Print environment maintenance system and method

Abstract

The embodiment of the present application provides a printing environment maintaining system and method, the printing environment maintaining system comprises a forming chamber, a gas monitoring device, a gas extraction device, a gas feeding device and a control device; the gas monitoring device is arranged in the forming chamber; the gas extraction device is communicated with the forming chamber and extracts the gas in the forming chamber when working; the gas feeding device is communicated with the forming chamber and feeds the inert gas into the forming chamber when working; the control device is connected with the gas monitoring device, the gas extraction device and the gas feeding device respectively; in the process of switching the forming chamber from an abnormal environment to a micro-positive pressure environment, the control device controls the gas extraction device and the gas feeding device to work cooperatively. In the scheme, the adverse effects of impurity gas on the forming quality are reduced, and the probability of the external gas penetrating into the forming chamber is reduced; meanwhile, the micro-positive pressure environment can also avoid the airflow disturbing the metal powder due to the excessively high pressure in the forming chamber, so that the quality of the printed part is ensured.

Description

Technical Field

[0001] This application relates to the field of metal additive manufacturing equipment technology, and in particular to a printing environment maintenance system and method. Background Technology

[0002] Metal 3D printing, especially technologies that use lasers or electron beams as energy sources (such as selective laser melting (SLM) and electron beam melting (EBM), is usually carried out in a protective atmosphere (such as high-purity argon or nitrogen) or a vacuum environment to prevent the metal material from being oxidized or nitrided by oxygen or nitrogen at high temperatures, thus ensuring the mechanical properties and forming quality of the printed parts.

[0003] In related technologies, when metal 3D printing equipment uses a closed chamber filled with protective gas, the oxygen content (O2) and water vapor content (H2O) in the chamber will gradually increase and fluctuate during the printing process due to powder feeding, powder spreading, micro-leakage of the chamber door seal, and release of gas adsorbed by the powder. It is difficult to maintain a stable and low level, which affects the quality of the printed parts. Summary of the Invention

[0004] This application provides a printing environment maintenance system and method to solve the technical problem that during the printing process, due to factors such as powder feeding, powder spreading, micro-leakage of the chamber door seal, and release of powder adsorbed gas, the oxygen content (O2) and water vapor content (H2O) in the chamber gradually increase and fluctuate, making it difficult to maintain them at a consistently low level, thus affecting the quality of the printed parts.

[0005] In a first aspect, embodiments of this application provide a printing environment maintenance system, including:

[0006] Molding chamber;

[0007] A gas monitoring device is installed in the molding chamber to monitor the gas pressure and concentration of impurity gas components inside the molding chamber;

[0008] An exhaust device is connected to the molding chamber and extracts the gas inside the molding chamber during operation;

[0009] An air supply device, connected to the molding chamber, supplies inert gas into the molding chamber during operation; and

[0010] A control device is connected to the gas monitoring device, the gas extraction device, and the gas delivery device, respectively. The control device controls the gas extraction device and the gas delivery device to work together according to the concentration of impurity gas components monitored by the gas monitoring device, and keeps the molding chamber in an inert gas atmosphere. The control device also adjusts the gas extraction volume of the gas extraction device and the gas delivery volume of the gas delivery device according to the gas pressure monitored by the gas monitoring device, and keeps the molding chamber in a slightly positive pressure environment.

[0011] In one embodiment, the evacuation device includes a rough evacuation unit and a high vacuum unit, which are respectively connected to the forming chamber. The rough evacuation unit can evacuate the forming chamber to a low vacuum, and the high vacuum unit can evacuate the forming chamber to a high vacuum or ultra-high vacuum.

[0012] In some embodiments, the gas monitoring device includes a residual gas analyzer, which is connected to the molding chamber via a gas sampling interface located in the molding chamber, for real-time monitoring of gas parameters within the molding chamber.

[0013] In some embodiments, the gas monitoring device further includes a switching valve group and a plurality of sampling tubes, each sampling tube having a connection end and a sampling end, the plurality of sampling tubes being disposed in the molding chamber, the plurality of connection ends being connected to the gas sampling interface, the switching valve group being disposed between the gas sampling interface and the plurality of connection ends for controlling the on / off state of the gas sampling interface and each of the connection ends, and the plurality of sampling ends being distributed at multiple points in the molding chamber.

[0014] In some embodiments, the gas supply device includes a gas source storage tank, a gas supply pipe, a mass flow controller, and a first pressure regulating valve. The gas supply pipe connects the gas source storage tank and the forming chamber. The mass flow controller and the first pressure regulating valve are located on the gas supply pipe and are arranged sequentially along the direction close to the forming chamber.

[0015] In some embodiments, the molding chamber is provided with a liquid-cooled jacket.

[0016] In some embodiments, the feedthrough interface of the molding chamber is provided with a magnetic fluid sealed feedthrough or a bellows feedthrough.

[0017] Secondly, this application also provides a printing environment maintenance method for use in the printing environment maintenance system as described in any of the preceding claims, the printing environment maintenance method comprising:

[0018] Control the operation of the air extraction and air supply devices of the printing environment maintenance system, and adjust the forming chamber of the printing environment maintenance system to be in an inert gas atmosphere and a slightly positive pressure environment;

[0019] The composition and concentration of impurity gas in the molding chamber are acquired in real time, and it is determined whether the concentration of the corresponding component of the impurity gas exceeds the preset concentration value.

[0020] If the concentration of the corresponding component of the impurity gas exceeds the preset concentration value, the gas supply device is controlled to deliver inert gas into the molding chamber, and the gas extraction device is controlled to extract the gas from the molding chamber until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, and the molding chamber is maintained in the micro-positive pressure environment.

