Green light fiber laser and blue light semiconductor laser composite welding method and system based on wave division reflected light feedback

Abstract

A green light fiber laser and blue light semiconductor laser composite welding method and system based on wave separation reflection light feedback, green light and blue light laser are coaxially compounded after focusing on the workpiece; the reflected light returned along the coaxial light path is sampled and separated by wavelength during the welding process, obtaining green back light signal and blue back light signal; the controller constructs a wave separation attribution quantity based on the two wave separation back light signals, indicates the responsibility wave band of energy coupling abnormality, and implements wave separation directional correction: when the blue back light component is enhanced, the blue light power is adjusted preferentially, when the green back light component is enhanced, the green light power is adjusted preferentially; at the same time, the power ratio quantity closed loop adjustment is constructed, and multi-stage safety interlocking is executed based on the back light ratio. The present application realizes the adaptive optimization of composite welding through the attributable wave separation feedback, expands the high reflection metal welding process window, and improves the weld consistency and system safety.

Description

Technical Field

[0001] This invention belongs to the field of laser material processing and laser welding process control technology, and particularly relates to a coaxial composite welding method and system for green fiber laser and blue semiconductor laser based on wavelength division reflection feedback. Background Technology

[0002] High-reflectivity metallic materials (such as copper, copper alloys, and nickel-plated copper) are widely used in power battery connectors, motor windings, power electronic packaging, and conductive structural components. These materials generally have characteristics such as high surface reflectivity, high thermal conductivity, and rapid heat diffusion, which results in low energy coupling efficiency and sensitivity to disturbances during laser welding. The welding process window is narrow, and the stability is poor, making it difficult to achieve high-consistency weld quality while ensuring welding efficiency.

[0003] For highly reflective metals, the welding process exhibits distinct stages and nonlinearity: during the initial melting stage, the material is mostly solid with significant surface specular reflection, leading to delayed molten pool establishment and discontinuous or incomplete weld penetration at the start; once in the steady-state stage, molten pool flow, evaporation backpressure, and keyhole opening and closing cause rapid fluctuations in weld depth, linewidth, and spatter, easily resulting in defects such as porosity, spatter, and surface collapse; during the final solidification stage, rapid solidification and shrinkage of the molten pool cause shrinkage cavities and end-forming defects. Therefore, relying solely on open-loop control with fixed parameters is insufficient to adapt to differences in surface condition, variations in assembly gaps, and heat accumulation disturbances, thus affecting the repeatability of weld quality.

[0004] To improve the melting ability and welding stability of highly reflective metals, existing technologies propose using visible light (such as blue and green light) and multi-wavelength composite welding methods. The aim is to enhance absorption and shorten melting delay in the solid state, and achieve more controllable penetration and weld formation in the steady state. However, multi-wavelength composite welding commonly faces the problem of "difficulty in solidifying parameter formulations" in engineering applications. During welding, surface conditions, temperature fields, and molten pool / keyhole morphology change rapidly over short timescales. Different wavelengths exhibit different absorption / reflection behaviors in the solid and liquid states, meaning there is no fixed window for the power distribution and ratio of the two lasers applicable to all conditions. When assembly gaps, surface roughness, oxide film thickness, or heat accumulation change, the original formulation often needs to be recalibrated. Therefore, while composite welding can improve welding performance under certain conditions, it remains difficult to achieve high consistency and robust mass production capabilities.

[0005] The fundamental reason for the aforementioned "difficulty in solidifying composite formulations" lies in the lack of real-time, attributable process observations to support decision-making regarding the energy coupling state of composite welding. For highly reflective materials, when absorption decreases, the molten pool collapses, keyholes open or close, or spatter intensifies, the energy not absorbed by the material will reflect back along the optical path, forming reflected light (backlight). The mean, fluctuation, and peak events of the backlight are strongly coupled with the welding state, and changes usually precede or occur simultaneously with the deterioration of weld geometry and defects. Therefore, the backlight signal can objectively reflect whether "the current coupling has deteriorated and whether the process is becoming unstable." Especially under composite wavelength conditions, the backlight contains different wavelength components: when the instantaneous absorption of a certain wavelength by the material decreases, the backlight component of its corresponding band will be relatively enhanced. If only the total backlight is obtained without distinguishing the band components, the most critical control question in composite welding—"which power / ratio should be adjusted first at this moment"—cannot be answered, resulting in either an overall power reduction leading to incomplete penetration or failure to target the responsible band, causing peaks and instability to persist.

