A multi-stage filtration system with inerting function for an lpbf apparatus

Abstract

The present application relates to the technical field of metal additive manufacturing, and provides a multi-stage filtering system with inertization function for an LPBF device, which solves the problems that the existing device cannot perform online diagnosis on the filtering system performance and lacks long-term safe passivation measures for high-temperature active waste residues. The present application comprises a first-stage filtering module, a second-stage filtering module and a third-stage filtering module connected in series along the airflow direction, as well as a fan module, an inertization spraying module and a controller. The inertization spraying module of the present application achieves two functions of pre-spraying protection and neutralization waste residue spraying through different system action combinations. The pre-coating protection function can prolong the service life of the filter, improve the backflushing effect, the neutralization waste residue spraying function can inhibit the activity of the waste residue and prevent the waste residue from causing sparks, thereby solving the problem of difficult treatment of the waste residue.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and more specifically to a multi-stage filtration system with inerting function for LPBF equipment. Background Technology

[0002] LPBF (Laser Powder Bed Fusion) is an additive manufacturing technology and a metal 3D printing process. It uses a high-energy-density laser to scan a powder bed, causing the metal powder to melt and solidify rapidly. After scanning, the forming platform descends to a certain layer thickness, and the powder spreading mechanism completes the powder spreading action before laser scanning is performed again. This process is repeated to form and stack the desired parts. Compared with traditional processing techniques, LPBF technology has a wider range of applications and is not limited by the complexity of the part shape.

[0003] Currently, dry filtration solutions are widely used in the industry to treat the dust generated by LPBF processes. Typical dry filtration systems usually employ multi-stage filtration structures. For example, Chinese Patent Publication No. CN109045855A discloses a dry filtration device and method for laser 3D printing dust, as well as a filter element replacement method. This solution discloses a filtration device with coarse filtration, multi-stage filter element filtration, and backflushing cleaning functions. It uses an inlet and outlet to introduce liquid to wet the dust on the filter element during replacement to prevent spontaneous combustion, and uses a baffle structure to initially separate large particles of powder. However, while existing devices have differential pressure sensors for monitoring single-stage filtration... The existing technology monitors the blockage of the filter element and triggers backflushing or replacement alarms accordingly. However, this monitoring is isolated and passive, and it cannot effectively assess the overall filtration quality of the front-end filtration system. Existing technologies address the risk of spontaneous combustion of smoke and dust during filter replacement (which is addressed by liquid wetting), but there is a lack of continuous safety passivation measures for the high-temperature and active metal waste generated during backflushing and collected in the waste tank. This waste accumulates in a confined space and poses a risk of slow oxidation and exothermic reaction, or even reignition, which is a long-term potential safety risk within the equipment. Summary of the Invention

