Additive manufacturing equipment and method for magnesium alloy liquid continuous injection molding annular part

Abstract

The invention provides additive manufacturing equipment and method for a magnesium alloy liquid continuous injection molding annular part, and mainly relates to the field of metal material additive manufacturing equipment. The invention discloses additive manufacturing equipment and method for a magnesium alloy liquid continuous injection molding annular part, and the additive manufacturing equipment comprises a crucible smelting assembly arranged in an upper vacuum cavity, a liquid injection printing assembly which is arranged in a lower vacuum cavity and communicates with the crucible smelting assembly, and a controller. A three-dimensional motion platform located below the liquid jet printing assembly is arranged in the lower vacuum cavity, and an annular mold with an opening in the top face is arranged at the top of the three-dimensional motion platform. The device has the beneficial effects that the hollow graphite ring piece and the nozzles distributed in an annular array mode are adopted, uniform spraying of magnesium liquid to the annular mold is achieved, the forming efficiency and the quality stability are improved, and the device is particularly suitable for manufacturing large-diameter annular pieces.

Description

Technical Field

[0001] The invention mainly relates to the field of additive manufacturing equipment for metal materials, specifically the additive manufacturing equipment and method for continuous injection molding of ring parts using magnesium alloy liquid. Background Art

[0002] As the lightest engineering metal material, magnesium alloys offer advantages such as high specific strength, excellent damping properties, and strong electromagnetic shielding capabilities, and hold broad application prospects in aerospace, automotive, electronics, and other fields. This is particularly true for annular structural components, such as engine cylinder liners and bearing races. Traditional manufacturing processes (such as casting and forging) are plagued by complex processes, low material utilization, and difficulty in creating complex structures.

[0003] A Chinese patent, publication number CN108515175A, discloses a magnesium alloy slurry and a printing method thereof. The slurry comprises, by weight, 5-50% magnesium alloy particles, 10-40% polylactic acid particles, and the balance additives. The additives consist of a solvent, a consistency modifier, an active agent, and a thixotropic agent. The magnesium alloy particles are AZ31 magnesium alloy with a particle size of 25-38 μm, and the polylactic acid particles are a polymer with a molecular weight of 10,000-20,000, a particle size of 0-10 μm, and a decomposition temperature of 200-220°C. The method involves injecting the prepared magnesium alloy slurry into a reservoir, applying pressure to uniformly force the slurry through a feed trough and into an ejection valve body. The slurry is then rapidly ejected into droplets by impacting a piezoelectric ceramic. This technical solution, through the printing and control of the magnesium alloy slurry, provides a new method for 3D printing of magnesium alloy-polylactic acid composites.

[0004] However, this technology has the following defects when used in practice: 1. The injection system adopts a single nozzle design, which makes it difficult to achieve uniform molding of the ring parts, and easily leads to local uneven thickness and structural defects; 2. Lack of precise control of the magnesium liquid injection process, especially the dynamic adjustment of pressure and flow rate, affects the stability of molding quality; 3. When using the point spray forming method, the continuity of magnesium alloy cladding is poor, which can easily lead to uneven stress distribution in the magnesium alloy and deterioration of alloy performance. Summary of the Invention

[0005] In order to address the shortcomings of the existing technology, the invention provides equipment and methods for additive manufacturing of ring parts by continuous injection molding of magnesium alloy liquid. Through innovative structural design and precise process control, efficient and high-quality additive manufacturing of magnesium alloy ring parts is achieved.

[0006] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions: Additive manufacturing equipment for magnesium alloy liquid continuous jet molding annular parts, comprising: a crucible melting assembly disposed in an upper vacuum chamber, a liquid jet printing assembly disposed in a lower vacuum chamber and connected to the crucible melting assembly, and a controller; a three-dimensional motion platform disposed in the lower vacuum chamber below the liquid jet printing assembly; and a ring-shaped mold with an open top surface disposed on top of the three-dimensional motion platform. The crucible smelting assembly includes: a smelting crucible, a release mechanism, and an annular filter screen. The smelting crucible is arranged in the upper vacuum chamber, and the smelting crucible is connected to the liquid jet printing assembly through a guide tube. The release mechanism is used to control the opening and closing of the guide tube, and the annular filter screen is used to filter the magnesium liquid entering the guide tube. The liquid jet printing assembly includes: a hollow graphite ring and a nozzle. The hollow graphite ring is fixedly connected to the melting crucible through a number of evenly distributed flow guide tubes. The bottom surface of the hollow graphite ring is provided with a number of nozzles distributed in a ring array. A liquid level detector and a temperature monitor are provided in the melting crucible.

