Laser welding device for creating a welded joint

Abstract

Laser welding device (1) for producing a welded joint (S) in the area of ​​a joint between at least two components (2, 3) by means of an emitted laser beam (LS) with - a laser scanner (4), having - at least one laser emitter (4.1) designed to emit laser radiation (L), and - at least one laser optic (4.2) designed to shape, direct and focus the emitted laser radiation (L) to form the laser beam (LS), - a measuring unit (4.3) which is designed, - to emit at least one measuring beam (MS) in such a way that it is guided to a predetermined point of impact on at least one of the components (2, 3), - to detect reflected components of the measuring beam (MS) and - to automatically determine depth data of the point of impact based on optical coherence tomography using measurement beam data (MD1 to MD3) determined from the reflected components, - a control unit (4.4) which is designed, - before welding, the measuring unit (4.3) is controlled so that it automatically scans a surface of the components (2, 3) in a grid-like scan movement using a measuring beam (MS), automatically determines geometric parameters of the components (2, 3) from depth data determined at the respective point of impact from measuring beam data (MD1), and stores the parameters as reference data in a database for different positions of the surface of the components (2, 3). - then, during welding, to control the laser scanner (4) so ​​that it directs the laser beam (LS) onto the surfaces of the components (2, 3) and at least partially melts the components (2, 3), and simultaneously to control the measuring unit (4.3) so that it automatically scans a generated melt (SM) using a measuring beam (MS) in a scanning motion and automatically determines depth data of a vapor capillary (DK) generated in the melt (SM) based on optical coherence tomography for different positions of the melt (SM) from measuring beam data (MD2), and - to compare the position-related depth data of the vapor capillary (DK) with the position-related reference data in a comparison process carried out simultaneously with or following welding, and to determine a position-related comparison depth of the vapor capillary (DK) in comparison to an initial state of the components (2, 3) existing before welding, wherein the measuring unit (4.3) is configured to emit at least one measuring beam (MS) into the at least one laser optic (4.2) in such a way that it is guided together with the laser beam (LS) to its point of impact.

Description

[0001] The invention relates to a laser welding device for producing a welded joint in the area of ​​a joint between at least two components by means of an emitted laser beam.

[0002] From DE 10 2024 001 048 A1 a method and a device for assessing a weld seam produced on a workpiece by means of a laser beam during a laser welding process are known, wherein - a welding device with a laser beam optic and with a measuring beam optic set up for carrying out continuous optical coherence tomography, as well as two or more joining partners stacked on top of each other in a predefinable relative position to the welding device, are provided, - a laser welding process is established in which the welding device is moved in a surface-parallel welding direction relative to the workpiece, or vice versa, and a weld seam is created on the workpiece using a laser beam provided by means of the laser beam optics, and - during the laser welding process, continuous optical coherence tomography is performed using the measuring beam optics, within which capillary depth measurements of a vapor capillary forming on the workpiece during the laser welding process and of a welding influence area surrounding the vapor capillary are determined, and surface depth measurements of two surface sections located outside the vapor capillary and outside the welding influence area of ​​a surface of the workpiece facing the measuring beam optics are determined as a reference for the capillary depth measurements.

[0003] EP 4 104 963 A1 discloses a method for welding grouped conductor ends of a component for an electric machine using a device. In the method, a first parameter of the weld pool is first measured. Then, a second parameter of the weld pool is measured. In a further process step, a value for the weld pool is determined from the first and second parameters. Finally, the welding energy input is controlled depending on the determined weld pool value.

[0004] The invention is based on the objective of providing a novel laser welding device for producing a welded joint.

[0005] The problem is solved according to the invention by a laser welding device which has the features specified in claim 1.

[0006] In the method for producing a welded joint in the area of ​​a joint between at least two components, the focus according to the invention is on a laser welding device with an emitted laser beam; in this respect - If, prior to welding, the surface of the components is automatically scanned using a measuring beam in a raster-shaped scanning motion, depth data and geometric parameters of the components are automatically determined from measuring beam data based on optical coherence tomography, and the parameters, in particular with an associated intensity of the received measuring beam data, are stored as reference data in a database for different positions on the surface of the components. - Subsequently, during welding, the laser beam is directed onto the surfaces of the components and the components are at least partially melted, while simultaneously a measuring beam automatically scans a generated melt in a scanning motion, and depth data of a vapor capillary generated in the melt are automatically determined for different positions of the melt based on optical coherence tomography from measuring beam data and - In a comparison process carried out simultaneously with or following welding, the position-related depth data of the steam capillary are compared with the position-related reference data, and a position-related comparison depth of the steam capillary is determined in comparison to an initial state of the components before welding.

