the molten metal to be squeezed out and self-adjusted to the initial position by the metal micro-droplet injection control component before injection.

[0019] Furthermore, by setting up a heating component, the molten metal in the crucible can be kept at a constant temperature during the spraying process.

[0020] The method of using the metal droplet stable injection control device provided by the present invention possesses all the advantages of the aforementioned metal droplet stable injection control device.

[0021] Furthermore, at the beginning of each preset excitation cycle, the metal droplet injection control component can drive the free liquid surface of the molten metal in the nozzle orifice to move in the opposite direction to the outlet end of the nozzle orifice. By utilizing the velocity of the flow field inside the crucible itself, high-speed droplet injection is achieved, reducing the formation of satellite droplets. In conjunction with the non-wetting wall and wetting wall structure inside the nozzle orifice, the liquid surface is reset after the injection cycle ends. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A cross-sectional view of the metal droplet stable injection control device provided in the embodiment; Figure 2 This is a schematic diagram illustrating the free liquid surface reset principle of the molten metal in the embodiment; Figure 3 This is a schematic diagram illustrating the process of rapid and stable jetting of uniform droplets in the embodiment.

[0024] Among them, 1 crucible, 2 sealing cover, 3 piezoelectric transducer, 4 excitation rod, 5 excitation plate, 6 nozzle connector, 7 nozzle body, 8 heating assembly, 9 signal generator, 10 free liquid surface; 701 interface between wet and dry areas, 702 wetting wall surface, 703 non-wetting wall surface. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] This invention provides a stable metal droplet ejection control device, comprising a crucible 1, a sealing cap 2, a metal droplet ejection control assembly, a nozzle connector 6, and a nozzle body 7; the crucible 1 is used to hold pre-printed solid metal material and its molten state; the sealing cap 2 is sealed and fixed to the top of the crucible 1, and the nozzle connector 6 is disposed at the bottom of the crucible 1; the nozzle body 7 is disposed at the center of the nozzle connector 6, and a nozzle orifice is provided at the center of the nozzle body 7; a cohesive / repulsive interface 701 is provided at a predetermined position on the inner wall of the nozzle orifice. The interface 701 is used to divide the inner wall of the nozzle orifice into a first wall region 702 and a second wall region 703; wherein, the first wall region 702 is near the outlet end of the nozzle orifice and is a non-wetting wall surface; the second wall region 703 is away from the outlet end of the nozzle orifice and is a wetting wall surface; the metal droplet injection control component is disposed on the sealing cover 2 and extends into the crucible 1; wherein, the metal droplet injection control component is used to force the molten metal to form single metal droplets at the nozzle body 7.

[0027] In the above embodiments, by setting a non-wetting interface at a preset position on the inner wall of the nozzle orifice, the inner wall is divided into a non-wetting first wall area and a wetting second wall area. Utilizing the wetting characteristics of different wall surfaces, the molten metal surface oscillates and stabilizes at the interface between the two areas after the excitation cycle, achieving rapid, stable, and uniform droplet ejection. This invention can effectively control the stability of droplet ejection, ensuring that the molten metal surface is non-wetting around the nozzle, and that after the ejection cycle, the surface retracts into the nozzle and stabilizes at the interface, achieving rapid control of stable micro-droplet ejection and improving the stability and efficiency of the printing process.

[0028] The following detailed explanation illustrates the metal microdroplet stable injection control device provided by the present invention through several specific embodiments: Example As attached Figure 1 As shown, this embodiment provides a stable metal droplet injection control device, including a crucible 1, a sealing cap 2, a metal droplet injection control component, a nozzle connector 6, a nozzle body 7, a heating component 8, and a nitrogen storage tank.

[0029] The crucible 1 is used to hold the pre-printed solid metal material and its molten metal; specifically, the crucible 1 is a hollow cylindrical structure with openings at both ends; the sealing cap 2 is sealed and fixed to the top of the crucible 1, and the sealing cap 2 and the crucible 1 are sealed by a threaded connection; the metal microdroplet injection control component is disposed on the sealing cap 2 and extends into the crucible 1; wherein, the metal microdroplet injection control component is used to force the molten metal to form single metal droplets at the nozzle body 7.

[0030] Specifically, the metal droplet injection control assembly includes a piezoelectric transducer 3, an excitation rod 4, an excitation plate 5, a signal generator 9, and a signal amplifier.

