Powder bed laser additive manufacturing apparatus and method for heterogeneous materials

Abstract

Disclosed in the present invention are a powder bed laser additive manufacturing apparatus and method for heterogeneous materials. The apparatus comprises a fixed-point powder-suction ultrasonic powder feeding system, an electrostatic powder spreading system, and a powder bed additive manufacturing forming system. The fixed-point powder-suction ultrasonic powder feeding system and the electrostatic powder spreading system are arranged in the powder bed additive manufacturing forming system. The present invention improves material utilization and manufacturing efficiency by means of a heterogeneous-material powder spreading approach combining ultrasonic powder feeding and electrostatic powder spreading. In addition, in the present invention, a scraper, an electrostatic powder spreading apparatus and a powder spreading carriage are integrated, which enhances the flexibility and applicability of devices, reduces the switching and waiting time between the devices, and improves production efficiency. Meanwhile, the present invention realizes automatic replacement of powder feeding needles, without manual intervention, thereby greatly improving working efficiency. Furthermore, by using the powder feeding needles of different diameters, the present invention not only maintains the efficiency of powder spreading, but also improves the quality of powder spreading at the interface of heterogeneous materials, thereby enhancing the bonding effect at a final heterogeneous material interface.

Description

A laser additive manufacturing apparatus and method for heterogeneous material powder bed Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, and particularly relates to a laser additive manufacturing apparatus and method for heterogeneous material powder bed. Background Technology

[0002] Additive manufacturing technology is currently listed as one of the twelve disruptive technologies that will determine the future economy. It is one of the fastest-growing, most actively researched, and most closely watched disciplines in the world's advanced manufacturing field, possessing broad application prospects and enormous development potential. Metal heterogeneous additive manufacturing technology refers to the process of combining multiple materials to create single complex functional components with diverse material structures, meeting the specific requirements of material performance, function, and structural integration in different application scenarios. Globally, new processes, principles, materials, and applications related to additive manufacturing are constantly emerging. With the development of contemporary science and technology and the innovation of technological industries, metal heterogeneous additive manufacturing technology has shown broad application prospects in aerospace, military, medical, and other fields. This technology breaks through the limitations of traditional manufacturing methods, enabling precise control and optimization of material composition and structure from the microscopic to the macroscopic scale, providing strong support for the development of high-performance, multifunctional, and lightweight advanced manufacturing products.

[0003] The forming principle of powder bed laser melting is as follows: First, a layer of metal powder to be printed is spread evenly on the substrate. Then, the laser heats and melts the metal powder in a designated area through scanning galvanometers and field lenses to form a cladding layer. The substrate is then lowered by one layer, and the system re-spreads the powder, repeating the above steps until printing is complete. In the field of additive manufacturing using powder bed melting, heterogeneous material additive manufacturing typically requires the heterogeneous material to be pre-placed freely and precisely on the powder bed before the next step of laser heating and melting. Mainstream heterogeneous material pre-placement methods include doctor blade powder feeding, ultrasonic powder feeding, electrophotographic powder feeding, and doctor blade + ultrasonic-assisted powder feeding. Unlike the traditional single-doctor layer-by-layer printing method for heterogeneous materials, ultrasonic powder feeding enables precise one-time pre-placement of heterogeneous material powder, greatly improving powder utilization and reducing powder mixing and the difficulty of heterogeneous material powder recovery. During ultrasonic powder feeding, the powder distribution may be affected by various factors, including feeding speed, vibration frequency, substrate flatness, and powder type. Powder particles dropped onto the substrate by ultrasonication often accumulate into hill-like formations before collapsing. To ensure a tight fit at the interface between heterogeneous materials in the final formed part, more powder is typically needed at this interface to reduce defects such as holes and cracks. This results in uneven powder distribution at the interface, exacerbated by the repeated powder distribution path of the ultrasonic transducer. Currently, research on ultrasonic powder delivery is still incomplete, and ultrasonic powder delivery technology suffers from a series of problems, including uneven surface distribution after powder delivery, excessive powder thickness at the interface between heterogeneous materials, and increased powder mixing caused by the scraper. These issues all negatively impact the final printing quality. Therefore, we propose a heterogeneous material powder bed laser additive manufacturing device and method. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a heterogeneous material powder bed laser additive manufacturing apparatus and method. In the powder bed additive manufacturing stage, the main material powder (powder placed in a powder cylinder) is first spread evenly from the powder cylinder to the upper surface of the substrate using a flexible scraper. Then, the powder suction system is activated, and the controller sends control signals to the motor to drive the three-axis slide table according to a predetermined path program, causing the powder suction tube to suction powder along a designated path. After completion, the powder suction system is turned off, and the ultrasonic powder dropping system is activated. A coarse-diameter powder delivery needle first fills the non-edge areas where powder has been suctioned, and then automatically replaces it with a fine-diameter powder delivery needle. Subsequently, powder is delivered to the edge areas where powder has been suctioned. Finally, the electrostatic powder spreading system operates; as the powder spreading carriage moves forward, the electric field strength between the electrodes can be adjusted in real time according to the material properties, completing the powder spreading of one layer of heterogeneous material. The above steps are repeated for each subsequent layer, ultimately effectively improving the powder spreading quality of each layer and completing the heterogeneous material additive manufacturing process.

[0005] This invention is implemented as follows: a heterogeneous material powder bed laser additive manufacturing apparatus, comprising:

[0006] The system includes a fixed-point powder suction ultrasonic powder delivery system, an electrostatic powder spreading system, and a powder bed additive manufacturing system, wherein the fixed-point powder suction ultrasonic powder delivery system and the electrostatic powder spreading system are both installed within the powder bed additive manufacturing system.

