Monitoring signal compensation system and method for selective laser melting process

Abstract

The invention discloses a monitoring signal compensation system and method for a selective laser melting process. The monitoring module is additionally arranged in the selective laser melting equipment; a laser beam is divided into two paths after reaching the spectroscope through the collimator; one path of light beam reaches a power meter, the power meter converts a received optical signal into an electric signal and outputs the electric signal to a data processing module, and the stability and change of the laser power are monitored; the other light beam irradiates metal powder, and part of the light beam is absorbed by the metal powder to be molten to form a molten pool; a thermal radiation infrared beam emitted by a molten pool outwards is reflected by a dichroscope, filtered by an infrared narrow-band filter and transmitted by a focusing lens and then reaches a photodiode, and a corrected two-dimensional signal distribution diagram is obtained by aligning an output voltage signal with an actual printing position and compensating and correcting light intensity data; and finally, performing feature correspondence and analysis on the two-dimensional signal distribution diagram and the measured data of the power meter. The method can be widely applied to the field of SLM process monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of selective laser melting in additive manufacturing, and particularly to a monitoring signal compensation system and method for the selective laser melting process. Background Art

[0002] Selective Laser Melting (SLM) technology, as one of the key processes in Additive Manufacturing (AM), has received extensive attention in the fields of aerospace, biomedicine, mold manufacturing, etc. due to its ability to directly manufacture complex structural parts.

[0003] The SLM technology is based on the forming principle of layer-by-layer manufacturing and stacking. It melts metal powder layer by layer through a high-energy laser beam to achieve three-dimensional free forming of materials. This technology shows great advantages in preparing high-precision complex structural parts, shortening the production cycle, and reducing costs.

[0004] However, defects that are difficult to control will occur during the SLM process, such as metallurgical defects, warping, cracks, etc. These defects seriously affect the quality and performance of components. By collecting and analyzing these defect signals, the SLM process can be monitored in real time, and possible abnormalities can be detected and adjusted in a timely manner, thereby improving the stability of the manufacturing process and the product quality. Photodiodes are widely used in the monitoring process due to their high acquisition frequency. However, the optical signals received during coaxial monitoring will have large errors according to different printing positions. By monitoring the selective laser melting forming process, it can help optimize processing parameters and can also be used to diagnose the state of the molten pool. However, there is currently a lack of a technical solution for compensating monitoring signals in the selective laser melting process. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned disadvantages and deficiencies of the prior art, and provide a monitoring signal compensation system and method for the selective laser melting process. The present invention realizes the compensation and correction of the light intensity signal within the same system, not only solves the problems of accuracy error and inaccurate signal caused by the acquisition of photodiodes in the prior art, but also can monitor the laser power and the printing process through photodiodes and a power meter, with advantages such as high measurement accuracy, real-time measurement, simple operation, and low measurement cost.

[0006] The present invention is realized through the following technical solutions:

[0007] A monitoring signal compensation system for the selective laser melting process includes a continuous fiber laser 10, a collimator 9, a scanning galvanometer 2, a field lens 1, a process monitoring module, and a data processing module 11 that are connected in optical path sequence;

[0008] The process monitoring module is located between the optical paths of the collimator 9 and the scanning galvanometer 2; the process monitoring module is signal-connected to the data processing module.

[0009] The process monitoring module includes a dichroic mirror 3, an infrared narrowband filter 4, a focusing lens 5, a photodiode 6, a power meter 7, and a beam splitter 8;

[0010] The dichroic mirror 3 and the beam splitter 8 are sequentially located on the optical path between the collimator 9 and the scanning galvanometer 2; the dichroic mirror 3, the infrared narrowband filter 4, the focusing lens 5, and the photodiode 6 are sequentially optically signal-connected; the beam splitter 8 is optically signal-connected to the power meter 7;

[0011] The photodiode 6 and the power meter 7 are respectively electrically signal-connected to the data processing module 11.

[0012] The laser beam emitted by the continuous fiber laser 10 is equally divided into two beams of light by the beam splitter 8. One path is directly received by the power meter 7 for monitoring power changes; the other path passes through the scanning galvanometer 2 and the field lens 1 to the preset position of the forming cylinder 15 to perform selective melting on the metal powder to form a molten pool and form. At the same time, the thermal radiation infrared beam emitted from the forming position is sequentially reflected by the dichroic mirror 3, transmitted through the infrared narrowband filter 4 and the focusing lens 5, and then reaches the photodiode 6. The data processing module 11 correlates the actual scanning position coordinates of the scanning galvanometer 2 and the light intensity data collected by the photodiode 6, compensates and corrects the light intensity data signal, and finally analyzes the generated two-dimensional corrected image to realize the monitoring of the laser selective melting process.

