Curved surface self-adaptive dynamic light spot laser quenching method based on galvanometer scanning

Abstract

The invention discloses a galvanometer scanning-based curved surface self-adaptive dynamic light spot laser quenching method, which has the following beneficial effects: (1) dynamic regulation and control of a light spot energy field: a traditional uniform light spot is reconstructed into a self-defined light spot with an adjustable energy gradient according to a curvature value of a workpiece, so that the energy of each section of the light spot is dynamically distributed according to the curvature; and the energy density deviation caused by geometric deformation is compensated. And (2) scanning-energy cooperative control: through coupling optimization of a light spot form and a scanning path, galvanometer high-frequency galvanometer micro-swing scanning and laser output energy adjustment are adopted in a curvature sudden change area, so that accurate regulation and control of heat input are realized, a heat accumulation effect is inhibited, and depth uniformity (fluctuation is less than or equal to 10%) of a hardening layer is ensured. And (3) online feedback and closed-loop correction: an infrared thermal imager and a surface topography sensor are integrated, a quenching point temperature field and a hardened layer topography are monitored in real time, a light spot energy ratio and a scanning strategy are dynamically corrected through an AI algorithm, and the dynamic characteristics of material phase change in the machining process are adapted.

Description

Technical Field

[0001] The invention relates to the technical field of laser quenching, and in particular to a curved surface adaptive dynamic spot laser quenching method based on galvanometer scanning. Background Art

[0002] Laser quenching technology is an advanced surface treatment technology that uses a high-energy laser beam to quickly heat the surface of the workpiece and harden it by self-cooling. Due to its advantages such as high efficiency, precision and environmental protection, it has been widely used in the fields of mechanical manufacturing, molds and the automotive industry. Existing laser quenching technology mainly uses a fixed light spot to treat the surface of the workpiece. A linear or circular light spot with uniform energy distribution is used to scan the workpiece surface line by line in conjunction with a CNC workbench or a mechanical axis (robot, manipulator, etc.). This method is suitable for planes or simple curved surfaces, but when facing complex curved surfaces (such as special-shaped molds, gear tooth surfaces, turbine blades, etc.), although it can achieve a certain degree of surface adaptability, due to the fixed energy distribution of the light spot, it cannot adapt to the changes in the curvature of the complex curved surface, resulting in uneven distribution of the hardened layer depth and hardness.

[0003] In addition, traditional laser quenching technology has the following limitations:

[0004] Energy-geometry mismatch: Changes in surface curvature lead to dynamic changes in the projection area and incident angle of the light spot. The actual energy density of the uniform energy spot on the curved surface fluctuates significantly, which can easily cause local ablation or insufficient hardening.

[0005] Limitations in process adaptability: Fixed spot patterns are difficult to dynamically adapt to surface topology and require reliance on multiple positioning of mechanical axes or complex tooling, which is inefficient and difficult to achieve high-precision gradient hardening requirements.

[0006] The process relies on experience-based debugging: parameters such as power and scanning speed need to be repeatedly adjusted to adapt to different surfaces, resulting in low efficiency and poor consistency.

[0007] Open-loop control relies on experience: parameters need to be repeatedly debugged to adapt to different surfaces, there is a lack of real-time feedback, and consistency is poor.

[0008] In summary, the existing technology has the following technical problems: (1) Poor uniformity: Due to the curvature difference on complex curved surfaces, the traditional spot energy distribution cannot be dynamically adapted, resulting in fluctuations in the depth of the hardened layer (up to 30%-50% or more) and uneven hardness distribution. (2) Low efficiency: The mechanical axis has large inertia, the scanning speed is limited (usually <2m / min), and complex curved surfaces require multiple positioning, which takes a long time to process. (3) Insufficient adaptability: The fixed spot mode is difficult to deal with areas with sudden changes in curvature (such as the root of the gear and the edge of the blade), and customized tooling is required or processing accuracy is sacrificed. (4) Difficulty in controlling thermal effects: Traditional linear spot patterns are prone to heat accumulation effects, which can easily lead to surface overheating, expand the heat-affected zone (HAZ), and reduce the fatigue strength of the material. Summary of the Invention

[0009] (1) Technical problems solved

[0010] In response to the shortcomings of the existing technology, the present invention provides a surface adaptive dynamic spot laser quenching method based on galvanometer scanning, which can solve the problems of energy density mismatch and poor uniformity of the hardened layer caused by curvature changes in laser quenching of complex surfaces.

