Laser directional energy deposition system for voxel-level metal multi-material preparation

Abstract

The invention belongs to the technical field of additive manufacturing equipment, and relates to a laser directional energy deposition system for voxel-level metal multi-material preparation, which comprises a powder feeding device and a controller, and the powder feeding device is electrically connected with the controller. The powder feeding device comprises a plurality of powder feeding tanks, a plurality of flow control switches, a powder mixing tank and a powder feeding nozzle. Discharging ports of the multiple powder feeding tanks are all communicated with the powder mixing tank, and a discharging port of the powder mixing tank is communicated with the powder feeding nozzle. And a flow control switch is arranged in each powder feeding tank. And the controller is configured to control the opening degree of each flow control switch in real time according to the real-time preset proportion of each metal powder so as to control the powder feeding flow of the metal powder flowing to the powder mixing tank in each powder feeding tank. According to the laser directional energy deposition system for preparing the voxel-level metal multi-material, the component proportion of the metal multi-material can be randomly changed in a three-dimensional space.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing equipment technology, and relates to a laser-directed energy deposition system for voxel-level metal multimaterial preparation. Background Technology

[0002] Multimaterial metallic structures are novel structural-functional materials in which metallic materials are continuously or discretely distributed in space, possessing enormous application potential in aerospace, nuclear industry, automotive, and medical devices. Traditional machining methods for fabricating multimaterial metallic structures suffer from complex processes, low geometric complexity, and long development cycles. Additive manufacturing technology employs a "discrete-stacking" deposition method, achieving near-net-shape construction of components through a layer-by-layer deposition process, providing new insights for the design and fabrication of multimaterial metallic structures. Laser-directed energy deposition (LDED) technology is a crucial component of additive manufacturing. It utilizes a high-energy laser beam to melt synchronously transported metal powder and deposit it layer-by-layer onto a substrate or existing component, directly creating dense metallic entities or repairing and strengthening parts. Due to its excellent multimaterial manufacturing capabilities, high material utilization rate, and unique advantages in manufacturing large components, LDED technology has gained widespread application in industrial fields.

[0003] Existing laser-directed energy deposition systems mainly consist of a laser and a powder feeding device. The powder feeding device includes a powder feeding nozzle and a powder feeder. The powder feeder stores pre-mixed metal powder for output through the powder feeding nozzle. During operation, the powder feeding nozzle moves synchronously with the laser and transports the powder. The moving laser synchronously melts the transported metal powder to form a moving molten pool. The tail of the molten pool rapidly solidifies to generate a single trajectory. Multiple trajectories overlap and fuse according to a planned path to form a dense deposition layer. Finally, through precise layer-by-layer stacking and interlayer remelting, a multi-material metal structure is fabricated.

[0004] However, in existing laser-directed energy deposition systems, the metal powders corresponding to each deposition layer are pre-mixed by a powder feeder, resulting in each deposition layer consisting of a fixed proportion of metal powders. The powder feeder can only adjust the proportions of the metal powders before a new deposition layer is formed, thus allowing for a gradient change in metal powder composition only between different deposition layers along the deposition direction. This results in the fabricated product achieving only a "pseudo" multimaterial structure in a two-dimensional space along the deposition direction, rather than a "true" multimaterial structure with arbitrarily variable composition in three-dimensional space, limiting the application potential of additive manufacturing of multimaterial metal structures. Therefore, there is an urgent need to develop a laser-directed energy deposition system that allows for arbitrarily variable composition ratios of multimaterial metals in three-dimensional space. Summary of the Invention

[0005] The purpose of this invention is to provide a laser-directed energy deposition system for voxel-level multi-material metal fabrication, in order to solve the technical problem that existing laser-directed energy deposition systems cannot achieve arbitrary variable ratios of multi-material components in three-dimensional space.

[0006] To achieve the above objectives, the present invention provides a specific technical solution for a laser-directed energy deposition system for voxel-level metal multimaterial fabrication as follows: A laser-directed energy deposition system for voxel-scale multi-material metal fabrication includes a powder feeding device and a controller, wherein the powder feeding device and the controller are electrically connected; the powder feeding device includes multiple powder feeding tanks, multiple flow control switches, a powder mixing tank, and a powder feeding nozzle; the outlets of the multiple powder feeding tanks are all connected to the powder mixing tank, and the outlets of the powder mixing tanks are connected to the powder feeding nozzles; each powder feeding tank is equipped with a flow control switch; the controller is configured to: control the opening degree of each flow control switch in real time according to a preset ratio of each metal powder, so as to control the powder feeding flow rate of metal powder in each powder feeding tank to the powder mixing tank.