[0013] The formula for compensating and correcting the light intensity data signal is as follows:

[0014] During the laser selective melting printing operation process, the relationship between the actual movement distances in the x direction and the y direction and the galvanometer angle is as follows:

[0015]

[0016] In the formula, x and y are the coordinates of the points on the processing plane, f is the focal length of the flat-field lens, and α and β are the deflection angles of the deflection mirror x and the deflection mirror y respectively;

[0017] When the galvanometer scans only in the x direction (β = 0) or in the y direction (α = 0), the relationship between the scanning position coordinates and the galvanometer deflection angle can be simplified as:

[0018] x = 2fα

[0019] y = 2fβ

[0020] The relationship between the light radiation received by the deflection mirror x in the scanning galvanometer 2 and the deflection angle changes as follows:

[0021]

[0022] Among them, σ is the molten pool radiation angle that the deflecting mirror x can receive, and θ is the latitude angle of the coordinate on the deflecting mirror x with the molten pool as the center of the sphere. is the longitude angle of the coordinate on the deflecting mirror x with the molten pool as the center of the sphere;

[0023] It is obtained that the area receiving radiation is:

[0024]

[0025] Since the light received by the deflecting mirror x needs to be reflected by the deflecting mirror y to the area that the photodiode can receive, the light intensity area S out is simplified to:

[0026] S out = S cos 2α cos 2β

[0027] Taking the position with the maximum light intensity on the printing plane as the reference, the light intensity of the remaining areas is calibrated as:

[0028]

[0029] Among them, E1 is the light intensity at the position that needs to be compensated, and S max is the area of the deflecting mirror x receiving radiation when the photodiode receives the maximum light intensity, S1 is the area of the deflecting mirror x receiving radiation at the position that needs to be compensated, and α max is the deflection angle of the deflecting mirror x when the photodiode receives the maximum light intensity, α1 is the deflection angle of the deflecting mirror x at the position that needs to be compensated, and β max is the deflection angle of the deflecting mirror y when the photodiode 6 receives the maximum light intensity, and β1 is the deflection angle of the deflecting mirror y at the position that needs to be compensated.

[0030] The splitting ratio of the beam splitter 8 is 1:1.

[0031] The shortest transmission wavelength of the dichroic mirror 3 is greater than 1000 nm and less than 1064 nm;

[0032] The shortest reflection wavelength of the dichroic mirror 3 is less than 800 nm;

[0033] The central wavelength of the infrared narrowband filter 4 is 900 nm.

[0034] The wavelength of the laser generated by the continuous fiber laser 10 is 1064 nm.

[0035] A method for compensating the laser selective melting process monitoring signal is as follows:

[0036] S1. Additive manufacturing: A part of the laser emitted by the continuous fiber laser is selectively irradiated on the powder bed through a collimator, a galvanometer scanner, and a field lens to form a molten pool for melting and forming;

[0037] S2. Power meter acquires data: The power meter receives another part of the laser emitted by the continuous fiber laser and performs photoelectric conversion on it to obtain a voltage signal;

[0038] S3. Monitor power change: The data processing module analyzes the obtained voltage signal and judges the stability and change of power;

[0039] S4. Collect molten pool radiation signal: The thermal radiation infrared beam emitted by the molten pool is reflected by the dichroic mirror 3, and after passing through the infrared narrow-band filter and the focusing lens in sequence, it reaches the photodiode and converts the signal into a voltage signal and outputs it to the data processing module;

[0040] S5. Data alignment; The data processing module 11 corresponds the voltage signal of the photodiode 6 received with the real-time scanning position information of the scanning galvanometer 2 to obtain the two-dimensional distribution map of the original signal;

[0041] S6. Data compensation: First, obtain the relationship between the actual movement distances in the x and y directions and the galvanometer angle during the printing process:

[0042]

[0043] Then, obtain the relationship between the change of the light radiation received by the deflecting mirror x in the galvanometer group with the deflection angle:

[0044]

[0045] The received radiation area is:

[0046]