[0004] Therefore, in view of the above problems, the present invention provides a multi-stage filtration system with inerting function for LPBF equipment, which solves the problems that existing devices cannot perform online diagnosis of filtration system performance and lack long-term safe passivation measures for high-temperature activated waste residue.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: A multi-stage filtration system with inerting function for LPBF equipment, the system comprising a primary filtration module, a secondary filtration module and a tertiary filtration module connected in series along the airflow direction, as well as a fan module, an inerting spraying module and a controller; The primary filtration module is used to remove large particles of smoke and dust from the gas. The secondary filtration module is connected downstream of the primary filtration module. It contains an online-cleanable filter element, a second differential pressure sensor for monitoring the gas pressure difference before and after filtration, an oxygen sensor for monitoring the internal oxygen concentration, and an ultraviolet / infrared spark sensor for detecting sparks. The secondary filtration module is connected to at least one secondary waste residue tank for collecting the waste residue generated during cleaning. The inlet of the secondary waste residue tank is equipped with an isolation valve. The secondary filtration module and / or the secondary waste residue tank are equipped with a temperature sensor. The tertiary filtration module is connected downstream of the secondary filtration module, and its inlet and outlet are equipped with a third differential pressure sensor for monitoring the gas pressure difference before and after filtration. The inerting spraying module is connected to the secondary filtration module and is used to spray inerting agent into its interior. The inerting spraying module includes an inerting agent storage unit, a spraying execution unit, and a weighing sensor for monitoring the remaining amount of inerting agent. The weighing sensor is electrically connected to the controller. The bottom of the inerting agent storage unit is equipped with a stirring blade. Before each spraying, the inerting spraying module first blows dry inert gas into the pipeline. The fan module includes a fan and a wind speed sensor for monitoring the wind speed in the pipeline. The controller adjusts the fan speed according to the feedback signal from the wind speed sensor. The controller is electrically connected to the second differential pressure sensor, the ultraviolet / infrared spark sensor, the temperature sensor, the third differential pressure sensor, the fan module, the oxygen sensor, and the inerting spraying module. The controller is configured to: receive the differential pressure value monitored by the third differential pressure sensor, and determine whether the filtration quality of the primary and secondary filtration modules meets the standards based on the trend of the differential pressure value monitored by the third differential pressure sensor; receive the monitoring signal from the ultraviolet / infrared spark sensor, immediately stop the machine and cut off the airflow when a spark is detected, and simultaneously start the inerting spraying module to spray inerting agent; receive the monitoring signal from the temperature sensor, and automatically start the inerting spraying module to re-spray inerting agent when the waste residue exceeds the temperature.

[0006] Furthermore, the secondary filtration module also includes a backflushing component, which is electrically connected to the controller. The controller is further configured to control the backflushing component to perform online dust removal on the filter element when the differential pressure value monitored by the second differential pressure sensor exceeds a set threshold.

[0007] Furthermore, the inerting spraying module includes an inerting agent storage unit, a spraying execution unit, and a weighing sensor for monitoring the remaining amount of inerting agent, the weighing sensor being electrically connected to the controller.

[0008] Furthermore, the controller is also configured to control the inerting spraying module to perform at least two working modes: a first mode, inerting agent is sprayed onto the surface of the filter element in the secondary filtration module to form a protective layer; a second mode, after the secondary filtration module performs online cleaning, inerting agent is sprayed onto the waste residue generated during cleaning to neutralize and passivate it, and the isolation valve is controlled to discharge the treated waste residue into the secondary waste residue tank.

[0009] Furthermore, the filter element that can be cleaned online is a sintered plate filter element, and the filter element of the three-stage filtration module is an H13 grade filter element.

[0010] Furthermore, the inerting agent storage unit is equipped with a humidity sensor, the top of the inerting agent storage unit is equipped with a pressure relief valve, a drying chamber is provided on one side of the inerting agent storage unit, the drying chamber is isolated from the inerting agent storage unit by a porous plate, the drying chamber is equipped with color-changing silica gel / molecular sieve desiccant, and an air inlet is provided on one side of the drying chamber.

[0011] Furthermore, the inerting agent storage unit is provided with an insulation shell on its outside, and a heat exchange medium flows inside the insulation shell.

[0012] A working method based on the above-mentioned multi-stage filtration system includes the following steps: S1. System initialization: Start the fan module to establish gas circulation and adjust the wind speed to the preset range; S2, Inertizer pre-spraying: Control the start of the inertizer spraying module to spray inertizer onto the surface of the filter element in the secondary filtration module to form a protective layer; S3. Cyclic monitoring and dust removal: During the printing process, the differential pressure of the secondary filter module is continuously monitored by the second differential pressure sensor. When the differential pressure exceeds the set threshold, the backflush component is controlled to perform online dust removal on the filter element. S4. Waste residue neutralization treatment: After completing online cleaning, control the inerting spraying module to spray inerting agent onto the waste residue generated during cleaning for neutralization and passivation. Then, control the isolation valve to open and discharge the treated waste residue into the secondary waste residue tank. S5. Filtration quality assessment: During the entire system operation, the differential pressure of the three-stage filtration module is continuously monitored by the third differential pressure sensor, and the controller analyzes the trend of differential pressure change to assess the overall filtration quality of the first and second stage filtration modules.

