Laser energy deposition spectrum signal acquisition device and method based on photomultiplier tube

Abstract

The present invention belongs to the field of additive manufacturing technology and discloses a device and method for collecting laser energy deposition spectrum signals based on photomultiplier tubes. A collimator is connected to the laser cladding head of a laser energy deposition forming system. The input end of a first single-channel optical fiber is connected to the output end of the collimator, and the output end of the first single-channel optical fiber is connected to the input end of a fiber optic splitter. The fiber optic splitter has at least two output ends, each of which is connected to a second single-channel optical fiber. The output end of each second single-channel optical fiber is connected to a narrowband filter. A photomultiplier tube is disposed behind each narrowband filter, and the output end of each photomultiplier tube is connected to a digital acquisition card. The present invention solves the problems of current spectrometers with low sampling frequencies, poor sensitivity in weak plasma conditions, weak effective spectral signals, external signal interference, and insufficient refinement capabilities of wide-band photoelectric sensors.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a laser energy deposition spectrum signal acquisition device and method based on a photomultiplier tube. Background Art

[0002] Laser energy deposition, also known as laser metal deposition, is an additive manufacturing technology with the characteristics of high energy density, low heat input and high forming efficiency. It can accelerate production and minimize material waste in various industries, including aerospace, automotive and biomedicine. The laser energy deposition process uses wire or powder as raw material and uses various heat sources such as laser, electron beam, arc and plasma for deposition energy input. Among various heat sources, laser has high flexibility, high energy density, low heat affected zone and precise heat input control, and has been widely used. However, the laser directed energy deposition process has the disadvantages of fast cooling speed (≈10 6 The technology's widespread application is severely hampered by defects such as high speed (K / s), large temperature gradients, and high thermal stresses during the manufacturing process, including stress, cracks, and unstable cladding quality. Existing "offline testing" methods, which address these quality challenges, are limited by high costs and long production cycles. The resulting "repetitive manufacturing" results in significant losses in human, material, and financial resources, and cannot meet the precision, low-cost, and high-reliability manufacturing requirements of high-end equipment.

[0003] Online detection technologies, including emission spectroscopy and infrared thermal imaging, offer advantages such as cost-effectiveness, high efficiency, and real-time performance. They have been widely used for defect monitoring in laser energy deposition (LD). These technologies are known as emission spectroscopy and infrared thermal imaging. Plasma emission spectroscopy is based on the principle that thermal energy from a liquid melt causes partial metal vaporization. The vaporized metal atoms are ionized by a heat source, such as a laser or arc, forming a plasma composed of free electrons, positive ions, and neutral particles above the melt pool. Complex thermal energy conversion occurs within the plasma, radiating different types of electromagnetic waves. These waves are collected by a spectrometer with dispersion capabilities as photon intensity signals at different wavelengths, representing the plasma spectrum signal. Spectral signals offer advantages such as high information content and high sensitivity. Compared to other signals such as images, arc spectroscopy offers advantages for detecting internal defects such as ablation, porosity, and cracks in additive manufacturing processes. However, traditional spectrometers, due to their low sampling frequency, struggle to effectively capture transient plasma spectrum signals generated by high-speed lasers. Furthermore, their sensitivity is poor in weak plasma conditions, making them susceptible to weak spectral signals and interference from external signals. In addition, traditional photoelectric sensors are mostly wide-band, lacking in refinement capabilities and unable to accurately sense the intensity of spectral lines of key elements. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a laser energy deposition spectral signal acquisition device and method based on a photomultiplier tube, which solves the problems of low sampling frequency of current spectrometers, which makes it difficult to effectively capture transient plasma spectral signals under the action of high-speed lasers, poor sensitivity under weak plasma, and prone to weak effective spectral signals and external signal interference, as well as insufficient refinement capability of wide-band photoelectric sensors.

[0005] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0006] According to a first aspect of the present invention, a laser energy deposition spectrum signal acquisition device based on a photomultiplier tube is provided, comprising a collimator, a first single-channel optical fiber, an optical fiber splitter, a second single-channel optical fiber, a narrow-band filter, a photomultiplier tube, and a digital acquisition card, wherein the collimator is connected to a laser cladding head of a laser energy deposition forming system, the input end of the first single-channel optical fiber is connected to the output end of the collimator, the output end of the first single-channel optical fiber is connected to the input end of the optical fiber splitter, the optical fiber splitter has at least two output ends, each output end of the optical fiber splitter is connected to a second single-channel optical fiber, the output end of each second single-channel optical fiber is connected to a narrow-band filter, the photomultiplier tube is arranged behind each narrow-band filter, and the output end of each photomultiplier tube is connected to the digital acquisition card.

