Liquid metal continuous liquid surface selective solidification additive manufacturing apparatus and method

Abstract

The application provides a liquid metal continuous liquid surface selective solidification additive manufacturing device and method, the device comprises an upper tank and a lower tank, the lower tank is used for heating a metal raw material to form a liquid metal, and the upper tank comprises: a forming chamber located in the interior of the upper tank, the forming chamber is connected with a pressure control device; the liquid metal is sucked into the forming chamber from the lower tank by applying negative pressure to the upper tank; a plurality of temperature control modules are located outside the forming chamber and arranged in a plane at the bottom of the forming chamber, and a temperature control device controls the temperature control modules to form different temperature states at different positions of the forming chamber; a driving device is located at the side of the forming chamber; a water-cooled substrate is connected with the driving device through a pulling platform, and the driving device drives the water-cooled substrate to immerse in the liquid metal or lift upward from the liquid metal. The application can realize directional and rapid selective solidification of the metal liquid, form complete liquid metal continuous liquid surface additive manufacturing, and realize shape control and property control of the forming part in the whole process.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and more specifically, to an additive manufacturing apparatus and method for selective solidification of liquid metal on a continuous liquid surface. Background Technology

[0002] Lightweight technology, as a crucial means to improve aircraft performance, reduce energy consumption, and increase payload, is a perennial theme in the aerospace field. Achieving material lightweighting facilitates safer and more efficient flight missions. Data shows that a 1% reduction in aircraft weight can improve performance by 3% to 5%, and weight reduction contributes to improved fuel efficiency and payload capacity. The use of materials such as titanium alloys, aluminum alloys, and magnesium alloys can achieve lightweight transformation in industries like aerospace. In terms of processing methods, traditional manufacturing methods have already maximized the potential for weight reduction in parts. Based on the characteristics of additive manufacturing technology—the ability to create free-form laminates—new technological approaches can be provided for the lightweight design and manufacturing of high-performance aerospace components. However, current metal additive manufacturing processes often require the use of high-energy-density heat sources such as lasers, electron beams, or electric arcs to simultaneously melt the raw metal material and the base metal within a relatively small area. Furthermore, the raw metal material must be pre-formed into wires or powders of specific shapes and sizes. This results in problems such as poor applicability to equipment and raw materials, high costs, low forming efficiency, significant height-direction step effects, poor mechanical properties, severe heat accumulation and high residual stress, and strong anisotropy in the microstructure and mechanical properties of the components. Therefore, research into novel, high-efficiency metal additive manufacturing processes is of great significance and economic value for the lightweight manufacturing of aerospace components.

[0003] For decades, the industry has not found a molding process solution that completely solves the above problems. An article published in the March 2015 issue of *Science* proposed a method utilizing the oxygen inhibition effect of photosensitive resins, such as... Figure 1 As shown, a non-curing liquid resin layer (dead zone, also known as a curing inhibition zone) is formed above a semi-permeable membrane that is highly transparent to UV light and oxygen. This allows for resin renewal without the need for delamination, enabling the continuous forming of three-dimensional objects—a technology called Continuous Liquid Interface Production (CLIP). The CLIP process is as follows: Figure 1As shown, this process allows for very thin layers in the cured slabs, enabling continuous printing of parts. It increases the bonding strength between layers, reduces anisotropy and stair-step effects caused by layer thickness, and improves the surface quality and performance of the parts. The forming efficiency of this process is 10 to 100 times that of traditional photopolymerization methods, and it perfectly solves problems such as anisotropy in the mechanical properties of printed parts. It can be considered a revolutionary achievement in the field of photopolymerization 3D printing.

[0004] High-efficiency lightweight manufacturing is an important application of metal additive manufacturing technology in the aerospace field. Current research mainly focuses on improving the efficiency of SLM and LMD processes, such as multi-laser beam parallel printing, area printing, and multi-filament feeding. To date, the main material for CLIP technology has been photosensitive resin, but research on CLIP processes for metallic materials has not been reported. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a liquid metal continuous liquid surface selective solidification additive manufacturing equipment and method.

[0006] According to one aspect of the present invention, a liquid metal continuous liquid surface selective solidification additive manufacturing apparatus is provided, comprising an upper tank and a lower tank, wherein the lower tank is used to heat metal raw materials to form liquid metal, and the upper tank comprises:

[0007] A forming chamber is located inside the upper tank and is connected to a pressure control device; by applying negative pressure to the upper tank, the liquid metal is drawn from the lower tank into the forming chamber.

