Intelligent gas circulation cooling system for SLM equipment

Abstract

The invention discloses an intelligent gas circulation cooling system for SLM equipment, and the system comprises a heat exchange module which comprises a heat exchanger and a refrigerating unit; the circulating air path main body comprises a closed gas circulating path which is formed by sequentially communicating a printing cabin, a circulating filtering system, a circulating fan and a heat exchanger through pipelines; the sensing module comprises a temperature sensor and an anemometer which are used for monitoring the gas cooled by the heat exchange module in real time; and the control and display module comprises a control unit and a human-computer interaction interface for visual display. Temperature and flow speed signals of outlet air flow are collected in real time through a sensor, real-time and in-situ monitoring signals of the air temperature serve as core feedback variables for managing printing heat accumulation to be introduced into control logic, system-level cooperation is carried out with an air speed control loop, and a multivariable feedback closed loop is formed; cooperative stable control of'temperature-flow velocity 'of an air inlet wind field is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of gas circulation and heat management control system for metal selective laser melting (SLM, Selective Laser Melting) equipment, especially a kind of system for the temperature and flow rate of protective gas are cooperatively regulated by integrating heat exchange module and real-time feedback unit, belong to additive manufacturing equipment technical field. BACKGROUND

[0002] In the metal selective laser melting (SLM) additive manufacturing process, the circulation of protective gas (usually argon or nitrogen) is crucial, which is used to remove smoke and maintain the inert environment of forming chamber, while exchanging heat with the printing surface to take away the cabin heat and participate in the heat balance of cabin. However, as the printing process continues, a large amount of heat generated by laser molten pool will be continuously absorbed by the circulating gas, causing the temperature of the wind field gas to continue to rise, which cannot effectively take away the cabin heat. This heat accumulation effect eventually leads to unstable thermal environment in the forming cabin, and obvious overheating phenomenon occurs during printing, causing the surface of the printed product to turn blue and black, affecting the consistency of microstructure and the mechanical properties of the product.

[0003] For the problem of heat accumulation during printing, the current method is to control and adjust the printing process parameters (such as changing the laser power, scanning speed, etc.). Due to the variety of materials and shapes of 3D printing products, this process adjustment method is complex and difficult to be universally applicable.

[0004] To alleviate the problem of heat accumulation during printing, various schemes in the prior art all have defects. The first type of scheme focuses on improving the static cooling capacity, such as installing a high-efficiency heat exchanger in the circulating pipeline (such as the practice of AMCM company), which reduces the gas temperature by enhancing heat exchange. This kind of scheme is passive and static, and its essence is the integration of a single device, which cannot respond to the dynamic changes of heat load during printing, cannot sense the dynamic changes of the circulating gas state (such as temperature, flow rate) during printing in real time, and cannot actively adjust accordingly. The second type of scheme is the air inlet speed closed-loop control realized by some devices, which adjusts the fan speed through the feedback of the air speed sensor to maintain the set gas flow rate constant. However, this scheme is mainly to ensure the stability of smoke removal effect, and its original intention and core function are not aimed at solving the problem of heat accumulation during printing, and it does not cooperate with the control of gas temperature, so it cannot solve the problem of heat accumulation.

[0005] None of the above-mentioned solutions can accurately maintain a constant thermal environment and airflow state in the forming area during continuous printing operations lasting tens or even hundreds of hours, thus failing to fundamentally suppress the gradual accumulation of heat. In particular, with the increasing pursuit of printing efficiency, the number and power of lasers in SLM equipment are constantly increasing, making it difficult for the above solutions to meet the demands of high-efficiency, high-power, and long-term continuous printing. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide an intelligent gas circulation control system and method for SLM equipment to address heat accumulation during SLM printing. This system enables real-time monitoring of heat load changes during the printing process, dynamic adjustment of cooling and flow parameters of the circulating gas, real-time monitoring and dynamic coordinated adjustment of the temperature and flow rate of the protective gas entering the printing chamber, and proactive and precise maintenance of the stability of the thermal environment in the printing area. This effectively suppresses heat accumulation during the printing process and improves the quality and consistency of the molded parts.