[0007] In a possible implementation of the first aspect, the acquisition device also includes a filter connector, the filter connector includes a filter mounting seat connected to the input end of the photomultiplier tube, the filter mounting seat is provided with a receiving hole for accommodating a narrowband filter, the narrowband filter is installed in the receiving hole, and an optical fiber connector is provided at one end of the receiving hole away from the input end of the photomultiplier tube, and the output end of each second single-channel optical fiber is connected to the corresponding optical fiber connector.

[0008] In a possible implementation manner of the first aspect, the filter connector further includes a plastic gasket disposed in the accommodating through hole, and the plastic gasket is located on a side of the narrowband filter facing the input end of the photomultiplier tube.

[0009] In a possible implementation manner of the first aspect, the filter connector further includes a screw, and the filter mounting seat and the corresponding photomultiplier tube are connected using the screw.

[0010] In a possible implementation of the first aspect, the distance between the output end of the collimating mirror and the molten pool of the laser energy deposition forming system is 10 cm to 100 cm.

[0011] In a possible implementation manner of the first aspect, an angle between the collimating mirror and a horizontal plane is 20° to 60°.

[0012] In a possible implementation manner of the first aspect, the collimating lens and the laser cladding head are connected via a collimating lens fixing fixture.

[0013] In a possible implementation of the first aspect, the acquisition device further includes a photomultiplier tube power supply and an acquisition computer, each of the photomultiplier tubes is correspondingly connected to a photomultiplier tube power supply, and the input end of the acquisition computer is connected to the output end of the digital acquisition card.

[0014] In a possible implementation manner of the first aspect, the wavelength bands of the narrowband filters connected to the output end of each second single-channel optical fiber are different.

[0015] According to a second aspect of the present invention, a method for collecting spectral signals of laser energy deposition based on a photomultiplier tube is provided, comprising: a spectral signal generated during the laser energy deposition forming process enters from the input end of the collimator, the spectral signal after collimation by the collimator enters the fiber optic splitter through the first single-channel optical fiber, the fiber optic splitter divides the spectral signal into at least two spectral signals, each spectral signal is filtered by the corresponding narrow-band filter after passing through the second single-channel optical fiber, the spectral signal after filtering enters the corresponding photomultiplier tube, the photomultiplier tube converts the corresponding spectral signal into an electrical signal, and the digital acquisition card collects and stores the electrical signal.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] The present invention provides a laser energy deposition spectrum signal acquisition device based on a photomultiplier tube. By introducing a photomultiplier tube as a signal acquisition element and combining it with a digital acquisition card, the sampling frequency can be significantly improved. Compared with traditional spectrometers, the sampling frequency can be increased by 1000 times, ensuring that the signal acquisition device can accurately capture the rapid changes of transient signals during the laser energy deposition process, improving the accuracy and real-time performance of signal capture, and thus effectively solving the problem of low sampling frequency and inability to capture transient signals in traditional equipment. The photomultiplier tube has extremely high light sensitivity, and its photoelectric gain effect can reach 10 6 -10 8, compared with traditional spectrometers, the light sensitivity is improved by millions of times. At the same time, the introduction of the collimating mirror can greatly improve the transmission efficiency of the optical system and enhance the focusing ability of the light source. This combination enables the signal acquisition device of the present invention to successfully collect weak plasma signals, solving the problem that traditional spectrometers are difficult to collect weak signals. By using narrow-band filters in conjunction with photomultiplier tubes, the present invention can flexibly select the wavelength range of the input photomultiplier tube light, thereby obtaining accurate plasma spectrum information, so that the signal acquisition device of the present invention can improve the fine light collection capability by more than 100 times. By using low-cost photomultiplier tubes to replace traditional expensive spectrometers, the signal acquisition device of the present invention significantly reduces the equipment cost, reducing the cost of online monitoring technology for laser energy deposition by about 50 times, which will help promote the widespread application of laser energy deposition technology, reduce production costs, and improve production efficiency.

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the specific embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a structural schematic diagram of a laser energy deposition spectrum signal acquisition device based on a photomultiplier tube in use according to an embodiment of the present invention;

[0021] Figure 2 A three-dimensional diagram of a photomultiplier tube according to an embodiment of the present invention;

[0022] Figure 3 A three-dimensional diagram of the filter connector according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the assembly of the filter connector, narrowband filter, and photomultiplier tube according to an embodiment of the present invention;

[0024] Figure 5 This is a calibration diagram of element band spectrum lines in an embodiment of the present invention;

[0025] Figure 6 This is the cross section of the cladding track in Experiment 1 of the embodiment of the present invention;

[0026] Figure 7 This is the cross section of the cladding track in Experiment 2 of the embodiment of the present invention;

[0027] Figure 8 This is the cross section of the cladding track in Experiment 3 of the embodiment of the present invention;

[0028] Figure 9 This is a correlation analysis diagram of the dilution rate and the mean value of the key element spectral line ratio in the embodiment of the present invention.

