A method and system for welding thin-walled stamped parts to their connectors

Abstract

The present application relates to the technical field of intelligent welding, and particularly relates to a welding method and system for thin-walled stamping parts and connecting parts, the method of the present application determines the synchronous interference characteristic quantity corresponding to each track point on the laser fusion welding track of the pre-extracted thin-walled stamping part and connecting part, and generates a synchronous defect gray scale image; the unqualified gray scale image sub-region is determined to have different defect performance categories, and finally, the laser welding track in the gray scale image sub-region is optimized in response to different defect performance categories; the system of the present application comprises a laser welding gun, a spatial feature extraction module, a clustering analysis module, a defect analysis module and a laser welding optimization module. Furthermore, the interference phenomenon caused by the spatial structure difference in the process of synchronously applying the welding track space and the protective gas is analyzed, the molten pool protection effectiveness is taken into account while the welding efficiency is ensured, and the quality stability of laser welding of the thin-walled stamping part is improved.

Description

Technical Field

[0001] This invention relates to the field of intelligent welding technology, and in particular to a welding method and system for thin-walled stamped parts and their connecting parts. Background Technology

[0002] In the field of laser welding of thin-walled stamped parts and connectors, the surface of thin-walled stamped parts generally has height differences such as ridges and steps after stamping. When connectors are welded and assembled with thin-walled stamped parts, the laser melting welding trajectory inevitably needs to cross these height differences. Traditional laser welding methods mostly use preset fixed trajectories and constant process parameters to perform welding, which is difficult to adapt to the spatial state changes when the trajectory crosses height differences. This makes it difficult for the shielding gas and the laser melting process to maintain synchronization. The reason is that the height difference will block and interfere with the airflow path of the shielding gas, making it impossible for the shielding gas to stably and timely cover the molten pool area, which can easily cause defects such as weld oxidation and porosity. In addition, when crossing ridges or steps, the laser welding torch needs to quickly change the incident angle of the laser beam relative to the surface of the thin-walled stamped part, while the shielding gas has a response lag after the output direction is adjusted, and cannot reach the melting position as instantaneously as the laser beam. At the same time, due to the limitations of the structural strength and heat resistance of thin-walled parts, it is impossible to alleviate the problems of protection lag and heat concentration by reducing the welding speed; otherwise, it is very easy to cause defects such as overheating and burn-through of the plate.

[0003] For example, Chinese invention patent CN117444404A, published on January 26, 2024, discloses a laser welding intelligent positioning method and system, including: acquiring an image of the workpiece to be welded, recording the welding trajectory, and preprocessing the image of the workpiece to be welded; obtaining the diameter of the suspected weld edge line, the laser welding area, and the laser smoke area based on the image of the workpiece to be welded; calculating the welding trajectory similarity and welding trajectory connection degree of the suspected weld edge line; obtaining the weld edge line; calculating the laser interference gradient degree of the weld edge line; determining the actual value of the number of autoregressive terms; and using a time series prediction model to predict the position of the welding point within the laser welding area, thereby achieving intelligent positioning of welding.

[0004] Existing technologies lack analysis of interference phenomena caused by differences in spatial structure during the synchronous application of welding trajectory space and shielding gas. This makes it impossible to ensure welding efficiency while simultaneously taking into account the effectiveness of molten pool protection and the forming quality of thin-walled parts, thus affecting the quality stability of laser welding of thin-walled stamped parts. Summary of the Invention

[0005] Therefore, the present invention provides a welding method and system for thin-walled stamped parts and their connecting parts, in order to overcome the problem that the prior art lacks analysis of the interference phenomenon caused by the difference in spatial structure during the synchronous application of the welding trajectory space and the shielding gas, and cannot ensure welding efficiency while taking into account the effectiveness of molten pool protection and the forming quality of thin-walled parts, thus affecting the quality stability of laser welding of thin-walled stamped parts.

[0006] To achieve the above objectives, the present invention provides a welding method for thin-walled stamped parts and their connecting parts, comprising: The laser melting welding trajectory of the thin-walled stamped part and the connecting part is extracted in advance. Several trajectory points are selected on the laser melting welding trajectory. The corresponding synchronous interference characterization quantity is determined based on the three-dimensional spatial information of each trajectory point. The synchronous defect grayscale map of the laser melting welding trajectory is generated based on the synchronous interference characterization quantity corresponding to each trajectory point. Based on the synchronous defect grayscale image, the grayscale image sub-regions that are not qualified are screened out, and the grayscale image sub-regions are determined as different defect manifestation categories based on the surface structure identification results of the thin-walled stamping parts within the unqualified grayscale image sub-regions. In response to the determination of different defect manifestation categories, the laser welding trajectory in the grayscale image sub-region is optimized, including adjusting the shielding gas output flow rate for the laser welding process of the defect identification trajectory sub-segment, or setting the defect feature point as the convergence endpoint of the segmented trajectory for segmented welding. The defect identification trajectory segment is defined based on the defect feature point, which is the point with the largest synchronous interference representation in the unqualified grayscale image sub-region.