[0021] In some embodiments, the step of controlling the gas supply device to deliver inert gas into the molding chamber and controlling the gas extraction device to extract gas from the molding chamber if the concentration of the corresponding component of the impurity gas exceeds the preset concentration value, until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, includes:

[0022] Obtain the concentration difference between the concentration of the corresponding component of the impurity gas and the preset concentration value, and determine whether the concentration difference is within the first interval;

[0023] If the difference between the concentration of the corresponding component of the impurity gas and the preset concentration value is in the first range, the gas delivery device is first controlled to increase the delivery flow rate of the inert gas until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, and the gas pressure in the molding chamber is obtained.

[0024] Determine whether the air pressure inside the molding chamber is within the set range of the slightly positive pressure environment;

[0025] If the air pressure in the molding chamber exceeds the set range of the micro-positive pressure environment, the air extraction device is controlled to extract the gas from the molding chamber until the air pressure in the molding chamber is within the set range of the micro-positive pressure environment.

[0026] In some embodiments, after the step of obtaining the concentration difference between the concentration of the corresponding component of the impurity gas and the preset concentration value, and determining whether the concentration difference is within a first interval, the method further includes:

[0027] If the concentration difference exceeds the first interval, the gas delivery device is controlled to inject inert gas at a first preset rate, and the gas extraction device is controlled to extract the gas in the molding chamber at a second preset rate, and the gas pressure in the molding chamber is obtained in real time.

[0028] Obtain the dynamic pressure range of the molding chamber and determine whether the air pressure inside the molding chamber is within the dynamic pressure range;

[0029] If the air pressure in the molding chamber is within the dynamic pressure range, the air supply device is controlled to run at the first preset rate and the air extraction device is controlled to run at the second preset rate for a preset time. Then, the concentration difference value is obtained again, and it is determined whether the concentration difference value is within the first interval.

[0030] In the printing environment maintenance system provided in this application embodiment, during the printing process, when the gas monitoring device detects fluctuations and increases in the concentration of impurity gas in the forming chamber, the motion parameters of the gas supply device and the gas extraction device can be adjusted. On the one hand, inert gas is supplied to the forming chamber through the gas supply device to dilute the concentration of impurity gas in the forming chamber, thereby rapidly reducing the concentration of impurity gas in the forming chamber and reducing the adverse effects of impurity gas on the forming quality.

[0031] On the other hand, by promptly removing gas from the forming chamber using an extraction device, impurity gases are discharged while maintaining a slightly positive pressure environment within the forming chamber. This reduces the total amount of impurity gases in the forming chamber, effectively preventing them from interfering with print quality; it also ensures the pressure within the forming chamber is slightly higher than the external environment, reducing the probability of external gases infiltrating the chamber; simultaneously, the slightly positive pressure environment prevents airflow disturbance of the metal powder due to excessive pressure, ensuring print quality. This allows for a dual closed-loop control strategy: a purity control loop and a pressure stabilization loop. The purity control loop flushes and dilutes impurities within the forming chamber, while the pressure stabilization loop pulls the pressure back to the preset slightly positive pressure environment, effectively reducing the adverse effects of impurity gases on print quality and improving print quality. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] Figure 1 This is a schematic diagram of the framework of a printing environment maintenance system in one embodiment of this application;

[0034] Figure 2 for Figure 1 Schematic diagram of the frame of the central air extraction device;

[0035] Figure 3 for Figure 1 Control flowchart of the printing environment maintenance system;

[0036] Figure 4 A flowchart of a first embodiment of the printing environment maintenance method provided in this application.

[0037] Figure label:

[0038] 1. Molding chamber; 11. Liquid-cooled interlayer; 12. Observation window; 13. Door;

[0039] 2. Gas monitoring device;

[0040] 3. Evacuation device; 31. Rough pump unit; 311. Rough pump pump; 312. Bypass valve; 313. First baffle valve; 32. High vacuum unit; 321. Molecular pump; 322. Second baffle valve; 33. Low vacuum gauge; 34. High vacuum gauge;

[0041] 4. Gas delivery device; 41. Gas source storage tank; 42. Mass flow controller; 43. First pressure regulating valve;

[0042] 5. Control device; 51. Core controller; 52. Human-machine interface;

[0043] 6. Powder spreader;

[0044] 7. Laser head;

[0045] 8. Emergency pressure relief valve.

[0046] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0047] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0048] In related technologies, metal 3D printing equipment typically employs a sealed chamber filled with protective gas to prevent the metal material from oxidizing or nitriding with oxygen, nitrogen, etc., at high temperatures, thus ensuring the mechanical properties and forming quality of the printed parts.

[0049] However, during the printing process, due to factors such as powder feeding, powder spreading, micro-leakage of the chamber door seal, and release of gas adsorbed by the powder, the oxygen content (O2) and water vapor content (H2O) in the chamber will gradually increase and fluctuate, making it difficult to maintain a stable and extremely low level (such as below 100ppm, or even 10ppm).

[0050] Fluctuations in the atmospheric environment directly affect the stability of the molten pool, which may lead to defects such as porosity, inclusions, and warping in the printed parts, especially significantly impacting the printing success rate of active metals such as titanium alloys and aluminum alloys.

[0051] Therefore, this application provides a printing environment maintenance system and method that can dilute the concentration of impurity gases in the forming chamber, reduce the total amount of impurity gases in the forming chamber, and ensure that the pressure in the forming chamber is slightly higher than that of the external environment, thereby reducing the probability of external gases infiltrating into the forming chamber. At the same time, it avoids the airflow disturbing the metal powder due to excessive pressure in the forming chamber, thus ensuring the quality of the printed parts.