[0031] The piezoelectric transducer 3 is disposed above the sealing cover 2. The piezoelectric transducer 3 is used to receive and respond to the injection signal transmitted by the signal amplifier and output mechanical vibration displacement. The mechanical vibration displacement is used to drive the excitation rod 4 to move toward the outlet end of the nozzle orifice of the nozzle body 7 or to move in the opposite direction to the outlet end of the nozzle orifice of the nozzle body 7.

[0032] The excitation rod 4 is located below the piezoelectric transducer 3, and the crucible 1, the sealing cover 2, the piezoelectric transducer 3 and the excitation rod 4 are all coaxially arranged; wherein, the top end of the excitation rod 4 is connected to the piezoelectric transducer 3, and the bottom end of the excitation rod 4 extends coaxially into the interior of the crucible 1.

[0033] The exciter plate 5 is coaxially disposed inside the crucible 1 and installed at the bottom end of the exciter rod 4; wherein the exciter plate 5 and the exciter rod 4 are coaxially and vertically fixedly connected, and the exciter plate 5 and the exciter rod 4 are connected by a thread; preferably, the exciter plate 5 has a disc-shaped structure to increase the area of ​​vibration and improve the spraying effect of metal droplets.

[0034] It should be noted that the bottom end of the excitation rod 4 extends into the molten metal inside the crucible 1 and is positioned near the nozzle inlet area of ​​the nozzle body 7 to transmit vibration to the liquid surface in contact with air inside the nozzle orifice. This allows the molten metal to be forced out of the nozzle orifice through a preset micro-vibration, breaking into individual metal droplets.

[0035] The output terminal of the signal generator 9 is connected to the input terminal of the signal amplifier, and the output terminal of the signal amplifier is connected to the input terminal of the piezoelectric transducer 3. The signal generator 9 is used to generate and send a preset excitation wave signal to the signal amplifier. The signal amplifier is used to convert the preset excitation wave signal into an injection signal and send the injection signal to the piezoelectric transducer 3. The metal droplet injection behavior is achieved by controlling the amplitude, pulse width, and frequency of the preset excitation wave signal. Preferably, the preset excitation wave signal is a negative voltage pulse signal to control the vibration and stabilization of the liquid surface at the interface 701 of the nozzle orifice. Specifically, the preset excitation wave signal adopts a negative voltage square wave signal, which can ensure that the excitation rod and excitation plate first move upward and then squeeze the molten metal downward, reducing the influence of the excitation rod and excitation plate on the speed of forming metal droplets and the entrainment of gas in the nozzle.

[0036] The nozzle connector 6 is disposed at the bottom end of the crucible 1, and the nozzle body 7 is disposed at the center of the nozzle connector 6; specifically, the nozzle connector 6 is coaxially and sealed to the bottom end of the crucible 1, the nozzle connector 6 has a central hole, and the nozzle body 7 is coaxially installed at the central hole of the nozzle connector 6; preferably, the nozzle body 7 is made of graphite or ceramic.

[0037] The nozzle body 7 has a nozzle hole at its center; preferably, the diameter of the nozzle hole is 50μm-500μm; a wetted / wetted area interface 701 is provided at a preset position on the inner wall of the nozzle hole; the wetted / wetted area interface 701 is used to divide the inner wall of the nozzle hole into a first wall area 702 and a second wall area 703; the first wall area 702 is close to the outlet end of the nozzle hole and is a non-wetting wall surface; the second wall area 703 is away from the outlet end of the nozzle hole and is a wetting wall surface.

[0038] Specifically, let A be the distance between the interface 701 of the intimacy region and the inlet end of the nozzle orifice, and let B be the distance between the interface 701 of the intimacy region and the outlet end of the nozzle orifice; then the distance between the interface 701 of the intimacy region and the inlet end of the nozzle orifice and the distance between the interface 701 of the intimacy region and the outlet end of the nozzle orifice satisfy: A:B=1:(0.2~1).