[0007] To address the above problems, the present invention provides an intelligent gas circulation cooling system for SLM equipment, comprising: The heat exchange module includes a heat exchanger and a refrigeration unit, which are connected by two cooling medium channels to form a heat exchange circulation path. The main body of the circulating air path includes a closed gas circulation path that is connected in sequence through pipes to the printing chamber, the circulating filtration system, the circulating fan, and the heat exchanger; The sensing module includes a temperature sensor and an anemometer for real-time monitoring of the gas cooled by the heat exchange module; The control and display module includes a control unit and a human-machine interface for visual display; the signal output terminals of the temperature sensor and the anemometer are connected to the signal input terminal of the control unit and the human-machine interface respectively via data cables; the first control output terminal of the control unit is connected to the speed controller of the circulating fan, and the second control output terminal is connected to the power controller of the refrigeration unit.

[0008] Preferably, the printing chamber has an air inlet on one side and an air outlet on the other side. The air inlet is connected to the heat exchanger through an air inlet pipe section, and the air outlet is connected to the circulating filtration system through an air outlet pipe section.

[0009] Preferably, the temperature sensor and the anemometer are both located on the pipe on the air outlet side of the heat exchanger.

[0010] Preferably, the outlet protective gas temperature T_real of the heat exchanger is established as the key direct parameter and core feedback variable characterizing the thermal accumulation state of the SLM printing process, and the operating mode is a human-machine collaborative semi-closed-loop mode or a fully automatic closed-loop mode. This is a fundamental feature that distinguishes it from all existing solutions that only focus on indirect parameters such as flow rate, pressure, or cooling water temperature. Based on the clear definition of the core feedback variable, a closed-loop circulating gas thermal management system based on temperature feedback is achieved.

[0011] More preferably, the human-machine collaborative semi-closed-loop mode is as follows: the system provides real-time feedback of the T_real value and its changing trend to the operator through a human-machine interface; when T_real indicates that heat accumulation is intensifying, the operator adjusts the set parameters of the refrigeration unit based on this direct temperature feedback, thereby changing the cooling intensity and realizing active intervention in heat accumulation. This mode constitutes an efficient "monitoring-display-human decision-making-adjustment" semi-closed loop. The fully automatic closed-loop mode is as follows: the control unit is configured to compare T_real with the preset target gas temperature T_target, and automatically output adjustment signals to the refrigeration unit through the control algorithm to dynamically change its cooling power, so that T_real is stabilized near T_target, forming a complete automatic temperature control closed loop.

[0012] Furthermore, T_real indicates that increased heat accumulation means that T_real continuously exceeds a set threshold.

[0013] Furthermore, adjusting the setting parameters of the refrigeration unit specifically involves reducing the target temperature of the coolant or the coolant flow rate.

[0014] Furthermore, the control algorithm is PID.

[0015] Furthermore, the control unit adjusts the refrigeration unit according to the change of T_real, or dynamically optimizes the wind speed setpoint V_target.

[0016] This invention defines the collaborative relationship between the temperature management loop and the wind speed control loop. This collaboration is manifested in: Unified Goal: Both serve the common advanced process goal of "suppressing heat accumulation during printing and stabilizing the thermal environment," rather than operating independently.

[0017] Logical layering: Stable airflow provides stable and predictable fluid conditions for heat exchange between the gas and the heat exchanger, which effectively improves the efficiency, linearity, and determinism of subsequent gas temperature (T_real) management by adjusting the refrigeration unit. Airflow control constitutes the foundation layer, while thermal management based on T_real feedback constitutes the optimization layer.

[0018] Interaction: In the preferred control strategy, the control unit can adjust not only the refrigeration unit based on changes in T_real, but also dynamically optimize the fan speed setpoint (V_target). For example, when the heat load increases sharply, commands to "moderately increase the fan speed" and "enhance the cooling" can be issued in tandem to achieve a faster response.

[0019] The entire system constitutes a multi-variable, closed-loop intelligent control system with the ultimate goal of "maintaining a constant airflow state at the air outlet" and the means of execution of "adjusting fan speed" and "adjusting cooling power". The system can actively adapt to dynamic thermal load disturbances caused by laser energy input, printing speed, and changes in part geometry.

