A real-time monitoring system for powder nozzle status during laser powder feeding additive manufacturing

Abstract

A real-time monitoring system for the status of a powder nozzle in a laser powder feeding additive manufacturing process relates to a monitoring system for the status of a powder nozzle in a laser powder feeding additive manufacturing process. The present invention aims to solve the technical problems of low detection accuracy, complex installation process and narrow application range in the current method for judging nozzle blockage caused by powder splashing or powder accumulation in the powder feeding laser additive manufacturing process. When the nozzle is not blocked, the circuit is disconnected, and the current value actually obtained by the computer is set as the threshold value I min , when the measured current is less than I min When the current value is set as the threshold value I max , when the detected current value is greater than I max When the nozzle is blocked over a large area,

Description

Technical Field

[0001] The invention relates to a monitoring system for a powder nozzle state in a laser powder feeding additive manufacturing process. Background Art

[0002] As the most cutting-edge and difficult technology in the entire additive manufacturing system, metal material additive manufacturing technology is an important development direction of advanced manufacturing technology. Using laser as a heat source to manufacture metal materials has also become a research hotspot. Laser additive manufacturing technology can be divided into selective melting (SLM) and laser melting deposition (LMD). Among them, laser melting deposition technology has the advantages of high flexibility and no restrictions on forming size.

[0003] Generally, according to the type of material filling, it is divided into powder feeding laser additive manufacturing and wire feeding laser additive manufacturing. The basic principle is to use a high energy density laser beam to instantly heat the filling material to above the melting point to form a liquid molten pool, which then quickly solidifies and deposits layer by layer to form a workpiece. In the process of powder feeding laser cladding additive manufacturing, powder feeding speed, powder accuracy, powder delivery rate, etc. are key factors affecting the forming quality of the workpiece. Among them, the phenomenon of nozzle clogging caused by powder splashing or powder accumulation during the cladding process, which leads to instability or even interruption of the processing process, is an important problem that the industry urgently needs to solve. At present, the solution to this problem is generally to observe the nozzle state with human eyes, which has low reliability and may cause harm to the staff; some scholars also use pressure sensing or temperature sensing to detect the nozzle state, but this method has low detection accuracy, complex installation process and narrow scope of application. Therefore, it is of great engineering significance to develop a real-time monitoring system for the powder nozzle state in the process of laser powder feeding additive manufacturing. Summary of the invention

[0004] The present invention aims to solve the technical problems that the current method for judging nozzle blockage caused by powder splashing or powder accumulation in the powder feeding laser additive manufacturing process uses pressure sensing or temperature sensing to detect the nozzle status, which has low detection accuracy, complex installation process and narrow application range, and provides a real-time monitoring system for the powder nozzle status in the laser powder feeding additive manufacturing process.

[0005] The real-time monitoring system for the powder nozzle state in the laser powder feeding additive manufacturing process of the present invention is composed of a powder feeding nozzle, a nozzle state feedback circuit module and a computer 3;

[0006] The powder feeding nozzle is composed of an inner nozzle 1-2 and an outer nozzle 1-4. The inner nozzle 1-2 is arranged in the inner cavity of the outer nozzle 1-4 to form two cavities, namely, the inner cavity 1-1 and the outer cavity 1-3; the inner cavity 1-1 is a protective gas or laser beam channel; the outer cavity 1-3 is an annular conical cavity formed by the conical inner nozzle 1-2 and the conical outer nozzle 1-4, and is a powder conveying channel in the powder feeding laser melting deposition process;

[0007] The nozzle state feedback circuit module is composed of a first power supply 2-1, an electrical signal sensor 2-2, a sensor power supply 2-3, a data acquisition card 2-4 and a resistor 2-5; the positive and negative poles of the first power supply 2-1 are respectively connected to the inner nozzle 1-2 and the outer nozzle 1-4 to form a loop, and a protective resistor 2-5 is connected in series in the loop; the electrical signal sensor 2-2 is used to monitor the electrical signal in the loop formed by the first power supply 2-1, the inner nozzle 1-2 and the outer nozzle 1-4; the sensor power supply 2-3 supplies power to the electrical signal sensor 2-2; the data acquisition card 2-4 is used to collect and record the loop current monitored by the electrical signal sensor 2-2; the electrical signal sensor 2-2 is connected to the computer 3 through the data acquisition card 2-4, and the computer 3 collects the electrical signal in real time to realize the visualization of online monitoring of the powder feeding nozzle state.