[0011] (2) Technical solution

[0012] To solve the above technical problems, the present invention provides the following technical solution: a surface adaptive dynamic spot laser quenching method based on galvanometer scanning, comprising the following steps:

[0013] a. Generate a gradient energy spot according to the curvature value of the workpiece to increase the energy density of the curvature compensation area of ​​the spot. The spot consists of an energy stabilization area and a curvature compensation area;

[0014] b. Use high-frequency galvanometer micro-swing scanning and pulse laser modulation in the curvature mutation area of ​​the workpiece to disperse the heat input in the curvature mutation area of ​​the workpiece;

[0015] c. Dynamically correct the spot energy ratio and scanning strategy through infrared thermal imagers and AI algorithms to achieve closed-loop control.

[0016] Preferably, in step a, the gradient energy spot is a Gaussian-flat-top composite distribution.

[0017] Preferably, in step b, the frequency of the high-frequency galvanometer micro-swing scanning is 1-10 kHz.

[0018] Preferably, in step c, the AI ​​algorithm is based on BP neural network.

[0019] Preferably, in step a, a gradient energy spot is generated according to the mapping function P_c / P_0=1+k·C^α, wherein P_c is the power density of the area corresponding to the curvature of a certain point of the generated gradient energy spot, P_0 is the power density of the energy stable area of ​​the spot, C is the curvature value, and k and α are both known parameters.

[0020] Preferably, in the mapping function, the value range of k is [0.02, 0.05], and the value range of α is [1.2, 1.5].

[0021] Preferably, in step b, the amplitude A and curvature value C of the high-frequency galvanometer micro-swing scanning satisfy A=0.1·C^0.5mm.

[0022] Preferably, in step b, the duty cycle D of the pulse laser modulation is in the range of [20%, 80%].

[0023] Preferably, before step a, the method further includes: calculating the curvature value of each region based on the three-dimensional model of the workpiece.

[0024] Preferably, in step c, the method further includes detecting the morphology of the hardened layer by using a surface morphology sensor.

[0025] (3) Beneficial effects

[0026] Compared with the prior art, the present invention provides a surface adaptive dynamic spot laser quenching method based on galvanometer scanning, which has the following beneficial effects: (1) Dynamic control of the spot energy field: The present invention reconstructs the traditional uniform spot into a custom spot with adjustable energy gradient according to the curvature value of the workpiece, so that the energy of each section of the spot is dynamically distributed according to the curvature, compensating for the energy density deviation caused by geometric deformation. (2) Scanning-energy collaborative control: Through the coupling optimization of the spot morphology and the scanning path, the galvanometer high-frequency galvanometer micro-swing scanning and laser output energy adjustment are used in the curvature mutation area to achieve precise control of heat input, suppress the heat accumulation effect, and ensure the uniformity of the hardened layer depth (fluctuation ≤ 10%). (3) Online feedback and closed-loop correction: Infrared thermal imager and surface morphology sensor are integrated to monitor the quenching point temperature field and hardened layer morphology in real time, and the spot energy ratio and scanning strategy are dynamically corrected by AI algorithm to adapt to the dynamic characteristics of material phase change during the processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the hardware system structure on which the present invention is based (the solid arrows in the figure represent the laser transmission path, and the dotted arrows represent the signal transmission path);

[0028] Figure 2 Schematic comparison between the light spot of the present invention and the traditional light spot Figure 1 ;

[0029] Figure 3 Schematic comparison between the light spot of the present invention and the traditional light spot Figure 2 ;

[0030] Figure 4 This is a schematic diagram of the laser quenching direction of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 making creative efforts are within the scope of protection of the present invention.

[0032] The present invention provides a surface adaptive dynamic spot laser quenching method based on galvanometer scanning, such as Figure 1As shown, the hardware system on which the present invention is based includes a laser 1, a galvanometer, i.e., a galvanometer scanning system 2, a sensor 3, and a control module 4. The laser beam of the laser 1 acts on the workpiece 5 through the galvanometer to perform laser quenching. The laser 1 preferably uses a high-power fiber laser with a wavelength of 1060-1080nm, a power range of ≥500W, a fiber core diameter of ≥400μm, and supports continuous / pulse mode switching. The galvanometer preferably uses a three-dimensional scanning architecture of a dual galvanometer + dynamic focusing lens group, with Z-axis dynamic compensation, a scanning speed of ≥5m / s, a positioning accuracy of ≤±5μm, and support for high-frequency micro-swing scanning (frequency ≥10kHz). Of course, other structural types of galvanometers in the prior art can also be used. The sensor 3 preferably includes an infrared thermal imager and a surface morphology sensor, so that the temperature field and the morphology of the hardened layer can be monitored online through the sensor 3. The control module 4 is used to run the control algorithm. In addition, the above-mentioned hardware system can also include a CNC workpiece positioning platform, which is used to assist in positioning of large-scale curved surfaces.