[0013] Furthermore, in step S3, the online dust removal operation is a pulse backflushing operation, which specifically includes: pausing the printing job and the main airflow, and sequentially performing high-pressure gas backflushing on the filter elements of the secondary filtration module in sections.

[0014] Furthermore, in step S5, when the controller analyzes and determines that the differential pressure of the three-stage filtration module shows a continuous abnormal upward trend, a warning signal for decreased filtration efficiency is triggered.

[0015] Furthermore, prior to step S1, an inert gas replacement step is included: inert gas is introduced into the system, and the oxygen concentration in the system is monitored by an oxygen sensor until the oxygen concentration drops below a safe threshold.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention integrates the primary (coarse filtration), secondary (cleanable filtration), and tertiary (final filtration and diagnostic) modules with inerting spraying, oxygen monitoring, and closed-loop wind speed control into a single controller. This not only enables efficient filtration but also allows for real-time monitoring of system safety (oxygen content, wind speed) and provides a complete, closed-loop system with self-diagnostic capabilities (judging the quality of upstream filtration through the three-stage pressure difference trend). This fundamentally improves the reliability and safety of LPBF equipment filtration systems and enables predictive maintenance. The built-in oxygen sensor in the secondary filtration module allows the controller to directly monitor the atmosphere safety in areas most prone to smoke and dust combustion explosions. This provides a direct data basis for fully automatic inert gas replacement and safety interlocks (such as prohibiting backflushing or printing when oxygen content exceeds the limit), thus enhancing the safety level of the equipment.

[0017] 2. The secondary filtration module of the present invention has a backflushing function and is equipped with numerous sensors and valves such as temperature, pressure, differential pressure, oxygen content, safety valve, and pneumatic butterfly valve of the secondary waste tank. It has temperature monitoring, pressure monitoring and overpressure prevention, automatic differential pressure backflushing function, and oxygen content monitoring function, which can realize a fully automatic printing and backflushing process, and the printing is not affected by filtration problems.

[0018] 3. The inerting spraying module of this invention achieves two main functions—pre-coating protection and neutralizing waste residue spraying—through a combination of different system actions. A weighing sensor monitors the amount of inerting agent used. The pre-coating protection function extends filter life and improves backflushing efficiency. The neutralizing waste residue spraying function inhibits waste residue activity, prevents sparks from being generated, and solves the problem of difficult waste residue treatment. Before each spraying, the inerting spraying module first blows dry inert gas into the pipeline to purge residual moisture, preventing contact between pipeline moisture and inerting agent that could lead to clumping and incomplete atomization. Good; the weighing sensor records the weight change after each inerting agent spraying. If the change is less than the minimum value, the stirring blade repeats the stirring and spraying action. If the weight change is still less than the minimum value, an inerting agent spraying failure is detected. The stirring blade at the bottom of the inerting agent storage unit and the heat insulation shell on the outside of the inerting agent storage unit work together to achieve low-heat drying, stirring and anti-caking, and prevent the inerting agent from getting damp and clumping, clogging the nozzle. The drying chamber on one side of the inerting agent storage unit works with the humidity sensor, pressure relief valve and controller to keep the inerting agent dry and non-caking for a long time. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the front structure of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the rear structure of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the inerting agent storage unit structure according to Embodiment 1 of the present invention.