[0007] Furthermore, the powder feeding device also includes multiple flow detection elements, each of which is located in the corresponding powder feeding tank and is used to detect the powder feeding flow in real time; the controller is also configured to adjust the opening degree of each flow control switch in real time according to the powder feeding flow detected in real time by each flow detection element and the corresponding preset ratio.

[0008] Furthermore, the flow control switch includes a piston switch and a first drive motor. The size of the piston switch matches the cross-sectional size of the inner wall of the powder feeding tank. The piston switch is rotatably disposed inside the powder feeding tank about the radial direction of the powder feeding tank, and the output end of the first drive motor is connected to the piston switch.

[0009] Furthermore, the flow control switch includes a screw and a second drive motor. The screw is coaxially arranged with the powder feeding tank, and the diameter of the screw matches the cross-sectional dimensions of the inner wall of the powder feeding tank. The output end of the second drive motor is connected to the screw.

[0010] Furthermore, the flow detection element is a ring charge sensor, a high-speed camera, an optical occlusion sensor, or an optical scattering sensor.

[0011] Furthermore, the powder feeding device also includes multiple powder storage tanks and multiple pre-storage tanks, with each powder storage tank connected in sequence to the corresponding pre-storage tank and the corresponding powder feeding tank.

[0012] Furthermore, the powder feeding device also includes a Venturi mixer, the inlet of which is connected to the outlet of the plurality of powder feeding tanks, and the outlet of which is connected to the inlet of the powder mixing tank.

[0013] Furthermore, the mixing tank includes a buffer chamber, a pressure stabilizing chamber, and a venturi tube; the buffer chamber and the pressure stabilizing chamber are sealed together, and the venturi tube is located inside the buffer chamber and the pressure stabilizing chamber, at the connection point between them. The inlet end of the venturi tube communicates with the buffer chamber, and the outlet end of the venturi tube communicates with the pressure stabilizing chamber; the buffer chamber is connected to the outlet of the venturi mixer; at least one tangential air inlet is provided on the side wall of the buffer chamber for connecting high-pressure inert gas; a stirring mechanism is provided inside the pressure stabilizing chamber, and a vibration mechanism is provided on the outer wall of the pressure stabilizing chamber.

[0014] Furthermore, the stirring mechanism includes a vertically arranged rotating shaft, a stirring paddle disposed on the outer wall of the rotating shaft, and a driving element for driving the rotating shaft to rotate; the distance between the stirring paddle and the inner wall of the pressure stabilizing chamber is 2mm to 5mm, and the rotational speed of the stirring paddle is 15 rpm to 20 rpm.

[0015] Furthermore, the laser-directed energy deposition system for voxel-level metal multimaterial fabrication also includes a gas delivery element and a dust removal element; the gas delivery element is used to deliver inert protective gas to the powder feeding tank; the dust removal element is used to remove dust and flue gas from the deposition layer.

[0016] The laser-directed energy deposition system for voxel-level metal multimaterial fabrication of the present invention has the following advantages: In operation, the laser-directed energy deposition system of this invention controls the opening of the flow control switch in each powder feeding tank in real time according to the preset ratio of each metal powder, thereby controlling the powder flow rate of the metal powder from each powder feeding tank to the mixing tank. The metal powder conveyed by each powder feeding tank enters the mixing tank for mixing. The mixed metal powder is then sprayed onto the substrate through the powder feeding nozzle. As the powder feeding nozzle moves synchronously with the laser device, the moving laser synchronously melts the conveyed metal powder to form a moving molten pool. The tail of the molten pool quickly solidifies to form a single trajectory. Multiple trajectories overlap and fuse according to the planned path to form a dense deposition layer. Finally, through precise layer-by-layer superposition and interlayer remelting, the metal powder ratio changes in real time, thereby enabling arbitrary variation of the multi-material composition of metals in three-dimensional space. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the powder feeding device of the present invention; Figure 2 This is a schematic diagram of the flow control switch, powder feeding tank, and controller of the present invention; Figure 3 This is a schematic diagram of the piston switch and powder feeding tank of the present invention; Figure 4 This is a control flowchart of the powder feeding process of the present invention.