[0047] Since the light received by the deflecting mirror x needs to be reflected by the deflecting mirror y to the area that can be received by the photodiode 6, the light intensity area S out Can be simplified to:

[0048] S out = S cos 2αcos 2β

[0049] Finally, taking the position with the maximum light intensity on the printing plane as the reference, the light intensity of the remaining areas can be calibrated to:

[0050]

[0051] S7, data alignment after compensation: the data processing module 11 matches the compensated voltage signal of the photodiode 6 with the real-time scanning position information of the scanning galvanometer 2 to obtain a two-dimensional distribution diagram of the compensated signal;

[0052] S8. Data fusion: Analyze the two-dimensional distribution diagram of the compensated signal with the power meter measurement data to realize the monitoring of the laser selective melting process.

[0053] Compared with the prior art, the present invention has the following advantages and effects:

[0054] The present invention integrates the process monitoring technology and the laser selective melting technology into one, and can realize high-precision and high-real-time printing process monitoring during the laser selective melting molding process.

[0055] The present invention is based on two detectors, a photodiode and a power meter. The photodiode and the power meter share the same optical system with the laser. Coaxial monitoring is achieved through laser optics and precise positioning, which is conducive to obtaining high local resolution and fast scanning rate, and improving the accuracy and reliability of the monitoring results.

[0056] The present invention divides the laser into two equal paths by using a beam splitter, thus avoiding disassembly of the system during the process of measuring the molten pool emissivity, thereby greatly improving efficiency and accuracy.

[0057] The light intensity compensation correction method proposed in the present invention can eliminate the influence of the forming position angle on the molten pool radiation received by the photodiode due to the coaxial installation, greatly improving the accuracy of the photodiode process monitoring. It has the advantages of high measurement accuracy, real-time measurement, simple operation and low measurement cost.

[0058] The technical means of the present invention are simple and easy to implement, and ingeniously avoid the problems of precision error and signal inaccuracy caused by traditional photodiode acquisition. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The present invention is a schematic diagram of the structure of the monitoring signal compensation system used in the laser selective melting process.

[0060] Figure 2 yes Figure 1 Schematic diagram of the deflection of the scanning galvanometer.

[0061] Figure 3 It is a comparison diagram of the original light intensity signal distribution diagram monitored during the laser selective melting process and the light intensity signal distribution diagram after compensation correction.

[0062] Reference Numerals: 1 - field lens; 2 - galvanometer scanner; 3 - dichroic mirror; 4 - infrared narrow-band filter; 5 - focusing lens; 6 - photodiode; 7 - power meter; 8 - beam splitter; 9 - collimator; 10 - continuous fiber laser; 11 - data processing module; 12 - powder spreading vehicle; 13 - guide rail; 14 - powder cylinder; 15 - forming cylinder. Detailed Embodiment

[0063] The present invention will be further described in detail below with reference to specific embodiments.

[0064] As Figures 1-3 shown, the present invention discloses a monitoring signal compensation system for the selective laser melting process, including a continuous fiber laser 10, a collimator 9, a galvanometer scanner 2, a field lens 1, a process monitoring module, and a data processing module 11 that are optically connected in sequence;

[0065] The process monitoring module is located between the optical paths of the collimator 9 and the galvanometer scanner 2; the process monitoring module is signal-connected to the data processing module.

[0066] The process monitoring module includes a dichroic mirror 3, an infrared narrow-band filter 4, a focusing lens 5, a photodiode 6, a power meter 7, and a beam splitter 8;

[0067] The dichroic mirror 3 and the beam splitter 8 are sequentially located on the optical path between the collimator 9 and the galvanometer scanner 2; the dichroic mirror 3, the infrared narrow-band filter 4, the focusing lens 5, and the photodiode 6 are optically connected in sequence; the beam splitter 8 is optically connected to the power meter 7;

[0068] The photodiode 6 and the power meter 7 are respectively electrically connected to the data processing module 11.