[0006] Therefore, in the composite welding of highly reactive metals, it is urgent to establish a set of quantitative state quantities that can characterize energy coupling and welding stability. These quantities should include not only outcome indicators such as weld linewidth, penetration depth, spatter, and porosity, but also rapidly changing process signals strongly correlated with process coupling, especially the peak value, mean value, fluctuation, and spike events of backlight. Furthermore, under composite wavelength welding conditions, the relative changes in backlight components at different wavelengths should be obtained to identify the sources of coupling anomalies and provide a basis for subsequent power allocation / ratio adjustment. Existing technologies generally suffer from insufficient process observation dimensions, weak band attribution capabilities, and unclear responses to rapid disturbances, making it difficult for highly reactive metal composite welding to simultaneously meet the engineering requirements of quality consistency and system safety margin. Summary of the Invention

[0007] The purpose of this invention is to address the problems of difficult melting initiation, low energy coupling efficiency, narrow process window, and large steady-state fluctuations in laser welding of highly reflective metallic materials (such as copper and its alloys). It provides a hybrid welding method and system based on wave-splitting reflected light feedback using green fiber laser and blue semiconductor laser. By sampling and wave-splitting the reflected light during the welding process, a power / ratio closed-loop control and safety interlock based on the wave-splitting reflected light signal is constructed. Simultaneously, optical defocusing fine-tuning is introduced to improve weld formation consistency and process stability, thereby meeting the requirements for quality consistency and safety margin in the mass production of highly reflective materials.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] This invention provides a method for composite welding of green fiber laser and blue semiconductor laser based on wavelength division reflection feedback, characterized by the following steps:

[0010] A) Laser output steps: Provide a green fiber laser and a blue semiconductor laser to output green laser beams and blue laser beams respectively;

[0011] B) Coaxial Combining and Focusing Step: The green laser beam and the blue laser beam are coaxially combined through a beam combining element. The combined beam is guided into the processing head by a folding mirror and focused by the processing head to act on the workpiece to be welded, forming a weld pool.

[0012] C) Wavelength-splitting backlight acquisition step: The reflected light returning along the coaxial optical path during the welding process is sampled, and the green backlight signal is obtained by wavelength separation through backlight sampling and wavelength-splitting dichroic elements. With blue backlight signal ;

[0013] D) Main beam monitoring steps: Acquiring the main beam monitoring signal The main beam monitoring signal is used to characterize the sampled light or leaked light of the main optical path;

[0014] E) Closed-loop adjustment step: The controller is based on the green backlight signal. Blue backlight signal and main beam monitoring signal Regarding green light power Blue light power And the power ratio of the two is adjusted in a closed loop; specifically:

[0015] E1) Constructing the partial wavelength attribution: Constructing the partial wavelength attribution The wavelength division attribution is determined by the green return signal. With blue backlight signal The relative relationship is determined to indicate whether energy coupling anomalies during welding are more likely to be caused by the green or blue light channel. The wavelength attribution factor... Use one of the following forms:

[0016] or ;

[0017] in, This is a calibrated and corrected green backlight signal used to eliminate differences between the green and blue light channels in terms of detection sensitivity, sampling ratio, or photoelectric conversion coefficient. There is a one-to-one correspondence between the direction of numerical variation and the responsible band of the energy coupling anomaly: Increased blue light channel indication is abnormal. Reduce the indication of abnormalities in the green light channel.

[0018] E2) Construction power ratio: Construction power ratio : and will Controlled within a preset steady-state window;

[0019] E3) Based on the aforementioned partial attribution quantity Implement wavelet-directed correction:

[0020] When the wave attribution amount When the blue backlight component is relatively enhanced, the blue light power is preferentially limited, reduced, and its ratio is adjusted.

[0021] When the wave attribution amount When the green backlight component is relatively enhanced, priority is given to adjusting the green light power and / or triggering defocus compensation.

[0022] When the wavelength division directional correction causes When the steady-state window is exceeded, the controller coordinates the adjustment of the power of another laser to make it so that... Return to steady state window.

[0023] F) Safety interlock protection steps: When the green backlight signal or blue backlight signal experiences a spike event or exceeds a preset threshold, safety interlock protection is executed. The safety interlock protection includes at least one of the following: amplitude limiting, power reduction, and light stoppage.

[0024] Preferably, the triggering criterion for the safety interlock protection is based on the backlight ratio. structure:

[0025]

[0026] in, For total return signal, A preset zero-constant is used to prevent the calculation of the backlight ratio from diverging due to an excessively small main beam monitoring signal or denominator term. The backlight ratio... This is used to eliminate the absolute numerical differences caused by different sampling ratios and laser power levels, and to achieve a normalized interlocking criterion that is universal across platforms.

[0027] Preferably, the safety interlock protection is configured with multiple threshold levels, including: a warning threshold. Trip threshold and peak threshold Each corresponds to a different persistence criterion. , , ;when When the corresponding threshold is exceeded and the duration condition is met, a tiered interlocking action is executed, namely, early warning limiting, rapid power reduction, or immediate shutdown; simultaneously, the interlocking is triggered based on the wavelength division attribution value. Identify the responsible band and prioritize applying amplitude limiting or power reduction to that responsible band.

[0028] As a further preferred embodiment of the present invention, the method is controlled in stages according to the welding stage, and the stages are automatically switched based on the backlight signal, specifically including:

[0029] Melting initiation stage t1: The proportion of blue light power is higher than the preset window in the steady-state stage to shorten the cell buildup time; the melting initiation criterion is the total backlight. It falls below the steady-state benchmark and volatility tends to stabilize;

[0030] Steady-state phase t2: Green light is used as the main beam to bear the main line energy input, and the power ratio is... Maintain within the preset steady-state window; and simultaneously based on the partial attribution value. Real-time execution of split-wave directional correction;

[0031] Final stage t3: The power of green light and / or blue light is ramped down to improve the end solidification and shaping, and the ramp duration is adaptively adjusted according to the backlight spike.

