Laser powder bed melting additive manufacturing system and method based on ultrasonic vibration assistance

Abstract

The invention discloses a laser powder bed melting additive manufacturing system and method based on ultrasonic vibration assistance, and the system comprises a control device which is used for setting process parameters and a process route, generating a user input parameter instruction, and transmitting the user input parameter instruction to a motion control card; the mechanical device is used for controlling the lifting of the powder cylinder and the working cylinder through a driving device and controlling the cyclic operation of powder feeding and returning of the scraper; the laser device is used for completing laser cladding operation; the ultrasonic device is used for transmitting ultrasonic waves to a workpiece on the sintering disc through an ultrasonic concentrator and carrying out ultrasonic vibration assistance; the dust removal and passivation device is used for filtering micro powder generated in the laser cladding process, oxidizing the outer surface of the metal micro powder and passivating the metal micro powder; and the atmosphere device adopts argon as atmosphere gas. According to the method, ultrasonic vibration is achieved in the LPBF process, the defects of pores, incomplete fusion, unfavorable inclusions, cracks and the like in the traditional LPBF process are overcome, and a novel and effective technology is provided for additive manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a laser powder bed melting additive manufacturing system and method based on ultrasonic vibration assistance. Background Art

[0002] Additive manufacturing (AM), commonly known as three-dimensional (3D) printing, is a manufacturing technology that integrates computer-aided design, material processing and forming technology, and uses software and numerical control systems to stack special metal materials, non-metallic materials and medical biomaterials layer by layer in the form of extrusion, sintering, melting, photocuring, injection, etc. to produce physical objects. Additive manufacturing can quickly form complex / single parts of customized products in a shorter time and is more precise than traditional processes. Recently, additive manufacturing has rapidly developed to the point of manufacturing end-use parts for various functional applications (such as biomedicine, engineering, automotive and aerospace).

[0003] Laser powder bed fusion (LPBF) in the additive manufacturing technology of metal materials has attracted researchers. This 3D printing process is carried out using a selective laser melting (SLM) machine. This technology offers great advantages over traditional manufacturing routes. For example, it is possible to manufacture parts of complex shapes without further post-processing and with almost no geometric restrictions. The technology offers high material utilization, high flexibility and low production time. In recent years, LPBF has received increasing attention in the production of many types of metal parts, mainly including aluminum, titanium, stainless steel, super alloys, nickel and cobalt-chromium alloys.

[0004] In the current LPBF process, the defects of printed workpieces mainly include porosity, lack of fusion (LOF), unfavorable inclusions (such as unmelted particles) and cracks. The current solutions mainly focus on the following aspects:

[0005] (1) Powder properties: particle size, shape, additives, etc.

[0006] (2) Laser properties: laser power, scanning speed, shadow line spacing (scanning track spacing), layer thickness, and scanning strategy;

[0007] (3) Post-treatment: heat treatment process, such as tempering and hot isostatic pressing;

[0008] (4) Online detection: Through sensor feedback of information such as defect formation, size, shape and position, a closed-loop system of adaptive laser control is realized.

[0009] The current solutions cannot fundamentally solve the defects in the LPBF process. Summary of the invention

[0010] The purpose of the present invention is to provide a laser powder bed fusion additive manufacturing system and method based on ultrasonic vibration assistance. Ultrasonic vibration is realized by ultrasonic waves during the LPBF process to eliminate defects such as porosity, lack of fusion (LOF), unfavorable inclusions (such as unmelted particles) and cracks in the traditional LPBF process, thereby providing a novel and effective technology for additive manufacturing, which has important practical application value.

[0011] To achieve the above object, the present invention provides the following solutions:

[0012] A laser powder bed fusion additive manufacturing system based on ultrasonic vibration assistance, the system comprising:

[0013] The control device is used for human-machine interaction, setting process parameters and process routes, generating user input parameter instructions, and transmitting them to the motion control card, with the motion control card as the carrier for instruction exchange;

[0014] The mechanical device includes a drive device, a powder cylinder, a working cylinder, and a scraper. The motion control card transmits the received user input parameter instructions to the drive device, and controls the lifting and lowering of the powder cylinder and the working cylinder through the drive device, as well as the cyclic operation of the scraper to feed powder and return.