[0007] For some welded joints, quality assurance is either impossible or severely limited because—as, for example, in the laser welding of so-called hairpin pairs of electric motor windings—the component edges of the parts to be welded, which would otherwise be detectable by a system, are completely melted during the welding process. This prevents any reference to other components or component edges during welding. In this case, due to the lack of reference, the penetration depth or the depth of the vapor capillary cannot be measured online during welding. Furthermore, even after welding, it is impossible to reference the weld surface, and consequently, no meaningful assessment of the weld's quality can be made.

[0008] Prior art methods in which sequential referencing and measurement of the depth of the vapor capillary takes place in order to obtain position-accurate depth information about the welding process are therefore not applicable to the aforementioned applications due to the melting of the component edges.

[0009] The present method advantageously enables, by determining the reference data before welding, determining the depth data of the vapor capillary during welding, and comparing the determined depth data of the vapor capillary with the reference data, that even with component edges that completely melt during the welding process, the depth data of the vapor capillary can be referenced to the reference data, thus ensuring quality assurance. This eliminates the need for online referencing, so that full signal yield is available to the measuring unit during the welding process. Furthermore, because all component edges and information from the welding process, including the depth of the vapor capillary, are referenced to the laser welding device performing the laser welding process, the method allows for control of the welding process, for example, by adjusting the focus and / or power of the laser beam.

[0010] In a welding process where multiple welds are produced, the determination of reference data is carried out specifically before each welding operation, i.e., separately for each weld. This enables unambiguous and reliable referencing.

[0011] In possible configurations of the method, depending on the set measurement position, additional information from the welding process can be detected alongside the depth data of the vapor capillary, such as the weld pool surface. This enables the detection of further features, such as the melting depth, including process control to a set value, for example, a minimum melting depth. The measurements taken with the measuring beam can be performed in all spatial directions, i.e., vertically, horizontally, and horizontally.

[0012] Furthermore, the present method is characterized by particularly high flexibility with regard to the geometry of the components to be welded and their materials, and is especially suitable for laser welding of, for example, copper hairpins of an electric motor. The method can be implemented using conventional system technology, such as a laser scanner in combination with measurement technology based on optical coherence tomography.

[0013] Furthermore, the process is at least almost cycle time-neutral and consequently cost-neutral, while simultaneously improving measurements and ensuring high process reliability.

[0014] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0015] This shows: Fig. 1. Schematic perspective views of a laser welding device during different steps of a process for producing a welded joint in the area of ​​a joint between two components and Fig. 2 schematic position-related progressions of measuring beam data before and after welding.

[0016] Corresponding parts are marked with the same reference symbols in all figures.

[0017] In Fig. Figure 1 shows perspective views of a possible embodiment of a laser welding device 1 during different steps of a method for generating a welded joint S in the area of ​​a joint between two components 2, 3 and the components 2, 3 as well as a coordinate system with a longitudinal direction x, a transverse direction y and a vertical direction z.

[0018] The laser welding device 1 comprises a laser scanner 4 with a laser emitter 4.1 for emitting laser radiation L and a laser optic 4.2 for shaping, directing, and focusing the emitted laser radiation L to form a laser beam LS and to guide it onto the components 2, 3. For this purpose, the laser optic 4.2 comprises several optical elements 4.2.1 to 4.2.3, which are configured to focus the emitted laser radiation L and direct it as a laser beam LS in a desired direction onto the components 2, 3. For this focusing and directing, some of the optical elements 4.2.1, 4.2.2 are designed to be pivotable about at least one axis.