[0007] Furthermore, the process of pre-extracting the laser melting welding trajectory of the thin-walled stamped part and the connecting part includes: Obtain 3D model data of thin-walled stamped parts and connecting parts, and extract the spatial contour information of the weld to be welded; Establish a welding processing spatial coordinate system, and map the preset laser welding torch head center point movement trajectory to the welding processing spatial coordinate system to obtain a laser melting welding trajectory that matches the weld space contour. The laser melting welding trajectory is sampled at equal intervals according to a preset sampling interval to obtain several uniformly distributed trajectory points.

[0008] Furthermore, the process of determining the corresponding synchronous interference characterization quantity and generating the synchronous defect grayscale image of the laser melting welding trajectory includes: A spherical action space is constructed with the trajectory point as the center and the preset effective distance as the radius; Calculate the ratio of the non-intrusive space volume within the spherical interaction space to the total volume of the spherical interaction space, and determine the ratio as the synchronous interference characterization quantity; The synchronous interferometric characterization quantity is linearly mapped to a gray value, where the larger the synchronous interferometric characterization quantity, the smaller the gray value; and the smaller the synchronous interferometric characterization quantity, the larger the gray value. Following the extension direction of the laser melting welding trajectory, the gray values ​​of each trajectory point are continuously arranged to form a synchronous defect grayscale map.

[0009] Furthermore, the process of filtering out sub-regions of grayscale images that fail the comparison includes: The synchronous defect grayscale image is divided into several grayscale sub-regions that are adjacent to each other. The average grayscale value of each sub-region is compared with the preset grayscale reference value. If the average grayscale value is greater than the preset grayscale reference value, the corresponding grayscale image sub-region is selected as the grayscale image sub-region that fails the comparison.

[0010] Furthermore, the process of determining different defect manifestation categories includes: Identify the surface of thin-walled stamped parts corresponding to the unqualified grayscale image sub-regions; If there is no surface drop characteristic in the unqualified grayscale image sub-region, the corresponding grayscale image sub-region will be identified as the first defect manifestation category. If a surface drop characteristic exists within a non-compliant grayscale image sub-region, the corresponding grayscale image sub-region will be identified as the second defect manifestation category.

[0011] Furthermore, the process of optimizing the laser welding trajectory within the grayscale image sub-region includes: If a grayscale image sub-region is determined to be the first defect manifestation category, the output flow rate of the protective gas in the laser welding process is adjusted according to the defect identification trajectory segment in the unqualified grayscale image sub-region. If a grayscale image sub-region is determined to be the second defect manifestation category, then the defect feature points in the unqualified grayscale image sub-region are set as the convergence endpoints of the segmented trajectory for segmented welding.

[0012] Furthermore, the process of defining the defect identification trajectory segment includes: Select the defect feature points within the unqualified grayscale image sub-region as the central reference points; Using the defect feature point as the midpoint, a predetermined length is extended along the extension direction of the laser melting welding trajectory to both sides of the weld start point and weld end point to form a defect identification trajectory segment.

[0013] Furthermore, the process of adjusting the protective gas output flow rate includes: The average value of the synchronous interference characterization of all trajectory points within the defect identification trajectory segment is recorded as the correction coefficient, and the output flow rate of the protective gas is increased according to the correction coefficient. The output flow rate of the protective gas is positively correlated with the correction coefficient.

[0014] Furthermore, the process of segmented welding includes: Using the defect feature point as the segment convergence endpoint, the laser melting welding trajectory is divided into two continuous welding sub-trajectories within the unqualified grayscale image sub-region; The laser welding torch is controlled to weld sequentially along each welding sub-trajectory, and each welding sub-trajectory terminates at the defect feature point.

[0015] Furthermore, the present invention also provides a welding system for thin-walled stamped parts and their connecting parts, comprising: A laser welding torch includes a laser emitter for emitting a laser beam to melt thin-walled stamped parts and connecting parts, and a gas output unit for outputting protective gas to the metal melting location; The spatial feature extraction module is used to pre-extract the laser melting welding trajectory of thin-walled stamped parts and connecting parts, select several trajectory points on the laser melting welding trajectory, and determine the corresponding synchronous interference characterization quantity based on the three-dimensional spatial information of each trajectory point. The clustering analysis module, which is connected to the spatial feature extraction module, is used to generate a synchronous defect grayscale map of the laser melting welding trajectory based on the synchronous interference characterization quantity corresponding to each trajectory point. The defect analysis module, which is connected to the cluster analysis module, is used to filter out the grayscale image sub-regions that fail the comparison and determine the grayscale image sub-regions as different defect manifestation categories based on the surface structure identification results of the thin-walled stamping parts within the unqualified grayscale image sub-regions. A laser welding optimization module is connected to both the laser welding gun and the defect analysis module to optimize the laser welding trajectory within a grayscale image sub-region.