[0020] Explanation of icon numbers: Primary filtration module 1; Secondary filtration module 2; Secondary waste residue tank 21; Isolation valve 22; Tertiary filtration module 3; Fan module 4; Inerting spray module 5; Inerting agent storage unit 51; Stirring blade 52; Drying chamber 53; Insulation shell 54; Backflush component 6; Air manifold 61; Pulse valve 62. Detailed Implementation

[0021] The following will describe in detail the implementation of the present invention with reference to specific embodiments, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0022] Example 1: As Figures 1 to 3 As shown, this embodiment provides a multi-stage filtration system with inerting function for LPBF equipment. The system includes a primary filtration module 1, a secondary filtration module 2 and a tertiary filtration module 3 connected in series along the airflow direction, as well as a fan module 4, an inerting spraying module 5 and a controller (not shown in the figure).

[0023] The primary filtration module 1 uses a cyclone separator to remove large particles of smoke and dust and a small amount of powder carried in the gas drawn from the forming chamber of the LPBF equipment. The separated solid particles fall into the primary waste tank below.

[0024] The secondary filtration module 2 is connected downstream of the primary filtration module via a pipeline. This module contains a filter element that can be cleaned online. In this embodiment, the filter element is preferably a sintered plate filter element, which has the characteristics of high strength, high temperature resistance, and long service life. In order to monitor the working status of the module, a second differential pressure sensor (not shown in the figure) is installed at its inlet and outlet to monitor the gas pressure difference before and after filtration. An oxygen sensor (not shown in the figure) is also installed inside the module to monitor the oxygen concentration inside the module in real time to ensure an inert environment. A secondary waste residue tank 21 is connected to the bottom of the secondary filtration module 2 to collect the waste residue that falls off during the online cleaning (backflushing) of the filter element. The inlet of the secondary waste residue tank 21 is equipped with a pneumatic isolation valve 22 to isolate the waste residue tank during non-slag discharge periods.

[0025] In other preferred embodiments, the bottom of the secondary filter module 2 is connected to two secondary waste residue tanks 21, which are switched by corresponding valves. When one secondary waste residue tank 21 is detected to be almost full, the second secondary waste residue tank 21 is switched to use. The full secondary waste residue tank 21 is allowed to stand for a set time (such as 24H or 48H) to indicate that the waste residue can be processed. The purpose is that the waste residue tank that has just been used is difficult to process or replace in time, and it generally needs to stand before processing. This avoids unnecessary risks and time waste caused by changing or cleaning the waste residue tank during the printing process.

[0026] The tertiary filtration module 3 is connected downstream of the secondary filtration module 2 via a pipe, serving as the final gas filtration stage. In this embodiment, its filter element is preferably an H13 grade filter element. A third differential pressure sensor (not shown in the figure) is installed at the inlet and outlet of this module.

[0027] The inerting spraying module 5 is connected to the air inlet chamber of the secondary filtration module 2 via a spraying pipe. This module includes an inerting agent storage unit 51 for storing inerting agents (such as nano-ceramic-based inerting agents, phosphate-based passivating agents, etc.), a spraying execution unit driven by high-pressure inert gas (using a spraying pump, not shown in the figure), and a weighing sensor (not shown in the figure) for weighing the entire inerting agent storage unit. The inerting agent storage unit 51 has an automatic supply interface (such as an electric valve, pneumatic valve, etc.), which automatically supplies inerting agent when the weight is below a certain value, reducing the risk of insufficient inerting agent dosage. To address potential issues causing inerting failure, the inerting agent storage unit 51 is equipped with a stirring blade 52 at its bottom. This blade is driven by an external rotating motor to prevent the inerting agent from becoming damp, clumping, or clogging the nozzle. Before each spray, the inerting spraying module 5 first blows dry inert gas into the pipeline to purge residual moisture, preventing contact between pipeline moisture and the inerting agent, which could lead to clumping and poor atomization. During purging, the stirring blade 52 does not rotate; during spraying, the stirring blade 52 rotates. In this embodiment, the stirring blade 52 is a plate-type stirring blade; in other preferred embodiments, the stirring blade 52 is a spiral-type stirring blade.