[0069] A powder spreading vehicle 12, a guide rail 13, a powder cylinder 14, and a forming cylinder 15 are arranged in the forming cavity. The powder spreading vehicle 12 is used to spread metal powder onto the forming cylinder 15. The continuous fiber laser 10 is used to generate laser light. After being collimated by the collimator 9, deflected in direction by the galvanometer scanner 2, and passing through the field lens 1, the laser light irradiates the metal powder. Part of the energy is absorbed by the metal powder to melt it and form a molten pool, and layer by layer reciprocation is carried out to form a formed part;

[0070] After the laser beam emitted by the continuous fiber laser 10 reaches the beam splitter 8 through the collimator 9, the beam splitter 8 divides the beam into two paths; one path of the beam directly reaches the power meter 7, and the other path of the beam passes through the dichroic mirror 3, the galvanometer scanner 2, and the field lens 1 and then reaches the metal powder to be formed; after the metal powder absorbs the laser energy to form a molten pool and emits a thermal radiation infrared beam outward, it is reflected by the dichroic mirror 3 and then passes through the infrared narrow-band filter 4 and the focusing lens 5 to reach the photodiode 6 for monitoring before and after each layer of printing.

[0071] The data processing module compares the actual laser power emitted by the continuous fiber laser 10 with the voltage value measured by the power meter 7, analyzes the change in voltage amplitude at different powers and monitors the stability of the power. The signal monitored by the photodiode 6 is corresponded to the actual scanning position information of the scanning galvanometer 2 to obtain a two-dimensional light intensity signal distribution map, and the signal is corrected according to the light intensity compensation correction formula to generate a compensated actual two-dimensional light intensity signal distribution map, realizing real-time monitoring of the laser selective melting process.

[0072] As Figure 1 shown, the operation process of the laser selective melting process monitoring signal compensation system is as follows: The powder spreading vehicle 12 in the forming cavity obtains the metal powder in the powder cylinder 14 and spreads the metal powder on the preset position of the forming cylinder 15. The laser beam selectively melts the powder on the plane of the forming cylinder 15 to form a molten pool. After the metal solidifies, powder spreading continues, melting continues, and finally a formed part is formed. Among them, as an alternative implementation, the powder spreading vehicle 12 scrapes the powder in the powder cylinder 14 to the upper part of the forming cylinder 15 and levels it through the scraper below it. For each layer formed, the powder cylinder 14 moves up one layer, the forming cylinder 15 moves down one layer, and the powder spreading vehicle 12 spreads the powder once, and the cycle repeats. Refer to Figure 1 , in this embodiment, the powder spreading device includes a powder spreading guide rail 13 and a powder spreading vehicle 12. The powder spreading vehicle 12 is used to scrape and carry the metal powder from the powder cylinder 14 and reach the forming cylinder 15 through the powder spreading guide rail 13 for powder spreading.

[0073] In some embodiments, the emission of the laser can be controlled by the laser head, and the irradiation position of the laser can be changed so that the laser irradiates different positions on the forming platform; in other embodiments, the forming platform can be moved in two dimensions so that the laser irradiates different positions on the forming platform.

[0074] The laser beam emitted by the continuous fiber laser 10 is equally divided into two beams of light by the beam splitter 8. One beam is directly received by the power meter 7 for monitoring power changes, and the other beam reaches the preset position of the forming cylinder 15 through the scanning galvanometer 2 and the field lens 1 to melt the metal powder to form a molten pool and form. At the same time, the thermal radiation infrared beam emitted from the forming position is reflected by the dichroic mirror 3, transmitted through the infrared narrow-band filter 4 and the focusing lens 5, and reaches the photodiode 6. The data processing module corresponds the actual scanning position coordinates of the scanning galvanometer 2 and the light intensity data collected by the photodiode, compensates and corrects it, and finally analyzes the generated two-dimensional corrected image to realize the monitoring of the laser selective melting process.

[0075] The calculation formula for light intensity signal compensation and correction is as follows:

[0076] During the printing process, the relationship between the actual moving distances in the x and y directions and the galvanometer angle is as follows:

[0077]

[0078] In the formula, x and y are the coordinates of points on the processing plane, f is the focal length of the flat-field lens, α and β are the deflection angles of the deflection mirror x and the deflection mirror y respectively;

[0079] When the galvanometer scans only in the x direction (β = 0) or in the y direction (α = 0), the relationship between the scanning position coordinates and the galvanometer deflection angle can be simplified as:

[0080] x = 2fα

[0081] y = 2fβ

[0082] The relationship between the light radiation received by the deflection mirror x in the scanning galvanometer 2 and the deflection angle is as follows:

[0083]

[0084] Among them, σ is the radiation angle of the molten pool that the deflection mirror x can receive, θ is the latitude angle of the coordinates on the deflection mirror x with the molten pool as the center of the sphere, is the longitude angle of the coordinates on the deflection mirror x with the molten pool as the center of the sphere;