[0018] Figure label: 1. Powder storage tank; 2. Pre-storage tank; 3. Piston switch; 4. First drive motor; 5. Flow detection element; 6. Controller; 7. Powder feeding tank; 8. Powder feeding tank outlet. Detailed Implementation

[0019] The technical solutions of this application will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of this application, unless otherwise stated, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features.

[0020] like Figures 1 to 4 As shown, this invention provides a laser-directed energy deposition system for voxel-scale multi-material metal fabrication, comprising a laser device, a powder feeding device, and a controller 6, wherein the powder feeding device and the controller 6 are electrically connected. The powder feeding device includes multiple powder feeding tanks 7, multiple flow control switches, a mixing tank, and powder feeding nozzles. The outlets of the multiple powder feeding tanks 7 are all connected to the mixing tank, and the outlets of the mixing tank are connected to the powder feeding nozzles. The outlets of the powder feeding tanks 7 are also known as the powder feeding tank outlets 8. Each powder feeding tank 7 contains a flow control switch. The controller 6 is configured to control the opening degree of each flow control switch in real time according to a preset ratio of each metal powder, thereby controlling the powder flow rate of metal powder from each powder feeding tank 7 to the mixing tank. The mixing tank receives metal powder from the multiple powder feeding tanks 7, mixes the various metal powders, and outputs the mixture through the powder feeding nozzles.

[0021] In the laser-directed energy deposition system for voxel-level multi-material metal fabrication according to this invention, during operation, the controller 6 controls the opening of the flow control switch in each powder feeding tank 7 in real time according to the preset ratio of each metal powder, thereby controlling the powder flow rate of the metal powder from each powder feeding tank 7 to the mixing tank. The metal powder conveyed by each powder feeding tank 7 enters the mixing tank for mixing, and the mixed metal powder is sprayed onto the substrate through the powder feeding nozzle. As the powder feeding nozzle moves synchronously with the laser device, the moving laser synchronously melts the conveyed metal powder to form a moving molten pool. The tail of the molten pool solidifies rapidly to generate a single trajectory, and multiple trajectories overlap and fuse according to the planned path to form a dense deposition layer. Finally, through precise layer-by-layer superposition and interlayer remelting, the metal powder ratio changes in real time, thereby realizing arbitrary variation of the multi-material metal composition in three-dimensional space.

[0022] In some embodiments of the present invention, the powder feeding process is illustrated using two powder feeding tanks 7 as an example: when the controller 6 controls the opening of one flow control switch to slowly decrease, so as to reduce the powder feeding flow of the corresponding powder feeding tank 7, at the same time it controls the opening of the other flow control switch to slowly increase, so as to increase the powder feeding flow of the corresponding powder feeding tank 7. Through this coordinated operation, the powder ratio in the mixing tank can be mixed at any time according to the requirements of gradient change.

[0023] However, there is a time delay in the delivery of metal powder to the powder delivery tank 7, causing a mismatch in the composition path obtained according to the preset proportion of metal powder with the composition path obtained from actual deposition in space and time. Specifically, because the metal powder requires a certain amount of time to reach the powder delivery tank 7, the powder delivery flow rate obtained by controlling the flow control switch deviates from the powder delivery flow rate obtained according to the preset proportion. This deviation is particularly noticeable when preparing complex multi-material structures with extremely high requirements for compositional accuracy, which can seriously affect the quality and performance of components, causing the prepared components to fail to meet design requirements, increasing the product defect rate, and raising production costs.

[0024] Therefore, based on the above embodiments, in the embodiments of the present invention, as follows: Figure 1 and Figure 4 As shown, the powder feeding device also includes multiple flow detection elements 5, each of which is located in a corresponding powder feeding tank 7 and is used to detect the powder feeding flow rate in real time. The controller 6 is also configured to adjust the opening degree of each flow control switch in real time according to the powder feeding flow rate detected in real time by each flow detection element 5 and the corresponding preset ratio.

[0025] In this embodiment, a real-time flow perception and closed-loop control mechanism is constructed by setting the flow detection element 5, which has dynamic response capability and flow adaptive adjustment function. Flow detection, signal processing, logical judgment and execution are integrated into the same powder feeding tank 7, forming an integrated "perception-decision-execution" control chain. This enables millisecond-level response and precise correction to the instantaneous powder flow state without relying on external manual intervention, thereby solving the problem that the actual composition deposited on the component deviates from the preset proportion due to the delay in the metal powder being transported to the powder feeding tank 7.