[0019] The laser welding device 1 further comprises a measuring unit 4.3 integrated into the laser optics 4.2, which is configured to emit a measuring beam MS onto another optical element 4.2.4 in the laser optics 4.2. The further optical element 4.2.4 is configured to direct the measuring beam MS onto the optical element 4.2.1. For this purpose, the optical element 4.2.4 is designed to be pivotable about at least one axis. The optical elements 4.2.1 to 4.2.3 are configured to direct the measuring beam MS in a desired direction onto a respective point of impact on the components 2, 3. Furthermore, the measuring unit 4.3 is configured to detect reflected components of the measuring beam MS and to determine the measurement beam based on the reflected components and in the following parameters: Fig. 2. Depth data of the respective point of impact are determined automatically based on optical coherence tomography using the measurement beam data MD1 to MD3, which are presented in more detail below.

[0020] Furthermore, the laser welding device 1 has a control unit 4.4 which is digitally coupled to the laser emitter 4.1, the optical elements 4.1.1, 4.1.2, 4.1.4 and the measuring unit 4.3 for controlling the laser emitter 4.1, the optical elements 4.1.1, 4.1.2, 4.1.4 and the measuring unit 4.3.

[0021] Components 2 and 3 are arranged in a butt joint. Components 2 and 3 are, for example, designed as so-called hairpins of windings in an electric motor.

[0022] For a mechanical connection, and, if the components 2 and 3 are designed as hairpins, an electrical connection, these are joined together by means of the laser beam LS emitted by the laser welding device 1 and directed onto their surfaces, forming the welded joint S. For this purpose, the components 2 and 3 are melted on their surfaces facing the laser optics 4.2.

[0023] To enable the referencing of a melt SM generated during welding, a vapor capillary DK formed in the melt SM, and a solidified melt eS to the original surface of components 2 and 3 existing before welding, it is provided that the surface of components 2 and 3 is automatically scanned in a raster-like scan motion using a measuring beam MS before welding. This is shown in the left-hand diagram. Fig. Figure 1 shows this schematically. For this purpose, the measuring beam MS is emitted onto the optical element 4.2.3 by means of the measuring unit 4.3, which is controlled by the control unit 4.4. To realize the raster-shaped scan movement, the optical elements 4.1.1, 4.1.2, 4.1.4 are controlled by the control unit 4.4 such that, by pivoting about at least one axis, they direct the measuring beam MS to a defined point of impact on the surface of the components 2, 3.

[0024] The control unit 4.4 automatically determines depth data and geometric parameters of components 2 and 3 based on optical coherence tomography, using measurement beam data MD1 received by the measuring unit 4.3. The depth data, in particular the corresponding intensity of the received measurement beam data MD1, are stored as reference data for various positions on the surface of components 2 and 3 in a database integrated into the control unit 4.4.

[0025] If it is planned that several welded joints S are to be produced in succession, the previously described determination of the reference data is carried out separately before each welding.

[0026] After the reference data for the respective welding process has been generated, the welding is carried out. This is shown in the middle of the diagram. Fig. Figure 1 shows this schematically. For this purpose, the control unit 4.4 controls the laser scanner 4, i.e., the laser emitter 4.1 and the laser optics 4.2, such that the laser beam LS is directed onto the surfaces of the components 2, 3 and the components 2, 3 are at least partially melted on their surface. In this process, the melt SM is generated, and a vapor capillary DK forms in the melt SM in the area of ​​the laser beam LS.

[0027] During welding, the control unit 4.4 simultaneously controls the measuring unit 4.3 in such a way that the latter automatically scans the generated melt SM using a measuring beam MS in a scanning motion and automatically determines depth data of the vapor capillary DK generated in the melt SM based on optical coherence tomography for various positions of the melt SM from the measuring beam data MD2. In particular, the measuring beam MS is positioned so that it is directed to the same point of impact on components 2, 3 as the laser beam LS.

[0028] In particular, the laser scanner 4 is controlled by the control unit 4.4 during welding in such a way that the welding process is regulated. Depending on the depth data of the vapor capillary DK acquired during welding, this regulation can, for example, be carried out such that a Fig. 2. Minimum melting depth T shown in more detail minthe components 2, 3 are reached or exceeded.

[0029] In a comparison process carried out simultaneously with or following welding, the position-related depth data of the vapor capillary DK, i.e., a in Fig. 2. The depth T of the vapor capillary DK, as shown in more detail, is compared with the position-related reference data, and a position-related comparison depth of the vapor capillary DK is determined in comparison to an initial state of components 2, 3 before welding.