[0008] Multiple temperature control modules are located outside the forming chamber and arranged in a plane at the bottom of the forming chamber. The multiple temperature control modules are connected to a temperature control device, which controls the multiple temperature control modules to form different temperature states at different positions in the forming chamber.

[0009] The drive unit is located on the side of the forming chamber;

[0010] A water-cooled substrate is located above the forming chamber;

[0011] A drawing platform is located above the water-cooled substrate; the water-cooled substrate is connected to the driving device through the drawing platform, and the driving device drives the water-cooled substrate and the drawing platform to move in the vertical direction, and the driving device drives the water-cooled substrate to be immersed in the liquid metal or lifted upward from the liquid metal.

[0012] Furthermore, both the forming chamber and the drawing platform are made of high-temperature resistant materials.

[0013] Furthermore, the drawing platform and the water-cooled substrate are horizontally arranged on the side near the forming chamber.

[0014] Furthermore, the driving device includes a linear module, which includes a servo motor and a ball screw. The output end of the servo motor is connected to one end of the ball screw, and the other end of the ball screw is connected to the drawing platform.

[0015] Furthermore, the temperature control device controls multiple temperature control modules to absorb or release heat, changing the heat distribution within the forming chamber and altering the solidification position of the liquid metal.

[0016] Furthermore, the lower tank is connected to the pressure control device, which is also used to regulate the pressure inside the lower tank.

[0017] Furthermore, the lower tank is equipped with a heating device for heating metal raw materials, and the heating device uses a coil.

[0018] Furthermore, the lower tank is connected to the forming chamber via an infusion pipe.

[0019] Furthermore, the device also includes a monitoring and sampling system for monitoring the state of the molded part during the molding process.

[0020] According to another aspect of the present invention, a method for selective solidification additive manufacturing of liquid metal on a continuous liquid surface is provided, which is implemented using the above-described selective solidification additive manufacturing equipment for liquid metal on a continuous liquid surface, the method comprising:

[0021] The metal raw material is placed into the lower tank, which heats the metal raw material to melt it into liquid metal;

[0022] A negative pressure is applied to the upper tank, causing the liquid metal to be stably drawn into the forming chamber from the lower tank;

[0023] The drive unit drives the pulling platform and the water-cooled substrate to descend, immersing the water-cooled substrate into the liquid metal.

[0024] The temperature control device controls the temperature control module corresponding to the forming layer to absorb heat according to the projection of each layer on the forming plane, and performs directional and rapid solidification of the liquid metal above the selected temperature control module to form metal part layers.

[0025] The drive unit drives the drawing platform and water-cooled substrate to rise, and drives the metal parts to rise. The temperature control unit controls the heat release of the remaining temperature control modules, and by adjusting the pressure and the lifting speed of the water-cooled substrate, the liquid metal enters the narrow channel for rapid filling.

[0026] The temperature control device controls the temperature control module to absorb or release heat, thereby changing the heat distribution in the forming chamber and the solidification position of the liquid metal. According to the shape of the part to be additively manufactured, the temperature control module is controlled to absorb or release heat accordingly, raising the drawing platform and water-cooled substrate, so that the solidified metal layers fuse together to achieve additive manufacturing.

[0027] The pressure and temperature inside the upper tank are controlled, and after in-situ hot isostatic pressing, a shaped part with a preset shape and properties is obtained.

[0028] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0029] This invention utilizes a temperature control device and multiple temperature control modules to establish different temperature states at different locations within the forming chamber. A drive device moves a water-cooled substrate vertically. Through the coordinated operation of the temperature control modules and the water-cooled substrate, directional, rapid, and selective solidification of molten metal can be achieved, resulting in complete liquid metal continuous surface additive manufacturing. The process is smooth, without any stair-step effect, thus ensuring product quality. Furthermore, the additive manufacturing speed is high, the quality of the additive parts is stable, robust, and less prone to sputtering. After forming, the shape and properties of the formed parts can be controlled throughout the entire process by pressurizing the forming chamber and performing post-processing methods such as in-situ hot isostatic pressing. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 The diagram shows a continuous liquid surface manufacturing process in the prior art, where: (a) is a schematic diagram of the principle, and (b) is a schematic diagram of the device;