[0008] The method of using the real-time monitoring system for the powder nozzle state in the laser powder feeding additive manufacturing process of the present invention is as follows:

[0009] 1. Conduct actual test to obtain threshold value: When the powder is stably transmitted, that is, the nozzle is not blocked, the circuit where the first power supply 2-1 is located is disconnected, and the current value at this time is obtained by computer 3 as I min ;

[0010] When the powder nozzle is blocked over a large area due to splashing or powder accumulation, the circuit where the first power source 2-1 is located forms a path, and the current value at this time can be obtained by the computer 3: max ;

[0011] 2. Practical application: When the measured current I≤I obtained by computer 3 min It is believed that there is no powder blockage and the powder transmission is stable;

[0012] When the measured current I≥I max When the nozzle is blocked, it is considered that a large area of ​​the nozzle is blocked, and the equipment is stopped for cleaning;

[0013] When the measured current I obtained by computer 3 is less than I max And greater than I min If the nozzle is partially clogged, attention should be paid.

[0014] The design principle of the present invention is based on the characteristics that metal powder, inner nozzle 1-2 and outer nozzle 1-4 can all be conductive. Figure 2 As shown, when the powder is stably transported, that is, the nozzle is not blocked, the circuit where the first power supply 2-1 is located is disconnected (because at this time the inner nozzle 1-2 and the outer nozzle 1-4 are not in contact and cannot conduct electricity), and the current detected by the electrical signal sensor 2-2 is almost 0. The current value actually obtained by the computer 3 is set as the threshold value I min , when the measured current is less than I min This indicates that there is no powder clogging ( Figure 2 The dashed box at the bottom of the figure);

[0015] When a large area of ​​the powder nozzle is clogged due to splashing or powder accumulation (the specific value of the large area is defined by the staff according to the actual situation), the circuit where the first power supply 2-1 is located forms a path (because the clogged metal powder connects the inner nozzle 1-2 and the outer nozzle 1-4 to form a circuit, which can conduct electricity); the current value actually obtained by the computer 3 is set as the threshold value I max , when the detected current value is greater than I max When the nozzle is blocked over a large area, Figure 2 ).

[0016] When the measured current I obtained by computer 3 is less than I max And greater than I min If the nozzle is partially clogged, attention should be paid.

[0017] Beneficial effects of the present invention:

[0018] 1. The present invention proposes a system for detecting the nozzle status through electrical signals to realize online monitoring of the powder delivery stability in the powder feeding laser additive manufacturing process;

[0019] 2. The system proposed by the present invention can greatly improve the stability of the laser powder feeding additive manufacturing process and reduce the problems of work interruption and low yield rate caused by nozzle blockage;

[0020] 3. The system of the present invention can be combined with a host computer such as a PLC to give an immediate alarm for possible instability problems during the processing process, while improving the safety of the entire process and better realizing the intelligence and automation of the manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the real-time monitoring system for the powder nozzle status during the laser powder feeding additive manufacturing process in Experiment 1;

[0022] Figure 2This is a schematic diagram of the design principle part of Experiment 1. DETAILED DESCRIPTION

[0023] Specific implementation method 1: This implementation method is a real-time monitoring system for the powder nozzle state in the laser powder feeding additive manufacturing process, which is specifically composed of a powder feeding nozzle, a nozzle state feedback circuit module and a computer 3;

[0024] The powder feeding nozzle is composed of an inner nozzle 1-2 and an outer nozzle 1-4. The inner nozzle 1-2 is arranged in the inner cavity of the outer nozzle 1-4 to form two cavities, namely, the inner cavity 1-1 and the outer cavity 1-3. The inner cavity 1-1 is a protective gas or laser beam channel; the outer cavity 1-3 is an annular conical cavity formed by the conical inner nozzle 1-2 and the conical outer nozzle 1-4, and is a powder conveying channel in the powder feeding laser melting deposition process.