[0020] This invention uses sensors to collect real-time temperature and velocity signals of the airflow. The real-time, in-situ monitoring signal of the gas temperature is introduced into the control logic as the core feedback variable for managing printing heat accumulation. This is then coordinated with the wind speed control loop at the system level to form a bivariate (or multivariate) feedback closed loop, achieving coordinated and stable control of the "temperature-velocity" relationship in the intake airflow. This invention uses the velocity and temperature of the protective gas as core parameters. By constructing a heat exchange and closed-loop feedback system, it achieves multi-parameter control through semi-automatic or fully automatic intelligent regulation, thereby effectively improving the stability of the equipment's gas circulation system. This addresses the significant process problem of heat accumulation from an equipment perspective and is of great importance for printing long-duration, high-power, phase-change-sensitive materials (such as martensitic steel).

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the SLM gas circulation system, the outlet gas temperature is introduced as the core feedback variable into the thermal management closed loop, which fills the gap in the existing technical solutions' ability to directly sense and control the thermal state of the printing process.

[0022] 2. Systematic: By designing and controlling the temperature management loop and the wind speed control loop in a coordinated manner with a unified objective, the limitations of single parameter control are overcome, and a system-level optimization effect of "1+1>2" is achieved.

[0023] 3. High practicality: The provided "human-machine collaborative semi-closed loop" embodiment does not require complex fully automated algorithms. It can achieve major process improvements at low cost and with high reliability using existing industrial components, and is very easy to promote.

[0024] 4. Significant Benefits: Directly improves the thermal stability of the printing process, significantly enhancing the success rate and quality consistency of printing large-sized parts made from phase-change sensitive materials (such as martensitic steel). Actual testing shows that the protective gas temperature and velocity can remain stable at the set target values ​​over a long period, resulting in a significant improvement in product printing quality without adjusting existing printing process parameters. Attached Figure Description

[0025] Figure 1 A schematic diagram of the intelligent gas circulation cooling system provided by the present invention; Figure 2 The control logic flowchart is shown in the example. Detailed Implementation

[0026] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0027] like Figure 1 As shown, an intelligent gas circulation cooling system for SLM equipment provided by the present invention includes: The heat exchange module includes a heat exchanger 4 and a refrigeration unit 6, which are connected by two cooling medium channels 61 to form a heat exchange circulation path. The main body of the circulating air path includes a closed gas circulation path that is connected in sequence through pipes to the printing chamber 1, the circulating filtration system 2, the circulating fan 3, and the heat exchanger 4; the printing chamber 1 has an air inlet 11 on one side and an air outlet 12 on the other side. The air inlet 11 is connected to the heat exchanger 4 through an air inlet pipe section 22, and the air outlet 12 is connected to the circulating filtration system 2 through an air outlet pipe section 21. The sensing module includes a temperature sensor 51 and an anemometer 52 for real-time monitoring of the gas cooled by the heat exchange module; the temperature sensor 51 and the anemometer 52 are both located on the pipe on the air outlet side of the heat exchanger 4. The control and display module includes a control unit 7 and a human-machine interface 8 for visual display; the signal output terminals of the temperature sensor 51 and the anemometer 52 are respectively connected to the signal input terminal of the control unit 7 and the human-machine interface 8 via data cables; the first control output terminal of the control unit 7 is connected to the speed regulator of the circulating fan 3, and the second control output terminal is connected to the power controller of the refrigeration unit 6.

[0028] The aforementioned system uses the outlet protective gas temperature T_real of heat exchanger 4 as the key direct parameter and core feedback variable characterizing the heat accumulation state during the SLM printing process. The operating modes are either a human-machine collaborative semi-closed-loop mode or a fully automatic closed-loop mode. In the human-machine collaborative semi-closed-loop mode, the system provides real-time feedback of the T_real value and its trend to the operator via the human-machine interface 8. When T_real indicates increased heat accumulation (T_real continuously exceeds the set threshold), the operator adjusts the set parameters of the refrigeration unit 6 based on this direct temperature feedback (reducing the target coolant temperature or coolant flow rate), thereby changing the cooling intensity and actively intervening in heat accumulation. This mode constitutes an efficient "monitoring-display-manual decision-making-adjustment" semi-closed loop. In the fully automatic closed-loop mode, the control unit 7 is configured to compare T_real with the preset target gas temperature T_target and automatically output an adjustment signal to the refrigeration unit 6 through a control algorithm (such as PID), dynamically changing its cooling power to stabilize T_real near T_target, forming a complete automatic temperature control closed loop. The control unit adjusts the refrigeration unit according to the change of T_real, or dynamically optimizes the wind speed setpoint V_target.