[0026] In some embodiments of the present invention, such as Figures 1 to 3 As shown, the flow control switch includes a piston switch 3 and a first drive motor 4. The size of the piston switch 3 matches the cross-sectional size of the inner wall of the powder feeding tank 7. The piston switch 3 is radially rotatable inside the powder feeding tank 7, and the output end of the first drive motor 4 is connected to the piston switch 3.

[0027] In this embodiment, the first drive motor 4 rotates under the control of the controller 6, driving the piston switch 3 connected to it to rotate synchronously, thereby controlling the size of the piston switch 3 relative to the inner wall of the powder feeding tank 7, i.e., the opening size, and adjusting the powder feeding flow rate. The first drive motor 4 is a stepper motor. As the core actuator driving the piston switch 3 in the flow control switch, the stepper motor's core function is to convert digital control signals into precise and repeatable angular displacement outputs, thereby achieving discrete and high-resolution control of the powder feeding channel opening. Each time the stepper motor receives an electrical pulse, it generates a fixed-angle stepping motion. By sending a pulse sequence and direction signal to its driver through the controller 6, the starting position, rotation angle, rotation speed, and acceleration / deceleration curve of the piston switch 3 can be precisely set. In this embodiment, the output shaft of the stepper motor is rigidly connected to the horizontal rotating shaft of the piston switch 3 through a coupling, ensuring power transmission without slippage or accumulated errors. Its installation orientation fixes the first drive motor 4 to the outer wall of the powder feeding tank 7, while the output end penetrates into the powder feeding tank 7 along the horizontal axis, directly driving the piston switch 3 to swing in a pitching motion around this axis. This structure avoids the thermal impact of the high-temperature powder environment on the first drive motor 4, while ensuring the mechanical rigidity and dynamic tracking of the rotation response.

[0028] In some embodiments of the present invention, such as Figures 1 to 3 As shown, the powder feeding tank 7 is a vertically arranged cylinder, and the piston switch 3 is in the shape of a circular plate.

[0029] In this embodiment, the powder feeding tank 7 adopts a cylindrical structure, that is, its cross-section is a standard circle and its axial direction is a straight cylindrical geometry. The inner wall of the powder feeding tank 7 is a continuous and smooth cylindrical surface, which provides a uniform radial constraint space for the stable falling of metal powder under the combined action of gravity and airflow. The cylindrical design makes the powder feeding channel axisymmetric, which is conducive to the uniform distribution of the powder flow field in the circumferential direction and reduces powder hanging, flow deviation or local accumulation caused by irregular wall surface. The powder feeding tank 7 can be made of 304 stainless steel, 316L stainless steel or hard aluminum alloy, and is manufactured by turning, spinning or cold drawing processes. The inner surface is polished to prevent metal powder adhesion, and a wear-resistant coating can also be applied to its inner surface to extend its service life.

[0030] The piston switch 3 is a rigid circular thin plate that precisely matches the inner diameter of the powder feeding tank 7. Its outer edge contour is a precision-machined arc surface, forming a micro-gap fit with the inner wall of the powder feeding tank 7. This gap ensures the smooth rotation of the piston switch 3 around the horizontal axis and prevents uncontrolled powder leakage from between the plate edge and the tank wall. The piston switch 3 can be made of high-hardness, low-density materials, such as silicon nitride, titanium alloy, or 45# steel with surface carburization treatment, with a thickness of 2mm to 5mm. It has a through hole in the center for mounting the rotating shaft and is fixed to the output shaft of the first drive motor 4 by a key connection or interference fit.

[0031] In some embodiments of the present invention, the flow control switch includes a screw and a second drive motor. The screw is coaxially arranged with the powder feeding tank 7, and the diameter of the screw matches the cross-sectional dimensions of the inner wall of the powder feeding tank 7. The output end of the second drive motor is connected to the screw.

[0032] In this embodiment, the screw pitch and groove depth are carefully designed, and the volume of metal powder pushed by the screw in one revolution is fixed. By controlling the speed and angle of the second drive motor, the volume of metal powder pushed by the screw can be controlled, thereby controlling the powder delivery flow rate. The screw is made of wear-resistant metal to resist long-term wear from the metal powder. The second drive motor can be a stepper motor or a servo motor.