[0032] The switching from the initiation stage to the steady-state stage, and the switching from the steady-state stage to the termination stage, are all automatically executed by the controller based on the return light signal, without the need for an external trigger signal.

[0033] The present invention also provides a composite welding system for implementing the above method, characterized in that it includes:

[0034] Green fiber laser, used to output a green laser beam;

[0035] Blue semiconductor laser, used to output a blue laser beam;

[0036] A beam combiner is used to coaxially combine a green laser beam and a blue laser beam.

[0037] A folding mirror is used to fold and guide the coaxially combined light beam into the processing head;

[0038] The processing head is used to focus a coaxial composite beam and apply it to the workpiece;

[0039] The backlight sampling and wavelength-splitting dichroic element is set on the coaxial path of the incident light path of the processing head to sample and separate the reflected light returning along the coaxial light path according to wavelength; preferably, it is an integrated dichroic mirror assembly, whose splitting ratio for both the green and blue light bands is not less than 95%;

[0040] Green backlight detectors and blue backlight detectors are used to acquire green backlight signals, respectively. With blue backlight signal Each of its front ends is equipped with a narrowband filter corresponding to the wavelength to suppress crosstalk between bands and the influence of stray light.

[0041] The main optical path sampling monitoring detector is used to acquire the main beam monitoring signal formed by the sampling light or leakage light in the main optical path. ;

[0042] The control and display terminal is configured to: construct power ratio quantities. With partial wave attribution ,based on Implement wavelength division directional correction, based on Implement multi-level safety interlocks, and in Interlocking protection is triggered when the preset steady-state window is exceeded or the return light signal exceeds the limit.

[0043] Preferably, the control and display terminal is further configured to: divide the welding process into a melting initiation stage, a steady-state stage, and a finishing stage, and automatically switch stages based on the backlight signal; employ a blue light leader strategy in the melting initiation stage and a power ratio strategy in the steady-state stage. Closed-loop as the main component, wavelet attribution quantity With directional correction as a secondary measure, power ramp descent is performed and ramp duration is adaptively adjusted during the final stage.

[0044] Preferably, the processing head further includes a defocus fine-tuning structure, which includes a defocus fine-tuning structure, a defocus fine-tuning structure mounting component, and a hinge / rotating shaft mechanism and its driving mechanism; the driving mechanism drives the defocus fine-tuning structure to adjust its attitude and / or position through the hinge / rotating shaft mechanism to achieve equivalent defocus fine-tuning; the control and display terminal is further configured to: when the wavelength division attribution... When the green backlight component is relatively enhanced and the power adjustment response is insufficient, a defocus fine-tuning command is output simultaneously.

[0045] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts a coaxial composite welding architecture of "green light main energy input + blue light auxiliary compensation": in the steady state welding stage, green light undertakes the main line energy input and is used for precise control of penetration depth / line width. In the melting stage and the disturbance stage, blue light provides auxiliary energy, thereby decoupling the "melting capability" and "steady state forming consistency" functionally, making the process more robust to changes in the surface state of highly reactive materials, gap fluctuations and heat accumulation disturbances, and effectively expanding the available process window.

[0046] 2. This invention obtains green / blue dichroic backlight signals through backlight sampling and dichroic element 7, achieving "attributable" process observation: Compared to schemes that only monitor total backlight or only monitor output power, this invention can obtain green and blue backlight components separately, and further construct state variables such as peak value, mean, fluctuation, spike count, and dichroic attribution quantity to characterize the source of energy coupling changes (green channel / blue channel). Therefore, control decisions no longer rely on fixed open-loop formulations or empirical thresholds, but are based on real-time process observation for adaptive adjustment, reducing the risk of repeated calibration and "same formulation, batch-to-batch failure".

[0047] 3. This invention can achieve coordinated control of "wavelength-based directional correction + spike / over-limit interlocking", taking into account both quality consistency and safety margin: when the wavelength attribution indicates abnormal enhancement of backlight in a certain band, the responsible band can be limited, ramped, or its proportion can be adjusted first, rather than simply reducing the overall power, thereby significantly reducing the side effects of "overall power reduction leading to incomplete penetration and reduced efficiency"; when the total backlight or any wavelength backlight component exceeds the peak value limit, spike count limit, or continuous limit, interlocking protection (total power limiting / rapid power reduction of the responsible band / stopping light output) can be triggered, and the event is recorded for process traceability and threshold setting, improving the protection capability against back reflection risk under high power conditions.