[0029] In the figure: 1. Powder feeder; 2. Argon protection device; 3. Laser cladding head; 4. Collimator lens fixing fixture; 5. Collimator lens; 6. Fiber optic splitter; 7. Second single-channel optical fiber; 8. Filter connector; 81. Filter mounting seat; 82. Fiber optic connector; 83. Plastic gasket; 84. Screw; 9. Narrowband filter; 10. Photomultiplier tube; 11. Photomultiplier tube power supply; 12. Digital acquisition card; 13. Acquisition computer; 14. First single-channel optical fiber; 15. Substrate; 16. Forming workbench; 17. Printing workpiece; 18. Robotic arm; 19. Control cabinet host. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] like Figure 1 As shown, an embodiment of the present invention provides a laser energy deposition spectral signal acquisition device based on a photomultiplier tube, which is mainly intended to solve the problems that the current spectrometer has a low sampling frequency and is difficult to effectively capture the transient plasma spectral signal under the action of high-speed laser. At the same time, the sensitivity is poor under weak plasma, and it is easy to have weak effective spectral signals and external signal interference, as well as the problem of insufficient refinement capability of wide-band photoelectric sensors, thereby promoting the widespread application of laser energy deposition technology in the precision manufacturing of high-end equipment. The laser energy deposition spectrum signal acquisition device based on the photomultiplier tube includes a collimator 5, a first single-channel optical fiber 14, an optical fiber splitter 6, a second single-channel optical fiber 7, a narrow-band filter 9, a photomultiplier tube 10 and a digital acquisition card 12. The collimator 5 is connected to the laser cladding head 3 of the laser energy deposition forming system. The input end of the first single-channel optical fiber 14 is connected to the output end of the collimator 5, and the output end of the first single-channel optical fiber 14 is connected to the input end of the optical fiber splitter 6. The optical fiber splitter 6 has at least two output ends. Each output end of the optical fiber splitter 6 is connected to a second single-channel optical fiber 7, and the output end of each second single-channel optical fiber 7 is connected to a narrow-band filter 9. A photomultiplier tube 10 is arranged behind each narrow-band filter 9, and the output end of each photomultiplier tube 10 is connected to the digital acquisition card 12.

[0032] Specifically, the collimator 5 is connected to the laser cladding head 3 of the laser energy deposition forming system. Its primary function is to collimate the spectral signal radiated from the molten pool, ensuring that the spectral signal can be efficiently transmitted to the subsequent fiber optic system. The input end of the first single-channel optical fiber 14 is connected to the output end of the collimator 5, and is used to transmit the collimated spectral signal to the fiber optic splitter 6. The fiber optic splitter 6 receives the spectral signal from the first single-channel optical fiber 14 and divides it into several spectral signals to simultaneously collect spectral signals of multiple wavelengths. Each split spectral signal is transmitted to the narrowband filter 9 via the corresponding second single-channel optical fiber 7. The narrowband filter 9 is used to filter the spectral signal of a specific wavelength to extract the spectral feature of interest. It should be noted that the selection of the narrowband filter 9 should be determined based on the spectral features that may be generated during the laser energy deposition process and the analysis requirements. The photomultiplier tube 10 converts the filtered spectral signal into an electrical signal. The photomultiplier tube 10 has the characteristics of high sensitivity, low noise, and fast response, making it suitable for detecting weak spectral signals. In the present invention, a photomultiplier tube 10 is positioned behind each narrowband filter 9 to ensure accurate detection of each spectral signal. A digital acquisition card 12 is used to collect and store the electrical signals from the photomultiplier tube 10. The digital acquisition card 12 also has data storage and transmission capabilities.

[0033] In other words, during the laser energy deposition process, the spectral signal radiated from the molten pool enters the first single-channel optical fiber 14 through the collimator 5, and then is transmitted to the optical fiber splitter 6. The optical fiber splitter 6 divides the spectral signal into several paths, and each spectral signal is transmitted to the corresponding narrow-band filter 9 through the second single-channel optical fiber 7. The narrow-band filter 9 filters the corresponding spectral signal to extract the spectral features of interest. The selection of the narrow-band filter 9 needs to be determined according to the specific analysis requirements. The spectral signal after filtering enters the corresponding photomultiplier tube 10, and the photomultiplier tube 10 converts the spectral signal into an electrical signal. The digital acquisition card 12 collects the electrical signal from the photomultiplier tube 10 and stores it.

[0034] Through the above-mentioned embodiments, the present invention provides a laser energy deposition spectral signal acquisition device based on a photomultiplier tube. This device solves the problems that the current spectrometer has a low sampling frequency and is difficult to effectively capture the transient plasma spectral signal under the action of high-speed laser. At the same time, the sensitivity is poor under weak plasma, and it is easy to have weak effective spectral signals and external signal interference, as well as the problem of insufficient refinement capability of wide-band photoelectric sensors.