[0033] In some embodiments of the present invention, the flow detection element 5 is a ring charge sensor.

[0034] In this embodiment, the ring charge sensor is a passive sensor based on the principle of electrostatic induction. Its main body is a metal ring electrode arranged around the inner wall of the powder feeding tank 7, with insulating coating, and coaxially arranged with the powder feeding tank 7. When charged powder particles flow through this ring area with a carrier gas, such as argon, a changing induced charge is formed between the particles and the ring electrode. This charge is converted into a voltage signal by a high input impedance charge amplifier, and after filtering, shaping, and linearization, a standard 4mA to 20mA current signal is output. The amplitude of this signal has a good linear relationship with the powder mass flow rate per unit time, and the response time is ≤10ms. Its installation position is downstream of the piston switch 3, on the inner wall of the powder feeding tank 7, without intruding into the gas-powder flow channel, thus avoiding disturbance to the stability of powder conveying. Of course, as an alternative embodiment, a high-speed camera, an optical obstruction sensor, or an optical scattering sensor can also be used.

[0035] The four flow detection elements 5 provided in this embodiment offer a real-time powder flow sensing solution that is highly responsive, non-contact, resistant to airflow disturbances, and compatible with inert protective atmosphere environments. This solution does not rely on mechanical contact or weighing principles, avoiding the hysteresis and clogging risks of traditional mass flow meters under conditions of powder particulate matter, low density, high flow velocity, and gas-solid two-phase flow. It achieves quantitative characterization of instantaneous powder flux through different physical mechanisms, providing a millisecond-level feedback signal source for the closed-loop control system of the controller 6, supporting the dynamic coordinated adjustment of multi-path component ratios during single-channel deposition.

[0036] In some embodiments of the present invention, such as Figure 1 and Figure 4 As shown, the powder feeding device also includes multiple powder storage tanks 1 and multiple pre-storage tanks 2, with each powder storage tank 1 connected in sequence to the corresponding pre-storage tank 2 and the corresponding powder feeding tank 7.

[0037] In this embodiment, each powder storage tank 1 is used to store a type of metal powder and to temporarily transport the metal powder to a pre-storage tank 2. The pre-storage tank 2 is used to transport the metal powder to the powder delivery tank 7. By setting up the powder storage tank 1 and the pre-storage tank 2, the metal powder is stored, providing a continuous supply of metal powder to the powder delivery tank 7.

[0038] In some embodiments of the present invention, the powder feeding device further includes a Venturi mixer, the inlet of which is connected to the outlet of a plurality of powder feeding tanks 7, and the outlet of which is connected to the inlet of a powder mixing tank.

[0039] In this embodiment, the Venturi mixer is a passive fluid mixing device designed based on Bernoulli's principle. Its core structure includes a converging section, a throat, and a diverging section, which are sequentially connected along the flow direction of the gas-powder mixture. When the carrier gas carries multiple streams of metal powder through the mixer, the flow velocity increases and the static pressure decreases at the throat due to the reduced cross-sectional area. This creates a local negative pressure suction effect at the merging points of the outlets of each powder feeding tank 7, causing different metal powders to undergo forced convergence, shearing, and preliminary mixing in the throat region before entering the mixing tank. The Venturi mixer can be machined into a single piece of metal, and the material can be selected from 316L stainless steel or titanium alloy to ensure both powder erosion resistance and inert atmosphere compatibility.

[0040] The Venturi mixer used in this embodiment has the following effects: 1. Realize dynamic and real-time ratio control: By independently and synchronously adjusting the feeding rate of each powder feeding tank 7, the system can change the chemical composition of the mixed powder in real time and continuously during operation. This is the core technical basis for manufacturing composition gradient functional materials. The response speed of the mixing ratio change is extremely fast, and it is only limited by the response time of the powder feeding tank 7 and the controller 6. 2. Improve mixing uniformity and conveying stability: (1) Strong dispersion: The turbulence of the Venturi mixer can effectively disperse powder agglomeration, especially for fine and easily agglomerated nano or micron-sized powders, the effect is significant. (2) Prevent stratification: During the argon gas conveying process, the powder is in a suspended state, which reduces the risk of gravity settling and stratification in the pipeline due to density differences. (3) Stable flow pattern: The gas-solid two-phase flow formed is relatively stable, which helps to achieve continuous and pulse-free stable powder feeding, which is crucial for the forming quality of additive manufacturing and cladding.

