A red-blue light fusion laser cladding system

Abstract

This invention discloses a red-blue light fusion laser cladding system, belonging to the field of laser additive manufacturing and intelligent online monitoring and control technology. The system includes a coaxial laser output module, a multi-data fusion monitoring module, and a central control module. The coaxial laser output module coaxially outputs a composite laser from a red laser and a blue laser via a beam combiner. The multi-data fusion monitoring module includes a main-axis high-speed camera, a side-axis high-speed camera, a colorimetric pyrometer, an infrared thermal imager, and a spectrometer, used to acquire images of the front and side surfaces of the molten pool, fixed-point temperature, two-dimensional temperature gradient distribution, and plasma emission spectral signals, respectively. The central control module performs spatiotemporal registration, feature extraction, and multi-data fusion processing on the multi-source monitoring signals. It combines the molten pool's geometric features, temperature field information, cooling rate, and plasma electron temperature to construct a comprehensive molten pool state index, and provides real-time feedback to adjust the output power and ratio of the red and blue lasers, achieving closed-loop control of the molten pool morphology, temperature field distribution, and solidification behavior. This invention improves the forming quality of the cladding layer and suppresses defects such as pores and cracks by multi-dimensional data coupling and adaptive control of red and blue light power. It is suitable for high-precision and high-efficiency laser cladding processing and remanufacturing processes.

Description

Technical Field

[0001] This invention relates to the fields of laser additive manufacturing and intelligent monitoring technology, and in particular to a laser cladding system based on real-time control of red and blue laser power through multi-data fusion. Background Technology

[0002] Laser cladding technology is an advanced additive manufacturing and surface engineering method based on the interaction between a high-energy laser beam and synchronously transported metallic materials. Its technical principle lies in creating a transient molten pool by applying a focused laser to the surface of a substrate, while simultaneously feeding alloy powder or wire into the pool. This allows the powder to rapidly melt, solidify, and metallurgically bond with the substrate, thereby producing a cladding layer on the substrate surface with excellent wear resistance, corrosion resistance, fatigue resistance, or special functional properties. Due to its precise heat input, narrow heat-affected zone, controllable dilution rate, and compatibility with various materials, this technology is widely used in fields such as the repair of critical aerospace components, remanufacturing of energy equipment, strengthening of high-end molds, and preparation of high-performance coatings.

[0003] However, traditional laser cladding processes generally use a single wavelength as the heat source. The interaction mechanism between a single-wavelength laser and different materials is relatively fixed, and its control over the internal flow field, temperature gradient distribution, and solidification kinetics of the molten pool is limited in scope and lacks flexibility. Specifically, when processing highly reflective materials or materials sensitive to heat input, a single wavelength often faces problems such as low energy absorption or violent thermal response, resulting in poor molten pool stability. This limitation easily leads to a series of process defects: uneven energy absorption may result in incomplete fusion or poor fusion; unstable molten pool flow can lead to gas entrainment and the formation of pores; and excessive temperature gradients during rapid cooling can induce residual stress and cracks. These defects severely restrict the density, mechanical properties, and service reliability of the cladding layer, becoming a key bottleneck in improving the overall level of laser cladding technology.

[0004] To monitor and optimize the cladding process, various online monitoring methods have been explored in existing technologies. In visual monitoring, high-speed cameras with coaxial or off-axis configurations are mainly used, supplemented by narrowband filtering technology, attempting to directly observe the morphology, size, and keyhole dynamics of the molten pool. For temperature monitoring, single-point infrared thermometers or infrared thermal imagers are commonly used to acquire temperature information at a specific point or area within the molten pool. While these methods have made some progress, they mostly rely on a single type of data source. The molten pool is essentially a transient, complex system involving strong coupling of multiple physical fields such as light, heat, fluid, and metallurgy. Single-dimensional information cannot comprehensively and accurately reflect its internal dynamic heat-fluid coupling behavior, solidification front evolution, and defect initiation mechanisms. More importantly, existing monitoring technologies mostly remain at the level of "monitoring" rather than "controlling," lacking a real-time, intelligent closed-loop feedback link between monitoring data and laser process parameters. This results in a significant lag in process control, and the control accuracy depends on the operator's experience, making it difficult to achieve proactive, precise, and stable improvement in cladding quality, and failing to meet the stringent requirements for consistency and repeatability in the high-end manufacturing field.