[0015] Laser device, the motion control card conveys the user input parameter instructions to the laser and galvanometer to complete the laser cladding operation;

[0016] Ultrasonic device, the motion control card conveys the user input parameter instructions to the ultrasonic generator, and transmits stable ultrasonic waves to the workpiece on the sintering disk through the ultrasonic concentrator to assist ultrasonic vibration;

[0017] The dust removal and passivation device filters the micro powder generated during the laser cladding process; the convection valve is installed to control the oxygen entering the dust removal chamber by controlling the valve switch of the convection valve, oxidizing the outer surface of the metal micro powder to form an oxide layer to passivate it;

[0018] The atmosphere device includes an argon gas source and pipelines, and uses argon as the atmosphere gas to exhaust the oxygen in the sintering chamber to a content below 1%. The atmosphere device, the sintering chamber, and the dust removal and passivation device are connected in sequence to form a closed loop.

[0019] Furthermore, the system also includes a cooling device, which is used to dissipate heat for the laser device.

[0020] Furthermore, the system also includes a monitoring device, which includes an oxygen content meter and a pressure sensor; the oxygen content meter is placed above the sintering chamber to monitor the oxygen content in the sintering chamber in real time and display the numerical value in the software interface of the control device; the pressure sensor is placed at the dust removal and passivation device to detect the flow direction of the gas in the sintering chamber.

[0021] Further, the control device includes a control panel and a processor, and the processor is installed with visualization software;

[0022] The process parameters include mechanical properties, laser properties and ultrasonic properties; the mechanical properties include the height and speed of the powder cylinder and the working cylinder rising and falling each time a printing operation is performed; the laser properties include laser power, type, spot size, and scanning parameters, and the scanning parameters include scanning strategy, scanning speed and scanning spacing; the ultrasonic properties include ultrasonic power, type and the time node for applying ultrasonic waves.

[0023] Furthermore, in the mechanical device:

[0024] The powder cylinder is located on the right side of the ultrasonic chamber. When working, the motion control card conveys the user input parameter instructions to the driving device corresponding to the powder cylinder to drive the powder cylinder to rise and fall;

[0025] The working cylinder is located on the left side of the ultrasonic chamber. When working, the motion control card conveys the user input parameter instructions to the driving device corresponding to the working cylinder to drive the working cylinder to move up and down;

[0026] The scraper is fixed on the back plate of the sintering chamber. When working, the motion control card transmits the received user input parameter instructions to the drive device corresponding to the scraper, drives the scraper to move left and right, and completes the powder application operation.

[0027] Furthermore, the laser device includes a laser, a voltage stabilizer, a galvanometer, and a field mirror; the laser is used to emit laser light; the voltage stabilizer is used to stabilize the voltage for generating the laser light, eliminate voltage fluctuations, and protect the laser device; the galvanometer is used to execute a scanning strategy and run a laser motion trajectory; the field mirror is used to focus the laser beam onto a workpiece;

[0028] When the laser device is working, the motion control card transmits the parameter instructions input by the user to the control card of the galvanometer, and the control card of the galvanometer synchronously controls the laser to perform the laser cladding operation.

[0029] Furthermore, the ultrasonic device includes an ultrasonic generator and an ultrasonic concentrator, and the sintering disk is connected to the ultrasonic concentrator via threads.

[0030] Further, the dust removal and passivation device includes a dust removal device and a passivation device;

[0031] The dust removal device is equipped with a filter element to filter the fine powder generated during the laser cladding process;

[0032] During processing, the inlet and outlet of the dust removal device and the sintering chamber form a closed air circulation loop, which transports the generated metal powder into the dust removal device and adsorbs it on the filter element;

[0033] The passivation device oxidizes the outer surface of the metal powder to form an oxide layer to passivate it;

[0034] After the processing is completed, press the sintering chamber door button, and the ball valves installed at both ends of the dust removal device are closed to isolate the dust removal device from the air in the sintering chamber; control the opening and closing time of the convection valve to allow the argon gas and air in the dust removal chamber to convect, and the metal micropowder undergoes oxidation reaction to passivate the metal micropowder and eliminate its surface activity.