[0032] Figure 2 This is a schematic diagram of the structure of a liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to an embodiment of the present invention. Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0034] The main reasons why the CLIP process for metal materials failed to be implemented are as follows: 1. Metal materials are opaque, unlike photosensitive resin materials, which can be precisely selected for additive manufacturing using a UV beam; 2. Metal materials have higher melting points, requiring more sophisticated equipment; 3. Liquid metal is difficult to fill quickly in narrow gaps without external force, making it impossible to control the thickness of the curing inhibition zone, thus leading to molding failure; 4. Because liquid metal cannot fill narrow gaps quickly without external force, a large local negative pressure is generated between the cured layer and the substrate, making it impossible to peel the part off, resulting in molding failure; 5. Due to the high specific strength and high elastic modulus of metal materials, large internal stresses are easily generated during the molding process, leading to deformation and cracking of the part.

[0035] To address the aforementioned problems in the prior art and realize the CLIP process for metallic materials, one embodiment of the present invention provides a liquid metal continuous liquid surface selective solidification additive manufacturing apparatus, referring to... Figure 2 The equipment includes an upper tank and a lower tank. The lower tank is used to heat the metal raw material to form liquid metal. The upper tank includes a forming chamber, multiple temperature control modules, a drive device, a water-cooled substrate, and a drawing platform. The forming chamber is located inside the upper tank and is connected to a pressure control device, which is used to regulate the internal pressure of the upper tank. By applying negative pressure to the upper tank, the liquid metal is drawn into the forming chamber from the lower tank. Multiple temperature control modules are located outside the forming chamber and are arranged in a plane at the bottom of the forming chamber. The multiple temperature control modules are connected to a temperature control device, which controls the multiple temperature control modules to form different temperature states at different positions in the forming chamber. The drive device is located on the side of the forming chamber. The water-cooled substrate is located above the forming chamber. The drawing platform is located above the water-cooled substrate. The water-cooled substrate is connected to the drive device through the drawing platform. The drive device drives the water-cooled substrate and the drawing platform to move in the vertical direction. The drive device moves the water-cooled substrate into the liquid metal or lifts it upward from the liquid metal to achieve forming in the height direction.

[0036] In this embodiment of the invention, the form of the metal raw material is not specifically limited, as long as the desired liquid metal can be obtained. Preferably, metal ingots are used as raw materials, which has a lower cost and helps to reduce manufacturing costs.

[0037] During the forming process, the drawing platform is slightly immersed in the molten metal. In order to enable the equipment to be suitable for additive manufacturing of metal parts with different melting points, especially high-melting-point metal parts, in some embodiments, both the forming chamber and the drawing platform are made of high-temperature resistant materials. For example, they are made of corundum-mullite riser material to achieve good heat insulation.

[0038] In some implementations, the drawing platform and the water-cooled substrate are horizontally positioned near the side of the forming chamber to ensure correct forming position.

[0039] In some embodiments, the drive unit includes a linear module, which is vertically disposed on the side of the liquid metal pool in the forming chamber. The linear module includes a servo motor and a ball screw. The output end of the servo motor is connected to one end of the ball screw, and the other end of the ball screw is connected to the drawing platform.

[0040] Multiple temperature control modules are installed below the forming chamber, each of which can be controlled independently to precisely regulate the temperature rise or fall. In some embodiments, the temperature control device controls multiple temperature control modules to absorb or release heat, changing the heat distribution inside the forming chamber and thus altering the solidification position of the liquid metal.

[0041] In some embodiments, the lower tank is connected to a pressure control device, which is also used to regulate the internal pressure of the lower tank. The pressures inside the forming chamber and the lower tank can be adjusted independently to better control the flow state of the liquid metal.

[0042] In order to heat the metal raw material to form a liquid metal, in some embodiments, a heating device for heating the metal raw material is provided inside the lower tank. The heating device adopts a coil, which has a simple structure, is easy to arrange, and has a good heating effect.

[0043] To facilitate the transfer of liquid metal from the lower tank to the forming chamber in the upper tank, in some embodiments, the lower tank is connected to the forming chamber via a delivery pipe. For example, the lower tank has two delivery pipes connected to the forming chamber, and by applying negative pressure to the upper tank, the liquid metal is smoothly and steadily drawn into the forming chamber.