[0052] Please see Figure 1 The printing environment maintenance system provided in this application includes a forming chamber 1, a gas monitoring device 2, an extraction device 3, an air supply device 4, and a control device 5. The gas monitoring device 2 is located in the forming chamber 1 and is used to monitor the gas pressure and concentration of impurity gas components in the forming chamber 1. The extraction device 3 is connected to the forming chamber 1 and extracts the gas in the forming chamber 1 during operation. The air supply device 4 is connected to the forming chamber 1 and supplies inert gas into the forming chamber 1 during operation. The control device 5 is connected to the gas monitoring device 2, the extraction device 3, and the air supply device 4 respectively. The control device 5 controls the extraction device 3 and the air supply device 4 to work together according to the gas component concentration monitored by the gas monitoring device 2, so that the forming chamber 1 is in an inert gas atmosphere. The control device 5 also adjusts the extraction volume of the extraction device 3 and the air supply volume of the air supply device 4 according to the gas pressure monitored by the gas monitoring device 2, so that the forming chamber 1 is maintained in a slightly positive pressure environment.

[0053] In this application, during the printing process, when the gas monitoring device 2 detects fluctuations and increases in the concentration of impurity gas in the molding chamber 1, it can adjust the motion parameters of the gas supply device 4 and the gas extraction device 3. On the one hand, inert gas is supplied to the molding chamber 1 through the gas supply device 4 to dilute the concentration of impurity gas in the molding chamber 1, thereby rapidly reducing the concentration of impurity gas in the molding chamber 1 and reducing the adverse effects of impurity gas on molding quality.

[0054] On the other hand, the gas in the forming chamber 1 is promptly extracted by the suction device 3. While removing impurity gas, the forming chamber 1 is also kept in a slightly positive pressure environment. This reduces the total amount of impurity gas in the forming chamber 1, effectively preventing it from interfering with print quality; it also ensures that the pressure inside the forming chamber 1 is slightly higher than the external environment, reducing the probability of external gas infiltration into the forming chamber 1; simultaneously, the slightly positive pressure environment also prevents airflow disturbance of the metal powder due to excessive pressure inside the forming chamber 1, ensuring print quality. This forms a dual closed-loop control strategy of purity control loop and pressure stabilization loop. The purity control loop flushes and dilutes impurities in the forming chamber 1, while the pressure stabilization loop pulls the pressure inside the forming chamber 1 back to the preset slightly positive pressure environment, effectively reducing the adverse effects of impurity gas on print quality and improving print quality.

[0055] It should be understood that the control device 5 can be a programmable logic controller (PLC) or an industrial computer. The control device 5 can be connected to the gas monitoring device 2, the gas extraction device 3, and the gas delivery device 4 by establishing a direct connection using physical cables (such as Ethernet cables, telephone lines, etc.) or by using wireless signals (such as Wi-Fi, Bluetooth, infrared, etc.) to achieve device interconnection.

[0056] In addition, the gas monitoring device 2 can at least monitor the gas pressure, gas composition, and concentration within the molding chamber 1. In this scheme, the control device 5 acquires the monitoring signal from the gas monitoring device 2 and controls the gas supply device 4 and the gas extraction device 3, involving three core stages: signal acquisition, processing, and execution control. The specific implementation method is as follows:

[0057] Signal Acquisition and Transmission: Sensor signal output. The gas monitoring device 2 detects the gas concentration using a sensor (such as an electrochemical sensor) and generates a weak electrical signal (such as a 4-20mA current signal or a 0-10V voltage signal) proportional to the concentration. Signal Conditioning and Conversion: The control module enhances the signal strength through an amplifier circuit, eliminates noise through a filter circuit, and then converts the analog signal into a digital signal via an analog-to-digital converter (ADC) for processing by an industrial computer. For example, using a 12-bit ADC (such as the AD574A) can improve measurement accuracy.

[0058] Communication Protocols and Data Transmission: The industrial computer needs to communicate with the gas monitoring device 2, gas supply device 4, and gas extraction device 3 via standardized protocols. For example, the Modbus protocol is used for data transmission between the PLC and the AI ​​system, supporting RS-485 or TCP / IP networks to achieve real-time interaction of device status and concentration values; the S7 protocol is a Siemens PLC-specific protocol that establishes connections through a hierarchical handshake mechanism, supporting reading and writing of I / O areas and data blocks, suitable for high-reliability scenarios; and functional safety communication, such as the IEC61784-3 standard, ensures reliable transmission of critical commands through redundancy checks and data integrity protection.

[0059] Execution control logic: The opening degree of the electrically controlled valve of the gas supply device 4 is adjusted by the industrial computer based on the gas concentration threshold, using PWM (Pulse Width Modulation) or analog output to control the solenoid valve opening; for example, when the concentration exceeds the standard, a 4-20mA signal is output to drive the solenoid valve to fully open; when the concentration is normal, the opening degree is adjusted proportionally to maintain flow balance. The capacity control of the gas extraction device 3 is achieved by adjusting the speed of the gas extraction pump through a frequency converter or servo system to change the extraction volume; for example, high-speed extraction is triggered when the gas concentration is high; the speed is reduced to save energy when the concentration is low.

[0060] It should be noted that in this solution, the control device 5 includes a core controller 51 (PLC) and a human-machine interface 52 (HMI). The core controller 51 is responsible for receiving and processing signals and outputting control commands to realize automation logic; it also processes continuously changing analog quantities such as temperature and pressure, and adjusts actuators (such as valves and frequency converters) through PID algorithms to stabilize parameters at set values; at the same time, it stores equipment status data and exchanges information with the HMI and SCADA systems through protocols such as Ethernet and Modbus.

[0061] The human-machine interface 52 serves as the medium for user interaction with the system, responsible for real-time monitoring, data input, and status feedback. It displays equipment operating parameters (such as temperature, pressure, and speed) and alarm information, and issues control commands, such as starting / stopping the equipment and adjusting parameters, through interfaces such as touch screens and buttons.