[0035] The present invention also provides a method for laser powder bed fusion additive manufacturing based on ultrasonic vibration assistance, which is applied to the above-mentioned laser powder bed fusion additive manufacturing system based on ultrasonic vibration assistance, and comprises the following steps:

[0036] S1, power on: close the main power switch and the power switches of each device;

[0037] S2, turn on the laser device: close the switch behind the laser stabilizer and turn on the cooling device to dissipate heat for the laser device;

[0038] S3, turn on the ultrasonic device: close the switch behind the ultrasonic generator;

[0039] S4, turn on the dust removal device: close the dust removal device switch;

[0040] S5, open the atmosphere device: open the argon gas bottle control valve, and inject argon gas into the sintering chamber until the oxygen content in the sintering chamber is less than 1%;

[0041] S6, power on and parameter input: turn on the control device and start the working software, including oxygen content monitoring software, laser software and process parameter control software, among which:

[0042] 1) Oxygen content monitoring software: used to monitor the oxygen content in the sintering chamber in real time, and formal processing will begin when it is less than 1%;

[0043] 2) Laser software: configure the IP address of the laser and enable operation;

[0044] 3) Process parameter control software, the specific parameter properties are as follows:

[0045] a. Printing workpiece attribute parameters: number of cycle printing layers, single layer thickness;

[0046] b. Powder spreading process: the rising height of the powder cylinder in a single print, and the descending height of the working cylinder in a single print;

[0047] c. Ultrasonic process: select the type, including pulse and continuous; select the time node for applying ultrasonic waves, including ultrasonic vibration after powder laying and ultrasonic vibration during laser cladding;

[0048] d. Laser scanning process: setting laser power, type, spot size, and scanning parameters, including scanning strategy, scanning speed, and scanning spacing;

[0049] S7, after setting the parameters, you can perform the additive manufacturing printing operation.

[0050] Furthermore, the method further comprises:

[0051] Self-protection mechanism: When the system is abnormal or in a fault state, the system will automatically pause; the printing operation can be continued only after the alarm fault is manually cleared; the abnormal or fault state includes: the powder cylinder does not perform the rising action, the working cylinder does not perform the descending action, or the scraper does not perform the powder application action in a certain cycle.

[0052] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0053] (1) The ultrasonic vibration-assisted laser powder bed melting additive manufacturing system provided by the present invention is based on the laser powder bed cladding (LPBF) process device, and an ultrasonic device is added to transmit stable ultrasonic waves to the workpiece on the sintering disk, so as to realize ultrasonic vibration after powder spreading, compact the powder in the working cylinder, reduce the powder porosity, and increase the powder space density. It can also realize ultrasonic vibration during the laser cladding process, and use low-amplitude high-frequency ultrasonic waves to enhance the metal-to-metal bonding force after the liquid metal in the molten pool solidifies, thereby eliminating defects such as pores, lack of fusion (LOF), unfavorable inclusions (such as unmelted particles) and cracks in the traditional LPBF process;

[0054] (2) The present invention integrates a control device, a mechanical device, a laser device, an ultrasonic device, a dust removal and passivation device to achieve comprehensive process control, and a monitoring device is provided to achieve real-time monitoring of the oxygen content in the sintering chamber and detect the flow direction of the gas in the sintering chamber to prevent gas backflow; the intelligent control level of the present invention is significantly improved. The present invention provides a novel and effective means for improving the process level of laser powder bed cladding additive manufacturing, and has important practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0056] Figure 1 It is a schematic structural diagram of the laser powder bed fusion additive manufacturing system based on ultrasonic vibration assistance of the present invention;

[0057] Explanation of the reference numerals: 1. control device; 2. motion control card; 3-1 and 4-1, driver; 3-2 and 4-2, motor; 5. working cylinder; 6. powder cylinder; 7. ultrasonic concentrator; 8. metal powder; 9. ultrasonic generator; 10. powder collecting bucket; 11. workpiece; 12. oxygen content meter; 13. field mirror; 14. galvanometer; 15. laser; 16. cooling device; 17. dust removal and passivation device; 18. pressure sensor; 19. argon gas bottle; 20. sintering chamber. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The purpose of the present invention is to provide a laser powder bed fusion additive manufacturing system and method based on ultrasonic vibration assistance. By adding ultrasonic vibration during the process, the purpose of eliminating defects is achieved, which provides a novel and effective means for improving the level of laser powder bed cladding additive manufacturing process and has important practical application value.