[0007] The upper vacuum chamber and the lower vacuum chamber are respectively provided with vacuum pumps, and the upper vacuum chamber is connected to an inert gas source to provide inert gas protection therein.

[0008] A condensation table is provided on the three-dimensional motion platform, and a flow channel for the circulation of coolant is provided in the condensation table. Through the mutual cooperation between the liquid jet printing component, the three-dimensional motion platform, and the condensation table, the magnesium liquid can be spread over a large area in the annular mold and continue to remain semi-solid at the printing interface, thereby achieving metallurgical bonding of the corresponding printing areas of each nozzle.

[0009] The spacing between adjacent nozzles is an adjustable spacing set according to the fluidity of the magnesium liquid and the printing accuracy, and the aperture is an adjustable aperture set according to the injection flow rate requirement; the injection flow rate of the nozzle is calculated by the formula v∝(P0+P1-F) / μ, where P0 is the static pressure of the magnesium liquid by its own weight, P1 is the argon pressure input into the upper vacuum chamber, F is the surface tension of the metal liquid in the nozzle, and μ is the viscosity of the magnesium liquid.

[0010] The release mechanism includes a stopper rod, an electric actuator, and a clamp arm. The electric actuator is installed in the smelting crucible, and the stopper rod and the electric actuator are connected as a whole through the clamp arm. Driven by the electric actuator, the stopper rod performs vertical linear motion to control the opening and closing of the guide tube. The flow rate of the magnesium liquid can be changed by changing the opening degree of the stopper rod and the guide tube.

[0011] The controller includes: a motion control unit and a general control unit, a pressure closed-loop control module and a speed matching control module, wherein: the motion control unit is connected to the general control unit and transmits motion information of the three-dimensional motion platform, and the general control unit is respectively connected to the release mechanism and the vacuum pump and transmits information on the release mechanism movement and the vacuum pump opening and closing; The pressure closed-loop control module is connected to the argon gas source of the upper vacuum chamber and the liquid level detector signal of the melting crucible, and automatically adjusts the argon pressure P1 according to the real-time liquid level height H, so that the total pressure P=P0+P1 meets the injection condition of PF>0; The speed matching control module is connected to the driving mechanism of the three-dimensional motion platform and the flow monitoring signal of the nozzle. It dynamically adjusts the up and down movement speed of the platform according to the measured injection flow rate to ensure that the spreading thickness of the magnesium liquid in the annular mold matches the solidification rate.

[0012] The heating mechanism of the hollow graphite ring and the nozzle includes a resistance heating element or an induction heating coil, and the preheating temperature range is 300-500° C. to ensure that the magnesium liquid maintains liquid fluidity and avoids overheating and oxidation when flowing through.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. Annular multi-nozzle design: The use of hollow graphite rings and annular array-distributed nozzles achieves uniform spraying of magnesium liquid on the annular mold, improving molding efficiency and quality stability. It is especially suitable for the manufacture of large-diameter annular parts. 2. Precise process control: Through pressure closed-loop control and speed matching control, the dynamic matching of the magnesium liquid injection flow rate and the platform movement speed is achieved, ensuring the consistency of the magnesium liquid spreading thickness and solidification rate of each layer, and improving the molding accuracy; 3. Semi-solid forming process: Through the precise temperature control of the condensation table, the magnesium liquid is kept in a semi-solid state at the printing interface, achieving metallurgical bonding of adjacent spray layers and improving the mechanical properties of the ring part; 4. Full-process protection: The dual vacuum chamber design and inert gas protection effectively prevent the oxidation and contamination of magnesium liquid, and improve the purity and forming quality of magnesium alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the invention structure; Figure 2 It is a structural diagram of the invented hollow graphite ring; Figure 3 1 is a metallographic diagram of the magnesium alloy of the embodiment.

[0015] Numbers shown in the accompanying drawings: 10, upper vacuum chamber; 20, crucible melting assembly; 201, melting crucible; 202, annular filter cylinder; 203, guide tube; 30, lower vacuum chamber; 40, liquid jet printing assembly; 401, hollow graphite ring; 402, nozzle; 50, three-dimensional motion platform; 501, annular mold; 502, condensation table; 60, release mechanism; 601, stopper rod; 602, electric actuator; 70, vacuum pump. DETAILED DESCRIPTION

[0016] The invention will be further described with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are intended only to illustrate the invention and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of the invention, those skilled in the art may make various changes or modifications to the invention, and that such equivalent forms also fall within the scope defined in this application.