[0028] The weighing sensor records the weight change after each application of inerting agent. If the change is less than the minimum value, the stirring blade 52 repeats the stirring and spraying action. If the weight change is still less than the minimum value, an inerting agent spraying failure is detected.

[0029] The inerting agent storage unit 51 has a drying chamber 53 on one side, which is isolated from the inerting agent storage unit by a perforated plate. The drying chamber 53 contains molecular sieve desiccant, and an air inlet is provided on one side of the drying chamber. The inerting agent storage unit is equipped with a humidity sensor (not shown in the figure), and a pressure relief valve (not shown in the figure) is provided on the top of the inerting agent storage unit. The humidity sensor and the pressure relief valve are electrically connected to the controller. When the humidity exceeds the threshold, air is introduced into the drying chamber 53 through the air inlet, and the molecular sieve desiccant is sent into the inerting agent storage unit 51 through the perforated plate. At this time, the pressure relief valve releases pressure, and then a slight positive pressure is applied to the inerting agent storage unit 51 to keep the inerting agent dry and prevent it from clumping.

[0030] The inerting agent storage unit 51 is provided with an insulation shell 54 on the outside. A heat exchange medium flows inside the insulation shell 54 to maintain a low temperature of 40–60°C inside the inerting agent storage unit, thereby achieving low-temperature drying. In this embodiment, the heat exchange medium is water. In other preferred embodiments, the heat exchange medium can also be conventional heat exchange media such as heat transfer oil or air.

[0031] The secondary filter module 2 is also equipped with an infrared spark sensor (not shown in the figure) to detect sparks inside the module. If a spark is detected, the module will stop immediately and the airflow will be cut off. At the same time, the inerting spraying module 5 will be activated to spray inerting agent. The secondary waste residue tank 21 is equipped with a temperature sensor (not shown in the figure). If the waste residue exceeds the temperature, the inerting spraying module 5 will be activated to spray inerting agent again, forming a safe closed loop of temperature triggering and automatic repassivation.

[0032] The fan module 4 includes a variable frequency sealed fan and a wind speed sensor (not shown in the figure) installed on the main air duct. The controller adjusts the fan speed in real time according to the feedback signal of the wind speed sensor to maintain the system's circulating air volume at a stable set value.

[0033] The controller (using a PLC or industrial computer) is electrically connected to the second differential pressure sensor, the third differential pressure sensor, the oxygen sensor, the wind speed sensor, the load cell, the fan module, the inerting spraying module, and the backflushing component 6 (including the air tank 61 and several pulse valves 62) and the isolation valve 22 included in the secondary filtration module; the controller is configured to execute the following logic: control backflushing and cleaning according to the signal from the second differential pressure sensor, and continuously receive and analyze the differential pressure value and its changing trend monitored by the third differential pressure sensor.

[0034] The controller works as follows: Under ideal conditions, the gas after secondary filtration is very clean, and the dust load reaching the tertiary filtration module is extremely low. Therefore, the initial differential pressure of the tertiary filtration module 3 is very small and increases extremely slowly. If the filtration efficiency of the secondary filtration module 2 (or the primary filtration module 1) decreases, for example, if the sintered plate filter element has microscopic damage or sealing failure, more fine particles will penetrate and reach the tertiary filtration module 3. These particles will accelerate the clogging of the H13 filter element, resulting in a continuous and abnormal upward trend in the reading of the third differential pressure sensor. By calculating the differential pressure growth rate per unit time, the controller can identify this trend and determine that the overall filtration quality of the primary and secondary filtration modules is substandard, thereby triggering an early warning signal to prompt the operator to check or maintain the system, without waiting for the secondary filter element itself to trigger a differential pressure alarm due to clogging. This achieves online diagnosis and predictive maintenance of the front-end filtration system performance.