[0005] Furthermore, red and blue lasers exhibit significant differences in absorption rate, penetration depth, and thermal mechanisms across various metallic materials. Therefore, the synergistic use of dual-wavelength lasers and the real-time coordinated control of their power have become key technical challenges in improving the adaptability and forming quality of cladding processes. Consequently, there is an urgent need to develop a laser cladding system capable of integrating multi-source monitoring data and intelligently controlling the power of red and blue lasers in real time, in order to achieve precise control and quality optimization of the cladding process. Summary of the Invention

[0006] To overcome the shortcomings of existing laser cladding technology in process monitoring and laser control, this invention provides a laser cladding system that integrates red and blue light. By integrating multiple data, the power of coaxial red and blue light is adjusted in real time to improve the quality of the cladding layer and the stability of the process.

[0007] The technical solution of the present invention is as follows:

[0008] A laser cladding system that fuses red and blue light, characterized in that it comprises:

[0009] The coaxial laser output module includes a red laser and a blue laser. The lasers output by the two lasers are coaxially irradiated onto the surface of the workpiece after passing through a beam combining device to form a molten pool.

[0010] The multi-data fusion monitoring module includes:

[0011] A main-spindle CCD camera, arranged along the laser output axis, is used to acquire image signals from the front of the molten pool.

[0012] A rangefinder high-speed camera, set at a certain angle and equipped with a laser-assisted light source, is used to acquire image signals from the side of the molten pool;

[0013] A colorimetric pyrometer, positioned at the center of the sediment layer, is used to collect temperature change signals at a fixed point.

[0014] Thermal imagers are used to acquire temperature gradient distribution signals in the molten pool and surrounding area.

[0015] The spectrometer, positioned above and to the side of the molten pool, is used to collect plasma emission spectral signals. The plasma electron temperature is calculated through characteristic spectral lines, reflecting the ionization state of the molten pool and the stability of energy coupling.

[0016] The central control module receives multi-source signals collected by the multi-data fusion monitoring module, performs data fusion and feature extraction, and generates control commands based on a preset process model to adjust the output power of the red laser and the blue laser in real time.

[0017] Furthermore, the red laser has an output wavelength of 600–700 nm, and the blue laser has an output wavelength of 400–500 nm, which is suitable for complementary modulation of the absorption characteristics of different metal powders.

[0018] Furthermore, the beam combining device is a dichroic mirror or a diffractive optical element, which realizes spatial beam combining and energy ratio adjustment of red and blue beams.

[0019] Furthermore, the angle between the rangefinder high-speed camera and the laser axis is 30°–60°, and the auxiliary light source is a semiconductor laser or LED light source with a wavelength that matches the camera's photosensitive band.

[0020] Furthermore, the temperature measuring point of the colorimetric pyrometer is located on the center line of the cladding layer width direction and is dynamically tracked along the cladding direction.

[0021] Furthermore, the spatial resolution of the thermal imager is no less than 640×480 pixels, and the frame rate is no less than 50 Hz.

[0022] Furthermore, the spectrometer acquires wavelengths covering 190nm–900nm and calculates plasma electron temperature using the Boltzmann double-line method to determine molten pool stability, material absorption state, and abnormal operating conditions.

[0023] Furthermore, the central control module includes a data fusion unit, a decision control unit, and a power drive unit, wherein the decision control unit uses fuzzy control, PID control, or neural network algorithms to achieve multi-objective optimization control.

[0024] Furthermore, the system also includes a human-machine interface for real-time display of monitoring data, control parameters, molten pool images and temperature field distribution, and supports process parameter setting and historical data query.

[0025] The beneficial effects of this invention are as follows:

[0026] By fusing the main axis and off-axis image signals, comprehensive monitoring of the three-dimensional morphology and flow behavior of the molten pool can be achieved, thereby improving the ability to perceive the dynamic process of the molten pool.