[0017] Example: Additive manufacturing equipment and method for continuous injection molding of magnesium alloy ring parts like Figure 1-3 As shown, the additive manufacturing equipment and method for continuous injection molding of magnesium alloy liquid ring parts, the specific structure of which includes: The upper vacuum chamber 10 and the lower vacuum chamber 30 are sealed together to form a closed environment, each evacuated by a vacuum pump 70. A crucible smelting assembly 20 is located within the upper vacuum chamber 10 for smelting magnesium alloy raw materials. The smelting crucible 201 is made of a material that is resistant to high temperatures and corrosion from the magnesium liquid. An annular filter 202 is located within the crucible to effectively filter impurities from the magnesium liquid. The stopper 601 of the release mechanism 60 cooperates with the flow conduit 203, and the opening and closing of the flow conduit 203 and the flow rate are controlled by an electric actuator 602.

[0018] The lower vacuum chamber 30 houses a liquid jet printing assembly 40 and a three-dimensional motion platform 50. A hollow graphite ring 401 connects to the crucible 201 via evenly distributed flow tubes 203, ensuring uniform flow of molten magnesium. The annular array of nozzles 402 on the bottom surface can be adjusted in spacing and aperture based on the magnesium alloy's material properties and molding requirements. A ring mold 501 on the three-dimensional motion platform 50 receives the injected molten magnesium, and coolant channels within the condensation stage 502 precisely control the mold temperature.

[0019] The controller automatically controls the entire equipment through various control modules. The closed-loop pressure control module adjusts the argon pressure in real time based on the liquid level in the crucible 201 to ensure stable magnesium liquid injection. The speed matching control module dynamically adjusts the platform's speed based on the nozzle flow rate to ensure molding quality.

[0020] The working method steps are as follows: S1: Preprocessing stage Magnesium alloy raw materials (magnesium, aluminum, zinc, manganese, cerium, thorium, and a small amount of zirconium or cadmium) are placed into the melting crucible 201. The heating device is turned on. Argon gas is introduced into the upper vacuum chamber to protect the oxygen content to 7ppm. The temperature is raised to 750°C for melting. Refining and slag removal are then performed. After sampling and testing for qualified components, the temperature is lowered to 25°C for printing. Close the upper vacuum chamber 10 and seal it, and introduce argon gas to a pressure of P1 = 0.1 MPa; The heating mechanism of the hollow graphite ring 401 and the nozzle 402 is started and preheated to 400° C. At the same time, a 40° C. coolant is introduced into the condensation table 502 to establish a cooling cycle.

[0021] S2: Filling and injection control stage The electric actuator 602 lifts the stopper rod 601 upward, opening the guide tube 203. The magnesium liquid is filtered through the annular filter cylinder 202 and flows into the hollow graphite ring 401. When the liquid level detector detects that the magnesium liquid in the liquid storage tank reaches 80%-90% of the set volume, the stopper rod is stopped from being lifted, and the opening of the guide tube 203 is kept constant. The pressure closed-loop control module monitors the liquid level H of the melting crucible in real time and automatically adjusts the argon pressure P1 so that the total pressure P=ρgH+P1 (ρ is the density of the magnesium liquid, g is the acceleration of gravity) satisfies P>F, driving the magnesium liquid to be ejected from the nozzle 402 at a flow rate of 0.7 m / s.

[0022] S3: Ring forming stage The three-dimensional motion platform 50 moves downward at a speed of 3 mm / s, synchronously receiving the magnesium liquid sprayed by the nozzle, and stacking it layer by layer in the annular mold 501; The speed matching control module calculates the platform movement speed in real time based on the nozzle flow rate, ensuring that the thickness of each layer of magnesium liquid is 2mm and that the semi-solid temperature range (solid phase ratio 50%) is maintained at the printing interface to achieve metallurgical bonding between adjacent sprayed layers; If a pause is required during the spraying process, the stopper rod 601 is lowered by the electric actuator 602 to close the guide tube, and the platform stops moving at the same time; when resuming the spraying, the stopper rod is first raised and then the platform movement is restarted.