[0033] The surface adaptive dynamic spot laser quenching method based on galvanometer scanning of the present invention comprises the following steps:

[0034] a. Generate a gradient energy spot based on the workpiece's curvature to increase the energy density in the curvature compensation zone. The spot consists of an energy stabilization zone and a curvature compensation zone. This method generates a custom spot with adjustable energy gradients in each zone based on the surface curvature. Compared to traditional fixed-energy spots (such as flat-top spots), which cannot adapt to curvature changes, this method solves the energy-geometry mismatch problem and improves the uniformity of the hardened layer by over 20%-50%.

[0035] In addition, before step a, the method further includes: calculating the curvature value of each area based on the three-dimensional model of the workpiece. Specifically, the curvature value of each point of the workpiece can be calculated based on NURBS surface reconstruction, wherein the range of the curvature value can be specifically 0-500m. -1 Specifically, the 3D CAD model of the workpiece can be imported to calculate the curvature value of each area and generate a curvature-energy mapping table (the greater the curvature, the higher the energy of the curvature compensation area of ​​the spot); the curvature distribution heat map is generated through the curvature analysis algorithm to divide the high curvature area (>200m -1 ), medium curvature area (50-200m-1), low curvature area (<50m -1 ).

[0036] Preferably, in step a, the gradient energy spot is a Gaussian-flat-top composite distribution.

[0037] Specifically, in step a, a gradient energy spot is generated according to the mapping function P_c / P_0=1+k·C^α, where P_c is the power density of the area corresponding to the curvature of a certain point of the generated gradient energy spot, P_0 is the power density of the energy stable area of ​​the spot, P_0 is the known reference power density, C is the curvature value, and k and α are both known parameters; in addition, when the curvature value is 0, the area corresponding to the spot is the energy stable area, and at this time P_c is P_0.

[0038] Furthermore, preferably, in the above mapping function, the value range of k is [0.02, 0.05], and the value range of α is [1.2, 1.5].

[0039] It can be understood that the above step a calculates the curvature-energy mapping relationship in real time, which corresponds to the above mapping function, and utilizes the high-frequency response characteristics of the galvanometer system to reconstruct the traditional uniform light spot into a custom light spot with adjustable energy gradient (such as Gaussian-flat top composite distribution, multi-focus array, etc.), so that the energy of the curvature compensation area and the energy stabilization area of ​​the light spot is dynamically distributed according to the curvature, compensating for the energy density deviation caused by geometric deformation. The present invention reconstructs the traditional uniform light spot into a gradient energy light spot according to the curvature value: high curvature area: using Gaussian-flat top composite light spot, the energy density of the curvature compensation area is increased by 30%-50% (power density 3-5kW / cm 2 ), to compensate for the energy loss caused by the increase of the incident angle; low curvature area: switch to a uniform flat top spot (power density 1-2kW / cm 2 ), ensuring stable energy input.

[0040] Specifically, the spot energy distribution dynamic control algorithm can be used to control the spot energy: Figure 4 As shown in the figure, the surface is divided into small rectangles (for example, 20mm long and 2mm wide) according to the laser scanning direction (i.e., the laser quenching direction). Based on the curvature-energy mapping relationship, the curvature-energy mapping relationship is converted into a galvanometer control instruction to generate a gradient energy spot within the small rectangle. When the galvanometer scans at a high frequency, the rectangular band formed by its scanning can be regarded as a rectangular spot. Furthermore, ANSYS finite element analysis software is used to analyze and simulate the temperature field of the quenching process, and the temperature field data within each small rectangle is obtained. The temperature distribution function T = f(x, y, z, p, t), T is the transient temperature field distribution function, x, y, z are the coordinates of the quenching point, p is the laser power (w), and t is the action time (s).