[0029] Example The specific operation process of the above system is as follows (e.g.) Figure 2 (as shown) 1. Using a certain model of SLM selective laser melting equipment (forming size 300×300mm) as a prototype, modify and configure the gas circulation system: Add a high-efficiency heat exchanger at the equipment's air inlet duct. The heat exchanger type is shell-and-tube or finned, and the heat exchange mode is gas-liquid exchange. The heat exchanger is installed at the rear end of the equipment's variable frequency circulating fan. Install a temperature sensor and a wind speed sensor at the air outlet of the heat exchanger; the temperature sensor and wind speed sensor are respectively connected to the control unit and the human-machine interface. The first control output terminal and the second control output terminal of the control unit are respectively connected to the speed controller of the equipment's circulating fan and the power controller of the refrigeration unit.

[0030] 2. In the specific implementation process, the printing material is a self-developed 3D printing martensitic steel, the printing power is 250-450W, the scanning speed is 600-900mm / s, the printing layer thickness is 0.03-0.1mm, and the scanning spacing is 0.08-0.18mm.

[0031] 3. Based on the calculated and measured heat load of the SLM equipment for printing this material, the selected high-efficiency heat exchanger should have a rated heat exchange capacity of not less than 1.2kW and a heat dissipation area of ​​not less than 0.2m². 2Based on the characteristic curve of the circulating fan, the selected high-efficiency heat exchanger, under the set gas flow rate, has an outlet-side pressure drop relative to the inlet-side that is no higher than 10%.

[0032] 4. Based on the analysis of historical printing data of this material using SLM equipment, the target circulating gas temperature threshold is set to any typical value within the range of 25-50℃, such as 40℃. Exceeding this temperature indicates significant heat accumulation during the printing process. The target circulating gas flow rate V_target is set to any typical value within the range of 2-6 m / s, such as 4.5 m / s, with a fluctuation range ΔV not exceeding 0.5 m / s. At this flow rate, the circulating gas maintains its dust removal effect while effectively exchanging heat with the printing environment. The initial coolant temperature of the refrigeration unit is set to 25℃.

[0033] 5. In the human-machine collaborative embodiment, the human-machine interface displays the circulating gas temperature T_real in real time. As the printing process proceeds, printing heat accumulates, and the circulating gas temperature T_real shows a significant increase. The operator continuously monitors the real-time changes in the circulating gas temperature. When T_real consistently exceeds the set target circulating gas temperature threshold of 40°C, the operator adjusts the coolant temperature of the refrigeration unit to 22°C based on this direct temperature feedback, while simultaneously observing the changes in the circulating gas temperature and continuing to increase or decrease the coolant temperature setting. After the above adjustments, T_real drops back and eventually stabilizes at 25±1°C within approximately 20 minutes.

[0034] As a preferred option, the above-mentioned control and adjustment steps based on human-machine collaboration can be automatically executed by the control unit to form a fully closed-loop control. The specific control process is as follows: 1. In addition to setting the target wind speed V_target = 4.5m / s and the upper and lower fluctuation range ΔV = 0.5m / s, the operator also sets a target gas temperature T_target = 25℃ and an allowable deviation range ΔT = 0.5℃ in the control unit.

[0035] 2. The temperature sensor collects the outlet temperature T_real in real time and feeds it back to the control unit. The control unit continuously calculates the temperature difference T_real - T_target between the actual temperature and the target gas temperature and compares it with ΔT.

[0036] 3. When the temperature difference T_real - T_target > ΔT (i.e., gas is superheated) and lasts for more than 30 seconds, the control unit sends a command to the chiller unit according to the preset PID algorithm to increase the cooling power. When T_real - T_target < -ΔT (i.e., gas is supercooled), the control unit sends a command to the chiller unit to reduce the cooling power or enter heating mode. When -ΔT ≤ T_real - T_target ≤ ΔT, the chiller unit maintains its current power operation.