[0016] The beneficial effects of the technical solution shown in this application include: by pre-extracting the laser melting welding trajectory of thin-walled stamping parts and connecting parts, determining the corresponding synchronous interference characterization quantity based on the three-dimensional spatial information of each trajectory point, and generating a synchronous defect grayscale map of the laser melting welding trajectory; based on the surface structure identification results of the thin-walled stamping parts in the unqualified grayscale map sub-regions, determining the grayscale map sub-regions as different defect manifestation categories; finally, in response to the determination results of different defect manifestation categories, determining to adjust the shielding gas output flow rate of the laser welding process for the defect identification trajectory sub-segments in the grayscale map sub-regions, or setting the defect feature points as the convergence endpoints of the segmented trajectories for segmented welding, thereby realizing the analysis of the interference phenomenon caused by spatial structure differences during the synchronous application of the welding trajectory space and shielding gas, ensuring welding efficiency while taking into account the effectiveness of molten pool protection, and improving the quality stability of laser welding of thin-walled stamping parts.

[0017] Furthermore, by performing linear grayscale mapping on the synchronous interference characterization quantity, the present invention can transform the quantitative value characterizing the degree of synchronous interference of the protective gas into a visual feature quantity that matches the local thermal action area, quantifying the phenomenon that the protective gas cannot act on the molten metal pool in a timely manner due to the inherent structure of thin-walled stamped parts such as edges and steps, and realizing a visual expression of the interference of the protective gas.

[0018] Furthermore, in this invention, if the unqualified grayscale image sub-region does not have other surface drop characteristics such as edges or steps, its defect is only due to insufficient shielding gas coverage caused by local spatial obstruction, and it is classified as the first defect manifestation category. However, if the unqualified grayscale image sub-region has other surface drop characteristics such as edges or steps, the laser beam incident angle needs to be adjusted rapidly and at a large angle due to the abrupt change in surface structure. The laser beam can reach the molten pool instantly, but the shielding gas has a response lag after the rapid change in airflow direction, and cannot synchronously and effectively cover the molten position, thus causing the problem of shielding failure. This type of region is classified as the second defect manifestation category, realizing the analysis of the interference phenomenon caused by the difference in spatial structure during the synchronous application of welding trajectory space and shielding gas.

[0019] Furthermore, the average value of the synchronous interference characterization of all trajectory points within the defect identification trajectory segment in this invention reflects the overall spatial obstruction degree and the shielding gas interference intensity of the region. By setting the shielding gas output flow rate and the correction coefficient to a positive correlation, the gas flow rate can be adaptively increased according to the actual interference degree. Without reducing the welding speed or increasing the heat input of the thin-walled part, the local airflow intensity and coverage are enhanced, effectively compensating for the insufficient protection caused by spatial obstruction. While avoiding burn-through of the plate, the molten pool is kept in a stable and effective protective state throughout the process, improving the quality stability of laser welding of thin-walled stamped parts.

[0020] Furthermore, this invention uses the defect feature point as the segmented convergence endpoint, dividing the welding trajectory within the unqualified grayscale image sub-region into two continuous welding sub-trajectories and welding them sequentially. This allows both welding sub-trajectories to approach the defect feature point with a gentle approach, avoiding large-angle attitude jumps of the laser welding gun at the edge or step position, thereby eliminating the lag and failure of the shielding gas caused by rapid adjustment of the output direction. It ensures that the laser heat source and the shielding gas always maintain a stable relative position and output direction, guaranteeing that the shielding gas and laser melting process work synchronously throughout, effectively avoiding defects such as weld oxidation and molten pool protection failure, and balancing welding efficiency and welding forming quality of thin-walled stamped parts. Attached Figure Description

[0021] Figure 1 This is a step diagram illustrating the welding method for thin-walled stamped parts and their connecting parts according to an embodiment of the present invention; Figure 2A flowchart illustrating the steps of determining synchronous interference characterization quantities and generating synchronous defect grayscale images in an embodiment of the present invention; Figure 3 This is a flowchart illustrating the logic of optimizing the laser welding trajectory based on different defect manifestation categories in an embodiment of the present invention. Figure 4 This is a system block diagram of a welding system for a thin-walled stamped part and its connecting parts, according to an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0023] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] It should be noted that in the description of this invention, the terms "upper," "lower," "inner," "outer," etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0025] It should be understood that although the terms "first," "second," etc., may be used in this invention to describe various types of information, these information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information.