[0027] By combining the fixed-point temperature data of the colorimetric pyrometer with the temperature gradient data of the thermal imager, dual monitoring of the molten pool temperature field is achieved, providing a precise basis for heat input control. In addition, by combining the spectral monitoring module, the plasma electron temperature is obtained, which makes up for the ionization state and energy coupling information inside the molten pool that cannot be reflected by visual and temperature sensors, thereby improving the system's accuracy in identifying abnormal operating conditions and its anti-interference ability.

[0028] By integrating multiple data and adjusting power in real time, the coordinated and dynamic distribution of red and blue laser energy is achieved, optimizing the thermal history and solidification behavior of the molten pool and suppressing defects such as porosity and cracks.

[0029] The system has adaptive control capabilities and can be applied to laser cladding processes under various metal materials and process parameters, improving process stability, repeatability, and forming quality. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the optical system structure of the coaxial image monitoring platform;

[0031] Figure 2 This is a schematic diagram of a red and blue light coaxial laser cladding monitoring system; Detailed Implementation

[0032] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention. The embodiments of the present invention include the following parts:

[0033] Figure 1 This is a schematic diagram of the optical system structure of the coaxial image monitoring platform described in this invention. This platform is a key functional module for realizing coaxial visual monitoring and spectral separation of the molten pool. Figure 1 As shown, the platform includes, in sequence along the optical path propagation direction: a red and blue coaxial laser source 1, a first total reflection mirror 2, a focusing lens group 3, a protective lens 4, a monitoring optical path 5, a second reflection mirror 6, an optical attenuator 7, a narrowband filter 8, an imaging lens 9, and a CCD image sensor 10.

[0034] In this embodiment, the red-blue coaxial laser source 1 is composed of a red laser and a blue laser integrated through polarization combining or wavelength combining to output a coaxial and wavelength-complementary composite laser beam. This composite laser beam is incident on a first total reflection mirror 2, which is coated with a high-reflectivity film for the main red-blue laser bands, with a reflectivity of not less than 99%, used to precisely redirect the laser beam and guide it into the processing optical path. The redirected laser beam is then focused by a focusing lens group 3, which may contain multiple lenses to correct aberrations and ensure beam quality. The focused laser beam passes through a protective lens 4 and reaches the workpiece surface, forming a molten pool.

[0035] During the cladding process, the composite light signal radiated and reflected from the molten pool region returns along the original optical path. This returned beam is transmitted through the protective lens 4 and re-collimated by the focusing lens group 3. When it reaches the first total reflection mirror 2, the mirror maintains high reflectivity for the red and blue laser bands, thus isolating most of the processing laser reflection; while exhibiting high transmission characteristics for the selected monitoring target band, allowing the characteristic light signal of that band to be transmitted, forming the monitoring optical path 5. The transmitted monitoring light is redirected by the second reflection mirror 6 and passes sequentially through the narrowband filter 8 and the optical attenuator 7. The narrowband filter is used to selectively transmit characteristic spectral lines generated by specific physical processes in the molten pool, suppressing background interference. The optical attenuator 7 is used to adjust the light intensity to the linear response region of the CCD sensor. Finally, the beam is converged by the imaging lens 9 onto the target surface of the CCD image sensor 10 to obtain a high-contrast image reflecting the real-time morphology, size, and stability of the molten pool.

[0036] Figure 2 This is a schematic diagram of the overall architecture of the red-blue light coaxial laser cladding monitoring system described in this invention. The system is an intelligent closed-loop control system that integrates multi-sensor information fusion, mainly comprising: a coaxial laser output module, a multi-data fusion monitoring module, and a central control module.

[0037] The coaxial laser output module generates and transmits a red-blue composite laser, which, in conjunction with the powder feeder and protective gas nozzle, completes the cladding deposition process. Metal powder is transported to the molten pool under an inert gas flow, while a protective gas covers the processing area to prevent oxidation.

[0038] The multi-data fusion monitoring module includes five functionally independent sensing subsystems:

[0039] Coaxial vision sensing subsystem: its structure is as follows Figure 1 As shown, this is used to obtain a two-dimensional image of the front of the molten pool;

[0040] The rangefinder vision sensing subsystem includes a high frame rate camera and an auxiliary illumination source, which are arranged at a certain angle to capture images of the side profile of the molten pool.