[0041] In some alternative embodiments, the Venturi mixer can be replaced by a perforated plate static mixer or a spiral guide vane premixing chamber, both of which can complete a short-range, low-delay, and high-response initial mixing process before the powder enters the main mixing tank without adding active drive components.

[0042] In some embodiments of the present invention, the mixing tank includes a buffer chamber, a pressure stabilizing chamber, and a venturi tube. The buffer chamber and the pressure stabilizing chamber are sealed together. The venturi tube is located inside the buffer chamber and the pressure stabilizing chamber, at their connection point. The inlet end of the venturi tube communicates with the buffer chamber, and the outlet end of the venturi tube communicates with the pressure stabilizing chamber. The buffer chamber is connected to the outlet of the venturi mixer. At least one tangential air inlet is provided on the side wall of the buffer chamber for connecting high-pressure inert gas. A stirring mechanism is provided inside the pressure stabilizing chamber, and a vibration mechanism is provided on the outer wall of the pressure stabilizing chamber.

[0043] In this embodiment, the buffer chamber is a cylindrical cavity with a powder inlet at its top center for receiving different metal powders premixed by the Venturi mixer. At least one tangential air inlet is located on the upper side wall, connected to a high-purity inert gas source, such as argon. Argon gas is injected at high speed through the tangential inlet, creating a strong forced rotating airflow field within the buffer chamber, achieving a "vortex structure." This structure is not a mechanical blade but is naturally formed by airflow dynamics. The Venturi tube is used for initial premixing as the airflow carries the powder downwards. The pressure stabilizing chamber is a vertical cylinder with a conical bottom to facilitate powder concentration towards the outlet under gravity. A discharge valve is located at the bottom of the cone.

[0044] The stirring mechanism includes a vertically mounted rotating shaft, a stirring paddle mounted on the shaft, and a drive element that drives the shaft to rotate. The distance between the stirring paddle and the inner wall of the pressure stabilizing chamber is 2mm to 5mm, and the stirring paddle rotates at a speed of 15 to 20 rpm. The small gap between the stirring paddle and the inner wall of the pressure stabilizing chamber, along with the extremely low rotation speed, ensures overall agitation of the metal powder rather than high-speed shearing. The vibration mechanism is located on the outer wall of the pressure stabilizing chamber and includes several high-frequency, low-amplitude pneumatic piston vibrators or electromagnetic vibrators.

[0045] The working process of the mixing tank is a dynamic and continuous physical process, which can be divided into three stages: 1. Feeding and Primary Premixing Stage: Metal powders of different compositions are fed into the buffer chamber from the top inlet according to a set ratio. Simultaneously, argon gas is injected at high speed from the tangential inlet, forming a stable vortex. The falling powder is immediately entrained in the vortex, and the different metal powders collide and mix violently under strong centrifugal force and turbulence, achieving the first step of forced premixing. This effectively breaks up powder agglomeration and provides preliminary homogenization for materials with large density differences. The vortex also acts as a pressure buffer, balancing pressure fluctuations introduced during feeding and preventing powder backflow.

[0046] 2. Main Mixing and Activation Stage: After preliminary mixing, the powder, carried by airflow and gravity, enters the pressure stabilizing chamber below in a dispersed state through the Venturi tube. Details are as follows:

[0047] (1) Low-speed stirring structure start-up: The large-sized blades rotate slowly, producing a gentle, overall tumbling and axial movement of the powder, achieving uniform mixing on a macroscopic scale. Its "wall scraping" effect can prevent the powder from adhering to the inner wall under the influence of heat or static electricity.

[0048] (2) Vibration mechanism works in concert: The vibrator attached to the can wall generates high-frequency micro-amplitude mechanical waves. This energy is transferred to the powder, which can effectively destroy the van der Waals forces and electrostatic forces between particles, thus "activating" the powder and greatly enhancing its flowability.

[0049] 3. Pressure Stabilization and Conveying Stage: The entire powder mixing process is conducted in an argon atmosphere. Pressure sensors monitor in real time, and the control system adjusts the intake and exhaust to maintain stable pressure. This pressure-stabilized environment prevents air and moisture intrusion, thus preventing powder oxidation; it also stabilizes the powder's bulk density and fluidization state, which is a prerequisite for stable, continuous, and precise powder delivery. The uniformly mixed powder is finally output from the cone-bottom outlet in a stable "mass flow" form under the assistance of gravity, vibration, and a weak fluidizing gas, and is directly conveyed to the laser deposition head.