[0085] It can be obtained that the area receiving radiation is:

[0086]

[0087] Since the light received by the deflection mirror x needs to be reflected by the deflection mirror y into the area that the photodiode can receive, the light intensity area S out can be simplified as:

[0088] S out = S cos 2αcos 2β

[0089] Therefore, taking the position with the maximum light intensity on the printing plane as the reference, the light intensity of the remaining areas can be calibrated as:

[0090]

[0091] Among them, E1 is the light intensity at the position that needs to be compensated, S max is the area of the deflection mirror x receiving radiation when the photodiode receives the maximum light intensity, S1 is the area of the deflection mirror x receiving radiation at the position that needs to be compensated, α max is the deflection angle of the deflection mirror x when the photodiode receives the maximum light intensity, α1 is the deflection angle of the deflection mirror x at the position that needs to be compensated, β maxθ is the deflection angle of the deflection mirror y when the maximum light intensity is received by the photodiode, and β1 is the deflection angle of the deflection mirror y at the required compensation position.

[0092] In the present invention, the laser is equally divided into two paths by the beam splitter 8, avoiding the disassembly of the system during the measurement of the radiation rate of the molten pool, and greatly improving the efficiency and accuracy.

[0093] See Figure 1 , the laser emitted by the continuous fiber laser 10 passes through the collimator 9 for collimation, the beam splitter 8 for transmission, the dichroic mirror 3, the scanning galvanometer 2 for position adjustment, and the field lens 1 for focusing in sequence, and then reaches the forming cylinder 15.

[0094] The continuous fiber laser 10 and the process monitoring device share a set of field lens 1 and scanning galvanometer 2, effectively reducing the cost. On the optical path of the laser emitted by the continuous fiber laser 10, the laser passes through the collimator 9 for collimation, then passes through the beam splitter 8 for transmission, and then passes through the dichroic mirror 3, the scanning galvanometer 2 and the field lens 1 in sequence to reach the forming cylinder 15 to heat and melt the metal powder.

[0095] As an optional implementation manner, the splitting ratio of the beam splitter 8 of the present invention is 1:1.

[0096] As an optional implementation manner, the shortest transmission wavelength of the dichroic mirror 3 of the present invention is greater than 1000 nm and less than 1064 nm.

[0097] As an optional implementation manner, the shortest reflection wavelength of the dichroic mirror 3 of the present invention is less than 800 nm.

[0098] As an optional implementation manner, the central wavelength of the infrared narrowband filter 4 of the present invention is 900 nm.

[0099] As an optional implementation manner, the wavelength of the laser generated by the continuous fiber laser 10 of the present invention is 1064 nm.

[0100] The monitoring process of the selective laser melting process of the present invention can be achieved through the following steps: The laser beam irradiates onto the beam splitter, dividing the beam into two paths; one path of the beam reaches the power meter, and the other path of the beam irradiates onto the metal powder after passing through the galvanometer and the field lens, and part of the beam is absorbed by the metal powder to melt it and form a molten pool; the power meter converts the received optical signal into a voltage signal and transmits it to the data processing module for monitoring the power stability of the laser emitted by the continuous fiber laser and the magnitude change of the laser power. The thermal radiation infrared beam emitted by the molten pool is reflected by the dichroic mirror, filtered by the infrared narrowband filter, and transmitted through the focusing lens, and then reaches the photodiode to collect the molten pool radiation signal in real time. The data processing module corresponds the optical intensity signal collected by the photodiode with the position coordinates scanned by the scanning galvanometer in real time, and corrects the optical signal according to the optical intensity compensation correction formula to obtain the two-dimensional distribution map of the corrected optical intensity signal. Finally, the two-dimensional distribution map of the optical intensity signal is analyzed to realize the monitoring of the selective laser melting process.

[0101] The following combines Figures 1-3 to specifically elaborate on the monitoring process during the selective laser operation process.

[0102] S1. Additive manufacturing: Part of the laser emitted by the continuous fiber laser passes through the collimator, galvanometer, and field lens and is selectively irradiated on the powder bed to form a molten pool for melting and forming.

[0103] S2. The power meter obtains data: The power meter receives another part of the laser emitted by the continuous fiber laser and performs photoelectric conversion on it to obtain a voltage signal.