[0035] In addition, the controller is also configured to control the inerting spraying module 5 to perform two key operating modes: Pre-coating protection mode: Before the equipment starts printing, the controller activates the inerting spraying module 5 to spray the atomized inerting agent onto the surface of the sintered plate filter element of the secondary filter module 2, forming a protective film. This film can isolate high-temperature smoke and dust from the filter element substrate during the printing process, reduce the adhesion of smoke and dust sintering, and make subsequent backflushing and cleaning easier and more thorough, thereby significantly extending the filter element life.

[0036] After the backflushing action is completed and the internal atmosphere of the equipment is automatically restarted, the controller also controls the inerting spraying module 5 to execute the pre-spraying protection mode.

[0037] Waste neutralization mode: After each online cleaning operation, the controller restarts the inerting spraying module 5 to spray inerting agent onto the hot waste residue that has just been back-blown down and accumulated at the bottom of the secondary filter module 2. The inerting agent mixes with the active metal waste residue and undergoes a passivation reaction, neutralizing its chemical activity and making it lose its ability to spontaneously combust or slowly oxidize. Subsequently, the controller opens the isolation valve 22 of the secondary waste residue tank 21 to discharge the passivated safe waste residue into the tank for storage. This fundamentally eliminates the safety hazards of waste residue in the collection process.

[0038] The secondary filtration module 2 also includes a backflush component 6 consisting of a pulse valve 62 and an air manifold 61. The controller automatically triggers the backflush action when the value of the second differential pressure sensor exceeds a set threshold based on the signal from the second differential pressure sensor.

[0039] Secondary filtration module 2 backflushing action: After shutting down the fan and closing the pneumatic butterfly valve in the pipeline, each pulse valve 62 opens for a certain period of time and then closes to complete the backflushing action. Among them, after each pulse valve 62 opens and closes, the air supply valve of the air tank 61 opens for a certain period of time and then closes. After the backflushing is completed, the inerting agent neutralization and waste residue spraying action is performed.

[0040] The figure only shows the location distribution of key components and does not show all pipelines and sensors. Those skilled in the art can understand and implement the content of the scheme based on the text and figures of this application.

[0041] Example 2: An automatic operation method based on the filtration system described in Example 1. This example provides an automatic operation method for the above-mentioned multi-stage filtration system, including the following steps: S1. System Initialization: When the LPBF equipment is ready to start printing, inert gas (such as argon or nitrogen) is first introduced into the entire filtration system and forming chamber. The oxygen concentration in the system is monitored by the oxygen sensor in the secondary filtration module 2. The controller continuously reads the oxygen sensor data until the oxygen concentration drops below the safety threshold. Then, the controller turns on the fan module 4 to establish gas circulation and dynamically adjusts the fan speed according to the feedback from the wind speed sensor so that the wind speed in the main air duct reaches and stabilizes within the preset target range.

[0042] S2, Inerting agent pre-coating: After confirming that the oxygen content meets the standard and the wind speed is stable, the controller executes the filter element pre-protection program, controls the opening of the spraying valve of the inerting spraying module 5, starts the spraying pump, and sprays the preset dose of inerting agent into the secondary filter module 2 in the form of atomization. The inerting agent is evenly attached to the surface of the sintered plate filter element with the airflow to form a protective layer. After the spraying is completed, the spraying module is turned off.

[0043] S3. Cyclic Monitoring and Dust Removal: The LPBF equipment begins normal printing. During printing, the controller continuously monitors the differential pressure of the secondary filtration module via the second differential pressure sensor. When the differential pressure rises due to dust accumulation on the filter element surface and exceeds the preset trigger threshold, the controller waits for the current laser scanning layer to complete. During the brief interval before the powder spreading mechanism operates, it automatically performs online dust removal. This online dust removal operation is a pulse backflushing: The controller first pauses the fan and closes the main air duct valve to isolate the filter chamber; then, it controls multiple pulse valves 62 of the backflushing component to open sequentially and at intervals, instantly releasing the high-pressure inert gas in the air tank 61 to powerfully blow the sintered plate filter element in sections, causing the attached dust to fall off.