[0039] Specifically, the first wall region 702 undergoes a predetermined hydrophobic surface treatment to form a non-wetting wall surface. Preferably, a predetermined hydrophobic surface treatment process is used to apply a micron-level hydrophobic coating to the surface of the first wall region 702, thereby making the first wall region 702 a non-wetting wall surface. For example, a plasma spraying process is used to uniformly spray a hydrophobic composite ceramic coating onto the surface of the first wall region 702 to form a micron-level hydrophobic coating of a predetermined thickness. The thickness of the micron-level hydrophobic coating is 50μm-100μm. The second wall region 702 is a graphite or ceramic material wall surface, meaning that no surface treatment is required for the wall surface of the second wall region 702, allowing it to maintain its original material surface.

[0040] It should be noted that setting the A:B ratio to 1:(0.2~1) can effectively balance the retraction effect of the non-wetting wall on the molten metal and the difficulty of spraying. When the A:B ratio is too large, it will weaken the retraction effect of the non-wetting wall on the molten metal; while when the A:B ratio is too small, it will increase the difficulty of spraying the molten metal out of the nozzle orifice.

[0041] Specifically, by setting a hydrophobic / wetted zone interface 701 at a preset position on the inner wall of the nozzle orifice, and using the hydrophobic / wetted zone interface 701 to divide the inner wall of the nozzle orifice into a non-wetting wall surface and a wetted wall surface; based on the principle that roughness and wettability produce different adhesion forces on the free liquid surface of the metal, the non-wetting wall surface, such as a micron-level hydrophobic coating of a preset thickness, generates a contractile wall adhesion force on the liquid surface of the molten metal, while the wetted wall surface generates an outward expansion wall adhesion force on the liquid surface of the molten metal; due to the combined effect of the contractile wall adhesion force and the outward expansion wall adhesion force on the liquid surface of the molten metal at the hydrophobic / wetted zone interface 701, after the excitation cycle ends, the free liquid surface 10 of the molten metal oscillates and fluctuates at the interface between the wetted and non-wetting walls, i.e., the hydrophobic / wetted zone interface 701, and finally stabilizes the free liquid surface 10 at the hydrophobic / wetted zone interface 701, thereby achieving rapid, stable and uniform droplet spraying.

[0042] The heating component 8 is disposed around the outer perimeter of the crucible 1. The heating component 8 is used to heat and melt the solid metal material in the crucible 1 to a liquid state through heat conduction, so that the molten metal in the crucible 1 can maintain a constant temperature during the spraying process. The heating component 8 is a heating furnace. The sealing cover 2 is provided with a back pressure gas inlet, and the outlet of the nitrogen storage tank is connected to the back pressure gas inlet. The nitrogen storage tank stores nitrogen at a preset pressure and can deliver nitrogen to the interior of the crucible 1 through the back pressure gas inlet to create back pressure on the molten metal in the crucible 1. By controlling the inlet pressure during the metal droplet spraying debugging, the metal droplet spraying control component is used to make the molten metal spray out of the nozzle hole to form a single metal droplet and enable it to self-adjust to the initial position.

[0043] It should be noted that a three-dimensional substrate to be printed is disposed below the nozzle body 7, and a gas flow channel is formed between the nozzle body 7 and the three-dimensional substrate to be printed, which is used to control the stability of the metal droplets ejected from the nozzle orifice and the flight deposition accuracy of the metal droplets; in addition, the flight deposition process of the metal droplets is carried out in a low oxygen nitrogen environment to prevent the metal droplets from oxidizing and deteriorating.

[0044] The metal droplet stable jetting control device described in this embodiment can achieve metal droplet printing with maximum utilization of limited materials in different environments. Specifically, by improving the inner wall structure of the nozzle body, the inner wall of the nozzle orifice is divided into a wetting wall and a non-wetting wall using a hydrophobic interface. Displacement is achieved by transmitting an excitation wave signal to the excitation rod, and pressure is applied to the molten metal surface inside the crucible using back pressure, forcing the formation of metal droplets. After each excitation cycle, the liquid surface recoils and stabilizes at a predetermined position in the nozzle orifice. This solves the problems of long-term unstable jetting and debugging before printing in existing devices, which result in high experimental costs for crucibles and raw materials, and the issue of uniform droplet jetting in microgravity environments. The non-wetting wall is coated with a hydrophobic composite ceramic coating, which effectively overcomes the unstable jetting phenomenon caused by high-temperature melt wetting and bubble entrapment during printing. This ensures that the liquid surface position in the nozzle flow field remains consistent at the beginning of each excitation cycle, preventing irregular changes in the liquid surface that severely affect stable jetting.