[0025] The nozzle state feedback circuit module is composed of a first power supply 2-1, an electrical signal sensor 2-2, a sensor power supply 2-3, a data acquisition card 2-4 and a resistor 2-5; the positive and negative poles of the first power supply 2-1 are respectively connected to the inner nozzle 1-2 and the outer nozzle 1-4 to form a loop, and a protective resistor 2-5 is connected in series in the loop; the electrical signal sensor 2-2 is used to monitor the electrical signal in the loop formed by the first power supply 2-1, the inner nozzle 1-2 and the outer nozzle 1-4; the sensor power supply 2-3 supplies power to the electrical signal sensor 2-2; the data acquisition card 2-4 is used to collect and record the loop current monitored by the electrical signal sensor 2-2; the electrical signal sensor 2-2 is connected to the computer 3 through the data acquisition card 2-4, and the computer 3 collects the electrical signal in real time to realize the visualization of online monitoring of the powder feeding nozzle state.

[0026] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the material of the inner nozzle 1-2 is metal. The rest is the same as the specific implementation method 1.

[0027] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the material of the outer nozzles 1-4 is metal. The rest is the same as specific implementation method 1 or 2.

[0028] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the electric signal sensor 2-2 is a current sensor and is connected in series to the loop formed by the first power source 2-1, the inner nozzle 1-2 and the outer nozzle 1-4. The rest is the same as specific embodiments 1 to 3.

[0029] Specific implementation mode 5: This implementation mode is different from the specific implementation mode 1 in that the powder feeding nozzle is a coaxial nozzle or a side-axis nozzle. The rest is the same as the specific implementation mode 1.

[0030] Specific embodiment 6: This embodiment is different from specific embodiment 1 in that the electric signal sensor 2-2 is a voltage sensor and is connected in parallel to the loop formed by the first power supply 2-1, the inner nozzle 1-2 and the outer nozzle 1-4. The rest is the same as specific embodiment 1.

[0031] Specific implementation method 7: This implementation method is different from the specific implementation method 1 in that the data acquisition card 2-4 is a data acquisition card with a USB interface, has good compatibility, does not require an external power supply, is connected to the electrical signal sensor 2-2 through a screw terminal, can record current, voltage or resistance signals, and is compatible with C, C#, and Labview programming platforms. Other aspects are the same as the specific implementation method 1.

[0032] Specific implementation eight: This implementation differs from specific implementation four in that the data acquisition card 2-4 is connected to the computer 3 via a USB interface, and the current signal can be directly read using the Labview programming platform, and the current signal waveform can be displayed on the screen for staff to view through high-frequency sampling. Other aspects are the same as specific implementation four.

[0033] Specific embodiment 9: This embodiment is a method for using the real-time monitoring system for the state of a powder nozzle in the laser powder feeding additive manufacturing process in specific embodiment 4, specifically:

[0034] 1. Conduct actual test to obtain threshold value: When the powder is stably transmitted, that is, the nozzle is not blocked, the circuit where the first power supply 2-1 is located is disconnected, and the current value at this time is obtained by computer 3 as I min ;

[0035] When the powder nozzle is blocked over a large area due to splashing or powder accumulation, the circuit where the first power source 2-1 is located forms a path, and the current value at this time can be obtained by the computer 3: max ;

[0036] 2. Practical application: When the measured current I≤I obtained by computer 3 min It is believed that there is no powder blockage and the powder transmission is stable;

[0037] When the measured current I≥I max When the nozzle is blocked, it is considered that a large area of ​​the nozzle is blocked, and the equipment is stopped for cleaning;

[0038] When the measured current I obtained by computer 3 is less than I max And greater than I min If the nozzle is partially clogged, attention should be paid.

[0039] Specific embodiment 10: This embodiment is different from specific embodiment 9 in that the powder in step 1 is metal powder. The rest is the same as specific embodiment 9.

[0040] The present invention is verified by the following tests:

[0041] Experiment 1: This experiment is a real-time monitoring system for the powder nozzle status during laser powder feeding additive manufacturing. Figure 1 As shown, it is specifically composed of a coaxial powder feeding nozzle, a nozzle state feedback circuit module and a computer 3;

[0042] The coaxial powder feeding nozzle is composed of an inner nozzle 1-2 and an outer nozzle 1-4. The inner nozzle 1-2 is arranged in the inner cavity of the outer nozzle 1-4 to form two cavities, namely, the inner cavity 1-1 and the outer cavity 1-3; the inner cavity 1-1 is a laser beam channel; the outer cavity 1-3 is an annular conical cavity formed by the conical inner nozzle 1-2 and the conical outer nozzle 1-4, and is a powder conveying channel in the powder feeding laser melting deposition process; the material of the inner nozzle 1-2 is copper; the material of the outer nozzle 1-4 is copper;