[0048] 4. This invention introduces a main optical path sampling monitoring detector to monitor the sampling / leakage light of the main optical path online. On the one hand, it can be used for main power calibration, drift monitoring and equipment self-testing to reduce output deviation caused by laser source attenuation, optical contamination or changes in beam combining efficiency. On the other hand, it can be used as an independent criterion for safety interlocking, forming complementary redundancy with the wavelength division return channel, improving the system's reliability in identifying abnormal states (such as optical component contamination, enhanced reflection, and abnormal output), and reducing the probability of optical damage and equipment failure.

[0049] 5. This invention achieves fine-tuning of the defocus amount / equivalent focal length through the defocus fine-tuning structure 15 and the hinge and its driving mechanism 17, and can be linked with the waveguide backlight closed loop: when the waveguide backlight or main beam monitoring signal indicates focus drift, coupling degradation, or the molten pool state deviates from the target window, the focusing state can be compensated through lens fine-tuning without significantly changing the bus energy input, thereby suppressing welding fluctuations caused by workpiece height fluctuations, protective window thermal lens effect, clamping errors, etc., and improving weld geometric consistency and process stability. Preferably, the defocus fine-tuning can be adjusted within a preset range (e.g., ±5mm).

[0050] 6. The system structure of this invention is modular, easy to integrate and promote in engineering: the backlight sampling and wavelength division detection module, the main beam monitoring module, and the adjustable defocus module can all be integrated as standardized components into the processing head or external optical path, which is suitable for various welding conditions such as linear welding, spot welding and oscillating welding, and the power ratio window, threshold strategy and adjustment rules can be adjusted according to different material and process requirements, which has good engineering scalability and portability. Attached Figure Description

[0051] Figure 1 A schematic diagram of the overall structure of the green fiber laser and blue semiconductor laser composite welding system based on wavelength division reflection feedback provided in an embodiment of the present invention.

[0052] Figure 2 This is a detailed schematic diagram of the internal optical path and defocusing fine-tuning structure of the processing head in this invention.

[0053] Figure 3 This is a schematic diagram of the backlight sampling and wavelength division detection module in this invention.

[0054] Figure 4 This is a schematic diagram of the backlight detection and spectral dispersion principle in this invention.

[0055] Figure 5 This is a schematic diagram of the beam spot cross-sectional distribution of the composite beam of the present invention on the surface of the workpiece.

[0056] Figure 6 This is a functional closed-loop control block diagram of the control and display terminal in this invention.

[0057] In the diagram: 1. Blue semiconductor laser; 2. Green fiber laser; 3. Beam combiner; 4. Processing head; 5. Workpiece; 6. Frame; 7. Backlight sampling and dichroic element; 8. Green backlight detector; 9. Blue backlight detector; 10. Main optical path sampling and monitoring detector; 11. Folding mirror; 12. Control and display terminal; 13. Optical path support arm; 14. Frame; 15. Defocusing fine-tuning structure; 151. Fine-tuning lens; 152. Mounting ring; 16. Focusing lens group; 17. Drive mechanism; 171. Drive controller; 172. Linkage rod; 173. Hinge pin; 18. Worktable. Detailed Implementation

[0058] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, those skilled in the art can make equivalent changes or substitutions to its structural form, parameter range, and control strategy, all of which should fall within the scope of protection of the present invention.

[0059] A hybrid welding system based on wavelength division multiplexing (WDM) reflection feedback of green fiber laser and blue semiconductor laser, such as... Figure 1 As shown, the system includes a blue semiconductor laser 1, a green fiber laser 2, a beam combiner 3, a processing head 4, a workpiece 5, a frame 6, a backlight sampling and dichroic element 7, a green backlight detector 8, a blue backlight detector 9, a main optical path sampling and monitoring detector 10, a folding mirror 11, a control and display terminal 12, and an optical path support arm 13. The two laser beams output from the blue semiconductor laser 1 and the green fiber laser 2 are coaxially combined by the beam combiner 3, and then guided by the folding mirror 11, enter the processing head 4. The laser beams are then focused onto the workpiece 5 by the optical components within the processing head 4. The workpiece 5 is placed on the worktable 18.

[0060] like Figure 2 As shown, the processing head 4 contains, in sequence along the optical path, a collimating lens group (not labeled in the figure), a defocusing fine-tuning structure 15, and a focusing lens group 16. The focusing lens group 16 is a cemented doublet achromatic lens with a focal length f=200 mm, used to focus the composite beam onto the surface of the workpiece 5 to form the welding zone. The defocusing fine-tuning structure 15 is located between the collimating lens and the focusing lens group.

[0061] Reference Figure 3 and Figure 4 This embodiment describes in detail the structure and working principle of the backlight sampling and wavelength division detection module.

[0062] During the welding process, energy not absorbed by the workpiece 5 returns as reflected light along the original coaxial optical path. The backlight sampling and dichroic element 7 is positioned on the coaxial optical path between the folding mirror 11 and the processing head 4, such as... Figure 1 As shown. The backlight sampling and dichroic element 7 can be implemented using a backlight sampling dichroic mirror group: the reflected light returning along the coaxial optical path is sampled, and the sampled backlight is separated into green and blue backlights according to wavelength, which are coupled to the green backlight detector 8 and the blue backlight detector 9 respectively to obtain the dichroic backlight signal that can be used for attribution analysis. The green backlight signal is detected by the green backlight detector 8 and the blue backlight detector 9 respectively. With blue backlight signal .