[0041] Fixed-point temperature sensing subsystem: A colorimetric pyrometer is used, with its probe aligned with a specific position in the center of the cladding channel to measure the single-point temperature time-series signal in real time;

[0042] Two-dimensional temperature field sensing subsystem: An infrared thermal imager is used to acquire two-dimensional temperature distribution images of the molten pool and heat-affected zone.

[0043] Spectral monitoring subsystem: A fiber optic spectrometer is used to collect the plasma emission spectrum above the molten pool through a light collector. This is used to obtain the characteristic spectral lines of elements and the plasma electron temperature, so as to realize the monitoring of the stability and energy coupling state of the molten pool.

[0044] The central control module is the core processing and decision-making unit of the system. It receives the above five types of sensor signals and operates according to the following process:

[0045] Data synchronization and preprocessing: Time-stamp alignment, noise reduction, and format standardization of data from various sensors;

[0046] Feature extraction and information fusion: Geometric features are extracted from coaxial images, three-dimensional morphological features are extracted from paraxial images, thermal cycling features are extracted from fixed-point temperature data, temperature gradient features are extracted from thermal imaging, and spectral line intensity and plasma electron temperature are extracted from spectral signals; feature-level or decision-level fusion algorithms are used to form a unified description of the overall state of the molten pool;

[0047] Intelligent decision-making and power regulation: The fused state information is compared with the preset process knowledge base, and the power adjustment instructions for the red and blue lasers are generated in real time through the control algorithm to dynamically adjust the heat input distribution;

[0048] Closed-loop execution: Power adjustment commands are sent to the laser driver to achieve real-time correction of processing parameters, and feedback is provided through the monitoring module to form closed-loop control.

[0049] In this embodiment, the central control module performs data synchronization, spatial registration, feature extraction, multi-data fusion, and closed-loop coupling control on multi-source signals. The specific implementation method is as follows:

[0050] 1. Data synchronization and spatial registration

[0051] The central control module first synchronizes the images from the main axis camera, the images from the rangefinder camera, the temperature from the colorimetric pyrometer, the temperature from the thermal imaging, and the spectral signals, using a linear interpolation method to achieve a unified time scale.

[0052]

[0053] Spatially, a homography matrix is ​​used to complete multi-sensor region registration:

[0054]

[0055] 2. Plasma electron temperature calculation

[0056] The plasma electron temperature is calculated by selecting two characteristic spectral lines of the same element and using the Boltzmann double-line method. :

[0057]

[0058] In the formula: For excited state energy levels, The relative intensity of the spectral lines. For the transition probability, For statistical weighting, is the Boltzmann constant.

[0059] To ensure the validity of the calculation results, it is necessary to verify that the plasma satisfies the McWhirter criterion of local thermal equilibrium:

[0060]

[0061] In the formula: For electron density, The energy difference between the transition levels is (eV).

[0062] 3. Coupling of temperature field and cooling rate

[0063] Two-dimensional temperature gradient at any point on the surface of the molten pool :

[0064]

[0065] Extract the temperature difference between two points D apart in the solidification zone at the tail of the molten pool. Coupled scan speed Calculate the solidification cooling rate of the molten pool. :

[0066]

[0067] 4. Multi-data deep feature normalization and coupling

[0068] Since the dimensions of each sensing feature are different, the Min-Max algorithm is first used to extract the molten pool area. Wetting corner Fixed point temperature Temperature gradient and electron temperature Perform dimensionless normalization (denoted as an asterisked variable, such as...). .

[0069] The normalized features are then fused at the feature level to construct a comprehensive melt pool status index. :

[0070]

[0071] Weight coefficients of each feature Standard deviation of real-time data series The reciprocal of the standard deviation is adaptively determined, and the smaller the standard deviation, the more stable the current state of the feature, and the higher its weight is assigned.

[0072]

[0073] 5. Intelligent closed-loop power regulation

[0074] With the preset ideal molten pool state Using this as a benchmark, calculate the real-time deviation. :

[0075]

[0076] The dynamic adjustment of the total power of the dual beams is achieved by employing a fuzzy PID algorithm (or a neural network controller). :

[0077]

[0078] To achieve complementary energy absorption and flexible matching of heat input among different materials, a dynamic power distribution mechanism for red and blue light is designed:

[0079]

[0080] In the formula: This is the initial reference power; This is the dynamic proportioning coefficient. When the system detects a temperature gradient... When the blue light ratio increases abnormally (indicating a high-altitude reaction phase), the controller adaptively increases the blue light ratio coefficient. Blue light is used to increase the surface absorption rate of the material; after entering the stable stage, the red light ratio coefficient is increased. To ensure the depth of melting.