[0043] The nozzle state feedback circuit module is composed of a first power supply 2-1, an electrical signal sensor 2-2, a sensor power supply 2-3, a data acquisition card 2-4 and a resistor 2-5; the positive and negative poles of the first power supply 2-1 are respectively connected to the inner nozzle 1-2 and the outer nozzle 1-4 to form a loop, and a protective resistor 2-5 is connected in series in the loop; the electrical signal sensor 2-2 is used to monitor the electrical signal in the loop formed by the first power supply 2-1, the inner nozzle 1-2 and the outer nozzle 1-4; the sensor power supply 2-3 supplies power to the electrical signal sensor 2-2; the data acquisition card 2-4 is used to collect and record the loop current monitored by the electrical signal sensor 2-2; the electrical signal sensor 2-2 is connected to the computer 3 through the data acquisition card 2-4, and the computer 3 collects the electrical signal in real time to realize the visualization of the online monitoring of the coaxial powder feeding nozzle state.

[0044] The electrical signal sensor 2-2 is a current sensor and is connected in series into a loop formed by the first power source 2-1, the inner nozzle 1-2 and the outer nozzle 1-4;

[0045] The data acquisition card 2-4 uses a USB interface data acquisition card, has good compatibility, does not require an external power supply, is connected to the electrical signal sensor 2-2 through a screw terminal, can record current signals, and is compatible with C, C#, and Labview programming platforms;

[0046] The data acquisition card 2-4 is connected to the computer 3 via a USB interface, and the current signal can be directly read using the Labview programming platform. The current signal waveform can be displayed on the screen for viewing by the staff through high-frequency sampling;

[0047] The method of using the real-time monitoring system for the powder nozzle state in the above-mentioned laser powder feeding additive manufacturing process is as follows:

[0048] 1. Conduct actual test to obtain threshold value: When the powder is stably transmitted, that is, the nozzle is not blocked, the circuit where the first power supply 2-1 is located is disconnected, and the current value at this time is obtained by computer 3 as I min ; The powder is a metal powder;

[0049] When the powder nozzle is blocked over a large area due to splashing or powder accumulation, the circuit where the first power source 2-1 is located forms a path, and the current value at this time can be obtained by the computer 3: max ;

[0050] 2. Practical application: When the measured current I≤I obtained by computer 3 min It is believed that there is no powder blockage and the powder transmission is stable;

[0051] When the measured current I≥I max When the nozzle is blocked, it is considered that a large area of ​​the nozzle is blocked, and the equipment is stopped for cleaning;

[0052] When the measured current I obtained by computer 3 is less than I max And greater than I min When the nozzle is partially blocked, it is considered that there is a local blockage and attention should be paid.

[0053] The design principle of this test is based on the fact that metal powder, inner nozzle 1-2 and outer nozzle 1-4 can all conduct electricity, such as Figure 2 As shown, when the powder is stably transported, that is, the nozzle is not blocked, the circuit where the first power supply 2-1 is located is disconnected (because at this time the inner nozzle 1-2 and the outer nozzle 1-4 are not in contact and cannot conduct electricity), and the current detected by the electrical signal sensor 2-2 is almost 0. The current value actually obtained by the computer 3 is set as the threshold value I min , when the measured current is less than I min This indicates that there is no powder clogging ( Figure 2 The dashed box at the bottom of the figure);

[0054] When a large area of ​​the powder nozzle is clogged due to splashing or powder accumulation (the specific value of the large area is defined by the staff according to the actual situation), the circuit where the first power supply 2-1 is located forms a path (because the clogged metal powder connects the inner nozzle 1-2 and the outer nozzle 1-4 to form a circuit, which can conduct electricity); the current value actually obtained by the computer 3 is set as the threshold value I max , when the detected current value is greater than I max When the nozzle is blocked over a large area, Figure 2 ).

[0055] When the measured current I obtained by computer 3 is less than I max And greater than I min If the nozzle is partially clogged, attention should be paid.

[0056] Beneficial effects of this test:

[0057] 1. This experiment proposes that a system that detects the nozzle status through electrical signals can realize online monitoring of the powder delivery stability during powder feeding laser additive manufacturing;

[0058] 2. The system proposed in this experiment can greatly improve the stability of the laser powder feeding additive manufacturing process and reduce the problems of work interruption and low yield rate caused by nozzle blockage;

[0059] 3. The system of this test can be combined with PLC and other host computers to give real-time alarms for possible instability problems in the processing process, while improving the safety of the entire process and better realizing the intelligence and automation of the manufacturing process.