[0026] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Please see Figure 1 The diagram shows the steps of a welding method for a thin-walled stamped part and its connecting parts according to an embodiment of the present invention. The welding method for a thin-walled stamped part and its connecting parts according to the present invention includes: Step S100: The laser melting welding trajectory of the thin-walled stamping part and the connecting part is extracted in advance. Several trajectory points are selected on the laser melting welding trajectory. The corresponding synchronous interference characterization quantity is determined based on the three-dimensional spatial information of each trajectory point. The synchronous defect grayscale map of the laser melting welding trajectory is generated based on the synchronous interference characterization quantity corresponding to each trajectory point. Step S200: Based on the synchronous defect grayscale image, filter out the grayscale image sub-regions that are not qualified in comparison, and determine the grayscale image sub-regions as different defect manifestation categories based on the surface structure identification results of the thin-walled stamping parts within the unqualified grayscale image sub-regions. Step S300: In response to the determination results of different defect manifestation categories, determine to optimize the laser welding trajectory in the grayscale image sub-region, including adjusting the protective gas output flow rate of the laser welding process for the defect identification trajectory sub-segment, or setting the defect feature point as the convergence endpoint of the segmented trajectory for segmented welding. The defect identification trajectory segment is defined based on the defect feature point, which is the point with the largest synchronous interference representation in the unqualified grayscale image sub-region.

[0028] Specifically, the process of pre-extracting the laser melting welding trajectory of the thin-walled stamped part and the connecting part includes: Obtain 3D model data of thin-walled stamped parts and connecting parts, and extract the spatial contour information of the weld to be welded; Establish a welding processing spatial coordinate system, and map the preset laser welding torch head center point movement trajectory to the welding processing spatial coordinate system to obtain a laser melting welding trajectory that matches the weld space contour. The laser melting welding trajectory is sampled at equal intervals according to a preset sampling interval to obtain several uniformly distributed trajectory points.

[0029] In this invention, the center of the reference end face after the thin-walled stamped part is clamped and positioned is taken as the origin of the coordinate system, the length direction of the thin-walled stamped part is taken as the X-axis, the direction perpendicular to the clamping reference surface is taken as the Z-axis, and the direction perpendicular to the X-axis and Z-axis is taken as the Y-axis. A Cartesian coordinate system is established as the spatial coordinate system for welding processing. The three-dimensional model data of the thin-walled stamped part and the connecting part, as well as the motion trajectory data of the welding gun, are all uniformly mapped to this coordinate system.

[0030] For example, the preset sampling interval in this invention can be set to 1cm to ensure that the sampling trajectory points can completely cover the surface structure changes of the weld, while avoiding redundant calculations caused by excessive sampling.

[0031] Specifically, please refer to Figure 2The diagram illustrates the steps of determining the synchronous interference characterization quantity and generating the synchronous defect grayscale image in an embodiment of the present invention. The process of determining the corresponding synchronous interference characterization quantity and generating the synchronous defect grayscale image of the laser melting welding trajectory includes: Step S101: Construct a spherical action space with the trajectory point as the center and the preset effective distance as the radius; Step S102: Calculate the ratio of the non-intrusive space volume to the total volume of the spherical interaction space, and determine the ratio as the synchronous interference characterization quantity; For example, using industrial-grade 3D scanning equipment and supporting point cloud processing software, a spherical 3D solid model is generated within the processing software, with the 3D coordinates (X, Y, Z) of a single trajectory point as the center and a predetermined effective distance as the radius. This model is the spherical action space corresponding to the trajectory point. For all trajectory points along the entire weld seam, the non-occupied space not occupied by the part entity within the spherical action space is calculated using the Boolean difference operation function in the processing software. The volume of the non-occupied space = the total volume of the spherical action space - the volume of the occupied space. The synchronous interference characterization quantity = the volume of the non-occupied space / the total volume of the spherical action space, with a value range of 0-1. This is a mature technical method commonly used in the field of laser welding processing, and will not be elaborated here.

[0032] For example, the synchronous interference characterization quantity = non-intrusive space volume / total volume of spherical action space, and its value ranges from 0 to 1.

[0033] Step S103: Linearly map the synchronous interferometric characterization quantity to a gray value, wherein the larger the synchronous interferometric characterization quantity, the smaller the gray value; and the smaller the synchronous interferometric characterization quantity, the larger the gray value. In this invention, the grayscale value ranges from 0 to 255, and the linear mapping relationship is: grayscale value = synchronous interference characterization quantity × 255; when the synchronous interference characterization quantity is closer to 0, the corresponding grayscale value is also closer to 0, representing no interference risk; when the synchronous interference characterization quantity is 1, the corresponding grayscale value is 255, representing the maximum interference risk.

[0034] Step S104: Arrange the gray values ​​of each trajectory point continuously according to the extension direction of the laser melting welding trajectory to form a synchronous defect gray map.