[0044] The equipment in the above embodiments also includes a monitoring and sampling system, which is used to monitor the state of the molded part during the molding process. Specifically, the monitoring and sampling system includes a synchrotron radiation meter, a pressure sensor, a water and oxygen concentration sensor, and a temperature sensor. The synchrotron radiation meter enables in-situ observation of the solidification molding process, the pressure sensor enables pressure regulation control, the water and oxygen concentration sensor controls the vacuum level, and the temperature sensor monitors the temperature changes of multiple temperature control modules, thereby achieving temperature regulation during the molding process.

[0045] Due to thermal effects, a solidification inhibition zone forms in the narrow area between the bottom of the forming chamber and the formed part. This invention, based on the principle of Continuous Liquid Surface Manufacturing (CLIP) technology and combined with anti-gravity pressure-regulating casting technology, can precisely control the temperature and flow fields of the liquid metal. Multiple temperature control modules, temperature control devices, and a water-cooled substrate are used to precisely select and solidify the materials involved in additive manufacturing within each layer. During the forming process, pressure and temperature are controlled, combined with an appropriate lifting speed along the height direction, to effectively fill the liquid metal material and control the thickness and adhesion of the solidification inhibition zone, ensuring the possibility of high-efficiency and high-precision forming. After the negative pressure feeding and pressurization forming stages, the formed part undergoes in-situ hot isostatic pressing and other post-treatment methods during the pressure holding stage, achieving full-process forming defect suppression and internal stress control. The entire process is not limited by the form of powder, filament, or sheet materials similar to existing metal additive manufacturing raw materials. It is low-cost, has a short process flow, high efficiency, and significantly reduced step effects. Furthermore, since there is no high-energy beam involved in the forming process, thermal stress is reduced, greatly reducing the risk of part deformation and cracking. By combining synchrotron radiation in-situ detection methods with solidification control and in-situ post-processing methods, defect suppression and internal stress regulation can be effectively carried out throughout the entire process, thus realizing the CLIP process for metallic materials.

[0046] Another embodiment of the present invention provides a method for selective solidification additive manufacturing of liquid metal on a continuous liquid surface, which is implemented using the above-mentioned selective solidification additive manufacturing equipment for liquid metal on a continuous liquid surface. The method includes:

[0047] S1. Place the metal raw material into the lower tank, and heat the metal raw material in the lower tank to melt it into liquid metal;

[0048] S2. Apply negative pressure to the upper tank to stably draw liquid metal from the lower tank into the forming chamber and keep the temperature of the liquid metal (molten metal) above its melting point.

[0049] S3. The driving device drives the pulling platform and the water-cooled substrate to descend, slightly immersing the water-cooled substrate into the liquid metal. The lower surface of the water-cooled substrate is lower than the liquid plane of the liquid metal, and the metal is melted by a heating device such as an induction coil, keeping the temperature of the liquid metal above the melting point.

[0050] S4. During the forming process, multiple layers are arranged along the height direction. The temperature control device controls the temperature control module corresponding to the forming layer to absorb heat according to the projection of each layer on the forming plane (horizontal plane), and performs directional and rapid solidification of the liquid metal above the selected temperature control module to form metal part layers.

[0051] S5. The drive device drives the drawing platform and the water-cooled substrate to slowly lift upwards, and the drawing platform drives the solidified additive forming part, i.e., the metal part sheet, to lift. The temperature control device controls the heat release of the other temperature control modules, and by adjusting the pressure and the lifting speed of the water-cooled substrate, the liquid metal enters the narrow channel between the bottom of the forming chamber and the formed part in a stable and efficient manner for filling.

[0052] S6. The temperature control device controls the temperature control module to absorb or release heat, thereby changing the heat distribution in the forming chamber and the solidification position of the liquid metal. According to the shape of the part to be additively manufactured, the temperature control module is controlled to absorb or release heat accordingly, and the drawing platform and water-cooled substrate are slowly raised so that the solidified metal is fused layer by layer in the height direction to achieve additive manufacturing.

[0053] S7. The pressure and temperature inside the upper tank are controlled and maintained for a certain period of time. After in-situ hot isostatic pressing, a formed part with a preset shape and properties is obtained, thus realizing the shape and properties control of the formed part.

[0054] In this embodiment of the invention, the temperature range formed by the heat absorbed or released by the temperature control module is approximately 0 to 100 degrees Celsius, forming a controllable high temperature distribution.

[0055] The manufacturing method of selective solidification additive manufacturing of liquid metal continuous liquid surface based on pressure regulation in the embodiments of the present invention can form a completely continuous additive manufacturing process. The process is smooth, does not produce a step effect, ensures product quality, and is highly efficient. The additive parts have stable quality and strong robustness.

