A nozzle device for liquid metal 3D printing

Abstract

This invention provides a nozzle device for liquid metal 3D printing, primarily relating to the field of metal additive manufacturing equipment technology. The nozzle device for liquid metal 3D printing includes an aluminum nitride ceramic body, a metal heating circuit, and an electrically conductive heating lead. Its features include: a dense alumina protective film formed on the surface of the aluminum nitride ceramic body, with the metal heating circuit embedded within; the electrically conductive heating lead is connected to the metal heating circuit, and its connection end is coated with high-temperature ceramic adhesive; a connecting structure is provided on the upper part of the aluminum nitride ceramic body for assembly with the feeding mechanism of the printing equipment; and an optional heat insulation layer can be fitted onto the aluminum nitride ceramic body. This invention integrates the nozzle and heating element into a single component, with the nozzle acting as the heating element in direct contact with the molten metal, resulting in rapid heating. The flow of the molten metal can be controlled by adjusting the heating temperature, achieving a simplified structure, reduced volume, lower energy consumption, and convenient and efficient operation.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing equipment technology, specifically a nozzle device for liquid metal 3D printing. Background Technology

[0002] Liquid metal 3D printing technology, with its unique advantages in the rapid prototyping of complex structural parts, has been widely applied in high-end industries such as aerospace, automotive manufacturing, and electronic components. In the liquid metal 3D printing process, the nozzle device, as the core executing component, directly determines the accuracy, efficiency, and overall energy consumption of the printed product.

[0003] Existing liquid metal 3D printing nozzle devices generally adopt a separate "heating element-insulation layer-nozzle" structure design. This means that a separate heating element heats the nozzle, and an insulation layer reduces heat loss to ensure the nozzle temperature remains above the metal's melting point, meeting the requirement for smooth liquid metal flow. However, this structure has the following significant drawbacks: High energy consumption and low heating efficiency: Due to the assembly gap between the heating element and the nozzle, heat transfer must occur through both radiation and conduction, resulting in significant heat loss during the transfer process. To compensate for this loss and ensure the nozzle reaches the target temperature, the heating element must continuously maintain an operating temperature far above the metal's melting point (for example, for aluminum alloys with a melting point of 650°C, the heating element temperature often needs to reach above 800°C). This not only significantly increases the equipment's energy consumption but also imposes stringent requirements on the high-temperature resistance of the heating element material, limiting the range of material choices and increasing manufacturing costs.

[0004] Large and inflexible printheads: To achieve effective heat preservation, existing devices require a large insulation layer, resulting in a bulky printhead. When printing irregularly shaped parts, thin-walled parts, or complex structures requiring multi-position feeding, the large printhead is difficult to adjust its posture and feeding position flexibly, easily interfering with the printed workpiece or other parts of the equipment. It also reduces material utilization and increases subsequent processing allowances.

[0005] Controlling the flow of molten metal is challenging: Existing devices require additional control components such as valves to regulate the flow and shut-off of molten metal. This not only increases the complexity of the printhead structure and manufacturing costs, but may also lead to seal failure due to wear and tear between the valve and the molten metal, thereby affecting printing accuracy and printhead lifespan.

[0006] Therefore, developing a liquid metal 3D printing nozzle device that is compact, low in energy consumption, and easy to control the flow of liquid metal has become a key requirement for promoting the further development of liquid metal 3D printing technology. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a nozzle device for liquid metal 3D printing. It integrates the nozzle and heating element into a single component, with the nozzle acting as the heating element in direct contact with the molten metal. This results in rapid heating, and the flow of the molten metal can be controlled by adjusting the heating temperature. This achieves the effects of simplified structure, reduced volume, lower energy consumption, and ease of use.