[0035] In one possible implementation, combining Figures 2 to 4As shown, the photomultiplier tube-based laser energy deposition spectrum signal acquisition device also includes a filter connector 8, which includes a filter mounting seat 81 connected to the input end of the photomultiplier tube 10. The filter mounting seat 81 is provided with a receiving hole for accommodating a narrowband filter 9. The narrowband filter 9 is mounted in the receiving hole. The end of the receiving hole away from the input end of the photomultiplier tube 10 is provided with a fiber connector 82. The output end of each second single-channel optical fiber 7 is connected to a corresponding fiber connector 82. In other words, the design of the filter connector 8 simplifies the connection between the narrowband filter 9, the second single-channel optical fiber 7, and the photomultiplier tube 10, thereby improving the stability of the device.

[0036] In one possible implementation, combining Figures 2 to 4 As shown, the filter connector 8 further includes a plastic gasket 83 disposed in the receiving through hole, and the plastic gasket 83 is located on the side of the narrowband filter 9 facing the input end of the photomultiplier tube 10. The plastic gasket 83 is used to prevent light leakage and improve the efficiency and accuracy of spectral signal collection.

[0037] Preferably, the filter connector 8 further includes a screw 84 , and the filter mounting base 81 and the photomultiplier tube 10 are connected by the screw 84 , so that the narrowband filter 9 can be easily disassembled and replaced.

[0038] In one implementation, the distance between the output end of the collimator 5 and the molten pool is 10 cm to 100 cm. This distance range ensures that the spectral signal can be fully diffused and effectively captured by the collimator 5, while avoiding excessive signal strength due to close distance or signal attenuation due to distance. The angle between the collimator 5 and the horizontal plane is 20° to 60°. This angle range ensures that the collimator 5 can effectively capture the spectral signal radiated from the molten pool, while avoiding signal attenuation or distortion caused by excessively large or small angles.

[0039] In one possible implementation, Figure 1 As shown, the collimator lens 5 is connected to the laser cladding head 3 via a collimator lens fixing fixture 4. The collimator lens fixing fixture 4 is used to firmly connect the collimator lens 5 to the laser cladding head 3, so that the collimator lens 5 and the laser cladding head 3 can move synchronously.

[0040] In one implementation, the acquisition device also includes a photomultiplier tube power supply 11 and an acquisition computer 13. Each photomultiplier tube 10 is connected to a corresponding photomultiplier tube power supply 11, and the acquisition computer 13 is connected to a digital acquisition card 12. The photomultiplier tube power supply 11 provides the required operating voltage and current for the photomultiplier tube 10, ensuring that the photomultiplier tube 10 can operate stably and efficiently. The acquisition computer 13 is connected to the digital acquisition card 12 and is used to receive, store, and analyze spectral signal data from the digital acquisition card 12. It should be understood that the acquisition computer 13 must be equipped with corresponding data acquisition and analysis software to perform operations such as real-time display, data storage, waveform analysis, and feature extraction of the spectral signal.

[0041] An embodiment of the present invention provides a method for collecting spectral signals of laser energy deposition based on a photomultiplier tube, specifically: during the laser energy deposition forming process, the generated spectral signal is first collected and collimated by a collimator 5. The collimated spectral signal is transmitted to the fiber optic splitter 6 through a first single-channel optical fiber 14, and the fiber optic splitter 6 divides the spectral signal into at least two paths. Each spectral signal is transmitted to the corresponding narrow-band filter 9 through a second single-channel optical fiber 7 for filtering, and only spectral signals of a specific wavelength band are allowed to pass. The filtered spectral signal enters the corresponding photomultiplier tube 10, and the photomultiplier tube 10 converts the spectral signal into an electrical signal. The digital acquisition card 12 acquires the electrical signal output by the photomultiplier tube 10, and stores the electrical signal data in the acquisition computer 13 for subsequent analysis.

[0042] The present invention will be explained in more detail below with reference to the embodiments.

[0043] This embodiment provides a photomultiplier tube-based laser energy deposition spectral signal acquisition device. Taking a three-path optical fiber splitter 6 as an example, the substrate 15 is made of 304 stainless steel, whose primary alloying element is FeI. The cladding powder is made of Stellite No. 6 cobalt-based high-temperature alloy, whose primary alloying element is CoII. A laser energy deposition forming system is used to form metal components with varying dilution rates. The corresponding spectral signals are acquired using the photomultiplier tube-based laser energy deposition spectral signal acquisition device. Feature parameters are extracted from the acquired spectral signals, and the extracted feature parameters are analyzed to determine whether they accurately characterize the dilution rate. This demonstrates the feasibility of the photomultiplier tube-based laser energy deposition spectral signal acquisition device for online monitoring of the dilution rate of laser energy deposited metal components.