[0035] In this invention, the preset effective distance ranges from 5mm to 20mm; it is adjusted according to the spatial complexity of the welding environment between the thin-walled stamped part and its connecting parts. For example, the preset effective distance is 10mm.

[0036] It is understandable that by calculating the ratio of the non-intrusive space volume to the total volume within the spherical action space, the degree of interference of the space around the trajectory point by the drop structures such as the edges and steps of the thin-walled stamped parts can be characterized. The larger the ratio, the more significant the obstruction and interference of the part entity on the protective gas flow path, and the worse the synchronicity between the laser melting process and the protective gas action. By linearly mapping the synchronous interference characterization quantity to grayscale values, the abstract spatial interference values ​​can be transformed into intuitive visual feature quantities, realizing the visual expression of the degree of interference.

[0037] Those skilled in the art should understand that the thermal effect of the laser heat source on thin-walled stamped parts during laser welding is localized. The range of heat diffusion and the degree of thermal impact are closely related to the structural characteristics of the parts themselves around the weld trajectory. Similarly, the risk of synchronous interference of the shielding gas is concentrated only in a limited space around the trajectory point, exhibiting localized distribution characteristics consistent with heat diffusion. By performing linear grayscale mapping on the synchronous interference characterization quantity, the quantitative value characterizing the degree of synchronous interference of the shielding gas can be transformed into a visual characteristic quantity that matches the local thermal effect area, quantifying the phenomenon that the shielding gas cannot act on the molten metal pool in a timely manner due to the inherent structure of the thin-walled stamped parts, such as edges and steps.

[0038] Specifically, the process of filtering out grayscale image sub-regions that fail the comparison includes: The synchronous defect grayscale image is divided into several grayscale sub-regions that are adjacent to each other. The average gray value of each sub-region is compared with the preset gray value. If the average gray value is greater than the preset gray value, the corresponding gray image sub-region is selected as the gray image sub-region that fails the comparison. If the average grayscale value is less than or equal to the preset grayscale reference value, the grayscale image sub-region will not be filtered.

[0039] For example, in an embodiment of the present invention, the synchronous defect grayscale image is divided into several adjacent grayscale image sub-regions along the extension direction of the weld trajectory. The length of the weld trajectory corresponding to each grayscale image sub-region is 5 times the preset sampling interval, and the width of each grayscale image sub-region is 5 times the weld width.

[0040] In this invention, the preset grayscale reference value is determined through preliminary experiments. A standard thin-walled stamping part of the same material and thickness as the target workpiece is selected in advance. Using the same laser welding gun, shielding gas type, and reference welding process parameters as the actual processing, welding experiments are conducted in flat areas without structural obstruction and in areas with different degrees of obstruction. The synchronous interference characterization quantity and the corresponding weld oxidation status of each test area are collected. The grayscale value corresponding to the critical state of no oxidation defects in the weld is determined as the preset grayscale reference value. For example, when using a 0.8mm thick low-carbon steel thin-walled stamping part and argon as the shielding gas, the preset grayscale reference value is set to 85.

[0041] This invention calculates the average gray value of each grayscale sub-region to reflect the overall severity of synchronous interference of the shielding gas on the welding trajectory within the grayscale sub-region. When the average gray value of the sub-region is greater than the preset grayscale reference value, it indicates that the trajectory is in a high-risk state where the shielding gas is easily blocked by the drop structure such as ridges and steps, and the synchronous action fails. This avoids ineffective adjustments and improves the stability of the welding process and the quality of weld formation.

[0042] Specifically, please refer to Figure 3 As shown, this is a flowchart illustrating the logic of optimizing the laser welding trajectory based on different defect manifestation categories in an embodiment of the present invention. The process of determining different defect manifestation categories includes: Identify the surface of thin-walled stamped parts corresponding to the unqualified grayscale image sub-regions; If there is no surface drop characteristic in the unqualified grayscale image sub-region, the corresponding grayscale image sub-region will be identified as the first defect manifestation category. If a surface drop characteristic exists within a non-compliant grayscale image sub-region, the corresponding grayscale image sub-region will be identified as the second defect manifestation category.

[0043] In this invention, three-dimensional point cloud data of the surface of the thin-walled stamped part corresponding to the unqualified grayscale image sub-region can be obtained by a three-dimensional scanning device. The maximum surface height difference within the unqualified grayscale image sub-region is calculated. When the maximum surface height difference is ≥0.5cm, it is determined that the region has surface drop characteristics; when the height difference is <0.5cm, it is determined that the region does not have surface drop characteristics.