[0044] S4. Waste neutralization treatment: After the online dust removal operation is completed, the controller immediately starts the inerting spraying module 5 to execute the waste neutralization program. A certain amount of inerting agent is sprayed onto the high-temperature waste pile that has just been back-blown down at the bottom of the secondary filter module 2. After the spraying is completed, it is left to stand for a short time to ensure mixing and initial reaction. Then, the controller opens the isolation valve 22 at the inlet of the secondary waste tank 21, so that the passivated waste is discharged into the waste tank under the action of gravity, and then the valve is closed.

[0045] S5. Filtration Quality Assessment: After waste residue treatment is completed, the controller reopens the main air duct valve and fan, and quickly adjusts the air speed back to the target value based on the wind speed sensor signal. The system status returns to normal, and the equipment continues the interrupted powder spreading and subsequent scanning and printing. At the same time, throughout the entire printing process, the controller continuously monitors the differential pressure of the three-stage filtration module through the third differential pressure sensor, and analyzes the change curve and trend of the differential pressure data in real time. If the analysis finds that the differential pressure shows a stable and slow normal increase, it is determined that the front-end filtration efficiency is good. If the analysis identifies a continuous and rapid abnormal upward trend in the differential pressure, the controller immediately triggers the "filtration efficiency decline" warning signal, displays the alarm information on the equipment's human-machine interface, and prompts the operator that there may be a problem with the front-end filtration system, which needs to be checked.

[0046] This method, through the automated execution of the above steps, not only achieves self-cleaning (backflushing) of the filtration system and immediate safe treatment of waste residue (inerting and neutralization), but more importantly, it utilizes the three-stage filtration module 3 as a diagnostic probe and uses its pressure difference change as an indirect signal to achieve continuous monitoring and intelligent diagnosis of the quality of the upstream filtration process.

[0047] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A multi-stage filtration system with inerting function for LPBF equipment, characterized in that, The system includes a primary filtration module, a secondary filtration module, and a tertiary filtration module connected in series along the airflow direction, as well as a fan module, an inert coating module, and a controller. The primary filtration module is used to remove large particles of smoke and dust from the gas. The secondary filtration module is connected downstream of the primary filtration module. It contains an online-cleanable filter element, a second differential pressure sensor for monitoring the gas pressure difference before and after filtration, an oxygen sensor for monitoring the internal oxygen concentration, and an ultraviolet / infrared spark sensor for detecting sparks. The secondary filtration module is connected to at least one secondary waste residue tank for collecting the waste residue generated during cleaning. The inlet of the secondary waste residue tank is equipped with an isolation valve. The secondary filtration module and / or the secondary waste residue tank are equipped with a temperature sensor. The tertiary filtration module is connected downstream of the secondary filtration module, and its inlet and outlet are equipped with a third differential pressure sensor for monitoring the gas pressure difference before and after filtration. The inerting spraying module is connected to the secondary filtration module and is used to spray inerting agent into its interior. The inerting spraying module includes an inerting agent storage unit, a spraying execution unit, and a weighing sensor for monitoring the remaining amount of inerting agent. The weighing sensor is electrically connected to the controller. The bottom of the inerting agent storage unit is equipped with a stirring blade. Before each spraying, the inerting spraying module first blows dry inert gas into the pipeline. The fan module includes a fan and a wind speed sensor for monitoring the wind speed in the pipeline. The controller adjusts the fan speed according to the feedback signal from the wind speed sensor. The controller is electrically connected to the second differential pressure sensor, the ultraviolet / infrared spark sensor, the temperature sensor, the third differential pressure sensor, the fan module, the oxygen sensor, and the inerting spraying module. The controller is configured to: receive the differential pressure value monitored by the third differential pressure sensor, and determine whether the filtration quality of the primary and secondary filtration modules meets the standards based on the trend of the differential pressure value monitored by the third differential pressure sensor; receive the monitoring signal from the ultraviolet / infrared spark sensor, immediately stop the machine and cut off the airflow upon detecting a spark, and simultaneously start the inerting spraying module to spray inerting agent; receive the monitoring signal from the temperature sensor, and automatically start the inerting spraying module to re-spray inerting agent if the waste residue exceeds the temperature. The secondary filtration module also includes a backflushing component, which is electrically connected to the controller. The controller is further configured to control the backflushing component to perform online dust removal on the filter element when the differential pressure value monitored by the second differential pressure sensor exceeds a set threshold.