[0062] Furthermore, it should be understood that when the air supply volume of the air supply device 4 is greater than the air extraction volume of the air extraction device 3, the air pressure in the molding chamber 1 will gradually increase, and the concentration of impurity gas will be diluted. Conversely, when the air supply volume of the air supply device 4 is less than the air extraction volume of the air extraction device 3, the air pressure in the molding chamber 1 will gradually decrease, and the concentration of impurity gas will also be diluted.

[0063] In one embodiment, please refer to Figure 1 and Figure 2 The vacuum pumping device 3 includes a roughing pump unit 31 and a high vacuum unit 32. The roughing pump unit 31 and the high vacuum unit 32 are respectively connected to the forming chamber 1. The roughing pump unit 31 can pump the forming chamber 1 to a low vacuum, and the high vacuum unit 32 can pump the forming chamber 1 to a high vacuum or ultra-high vacuum.

[0064] In this embodiment, the roughing pump unit 31 can quickly pump the forming chamber 1 from atmospheric pressure to a low-to-medium vacuum range (e.g., 1 Pa); while the high-vacuum unit 32 can further increase the pressure to a high vacuum (e.g., 10 Pa). -3 ~10 -5 Pa), or ultra-high vacuum (10 Pa), or ultra-high vacuum (10 Pa). - 7 After the forming chamber 1 is in a preset vacuum environment, inert gas is introduced into the forming chamber 1 through the gas supply device 4, switching the forming chamber 1 to a slightly positive pressure inert gas atmosphere, thus completing the initial adjustment of the forming chamber 1. The high pumping speed of the roughing pump unit 31 significantly shortens the pumping time from atmospheric pressure to medium-low vacuum; while the high vacuum unit 32 maintains efficient pumping even at low pressure, avoiding overload of the high vacuum pump due to insufficient roughing, ensuring small vacuum fluctuations and high stability. The combination of these two systems covers the entire process from roughing to high vacuum, meeting different process requirements.

[0065] Furthermore, when the gas concentration in the forming chamber 1 fluctuates and increases, the initial evacuation can be completed by the rough evacuation unit 31, followed by the gradual intervention of the high vacuum unit 32. Through a multi-stage early warning mechanism and automatic adjustment program, a slightly positive pressure state is maintained. During this process, the gas supply device 4 supplies gas in conjunction with the process, delivering inert gas into the forming chamber 1.

[0066] It should be understood that the roughing pump 311 of the roughing unit 31 can be a dry screw pump or a rotary vane pump to evacuate the forming chamber 1 from atmospheric pressure to a low to medium vacuum range, such as 1 Pa to 1000 Pa. The vacuum pump of the high vacuum unit 32 can be a molecular pump 321 or a cryogenic pump to evacuate the forming chamber 1 to a high vacuum or ultra-high vacuum range, such as 10 Pa. -4 Pa~10 -7 Pa. Pneumatic baffle valves, solenoid valves, and bypass valves 312 are respectively installed on the connecting pipelines between the forming chamber 1 and the roughing pump unit 31 and the high vacuum unit 32 to control the pumping path and achieve automatic switching between the roughing and fine pumping pumps. Specifically, in this scheme, the roughing pump unit 31 includes a roughing pump 311, a bypass valve 312, and a first baffle valve 313. The high vacuum unit 32 includes a molecular pump 321 and a second baffle valve 322.

[0067] Furthermore, it should be understood that the forming chamber 1 is provided with an exhaust port for connecting the roughing pump unit 31 and the high vacuum unit 32, and a second pressure regulating valve is provided at the exhaust port. In addition, the forming chamber 1 is also equipped with a low vacuum gauge 33 and a high vacuum gauge 34 corresponding to the roughing pump unit 31 and the high vacuum unit 32, respectively. The low vacuum gauge 33 is a Pirani gauge or a capacitance diaphragm gauge used to monitor the pressure during the roughing vacuum stage. The high vacuum gauge 34 is a cold cathode ionizer or a hot cathode ionizer used to monitor the pressure during the high vacuum stage.

[0068] In one embodiment, the gas monitoring device 2 includes a residual gas analyzer, which is connected to the molding chamber 1 through a gas sampling interface located in the molding chamber 1, and is used to monitor the gas parameters in the molding chamber 1 in real time.

[0069] In this embodiment, the residual gas analyzer (RGA) not only measures the total pressure, but more importantly, it quantitatively analyzes the partial pressure (concentration) of each gas component. For example, it clearly distinguishes the oxygen ion peak and the water ion peak, and outputs their concentration values ​​in real time. Furthermore, the gas inside the forming chamber 1 is obtained through a gas sampling interface, rather than the entire residual gas analyzer being built into the forming chamber 1, thus avoiding damage to the residual gas analyzer from the environment inside the forming chamber 1 and extending its service life.

[0070] Specifically, the residual gas analyzer collects gas samples from the molding chamber 1 in real time and performs mass spectrometry analysis, outputting partial pressure data for oxygen, water vapor, nitrogen, or hydrogen. This data is transmitted to the control device 5 via a communication interface, serving as the basis for dynamically adjusting the operating parameters of the extraction device 3 and the gas delivery device 4. For example, when the RGA detects that the oxygen partial pressure exceeds a threshold, the control device 5 activates the extraction device 3 to extract oxygen gas and correspondingly activates the gas delivery device 4 to inject inert gas to dilute the oxygen concentration. The connectivity of the gas sampling interface ensures that the RGA can continuously acquire gas composition data within the molding chamber 1, forming a closed-loop control.