[0007] The powder bed additive manufacturing forming system includes an optical path system, a forming cavity, a forming cylinder, a powder cylinder, and a flexible scraper. The powder cylinder is located at the bottom of the forming cavity and is connected to the inside of the forming cavity. The forming cylinder is located at the bottom of the forming cavity and is connected to the inside of the forming cavity. The flexible scraper is located at one end of the bottom of the forming cavity.

[0008] The fixed-point powder suction ultrasonic powder delivery system comprises an ultrasonic transducer, multiple sets of powder delivery needles, a suction tube, and a needle frame. The powder delivery needles are hung on the needle frame, and the needle frame is located inside the molding cavity. One set of powder delivery needles is detachably installed inside the ultrasonic transducer.

[0009] The electrostatic powder spreading system includes an electrostatic powder spreading mechanism and a powder spreading cart. The powder spreading cart is horizontally movable inside the forming cavity, and the electrostatic powder spreading mechanism is located at the bottom of the powder spreading cart, above the powder cylinder and the powder recovery cylinder.

[0010] Optionally, a lead screw slide is provided on one side of the molding cavity, and a double-rod cylinder is connected to the inside of the molding cavity via the lead screw slide. The movable end of the double-rod cylinder is provided with an internal support gripper. The needle holder is located at the bottom of the lead screw slide, and a placement hole for placing powder feeding needles is provided on the needle holder. The internal support gripper is vertically aligned with the placement hole.

[0011] Optionally, the powder delivery needle tube is composed of a coarse-diameter powder delivery needle tube A, a fine-diameter powder delivery needle tube A, a coarse-diameter powder delivery needle tube B, and a fine-diameter powder delivery needle tube B, and all three are hung on a needle tube rack.

[0012] Optionally, the ultrasonic transducer is composed of a front cover plate, a rear cover plate, a piezoelectric ceramic sheet, an electrode sheet, and a hollow bolt, and the powder delivery needle tube is detachably installed inside the ultrasonic transducer.

[0013] Optionally, a three-axis slide system is provided at the upper end of one side of the molding cavity. The ultrasonic transducer is connected to the three-axis slide system, so that the ultrasonic transducer is movably positioned inside the molding cavity through the three-axis slide system. The powder suction tube is located between the ultrasonic transducer and the three-axis slide system. A push-pull electromagnet is provided at the transmission end of the three-axis slide system. The push-pull electromagnet is located close to the ultrasonic transducer and is used to fix the powder feeding needle tube.

[0014] Optionally, the electrostatic powder spreading mechanism comprises an upper electrode plate and an insulating layer, the insulating layer being disposed at the bottom of the upper electrode plate, the flexible scraper being disposed on the outside of the powder spreading cart, a powder bed being disposed at the lower end of the forming cavity, and the insulating layer being located above the powder bed, and a high-voltage AC power supply being electrically connected between the upper electrode plate and the powder bed.

[0015] Optionally, a powder spreading guide rail is provided at the lower end of one side of the molding cavity, and the powder spreading cart is drivenly connected to the powder spreading guide rail, so that the powder spreading cart is horizontally positioned inside the molding cavity through the powder spreading guide rail. A lead screw guide rail is provided at the end of the powder spreading cart, and the upper electrode plate and the insulating layer are both drivenly connected to the lead screw guide rail, so that the upper electrode plate and the insulating layer are both raised and lowered within the powder spreading cart through the lead screw guide rail.

[0016] Optionally, the optical path system is located at the upper end of the forming cavity, and the optical path system consists of a collimator, a scanning galvanometer, and a field lens.

[0017] A method for heterogeneous material powder bed laser additive manufacturing, employing the heterogeneous material powder bed laser additive manufacturing apparatus as described in the claims, is characterized by comprising the following steps:

[0018] S1: Preparation Phase

[0019] S11. Preparation of Powder Bed Additive Manufacturing System: Use 3D design software to create a model of a heterogeneous material part; add support and slice the model data, and at the same time, the computer software generates corresponding powder suction and powder dropping paths based on the slice information and imports them into the powder bed additive manufacturing system; add the main material powder and the forming substrate into the powder cylinder and the forming cylinder respectively, level the forming substrate, and complete the preparation of the powder bed additive manufacturing system.

[0020] S12. Preparation of the fixed-point ultrasonic powder delivery system: Calculate the required amount, fill each powder delivery needle with the heterogeneous material, and place each powder delivery needle vertically on the needle holder and inside the ultrasonic transducer. For the powder delivery needle inside the ultrasonic transducer, first select a large-diameter needle, and then clamp the powder delivery needle by energizing the push-pull electromagnet; return the position of the lead screw slide to zero; return the coordinates of the three-axis slide system to zero, and check whether the ultrasonic generator and vacuum powder delivery machine can operate normally.

[0021] S13. Preparation of electrostatic powder spreading system: Return the powder spreading cart and lead screw guide rail to zero, and connect the lines between the electrodes.

[0022] S2: Powder application stage:

[0023] S21. The powder bed additive manufacturing system is in operation and executes the slicing program. When it is necessary to print heterogeneous materials, after the flexible scraper lays a layer of main material powder in the powder cylinder, the motor shaft on the side of the powder spreading carriage drives the flexible scraper to rotate to the vertically upward idle position.