[0045] Usage instructions and working principle: The method of using the metal microdroplet spraying device described in this embodiment includes adding pre-printed solid metal material into crucible 1 and heating crucible 1 to melt the pre-printed solid metal material; during the printing process, using the metal microdroplet spraying control component, according to a preset excitation cycle, the molten metal is forced to form individual metal droplets at the nozzle body 7, thereby forming the component to be printed through the deposition of individual metal droplets; wherein, before the start of printing and before the start of each preset excitation cycle, the free liquid surface 10 of the molten metal in the nozzle orifice is at the interface 701 of the affinity and non-affinity regions; at the start of each preset excitation cycle, the metal microdroplet spraying control component can drive the free liquid surface 10 of the molten metal in the nozzle orifice to move in the opposite direction to the outlet end of the nozzle orifice, using the velocity of the flow field inside crucible 1 to achieve high-speed droplet spraying, reducing the formation of satellite droplets, and in conjunction with the non-wetting wall and wetting wall structure inside the nozzle orifice, the liquid surface is reset after the spraying cycle ends.

[0046] Specifically, the usage process includes the following steps: Step 1: Analyze the structural characteristics of the component to be formed, and select a nozzle body 7 with a suitable nozzle orifice diameter according to the forming accuracy requirements; wherein, the nozzle orifice diameter is selected as 50μm-500μm; wherein, the first wall area 702 of the nozzle body 7 is subjected to hydrophobic surface treatment, such as forming a 50μm-100μm micron-level hydrophobic coating on the first wall area 702 using plasma spraying process, so that the first wall area 702 forms a non-wetting wall surface; the crucible 1, excitation rod 4, excitation plate 5, nozzle connecting assembly 6 and nozzle body 7 are ultrasonically cleaned; the surface of the pre-printed solid metal material is cleaned to remove surface oxides and impurities.

[0047] Step 2: Assemble all components to form a stable metal droplet ejection control device; then, add the pre-printed solid metal material into crucible 1.

[0048] Step 3: Set the heating temperature of the heating component 8 and start it. Melt the pre-printed solid metal material in the crucible 1 by heat conduction and keep it at the preset temperature for a preset time. Adjust the excitation rod 4 to move downward to expel the gas in the crucible 1. Continue to adjust the excitation rod 4 to move downward so that the bottom end of the excitation rod 4 extends into the interior of the molten metal in the crucible 1, ensuring that the molten metal fills the nozzle body 7. Then, keep the excitation rod 4 stationary so that the free liquid surface 10 of the molten metal is maintained at the interface 701 of the intermolecular and nonterminal regions.

[0049] Step 4: Turn on the signal generator 9 to generate a preset excitation wave signal according to the preset excitation cycle; after the preset excitation wave signal is processed by the signal generator, it is applied to the piezoelectric transducer 3 to generate micron-level mechanical vibration; then, the mechanical vibration is transmitted to the molten metal in the crucible 1 through the excitation rod 4 and the excitation plate 6, and combined with the back pressure formed by the nitrogen released from the nitrogen storage tank, the free liquid surface 10 of the metal droplet at the nozzle body 7 is forced to vibrate to generate a single metal droplet; through the deposition of the single metal droplet, the component to be printed is formed; wherein, by adjusting the amplitude, pulse and frequency of the preset excitation wave signal, a stable printing time cycle is tested and achieved, and the thickness of different micron-level hydrophobic coatings can be appropriately changed for operation.

[0050] In this embodiment, at the beginning of each preset excitation cycle, the excitation rod 4 is first controlled to vibrate upward, so that the gas-liquid contact surface contracts into a semi-elliptical shape within the nozzle orifice; then the excitation rod 4 is controlled to vibrate downward, forcing the molten metal surface to be squeezed out from the nozzle orifice and thus forming metal droplets; at the end of the excitation cycle, the ejected liquid naturally breaks into droplets due to inertial force, reducing the violent fluctuations that occur when the liquid surface retracts to the nozzle body 7, quickly completing the liquid surface reset, and ensuring the droplet ejection stability in the next excitation cycle.