[0071] In one embodiment, the gas monitoring device 2 further includes a switching valve group and multiple sampling tubes. Each sampling tube has a connection end and a sampling end. The multiple sampling tubes are located in the molding chamber 1. The multiple connection ends are all connected to the gas sampling interface. The switching valve group is located between the gas sampling interface and the multiple connection ends and is used to control the on / off state of the gas sampling interface and each connection end. The multiple sampling ends are distributed at multiple points in the molding chamber 1.

[0072] In this implementation, the residual gas analyzer can acquire gas composition data from multiple locations within the forming chamber 1, enabling multi-point monitoring of the gas within the forming chamber 1 and real-time acquisition of gas composition data from different locations. This solution, through a multi-point RGA layout, significantly improves the comprehensiveness and response speed of impurity concentration monitoring. For example, a sampling tube is placed within the travel stroke of the powder feeding mechanism. When the powder feeding mechanism moves, the sampling tube at the corresponding location is activated to quickly detect whether the local water vapor concentration has increased, triggering the control device 5 to initiate a targeted purification strategy. This multi-point monitoring capability avoids the monitoring blind spots caused by the fixed location of traditional single-point RGAs, allowing the system to more accurately identify local fluctuations in impurity concentration and initiate targeted purification actions, thereby reducing the global environmental deterioration caused by the spread of local contamination and further improving print quality stability.

[0073] It should be understood that the switching valve assembly can be configured as an electrically controlled multi-way valve, or it can be configured to have an independent control valve on each sampling tube. Furthermore, the sampling tube is configured to avoid the laser head 7.

[0074] In one embodiment, the gas supply device 4 includes a gas source storage tank 41, a gas supply pipe, a mass flow controller 42, and a first pressure regulating valve 43. The gas supply pipe connects the gas source storage tank 41 and the molding chamber 1. The mass flow controller 42 and the first pressure regulating valve 43 are located on the gas supply pipe and are arranged sequentially in the direction close to the molding chamber 1.

[0075] In this embodiment, the mass flow controller 42 (MFC) is used to control the injection flow rate of the inert gas, and the first pressure regulating valve 43 is used to adjust the airflow resistance of the exhaust path of the molding chamber 1. When the control device 5 needs to maintain a slight positive pressure, the MFC injects inert gas at a set flow rate, while the first pressure regulating valve 43 balances the pressure of the molding chamber 1 by adjusting its opening. For example, in the flowing inert atmosphere mode, the MFC continuously injects gas at a low flow rate, and the first pressure regulating valve 43 maintains a slight positive pressure in the molding chamber 1 by a small opening, forming a slow gas flow to dilute impurities. When the RGA detects that the impurity concentration is severely exceeded, the MFC increases the flow rate and the first pressure regulating valve 43 is fully opened, and a brief evacuation-refill cycle is initiated.

[0076] MFC's precise flow control ensures that the gas injection volume only meets purification requirements, while the pressure regulating valve dynamically adjusts the exhaust resistance to avoid molten pool disturbance caused by continuous high-flow gas injection. For example, it maintains a low-flow injection under normal conditions, and only activates high-flow flushing and evacuation circulation when the impurity concentration is abnormal, thereby reducing the amount of high-purity gas used while ensuring print quality.

[0077] In one embodiment, the molding chamber 1 is provided with a liquid-cooled interlayer 11.

[0078] In this embodiment, a stainless steel or alloy material with a double-layer water-cooled sandwich structure is used. The inner layer of the molding chamber 1 is the printing cavity, and the outer layer is the water-cooled sandwich layer. They are fixed by flange connection to resist heat radiation and thermal deformation during the printing process, maintain the geometric stability of the cavity, and reduce the risk of deformation at the interface.

[0079] Furthermore, it should be noted that in this design, the molding chamber 1 has an observation window 12, which is a flange-connected sapphire or quartz glass window equipped with a metal sealing ring. The door 13 of the molding chamber 1 is a knife-edge or cam-locking quick-opening flange door, with a large metal sealing ring embedded, such as a copper gasket or an O-ring indium seal. Simultaneously, multiple standard CF flanges or KF flange interfaces are pre-fabricated on the wall of the molding chamber 1 for connecting the vacuum pump 3, vacuum measuring device, gas supply device 4, and emergency pressure relief valve 8.

[0080] In one embodiment, the feed interface of the molding chamber 1 is provided with a magnetic fluid sealed feed element or a bellows feed element.

[0081] In this embodiment, a magnetohydrodynamic seal or a bellows or other ultra-high vacuum feeder is used at the feeder interface to ensure the sealing performance within the forming chamber 1. In one embodiment, a magnetohydrodynamic seal is used instead of a traditional metal bellows or O-ring seal in the sealing design of moving parts such as the powder spreader 6 and the powder bed lifting mechanism within the forming chamber 1. The magnetohydrodynamic seal consists of a permanent magnet ring, a magnetohydrodynamic fluid (magnetic nanoparticle suspension), and a non-magnetic sealing shell. It forms a dynamic sealing interface by confining the magnetohydrodynamic fluid with a magnetic field, while allowing the moving parts to slide freely in a vacuum environment.

[0082] When moving parts (such as the powder spreader 6) move within the forming chamber 1, the magnetic fluid forms a stable sealing film under the influence of the strong magnetic field generated by the permanent magnet ring, filling the movement gaps and blocking gas leakage paths. Compared to traditional mechanical seals, magnetic fluid seals achieve sealing without physical contact, and the magnetic fluid has low volatility in a vacuum environment, avoiding micro-leakage caused by aging or wear of the sealing material. Furthermore, the structural design of the magnetic fluid seal, through optimized magnetic ring polarity arrangement and magnetic fluid filling thickness, can further enhance sealing strength and thermal stability.