[0008] To achieve the above objectives, the present invention employs the following technical solution: A nozzle device for liquid metal 3D printing includes an aluminum nitride ceramic body, a metal heating circuit, and an electrically conductive heating lead. The aluminum nitride ceramic body has a dense alumina protective film formed on its surface and the metal heating circuit is embedded inside. The electrically conductive heating lead is connected to the metal heating circuit, and the connection end is coated with high-temperature ceramic adhesive. The upper part of the aluminum nitride ceramic body is provided with a connection structure for assembly with the feeding mechanism of the printing equipment. The aluminum nitride ceramic body may also be optionally equipped with a heat insulation layer.

[0009] Furthermore, the metal heating circuit uses a high-melting-point metal paste of tungsten or molybdenum-manganese, which is screen-printed onto an aluminum nitride ceramic casting body, hot-pressed and stacked, and then sintered with the aluminum nitride ceramic casting body at a high temperature of 1650℃. The path of the metal heating circuit is designed according to the nozzle shape, jet hole position and heating power requirements to ensure uniform temperature of the nozzle jet hole and surrounding area, with a temperature difference ≤ ±5℃.

[0010] Furthermore, the thermal conductivity of the aluminum nitride ceramic body is 150-200 W / m. K, the coefficient of thermal expansion is 4.5 × 10⁻⁶. -6 / ℃; The alumina protective film can directly contact liquid metals such as aluminum, copper, silver, and lead, and can resist the corrosion of liquid metals.

[0011] Furthermore, the energized heating lead is made of a high-temperature resistant wire with a temperature resistance rating of not less than 800℃, specifically a nickel-chromium high-temperature resistant wire or an iron-chromium-aluminum high-temperature resistant wire.

[0012] Furthermore, the material of the heat insulation layer is selected according to the melting point of the printed metal and the size of the nozzle structure. If the melting point of the printed metal is below 300°C, the heat insulation layer can be omitted; if the melting point of the printed metal is above 800°C, the heat insulation layer can be selected from mica sheets, calcium silicate boards or nano-ceramic insulation boards.

[0013] Furthermore, the upper connection structure of the aluminum nitride ceramic body is an external thread or flange connection surface, which is assembled with the feeding mechanism of the printing equipment through threaded connection or flange connection. During assembly, a graphite sealing gasket can be used to enhance the sealing performance and prevent liquid metal leakage.

[0014] Furthermore, the aluminum nitride ceramic body is provided with at least one jet hole. When multiple jet holes are provided, the metal heating circuit is provided with an independent heating branch for each jet hole, which can realize single-channel independent control of the flow and cut-off of liquid metal.

[0015] Furthermore, by controlling the heating temperature of the metal heating circuit, the flow and cut-off of liquid metal can be achieved: when the heating temperature is higher than the melting point of the liquid metal, the liquid metal remains liquid and flows out from the jet hole; when the heating temperature is lower than the melting point of the liquid metal, the liquid metal solidifies in the aluminum nitride ceramic body and stops flowing out.

[0016] Compared with the prior art, the beneficial effects of the present invention are: Significantly reduced energy consumption and improved heating efficiency: This invention embeds the metal heating circuit within the aluminum nitride ceramic body, achieving an integrated design of the heating element and nozzle. Heat can be directly transferred to the nozzle jet orifice through the aluminum nitride ceramic body, avoiding heat transfer losses in traditional separate structures. Experimental tests show that, for aluminum alloy printing scenarios, the heating power of this invention's printhead is reduced by 35%-40% compared to existing printheads, and the time to reach the target temperature (650℃) is shortened to half that of existing printheads, significantly reducing equipment energy consumption and improving printing preparation efficiency.

[0017] Reduced nozzle size and increased flexibility: Due to the excellent thermal conductivity of the aluminum nitride ceramic body, there is no need for a large insulation layer, and the overall size of the nozzle is reduced by 50%-60% compared to existing nozzles. In the printing of irregularly shaped parts, the compact nozzle can flexibly adjust the feeding position, reduce interference with the workpiece, and improve material utilization by 20%-25%, making it especially suitable for printing complex thin-walled structural parts.