[0063] Meanwhile, the main optical path sampling monitoring detector 10 is positioned between the beam combiner 3 and the folding mirror 11. It obtains the total power sample light of the combined beam after beam combining through the slight leakage of the beam combiner 3, and outputs the main beam monitoring signal after calibration. This signal is used to verify the output power of green and blue light in real time to compensate for power deviations caused by laser aging or temperature drift; on the other hand, it serves as an independent safety interlock criterion, forming a redundant complement with the wavelength division return signal.

[0064] The control and display terminal 12 adjusts the green light power based on the wavelength division and return signal. Blue light power The power ratio of the two components is adjusted in a closed loop, and interlocking protection actions are performed during backlight spikes, continuous over-limit conditions, or abnormal fluctuations. The closed-loop adjustment includes at least one or more of the following:

[0065] (1) Power ratio / proportion maintenance: constrain the composite output proportion with a preset target window. During the steady-state welding stage, green light is maintained as the main beam (i.e., (Not lower than the preset lower limit) to achieve precise stability of melt depth / linewidth; during the melting or disturbance stage, the proportion of blue light can be increased or a blue light leader can be used to shorten the pool building time and enhance the robustness to changes in gap and surface state.

[0066] (2) Wavelength attribution-based directional correction: based on green backlight signal With blue backlight signal Constructing total backlight And construct the partial wave attribution quantity ,

[0067] For example: ,or , in To prevent zero constant;

[0068] when When the contribution of blue backlight increases, priority should be given to applying limiting / slope reduction / proportion adjustment to the blue light channel; when When the contribution of green backlight increases, small-step power fine-tuning is performed on the green light channel first, or the defocus amount / equivalent focal length is fine-tuned in conjunction to restore the steady-state window, thereby avoiding the side effect of "overall power reduction leading to unsoldered or geometrically out-of-control".

[0069] (3) Peak / Over-limit Interlock Protection: When the peak value of the total return light or any subwavelength return light component exceeds the limit, the peak count exceeds the limit, or the continuous over-limit meets the set conditions, the control and display terminal 12 triggers the interlock protection, including rapid power reduction of the responsible band, total power limiting or stopping light output, and records the return light event for process traceability and threshold setting.

[0070] As a further preferred embodiment, the processing head 4 includes a lens frame 14, a defocusing fine-tuning structure 15, a focusing lens group 16, and a driving mechanism 17; the operating wavelength of the blue semiconductor laser 1 is within the blue light band, for example, 440 nm to 470 nm (preferably 445 nm to 460 nm); the operating wavelength of the green fiber laser 2 is within the green light band, for example, 515 nm to 545 nm (preferably 520 nm to 535 nm). The above-mentioned band range settings are used to meet the band differentiation requirements of the beam combining and color-splitting elements and to adapt to the differences in absorption characteristics of highly reflective metallic materials in the visible light band.

[0071] In a specific embodiment, the maximum continuous output power of the green fiber laser 2 is set to 1500 W; the maximum continuous output power of the blue semiconductor laser 1 is set to 500 W. The two lasers are coaxially combined by the beam combiner 3 to form a composite beam. The composite beam is refracted by the folding mirror 11 and enters the processing head 4. The optical components inside the processing head 4 focus the beam onto the workpiece 5 to complete the welding.

[0072] In a specific embodiment, the beam combining element 3 is a dichroic beam combining mirror or a dichroic mirror, which couples blue light and green light along the coaxial direction for output; the combined beam is guided into the processing head 4 by the folding mirror 11, and the focusing mirror group 16 focuses the combined beam onto the surface of the workpiece 5 to form a welding action area.

[0073] like Figure 2 The diagram shows a detailed optical path for backlight sampling and wavelength division detection. During welding, the reflected light from the surface of workpiece 5 returns along the original optical path and is sampled and separated by wavelength at the backlight sampling and wavelength division dichroic element 7: for example, the green light component in the backlight is transmitted to the green backlight detector 8, and the blue light component in the backlight is reflected to the blue backlight detector 9. Simultaneously, a main optical path sampling monitoring detector 10 is installed on the main optical path side to perform power calibration and safety interlocking of the sampled / leaked light in the main optical path.

[0074] like Figure 2 As shown, in a specific embodiment, the optical path arrangement for backlight sampling and wavelength division detection is as follows: During the welding process, the reflected light generated by the surface of the workpiece 5 returns along the coaxial optical path, is sampled at the backlight sampling and wavelength division dichroic element 7, and is separated according to wavelength to form a green backlight channel and a blue backlight channel; the green backlight channel is detected by the green backlight detector 8, which outputs a green backlight signal. The blue backlight channel is detected and output by the blue backlight detector 9, which outputs the blue backlight signal. Simultaneously, the main optical path sampling monitoring detector 10 is used to detect the sampling / leakage light in the main optical path and outputs the main beam monitoring signal. It is used as a criterion for power calibration, drift monitoring, and safety interlocking.