[0024] S22. Operation of the fixed-point powder suction ultrasonic powder delivery system: First, the vacuum powder suction machine is started, and the three-axis slide system drives the powder suction tube to move along the predetermined path program to suction powder, removing a layer of powder from the area where the material to be replaced; then, the ultrasonic transducer moves to the starting point of the area inside the powder that has been suctioned under the action of the three-axis slide, the ultrasonic generator is started, and then the ultrasonic transducer moves along the designated path, using a large-diameter powder delivery needle to accurately drop powder to fill the non-edge area of ​​the powder that has been suctioned. After the powder dropping is completed, the ultrasonic generator is turned off, and the ultrasonic transducer moves to the side of the needle holder in front of the empty needle slot;

[0025] S23. Needle removal: First, the double-rod cylinder pushes out the inner support gripper, then the lead screw slide moves down, so that the gripper head extends into the inside of the powder delivery needle tube in the ultrasonic transducer. Then, the inner support gripper starts, the push-pull electromagnet is de-energized, the lead screw slide moves up, the double-rod cylinder retracts, the lead screw slide moves down, and finally the inner support gripper closes, the lead screw slide returns to zero, and the automatic replacement of the large-diameter powder delivery needle tube is completed.

[0026] S24. Replace the fine-diameter powder delivery needle and assemble it in reverse order of S23. After the needle is automatically replaced, the ultrasonic transducer moves to the starting point of the edge area where the powder has been removed, the ultrasonic generator starts, and the fine-diameter powder delivery needle accurately delivers powder to fill the edge area where the powder has been removed. After the powder delivery is completed, the ultrasonic generator is turned off; the three-dimensional coordinates of the three-axis slide are returned to zero.

[0027] S25. Operation of the electrostatic powder spreading system: First, turn on the high-voltage AC power supply. An AC electric field with rapidly alternating polarity will be formed between the upper electrode plate and the powder bed. Start the powder spreading carriage and move it along the powder spreading guide rail. At the same time, the lead screw guide rail drives the insulating layer and the upper electrode plate to move vertically. Adjust the electric field strength between the upper electrode plate and the powder bed. When the upper electrode plate passes the forming cylinder and is located above the powder material, the powder will oscillate up and down under the AC electric field force, thereby spreading the powder.

[0028] Optionally, in S25, the electric field strength E is set to a range of 200-2000V / mm. The electric field strength E is adjusted by driving the upper electrode plate through the lead screw and guide rail, and the electric field strength E satisfies E=U / d.

[0029] Where U is the AC voltage applied by the high-voltage AC power supply, E is the electric field strength between the upper electrode plate and the upper surface of the powder in the molding cylinder, and d is the distance between the upper electrode plate and the upper surface of the powder in the molding cylinder.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. This invention employs a heterogeneous powder placement method using ultrasonic powder feeding and electrostatic powder placement during the metal additive manufacturing process, achieving precise pre-placement of heterogeneous powder materials on the substrate. This powder placement method enables one-time powder placement of each layer in heterogeneous material additive manufacturing, eliminating the need for segmented powder placement and laser irradiation printing of each layer in traditional heterogeneous materials. This avoids the material waste and uneven distribution problems that may occur in traditional methods, thereby improving material utilization and manufacturing efficiency.

[0032] 2. This invention integrates the scraper, electrostatic powder spreading device, and powder spreading cart into one unit, reducing the possibility of hardware interference between various systems, providing a large amount of free space for the forming cavity, and further enhancing the flexibility and applicability of the equipment. This helps to reduce the conversion and waiting time between equipment and improve production efficiency.

[0033] 3. During the ultrasonic powder delivery process, the present invention can realize the automatic replacement of the powder delivery needle without manual intervention, which greatly improves the work efficiency. At the same time, the method of using a large-diameter powder delivery needle to deliver powder inside the contour of the heterogeneous material and a small-diameter powder delivery needle to deliver powder to the edge of the contour of the heterogeneous material further improves the powder spreading quality at the junction of heterogeneous materials without losing powder spreading efficiency, and indirectly enhances the final interface connection effect of heterogeneous materials.

[0034] 4. Compared with existing technologies based on scraper and ultrasonic powder feeding, this invention adopts an electrostatic powder spreading method after ultrasonic powder feeding, which greatly improves the problem of uneven thickness of the interface layer of heterogeneous materials caused by ultrasonic powder feeding. This electrostatic powder spreading system can adjust the electric field strength according to different material properties, further enhancing the powder spreading effect. At the same time, since electrostatic powder spreading effectively reduces the powder mixing phenomenon caused by traditional scraper powder spreading, it ensures the consistency and reliability of the quality of heterogeneous material additive manufacturing. This provides a new composite powder spreading method for heterogeneous material additive manufacturing.

[0035] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0036] Figure 1 is a schematic diagram of the structure of the heterogeneous material powder bed laser additive manufacturing device provided by the present invention;

[0037] Figure 2 is a schematic diagram of the powder suction tube provided by the present invention performing regional fixed-point powder suction;

[0038] Figure 3 is a schematic diagram of the ultrasonic powder delivery process provided by the present invention;

[0039] Figure 4 is a schematic diagram of the electrostatic powder spreading process provided by the present invention;

[0040] Figure 5 is a schematic diagram of the protrusions at the interface of heterogeneous materials and the unevenness of the powder surface after ultrasonic powder removal provided by the present invention.

[0041] Figure 6 is a schematic diagram of the effect after electrostatic powder spreading and leveling provided by the present invention;

[0042] Figure 7 is a schematic diagram of the coarse-diameter powder delivery needle filling the non-edge area of ​​the powder that has been removed and the fine-diameter powder delivery needle filling the edge area of ​​the powder that has been removed, provided by the present invention.

[0043] Figure 8 is a schematic diagram of the internal structure of the flexible scraper and electrostatic powder spreading system provided by the present invention.