[0044] like Figure 1The laser energy deposition forming system in this embodiment primarily includes a robot and its control system, a powder feeding system, a laser deposition system, an atmosphere protection system, and a forming workbench 16. The hardware for the robot and its control system primarily consists of a robotic arm 18 and a control cabinet host 19. The powder feeding system comprises a powder feeder 1 and its powder delivery pipeline. The laser deposition system comprises a laser cladding head 3 and its housing. The atmosphere protection system comprises an argon gas protection device 2. The tip of the robotic arm 18 is equipped with the laser cladding head 3. The powder delivery pipeline of the powder feeder 1 pneumatically transports powder along the robotic arm 18 to the laser cladding head 3. The argon gas protection device 2 delivers protective gas to the laser cladding head 3 via a pipeline to prevent oxidation and corrosion. The robotic arm 18, laser cladding head 3, argon gas protection device 2, and powder feeder 1 are uniformly coordinated and controlled by the control cabinet host 19. The forming workbench 16 is a rotatable base used to place a substrate 15, on which a printed workpiece 17 is formed.

[0045] The laser energy deposition spectrum signal acquisition device based on the photomultiplier tube includes a collimator fixing fixture 4, a collimator 5, a first single-channel optical fiber 14, an optical fiber splitter 6, three second single-channel optical fibers 7, three narrow-band filters 9, three filter connectors 8, three photomultiplier tubes 10, three photomultiplier tube power supplies 11, a digital acquisition card 12 and an acquisition computer 13; the input end of the first single-channel optical fiber 14 is connected to the output end of the collimator 5 to improve the directionality of the light beam and enhance the collection efficiency of the spectral signal, and the output end of the first single-channel optical fiber 14 is connected to the optical fiber splitter 6; the collimator 5 is fixed on the laser cladding head 3 through the collimator fixing fixture 4 to ensure that the acquisition angle of view remains relatively stationary with the laser cladding head 3 of the laser energy deposition forming system; the distance between the collimator 5 and the molten pool of the laser energy deposition forming system is 30 cm, and the angle with the horizontal plane is 40° to ensure a better acquisition angle of view; the collimator fixing fixture 4 The fixed fixture 4 includes two universal arms and two calipers; the input end of each second single-channel optical fiber 7 is connected to the output end of the corresponding optical fiber splitter 6, thereby evenly dividing the light into three groups for transmission; the filter connector 8 is composed of a filter mounting seat 81, an optical fiber connector 82, a plastic gasket 83 and a screw 84, and the optical fiber connector 82 adopts an SMA905 optical fiber connector; the narrowband filter 9 is fixed in the filter mounting seat 81; the optical fiber connector 82 of the filter connector 8 is connected to the output end of the second single-channel optical fiber 7; the filter connector 8 is fixed to the photomultiplier tube 10 by a screw 84, and the plastic gasket 83 can prevent light leakage; the photomultiplier tube 10 is connected to the photomultiplier tube power supply 11; the wavelengths of the three narrowband filters 9 are: 450nm±5 (FeI), 455nm±5 (CoⅡ) and 445nm±5 (background spectrum), and the diameters of the three narrowband filters 9 are all 12.7mm. The input end of the digital acquisition card 12 is connected to the output end of the photomultiplier tube 10 to obtain the collected data; the output end of the digital acquisition card 12 is connected to the input end of the acquisition computer 13.

[0046] like Figure 2 The photomultiplier tube 10 is shown. It should be understood that the interior of the photomultiplier tube 10 includes a photosensitive electrode, a photomultiplier tube housing, a gain element, and an output electrode. Its operating principle is that the photosensitive electrode receives a spectral signal. When a photon strikes the photosensitive electrode, it triggers a photoelectric effect, releasing electrons. The released electrons are accelerated by the electric field and strike the gain element, resulting in the release of secondary electrons, thereby forming an electron multiplication effect. As the electrons continue to collide and release, a large amount of electron flow is eventually generated. This flow passes through the output electrode, is converted into an electrical signal, and is sent to the digital acquisition card 12, completing the conversion process from spectral signal to electrical signal.

[0047] like Figure 4 The figure shows a schematic diagram of the photomultiplier tube 10 and the narrowband filter 9 being matched through the filter connector 8. Since the photomultiplier tube 10 can only collect the intensity of all input light in the full band and cannot separately correspond to the band, and the intensity of the excitation spectrum of certain key elements plays an important role in detecting the dilution rate and internal defects, it is necessary to use the selective transmittance of the narrowband filter 9 to realize the function of collecting the light intensity in the key band. The narrowband filter 9 cannot be directly integrated in front of the photomultiplier tube 10, so the filter connector 8 is designed to connect the output end of the second single-channel optical fiber 7, the narrowband filter 9 and the photomultiplier tube 10. The filter mounting seat 81 can accommodate a narrowband filter 9 with a diameter of 12.7 mm; the plastic gasket 83 can prevent the collected light signal from leaking outward, and also ensure that the collected signal is not affected by external ambient light.