[0104] S3. Monitor power change: The data processing module analyzes the obtained voltage signal and judges the power stability and change.

[0105] S4. Collect the molten pool radiation signal: The thermal radiation infrared beam emitted by the molten pool is reflected by the dichroic mirror 3, passes through the infrared narrowband filter and the focusing lens in sequence, and then reaches the photodiode and converts the signal into a voltage signal and outputs it to the data processing module.

[0106] S5. Data alignment; The data processing module corresponds the voltage signal of the photodiode received with the real-time scanning position information of the scanning galvanometer to obtain the two-dimensional distribution map of the original signal.

[0107] S6. Data compensation: First, obtain the relationship between the actual movement distances in the x and y directions during the printing process and the galvanometer angle:

[0108]

[0109] Then, obtain the relationship between the change in the light radiation received by the deflecting mirror x in the galvanometer group from the molten pool and the deflection angle:

[0110]

[0111] Furthermore, the area receiving radiation is obtained as follows:

[0112]

[0113] Since the light received by the deflection mirror x needs to be reflected by the deflection mirror y into the area that can be received by the photodiode, the light intensity area S that the photodiode can receive out can be simplified to:

[0114] S out = S cos 2α cos 2β

[0115] Finally, taking the position with the maximum light intensity on the printing plane as the reference, the light intensity of the remaining areas can be calibrated to:

[0116]

[0117] S7. Data alignment after compensation: The data processing module corresponds the compensated voltage signal of the photodiode with the real-time scanning position information of the scanning galvanometer to obtain a two-dimensional distribution diagram of the compensated signal;

[0118] S8. Data fusion: Analyze the two-dimensional distribution diagram of the compensated signal and the measurement data of the power meter to realize the monitoring of the laser selective melting process.

[0119] As described above, the present invention can be preferably realized.

[0120] The implementation manners of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement manners and are all included in the protection scope of the present invention.

Claims

1. A monitoring signal compensation system for a laser selective melting process, comprising a continuous fiber laser (10), a collimator (9), a scanning galvanometer (2) and a field lens (1) connected in sequence in an optical path; characterized in that: It also includes a process monitoring module and a data processing module (11); The process monitoring module is located between the collimator (9) and the optical path of the scanning galvanometer (2); and the process monitoring module is signal-connected to the data processing module.

2. The monitoring signal compensation system for selective laser melting process according to claim 1, characterized in that: The process monitoring module comprises a dichroic mirror (3), an infrared narrow-band filter (4), a focusing lens (5), a photodiode (6), a power meter (7) and a spectroscope (8); The dichroic mirror (3) and the beam splitter (8) are sequentially located on an optical path between a collimator (9) and a scanning galvanometer (2); the dichroic mirror (3), an infrared narrowband filter (4), a focusing lens (5) and a photodiode (6) are sequentially optically connected; and the beam splitter (8) and a power meter (7) are optically connected; The photodiode (6) and the power meter (7) are respectively connected to the data processing module (11) via electrical signals.

3. The monitoring signal compensation system for selective laser melting process according to claim 2, characterized in that: The laser beam emitted by the continuous fiber laser (10) is equally divided into two beams by a beam splitter (8), one of which is directly received by a power meter (7) for monitoring power changes; the other beam is sent to a preset position of a forming cylinder 15 via a scanning galvanometer (2) and a field lens (1) to selectively melt the metal powder to form a molten pool and form the formed part; at the same time, a thermal radiation infrared beam emitted outward from the forming position is reflected by a dichroic mirror (3), transmitted by an infrared narrowband filter (4) and a focusing lens (5) in sequence, and then reaches a photodiode (6); a data processing module (11) matches the position coordinates actually scanned by the scanning galvanometer (2) with the light intensity data collected by the photodiode (6), and compensates and corrects the light intensity data signal; and finally, the generated two-dimensional correction image is analyzed to realize the monitoring of the laser selective melting process.