[0050] The above structure achieves the following effect: 1. Extremely high mixing uniformity: It adopts a three-stage mixing mechanism of "pneumatic swirl premixing" + "mechanical overall turning" + "vibration activation", which takes into account both macroscopic dispersion and microscopic deagglomeration. It is especially suitable for high-quality uniform mixing of multi-element powders with huge differences in density and particle size.

[0051] 2. Anti-oxidation and anti-pollution: The fully enclosed argon environment provides crucial protection for the preparation of active materials such as titanium alloys, aluminum alloys, and high-temperature alloys.

[0052] 3. No dead angles and no clogging: The application of the vibration device fundamentally solves the problems of powder accumulation and bridging at the bottom of the cone and corners, ensuring 100% emptying rate of the hopper and continuous and stable discharge, which is crucial for the stability of additive manufacturing processes for long-term and large components.

[0053] 4. Low shear and low damage: The entire process avoids high-speed mechanical shear, protecting the original sphericity of the powder, especially avoiding the breakage of brittle ceramic phases or the cold welding of easily deformable particles, thus maintaining the excellent flowability of the powder.

[0054] 5. High process repeatability: The pressure stabilization design ensures stable powder properties. Combined with loss-in-weight metering, it enables high-precision and high-repeatability control of powder feeding rate and mixing ratio, which is the basis for preparing precisely composed gradient functional materials or composite materials.

[0055] In some embodiments of the present invention, the laser-directed energy deposition system for voxel-scale multimaterial metal fabrication further includes a gas delivery element, a dust removal element, and a cooling element. The gas delivery element delivers inert protective gas to the powder feeding tank 7. The dust removal element removes dust and fumes from the deposition layer. The cooling element cools the laser device.

[0056] In this embodiment, the gas delivery element refers to a fluid control system that continuously supplies inert gas to the powder delivery path to isolate oxygen and prevent oxidation of the metal powder. It includes a gas source interface, a pressure regulating valve, a flow meter, an electromagnetic control valve, a pressure stabilizing buffer tank, and multiple branch gas pipes. The gas source can be high-purity argon or an argon-nitrogen mixture. After being connected to the system through the gas source interface, pulsation is eliminated by the pressure stabilizing buffer tank, and the electromagnetic control valve opens and closes as needed. The flow meter monitors the carrier gas flow rate in real time, and finally, the gas is delivered to each powder delivery tank 7 through the branch gas pipes, forming a stable and controllable powder-carrying gas flow. This element not only ensures the chemical stability of the powder delivery process but also participates in powder fluidization and accelerated delivery.

[0057] The dust collection element refers to the functional module used to dynamically capture condensed metal vapors, unmelted splash particles, and high-temperature pyrolysis fumes generated during laser deposition. It includes a negative pressure suction port, flexible suction hose, cyclone separator, filter, explosion-proof fan, and dust recovery box. The negative pressure suction port is located at the deposition head, at approximately a 45° angle to the centerline of the molten pool, ensuring efficient coverage of the dust diffusion area without interfering with the powder delivery airflow and protective air curtain. The explosion-proof fan provides continuous negative pressure, causing the dust-laden airflow to undergo centrifugal sedimentation of coarse powder through the cyclone separator, followed by the filter to trap submicron particles. Clean air is then discharged by the fan or recirculated back to the internal purification system. The cooling element refers to the heat exchange system that actively manages the laser device's thermal performance and maintains stable optical performance and electro-optical conversion efficiency. It includes a closed-loop water-cooled unit, circulation piping, internal heat exchanger plate, and temperature feedback sensor. The coolant is a mixture of deionized water and ethylene glycol, provided by the water-cooled unit at a constant temperature and flow rate. This coolant is circulated through the piping to the internal heat exchanger plate of the laser, carrying away the heat generated. The temperature feedback sensor monitors the temperature of key measuring points on the laser housing in real time and transmits the signal to the controller 6. When the temperature exceeds the threshold, the laser power is automatically reduced or an alarm is triggered.

[0058] In some embodiments of the present invention, the laser-directed energy deposition system for voxel-scale metal multimaterial fabrication further includes a molding chamber and a door.