[0060] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0061] like Figure 1 As shown, the laser powder bed melting additive manufacturing system based on ultrasonic vibration assistance provided by the present invention includes:

[0062] The control device 1 is used for human-machine interaction, setting process parameters and process routes, generating user input parameter instructions, and transmitting them to the motion control card 2, with the motion control card 2 as the carrier for instruction exchange;

[0063] The mechanical device includes a driving device, a powder cylinder 6, a working cylinder 5, and a scraper. The motion control card 2 transmits the received user input parameter command to the driving device, and controls the lifting and lowering of the powder cylinder 6 and the working cylinder 5 through the driving device, as well as the cyclic operation of the scraper feeding and returning powder. For example, the driving device includes a driver and a motor;

[0064] Laser device, the motion control card 2 conveys the user input parameter instructions to the laser 15 and the galvanometer 14 to complete the laser cladding operation;

[0065] Ultrasonic device, the motion control card 2 conveys the user input parameter command to the ultrasonic generator 9, and transmits stable ultrasonic waves to the workpiece 11 on the sintering disk through the ultrasonic concentrator 7 to assist ultrasonic vibration;

[0066] The dust removal and passivation device 17 filters the micro powder generated during the laser cladding process; installs a convection valve to control the oxygen entering the dust removal chamber by controlling the valve switch of the convection valve, oxidizes the outer surface of the metal micro powder to form an oxide layer, and passivates it;

[0067] The atmosphere device includes an argon gas source and pipelines, and uses argon gas as the atmosphere gas to exhaust the oxygen in the sintering chamber to a content of less than 1%; the atmosphere device, the sintering chamber 20 and the dust removal and passivation device 17 are connected in sequence to form a closed loop; for example, an argon gas bottle 19 is used as the argon gas source;

[0068] A cooling device 16, the cooling device 16 is used to dissipate heat for the laser device; for example, a water-cooled radiator may be used;

[0069] The monitoring device includes an oxygen content meter 12 and a pressure sensor 18; the oxygen content meter 12 is placed above the sintering chamber to monitor the oxygen content in the sintering chamber in real time and display the value on the software interface of the control device; the pressure sensor 18 is placed at the dust removal and passivation device to detect the flow direction of the gas in the sintering chamber 20 to prevent the gas from flowing back.

[0070] Specifically, the specific structure and working principle of each device in the system are introduced as follows:

[0071] 1. Control device 1: The software is used for specific programming to realize the visualization of process route selection, and the user's parameters are passed to the motion control card, which is used as the carrier of instruction exchange. The control device 1 includes a processor and a control panel. For example, the control device 1 can be a computer.

[0072] Set process parameters and process routes, including input and selection of process parameters and process routes. The process parameters mainly include the following parameters:

[0073] (1) Mechanical properties: parameters such as the height and speed of the rise and fall of the powder cylinder 6 and the working cylinder 5 each time they perform a printing operation;

[0074] (2) Laser properties: laser power, type (pulse or continuous wave (CW)), spot size, scanning parameters, including scanning strategy, scanning speed, and scanning spacing. Scanning strategies include: single directional scanning, bidirectional / zigzag scanning, 45-degree linear scanning, island scanning, inner / outer spiral scanning, 90° rotation scanning between layers, etc. The scanning strategy can be innovated and optimized according to the actual effect of the printed workpiece;

[0075] (3) Ultrasonic properties: The ultrasonic power (adjusting amplitude) and type (pulse or continuous wave) of the ultrasonic device can be selected to apply ultrasound in any process. For example, after spreading the powder, the original powder is compacted with ultrasound to reduce the gaps between the powders. During the laser cladding process, ultrasonic vibrations are used to enhance the metal-to-metal bonding force after the liquid metal in the molten pool solidifies by using low-amplitude and high-frequency ultrasound, eliminating defects such as porosity, lack of fusion (LOF), unfavorable inclusions (such as unmelted particles) and cracks in the traditional LPBF process.