[0044] Understandably, identifying the surface structure of thin-walled stamped parts corresponding to unqualified grayscale image sub-regions aims to distinguish the root cause of protective gas synchronous interference defects by combining the part's own geometric features, and to accurately match the defect causes with corresponding optimization strategies. If the unqualified grayscale image sub-region does not have other surface drop characteristics such as edges or steps, its defect is only due to insufficient protective gas coverage caused by local space blockage, and it is classified as the first defect manifestation category. If the unqualified grayscale image sub-region has other surface drop characteristics such as edges or steps, the sudden change in surface structure will cause the laser beam incident angle to need to be adjusted rapidly and at a large angle. The laser beam can reach the molten pool instantly, but the protective gas has a response lag after the rapid change in airflow direction, and cannot synchronously and effectively cover the molten position, thus causing the problem of protective gas failure. This type of region is classified as the second defect manifestation category, providing a reliable basis for subsequent differentiated trajectory optimization and protective gas control measures.

[0045] Specifically, the process of optimizing the laser welding trajectory within the grayscale image sub-region includes: If a grayscale image sub-region is determined to be the first defect manifestation category, the output flow rate of the protective gas in the laser welding process is adjusted according to the defect identification trajectory segment in the unqualified grayscale image sub-region. If a grayscale image sub-region is determined to be the second defect manifestation category, then the defect feature points in the unqualified grayscale image sub-region are set as the convergence endpoints of the segmented trajectory for segmented welding.

[0046] Specifically, the process of defining the defect identification trajectory segment includes: Select the defect feature points within the unqualified grayscale image sub-region as the central reference points; Using the defect feature point as the midpoint, a predetermined length is extended along the extension direction of the laser melting welding trajectory to both sides of the weld start point and weld end point to form a defect identification trajectory segment.

[0047] Optionally, the length of the defect identification trajectory segment is the same as the length of the unqualified grayscale image sub-region.

[0048] Understandably, for the first defect manifestation category, the defect identification trajectory segment is delineated with the defect feature point as the center, and the shielding gas output flow rate is adjusted according to the average value of the synchronous interference characterization quantity. The purpose is that: this type of defect is only due to insufficient shielding gas coverage caused by local space obstruction, and there is no problem of sudden change in airflow direction caused by additional edge lines, steps or other drop structures. Therefore, there is no need to change the welding trajectory and laser incident angle; the delineated defect identification trajectory segment can cover the local heat-affected area where the shielding gas effect is insufficient.

[0049] Specifically, the process of adjusting the protective gas output flow rate includes: The average value of the synchronous interference characterization of all trajectory points within the defect identification trajectory segment is recorded as the correction coefficient K. The output flow rate of the protective gas is increased according to the correction coefficient. The output flow rate of the protective gas is positively correlated with the correction coefficient K.

[0050] In this invention, the protective gas output flow rate is increased based on the protective gas reference flow rate. The initial set protective gas reference flow rate is the protective gas reference flow rate. The adjusted protective gas output flow rate is equal to the protective gas reference flow rate × (1 + K), where K is the flow rate adjustment coefficient. The protective gas reference flow rate is 10–20 L / min. Optionally, the protective gas reference flow rate is set to 15 L / min.

[0051] Understandably, the average value of the synchronous interference characterization of all trajectory points within the defect identification trajectory segment reflects the overall spatial obstruction level and shielding gas interference intensity in that area. By setting the shielding gas output flow rate and correction coefficient to a positive correlation, the gas flow rate can be adaptively increased according to the actual interference level. Without reducing the welding speed or increasing the heat input of thin-walled parts, the local airflow intensity and coverage can be enhanced, effectively compensating for the insufficient protection caused by spatial obstruction. This ensures that the molten pool is in a stable and effective protective state throughout the entire process, while preventing the plate from burning through.

[0052] Specifically, the process of segmented welding includes: Using the defect feature point as the segment convergence endpoint, the laser melting welding trajectory is divided into two continuous welding sub-trajectories within the unqualified grayscale image sub-region; The laser welding torch is controlled to weld sequentially along each welding sub-trajectory, and each welding sub-trajectory terminates at the defect feature point.

[0053] In this invention, the defect feature point is the endpoint of the segmented convergence. Starting from the two boundary points of the unqualified grayscale image sub-region, the welding sub-trajectory is extended towards the defect feature point to form the first welding sub-trajectory and the second welding sub-trajectory. Both welding sub-trajectories have the defect feature point as the unique endpoint. For example, the laser welding gun is controlled to weld from the starting point to the defect feature point along the first welding sub-trajectory. After reaching the defect feature point, the laser emitter stops emitting light, the protective gas continues to be output, and the laser welding gun is controlled to move to the starting point of the second welding sub-trajectory, and then welds along the second welding sub-trajectory to the defect feature point.