[0041] It can be understood that when the galvanometer scans at a uniform speed within the amplitude area, it is necessary to establish a piecewise function of the laser energy with respect to the coordinate position according to the change in the curvature of the quenched surface. The scanning process of the galvanometer can be understood as the same displacement of the light spot along the scanning direction each time. Since the scanning frequency of the galvanometer is very high, the duration and displacement of the single-point deflection of the galvanometer are very small, and the light spot can be approximately considered to be continuously scanned. When the scanning frequency of the galvanometer is very high, the rectangular band formed by its scanning can be regarded as a rectangular light spot. In different sections of the light spot, the gradient energy light spot is achieved by adjusting the laser power and scanning overlap rate (laser action time) of the scanning point. Figure 3 The curvature compensation area shown is used to compensate for the increase in light spot energy.

[0042] b. High-frequency galvanometer micro-swing scanning and pulse laser modulation are used in the curvature mutation area of ​​the workpiece to disperse the heat input in the curvature mutation area of ​​the workpiece; compared with traditional linear scanning, which causes heat accumulation and requires reducing speed and sacrificing efficiency, the present invention can reduce the width of the heat-affected zone by 30% and increase the processing speed by 3 times.

[0043] It can be understood that step b is to achieve scanning-energy coordinated control: through the coupling optimization of the spot shape and the scanning path, high-frequency galvanometer micro-swing scanning and laser output energy adjustment are used in the curvature mutation area to achieve precise control of heat input, suppress the heat accumulation effect, and ensure the uniformity of the hardened layer depth (fluctuation ≤ 10%).

[0044] Preferably, in step b, the frequency of the high-frequency galvanometer micro-swing scanning is 1-10 kHz.

[0045] Preferably, in step b, the amplitude A and curvature value C of the high-frequency galvanometer micro-oscillation scanning satisfy A=0.1·C^0.5mm. In addition, in step b, the duty cycle D of the pulse laser modulation is preferably in the range of [20%, 80%]. The present invention designs a widened rectangular scanning path based on the curvature distribution: in the area with sudden changes in curvature (such as the root of the gear), high-frequency micro-oscillation scanning (frequency 2kHz, amplitude ±0.1mm) is adopted, combined with pulsed laser (duty cycle 20%-80%) to disperse heat input; in the flat area, linear high-speed scanning (speed ≥10m / min) is used to improve efficiency, and the spot overlap rate is controlled at 20%-30%.

[0046] In addition, preferably, an energy buffer zone is provided in the curvature mutation area (such as the edge with R<1 mm), and a segmented S-shaped energy curve transition is adopted to avoid micro cracks caused by sudden changes in the temperature field.

[0047] c. Dynamically correct the spot energy ratio and scanning strategy through infrared thermal imagers and AI algorithms to achieve closed-loop control. Compared with the open-loop control of existing technologies that rely on manual debugging and have slow response speed, the process stability of the present invention is improved by 60%, achieving "full-surface quenching in one clamping."

[0048] In addition, in step c, it is preferred to further include detecting the morphology of the hardened layer by using a surface morphology sensor.

[0049] In step c, the quenching point temperature is monitored in real time by an infrared thermal imager, and the surface morphology sensor detects the morphology of the hardened layer; if the infrared thermal imager detects that the temperature exceeds the limit or the surface morphology sensor detects that the depth deviation is greater than 10%, the AI ​​algorithm dynamically adjusts the spot energy ratio and scanning speed to achieve adaptive correction.

[0050] Specifically, the infrared thermal imager provides real-time feedback on the quenching point temperature. If it detects that the local temperature exceeds the set threshold (such as 1600°C), the AI ​​algorithm immediately reduces the power of the area by 10%-20% and increases the scanning speed.

[0051] Specifically, the surface topography sensor detects the topography of the hardened layer. If the deviation is greater than 1%, the energy ratio of the light spot is adjusted (eg, the energy of the curvature compensation area is reduced by 5%-10%).

[0052] Preferably, in step c, the AI ​​algorithm is based on BP neural network.

[0053] It can be understood that the above step c is used to achieve online feedback and closed-loop correction: integrating infrared thermal imagers and surface morphology sensors to monitor the quenching point temperature field and hardened layer morphology in real time, and dynamically correcting the spot energy ratio and scanning strategy through AI algorithms to adapt to the dynamic characteristics of material phase change during the processing process.