[0056] In the above embodiments of the present invention, different temperature states are established at different locations in the forming chamber through a temperature control device and multiple temperature control modules. A driving device moves the water-cooled substrate vertically. Through the cooperation between the temperature control modules and the water-cooled substrate, directional, rapid, and selective solidification of the molten metal can be achieved, forming a completely continuous liquid metal additive manufacturing process. The process is smooth, without any step effects, thus ensuring product quality. Furthermore, the additive manufacturing speed is fast, the quality of the additive parts is stable, robust, and less prone to sputtering. After forming, the shape and properties of the formed parts can be controlled throughout the entire process by pressurizing the inside of the forming chamber and performing post-processing methods such as in-situ hot isostatic pressing.

[0057] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. The above preferred features can be used in any combination without conflict.

Claims

1. A liquid metal continuous liquid surface selective solidification additive manufacturing device, characterized in that, It includes an upper tank and a lower tank, wherein the lower tank is used to heat metal raw materials to form liquid metal, and the upper tank includes: A forming chamber is located inside the upper tank and is connected to a pressure control device; by applying negative pressure to the upper tank, the liquid metal is drawn from the lower tank into the forming chamber. Multiple temperature control modules are located outside the forming chamber and arranged in a plane at the bottom of the forming chamber. The multiple temperature control modules are connected to a temperature control device, which controls the multiple temperature control modules to form different temperature states at different positions in the forming chamber. The drive unit is located on the side of the forming chamber; A water-cooled substrate is located above the forming chamber; A drawing platform is located above the water-cooled substrate; the water-cooled substrate is connected to the driving device through the drawing platform, and the driving device drives the water-cooled substrate and the drawing platform to move in the vertical direction, and the driving device drives the water-cooled substrate to be immersed in the liquid metal or lifted upward from the liquid metal.

2. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, Both the forming chamber and the drawing platform are made of high-temperature resistant materials.

3. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, The drawing platform and the water-cooled substrate are horizontally arranged on the side near the forming chamber.

4. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, The drive device includes a linear module, which includes a servo motor and a ball screw. The output end of the servo motor is connected to one end of the ball screw, and the other end of the ball screw is connected to the drawing platform.

5. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, The temperature control device controls multiple temperature control modules to absorb or release heat, changing the heat distribution in the forming chamber and thus altering the solidification position of the liquid metal.

6. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, The lower tank is connected to the pressure control device, which is also used to regulate the pressure inside the lower tank.

7. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, The lower tank is equipped with a heating device for heating metal raw materials, and the heating device uses a coil.

8. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, The lower tank is connected to the forming chamber via an infusion pipe.

9. The liquid metal continuous liquid surface selective solidification additive manufacturing equipment according to claim 1, characterized in that, It also includes a monitoring and sampling system, which is used to monitor the state of the formed part during the forming process.

10. A method for selective solidification additive manufacturing of liquid metal on a continuous liquid surface, implemented using the selective solidification additive manufacturing equipment for liquid metal on a continuous liquid surface as described in any one of claims 1-9, characterized in that... include: The metal raw material is placed into the lower tank, which heats the metal raw material to melt it into liquid metal; A negative pressure is applied to the upper tank, causing the liquid metal to be stably drawn into the forming chamber from the lower tank; The drive unit drives the pulling platform and the water-cooled substrate to descend, immersing the water-cooled substrate into the liquid metal. The temperature control device controls the temperature control module corresponding to the forming layer to absorb heat according to the projection of each layer on the forming plane, and performs directional and rapid solidification of the liquid metal above the selected temperature control module to form metal part layers. The drive unit drives the drawing platform and water-cooled substrate to rise, and drives the metal parts to rise. The temperature control unit controls the heat release of the remaining temperature control modules, and by adjusting the pressure and the lifting speed of the water-cooled substrate, the liquid metal enters the narrow channel for filling. The temperature control device controls the temperature control module to absorb or release heat, thereby changing the heat distribution in the forming chamber and the solidification position of the liquid metal. According to the shape of the part to be additively manufactured, the temperature control module is controlled to absorb or release heat accordingly, raising the drawing platform and water-cooled substrate, so that the solidified metal layers fuse together to achieve additive manufacturing. The pressure and temperature inside the upper tank are controlled, and after in-situ hot isostatic pressing, a shaped part with a preset shape and properties is obtained.

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