[0018] The flow of molten metal is easily controlled, extending its service life: By controlling the heating temperature of the metal heating circuit, the flow and shut-off of molten metal can be directly achieved—when the temperature is higher than the metal's melting point, the molten metal remains liquid and flows out smoothly; when the temperature is lower than the metal's melting point, the molten metal solidifies inside the nozzle, achieving flow shut-off. No additional valves or other control components are needed, simplifying the nozzle structure and reducing manufacturing costs. Simultaneously, the alumina protective film and excellent thermal shock resistance of the aluminum nitride ceramic body make the nozzle less prone to damage during repeated heating-cooling cycles, extending its service life by 2-3 times compared to existing nozzles. Attached Figure Description

[0019] Figure 1 This is a perspective view of the single-hole nozzle structure of the present invention; Figure 2 This is a partial cross-sectional view of the single-hole nozzle of the present invention; Figure 3 This is a schematic diagram of the internal cross-sectional structure of the single-hole nozzle of the present invention; Figure 4This is a perspective view of the multi-hole plate-mounted nozzle structure of the present invention; Figure 5 This is a partial cross-sectional view of the multi-hole plate nozzle of the present invention; Figure 6 This is a schematic diagram of the internal cross-sectional structure of the multi-hole plate nozzle of the present invention.

[0020] The labels shown in the attached diagram are: 1. Heating lead wire; 2. Metal heating element; 3. Aluminum nitride ceramic body; 4. Heating lead wire; 5. Metal heating element; 6. Aluminum nitride ceramic body. Detailed Implementation

[0021] The present invention will be further described in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0022] Combined with appendix Figures 1-6 A nozzle device for liquid metal 3D printing includes an aluminum nitride ceramic body, a metal heating circuit, an electrically energized heating lead, and an optional heat insulation layer. Aluminum nitride ceramic body: As the core substrate of the nozzle assembly, its surface naturally forms a dense protective alumina film. This film can directly contact common liquid metals such as aluminum, copper, silver, and lead, and effectively resists their corrosion, ensuring long-term stable operation of the nozzle. The thermal conductivity of the aluminum nitride ceramic body can reach 150-200 W / m. K possesses excellent thermal conductivity, enabling rapid and uniform heat transfer; simultaneously, its coefficient of thermal expansion is only 4.5 × 10⁻⁶. -6 The coefficient of thermal expansion is ℃, which is much smaller than that of common liquid metals. When the nozzle temperature is lower than the metal melting point, the volume shrinkage of the solidified metal is greater than that of the aluminum nitride ceramic body, and will not cause extrusion damage to the nozzle jet orifice.

[0023] Metal heating circuit: High-melting-point metal pastes such as tungsten or molybdenum-manganese are used. These pastes are screen-printed onto an aluminum nitride ceramic casting body according to the nozzle shape and jet orifice position requirements. Subsequently, a hot-pressing lamination process is performed to embed the metal heating circuit within the aluminum nitride ceramic casting body. Finally, sintering is carried out at 1650℃ to form a robust, integrated structure between the metal heating circuit and the aluminum nitride ceramic body. The path design of the metal heating circuit must meet the nozzle heating power requirements, ensuring uniform temperature in the nozzle jet orifice and surrounding area, with a temperature difference controlled within ±5℃.

[0024] Heating lead wire: High-temperature resistant wire (temperature resistance rating not lower than 800℃) is used. The connection end between the wire and the metal heating circuit is coated with high-temperature ceramic adhesive. This high-temperature ceramic adhesive not only achieves good insulation effect, but also enhances the high-temperature stability of the connection part and prevents the connection between the wire and the ceramic body from failing at high temperature.