4. The monitoring signal compensation system for selective laser melting process according to claim 3, characterized in that: The formula for compensating and correcting the light intensity data signal is as follows: During the laser selective melting printing process, the relationship between the actual movement distance in the x-direction and the y-direction and the galvanometer angle is as follows: Where x and y are the coordinates of the processing plane point, f is the focal length of the flat field lens, α and β are the deflection angles of the deflection mirror x and the deflection mirror y respectively; When the galvanometer scans only along the x-direction (β=0) or the y-direction (α=0), the relationship between the scanning position coordinates and the galvanometer deflection angle can be simplified as: x=2fα y=2fβ The relationship between the light radiation emitted by the molten pool and the deflection angle that the deflection mirror x in the scanning galvanometer (2) can receive is as follows: Among them, σ is the radiation angle of the molten pool that the deflection mirror x can receive, θ is the latitude angle of the coordinate on the deflection mirror x on the sphere with the molten pool as the center, is the longitude angle of the coordinate on the deflection mirror x on the sphere centered on the molten pool; So, the area receiving radiation is: Since the light received by the deflection mirror x needs to be reflected by the deflection mirror y to the area that the photodiode can receive, the light intensity area S that the photodiode can receive out Simplified to: S out =Subtract 2αcos 2β Taking the position with the maximum light intensity on the printing plane as the reference, calibrate the light intensity of the remaining areas to: Among them, E1 is the light intensity at the position to be compensated, S max is the area of ​​the deflection mirror x receiving radiation when the photodiode receives the maximum light intensity, S1 is the area of ​​the deflection mirror x receiving radiation at the required compensation position, α max is the deflection angle of the deflection mirror x when the photodiode receives the maximum light intensity, α1 is the deflection angle of the deflection mirror x at the required compensation position, β max is the deflection angle of the deflection mirror y when the light intensity received by the photodiode (6) is the maximum, and β1 is the deflection angle of the deflection mirror y at the required compensation position.

5. The monitoring signal compensation system for selective laser melting process according to claim 2, characterized in that: The beam splitting ratio of the beam splitter (8) is 1:

1.

6. The monitoring signal compensation system for selective laser melting process according to claim 2, characterized in that: The shortest transmission wavelength of the dichroic mirror (3) is greater than 1000 nm and less than 1064 nm.

7. The monitoring signal compensation system for selective laser melting process according to claim 2, characterized in that: The shortest reflection wavelength of the dichroic mirror (3) is less than 800 nm.

8. The monitoring signal compensation system for selective laser melting process according to claim 2, characterized in that: The central wavelength of the infrared narrow-band filter (4) is 900 nm.

9. The monitoring signal compensation system for selective laser melting process according to claim 2, characterized in that: The wavelength of the laser light generated by the continuous fiber laser (10) is 1064 nm.

10. A method for compensating monitoring signals in a laser selective melting process, characterized in that The monitoring signal compensation system according to any one of claims 1 to 5 is used for implementation, specifically as follows: S1. Additive processing: A portion of the laser light emitted by the continuous fiber laser passes through a collimator, a galvanometer and a field lens and is selectively irradiated onto the powder bed to form a molten pool for melting and molding; S2. Power meter acquires data: the power meter receives another part of the laser emitted by the continuous fiber laser and converts it into a voltage signal; S3. Monitoring power changes: The data processing module analyzes the obtained voltage signal and determines the stability and changes of the power; S4, collecting radiation signals from the molten pool: the thermal radiation infrared beam emitted from the molten pool is reflected by the dichroic mirror (3), passes through the infrared narrow-band filter and the focusing lens in sequence, reaches the photodiode and converts the signal into a voltage signal and outputs it to the data processing module; S5, data alignment; the data processing module (11) matches the received voltage signal of the photodiode (6) with the real-time scanning position information of the scanning galvanometer (2) to obtain a two-dimensional distribution diagram of the original signal; S6. Data compensation: First, obtain the relationship between the actual movement distance in the x-direction and the y-direction and the galvanometer angle during printing: Then, the relationship between the light radiation emitted by the molten pool and the deflection angle that the deflection mirror x in the galvanometer group can receive is obtained: The area receiving radiation is: Since the light received by the deflection mirror x needs to be reflected by the deflection mirror y to the area that the photodiode (6) can receive, the light intensity area S that the photodiode (6) can receive is out Can be simplified to: S out =Subtract 2αcos 2β Finally, taking the position with the maximum light intensity on the printing plane as the reference, the light intensity of the remaining areas can be calibrated as: S7, data alignment after compensation: the data processing module (11) matches the compensated voltage signal of the photodiode (6) with the real-time scanning position information of the scanning galvanometer (2) to obtain a two-dimensional distribution diagram of the compensated signal; S8. Data fusion: Analyze the two-dimensional distribution diagram of the compensated signal with the power meter measurement data to realize the monitoring of the laser selective melting process.

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