[0076] 2. Mechanical device: The motion control card 2 transmits the received user input parameter command to the driver to realize the operation of the powder cylinder 6 rising, the working cylinder 5 falling, the scraper feeding powder and returning cycle, etc.

[0077] (1) Powder cylinder 6: located on the right side of the ultrasonic chamber. When working, the motion control card 2 transmits the received user input parameter command to the driver 4-1, and the driver 4-1 drives the motor 4-2 to realize the lifting and lowering control of the powder cylinder 6;

[0078] (2) Working cylinder 5: located on the left side of the ultrasonic chamber. When working, the motion control card 2 transmits the received user input parameter instructions to the driver 3-1, and the driver 3-1 drives the motor 3-2 to realize the lifting control of the working cylinder 5;

[0079] (3) Scraper: fixed on the back plate of the sintering chamber 20. When working, the motion control card 2 transmits the received user input parameter command to the driver corresponding to the scraper, drives the scraper to move left and right, and completes the powder application operation.

[0080] 3. Laser device: The motion control card 2 transmits the received user input parameter instructions to the laser 15 and the galvanometer 14 to complete the laser cladding operation.

[0081] The laser device includes a laser 15, a voltage stabilizer, a galvanometer 14, a field lens 13, etc.:

[0082] (1) Laser 15: emits laser light;

[0083] (2) Voltage stabilizer: stabilizes the voltage that generates the laser, eliminates voltage fluctuations, and protects the laser device;

[0084] (3) Galvanometer 14: executes scanning strategy and runs laser motion trajectory;

[0085] (4) Field lens 13: focuses the laser beam.

[0086] During operation, the motion control card 2 receives an execution signal and transmits it to the control card of the galvanometer 14 . The control card of the galvanometer 14 synchronously controls the laser to perform the laser cladding operation.

[0087] 4. Ultrasonic device: The motion control card 2 transmits the received user input parameter instructions to the ultrasonic generator 9, and transmits stable ultrasonic waves to the workpiece on the sintering disk through the ultrasonic concentrator 7.

[0088] The ultrasonic device is composed of an ultrasonic generator 9 and an ultrasonic concentrator 7 (transducer + horn), and the sintered disk is connected to the ultrasonic concentrator 7 by threads.

[0089] During operation, the motion control card 2 receives an execution signal, controls the relay, and closes the ultrasonic device in a manner of controlling strong electricity with weak electricity, and the ultrasonic signal is transmitted to the workpiece 11 through the sintering disk.

[0090] 5. Dust removal and passivation device 17: Filter the micro powder generated during the laser cladding process to prevent dust from overflowing. Install an air (oxygen) convection valve to control the air (oxygen) entering the dust removal room by controlling the valve switch, oxidize the outer surface of the highly active metal micro powder to form an oxide layer to passivate it, prevent the micro powder body from contacting with excessive oxygen after laser sintering, and eliminate safety hazards.

[0091] (1) Dust removal: The dust removal device is equipped with a filter element to filter the fine powder generated during the laser cladding process to prevent dust from overflowing.

[0092] During processing, the inlet and outlet of the dust removal system and the sintering chamber form a closed air circulation loop, which transports the generated metal powder to the dust removal device and adsorbs it on the filter element. Pay attention to regularly replace the filter element in the dust removal device.

[0093] (2) Passivation: The outer surface of the highly active metal micropowder produced after sintering is oxidized to form an oxide layer to passivate it, thereby preventing the micropowder from coming into contact with excessive oxygen after laser sintering, which could pose a safety hazard.

[0094] 1) After the processing is completed, press the sintering chamber door button, and the ball valves installed at both ends of the dust removal device will be closed, isolating the dust removal device from the air in the sintering chamber 20 to ensure system safety.