[0025] Optional insulation layer: Based on the melting point of the printed metal and the nozzle structure size, insulation materials such as mica sheets, calcium silicate boards, or nano-ceramic insulation boards can be selectively installed. When printing low-melting-point metals (such as zinc alloys with a melting point below 300℃), the insulation layer can be omitted; when printing high-melting-point metals (such as steel materials with a melting point above 800℃), installing an insulation layer can further reduce heat loss and lower energy consumption.

[0026] In addition, the upper part of the aluminum nitride ceramic body can be machined with an external thread structure or a flange connection surface, and assembled with the feeding mechanism of the printing equipment through threaded connection or flange connection to ensure connection sealing and prevent liquid metal leakage.

[0027] Example 1: Single-hole nozzle As shown in Figure 1, this embodiment provides a single-hole nozzle device suitable for single-channel liquid metal 3D printing scenarios, and its structure includes: Aluminum nitride ceramic body 3: It is cylindrical in shape, with external threads machined on the upper part. These external threads are threaded to connect with the feeding mechanism of the printing equipment to ensure stable feeding of liquid metal. A circular jet hole is provided at the lower part, with the diameter of the jet hole set to 0.5-2mm according to printing requirements.

[0028] Metal heating element 2: Tungsten metal paste is printed onto an aluminum nitride ceramic casting body using a screen printing process. Its path is distributed in a spiral shape around the jet hole, with 2 layers to meet the heating power requirements (heating power of 50-80W) and ensure uniform temperature around the jet hole.

[0029] Electric heating lead 1: It adopts nickel-chromium high temperature resistant wire (temperature resistance 800℃), and its connection end with the metal heating element 2 is coated with high temperature ceramic glue (model: HT-893) to achieve insulation and high temperature protection.

[0030] Thermal insulation layer: In this embodiment, for aluminum alloy printing (melting point 650℃), a 2mm thick mica sheet is assembled as a thermal insulation layer, which is wrapped around the middle area of ​​the aluminum nitride ceramic body 3 to further reduce heat loss.

[0031] The working process of this embodiment is as follows: Power is supplied to the metal heating element 2 through the energized heating lead 1. The heat generated by the metal heating element is quickly transferred to the jet hole through the aluminum nitride ceramic body 3. When the temperature reaches above 650°C, the liquid aluminum alloy conveyed by the feeding mechanism flows out through the jet hole to achieve printing. When printing needs to be stopped, the power is cut off, the temperature of the metal heating element drops, and the aluminum alloy in the jet hole quickly solidifies to achieve flow stoppage.

[0032] Example 2: Multi-hole plate nozzle As shown in Figure 4, this embodiment provides a multi-hole plate-mounted printhead device, suitable for multi-channel simultaneous printing scenarios, and its structure includes: Aluminum nitride ceramic body 6: The whole is in the shape of a square plate, with 4 circular jet holes (1mm in diameter) evenly distributed on the plate surface; through the cooperation of ceramic pressure plate and graphite sealing gasket, a sealed assembly with the feeding mechanism is achieved to prevent leakage of liquid metal during multi-channel feeding.

[0033] Metal heating element 5: It uses molybdenum-manganese alloy paste, which is printed on aluminum nitride ceramic casting body by screen printing process. Its path is designed as a branch according to the position of the 4 jet holes. Each jet hole has an independent heating branch around it to ensure that the temperature of each jet hole is uniform (temperature difference ≤3℃). The heating power is set to 120-150W to meet the needs of simultaneous heating of multiple channels.

[0034] Heating lead 4: Made of iron-chromium-aluminum high-temperature resistant wire (temperature resistance 1000℃), and its four connection ends with the metal heating element 5 are coated with high-temperature ceramic adhesive (model: HT-893) to ensure insulation performance.

[0035] Thermal insulation layer: In this embodiment, for copper alloy printing (melting point 1083℃), a 3mm thick nano-ceramic thermal insulation board is assembled as a thermal insulation layer, covering the upper surface of the aluminum nitride ceramic body 6, which effectively reduces heat loss at high temperatures.