[0075] In a specific embodiment, the backlight sampling and wavelength division dichroic element 7 can be an integrated dichroic mirror group of "backlight sampling + wavelength division", or it can be implemented by a combination of "sampling element + dichroic element"; the green backlight detector 8, the blue backlight detector 9, and the main optical path sampling monitoring detector 10 can respectively adopt photodiodes, thermopile, or equivalent photoelectric detection components; their front ends can be configured with bandpass / narrowband filters of corresponding wavelengths to suppress crosstalk and stray light effects.

[0076] like Figure 3 As shown, in a specific embodiment, the processing head 4 is equipped with a focusing optical assembly and a defocusing fine-tuning assembly. The focusing optical assembly includes at least a lens frame 14 for supporting and positioning the main focusing element, and a focusing lens group 16 as the main focusing element. The defocusing fine-tuning assembly includes at least a defocusing fine-tuning structure 15 and a driving mechanism 17 to achieve online fine-tuning compensation of the focusing state.

[0077] The defocusing fine-tuning structure 15 includes a fine-tuning lens 151, a mounting ring 152, and a drive mechanism 17. The fine-tuning lens 151 is a plano-concave or meniscus lens, and its refractive power design allows a small displacement along the optical axis to produce an equivalent defocusing amount change within ±5 mm. The fine-tuning lens 151 is fixed inside the mounting ring 152, one side of which is hinged to the lens frame 14 via a hinge pin 173, and the other side is connected to the drive controller 171 via a connecting rod 172.

[0078] The drive controller 171 preferably employs a micro stepper motor or a piezoelectric ceramic actuator. Its output linear displacement is converted into a minute oscillation of the mounting ring 152 around the hinge pin 173 via the connecting rod 172, thereby driving the fine-tuning lens 151 to perform attitude or position fine-tuning. This driving method can achieve sub-micron level position control, with a defocus adjustment accuracy of ±0.1 mm. The drive controller 171 receives commands from the control and display terminal 12 to realize online real-time adjustment of the defocus amount.

[0079] The defocus fine-tuning structure 15 works in conjunction with the power closed-loop: when the wavelet return signal indicates focus drift (e.g., green and blue return light rise synchronously and the average total return light value increases), or when the main beam monitoring signal indicates that the protective window contamination causes a change in equivalent focal length, the control and display terminal 12, while adjusting the power ratio, sends a defocus fine-tuning command to the drive controller 171 to change the equivalent defocus amount to restore the optimal focus state. This collaborative control strategy avoids excessive changes in energy input that may result from relying solely on power adjustment, further improving robustness against thermal lensing effects, workpiece height fluctuations, and clamping errors.

[0080] As shown in Figure 5, a green fiber laser beam and a blue semiconductor laser beam are coaxially combined by a beam combiner and then focused by a processing head to form a coaxial composite spot on the workpiece surface. (Figure 5) Indicates the diameter of the green light spot. The green light spot diameter and the blue light spot diameter both characterize the size of the light spot on the workpiece surface at the corresponding wavelength. The smaller green light spot provides a higher power density main energy input, while the larger blue light spot provides auxiliary energy distribution during the melting and disturbance stages, thus achieving composite welding control of green main energy input and blue auxiliary compensation.

[0081] like Figure 6 As shown, in a specific embodiment, the control and display terminal 12 collects and processes the detection signal, including at least the following steps: [The text abruptly ends here, likely due to an incomplete translation or source material.] , , Perform synchronous sampling, filtering, and calibration; based on the main beam monitoring signal The output power is checked; a return criterion and attribution factor are constructed based on the wavelength division return signal; the output is used to check the green light power. Blue light power and defocus fine adjustment amount Control commands.

[0082] In a specific embodiment, the total return signal and the wavelength division attribution can be constructed for directional polarization correction. For example: Total return: Wavelength attribution: or ,in To prevent zero constant. When An increase indicates an increase in the blue band backlight contribution; when A decrease indicates an increase in the contribution of green band backlight. The control unit selects the priority adjustment channel accordingly to avoid incomplete penetration or uncontrolled soldering caused by "overall power reduction".

[0083] In a specific embodiment, to achieve a steady-state energy organization with green as the primary component and blue as the secondary component, the power ratio is defined as follows:

[0084]

[0085] And in the steady state phase Constraints within a preset window Inside; among them , The threshold parameters obtained from process calibration can be set according to material type, plate thickness, welding temperature, and weld target geometry.

[0086] In a specific embodiment, the welding process is divided into three stages: the initiation stage and the fusion stage. steady state phase Final stage The control and display terminal 12 performs stage switching and closed-loop adjustment based on the return light signal and the main beam monitoring signal, so that the welding process meets the control concept of "blue pilot melting - green main steady state - finishing ramp". Figure 6 This timing diagram is for illustrating the control strategy.

