Laser energy deposition spectral signal acquisition device and method based on photomultiplier

Abstract

The invention belongs to the technical field of additive manufacturing, and discloses a laser energy deposition spectral signal acquisition device and method based on a photomultiplier, a collimating mirror is connected to a laser cladding head of a laser energy deposition forming system, the input end of a first single-channel optical fiber is connected with the output end of the collimating mirror, and the output end of the first single-channel optical fiber is connected with the output end of a second single-channel optical fiber; the output end of the first single-channel optical fiber is connected with the input end of the optical fiber splitter, the optical fiber splitter is provided with at least two output ends, each output end of the optical fiber splitter is connected with a second single-channel optical fiber, the output end of each second single-channel optical fiber is connected with a narrow-band optical filter, a photomultiplier is arranged behind each narrow-band optical filter, and the photomultiplier is connected with the optical fiber splitter. And the output end of each photomultiplier is connected to a digital acquisition card. The invention solves the problems of low sampling frequency, poor sensitivity under weak plasma, weak effective spectral signal and external signal interference of the current spectrograph, and the problem of insufficient refinement capability of a broadband photoelectric sensor.

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 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 K / s), large temperature gradient, high thermal stress, and other characteristics. The defects of stress, cracks, unstable cladding quality in the manufacturing process seriously restrict the application and promotion of this technology. In view of the above quality problems, the existing "offline detection" method has limitations such as high cost and long cycle. The "repetitive manufacturing" caused by it will cause huge losses of manpower, material and financial resources, and cannot meet the precision-low-cost-high-reliability manufacturing needs of high-end equipment.

[0003] Online detection technology has the advantages of being economical, efficient, and real-time, and has been widely used in defect monitoring of laser energy deposition, including emission spectroscopy, infrared thermal imaging, etc. Among them, the principle of plasma emission spectrum generation is: part of the metal in the liquid molten pool evaporates under the action of thermal energy, and the evaporated metal atoms are ionized under the action of heat sources such as lasers or arcs, thereby forming a plasma composed of free electrons, positive ions, and neutral particles above the molten pool. Complex thermal energy conversion occurs inside the plasma, and different types of electromagnetic waves are radiated outward. The electromagnetic waves are collected as intensity signals of photons at different wavelengths by a spectrometer with a dispersion function, which is the plasma spectrum signal. Spectral signals have the advantages of large information content and strong sensitivity. Compared with other signals such as images, arc spectra have certain advantages in detecting internal defects such as ablation, pores, and cracks in the additive process. However, due to the low sampling frequency, traditional spectrometers are difficult to effectively capture transient plasma spectrum signals under the action of high-speed lasers. At the same time, the sensitivity is poor under weak plasma, and it is easy to have problems such as weak effective spectrum signals and external signal interference. 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 view of 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 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.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions: 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, an input end of the first single-channel optical fiber is connected to an output end of the collimator, an output end of the first single-channel optical fiber is connected to an 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, each output end of the 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.

[0006] 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 an accommodating through hole for accommodating a narrowband filter, the narrowband filter is installed in the accommodating through hole, and an optical fiber connector is provided at one end of the accommodating through hole away from the input end of the photomultiplier tube, and the output end of each of the second single-channel optical fibers is connected to the corresponding optical fiber connector.

[0007] In a possible implementation manner of the first aspect, the filter connector further includes a plastic gasket ring disposed in the accommodating through hole, and the plastic gasket ring is located on a side of the narrow-band filter facing an input end of the photomultiplier tube.

[0008] 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 by using the screw.

[0009] In a possible implementation manner 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.

[0010] In a possible implementation manner of the first aspect, an angle between the collimating mirror and a horizontal plane is 20° to 60°.

[0011] 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.

[0012] In a possible implementation of the first aspect, the acquisition device also 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.

[0013] In a possible implementation manner of the first aspect, the narrowband filters connected to the output ends of each of the second single-channel optical fibers have different wavelength bands.

[0014] 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.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 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 matching it with a digital acquisition card, the sampling frequency can be significantly improved. Compared with the traditional spectrometer, 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 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 collimator 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 light fine-grained acquisition 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 helps to promote the widespread application of laser energy deposition technology, reduce production costs, and improve production efficiency.