[0048] The selection of three narrowband filters with 9 bands is based on the spectral signals collected by the three-channel spectrometer and the database of the National Bureau of Standards of the United States, such as Figure 5 As shown, Figure 5 The horizontal axis is wavelength, and the vertical axis is spectral intensity. FeI (449.488nm), CoⅡ (454.403nm) and background spectrum (445nm) are selected as element bands, and the bands of narrow-band filter 9 are: 450nm±5 (FeI), 455nm±5 (CoⅡ) and 445nm±5 (background spectrum).

[0049] When in use, a laser energy deposition spectral signal acquisition device based on a photomultiplier tube (PMT) is equipped with a laser cladding head 3 at the tip of a robotic arm 18. A powder feeder 1 conveys powder along the robotic arm 18 to the laser cladding head 3 via a pneumatic transmission method. An argon shielding device 2 delivers shielding gas to the laser cladding head 3 via a pipeline. The robotic arm 18, laser cladding head 3, argon shielding device 2, and powder feeder 1 are uniformly coordinated and controlled by a control cabinet host 19. The forming worktable 16 is a rotatable base for placing a substrate 15. The argon shielding device 2 neither chemically reacts with nor dissolves in the metal, making the metallurgical reaction in the molten pool during the printing process simple and easy to control, thus providing excellent conditions for forming high-quality components. The argon shielding gas flow rate is 20 g / min. The input end of the first single-channel optical fiber 14 is connected to the collimator 5 to improve the directionality of the light beam and enhance the signal collection efficiency, and the output end is connected to the fiber optic splitter 6; the collimator 5 is fixed to the laser cladding head 3 through the collimator fixing fixture 4 to ensure that the collection angle of view and the molten pool remain relatively stationary; the collimator 5 is 30 cm away from the molten pool and has an angle of 40° with the horizontal plane to ensure a better collection angle of view; the input end of the second single-channel optical fiber 7 is connected to the fiber optic splitter 6 to evenly divide the light into three groups for transmission; the filter connector 8 consists of a filter mounting seat 81, an optical fiber connector 82, a plastic gasket 83 and a screw 84; the narrowband filter 9 is fixed to the filter The filter mount 81 is mounted on a filter connector 8. The input end of the filter connector 8 is connected to the output end of the corresponding second single-channel optical fiber 7. The output end of the filter connector 8 is fixed to the photomultiplier tube 10 via screws 84. A plastic gasket 83 prevents light leakage. The photomultiplier tube 10 is connected to a photomultiplier tube power supply 11. The narrowband filter 9 has a diameter of 12.7 mm. The filter connector 8 is 22 mm long and wide, and 17 mm high. The collimator fixture 4 is 580 mm long. The forming workbench 16 is 50 mm thick. The substrate 15 measures 300 mm by 300 mm by 20 mm. The hole diameter of the plastic gasket 83 is 12.7 mm. The photomultiplier tube 10 has a spectral response band of 230 nm to 700 nm, a bandwidth of DC to 20 Hz, and a current-to-voltage conversion coefficient of 1 V / μa. The photomultiplier tube power supply 11 is connected to the power supply terminal of the photomultiplier tube 10. Its output voltage range is 0-1.8V. To ensure the sensitivity of the photomultiplier tube 10 while preventing damage from excessive light intensity, the voltage of the photomultiplier tube power supply 11 was fixed at 0.7V after experimental testing. The input terminal of the digital acquisition card 12 is connected to the output terminal of the photomultiplier tube 10. The digital acquisition card 12 has a maximum sampling rate of 204.8kHz, a dynamic range of 100dB, an amplitude accuracy of <0.1%, a frequency accuracy of <0.01%, and four acquisition channels.

[0050] It should be noted that the optical fiber splitter 6 includes but is not limited to three-way, four-way, five-way, ten-way, etc., depending on the number of elements to be analyzed and the wavelength.

[0051] The robot is a FANUC robot, and its forming workbench 16 is placed on the horizontal ground. The working mode of the FANUC robot in laser energy deposition is:

[0052] 1. Printing path: First, mark the starting point of printing on the forming workbench 16 and record its coordinates; determine the end point position according to the printing requirements and record its coordinates; program and define the path from the starting point to the end point in the robot control system; set the laser deposition printing speed, powder feeding amount, laser power and other parameters in the control system; set the cycle parameters according to the printing requirements; check and verify the set path in the control system to ensure that there are no obstacles and the path is reasonable; perform a dry run test to observe the movement of the robot arm 18 from the starting point to the end point to ensure the path is accurate.