[0044] Figure 9 is a schematic diagram of the ultrasonic transducer and powder suction tube provided by the present invention.

[0045] Figure 10 is a structural schematic diagram of the automatic pipe changing device provided by the present invention;

[0046] Figure 11 is a schematic flowchart of the heterogeneous material powder bed laser additive manufacturing method provided by the present invention.

[0047] In the diagram: 1. Optical path system; 2. Molding cavity; 3. Powder recovery cylinder; 4. Molding cylinder; 5. Powder cylinder; 6. Triaxial slide system; 7. Ultrasonic transducer; 8. Powder suction tube; 9. Powder spreading guide rail; 10. Electromagnet; 11. Screw slide; 12. Double-rod cylinder; 13. Internal support gripper; 14. Powder feeding needle tube; 15. Powder spreading cart; 16. Flexible scraper; 17. Main powder material A; 18. Powder material B; 19. Substrate; 20. High voltage AC power supply; 21. Powder bed; 22. Upper electrode plate; 23. Insulating layer; 24. Screw guide rail; 25. Needle tube frame; 26. Non-edge area where powder has been suctioned; 27. Edge area where powder has been suctioned; 28. Coarse diameter powder feeding needle tube A; 29. ​​Fine diameter powder feeding needle tube A; 30. Coarse diameter powder feeding needle tube B; 31. Fine diameter powder feeding needle tube B. Detailed Implementation

[0048] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given in conjunction with the accompanying drawings.

[0049] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0050] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0051] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0052] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0053] The structure of the present invention will now be described in detail with reference to the accompanying drawings.

[0054] As shown in Figures 1 to 11, an embodiment of the present invention provides a heterogeneous material powder bed laser additive manufacturing apparatus, comprising: a fixed-point powder suction and ultrasonic powder feeding system, an electrostatic powder spreading system, and a powder bed additive manufacturing forming system, wherein the fixed-point powder suction and ultrasonic powder feeding system and the electrostatic powder spreading system are both disposed within the powder bed additive manufacturing forming system;

[0055] The powder bed additive manufacturing forming system comprises an optical path system 1, a forming cavity 2, a forming cylinder 4, a powder cylinder 5, and a flexible scraper 16. The powder cylinder 5 is located at the bottom of the forming cavity 2 and is connected to the interior of the forming cavity 2. The forming cylinder 4 is located at the bottom of the forming cavity 2 and is connected to the interior of the forming cavity 2. The flexible scraper 16 is located at one end of the bottom of the forming cavity 2.

[0056] As shown in Figures 1 to 9, the flexible scraper 16 described above can spread the powder in the powder cylinder 5 onto the forming cylinder 4.

[0057] The fixed-point suction and ultrasonic powder delivery system comprises an ultrasonic transducer 7, multiple sets of powder delivery needles 14, a suction tube 8, and a needle frame 25. The powder delivery needles 14 are hung on the needle frame 25, and the needle frame 25 is located inside the molding cavity 2. One set of powder delivery needles 14 is detachably installed inside the ultrasonic transducer 7.

[0058] The electrostatic powder spreading system includes an electrostatic powder spreading mechanism and a powder spreading cart 15. The powder spreading cart 15 is horizontally and movably arranged inside the forming cavity 2, and the electrostatic powder spreading mechanism is arranged at the bottom of the powder spreading cart 15. The electrostatic powder spreading mechanism is located above the powder cylinder 5 and the powder recovery cylinder 3.

[0059] Furthermore, a lead screw slide 11 is provided on one side of the molding cavity 2. A double-rod cylinder 12 is connected to the molding cavity 2 via the lead screw slide 11. The movable end of the double-rod cylinder 12 is provided with an internal support gripper 13. The needle tube frame 25 is located at the bottom of the lead screw slide 11, and the needle tube frame 25 is provided with a placement hole for placing the powder feeding needle tube 14. The internal support gripper 13 is perpendicularly corresponding to the placement hole. The powder feeding needle tube 14 is composed of a coarse-diameter powder feeding needle tube A28, a fine-diameter powder feeding needle tube A29, a coarse-diameter powder feeding needle tube B30, and a fine-diameter powder feeding needle tube B31. All three powder feeding needle tubes are hung on the needle tube frame 25.

[0060] As shown in Figures 1 to 9, through the coordinated design of the double-rod cylinder 12, the internal support gripper 13, and the needle holder 25, during the powder spreading stage, the powder delivery needle 14 inside the ultrasonic transducer 7 can be replaced at any time with the powder delivery needle 14 on the needle holder 25 via the internal support gripper 13. The powder delivery needle 14 on the needle holder 25 is equipped with a fine-diameter powder delivery needle and a coarse and fine-diameter powder delivery needle filled with another material, thereby realizing automatic replacement of the powder delivery needle without manual intervention, effectively improving work efficiency.

[0061] It should be noted that by using powder delivery needles of different materials with coarse and fine diameters, powder can be delivered inside the contour of heterogeneous materials, while fine-diameter powder delivery needles can be used to deliver powder to the edge of the contour of heterogeneous materials. This not only improves the powder delivery efficiency but also enhances the powder delivery quality at the junction of heterogeneous materials, indirectly strengthening the final interface connection effect of heterogeneous materials.

[0062] Furthermore, the ultrasonic transducer 7 is composed of a front cover plate, a rear cover plate, a piezoelectric ceramic sheet, an electrode sheet, and a hollow bolt, and the powder delivery needle tube 14 is detachably installed inside the ultrasonic transducer 7.