[0059] In this embodiment, the forming chamber and the door together constitute a sealable deposition workspace. Its core function is to provide a controlled physical environment for the laser-directed energy deposition process, ensuring the stability of the inert atmosphere, operational safety, and process repeatability. The forming chamber is a rigid box structure, typically made of stainless steel or aluminum alloy. The inner walls are polished or coated with a high-temperature resistant and anti-oxidation coating to inhibit powder adhesion and facilitate cleaning. The chamber is generally rectangular or cylindrical, with a laser entrance window at the top and a substrate mounting platform and lifting mechanism interface integrated at the bottom. The door is a hinged or sliding sealed door, with a sealing ring between the door and the chamber. Airtightness under positive pressure is achieved through a pneumatic clamping device or manual locking bolts.

[0060] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A laser-directed energy deposition system for voxel-scale multi-material metal fabrication, comprising a powder feeding device and a controller, wherein the powder feeding device and the controller are electrically connected; characterized in that, The powder feeding device includes multiple powder feeding tanks, multiple flow control switches, a powder mixing tank, and powder feeding nozzles; the outlets of the multiple powder feeding tanks are all connected to the powder mixing tank, and the outlet of the powder mixing tank is connected to the powder feeding nozzles; each powder feeding tank is equipped with one of the flow control switches; the controller is configured to: control the opening degree of each flow control switch in real time according to the real-time preset ratio of each metal powder, so as to control the powder feeding flow rate of metal powder in each powder feeding tank to the powder mixing tank.

2. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 1, characterized in that, The powder feeding device also includes multiple flow detection elements, each of which is located in the corresponding powder feeding tank and is used to detect the powder feeding flow in real time. The controller is also configured to adjust the opening degree of each flow control switch in real time according to the powder feeding flow detected in real time by each flow detection element and the corresponding preset ratio.

3. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 1, characterized in that, The flow control switch includes a piston switch and a first drive motor. The size of the piston switch matches the cross-sectional size of the inner wall of the powder feeding tank. The piston switch is rotatably disposed inside the powder feeding tank about the radial direction of the powder feeding tank. The output end of the first drive motor is connected to the piston switch.

4. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 1, characterized in that, The flow control switch includes a screw and a second drive motor. The screw is coaxially arranged with the powder feeding tank, and the diameter of the screw matches the cross-sectional dimension of the inner wall of the powder feeding tank. The output end of the second drive motor is connected to the screw.

5. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 2, characterized in that, The flow detection element is a ring charge sensor, a high-speed camera, an optical obstruction sensor, or an optical scattering sensor.

6. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 1, characterized in that, The powder feeding device also includes multiple powder storage tanks and multiple pre-storage tanks, with each powder storage tank connected in sequence to the corresponding pre-storage tank and the corresponding powder feeding tank.

7. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 1, characterized in that, The powder feeding device also includes a Venturi mixer, the inlet of which is connected to the outlet of the plurality of powder feeding tanks, and the outlet of which is connected to the inlet of the powder mixing tank.

8. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 7, characterized in that, The mixing tank includes a buffer chamber, a pressure stabilizing chamber, and a venturi tube; the buffer chamber and the pressure stabilizing chamber are sealed together, and the venturi tube is located inside the buffer chamber and the pressure stabilizing chamber, at their connection point. The inlet end of the venturi tube communicates with the buffer chamber, and the outlet end of the venturi tube communicates with the pressure stabilizing chamber; the buffer chamber is connected to the outlet of the venturi mixer; at least one tangential air inlet is provided on the side wall of the buffer chamber for connecting high-pressure inert gas; a stirring mechanism is provided inside the pressure stabilizing chamber, and a vibration mechanism is provided on the outer wall of the pressure stabilizing chamber.

9. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 8, characterized in that, The stirring mechanism includes a vertically arranged rotating shaft, a stirring paddle disposed on the outer wall of the rotating shaft, and a driving element for driving the rotating shaft to rotate; the distance between the stirring paddle and the inner wall of the pressure stabilizing chamber is 2mm to 5mm, and the rotation speed of the stirring paddle is 15 rpm to 20 rpm.

10. The laser-directed energy deposition system for voxel-level metallic multimaterial fabrication according to claim 1, characterized in that, It also includes a gas conveying element and a dust removal element; the gas conveying element is used to convey inert protective gas to the powder feeding tank; the dust removal element is used to extract dust and flue gas from the deposition layer.

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