[0016] 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

[0017] In order to more clearly illustrate the technical solutions in the specific implementation modes of the present invention, the drawings required for use in the description of the specific implementation modes will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] 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; Figure 2 A three-dimensional diagram of a photomultiplier tube according to an embodiment of the present invention; Figure 3 A three-dimensional diagram of a filter connector according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the assembly of the filter connector, narrow-band filter and photomultiplier tube according to an embodiment of the present invention; Figure 5 This is a calibration diagram of element band spectrum lines in an embodiment of the present invention; Figure 6 This is the cross section of the cladding track of Experiment 1 of the embodiment of the present invention; Figure 7 This is the cross section of the cladding track of Experiment 2 of the embodiment of the present invention; Figure 8 This is the cross section of the cladding track of Experiment 3 of the embodiment of the present invention; Fig. 9 This is a correlation analysis diagram of the dilution rate and the mean value of the spectral line ratio of key elements in the embodiment of the present invention.

[0019] 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. optical fiber connector; 83. plastic gasket; 84. screw; 9. narrow-band 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

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] 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 a 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 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 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.

[0022] Specifically, the collimator 5 is connected to the laser cladding head 3 of the laser energy deposition forming system, and its main function is to collimate the spectral signal radiated from the molten pool to ensure that the spectral signal can be efficiently transmitted to the subsequent optical fiber 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 optical fiber splitter 6. The optical fiber splitter 6 receives the spectral signal from the first single-channel optical fiber 14 and divides it into several spectral signals so as to simultaneously collect spectral signals of multiple bands. Each split spectral signal is transmitted to the narrowband filter 9 through 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 features of interest. It should be noted that the selection of the narrowband filter 9 needs to be determined according to 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, and is suitable for detecting weak spectral signals. In the present invention, a photomultiplier tube 10 is arranged behind each narrowband filter 9 to ensure accurate detection of each spectrum signal. The digital acquisition card 12 is used to collect and store the electrical signals from the photomultiplier tube 10. At the same time, the digital acquisition card 12 also has data storage and transmission functions.

[0023] 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.

[0024] Through the above-mentioned implementation mode, the present invention provides a laser energy deposition spectral signal acquisition device based on a photomultiplier tube, which 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, and 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.

[0025] In one possible implementation, combining Figures 2 to 4As shown, the laser energy deposition spectrum signal acquisition device based on the photomultiplier tube also includes a filter connector 8, which includes a filter mounting seat 81 connected to the input end of the photomultiplier tube 10, and a receiving through hole for accommodating a narrowband filter 9 is provided on the filter mounting seat 81. The narrowband filter 9 is installed in the receiving through hole, and an optical fiber connector 82 is provided at one end of the receiving through hole away from the input end of the photomultiplier tube 10, and the output end of each second single-channel optical fiber 7 is connected to the corresponding optical fiber connector 82. In other words, the design of the filter connector 8 simplifies the connection between the narrowband filter 9 and the second single-channel optical fiber 7 and the photomultiplier tube 10, and improves the stability of the device.

[0026] In one possible implementation, combining Figures 2 to 4 As shown, the filter connector 8 also 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 collection efficiency and accuracy of the spectral signal.

[0027] Preferably, the filter connector 8 further includes a screw 84 , and the filter mounting seat 81 and the photomultiplier tube 10 are connected by the screw 84 , so that the narrow-band filter 9 can be easily disassembled and replaced.

[0028] In one achievable manner, the output end of the collimator 5 is 10 cm to 100 cm away from the molten pool. This distance range ensures that the spectral signal can be fully diffused and effectively captured by the collimator 5, while avoiding the signal being too strong due to being too close or the signal being attenuated due to being too far. 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 the signal being attenuated or distorted due to an angle that is too large or too small.

[0029] 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 as to achieve synchronous movement of the collimator lens 5 and the laser cladding head 3.

[0030] In one achievable manner, the acquisition device further 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 the digital acquisition card 12. The photomultiplier tube power supply 11 provides the required working voltage and current for the photomultiplier tube 10, ensuring that the photomultiplier tube 10 can work stably and efficiently. The acquisition computer 13 is connected to the digital acquisition card 12, and is used to receive, store and analyze the spectral signal data from the digital acquisition card 12. It should be understood that the acquisition computer 13 needs to be equipped with corresponding data acquisition software and analysis software to perform operations such as real-time display, data storage, waveform analysis and feature extraction of the spectral signal.