[0063] It should be noted that the ultrasonic transducer 7 mentioned above needs to be connected to an external ultrasonic generator, and the powder suction tube 8 needs to be connected to an external vacuum powder suction machine. When printing reaches the corresponding stage, the computer sends a signal to control the on / off state of the two.

[0064] Furthermore, a triaxial slide system 6 is provided at the upper end of one side of the molding cavity 2. The ultrasonic transducer 7 is connected to the triaxial slide system 6 through a transmission connection, so that the ultrasonic transducer 7 is movably disposed inside the molding cavity 2 through the triaxial slide system 6. The powder suction tube 8 is disposed between the ultrasonic transducer 7 and the triaxial slide system 6. A push-pull electromagnet 10 is provided at the transmission end of the triaxial slide system 6. The push-pull electromagnet 10 is disposed close to the ultrasonic transducer 7 and is used to fix the powder feeding needle tube 14.

[0065] As shown in Figures 1 to 9, the three-dimensional coordinates of the three-axis slide system 6 mentioned above are changed by the control signal corresponding to the powder suction and discharge path transmitted by the controller. The powder suction and discharge path is generated by the software based on the three-dimensional model, and the range of action must at least include the entire area of ​​the forming cylinder. Thus, the ultrasonic transducer 7 can be used to drive the powder feeding needle tube 14 to move to any position, so as to realize the powder discharge work at any position.

[0066] Furthermore, the electrostatic powder spreading mechanism consists of an upper electrode plate 22 and an insulating layer 23. The insulating layer 23 is disposed at the bottom of the upper electrode plate 22. The flexible scraper 16 is disposed on the outside of the powder spreading cart 15. A powder bed 21 is disposed at the lower end of the forming cavity 2, and the insulating layer 23 is located above the powder bed 21. A high-voltage AC power supply 20 is electrically connected between the upper electrode plate 22 and the powder bed 21.

[0067] As shown in Figures 1 to 9, the insulating layer 23 is designed to prevent an electric arc from forming between the upper electrode plate 22 and the powder bed 21.

[0068] It should be noted that a high-voltage AC power supply 20 needs to be connected between the upper electrode plate 22 and the powder bed 21 platform to provide a sufficiently large electric field strength to vibrate and flatten the powder. The lower electrode is composed of the powder bed 21 and the powder, and both need to have a certain degree of conductivity to ensure normal current flow in the lower electrode.

[0069] Secondly, it is worth noting that the powder bed 21 needs to be grounded to avoid the powder in the molding cylinder 4 being affected by other electrical forces besides the high voltage AC electric field force, and to reduce the disturbance effect of the high voltage AC on the surrounding sensitive instruments and equipment.

[0070] Furthermore, a powder spreading guide rail 9 is provided at the lower end of one side of the molding cavity 2. The powder spreading cart 15 is connected to the powder spreading guide rail 9, so that the powder spreading cart 15 is horizontally positioned inside the molding cavity 2 via the powder spreading guide rail 9. A lead screw guide rail 24 is provided at the end of the powder spreading cart 15. The upper electrode plate 22 and the insulating layer 23 are both connected to the lead screw guide rail 24, so that the upper electrode plate 22 and the insulating layer 23 are both vertically and vertically positioned inside the powder spreading cart 15 via the lead screw guide rail 24.

[0071] As shown in Figures 1 to 9, through the design of the powder spreading cart 15 being connected to the powder spreading guide rail 9, the powder spreading cart 15 moves horizontally, so that the movement coverage of the powder spreading cart 15 includes at least the powder cylinder 5 to the powder recovery cylinder 3, thereby effectively increasing the powder spreading area.

[0072] Furthermore, the optical path system 1 is disposed at the upper end of the forming cavity 2, and the optical path system 1 consists of a collimator, a scanning galvanometer, and a field lens;

[0073] As shown in Figures 1 to 9, the optical path system 1, consisting of a collimator, a scanning galvanometer, and a field lens, allows the laser scanning range to cover the entire forming cylinder 4. This facilitates the laser to heat and melt the metal powder in the designated area through the scanning galvanometer and field lens, forming a cladding layer. Then, the substrate 19 descends by one layer, the system re-spreads the powder, and the above steps are repeated until printing is finished.

[0074] This invention also provides a method for heterogeneous material powder bed laser additive manufacturing, using the aforementioned heterogeneous material powder bed laser additive manufacturing apparatus, comprising the following steps:

[0075] S1. Preparation Phase:

[0076] S11. Preparation of Powder Bed Additive Manufacturing System: A model of a heterogeneous material part is established using 3D design software; the model data is supported and sliced, and the computer software generates corresponding powder suction and powder dropping paths based on the slicing information and imports them into the powder bed additive manufacturing system; the main material powder and the forming substrate 19 are added to the powder cylinder 5 and the forming cylinder 4 respectively, and the forming substrate 19 is leveled to complete the preparation of the powder bed additive manufacturing system.

[0077] S12. Preparation of the fixed-point ultrasonic powder delivery system: Calculate the amount of heterogeneous material and fill each powder delivery needle tube 14. Place each powder delivery needle tube 14 vertically on the needle tube frame 25 and inside the ultrasonic transducer 7. First, select a large-diameter needle tube for the powder delivery needle tube 14 inside the ultrasonic transducer 7. Then, energize the push-pull electromagnet 10 to clamp the powder delivery needle tube 14. Return the position of the lead screw slide 11 to zero. Return the coordinates of the three-axis slide system 6 to zero and check whether the ultrasonic generator and vacuum powder delivery machine can operate normally.

[0078] S13. Preparation of electrostatic powder spreading system: Return the powder spreading cart 15 and lead screw guide rail 24 to zero and connect the lines between the electrodes.