[0037] 4. The automatic gas temperature control loop and the closed-loop wind speed control loop are data-coupled within the control unit. When a rapid increase in T_real is detected, the control unit simultaneously sends a command to the circulating fan to fine-tune and increase the fan speed, adjusting the gas flow rate to the set upper limit V_target + ΔV = 5 m / s to enhance heat exchange. After the gas temperature drops, the original fan power is restored, maintaining a constant gas flow rate of 4.5 m / s.

[0038] 5. In this mode, the system can keep the fluctuation of gas temperature T_real within an extremely narrow range of 25±0.2℃ during 48 hours of continuous printing, achieving completely stable and unattended circulating gas thermal management.

Claims

1. A smart gas circulation cooling system for SLM equipment, characterized in that, include: The heat exchange module includes a heat exchanger (4) and a refrigeration unit (6), which are connected by two cooling medium channels (61) to form a heat exchange circulation path. The main body of the circulating air path includes a closed gas circulation path consisting of a printing chamber (1), a circulating filtration system (2), a circulating fan (3), and a heat exchanger (4) connected in sequence through pipes; The sensing module includes a temperature sensor (51) and an anemometer (52) for real-time monitoring of the gas cooled by the heat exchange module. The control and display module includes a control unit (7) and a human-machine interface (8) for visualization display; the signal output terminals of the temperature sensor (51) and the anemometer (52) are connected to the signal input terminal of the control unit (7) and the human-machine interface (8) respectively via data cables; the first control output terminal of the control unit (7) is connected to the speed regulator of the circulating fan (3), and the second control output terminal is connected to the power controller of the refrigeration unit (6).

2. The intelligent gas circulation cooling system for SLM equipment as described in claim 1, characterized in that, The printing chamber (1) has an air inlet (11) on one side and an air outlet (12) on the other side. The air inlet (11) is connected to the heat exchanger (4) through the air inlet pipe section (22), and the air outlet (12) is connected to the circulating filtration system (2) through the air outlet pipe section (21).

3. The intelligent gas circulation cooling system for SLM equipment as described in claim 1, characterized in that, The temperature sensor (51) and the anemometer (52) are both located on the pipe on the air outlet side of the heat exchanger (4).

4. The intelligent gas circulation cooling system for SLM equipment as described in claim 1, characterized in that, The temperature of the protective gas at the outlet of the heat exchanger (4) is established as the key direct parameter and core feedback variable characterizing the thermal accumulation state of the SLM printing process. The working mode is either human-machine collaborative semi-closed loop mode or fully automatic closed loop mode.

5. The intelligent gas circulation cooling system for SLM equipment as described in claim 4, characterized in that, The human-machine collaborative semi-closed-loop mode is as follows: the system feeds back the T_real value and its trend to the operator in real time through the human-machine interface (8); when T_real indicates that the heat accumulation is aggravated, the operator adjusts the setting parameters of the refrigeration unit (6) based on this direct temperature feedback, thereby changing the cooling intensity and realizing active intervention in the heat accumulation; the fully automatic closed-loop mode is as follows: the control unit (7) is configured to compare T_real with the preset target gas temperature T_target, and automatically output the adjustment signal to the refrigeration unit (6) through the control algorithm, dynamically changing its cooling power, so that T_real is stable near T_target, forming a complete temperature automatic control closed loop.

6. The intelligent gas circulation cooling system for SLM equipment as described in claim 5, characterized in that, T_real indicates that increased heat accumulation occurs when T_real continuously exceeds a set threshold.

7. The intelligent gas circulation cooling system for SLM equipment as described in claim 5, characterized in that, The specific parameters for adjusting the refrigeration unit (6) are: reducing the target temperature of the coolant or the flow rate of the coolant.

8. The intelligent gas circulation cooling system for SLM equipment as described in claim 5, characterized in that, The control algorithm is PID.

9. The intelligent gas circulation cooling system for SLM equipment as described in claim 5, characterized in that, The control unit adjusts the refrigeration unit according to the change of T_real, or dynamically optimizes the wind speed setpoint V_target.

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