[0054] It is understandable that the purpose of segmented welding with the defect feature point as the endpoint for the second defect manifestation category is that: the defect area has additional surface drop structures such as ridges and steps. If continuous welding is used, the laser welding gun will be forced to change the incident angle of the laser beam quickly and at a large angle at the drop position. However, the shielding gas has a significant response lag when the gas flow direction is switched quickly, and it cannot reach the molten pool as instantaneously as the laser beam, thus resulting in the problem of delayed arrival or insufficient coverage of the shielding gas. This invention uses the defect feature point as the segmented convergence endpoint, dividing the welding trajectory within the unqualified grayscale image sub-region into two continuous welding sub-trajectories and welding them sequentially. This allows both welding sub-trajectories to approach the defect feature point with a gentle approach, avoiding large-angle attitude jumps of the laser welding torch at edge or step positions, thereby eliminating the lag and failure of the shielding gas caused by rapid adjustment of the output direction. It ensures that the laser heat source and the shielding gas always maintain a stable relative position and output direction, guaranteeing that the shielding gas and laser melting process work synchronously throughout, effectively avoiding defects such as weld oxidation and failure of the molten pool protection, and balancing welding efficiency and welding forming quality of thin-walled stamped parts.

[0055] Specifically, please refer to Figure 4 The diagram shown is a system block diagram of a welding system for a thin-walled stamped part and its connector according to an embodiment of the present invention. The present invention also provides a welding system for a thin-walled stamped part and its connector, comprising: A laser welding torch includes a laser emitter for emitting a laser beam to melt thin-walled stamped parts and connecting parts, and a gas output unit for outputting protective gas to the metal melting location; This invention does not specifically limit the laser emitter and gas output unit in the laser welding equipment. The laser emitter emits a laser beam of rated power to melt the metal; the gas output unit is used to output argon protective gas to the molten pool. The laser emitter and gas output unit are commonly used equipment components in laser welding, and will not be described in detail here.

[0056] The spatial feature extraction module is used to pre-extract the laser melting welding trajectory of thin-walled stamped parts and connecting parts, select several trajectory points on the laser melting welding trajectory, and determine the corresponding synchronous interference characterization quantity based on the three-dimensional spatial information of each trajectory point. The present invention does not limit the spatial feature extraction module, which can be an industrial computer that pre-stores relevant algorithms to acquire three-dimensional model data of parts, extract the spatial contour of welds, establish a spatial coordinate system for welding processing, map the trajectory of welding torch, complete trajectory sampling, and calculate synchronous interference characterization based on the three-dimensional spatial information of trajectory points.

[0057] The clustering analysis module, which is connected to the spatial feature extraction module, is used to generate a synchronous defect grayscale map of the laser melting welding trajectory based on the synchronous interference characterization quantity corresponding to each trajectory point. The defect analysis module, which is connected to the cluster analysis module, is used to filter out the grayscale image sub-regions that fail the comparison and determine the grayscale image sub-regions as different defect manifestation categories based on the surface structure identification results of the thin-walled stamping parts within the unqualified grayscale image sub-regions. This invention does not limit the specific structure of the clustering analysis module and the defect analysis module. They can be constructed using logic components, such as field-programmable logic components, microprocessors, processors used in computers, etc., which will not be elaborated here.

[0058] A laser welding optimization module is connected to both the laser welding gun and the defect analysis module to optimize the laser welding trajectory within a grayscale image sub-region.

[0059] The present invention does not limit the laser welding optimization module, which can be a PLC controller, used to adjust the output flow of shielding gas or control the welding torch to perform segmented welding actions according to the optimization control instructions.

[0060] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A welding method for thin-walled stamped parts and their connecting parts, characterized in that, include: The laser melting welding trajectory of the thin-walled stamped part and the connecting part is extracted in advance. Several trajectory points are selected on the laser melting welding trajectory. The corresponding synchronous interference characterization quantity is determined based on the three-dimensional spatial information of each trajectory point. The synchronous defect grayscale map of the laser melting welding trajectory is generated based on the synchronous interference characterization quantity corresponding to each trajectory point. The process of pre-extracting the laser melting welding trajectory of thin-walled stamping parts and connectors includes acquiring three-dimensional model data of thin-walled stamping parts and connectors, and extracting the spatial contour information of the weld to be welded; Establish a welding processing spatial coordinate system, and map the preset laser welding torch head center point movement trajectory to the welding processing spatial coordinate system to obtain a laser melting welding trajectory that matches the weld space contour. The laser melting welding trajectory is sampled at equal intervals according to a preset sampling interval to obtain a number of uniformly distributed trajectory points; The process of determining the corresponding synchronous interference characterization quantity and generating the synchronous defect grayscale map of the laser melting welding trajectory includes constructing a spherical action space with the trajectory point as the center and the preset effective distance as the radius; Calculate the ratio of the non-intrusive space volume within the spherical interaction space to the total volume of the spherical interaction space, and determine the ratio as the synchronous interference characterization quantity; The synchronous interferometric characterization quantity is linearly mapped to a gray value, where the larger the synchronous interferometric characterization quantity, the smaller the gray value; and the smaller the synchronous interferometric characterization quantity, the larger the gray value. Following the extension direction of the laser melting welding trajectory, the gray values ​​of each trajectory point are continuously arranged to form a synchronous defect grayscale map. Based on the synchronous defect grayscale image, the grayscale image sub-regions that are not qualified are screened out, and the grayscale image sub-regions are determined as different defect manifestation categories based on the surface structure identification results of the thin-walled stamping parts within the unqualified grayscale image sub-regions. In response to the determination of different defect manifestation categories, the laser welding trajectory in the grayscale image sub-region is optimized, including adjusting the shielding gas output flow rate for the laser welding process of the defect identification trajectory sub-segment, or setting the defect feature point as the convergence endpoint of the segmented trajectory for segmented welding. The defect identification trajectory segment is defined based on the defect feature point, which is the point with the largest synchronous interference representation in the unqualified grayscale image sub-region.