[0081] The workflow of this invention is as follows:

[0082] System initialization, setting process parameters and starting the laser cladding process;

[0083] In the multi-data fusion monitoring module, all sensors are activated synchronously to continuously collect images of the molten pool and temperature signals.

[0084] The central control module processes and integrates multi-source data in real time to identify the characteristics of the molten pool state.

[0085] Based on the deviation between the state characteristics and the process target, the decision unit calculates and outputs the red and blue light power adjustment amount;

[0086] The power drive unit executes control commands to adjust the laser output;

[0087] Repeat the above steps to achieve dynamic optimization and stable control of the entire cladding process.

[0088] This invention effectively improves the monitoring accuracy, real-time control, and process stability of the laser cladding process through the above-mentioned coaxial monitoring optical path design and multi-source information fusion closed-loop control. It is particularly suitable for additive manufacturing and remanufacturing of high-performance components with stringent forming quality requirements.

[0089] The embodiments described above are merely illustrative of the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent structural modifications or method improvements made based on the content of this specification and drawings should be included within the patent protection scope defined by the claims of this invention.

Claims

1. A red-blue light fusion laser cladding system, characterized in that, include: The coaxial laser output module consists of a red laser and a blue laser. The lasers output by the two lasers are coaxially irradiated onto the surface of the workpiece after passing through a beam combining device. The system includes a multi-data fusion monitoring module comprising a main-axis high-speed camera, a side-axis high-speed camera, a colorimetric pyrometer, a thermal imager, and a spectrometer. A central control module receives signals from the multi-data fusion monitoring module, performs data fusion processing, and outputs control signals to the coaxial laser output module to adjust the output power of the red and blue lasers in real time. The main-axis high-speed camera is positioned along the laser output axis to acquire images of the front of the molten pool. The side-axis high-speed camera is positioned at a certain angle to acquire images of the side profile of the molten pool. The colorimetric pyrometer is aligned with the center of the cladding layer to obtain a fixed-point temperature change signal. The thermal imager acquires two-dimensional temperature gradient distribution information of the molten pool and its surrounding area. The spectrometer acquires the plasma emission spectrum signal above the molten pool.

2. The red-blue light-fused laser cladding system of claim 1, wherein, The temperature measuring point of the colorimetric pyrometer is located on the center line of the cladding layer width direction and dynamically tracks along the cladding direction; the spectrometer is arranged above the molten pool side and calculates the plasma electron temperature by the Boltzmann double-line method to determine the ionization state and energy coupling stability of the molten pool.

3. The red-blue light fused laser cladding system of claim 1, wherein, The central control module includes: a data fusion unit for spatiotemporal registration and feature extraction of image and temperature signals; a decision control unit for generating red and blue light power adjustment commands based on a preset process model and real-time data; and a power drive unit for receiving the commands and controlling the laser output power.

4. The red-blue light-fused laser cladding system of claim 3, wherein The decision control unit employs fuzzy control, PID control, or neural network algorithms to achieve multi-objective optimization control.

5. The red-blue light fused laser cladding system of claim 1, wherein, The system also includes a human-machine interface for real-time display of monitoring data, control parameters, molten pool images, temperature field distribution, and spectral signal status.

6. The red-blue light fused laser cladding system of claim 1, wherein, The beam combining device is a dichroic mirror or a diffractive optical element.

7. A method of laser cladding control based on the system of any one of claims 1-6, characterized in that, The process includes the following steps: synchronously acquiring molten pool images, temperature signals, and spectral signals through a multi-data fusion monitoring module; performing spatiotemporal registration, feature extraction, and data fusion analysis on the multi-source data to determine the molten pool morphology, temperature field state, and plasma stability; dynamically adjusting the power ratio and absolute value of the coaxial red and blue lasers based on the analysis results; and achieving closed-loop control of the cladding process to improve the quality and process stability of the cladding layer.

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