[0087] During the melting stage In this process, a blue light leader is preferred to rapidly establish absorption and a molten pool: blue light power The green light power is preferably increased rapidly to 0.6 to 1.0 times its maximum power (e.g., 300 W to 500 W). Simultaneously or later, ramp up to 0.2~0.6 times (e.g., 300 W~900 W). When the melting criterion is met (e.g.) When the molten pool enters the preset range and the rate of change tends to stabilize, or when the molten pool state signal reaches the stable threshold, it enters the steady state stage.

[0088] During the steady state phase In the process, green light is preferred for stable shaping: green light power Ideally, the blue light power should be maintained within the range of 900W to 1500W. It is preferable to maintain the power in the range of 50 W to 250 W, and Constrained within a preset window (e.g.) (Specifically determined by process calibration). When detected Preferring the blue band and When the amplitude is increased, the blue light channel is preferentially limited / down-adjusted to suppress backlighting; when detected... When the light is biased towards the green band or shows a trend of coupling degradation, prioritize making small, incremental adjustments to the green light channel, and coordinate with the defocus adjustment. Compensation is performed within ±5 mm to restore the steady-state window.

[0089] In the final stage In this case, a ramp-down strategy is preferred for both power paths: , Perform linear or exponential slope reduction, and for Implement a smooth transition to reduce the risk of end-stage shrinkage, collapse, and spatter; at the same time, continuously monitor the backlight signal to prevent backlight spikes caused by molten pool collapse during the final stage.

[0090] In a specific embodiment, a backlight interlock and protection mechanism is set up. To facilitate universality across different models and sampling ratios, the interlock threshold is preferably defined using a "relative threshold + duration" method, for example, constructing a backlight ratio value:

[0091]

[0092] And set early warning thresholds Trip threshold and peak threshold Simultaneously set duration criteria For example: when Continue to exceed Execute early warning and responsibility channel limits in a timely manner; when Continue to exceed Time-triggered interlock (rapid power reduction or cessation of light output); when And continue to exceed Fast protection is triggered upon activation. All threshold values ​​are configurable parameters; a preferred range is shown in the following example: , ms ms ms; or can be equivalently converted to the absolute threshold of backlight power (determined based on the sampling ratio and calibration coefficient).

[0093] In a specific embodiment, when the interlocking conditions are met, the control and display terminal 12 preferably performs one or a combination of the following actions: 1. Limiting the power of the responsible channel (e.g., prioritizing blue or green); 2. Reducing the total power and adjusting... 3. Return to steady-state window; 4. Link the defocus fine-tuning structure 15 to perform equivalent defocus compensation; 5. Stop light emission and sound an alarm. Record events for process traceability and threshold setting.

[0094] It should be noted that: such as Figure 2 The defocus fine-tuning structure 15 of the present invention shown can be implemented by means of "fine-tuning lens + hinge drive", or by other optical-mechanical structures that achieve defocus / focal length adjustment (such as linear micro-movement of slide, micro-displacement of flexible hinge or variable focal length group), all of which are equivalent embodiments of the present invention.

[0095] Furthermore, the backlight sampling and wavelength division detection module, the main optical path monitoring module, and the defocus fine-tuning module of the present invention can be integrated into the processing head 4 or arranged in an external optical path module; threshold parameters, proportion window, and three-stage timing. All of these can be determined through process calibration and configured at the control end to adapt to the process requirements of different materials, plate thicknesses and welding methods (straight welding, oscillating welding, spot welding, etc.).

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can modify, substitute equivalently, or alter the technical solutions described in the embodiments without departing from the spirit and principles of the present invention. Any modifications, equivalent substitutions, or improvements made within the inventive concept and scope of the claims of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for composite welding of green fiber laser and blue semiconductor laser based on wavelength division multiplexing (WDM) reflection feedback, characterized in that, Includes the following steps: A) Provide a green fiber laser and a blue semiconductor laser to output green laser beams and blue laser beams respectively; B) The green laser beam and the blue laser beam are coaxially combined by a beam combiner. The combined beam is guided into the processing head by a folding mirror and focused by the processing head to act on the workpiece to be welded, forming a weld pool. C) Sample the reflected light returning along the coaxial optical path during the welding process, and obtain the green backlight signal by wavelength separation through backlight sampling and wavelength division dichroism element. With blue backlight signal ; D) Acquiring the main beam monitoring signal The main beam monitoring signal is used to characterize the sampled light or leaked light of the main optical path; at the same time, it is used to verify the output power of green and blue light in real time, compensate for power deviation caused by laser aging or temperature drift; and serve as an independent safety interlock criterion. E) The controller is based on the green backlight signal Blue backlight signal and main beam monitoring signal Regarding green light power Blue light power The power ratio of the two components is adjusted in a closed-loop manner; the closed-loop adjustment specifically includes: Constructing the partial attribution quantity The wavelength division attribution is determined by the green return signal. With blue backlight signal The relative relationship is determined to indicate whether energy coupling anomalies during welding are more likely to be caused by the green light channel or the blue light channel; And based on the said partial attribution quantity Implement wavelet-directed correction: When the wave attribution amount When the blue backlight component is relatively enhanced, the blue light power is preferentially limited, reduced, and its ratio is adjusted. When the wave attribution amount When the green backlight component is relatively enhanced, priority is given to performing a ratio correction on the green light power and / or triggering defocus compensation; F) When the green or blue backlight signal experiences a spike or exceeds a preset threshold, a safety interlock protection is executed, wherein the safety interlock protection includes at least one of the following: amplitude limiting, power reduction, or light outage.