[0079] S2: Powder application stage:

[0080] S21. Operation of the powder bed additive manufacturing system: The powder bed additive manufacturing system performs additive manufacturing printing of parts layer by layer according to the slicing program; when the printing process does not require printing of heterogeneous materials, the side motor shaft of the powder spreading carriage 15 drives the flexible scraper 16 to rotate to the vertically downward working position for printing; when the printing process requires printing of heterogeneous materials, after the flexible scraper 16 spreads a layer of main material powder in the powder cylinder 5, the side motor shaft of the powder spreading carriage 15 drives the flexible scraper 16 to rotate to the vertically upward idle position, and the remaining powder spreading stage work is carried out according to the following steps;

[0081] S22. Operation of the Pre-selective Ultrasonic Powder Delivery System: First, the vacuum powder suction machine is started. The three-axis slide system 6 drives the powder suction tube 8 to move along a predetermined path to remove a layer of powder from the area where the material to be replaced. The moving speed of the powder suction tube 8 and the negative pressure of the vacuum powder suction machine should be set in advance by the experiment to ensure that the powder suction tube 8 precisely removes only one layer of powder per operation. Then, the ultrasonic transducer 7 moves to the starting point of the area where the powder has been removed under the action of the three-axis slide. The ultrasonic generator is started, and then the ultrasonic transducer 7 moves along the designated path. A large-diameter powder delivery needle precisely delivers powder to fill the non-edge area 26 where powder has been removed. After powder delivery, the ultrasonic generator is turned off, and the ultrasonic transducer 7 moves to the empty needle slot on the side of the needle holder 25. After the needle is automatically replaced, the ultrasonic transducer 7 moves to the starting point of the edge area 27 where powder has been removed, the ultrasonic generator is activated, and a small-diameter powder delivery needle precisely delivers powder to fill the edge area 27 where powder has been removed. After powder delivery, the ultrasonic generator is turned off. The three-dimensional coordinates of the three-axis slide are zeroed to avoid interference and collision between the three-axis slide and the powder spreading cart 15 in S.

[0082] S23. Needle removal: First, the double-rod cylinder (12) pushes out the inner support gripper (13), and then the lead screw slide moves down, so that the claw head of the inner support gripper (13) extends into the interior of the powder delivery needle tube (14) in the ultrasonic transducer (7). Then the inner support gripper (13) starts, the push-pull electromagnet (10) is de-energized, the lead screw slide moves up, the double-rod cylinder (12) retracts, the lead screw slide moves down, and finally the inner support gripper (13) closes, the lead screw slide (11) returns to zero, and the automatic replacement of the coarse diameter powder delivery needle tube is completed.

[0083] S24. Replace the fine-diameter powder delivery needle and assemble it according to the reverse process of S23. After the needle is automatically replaced, the ultrasonic transducer (7) moves to the starting point of the edge area (27) where the powder has been removed, the ultrasonic generator starts, and the fine-diameter powder delivery needle accurately drops powder to fill the edge area (27) where the powder has been removed. After the powder is dropped, the ultrasonic generator is turned off. The three-dimensional coordinates of the three-axis slide are returned to zero.

[0084] S25. Electrostatic powder spreading system operation: First, turn on the high-voltage AC power supply 20. An AC electric field with rapidly alternating polarity will be formed between the upper electrode plate 22 and the powder bed 21. In the process, it is often difficult to control the powder thickness at the junction of different material areas and at the beginning and end points of the ultrasonic transducer 7, resulting in uneven powder surface and inconsistent layer thickness in some areas. Start the powder spreading carriage 15 and move it along the powder spreading guide rail 9. At the same time, the lead screw guide rail 24 drives the insulating layer 23 and the upper electrode plate 22 to move vertically according to different material properties, adjusting the electric field strength between the upper electrode plate 22 and the powder bed 21. When the upper electrode plate 22 passes the forming cylinder 4 and is above the powder material, the conductive powder oscillates up and down under the AC electric field force. The high-concentration particle oscillation area tends to move to the low-concentration particle oscillation area, ultimately achieving the effect of uniform powder particle distribution and smooth powder spreading surface.

[0085] Specifically, as shown in Figures 5 and 6, the powder material mentioned above is composed of main powder material A17 and powder material B18.

[0086] Furthermore, assuming the AC voltage applied by the high-voltage AC power supply 20 is U, and the electric field strength between the upper electrode plate 22 and the upper surface of the powder in the molding cylinder 4 is E, the distance d between the upper electrode plate 22 and the upper surface of the powder in the molding cylinder 4 can be determined by the following relationship:

[0087] d=U / E

[0088] To achieve a good electrostatic powder spreading effect, the electric field strength E should be at least 200-2000 V / mm. Since different materials have varying conductivity, the selected electrostatic powder spreading electric field strength will also differ for different materials. In this system, the electric field strength can be adjusted in real time by the lead screw guide 24 according to the material, thereby optimizing the electrostatic powder spreading effect.