[0095] 2) The opening and closing time of the convection valve (or airflow exchange valve) is controlled by the program to make the argon gas and air in the dust removal chamber convection. The specific principle is: the convection valve is opened for 5 seconds, the argon gas and air in the dust removal chamber convection, a small amount of air (oxygen) will enter the cavity, and then the valve is closed for 30 seconds to make the metal powder fully oxidized, passivate the metal powder, and eliminate the surface activity of the metal powder. The valve is opened and closed repeatedly, and finally all the powder in the dust removal device is passivated.

[0096] 6. Atmosphere device: In order to obtain better workpiece quality, argon is used as the atmosphere gas to exhaust the air in the sintering chamber to less than 1%.

[0097] The atmosphere device, sintering chamber and dust removal device form a closed loop. When the atmosphere device is turned on, argon gas is filled into the sintering chamber, and the excess air is pumped out of the closed loop by a pump.

[0098] 7. Cooling device 16: During the laser cladding process, the laser power is relatively high and will generate a large amount of heat. Water cooling is used to reduce the heat and ensure processing stability.

[0099] For example, the cooling device 16 can be a water-cooled radiator, which forms a closed pipeline with the heat generating part of the laser, and uses pure water as a fluid medium for heat dissipation. When working, the water in the pipeline circulates rapidly to take away the heat.

[0100] 8. Monitoring device: A real-time monitoring device for oxygen content is placed in the sintering chamber, and the value is displayed on the software interface to ensure the quality of printed workpieces; a pressure sensor 18 is placed in the air duct to detect the flow direction of gas in the sintering chamber to prevent gas backflow.

[0101] (1) Oxygen content meter 12: placed above the sintering chamber 20, monitors the oxygen content in the sintering chamber in real time, and displays the value on the software interface to ensure the quality of the printed workpiece.

[0102] (2) Pressure sensor 18: placed at the dust removal device to detect the flow direction of gas in the sintering chamber and prevent gas backflow.

[0103] In addition, the system also has a protection mechanism function: when the system is abnormal or fails, such as the powder cylinder does not perform the rising action, the working cylinder does not perform the descending action, or the scraper does not perform the powder application action in a certain cycle, the system will automatically pause. The printing operation can only be continued after the alarm fault is manually cleared.

[0104] The present invention also provides a method for laser powder bed fusion additive manufacturing based on ultrasonic vibration assistance, which is applied to the above-mentioned laser powder bed fusion additive manufacturing system based on ultrasonic vibration assistance, and comprises the following steps:

[0105] S1, power on: close the main power switch and the power switches of each device;

[0106] S2, turn on the laser device: close the switch behind the laser voltage stabilizer, and turn on the cooling device to dissipate heat for the laser device. Check whether the water level in the water-cooled radiator is at a safe level, and turn on the water cooling after confirmation;

[0107] S3, turn on the ultrasonic device: close the switch behind the ultrasonic generator;

[0108] S4, turn on the dust removal device: close the dust removal device switch;

[0109] S5, open the atmosphere device: open the argon gas bottle control valve, and inject argon gas into the sintering chamber until the oxygen content in the sintering chamber is less than 1%;

[0110] S6, power on and parameter input: turn on the control device and start the working software, including oxygen content monitoring software, laser software and process parameter control software; where:

[0111] 1) Oxygen content monitoring software: used to monitor the oxygen content in the sintering chamber in real time, and formal processing will begin when it is less than 1%;

[0112] 2) Laser software: configure the IP address of the laser and enable operation;

[0113] 3) Process parameter control software, the specific parameter properties are as follows:

[0114] a. Printing workpiece attribute parameters: number of cycle printing layers, single layer thickness;

[0115] b. Powder spreading process: the rising height of the powder cylinder in a single print, and the descending height of the working cylinder in a single print;

[0116] c. Ultrasonic process: select the type, including pulse and continuous; select the time node for applying ultrasonic waves, including ultrasonic vibration after powder laying and ultrasonic vibration during laser cladding;

[0117] d. Laser scanning process: setting laser power, type, spot size, and scanning parameters, including scanning strategy, scanning speed, and scanning spacing;

[0118] S7, after setting the parameters, you can perform the additive manufacturing printing operation.