[0030] Furthermore, optionally, as shown in the right-hand illustration of the Fig. Figure 1 schematically shows that, after welding and solidification of the melt SM, the control unit 4.4 controls the measuring unit 4.3 such that a measuring beam MS scans the surface of the solidified melt eS in a raster-like scanning motion. Based on optical coherence tomography, geometric data of the solidified melt eS are automatically determined from the received measuring beam data MD3 for various positions on the surface of the solidified melt eS. By comparing the geometric data of the solidified melt eS with the reference data, properties of the solidified melt eS and the quality of the resulting weld S are determined.

[0031] Fig. Figure 2 shows position-related profiles of measurement beam data MD1 to MD3 before and after welding. The measurement beam data MD1 to MD3 represent the position-related profile of the point of impact of a measurement beam MS emitted by the measuring unit 4.3 and the laser optics 4.2 on the surface of components 2, 3 (left profile in Figure 2). Fig. 2), in the vapor capillary DK of the melt SM (average course in Fig. 2) and on a surface of the solidified melt eS (right course in Fig. 2) in the vertical direction z and longitudinal direction x.

[0032] The left curve shows the MD1 measurement beam data recorded before welding to generate the reference data.

[0033] The middle curve shows a superposition of the measuring beam data MD1 with the measuring beam data MD2 determined during welding and used to determine the depth T of the vapor capillary DK, and with the minimum melting depth T. min, also known as minimum weld penetration depth.

[0034] The right-hand curve shows a superposition of the measuring beam data MD1 with the measuring beam data MD2 determined during welding and with the measuring beam data MD3 optionally recorded after welding and to determine the geometric data of the solidified melt eS.

[0035] In contrast to the two-dimensional design of the profiles, the measuring unit 4.3 and control unit 4.4 can be designed in such a way that emission of measuring beams MS and acquisition of measuring beam data MD1 to MD3 in several planes is possible, so that a complete three-dimensional profile of the respective acquired surface can be created from the measuring beam data MD1 to MD3 before welding, during welding and after welding.

Claims

[1] Laser welding device (1) for producing a weld joint (S) in the area of ​​a joint between at least two components (2, 3) by means of an emitted laser beam (LS) with - a laser scanner (4), having - at least one laser emitter (4.1) designed to emit laser radiation (L), and - at least one laser optic (4.2) designed to shape, direct and focus the emitted laser radiation (L) to form the laser beam (LS), - a measuring unit (4.3) which is designed, - to emit at least one measuring beam (MS) in such a way that it is guided to a predetermined point of impact on at least one of the components (2, 3), - to detect reflected components of the measuring beam (MS) and - to automatically determine depth data of the point of impact based on optical coherence tomography using measurement beam data (MD1 to MD3) determined from the reflected components, - a control unit (4.4) which is designed, - before welding, the measuring unit (4.3) is controlled so that it automatically scans a surface of the components (2, 3) in a grid-like scan movement using a measuring beam (MS), automatically determines geometric parameters of the components (2, 3) from depth data determined at the respective point of impact from measuring beam data (MD1), and stores the parameters as reference data in a database for different positions of the surface of the components (2, 3). - then, during welding, to control the laser scanner (4) so ​​that it directs the laser beam (LS) onto the surfaces of the components (2, 3) and at least partially melts the components (2, 3), and simultaneously to control the measuring unit (4.3) so that it automatically scans a generated melt (SM) using a measuring beam (MS) in a scanning motion and automatically determines depth data of a vapor capillary (DK) generated in the melt (SM) based on optical coherence tomography for different positions of the melt (SM) from measuring beam data (MD2), and - to compare the position-related depth data of the vapor capillary (DK) with the position-related reference data in a comparison process carried out simultaneously with or following welding, and to determine a position-related comparison depth of the vapor capillary (DK) in comparison to an initial state of the components (2, 3) existing before welding, wherein the measuring unit (4.3) is configured to emit at least one measuring beam (MS) into the at least one laser optic (4.2) in such a way that it is guided together with the laser beam (LS) to its point of impact.

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