[0051] It should be noted that, as shown in the attached document Figure 2 As shown, attached Figure 2 The diagram illustrates the principle of free liquid surface reset of molten metal. During the printing process, after receiving the jet signal, the piezoelectric transducer 3 outputs micron-level mechanical vibration to the excitation rod 4. The excitation rod 4 transmits the vibration to the nozzle body 7. During the first excitation cycle, the molten metal in the crucible 1 is transformed from a static to a dynamic flow field due to the force transmitted by the excitation motion. At this time, under the influence of the combined force of the wetting and non-wetting walls, the free liquid surface 10 of the molten metal is maintained at the interface 701 of the affinity and non-affinity regions, as shown in the attached diagram. Figure 2 As shown in (a); and, before the start of each excitation cycle, it is also affected by the combined force of the wetting and non-wetting walls, so that the free liquid surface 10 of the molten metal can always be kept in the same position, improving the stability of uniform droplet spray; as shown in the appendix Figure 2 As shown in (b), after the ejected molten metal breaks into single metal droplets, the undropped molten metal retracts into the nozzle orifice. Because the wetted wall of the nozzle orifice prevents the liquid from continuing to retract into the crucible, the unwetted wall drives the liquid surface to retract into the nozzle, causing the undropped molten metal to start oscillating at the gas-liquid interface. The amplitude of the oscillation gradually decreases and eventually stops, thereby suppressing the generation of satellite droplets. Finally, under the combined action of the frictional force between the liquid and the wall, it gradually returns to the initial position of the ejection, that is, it is maintained at the interface 701 of the intermolecular and nonterminal regions, thus achieving uniform droplet ejection and rapid and stable printing.

[0052] It should also be noted that, as attached Figure 3 As shown, attached Figure 3 The diagram below illustrates the process of rapid and stable jet formation of uniform droplets; see attached diagram. Figure 3 As shown in (a), at the beginning of each preset excitation cycle, the preset excitation signal is set to a negative voltage pulse signal, and a jet signal is generated through a signal amplifier. This signal acts on the piezoelectric transducer 3, outputting micron-level mechanical vibration to the excitation rod 4. This causes the excitation rod 4 to vibrate in the opposite direction to the outlet end of the nozzle orifice, thereby driving the free liquid surface 10 of the molten metal in the nozzle orifice to move in the opposite direction to the outlet end of the nozzle orifice. At this time, the shape of the free liquid surface 10 shrinks from a planar circle inward to a three-dimensional semi-ellipse; as shown in the attached figure. Figure 3 As shown in (b), under the continuous action of the preset excitation signal, the excitation rod vibrates towards the outlet end of the nozzle orifice, forcing the molten metal to be ejected from the nozzle orifice, completing one excitation cycle; from the attached Figure 3 As shown in (c), the droplet breaks naturally due to the inertial force of the ejected liquid, reducing the influence of mechanical vibration on the droplet breaking process, and thus reducing the influence of liquid vibration retracting into the nozzle orifice on the spraying; from the attached Figure 3 As shown in (d), after the excitation cycle ends, the improved nozzle resets the liquid surface and stabilizes it quickly, improving the droplet ejection stability in the next excitation cycle and quickly achieving uniform droplet stable ejection printing. In addition, after the printing process ends, the ejection signal is stopped, the three-dimensional substrate stops moving, and the ejection device is cleaned after the device cools down.

[0053] The metal microdroplet stable jetting control device of this invention divides the inner wall of the nozzle orifice into a wetting region and an unwetting region by setting a micron-level hydrophobic coating on the nozzle body to form a non-wetting wall surface. Secondly, the vibration mode of the excitation rod is modified to vibrate upwards first and then downwards, reducing the impact of the excitation rod displacement on the liquid tearing and droplet formation process. Mechanical vibration pressure is applied to the feeding area by the excitation plate, combined with the back pressure generated by nitrogen gas, to fill the crucible interior with molten metal and ensure that the molten metal surface is unwetted around the nozzle. After the jetting cycle ends, the liquid surface retracts into the nozzle orifice, stabilizing at the interface between the wetting and unwetting regions, thus achieving rapid and stable microdroplet jetting control. Furthermore, by optimizing the excitation wave signal and the method of generating airflow channels around the nozzle orifice, the influence of the liquid on the flow field during the first excitation cycle can be significantly reduced, preventing large fluctuations after the liquid surface retracts into the nozzle, improving the stability of the droplet formation stage, and achieving gas region control during droplet flight. This provides a feasible improvement and optimization for a rapid and stable jetting microdroplet printing device.