[0031] The 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 the 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 the 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 collects the electrical signal output by the photomultiplier tube 10, and stores the electrical signal data in the acquisition computer 13 for subsequent analysis.

[0032] The present invention will be explained in more detail below in conjunction with the embodiments.

[0033] This embodiment provides a laser energy deposition spectrum signal acquisition device based on a photomultiplier tube. The optical fiber splitter 6 takes three optical paths as an example. The substrate 15 is made of 304 stainless steel, the main alloying element of which is FeI. The cladding powder is made of Stellite No. 6 cobalt-based high-temperature alloy, the main alloying element of which is CoⅡ. The laser energy deposition forming system is used to form metal components with different dilution rates. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube is used to obtain the corresponding spectrum signal, extract characteristic parameters from the collected spectrum signal, and analyze whether the proposed characteristic parameters can accurately characterize the dilution rate, thereby verifying the feasibility of the laser energy deposition spectrum signal acquisition device based on a photomultiplier tube for online monitoring of the dilution rate of laser energy deposition metal components.

[0034] like Figure 1The laser energy deposition forming system in this embodiment mainly includes a robot and its control system, a powder feeding system, a laser deposition system, an atmosphere protection system and a forming workbench 16. Among them, the hardware of the robot and its control system mainly consists of a robot arm 18 and a control cabinet host 19; the powder feeding system consists of a powder feeder 1 and its powder conveying pipeline; the laser deposition system consists of a laser cladding head 3 and its shell; and the atmosphere protection system consists of an argon protection device 2. The tip of the robot arm 18 is equipped with a laser cladding head 3, and the powder conveying pipeline of the powder feeder 1 conveys the powder to the laser cladding head 3 by pneumatic transmission along the robot arm 18. The argon protection device 2 conveys protective gas to the laser cladding head 3 through a pipeline to avoid oxidation and corrosion. The robot arm 18, the laser cladding head 3, the argon protection device 2 and the powder feeder 1 are uniformly deployed and controlled by the control cabinet host 19. The forming workbench 16 is a rotatable base for placing a substrate 15, and the substrate 15 is used to make a printed workpiece 17.

[0035] 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 directivity 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 viewing angle remains relatively still 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 viewing angle; the collimator fixing fixture 4 is fixed on the laser cladding head 3 to ensure that the acquisition viewing angle remains relatively still 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 viewing angle; 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 so as to evenly divide 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 collection computer 13.

[0036] 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 working principle is that the photosensitive electrode receives a spectral signal. When a photon hits the photosensitive electrode, a photoelectric effect is triggered, releasing electrons. The released electrons are accelerated under the action of the electric field and hit the gain element, resulting in the release of secondary electrons, thereby forming an electron multiplication effect. With the continuous collision and release of electrons, a large amount of electron flow is eventually generated, which passes through the output electrode, is converted into an electrical signal, and is sent to the digital acquisition card 12, completing the conversion process of the spectral signal to the electrical signal.

[0037] 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 lights in the full band and cannot correspond to the corresponding bands respectively, and the intensity of the excitation spectrum of some key elements plays an important role in detecting the dilution rate and internal defects, it is necessary to use the selective transmission characteristics 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 be loaded with 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 the external ambient light.

[0038] The selection of three narrow-band filters with 9 bands is based on the spectral signals collected by the three-channel spectrometer and the US National Bureau of Standards database, such as Figure 5 As shown, Figure 5 The horizontal axis is wavelength, the vertical axis is spectral intensity, FeI (449.488nm), CoⅡ (454.403nm) and background spectrum (445nm) are selected as element bands, and then the bands of narrow-band filter 9 are: 450nm±5 (FeI), 455nm±5 (CoⅡ) and 445nm±5 (background spectrum).