2. The composite welding method according to claim 1, characterized in that, In step E), before implementing wavelength division directional correction, the controller first establishes the power ratio. : And Controlled within a preset steady-state window; When the wavelength division directional correction causes When the steady-state window is exceeded, the controller coordinates the adjustment of the power of another laser to make it so that... Return to steady state window.

3. The composite welding method according to claim 1, characterized in that, The wavelength attribution quantity Use one of the following forms: or in, This is a calibrated and corrected green backlight signal used to eliminate differences between the green and blue light channels in terms of detection sensitivity, sampling ratio, or photoelectric conversion coefficient.

4. The composite welding method according to claim 1, characterized in that, The triggering criterion for the safety interlock protection described in step F) is based on the backlight ratio. structure: in, For total return signal, A preset zero-prevention constant is used to prevent the backlight ratio calculation from diverging due to excessively small main beam monitoring signals or denominator terms; the backlight ratio... This is used to eliminate the absolute numerical differences caused by different sampling ratios and laser power levels, and to achieve a normalized interlocking criterion that is universal across platforms.

5. The composite welding method according to claim 4, characterized in that, The safety interlock protection is set with multiple threshold levels, including: early warning threshold. Trip threshold and peak threshold Each corresponds to a different persistence criterion. , , ;when When the corresponding threshold is exceeded and the duration condition is met, a tiered interlocking action is executed, namely, early warning limiting, rapid power reduction, or immediate shutdown; simultaneously, the interlocking is triggered based on the wavelength division attribution value. Identify the responsible band and prioritize applying amplitude limiting or power reduction to that responsible band.

6. The composite welding method according to claim 1, characterized in that, The method is controlled in stages according to the welding process, with automatic switching between stages based on the backlight signal. Specifically, it includes: Melting initiation stage t1: The proportion of blue light power is higher than the preset window in the steady-state stage to shorten the cell buildup time; the melting initiation criterion is the total backlight. It falls below the steady-state benchmark and volatility tends to stabilize; Steady-state phase t2: Green light is used as the main beam to bear the main line energy input, and the power ratio is... Maintain within the preset steady-state window; and simultaneously based on the partial attribution value. Real-time execution of split-wave directional correction; Final stage t3: The power of green light and / or blue light is ramped down to improve the end solidification and shaping, and the ramp duration is adaptively adjusted according to the backlight spike. The switching from the initiation stage to the steady-state stage, and the switching from the steady-state stage to the termination stage, are all automatically executed by the controller based on the return light signal, without the need for an external trigger signal.

7. A composite welding system for implementing the method according to any one of claims 1 to 6, characterized in that, include: Green fiber laser, used to output a green laser beam; A blue semiconductor laser is used to output a blue laser beam; a beam combiner is used to coaxially combine a green laser beam with a blue laser beam; a folding mirror is used to fold the coaxially combined beam and guide it into the processing head; the processing head is used to focus the coaxially combined beam and apply it to the workpiece to be welded; a backlight sampling and wavelength-splitting dichroic element is set on the coaxial path of the incident light path of the processing head to sample and separate the reflected light returning along the coaxial light path according to wavelength; a green backlight detector and a blue backlight detector are used to acquire green backlight signals and blue backlight signals, respectively; a main light path sampling monitoring detector is used to acquire the main beam monitoring signal formed by the main light path sampling light / leakage light; a control and display terminal is used to implement closed-loop adjustment of the green light power, blue light power and their power ratio based on the green backlight signal, blue backlight signal and main beam monitoring signal, and to perform safety interlock protection when the backlight spikes or exceed the limit, wherein the safety interlock protection is at least one of: amplitude limiting, power reduction, and light stoppage.

8. The composite welding system according to claim 7, characterized in that, The processing head is equipped with a defocus fine-tuning structure, which includes a defocus fine-tuning structure, a mounting structure for mounting the defocus fine-tuning structure, and a driving mechanism. The driving mechanism drives the defocus fine-tuning structure to perform attitude and / or position fine-tuning relative to the main focusing lens group to achieve equivalent focal length or defocus amount fine-tuning. Furthermore, the defocus fine-tuning works in conjunction with the power ratio closed-loop adjustment in step E) as a second execution quantity: when the wavelength division attribution quantity... When the green backlight component is relatively enhanced and the power adjustment response is insufficient, the controller simultaneously triggers defocus fine adjustment to compensate for focus drift.

9. The composite welding system according to claim 7, characterized in that, The control and display terminal is also used to construct power ratios. With partial wave attribution , and in Interlocking is triggered when the preset steady-state window is exceeded or the return light signal exceeds the limit. The interlocking action includes at least one of the following: amplitude limiting, power reduction, and light stoppage.

Images