[0023] S4: Post-processing stage After printing is completed, the stopper rod is lowered to close the guide tube, the argon gas input and heating are stopped, and the ring part is removed from the mold after it cools to room temperature; The ring parts are subjected to stress relief annealing (temperature 270℃, holding temperature 1.5h), surface cleaning and dimensional accuracy inspection.

[0024] The controller described in this solution is used to control the electrical devices used in this solution, including but not limited to sensors, motors, telescopic rods, water pumps, solenoid valves, heating wires, heat pumps, display screens, computer input devices, switch buttons, communication equipment, lights, speakers and microphones; the controller is an Intel processor, AMD processor, PLC controller, ARM processor or a single-chip microcomputer, and the supporting components also include a motherboard, a memory stick, a storage medium and a power supply, and the power supply is AC or a lithium battery; when a display screen is provided, a display card is also provided; for the operating principle of the controller, please refer to "Principles of Automatic Control", "Principles and Application Simulation Cases of Microcontrollers" and "Principles and Applications of Sensors" published by Tsinghua University Press, and other books in this field can be used for reference; other automatic control and electrical devices not mentioned are all knowledge well known to those skilled in the art and will not be repeated here.

[0025] In the explanation of the invention, it should be noted that the terms indicating orientation are only for the convenience of description and understanding, and are not the only limitation on the installation position of specific technical features, and do not exclude other possible installation methods.

[0026] The serial numbers assigned to components herein, such as "first," "second," etc., are used solely to distinguish the objects being described and do not convey any sequential or technical meaning. References to "connection" and "coupling" herein, unless otherwise specified, include both direct and indirect connections (couplings). In the description of the present invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like, indicating positions or relationships, are based on those shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention.

[0027] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the invention, rather than to limit it. Although the invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the invention.

Claims

1. An additive manufacturing equipment for continuous injection molding of ring parts using magnesium alloy liquid, characterized in that: include: A crucible melting assembly (20) is arranged in the upper vacuum chamber (10), and a liquid jet printing assembly (40) and a controller are arranged in the lower vacuum chamber (30) and communicated with the crucible melting assembly (20); a three-dimensional motion platform (50) is provided in the lower vacuum chamber (30) and is located below the liquid jet printing assembly (40); and a ring-shaped mold (501) with an open top surface is provided on the top of the three-dimensional motion platform (50); The crucible smelting assembly (20) comprises: a smelting crucible (201), a release mechanism (60) and an annular filter screen cartridge (202); the smelting crucible (201) is arranged in the upper vacuum chamber (10), and the smelting crucible (201) is connected to the liquid jet printing assembly (40) via a guide tube (203); the release mechanism (60) is used to control the opening and closing of the guide tube (203), and the annular filter screen cartridge (202) is used to filter the magnesium liquid entering the guide tube (203); The liquid jet printing assembly (40) comprises: a hollow graphite ring (401) and a nozzle (402); the hollow graphite ring (401) is fixedly connected to the melting crucible (201) via a plurality of evenly distributed flow guide tubes (203); the bottom surface of the hollow graphite ring (401) is provided with a plurality of nozzles (402) distributed in a ring array; and a liquid level detector and a temperature monitor are provided in the melting crucible (201).

2. The additive manufacturing equipment for ring-shaped parts by continuous injection molding of magnesium alloy liquid according to claim 1, characterized in that: The upper vacuum chamber (10) and the lower vacuum chamber (30) are respectively provided with vacuum pumps (70), and the upper vacuum chamber (10) is connected to an inert gas source to provide inert gas protection therein.

3. The additive manufacturing equipment for ring-shaped parts by continuous injection molding of magnesium alloy liquid according to claim 1, characterized in that: A condensation table (502) is provided on the three-dimensional motion platform (50), and a flow channel for circulating cooling liquid is provided in the condensation table (502). Through the mutual cooperation among the liquid jet printing component (40), the three-dimensional motion platform (50), and the condensation table (502), the magnesium liquid can be spread over a large area in the annular mold (501) and can be kept in a semi-solid state at the printing interface, thereby achieving metallurgical bonding of the corresponding printing areas of each nozzle (402).

4. The additive manufacturing equipment for ring-shaped parts by continuous injection molding of magnesium alloy liquid according to claim 1, characterized in that: The release mechanism (60) comprises a stopper rod (601), an electric actuator (602), and a clamp arm. The electric actuator (602) is installed in the smelting crucible (201). The stopper rod (601) and the electric actuator (602) are connected as a whole via the clamp arm. Driven by the electric actuator (602), the stopper rod (601) performs vertical linear motion to control the opening and closing of the flow guide tube (203). The flow rate of the magnesium liquid can be changed by changing the opening degree of the stopper rod and the flow guide tube (203).