[0039] When a laser energy deposition spectrum signal acquisition device based on a photomultiplier tube is used, the tip of the mechanical arm 18 is equipped with a laser cladding head 3, the powder feeder 1 conveying pipeline conveys the powder to the laser cladding head 3 by pneumatic transmission along the mechanical arm 18, and the argon protection device 2 conveys the protective gas to the laser cladding head 3 through the pipeline. The mechanical arm 18, the laser cladding head 3, the argon protection device 2, and the powder feeder 1 are uniformly deployed and controlled by the control cabinet host 19. The forming workbench 16 is a rotatable base for placing the substrate 15. Among them, the function of the argon protection device 2 is that it neither reacts chemically with the metal nor dissolves in the metal, making the metallurgical reaction of the molten pool in the printing process simple and easy to control, thus providing good conditions for forming high-quality components, and the argon protection gas flow rate is 20 / min. The input end of the first single-channel optical fiber 14 is connected to the collimator 5 to improve the directivity 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 on 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 static; 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 3 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; the narrowband filter 9 is fixed to the filter The filter connector 8 is in the mounting seat 81; 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 by screws 84, and the plastic gasket 83 can prevent light leakage; the photomultiplier tube 10 is connected to the photomultiplier tube power supply 11; wherein, the narrowband filter 9 has a diameter of 12.7mm, the filter connector 8 has a length and width of 22mm and a height of 17mm, the collimator lens fixing fixture 4 has a length of 580mm, the thickness of the forming workbench 16 is 50mm, the size of the substrate 15 is 300mm*300mm*20mm, and the diameter of the plastic gasket 83 hole is 12.7mm. The spectral response band of the photomultiplier tube 10 is 230nm-700nm, the bandwidth is DC-20Hz, and the current-voltage conversion coefficient is 1V / μa. The photomultiplier tube power supply 11 is connected to the power transmission end of the photomultiplier tube 10, and its output voltage range is 0-1.8v. In order to ensure the sensitivity of the photomultiplier tube 10 and prevent the photomultiplier tube 10 from being damaged by excessive light intensity, the voltage of the photomultiplier tube power supply 11 is fixed to 0.7v after experimental testing. The input end of the digital acquisition card 12 is connected to the output end of the photomultiplier tube 10. The maximum sampling rate of the digital acquisition card 12 is 204.8kHz, the dynamic range is 100dB, the amplitude accuracy is <0.1%, the frequency accuracy is <0.01%, and the acquisition channels are 4.

[0040] 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.

[0041] The robot is a FANUC robot, and its forming workbench 16 is placed on a horizontal ground. The working mode of the FANUC robot in laser energy deposition is: 1. Printing path: First, mark the starting point of printing on the forming workbench 16 and record its coordinates; determine the end point 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 printing speed, powder feeding amount, laser power and other parameters of laser deposition in the control system; set the cycle parameters according to printing needs; check and verify the set path in the control system to ensure that there are no obstacles and the path is reasonable; perform an idle run test to observe the movement of the robot arm 18 from the starting point to the end point to ensure the accuracy of the path.

[0042] 2. Printing operation: turn on the argon protection device 2 and the powder feeder 1, and start printing after ensuring that all systems are working stably; after clicking start printing on the control cabinet host 19, the laser and its laser cladding head 3 start working, 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 a layer according to the predetermined path, the laser and its laser cladding head 3 stop working, and the robot arm 18 moves a distance. After the molten pool cools down for a certain period of time, the robot arm 18 descends to the initial height, and the laser cladding head 3 outputs the laser again, and scans the next layer according to the predetermined path, and repeats this process until all printing tasks are completed.

[0043] Adjust the process parameters, print the cobalt-based alloy cladding with different dilution rates, and collect the corresponding spectral signals. Laser energy deposition parameter 1: powder feeding speed 20.4g / min, printing speed 12mm / s, laser energy 2200w; after cutting, grinding, polishing and etching the printed cladding, use an electron microscope to take a cross-sectional metallographic image (see Figure 1). Figure 6 The melting area of ​​the cross-sectional substrate 15 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 melting area of ​​the cross-sectional substrate 15 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. 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).

[0044] (1) In the formula, is the dilution rate; is the cross-sectional area of ​​the sedimentary layer, is the melting area of ​​the substrate 15.

[0045] Based on this formula, the dilution rates of the cladding channels of the three groups of experiments were calculated. The results were: Experiment 1: 0.21; Experiment 2: 0.29; Experiment 3: 0.31.

[0046] The signal output end of each photomultiplier tube 10 is respectively connected to the three acquisition channel input ends of the digital acquisition card 12, and the digital acquisition card 12 stores the electrical signals collected and converted by the photomultiplier tube 10. The input end of the acquisition computer 13 is connected to the signal output end of the digital acquisition card 12.