[0083] This solution significantly improves the sealing performance of moving parts in a vacuum environment by leveraging the dynamic characteristics of magnetohydrodynamic (MHD) seals, reducing gas leakage caused by mechanical friction or seal aging. Combined with the double-layer water-cooled sandwich structure of the molding chamber 1 body, the impact of thermal deformation on sealing performance is effectively suppressed, thereby maintaining the long-term stability of oxygen, water vapor, and other impurity concentrations within the molding chamber 1. Simultaneously, the non-contact nature of MHD seals reduces mechanical wear on moving parts, extends equipment lifespan, and reduces the frequency of seal maintenance, further enhancing the system's reliability and economy.

[0084] In addition, please see Figure 3 and Figure 4 This application also provides a printing environment maintenance method for use in the printing environment maintenance system described above. A first embodiment of the printing environment maintenance method includes:

[0085] The air extraction device 3 and air supply device 4 of the printing environment maintenance system are controlled to work, and the forming chamber 1 of the printing environment maintenance system is adjusted to be in an inert gas atmosphere and a slightly positive pressure environment.

[0086] The composition and concentration of impurity gas in the molding chamber 1 are acquired in real time, and it is determined whether the concentration of the corresponding component of the impurity gas exceeds the preset concentration value.

[0087] If the concentration of the corresponding component of the impurity gas exceeds the preset concentration value, the gas supply device 4 is controlled to supply inert gas into the molding chamber 1, and the gas extraction device 3 is controlled to extract the gas from the molding chamber 1 until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, and the molding chamber 1 is maintained in a slightly positive pressure environment.

[0088] In this embodiment, when the printing device is in the flowing inert atmosphere printing mode, the forming chamber 1 is first evacuated to a low vacuum, then filled with protective gas to a pressure slightly higher than atmospheric pressure. The air intake of the MFC and the opening of the first pressure regulating valve 43 are then finely adjusted to maintain a slight positive pressure in the forming chamber 1, creating a slow gas flow that carries away impurities. When the RGA detects an increase in impurity content, the system automatically increases the air intake flow or starts the vacuum pump for a brief evacuation before refilling, achieving dynamic purification.

[0089] It should be understood that the coordinated action of gas monitoring device 2, extraction device 3, gas delivery device 4, and control device 5 solves the environmental instability problem caused by fluctuations in impurity gas concentration during the dynamic operation of the closed molding chamber 1. The real-time monitoring capability of gas monitoring device 2 enables the system to accurately identify changes in the concentration of harmful gas components (such as oxygen and water vapor), and dynamically adjust the operating parameters of extraction device 3 and gas delivery device 4 through control device 5 to achieve targeted purification and regulation.

[0090] Specifically, when an increase in water vapor concentration is detected, the control device 5 immediately increases the pumping rate of the extraction device 3 and adjusts the gas injection flow rate of the gas delivery device 4 to quickly dilute impurities and reduce the total amount of impurities. Simultaneously, the control device 5 continuously optimizes operating parameters through closed-loop logic to avoid control lag caused by environmental disturbances or process changes. The synergistic effect of these technologies significantly improves the purity and stability of the environment in the closed molding chamber 1, providing a crucial guarantee for high-precision printing of reactive metals, while reducing the risk of printing defects caused by fluctuations in impurity concentration.

[0091] Furthermore, it should be understood that in this plan, please refer to... Figure 3 The control device 5 has a dual closed-loop control loop consisting of an outer loop control loop and an inner loop control loop. The outer loop control loop adjusts the operating parameters of the extraction device 3 and the delivery device 4 based on the partial pressure data from the RGA; the inner loop control loop adjusts the gas injection flow rate of the delivery device 4 or the extraction rate of the extraction device 3 based on the pressure sensor output of the forming chamber 1. The outer loop is responsible for higher-order targets, such as impurity concentration; the inner loop is responsible for lower-order targets, such as pressure stability. The pressure sensor refers to a sensor that measures the absolute pressure of the forming chamber 1, such as a capacitive thin-film gauge or a piezoresistive pressure sensor.

[0092] The outer loop control circuit receives the partial pressure data from the RGA and determines whether a purification strategy needs to be activated based on a preset threshold, such as increasing the pumping rate or injecting inert gas. The inner loop control circuit receives the output from the pressure sensor and adjusts the gas injection flow rate of the gas supply device 4 or the pumping rate of the pumping device 3 through a PID algorithm to maintain the pressure in the forming chamber 1 within a set range. For example, when the RGA detects that the oxygen partial pressure exceeds the limit, the outer loop control circuit activates the pumping device 3, while the inner loop control circuit adjusts the pressure value fed back by the pressure sensor to ensure that the pressure in the forming chamber 1 does not fluctuate drastically during the pumping process.

[0093] This application also provides a second embodiment of the printing environment maintenance method. In the second embodiment of the printing environment maintenance method, the steps described above, such as controlling the gas supply device 4 to supply inert gas into the forming chamber 1 if the concentration of the corresponding component of the impurity gas exceeds a preset concentration value, and controlling the gas extraction device 3 to extract the gas from the forming chamber 1 until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, include:

[0094] Obtain the concentration difference between the concentration of the corresponding component of the impurity gas and the preset concentration value, and determine whether the concentration difference is within the first interval;

[0095] If the difference between the concentration of the corresponding component of the impurity gas and the preset concentration value is in the first range, the gas supply device 4 is first controlled to increase the inert gas delivery flow rate until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, and the gas pressure in the molding chamber 1 is obtained.

[0096] Determine whether the air pressure inside molding chamber 1 is within the set range of a slightly positive pressure environment;

[0097] If the air pressure in the molding chamber 1 exceeds the set range of the micro-positive pressure environment, the air extraction device 3 is controlled to extract the gas from the molding chamber 1 until the air pressure in the molding chamber 1 is within the set range of the micro-positive pressure environment.