2. The welding method for thin-walled stamped parts and their connecting parts according to claim 1, characterized in that, The process of filtering out grayscale image sub-regions that fail the comparison includes: The synchronous defect grayscale image is divided into several grayscale sub-regions that are adjacent to each other. The average grayscale value of each sub-region is compared with the preset grayscale reference value. If the average grayscale value is greater than the preset grayscale reference value, the corresponding grayscale image sub-region is selected as the grayscale image sub-region that fails the comparison.

3. The welding method for thin-walled stamped parts and their connecting parts according to claim 1, characterized in that, The process of determining different defect manifestation categories includes: Identify the surface of thin-walled stamped parts corresponding to the unqualified grayscale image sub-regions; If there is no surface drop characteristic in the unqualified grayscale image sub-region, the corresponding grayscale image sub-region will be identified as the first defect manifestation category. If a surface drop characteristic exists within a non-compliant grayscale image sub-region, the corresponding grayscale image sub-region will be identified as the second defect manifestation category.

4. The welding method for thin-walled stamped parts and their connecting parts according to claim 3, characterized in that, The process of optimizing the laser welding trajectory within a grayscale image sub-region includes: If a grayscale image sub-region is determined to be the first defect manifestation category, the output flow rate of the protective gas in the laser welding process is adjusted according to the defect identification trajectory segment in the unqualified grayscale image sub-region. If a grayscale image sub-region is determined to be the second defect manifestation category, then the defect feature points in the unqualified grayscale image sub-region are set as the convergence endpoints of the segmented trajectory for segmented welding.

5. The welding method for thin-walled stamped parts and their connecting parts according to claim 4, characterized in that, The process of defining the defect identification trajectory segment includes: Select the defect feature points within the unqualified grayscale image sub-region as the central reference points; Using the defect feature point as the midpoint, a predetermined length is extended along the extension direction of the laser melting welding trajectory to both sides of the weld start point and weld end point to form a defect identification trajectory segment.

6. The welding method for thin-walled stamped parts and their connecting parts according to claim 5, characterized in that, The process of adjusting the protective gas output flow rate includes: The average value of the synchronous interference characterization of all trajectory points within the defect identification trajectory segment is recorded as the correction coefficient, and the output flow rate of the protective gas is increased according to the correction coefficient. The output flow rate of the protective gas is positively correlated with the correction coefficient.

7. The welding method for thin-walled stamped parts and their connecting parts according to claim 6, characterized in that, The process of segmented welding includes: Using the defect feature point as the segment convergence endpoint, the laser melting welding trajectory is divided into two continuous welding sub-trajectories within the unqualified grayscale image sub-region; The laser welding torch is controlled to weld sequentially along each welding sub-trajectory, and each welding sub-trajectory terminates at the defect feature point.

8. A welding system for thin-walled stamped parts and their connectors, for performing the welding method for thin-walled stamped parts and their connectors as described in any one of claims 1-7, characterized in that, include: A laser welding torch includes a laser emitter for emitting a laser beam to melt thin-walled stamped parts and connecting parts, and a gas output unit for outputting protective gas to the metal melting location; The spatial feature extraction module is used to pre-extract the laser melting welding trajectory of thin-walled stamping parts and connecting parts, select several trajectory points on the laser melting welding trajectory, and determine the corresponding synchronous interference characterization quantity based on the three-dimensional spatial information of each trajectory point. The clustering analysis module, which is connected to the spatial feature extraction module, is used to generate a synchronous defect grayscale map of the laser melting welding trajectory based on the synchronous interference characterization quantity corresponding to each trajectory point. The defect analysis module, which is connected to the cluster analysis module, is used to filter out the grayscale image sub-regions that fail the comparison, and to determine the grayscale image sub-regions as different defect manifestation categories based on the surface structure identification results of the thin-walled stamping parts within the unqualified grayscale image sub-regions. A laser welding optimization module is connected to both the laser welding gun and the defect analysis module to optimize the laser welding trajectory within a grayscale image sub-region.

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