[0047] In this embodiment, the collected spectral signals are preliminarily analyzed. The collected spectra of specific elements can not only prove the presence of these elements in the molten pool, but their relative intensity can also represent the number of elements to a certain extent. Since the dilution rate will affect the ratio of the components of the substrate 15 and the powder components in the molten pool, it is possible to compare the peak intensities of the spectra of the elements mainly present in the substrate 15 and the elements mainly present in the cladding powder, and observe the corresponding relationship between the spectral line intensity and the dilution rate.

[0048] By calculating the spectral line intensity ratio of the representative elements of the substrate 15 and the cladding powder, the influence of the change of element content on the spectral signal under different dilution rates is explored. Formula (2) is used for each single spectrum in each group of experiments. i Calculate the representative elements of substrate 15 respectively S and representative elements of cladding powder P The spectral emission intensity changes dynamically, so formula (3) calculates the mean value of the spectral line intensity of each group of representative elements in order to observe universal laws.

[0049] (2) (3) In the formula, is the ratio of spectral line intensities; is the intensity of the element line represented by substrate 15; Cladding powder represents the elemental spectral line intensity; is the spectral line intensity of Fe; is the Co spectral line intensity; is the mean value of the spectral line intensity ratio; n is the number of spectral line intensity acquisitions.

[0050] 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 mathematical expression: (4) In the formula, represents the intensity of the collected spectrum, represents the background spectral line intensity, Represents the intensity of the excitation line.

[0051] The Fe and Co element spectral line intensities collected by the photomultiplier tube 10 include the background spectrum intensity, and the background spectrum needs to be subtracted.

[0052] Calculate the mean of the spectral line intensity ratios under the three groups of experiments and plot it with the dilution rate as the horizontal axis. Fig. 9 .from Fig. 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.

[0053] This embodiment can utilize a photomultiplier tube 10 with low cost, high sensitivity (better than 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 of representative elements of the substrate 15 and representative elements of the cladding powder during the laser energy deposition process, especially enhanced collection of weak plasma spectral information under low laser energy, and realize additive process abnormality detection, defect monitoring and real-time quality evaluation based on the signal, solving the problems of the current spectrometer being unable to capture weak spectral information, the sampling rate being too low to match high-speed processing and refined element analysis, and the high commercial cost. Through the band design, element selection and information fusion of multiple photomultiplier tubes 10, a low-cost and high-efficiency construction of a laser energy deposition spectral signal acquisition device based on photomultiplier tubes and online quality monitoring are realized.

[0054] 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 as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0055] In the present invention, unless otherwise clearly specified and limited, the terms "connected", "connection" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0057] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. 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 representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0058] 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 aforementioned embodiments, those of ordinary skill in the art should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the aforementioned embodiments within the technical scope disclosed by the present invention, or can easily conceive of changes, or make equivalent replacements for some of the technical features therein. Such 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 within 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 narrow-band filter (9), a photomultiplier tube (10) and a digital acquisition card (12); the collimator (5) is connected to a laser cladding head (3) of a 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); 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 one of the second single-channel optical fibers (7); the output end of each of the second single-channel optical fibers (7) is connected to one of the narrow-band filters (9); a photomultiplier tube (10) is arranged behind each of the narrow-band filters (9); and the output end of each of the photomultiplier tubes (10) is connected to the digital acquisition card (12).

2. 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 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 a receiving through hole for receiving a narrowband filter (9), the narrowband filter (9) being mounted in the receiving through hole, an optical fiber connector (82) being provided at one end of the receiving through hole away from the input end of the photomultiplier tube (10), and the output end of each of the second single-channel optical fibers (7) being connected to a corresponding optical fiber connector (82).

3. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to claim 2, characterized in that: The optical 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 narrow-band optical filter (9) facing the input end of the photomultiplier tube (10).

4. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to claim 2, characterized in that: The optical filter connecting member (8) further comprises a screw (84), and the optical filter mounting seat (81) and the corresponding photomultiplier tube (10) are connected by means of the screw (84).

5. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to claim 1, characterized in that: The distance between the output end of the collimating mirror (5) and the molten pool of the laser energy deposition forming system is 10 cm to 100 cm.

6. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to claim 5, characterized in that: The angle between the collimating mirror (5) and the horizontal plane is 20° to 60°.

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

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

9. The laser energy deposition spectrum signal acquisition device based on a photomultiplier tube according to claim 1, characterized in that: The wavelength bands of the narrowband filters (9) connected to the output ends of each of the second single-channel optical fibers (7) are different.

10. 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 as claimed in any one of claims 1 to 9, 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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