5. The additive manufacturing equipment for ring-shaped parts by continuous injection molding of magnesium alloy liquid according to claim 1, characterized in that: The controller comprises: a motion control unit and a general control unit, a pressure closed-loop control module and a speed matching control module, wherein: the motion control unit is connected to the general control unit and transmits motion information of the three-dimensional motion platform (50), and the general control unit is respectively connected to the release mechanism (60) and the vacuum pump and transmits information on the motion of the release mechanism (60) and the opening and closing of the vacuum pump; The pressure closed-loop control module is connected to the argon gas source of the upper vacuum chamber and the liquid level detector signal of the melting crucible (201), and automatically adjusts the argon pressure P1 according to the real-time liquid level height H, so that the total pressure P=P0+P1 satisfies the injection condition of PF>0; The speed matching control module is connected to the driving mechanism of the three-dimensional motion platform (50) and the flow monitoring signal of the nozzle (402), and dynamically adjusts the up and down movement speed of the platform according to the measured injection flow rate to ensure that the spreading thickness of the magnesium liquid in the annular mold (501) matches the solidification rate.

6. The additive manufacturing equipment for ring-shaped parts by continuous injection molding of magnesium alloy liquid according to claim 1, characterized in that: The heating mechanism of the hollow graphite ring (401) and the nozzle (402) comprises a resistance heating element or an induction heating coil, and the preheating temperature range is 300-500° C., so as to ensure that the magnesium liquid maintains liquid fluidity when flowing through and avoid overheating and oxidation.

7. The operating method of the additive manufacturing equipment for continuous injection molding of ring-shaped parts using magnesium alloy liquid according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Preprocessing stage Putting magnesium alloy raw materials into the melting crucible (201), turning on the heating device, heating to 700-800°C for melting under the protection of argon gas introduced into the upper vacuum chamber so that the oxygen content is less than 10 ppm, then performing refining and slag removal, sampling and testing the composition to find that it is qualified, and then cooling to the printing temperature (20-50°C higher than the liquidus temperature); Close the upper vacuum chamber (10) and seal it, then introduce argon gas to a pressure of P1 = 0.05-0.2 MPa (pre-set according to the liquid level H); Start the heating mechanism of the hollow graphite ring (401) and the nozzle (402), preheat to 400±50°C, and simultaneously introduce 20-50°C coolant into the condensation table (502) to establish a cooling cycle; S2: Filling and injection control stage The stopper rod (601) is lifted upward by the electric actuator (602), the guide tube (203) is opened, and the magnesium liquid is filtered through the annular filter cylinder (202) and flows into the hollow graphite ring (401). When the liquid level detector detects that the magnesium liquid in the liquid storage tank reaches 80%-90% of the set volume, the stopper rod is stopped from being lifted, and the opening degree of the guide tube (203) is kept constant; The pressure closed-loop control module monitors the liquid level H of the smelting crucible in real time, automatically adjusts the argon pressure P1, and makes the total pressure P=ρgH+P1 (ρ is the density of the magnesium liquid, g is the acceleration of gravity) satisfy P>F, and drives the magnesium liquid to be ejected from the nozzle (402) at a flow rate of 0.1-1m / s; S3: Ring forming stage The three-dimensional motion platform (50) moves downward at a speed of 0.5-5 mm / s, synchronously receiving the magnesium liquid sprayed by the nozzle, and stacking it layer by layer in the annular mold (501); The speed matching control module calculates the platform movement speed in real time according to the nozzle flow rate, ensuring that the thickness of each layer of magnesium liquid is 1-5mm and that the semi-solid temperature range (solid phase ratio 30%-70%) is maintained at the printing interface to achieve metallurgical bonding of adjacent sprayed layers; If a pause is required during the spraying process, the stopper rod (601) is lowered by the electric actuator (602) to close the guide tube, and the platform stops moving at the same time; when resuming the spraying, the stopper rod is first raised and then the platform movement is restarted; S4: Post-processing stage After printing is completed, the stopper rod is lowered to close the guide tube, the argon gas input and heating are stopped, and the ring part is removed from the mold after it cools to room temperature; The ring parts are subjected to stress relief annealing (temperature 200-350℃, insulation 1-2h), surface cleaning and dimensional accuracy inspection, and are put into storage after passing the inspection.

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