[0036] The working process of this embodiment is as follows: Power is supplied to the metal heating element 5 through the energized heating lead 4. The heat is transferred to the four jet holes through the aluminum nitride ceramic body 6. When the temperature reaches above 1083°C, the feeding mechanism simultaneously delivers liquid copper alloy to the four channels to achieve multi-channel synchronous printing. If it is necessary to shut down a certain channel, the heating branch corresponding to that channel can be de-energized independently to solidify the copper alloy in that jet hole, thereby achieving independent shut-off of a single channel and improving printing flexibility.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nozzle device for liquid metal 3D printing, comprising an aluminum nitride ceramic body, a metal heating circuit, and electrically conductive heating leads, characterized in that: A dense alumina protective film is formed on the surface of the aluminum nitride ceramic body, and the metal heating circuit is embedded inside. The energized heating lead is connected to the metal heating circuit, and the connection end is coated with high-temperature ceramic adhesive. A connection structure is provided on the upper part of the aluminum nitride ceramic body for assembly with the feeding mechanism of the printing equipment. The aluminum nitride ceramic body can also be optionally equipped with a heat insulation layer.

2. The nozzle device for liquid metal 3D printing according to claim 1, characterized in that: The metal heating circuit uses a high-melting-point metal paste of tungsten or molybdenum-manganese, which is screen-printed onto an aluminum nitride ceramic casting body, hot-pressed and stacked, and then sintered with the aluminum nitride ceramic casting body at a high temperature of 1650℃. The path of the metal heating circuit is designed according to the nozzle shape, jet hole position and heating power requirements to ensure uniform temperature of the nozzle jet hole and surrounding area, with a temperature difference ≤ ±5℃.

3. The nozzle device for liquid metal 3D printing according to claim 1, characterized in that: The thermal conductivity of the aluminum nitride ceramic body is 150-200 W / m. K, the coefficient of thermal expansion is 4.5 × 10⁻⁶. -6 / ℃; The alumina protective film can directly contact liquid metals such as aluminum, copper, silver, and lead, and can resist the corrosion of liquid metals.

4. The nozzle device for liquid metal 3D printing according to claim 1, characterized in that: The heating lead is made of high-temperature resistant wire with a temperature resistance rating of not less than 800℃, specifically nickel-chromium high-temperature resistant wire or iron-chromium-aluminum high-temperature resistant wire.

5. The nozzle device for liquid metal 3D printing according to claim 1, characterized in that: The material of the heat insulation layer is selected according to the melting point of the printed metal and the size of the nozzle structure. If the melting point of the printed metal is below 300°C, the heat insulation layer can be omitted; if the melting point of the printed metal is above 800°C, the heat insulation layer can be selected from mica sheets, calcium silicate boards or nano-ceramic insulation boards.

6. The nozzle device for liquid metal 3D printing according to claim 1, characterized in that: The upper connection structure of the aluminum nitride ceramic body is an external thread or flange connection surface. It is assembled with the feeding mechanism of the printing equipment through threaded connection or flange connection. During assembly, a graphite sealing gasket can be used to enhance the sealing performance and prevent liquid metal leakage.

7. A nozzle device for liquid metal 3D printing according to claim 1, characterized in that: The aluminum nitride ceramic body is provided with at least one jet hole. When multiple jet holes are provided, the metal heating circuit is provided with an independent heating branch for each jet hole, which can realize single-channel independent control of the flow and cut-off of liquid metal.

8. A nozzle device for liquid metal 3D printing according to any one of claims 1-7, characterized in that: By controlling the heating temperature of the metal heating circuit, the flow and cut-off of liquid metal can be achieved: when the heating temperature is higher than the melting point of the liquid metal, the liquid metal remains liquid and flows out from the jet hole; when the heating temperature is lower than the melting point of the liquid metal, the liquid metal solidifies in the aluminum nitride ceramic body and stops flowing out.

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