[0098] This embodiment applies to dynamic equilibrium under normal fluctuations. In this scheme, the preset concentrations of relevant gas components are O2 < 5 ppm and H2O < 10 ppm. The set range of micro-positive pressure is that the static pressure difference between molding chamber 1 and the adjacent non-clean area should not be less than 0.1 kPa and not more than 0.3 kPa. The first range is a concentration difference of less than 20 ppm. Based on this, the specific process of dynamic equilibrium under normal fluctuations is as follows:

[0099] Initial state: Molding chamber 1 is in a slightly positive pressure mode with a flowing inert atmosphere, and the ambient pressure in the non-clean area is 101.325 kPa. Target: The pressure in molding chamber 1 is maintained at 101.5 kPa (slightly positive pressure), O2 < 5 ppm, and H2O < 10 ppm.

[0100] Incident occurred: Powder spreader 6 activated, and the agitated powder released a trace amount of adsorbed water vapor (H2O). RGA detected a slow increase in H2O partial pressure and a slow increase in concentration from 8 ppm to 12 ppm, exceeding the threshold of 10 ppm. The total pressure also increased slightly due to the release of a small amount of gas.

[0101] Control Response: Purity Control Loop (Outer Loop) Activation: After comparing the RGA data with the threshold, control device 5 determines that purification is required. Instead of immediately evacuating, it slightly increases the set flow rate of the MFC (e.g., from 5.0 sccm to 5.8 sccm) to flush and dilute impurities with a slightly faster inert gas inflow.

[0102] Pressure stabilization loop (inner loop) response: An increase in MFC flow causes the pressure in molding chamber 1 to rise (e.g., from 101.5 kPa to 101.7 kPa). The pressure sensor feeds this change back to control unit 5. Control unit 5 then calculates and increases the opening of the first pressure regulating valve 43 and increases the venting capacity, precisely pulling the pressure back to the set point of 101.5 kPa.

[0103] In this new equilibrium state, both the intake and exhaust volumes are greater than before, creating a relatively strong purification and displacement airflow, which carries away moisture from the forming chamber 1 more quickly. RGA monitoring showed that the H2O partial pressure gradually decreased, and the concentration dropped below 8 ppm. The system then restored the MFC flow rate and the opening of the first pressure regulating valve 43 to their normal values. Throughout the process, the pressure in forming chamber 1 remained stable, avoiding the potential impact of pressure fluctuations on the laser molten pool.

[0104] This application provides a third embodiment of a printing environment maintenance method. In this third embodiment, after the steps of obtaining the concentration difference between the concentration of the corresponding gas component and a preset concentration value, and determining whether the concentration difference is within a first interval, the method further includes:

[0105] If the concentration difference exceeds the first range, the gas supply device 4 is controlled to inject inert gas at the first preset rate, and the gas extraction device 3 is controlled to extract the gas in the molding chamber 1 at the second preset rate, and the gas pressure in the molding chamber 1 is obtained in real time.

[0106] Obtain the dynamic pressure range of molding chamber 1 and determine whether the air pressure in molding chamber 1 is within the dynamic pressure range;

[0107] If the air pressure in the molding chamber 1 is within the dynamic pressure range, the air supply device 4 is controlled to run at the first preset rate and the air extraction device 3 is controlled to run at the second preset rate for a preset time. Then, the concentration difference value is obtained again, and it is determined whether the concentration difference value is within the first interval.

[0108] This embodiment is applied to the powerful intervention of sudden pollution events. The specific process of this embodiment is as follows:

[0109] Initial state: Molding chamber 1 is in a slightly positive pressure mode with a flowing inert atmosphere, and the ambient pressure in the non-clean area is 101.325 kPa. Target: The pressure in molding chamber 1 is maintained at 101.5 kPa (slightly positive pressure), O2 < 5 ppm, and H2O < 10 ppm.

[0110] Incident occurred: The operator introduced a new powder container through the rapid transfer chamber, and despite the airlock protection, a small amount of air was still introduced. The RGA instantly detected a sharp rise in O2 partial pressure and a concentration of 50 ppm (severely exceeding the limit).

[0111] Control Response: Strong Intervention of the Purity Control Loop (Outer Loop): Upon receiving this severe exceedance signal, control device 5 activates the powerful purification mode. The MFC set flow rate is significantly increased to its maximum value (e.g., 20 sccm), injecting pure argon gas at the highest rate for dilution. Simultaneously, a command is sent to the first pressure regulating valve 43, causing it to open significantly (even fully), allowing the vacuum pump to operate at maximum capacity. At this time, the pressure control setpoint may be temporarily modified from a fixed slightly positive pressure value to a lower dynamic pressure range (e.g., 100 kPa ~ 90 kPa), allowing the system to operate at sub-atmospheric pressure for a period of time to maximize pumping efficiency.

[0112] After running for a period of time, when the RGA data shows that the O2 partial pressure drops rapidly and approaches the threshold (e.g., the corresponding concentration is close to 10 ppm), the system exits the powerful purification mode. The control device 5 resets the pressure setpoint to 101.5 kPa and coordinates with the MFC to reduce the flow rate and close the pressure regulating valve to allow the system to smoothly return to a normal, stable micro-positive pressure state.

[0113] This solution can quickly dilute impurity concentration while reducing the amount of inert gas used and minimizing the disturbance of airflow to the printing pool. As a result, in the slightly positive pressure mode of the flowing atmosphere, the gas consumption is much lower than that of the traditional continuous high-flow rinsing method.