[0053] 2. Printing Operation: Turn on the argon protection device 2 and powder feeder 1, ensure that all systems are working stably, and then start printing. After clicking "Start Print" on the control cabinet host 19, the laser and its laser cladding head 3 begin to operate, melting the Stellite No. 6 cobalt-based high-temperature alloy to form a molten pool on the surface of the 304 stainless steel substrate 15. After scanning one layer along the predetermined path, the laser and its laser cladding head 3 stop working, and the robotic arm 18 moves a distance. After the molten pool cools for a certain period of time, the robotic arm 18 returns to its initial height, and the laser cladding head 3 resumes laser output and scans the next layer along the predetermined path. This process repeats until all printing tasks are completed.

[0054] Adjust the process parameters, print cobalt-based alloy cladding paths with different dilution rates, and collect the corresponding spectral signals. Laser energy deposition parameters 1: powder feeding speed 20.4g / min, printing speed 12mm / s, laser energy 2200w; after cutting, grinding, polishing, and etching the printed cladding path, use an electron microscope to take a cross-sectional metallographic image (see Figure 1). Figure 6 The cross-sectional substrate 15 melting area is much larger than the powder cladding area, and the dilution rate is small; laser energy deposition parameters 2: powder feeding speed 20.4g / min, printing speed 12mm / s, laser energy 2600w; after cutting, grinding, polishing and etching the printed cladding path, the cross-sectional metallographic image is taken by electron microscope. Figure 7 The cross-sectional substrate 15 melting area is larger than the powder cladding area, and the dilution rate is small; laser energy deposition parameters 3: powder feeding speed 20.4g / min, printing speed 12mm / s, laser energy 3000w; after cutting, grinding, polishing and etching the printed cladding path, the cross-sectional metallographic image is taken by electron microscope. Figure 8 The melting area of ​​the cross-sectional substrate 15 is slightly larger than the powder cladding area, and the dilution rate value is relatively large.

[0055] The dilution rate is an important indicator for evaluating the quality of laser cladding forming and the bonding strength of the formed parts. It describes the proportion of the substrate 15 metal integrated into the cladding layer and reflects the degree of mixing of the substrate 15 metal and the cladding powder material in the cladding layer. The standard calculation method is shown in formula (1).

[0056] (1)

[0057] Where, is the dilution rate; is the cross-sectional area of ​​the sedimentary layer, is the melting area of ​​the substrate 15.

[0058] The dilution rates of the cladding channels of the three groups of experiments were calculated based on this formula. The results were: Experiment 1: 0.21; Experiment 2: 0.29; Experiment 3: 0.31.

[0059] The signal output of each photomultiplier tube 10 is connected to the three acquisition channel inputs of a digital acquisition card 12. The digital acquisition card 12 stores the electrical signals collected and converted by the photomultiplier tube 10. The input of the acquisition computer 13 is connected to the signal output of the digital acquisition card 12.

[0060] In this embodiment, a preliminary analysis of the collected spectral signals was performed. The collected spectral lines of specific elements not only confirm the presence of these elements in the molten pool, but their relative intensities can also, to a certain extent, represent the elemental quantities. Because the dilution rate affects the ratio of the components of the substrate 15 and the powder in the molten pool, it is possible to compare the peak intensities of the spectral lines of elements primarily present in the substrate 15 and those primarily present in the cladding powder to observe the corresponding relationship between the spectral line intensity and the dilution rate.

[0061] By calculating the spectral line intensity ratio of the representative elements of the substrate 15 and the cladding powder, the influence of the element content change on the spectral signal under different dilution rates is explored. i Calculate the representative elements of substrate 15 respectively S and representative elements of cladding powder P The spectral emission intensity changes dynamically, so Equation (3) calculates the mean value of the spectral line intensity of the representative element in each group of experiments to observe the general law.

[0062] (2)

[0063] (3)

[0064] Where, is the ratio of spectral line intensities; is the element line intensity represented by substrate 15; Cladding powder represents the elemental spectrum intensity; is the spectral line intensity of Fe; is the Co spectral line intensity; is the mean of the spectral line intensity ratios; n is the number of spectral line intensity acquisitions.

[0065] The spectral signal consists of a continuous background spectrum and spectral lines, and the radiation types of the two are different. It can be defined by the mathematical expression:

[0066] (4)

[0067] In the formula, represents the intensity of the collected spectrum, represents the background line intensity, Indicates the intensity of the excitation line.

[0068] The Fe and Co elemental spectral line intensities collected by the photomultiplier tube 10 include the background spectrum intensity, and the background spectrum needs to be subtracted.