Claims

1. A real-time monitoring system for the status of a powder nozzle during laser powder feeding additive manufacturing, characterized in that The real-time monitoring system for the powder nozzle state in the laser powder feeding additive manufacturing process is composed of a powder feeding nozzle, a nozzle state feedback circuit module and a computer (3); The powder feeding nozzle is composed of an inner nozzle (1-2) and an outer nozzle (1-4); the inner nozzle (1-2) is arranged in the inner cavity of the outer nozzle (1-4) to form two cavities, namely, the inner cavity (1-1) and the outer cavity (1-3); the inner cavity (1-1) is a protective gas or laser beam channel; the outer cavity (1-3) is an annular conical cavity formed by the conical inner nozzle (1-2) and the conical outer nozzle (1-4), and is a powder conveying channel in the powder feeding laser melting deposition process; The nozzle state feedback circuit module is composed of a first power supply (2-1), an electric signal sensor (2-2), a sensor power supply (2-3), a data acquisition card (2-4) and a resistor (2-5); the positive and negative poles of the first power supply (2-1) are respectively connected to the inner nozzle (1-2) and the outer nozzle (1-4) to form a loop, and a protective resistor (2-5) is connected in series in the loop; the electric signal sensor (2-2) is used to monitor the electric signal in the loop formed by the first power supply (2-1) and the inner nozzle (1-2) and the outer nozzle (1-4); the sensor power supply (2-3) supplies power to the electric signal sensor (2-2); the data acquisition card (2-4) is used to collect and record the loop current monitored by the electric signal sensor (2-2); the electric signal sensor (2-2) is connected to a computer (3) through the data acquisition card (2-4), and the computer (3) collects the electric signal in real time to realize the visualization of the online monitoring of the powder feeding nozzle state; The electric signal sensor (2-2) is a current sensor and is connected in series into a loop formed by the first power source (2-1), the inner nozzle (1-2) and the outer nozzle (1-4); The method for using the real-time monitoring system for the powder nozzle state in the laser powder feeding additive manufacturing process is as follows:

1. Conducting actual tests to obtain the threshold value: When the powder is stably transmitted, that is, the nozzle is not blocked, the circuit where the first power supply (2-1) is located is disconnected, and the current value at this time is obtained by the computer (3) as I min ; When the powder nozzle is blocked over a large area due to splashing or powder accumulation, the circuit where the first power source (2-1) is located forms a path, and the current value at this time can be obtained by the computer (3) as I max ; 2. Practical application: When the measured current I≤I obtained by computer (3) min It is believed that there is no powder blockage and the powder transmission is stable; When the measured current I ≥ I max When the nozzle is blocked, it is considered that a large area of ​​the nozzle is blocked, and the equipment is stopped for cleaning; When the measured current I obtained by the computer (3) is less than I max And greater than I min If the nozzle is partially clogged, attention should be paid.

2. A real-time monitoring system for powder nozzle status in a laser powder feeding additive manufacturing process according to claim 1, characterized in that The inner nozzle (1-2) is made of metal material.

3. The real-time monitoring system for powder nozzle status in laser powder feeding additive manufacturing process according to claim 1 is characterized in that The outer nozzle (1-4) is made of metal material.

4. The real-time monitoring system for powder nozzle status in laser powder feeding additive manufacturing process according to claim 1 is characterized in that The powder feeding nozzle is a coaxial nozzle or a side-axis nozzle.

5. The real-time monitoring system for powder nozzle status in laser powder feeding additive manufacturing process according to claim 1 is characterized in that The data acquisition card (2-4) is a data acquisition card using a USB interface.

6. The real-time monitoring system for powder nozzle status in laser powder feeding additive manufacturing process according to claim 1 is characterized in that The data acquisition card (2-4) is connected to the computer (3) via a USB interface, and uses a Labview programming platform to read the current signal, and displays the current signal waveform on the screen through high-frequency sampling.

7. The real-time monitoring system for powder nozzle status in laser powder feeding additive manufacturing process according to claim 1 is characterized in that The powder described in step 1 is metal powder.

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