[0089] The novel working principle and usage process of this invention:

[0090] In the powder bed additive manufacturing process of this invention, when the powder spreading stage is reached, the computer determines whether each layer needs to be printed with a different material. When spreading powder for a non-different material printing layer, the flexible scraper 16 is placed in the working position, and the main material powder is spread and laser irradiation is performed normally. When a different material printing layer needs to be spread, the flexible scraper 16 is rotated upwards and placed in the idle position after the main material powder is spread. The motor drives the three-axis slide system 6 to move according to the predetermined path program, which drives the powder suction tube 8 to suck up powder along the specified path. Then, after the coarse-diameter powder feeding needle fills the non-edge area 26 where the powder has been sucked up, it is automatically replaced with the fine-diameter powder feeding needle. Then, the powder is fed to the edge area 27 where the powder has been sucked up. Finally, the electrostatic powder spreading device is started and moves back and forth. At the same time, the computer adjusts the electric field strength in real time according to the powder type to spread the powder evenly. This invention abandons the traditional doctor blade powder spreading device and instead adopts a heterogeneous material powder spreading method combining ultrasonic powder dropping and electrostatic powder spreading. This results in more uniform interlayer thickness and tighter interfacial bonding between different materials when printing heterogeneous material components. It also effectively avoids the powder mixing phenomenon caused by traditional doctor blade powder spreading, thus improving the quality of heterogeneous material printed parts. Furthermore, this invention achieves automatic replacement of the powder delivery needle 14 and variable adjustment of the electrostatic powder spreading electric field strength, improving processing efficiency while ensuring higher powder spreading accuracy. Therefore, this invention realizes a novel heterogeneous material powder spreading method combining ultrasonic powder dropping and electrostatic powder spreading, which is of great significance for upgrading the printing effect and optimizing the performance of heterogeneous material components.

[0091] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A laser additive manufacturing apparatus for heterogeneous material powder bed, characterized in that: include: The system includes a fixed-point powder suction ultrasonic powder delivery system, an electrostatic powder spreading system, and a powder bed additive manufacturing system, wherein the fixed-point powder suction ultrasonic powder delivery system and the electrostatic powder spreading system are both installed within the powder bed additive manufacturing system. The powder bed additive manufacturing molding system comprises an optical path system (1), a molding cavity (2), a molding cylinder (4), a powder cylinder (5), and a flexible scraper (16). The powder cylinder (5) is located at the bottom of the molding cavity (2) and is connected to the interior of the molding cavity (2). The molding cylinder (4) is located at the bottom of the molding cavity (2) and is connected to the interior of the molding cavity (2). The flexible scraper (16) is located at one end of the bottom of the molding cavity (2). The fixed-point suction ultrasonic powder delivery system consists of an ultrasonic transducer (7), multiple sets of powder delivery needles (14), a suction tube (8), and a needle frame (25). The powder delivery needles (14) are hung on the needle frame (25), and the needle frame (25) is located inside the forming cavity (2). One set of powder delivery needles (14) can be detachably installed inside the ultrasonic transducer (7). The electrostatic powder spreading system includes an electrostatic powder spreading mechanism and a powder spreading cart (15). The powder spreading cart (15) is horizontally movable inside the forming cavity (2), and the electrostatic powder spreading mechanism is located at the bottom of the powder spreading cart (15). The electrostatic powder spreading mechanism is located above the powder cylinder (5) and the powder recovery cylinder (3).

2. The heterogeneous material powder bed laser additive manufacturing apparatus according to claim 1, characterized in that: A lead screw slide (11) is provided on one side of the molding cavity (2). A double-rod cylinder (12) is connected to the molding cavity (2) via the lead screw slide (11). An internal support gripper (13) is provided on the movable end of the double-rod cylinder (12). The needle holder (25) is located at the bottom of the lead screw slide (11), and a placement hole for placing the powder feeding needle (14) is provided on the needle holder (25). The internal support gripper (13) is vertically aligned with the placement hole.

3. The heterogeneous material powder bed laser additive manufacturing apparatus according to claim 2, characterized in that: The powder delivery needle tube (14) is composed of a coarse-diameter powder delivery needle tube A (28), a fine-diameter powder delivery needle tube A (29), a coarse-diameter powder delivery needle tube B (30), and a fine-diameter powder delivery needle tube B (31), and the coarse-diameter powder delivery needle tube A (28), the fine-diameter powder delivery needle tube A (29), the coarse-diameter powder delivery needle tube B (30), and the fine-diameter powder delivery needle tube B (31) are all hung on the needle tube rack (25).

4. The heterogeneous material powder bed laser additive manufacturing apparatus according to claim 3, characterized in that: The ultrasonic transducer (7) consists of a front cover plate, a rear cover plate, a piezoelectric ceramic sheet, an electrode sheet, and a hollow bolt. The powder delivery needle tube (14) is detachably installed inside the ultrasonic transducer (7).

5. The heterogeneous material powder bed laser additive manufacturing apparatus according to claim 4, characterized in that: A three-axis slide system (6) is provided on the upper end of one side of the molding cavity (2). The ultrasonic transducer (7) is connected to the three-axis slide system (6) for transmission. Thus, the ultrasonic transducer (7) is movably set inside the molding cavity (2) through the three-axis slide system (6). The powder suction tube (8) is set between the ultrasonic transducer (7) and the three-axis slide system (6). A push-pull electromagnet (10) is provided at the transmission end of the three-axis slide system (6). The push-pull electromagnet (10) is set close to the ultrasonic transducer (7) and is used to fix the powder feeding needle tube (14).

6. The heterogeneous material powder bed laser additive manufacturing apparatus according to claim 5, characterized in that: The electrostatic powder spreading mechanism consists of an upper electrode plate (22) and an insulating layer (23). The insulating layer (23) is located at the bottom of the upper electrode plate (22). The flexible scraper (16) is located on the outside of the powder spreading cart (15). A powder bed (21) is provided at the lower end of the forming cavity (2), and the insulating layer (23) is located above the powder bed (21). A high-voltage AC power supply (20) is electrically connected between the upper electrode plate (22) and the powder bed (21).