[0119] The step c. ultrasonic process specifically embodies the following innovative process points:

[0120] (1) Ultrasonic vibration after powder spreading: compact the powder in the working cylinder, reduce the porosity of the powder, and increase the spatial density of the powder;

[0121] (2) Ultrasonic vibration during laser cladding: Low-amplitude, high-frequency ultrasonic waves are used to enhance the metal-metal bonding force after the liquid metal in the molten pool solidifies, eliminating defects such as porosity, lack of fusion (LOF), unfavorable inclusions (e.g., unmelted particles), and cracks in the traditional LPBF process.

[0122] The method also includes a self-protection mechanism: when the system is in an abnormal or faulty state, the system will automatically pause; the printing operation can be continued only after the alarm fault is manually cleared; wherein the abnormal or faulty state includes: in a certain cycle, the powder cylinder does not perform an ascending action, the working cylinder does not perform a descending action, or the scraper does not perform a powdering action.

[0123] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A laser powder bed fusion additive manufacturing system based on ultrasonic vibration assistance, characterized in that: include: The control device is used for human-machine interaction, setting process parameters and process routes, generating user input parameter instructions, and transmitting them to the motion control card, with the motion control card as the carrier for instruction exchange; The mechanical device includes a drive device, a powder cylinder, a working cylinder, and a scraper. The motion control card transmits the received user input parameter instructions to the drive device, and controls the lifting and lowering of the powder cylinder and the working cylinder through the drive device, as well as the cyclic operation of the scraper to feed powder and return. Laser device, the motion control card conveys the user input parameter instructions to the laser and galvanometer to complete the laser cladding operation; Ultrasonic device, the motion control card conveys the user input parameter instructions to the ultrasonic generator, and transmits the ultrasonic wave to the workpiece on the sintering disk through the ultrasonic concentrator to assist the ultrasonic vibration; The dust removal and passivation device filters the micro powder generated during the laser cladding process; the convection valve is installed to control the oxygen entering the dust removal chamber by controlling the valve switch of the convection valve, oxidizing the outer surface of the metal micro powder to form an oxide layer to passivate it; An atmosphere device, including an argon gas source and pipelines, uses argon as the atmosphere gas to exhaust the oxygen in the sintering chamber to a content below 1%; The atmosphere device, sintering chamber and dust removal and passivation device are connected in sequence to form a closed circuit.

2. The ultrasonic vibration-assisted laser powder bed fusion additive manufacturing system according to claim 1 is characterized in that: The system further comprises a cooling device, which is used for dissipating heat for the laser device.

3. The ultrasonic vibration-assisted laser powder bed fusion additive manufacturing system according to claim 1 is characterized in that: The system also includes a monitoring device, which includes an oxygen content meter and a pressure sensor; the oxygen content meter is placed above the sintering chamber to monitor the oxygen content in the sintering chamber in real time and display the value in the software interface of the control device; the pressure sensor is placed at the dust removal and passivation device to detect the flow direction of the gas in the sintering chamber.

4. The ultrasonic vibration-assisted laser powder bed fusion additive manufacturing system according to claim 1 is characterized in that: The control device includes a control panel and a processor, and the processor is installed with visualization software; The process parameters include mechanical properties, laser properties and ultrasonic properties; the mechanical properties include the height and speed of the powder cylinder and the working cylinder rising and falling each time a printing operation is performed; the laser properties include laser power, type, spot size, and scanning parameters, and the scanning parameters include scanning strategy, scanning speed and scanning spacing; the ultrasonic properties include ultrasonic power, type and the time node for applying ultrasonic waves.

5. The ultrasonic vibration-assisted laser powder bed fusion additive manufacturing system according to claim 1 is characterized in that: In the mechanical device: The powder cylinder is located on the right side of the ultrasonic chamber. When working, the motion control card conveys the user input parameter instructions to the driving device corresponding to the powder cylinder to drive the powder cylinder to rise and fall; The working cylinder is located on the left side of the ultrasonic chamber. When working, the motion control card conveys the user input parameter instructions to the driving device corresponding to the working cylinder to drive the working cylinder to move up and down; The scraper is fixed on the back plate of the sintering chamber. When working, the motion control card transmits the received user input parameter instructions to the drive device corresponding to the scraper, drives the scraper to move left and right, and completes the powder application operation.