[0054] For the traditional process: it uses a linear spot, the hardened layer depth fluctuates by ±0.25mm, the single piece processing time is 45 minutes, the middle area of ​​the spot (corresponding to the top of the arc) is slightly over-burned due to excess heat accumulation, and the areas on both sides of the spot are under-quenched due to insufficient heat accumulation. By using the surface adaptive dynamic spot laser quenching method based on galvanometer scanning of the present invention, the following technical effects can be achieved: Gradient energy spot: the central energy of the areas on both sides of the spot (corresponding to the top of the arc) is increased by 40% (4.2kW / cm 2 ). Scanning path: linear scanning at the top of the arc (speed 15m / min), micro-oscillation scanning on both sides (frequency 20kHz). Path optimization: S-shaped staggered filling, overlap rate 25%. Closed-loop control: AI dynamically adjusts power deviation to <±5%, temperature error <±3°C. The uniformity of the hardened layer depth is improved to ±0.05mm, and the hardness fluctuation is HV±20; the processing time is shortened to 12 minutes; the width of the heat-affected zone is reduced from 0.5mm to 0.3mm, and there are no overburning defects.

[0055] Compared with the existing technology, the present invention provides a surface adaptive dynamic spot laser quenching method based on galvanometer scanning, which has the following beneficial effects: (1) Improved quenching uniformity: By compensating the curvature effect through the gradient energy spot, the fluctuation of the hardened layer depth is ≤10% (the traditional process is 30%-50%), and the hardness uniformity is improved by more than 40% (HV fluctuation is reduced from ±50 to ±20). (2) Significantly improved processing efficiency: The galvanometer scanning speed reaches 5m / s, and combined with path optimization, the processing time of complex surfaces is reduced by 50%-70% (for example, the processing time of a single piece of aviation gear is shortened from 45 minutes to 12 minutes). (3) Enhanced process adaptability: The curvature range can be processed from 0-500m -1 It can handle complex curved surfaces without the need for custom tooling, making it suitable for applications such as gears, blades, and special-shaped molds. (4) Reduce the risk of thermal damage: Closed-loop control ensures that the surface temperature error is less than ±5%, and the width of the heat-affected zone is reduced by 30% (from 0.5mm to 0.35mm), avoiding material overburning or abnormal phase change. (5) Intelligence and scalability: It supports integration with robots and additive manufacturing systems and can be expanded to composite processes such as laser cladding and surface alloying.

[0056] It should be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not preclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0057] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A surface adaptive dynamic spot laser quenching method based on galvanometer scanning, characterized in that: The following steps are involved: a. Generate a gradient energy spot according to the curvature value of the workpiece to increase the energy density of the curvature compensation area of ​​the spot, wherein the spot consists of an energy stabilization area and the curvature compensation area; b. Using high-frequency galvanometer micro-swing scanning and pulse laser modulation in the curvature mutation area of ​​the workpiece to disperse the heat input in the curvature mutation area of ​​the workpiece; c. Dynamically correct the spot energy ratio and scanning strategy through infrared thermal imagers and AI algorithms to achieve closed-loop control.

2. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1 is characterized in that: In step a, the gradient energy spot is a Gaussian-flat-top composite distribution.

3. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1 is characterized in that: In the step b, the frequency of the high-frequency galvanometer micro-swing scanning is 1-10 kHz.

4. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1 is characterized in that: In step c, the AI ​​algorithm is based on BP neural network.

5. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1 is characterized in that: In step a, the gradient energy spot is generated according to the mapping function P_c / P_0=1+k·C^α, wherein P_c is the power density of the curvature area corresponding to a certain point of the generated gradient energy spot, P_0 is the power density of the energy stable area of ​​the spot, C is the curvature value, and k and α are both known parameters.

6. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 5 is characterized in that: In the mapping function, the value range of k is [0.02, 0.05], and the value range of α is [1.2, 1.5].

7. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1 is characterized in that: In the step b, the amplitude A of the high-frequency galvanometer micro-swing scanning and the curvature value C satisfy A=0.1·C^0.5mm.

8. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1 is characterized in that: In the step b, the duty cycle D of the pulse laser modulation is in the range of [20%, 80%].

9. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1 is characterized in that: Before step a, the method further includes: calculating the curvature value of each region based on the three-dimensional model of the workpiece.

10. The surface adaptive dynamic spot laser quenching method based on galvanometer scanning according to claim 1, characterized in that: In the step c, the method further includes detecting the morphology of the hardened layer by using a surface morphology sensor.

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