[0069] Calculate the mean of the spectral line intensity ratio under the three groups of experiments and plot it as the vertical axis with the dilution rate as the horizontal axis. Figure 9 .from Figure 9 It can be seen that the dilution rate is positively correlated with the mean value of the spectral line intensity ratio, which verifies the feasibility of the laser energy deposition spectrum signal acquisition device based on photomultiplier tube for online monitoring of the dilution rate of laser energy deposition metal components.

[0070] This embodiment can utilize a photomultiplier tube 10 with low cost, high sensitivity (superior to traditional spectrometers), and a high sampling rate of hundreds of kHz (four orders of magnitude higher than traditional spectrometers) to collect plasma spectral radiation information representing elements of the substrate 15 and the cladding powder during the laser energy deposition process, especially enhanced collection of weak plasma spectral information at low laser energy. Based on this signal, anomaly detection, defect monitoring, and real-time quality assessment of the additive process are realized. This solves the problems of current spectrometers that cannot capture weak spectral information, have too low a sampling rate to match high-speed processing processes and refined element analysis, and have high commercial costs. Through the band design, element selection, and information fusion of multiple photomultiplier tubes 10, a low-cost and high-efficiency photomultiplier tube-based laser energy deposition spectral signal acquisition device and online quality monitoring are realized.

[0071] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0072] In the present invention, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can mean fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0073] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0074] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0075] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-mentioned embodiments, ordinary technicians in this field should understand that any technician familiar with this technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed by the present invention, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention.

Claims

1. A laser energy deposition spectrum signal acquisition device based on a photomultiplier tube, characterized in that: The invention comprises a collimator (5), a first single-channel optical fiber (14), an optical fiber splitter (6), a second single-channel optical fiber (7), a narrowband filter (9), a photomultiplier tube (10) and a digital acquisition card (12), wherein the collimator (5) is connected to a laser cladding head (3) of a laser energy deposition forming system, the angle between the collimator (5) and a horizontal plane is 20° to 60°, the distance between the output end of the collimator (5) and the molten pool of the laser energy deposition forming system is 10 cm to 100 cm, the input end of the first single-channel optical fiber (14) is connected to the output end of the collimator (5), and the first single-channel optical fiber (14) is connected to the output end of the collimator (5). The output end of the optical fiber splitter (4) is connected to the input end of the optical fiber splitter (6), the optical fiber splitter (6) has at least two output ends, each output end of the optical fiber splitter (6) is connected to a second single-channel optical fiber (7), the output end of each second single-channel optical fiber (7) is connected to a narrow-band filter (9), the wavelength bands of the narrow-band filters (9) connected to the output ends of each second single-channel optical fiber (7) are different, a photomultiplier tube (10) is arranged behind each narrow-band filter (9), and the output end of each photomultiplier tube (10) is connected to the digital acquisition card (12); The acquisition device further comprises a filter connector (8), the filter connector (8) comprising a filter mounting seat (81) connected to the input end of the photomultiplier tube (10), the filter mounting seat (81) being provided with an accommodating through hole for accommodating a narrowband filter (9), the narrowband filter (9) being mounted in the accommodating through hole, an optical fiber connector (82) being provided at one end of the accommodating through hole away from the input end of the photomultiplier tube (10), and the output end of each second single-channel optical fiber (7) being connected to a corresponding optical fiber connector (82); The filter connector (8) further comprises a plastic gasket (83) disposed in the receiving through hole, wherein the plastic gasket (83) is located on a side of the narrowband filter (9) facing the input end of the photomultiplier tube (10); The filter connector (8) further comprises a screw (84), and the filter mounting seat (81) and the corresponding photomultiplier tube (10) are connected by means of the screw (84).

2. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to claim 1, characterized in that: The collimating mirror (5) and the laser cladding head (3) are connected via a collimating mirror fixing fixture (4).

3. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to claim 1, characterized in that: The acquisition device further comprises a photomultiplier tube power supply (11) and an acquisition computer (13), each of the photomultiplier tubes (10) is correspondingly connected to one of the photomultiplier tube power supplies (11), and the input end of the acquisition computer (13) is connected to the output end of the digital acquisition card (12).

4. A method for collecting laser energy deposition spectrum signals based on a photomultiplier tube, characterized in that: A laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to any one of claims 1 to 3, comprising: The spectral signal generated during the laser energy deposition forming process enters from the input end of the collimator (5), and the spectral signal after being collimated by the collimator (5) enters the fiber optic splitter (6) through the first single-channel optical fiber (14). The fiber optic splitter (6) splits the spectral signal into at least two spectral signals. Each spectral signal passes through the second single-channel optical fiber (7) and is filtered by the corresponding narrow-band filter (9). The spectral signal after filtering enters the corresponding photomultiplier tube (10). The photomultiplier tube (10) converts the corresponding spectral signal into an electrical signal, and the digital acquisition card (12) acquires and stores the electrical signal.

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