6. The ultrasonic vibration-assisted laser powder bed fusion additive manufacturing system according to claim 1, characterized in that: The laser device includes a laser, a voltage stabilizer, a galvanometer, and a field mirror; the laser is used to emit laser light; the voltage stabilizer is used to stabilize the voltage for generating the laser light, eliminate voltage fluctuations, and protect the laser device; the galvanometer is used to execute a scanning strategy and run the laser motion trajectory; the field mirror is used to focus the laser beam onto a workpiece; When the laser device is working, the motion control card transmits the parameter instructions input by the user to the control card of the galvanometer, and the control card of the galvanometer synchronously controls the laser to perform the laser cladding operation.

7. The ultrasonic vibration-assisted laser powder bed fusion additive manufacturing system according to claim 1, characterized in that: The ultrasonic device comprises an ultrasonic generator and an ultrasonic concentrator, and the sintering disk is connected to the ultrasonic concentrator via threads.

8. The ultrasonic vibration-assisted laser powder bed fusion additive manufacturing system according to claim 1, characterized in that: The dust removal and passivation device comprises a dust removal device and a passivation device; The dust removal device is equipped with a filter element to filter the fine powder generated during the laser cladding process; During processing, the inlet and outlet of the dust removal device and the sintering chamber form a closed air circulation loop, which transports the generated metal powder into the dust removal device and adsorbs it on the filter element; The passivation device oxidizes the outer surface of the metal powder to form an oxide layer to passivate it; After the processing is completed, press the sintering chamber door button, and the ball valves installed at both ends of the dust removal device are closed to isolate the dust removal device from the air in the sintering chamber; control the opening and closing time of the convection valve to allow the argon gas and air in the dust removal chamber to convect, and the metal micropowder undergoes oxidation reaction to passivate the metal micropowder and eliminate its surface activity.

9. A method for additive manufacturing by laser powder bed fusion assisted by ultrasonic vibration, applied to the laser powder bed fusion additive manufacturing system assisted by ultrasonic vibration according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, power on: close the main power switch and the power switches of each device; S2, turn on the laser device: close the switch behind the laser stabilizer and turn on the cooling device to dissipate heat for the laser device; S3, turn on the ultrasonic device: close the switch behind the ultrasonic generator; S4, turn on the dust removal device: close the dust removal device switch; S5, open the atmosphere device: open the argon gas bottle control valve, and inject argon gas into the sintering chamber until the oxygen content in the sintering chamber is less than 1%; S6, power on and parameter input: turn on the control device and start the working software, including oxygen content monitoring software, laser software and process parameter control software, among which: 1) Oxygen content monitoring software: used to monitor the oxygen content in the sintering chamber in real time, and formal processing will begin when it is less than 1%; 2) Laser software: configure the IP address of the laser and enable operation; 3) Process parameter control software, the specific parameter properties are as follows: a. Printing workpiece attribute parameters: number of cycle printing layers, single layer thickness; b. Powder spreading process: the rising height of the powder cylinder in a single print, and the descending height of the working cylinder in a single print; c. Ultrasonic process: select the type, including pulse and continuous; select the time node for applying ultrasonic waves, including ultrasonic vibration after powder laying and ultrasonic vibration during laser cladding; d. Laser scanning process: setting laser power, type, spot size, and scanning parameters, including scanning strategy, scanning speed, and scanning spacing; S7, after setting the parameters, you can perform the additive manufacturing printing operation.

10. The method for laser powder bed melting additive manufacturing based on ultrasonic vibration assistance according to claim 9, characterized in that: The method further comprises: Self-protection mechanism: When the system is abnormal or in a fault state, the system will automatically pause; the printing operation can be continued only after the alarm fault is manually cleared; the abnormal or fault state includes: the powder cylinder does not perform the rising action, the working cylinder does not perform the descending action, or the scraper does not perform the powder application action in a certain cycle.

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