[0114] Based on the above embodiments, this solution, through RGA and closed-loop control, can actively and stably control the concentration of harmful impurities such as oxygen and water vapor at extremely low levels, far exceeding traditional flushing equipment, thus greatly improving print quality. Simultaneously, the system can automatically decide whether to evacuate or purge based on data from RGA feedback, adapting to changes in gas release at different stages of the printing process. Furthermore, it can fine-tune impurity concentrations as soon as they show signs of exceeding limits, nipping them in the bud rather than waiting until severe contamination occurs. This provides a relatively ideal environment for printing reactive metals such as titanium alloys, high-temperature alloys, and aluminum alloys, reducing the risk of print failures due to atmosphere issues.

[0115] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A printing environment maintenance system, characterized in that, include: Molding chamber; A gas monitoring device is installed in the molding chamber to monitor the gas pressure and concentration of impurity gas components inside the molding chamber; An exhaust device is connected to the molding chamber and extracts the gas inside the molding chamber during operation; An air supply device, connected to the molding chamber, supplies inert gas into the molding chamber during operation; and A control device is connected to the gas monitoring device, the gas extraction device, and the gas delivery device respectively. The control device controls the gas extraction device and the gas delivery device to work together according to the concentration of impurity gas components monitored by the gas monitoring device, and keeps the molding chamber in an inert gas atmosphere. The control device also adjusts the gas extraction volume of the gas extraction device and the gas delivery volume of the gas delivery device according to the gas pressure monitored by the gas monitoring device, and keeps the molding chamber in a slightly positive pressure environment. The evacuation device includes a rough evacuation unit and a high vacuum unit. The rough evacuation unit and the high vacuum unit are respectively connected to the forming chamber. The rough evacuation unit can evacuate the forming chamber to a low vacuum, and the high vacuum unit can evacuate the forming chamber to a high vacuum or ultra-high vacuum. The gas monitoring device includes a residual gas analyzer, which is connected to the molding chamber via a gas sampling interface located in the molding chamber, for real-time monitoring of gas parameters within the molding chamber. Once the molding chamber is in a preset vacuum environment, inert gas is then introduced into the molding chamber through the gas supply device to switch the molding chamber to a slightly positive pressure inert gas atmosphere. The gas monitoring device also includes a switching valve group and multiple sampling tubes. Each sampling tube has a connection end and a sampling end. The multiple sampling tubes are located in the molding chamber. The multiple connection ends are all connected to the gas sampling interface. The switching valve group is located between the gas sampling interface and the multiple connection ends and is used to control the on / off state of the gas sampling interface and each connection end. The multiple sampling ends are distributed at multiple points in the molding chamber. The gas delivery device includes a gas source storage tank, a gas delivery pipe, a mass flow controller, and a first pressure regulating valve. The gas delivery pipe connects the gas source storage tank and the molding chamber. The mass flow controller and the first pressure regulating valve are located on the gas delivery pipe and are arranged sequentially along the direction close to the molding chamber. The molding chamber is equipped with a liquid-cooled jacket.

2. The printing environment maintenance system according to claim 1, characterized in that, The feedthrough interface of the molding chamber adopts a magnetic fluid sealed feedthrough component or a bellows feedthrough component.

3. A method for maintaining a printing environment, used in the printing environment maintenance system as described in claim 1 or 2, characterized in that, The method for maintaining the printing environment includes: Control the operation of the air extraction and air supply devices of the printing environment maintenance system, and adjust the forming chamber of the printing environment maintenance system to be in an inert gas atmosphere and a slightly positive pressure environment; The composition and concentration of impurity gas in the molding chamber are acquired in real time, and it is determined whether the concentration of the corresponding component of the impurity gas exceeds the preset concentration value. If the concentration of the corresponding component of the impurity gas exceeds the preset concentration value, the gas supply device is controlled to deliver inert gas into the molding chamber, and the gas extraction device is controlled to extract the gas from the molding chamber until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, and the molding chamber is maintained in the micro-positive pressure environment.

4. The printing environment maintenance method according to claim 3, characterized in that, If the concentration of the corresponding component of the impurity gas exceeds the preset concentration value, the steps of controlling the gas supply device to deliver inert gas into the molding chamber and controlling the gas extraction device to extract the gas from the molding chamber until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value include: Obtain the concentration difference between the concentration of the corresponding component of the impurity gas and the preset concentration value, and determine whether the concentration difference is within the first interval; If the difference between the concentration of the corresponding component of the impurity gas and the preset concentration value is in the first range, the gas delivery device is first controlled to increase the delivery flow rate of the inert gas until the concentration of the corresponding component of the impurity gas is lower than the preset concentration value, and the gas pressure in the molding chamber is obtained. Determine whether the air pressure inside the molding chamber is within the set range of the slightly positive pressure environment; If the air pressure in the molding chamber exceeds the set range of the micro-positive pressure environment, the air extraction device is controlled to extract the gas from the molding chamber until the air pressure in the molding chamber is within the set range of the micro-positive pressure environment.

5. The printing environment maintenance method according to claim 4, characterized in that, The step of obtaining the concentration difference between the concentration of the corresponding component of the impurity gas and the preset concentration value, and determining whether the concentration difference is within the first interval, further includes: If the concentration difference exceeds the first interval, the gas delivery device is controlled to inject inert gas at a first preset rate, and the gas extraction device is controlled to extract the gas in the molding chamber at a second preset rate, and the gas pressure in the molding chamber is obtained in real time. Obtain the dynamic pressure range of the molding chamber and determine whether the air pressure inside the molding chamber is within the dynamic pressure range; If the air pressure in the molding chamber is within the dynamic pressure range, the air supply device is controlled to run at the first preset rate and the air extraction device is controlled to run at the second preset rate for a preset time. Then, the concentration difference value is obtained again, and it is determined whether the concentration difference value is within the first interval.

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