[0054] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A stable injection control device for metal microdroplets, characterized in that, Includes a crucible (1), a sealing cap (2), a metal droplet injection control assembly, a nozzle connector (6), and a nozzle body (7). The crucible (1) is used to hold the pre-printed solid metal material and its molten metal; the sealing cap (2) is sealed and fixed to the top of the crucible (1); the nozzle connector (6) is set at the bottom of the crucible (1); the nozzle body (7) is set at the center of the nozzle connector (6); and the nozzle body (7) has a nozzle hole at its center. A non-wetting area interface (701) is provided at a preset position on the inner wall of the nozzle orifice. The non-wetting area interface (701) is used to divide the inner wall of the nozzle orifice into a first wall area (702) and a second wall area (703). The first wall area (702) is close to the outlet end of the nozzle orifice and is a non-wetting wall surface. The second wall area (703) is far away from the outlet end of the nozzle orifice and is a wetting wall surface. The metal droplet injection control assembly is disposed on the sealing cap (2) and extends into the crucible (1); wherein the metal droplet injection control assembly is used to force the molten metal to form single metal droplets at the nozzle body (7).

2. The metal microdroplet stable injection control device according to claim 1, characterized in that, The nozzle body (7) is made of graphite or ceramic material; the first wall area (702) is formed into a non-wetting wall by a predetermined hydrophobic surface treatment.

3. The metal microdroplet stable injection control device according to claim 2, characterized in that, The surface of the first wall region (702) is provided with a micron-level hydrophobic coating; wherein the thickness of the micron-level hydrophobic coating is 50μm-100μm.

4. The metal microdroplet stable injection control device according to claim 1, characterized in that, The ratio of the distance between the interface of the intimacy region (701) and the inlet end of the nozzle hole to the distance between the interface of the intimacy region (701) and the outlet end of the nozzle hole is 1:(0.2~1).

5. The metal microdroplet stable injection control device according to claim 1, characterized in that, The metal droplet injection control assembly includes a piezoelectric transducer (3), an excitation rod (4), an excitation plate (5), a signal generator (9), and a signal amplifier; The piezoelectric transducer (3) is disposed above the sealing cover (2), the top end of the excitation rod (4) is connected to the piezoelectric transducer (3), and the bottom end of the excitation rod (4) extends coaxially into the interior of the crucible (1); the excitation plate (5) is coaxially disposed inside the crucible (1) and installed at the bottom end of the excitation rod (4); The output of the signal generator (9) is connected to the input of the piezoelectric transducer (3) via the signal amplifier. The signal generator (9) is used to generate a preset excitation wave signal. The preset excitation wave signal is processed by the signal amplifier and then sent to the piezoelectric transducer (3).

6. The metal microdroplet stable injection control device according to claim 5, characterized in that, The preset excitation wave signal is a negative voltage square wave signal.

7. The metal microdroplet stable injection control device according to claim 1, characterized in that, It also includes a nitrogen storage tank; the sealing cover (2) is provided with a back pressure gas inlet, and the outlet of the nitrogen storage tank is connected to the back pressure gas inlet.

8. The metal microdroplet stable injection control device according to claim 1, characterized in that, It also includes a heating assembly (8) which is disposed around the outer periphery of the crucible (1).

9. A method of using the metal microdroplet stable injection control device as described in any one of claims 1-8, characterized in that, include: The pre-printed solid metal material is added into the crucible (1) and the crucible (1) is heated to melt the pre-printed solid metal material. During the printing process, the metal droplet jet control component is used to force the molten metal to form single metal droplets at the nozzle body (7) according to the preset excitation cycle, thereby forming the component to be printed through the deposition of single metal droplets; Before printing begins and before each preset excitation cycle begins, the free surface (10) of the molten metal in the nozzle orifice is located at the interface (701) of the intermolecular and nontermolecular regions.

10. The method of using the metal microdroplet stable injection control device according to claim 9, characterized in that, At the start of each preset excitation cycle, the metal droplet injection control component can drive the free surface (10) of the molten metal in the nozzle orifice to move in the opposite direction to the outlet end of the nozzle orifice.

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