2. A multi-stage filtration system with inerting function for LPBF equipment according to claim 1, characterized in that: The filter element that can be cleaned online is a sintered plate filter element, and the filter element of the three-stage filtration module is an H13 grade filter element.

3. A multi-stage filtration system with inerting function for LPBF equipment according to claim 1, characterized in that: The controller is also configured to control the inerting spraying module to perform at least two operating modes: a first mode, inerting agent is sprayed onto the surface of the filter element in the secondary filtration module to form a protective layer; and a second mode, after the secondary filtration module performs online cleaning, inerting agent is sprayed onto the waste residue generated during cleaning to neutralize and passivate it, and the isolation valve is controlled to discharge the treated waste residue into the secondary waste residue tank.

4. A multi-stage filtration system with inerting function for LPBF equipment according to claim 1, characterized in that: The inerting agent storage unit is equipped with a humidity sensor, and the top of the inerting agent storage unit is equipped with a pressure relief valve. A drying chamber is provided on one side of the inerting agent storage unit. The drying chamber is isolated from the inerting agent storage unit by a porous plate. The drying chamber is equipped with color-changing silica gel / molecular sieve desiccant, and an air inlet is provided on one side of the drying chamber.

5. A multi-stage filtration system with inerting function for LPBF equipment according to claim 1, characterized in that: The inerting agent storage unit is provided with an insulation shell on the outside, and a heat exchange medium flows inside the insulation shell.

6. A method of operating a multi-stage filtration system according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. System initialization: Start the fan module to establish gas circulation and adjust the wind speed to the preset range; S2, Inertizer pre-spraying: Control the start of the inertizer spraying module to spray inertizer onto the surface of the filter element in the secondary filtration module to form a protective layer; S3. Cyclic monitoring and dust removal: During the printing process, the differential pressure of the secondary filter module is continuously monitored by the second differential pressure sensor. When the differential pressure exceeds the set threshold, the backflush component is controlled to perform online dust removal on the filter element. S4. Waste residue neutralization treatment: After completing online cleaning, control the inerting spraying module to spray inerting agent onto the waste residue generated during cleaning for neutralization and passivation. Then, control the isolation valve to open and discharge the treated waste residue into the secondary waste residue tank. S5. Filtration quality assessment: During the entire system operation, the differential pressure of the three-stage filtration module is continuously monitored by the third differential pressure sensor, and the controller analyzes the trend of differential pressure change to assess the overall filtration quality of the first and second stage filtration modules.

7. The working method according to claim 6, characterized in that, In step S3, the online dust removal operation is a pulse backflushing operation, which specifically includes: pausing the printing job and the main airflow, and sequentially performing high-pressure gas backflushing on the filter elements of the secondary filtration module in sections.

8. The working method according to claim 6, characterized in that: In step S5, when the controller analyzes and determines that the differential pressure of the three-stage filtration module shows a continuous abnormal upward trend, it triggers a warning signal for decreased filtration efficiency.

9. The working method according to claim 6, characterized in that: Before step S1, an inert gas replacement step is also included: inert gas is introduced into the system, and the oxygen concentration in the system is monitored by an oxygen sensor until the oxygen concentration drops below a safe threshold.

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