7. The heterogeneous material powder bed laser additive manufacturing apparatus according to claim 6, characterized in that: A powder spreading guide rail (9) is provided at the lower end of one side of the molding cavity (2). The powder spreading cart (15) is connected to the powder spreading guide rail (9) for transmission. Thus, the powder spreading cart (15) is horizontally positioned inside the molding cavity (2) through the powder spreading guide rail (9). A lead screw guide rail (24) is provided at the end of the powder spreading cart (15). The upper electrode plate (22) and the insulating layer (23) are both connected to the lead screw guide rail (24) for transmission. Thus, the upper electrode plate (22) and the insulating layer (23) are both moved up and down within the powder spreading cart (15) through the lead screw guide rail (24).

8. The heterogeneous material powder bed laser additive manufacturing apparatus according to claim 7, characterized in that: The optical path system (1) is located at the upper end of the forming cavity (2), and the optical path system (1) consists of a collimator, a scanning galvanometer, and a field lens.

9. A method for heterogeneous material powder bed laser additive manufacturing, employing the heterogeneous material powder bed laser additive manufacturing apparatus as described in claim 8, characterized in that: Includes the following steps: S1: Preparation Phase S11. Preparation of powder bed additive manufacturing system: Use 3D design software to establish a model of heterogeneous material parts; add support and slice the model data, and at the same time, the computer software generates corresponding powder suction and powder dropping paths according to the slice information and imports them into the powder bed additive manufacturing system; add the main material powder and the forming substrate (19) into the powder cylinder (5) and the forming cylinder (4) respectively, and level the forming substrate (19) to complete the preparation of the powder bed additive manufacturing system. S12. Preparation of the fixed-point suction ultrasonic powder delivery system: Calculate the amount of heterogeneous material and fill each powder delivery needle (14). Place each powder delivery needle (14) vertically on the needle holder (25) and inside the ultrasonic transducer (7). First, select a large-diameter needle for the powder delivery needle (14) inside the ultrasonic transducer (7). Then, energize the push-pull electromagnet (10) to clamp the powder delivery needle (14). Return the position of the screw slide (11) to zero. Return the coordinates of the three-axis slide system (6) to zero and check whether the ultrasonic generator and vacuum suction machine can operate normally. S13. Preparation of electrostatic powder spreading system: Return the powder spreading cart (15) and lead screw guide rail (24) to zero and connect the lines between the electrodes; S2: Powder application stage: S21. The powder bed additive manufacturing system is working and executing the slicing program. When it is necessary to print heterogeneous materials, after the flexible scraper (16) lays a layer of main material powder in the powder cylinder (5), the side motor shaft of the powder spreading carriage (15) drives the flexible scraper (16) to rotate to the vertically upward idle position. S22. Operation of the fixed-point powder suction ultrasonic powder delivery system: First, the vacuum powder suction machine is started, and the three-axis slide system (6) drives the powder suction tube (8) to move along the predetermined path program to suction powder, removing a layer of powder from the area where the material to be replaced; then the ultrasonic transducer (7) moves to the starting point of the area inside the powder that has been suctioned under the action of the three-axis slide, the ultrasonic generator is started, and then the ultrasonic transducer (7) moves along the designated path, using a large-diameter powder delivery needle to accurately drop powder to fill the non-edge area (26) of the powder that has been suctioned; after the powder is dropped, the ultrasonic generator is turned off, and the ultrasonic transducer (7) moves to the side of the needle holder (25) in front of the empty needle slot; S23. Needle removal: First, the double-rod cylinder (12) pushes out the inner support gripper (13), and then the lead screw slide moves down, so that the claw head of the inner support gripper (13) extends into the interior of the powder delivery needle tube (14) in the ultrasonic transducer (7). Then the inner support gripper (13) starts, the push-pull electromagnet (10) is de-energized, the lead screw slide moves up, the double-rod cylinder (12) retracts, the lead screw slide moves down, and finally the inner support gripper (13) closes, the lead screw slide (11) returns to zero, and the automatic replacement of the coarse diameter powder delivery needle tube is completed. S24. Replace the fine-diameter powder delivery needle and assemble it according to the reverse process of S23. After the needle is automatically replaced, the ultrasonic transducer (7) moves to the starting point of the edge area (27) where the powder has been removed, the ultrasonic generator starts, and the fine-diameter powder delivery needle accurately drops powder to fill the edge area (27) where the powder has been removed. After the powder is dropped, the ultrasonic generator is turned off. The three-dimensional coordinates of the three-axis slide are returned to zero. S25. Operation of the electrostatic powder spreading system: First, turn on the high-voltage AC power supply (20). An AC electric field with rapidly changing polarity will be formed between the upper electrode plate (22) and the powder bed (21). Start the powder spreading car (15) and move along the powder spreading guide rail (9). At the same time, the lead screw guide rail (24) drives the insulating layer (23) and the upper electrode plate (22) to move vertically. Adjust the electric field strength between the upper electrode plate (22) and the powder bed (21). When the upper electrode plate (22) passes the forming cylinder (4) and is located above the powder material, the powder will oscillate up and down under the AC electric field force, thus spreading the powder.

10. The method for laser additive manufacturing of heterogeneous material powder bed according to claim 9, characterized in that: In S25, the electric field strength E is set to a range of 200-2000V / mm. The electric field strength E is adjusted by the upper electrode plate (22) driven by the lead screw rail (24), and the electric field strength E satisfies E=U / d. Wherein, U is the AC voltage applied by the high-voltage AC power supply (20), E is the electric field strength between the upper electrode plate (22) and the upper surface of the powder in the molding cylinder (4), and d is the distance between the upper electrode plate (22) and the upper surface of the powder in the molding cylinder (4).

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