Method and laser welding device for producing a welded joint

Abstract

Method for producing a welded joint (S) in the area of ​​a joint between at least two components (2, 3) by means of a laser beam (LS) emitted by means of a laser welding device (1), wherein - at least one reference distance (z) before welding. 1.1 , z 1.2 ) at least one surface of each of the components (2, 3) is determined to at least one reference plane (RE) formed on the laser welding device (1), - then, during welding, the laser beam (LS) is directed onto the surfaces of the components (2, 3), the components (2, 3) are at least partially melted, and the weld joint (S) is created by the solidification of a generated melt, - after welding and solidification of the melt, at least a surface distance (z2) of a surface of the solidified melt (eS) to which at least one reference plane (RE) is determined, - a ratio between at least one reference distance (z 1.1 , z 1.2 ) and at least one surface distance (z2) is determined and - depending on the size of the ratio, it is determined whether the produced welded joint (S) meets specified quality requirements.

Description

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

[0002] The invention further 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.

[0003] 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, - 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.

[0004] DE 10 2022 127 484 A1 discloses a laser processing head comprising a housing in which at least one optic for directing the laser beam onto a processing point on the workpiece is arranged; at least one frequency-modulated and / or amplitude-modulated continuous-wave lidar sensor for detecting a distance to at least one point on the workpiece, wherein the lidar sensor comprises an emitter and a detector; and a control system for monitoring and / or controlling and / or regulating the processing process based on the detected distance; as well as a corresponding method for carrying out a laser processing process.

[0005] EP 3 865 242 A1 discloses the following: To improve quality and reduce scrap in the mass production of components for an electric machine equipped with coil windings, the invention provides a welding method for welding conductor ends of a component for an electric machine that are grouped into conductor end groups, comprising: a) detecting the relative position of a first conductor end and a second conductor end of a conductor end group and b) controlling the input of welding energy to the conductor ends to be welded depending on the detected relative position. A welding device for carrying out the welding method is also proposed.

[0006] DE 10 2023 004 313 A1 discloses a method for producing a welded joint for joining two components, in which the two components, each having an end-face joining surface, are arranged side by side in a welding device such that the two joining surfaces are adjacent to each other, in which a spatial position of the two joining surfaces is measured, in which the welding process for producing the welded joint is carried out in such a way that the welded joint joins the two joining surfaces together, in which a spatial shape and spatial position of the produced welded joint are measured, in which a spatial actual shape of the produced welded joint is determined from the measured shape and position of the produced welded joint in conjunction with the measured position of the joining surfaces.- in which, by comparing the actual shape of the welded joint produced with shapes of good and bad welded joints stored in a database, it is determined whether the welded joint produced is a good or bad welded joint.

[0007] The invention is based on the objective of providing a novel method and a novel laser welding device for producing a welded joint.

[0008] The problem is solved according to the invention by a method which has the features specified in claim 1 and by a laser welding device which has the features specified in claim 7.

[0009] Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] In the inventive method for producing a welded joint in the area of ​​a joint between at least two components by means of a laser beam emitted by means of a laser welding device - Before welding, at least one reference distance is determined between at least one surface of each component and at least one reference plane formed on the laser welding device. - If the laser beam is then directed onto the surfaces of the components during welding, the components are at least partially melted and the weld joint is created by the solidification of the resulting molten metal. - After welding and solidification of the melt, at least one surface distance of a surface of the solidified melt to at least one reference plane is determined, - a ratio is determined between at least one reference distance and at least one surface distance and - It is determined, depending on the size of the ratio, whether the produced welded joint meets specified quality requirements.

[0011] 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 makes it impossible to reference other components or component edges during welding. In this case, due to the lack of reference, the penetration depth or the depth of a 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.

[0012] Methods known from the prior art, in which the measurement is referenced to unmelted component edges during welding, are not applicable for the aforementioned applications involving melting of the component edges.

[0013] The present method advantageously enables, by determining the reference distances before welding, the referencing of the welded joint and quality assurance of the resulting weld joint, even when component edges completely melt during the welding process. Since at least one reference plane is formed on the laser welding device, it remains unchanged during welding. For example, at least one reference plane is formed on a holding tool, such as a hold-down clamp, used to fix the components together. The determination of the reference distances and surface distances can be carried out in all spatial directions, i.e., vertically, horizontally, and longitudinally.Due to the referencing of the laser welding device performing the laser welding process and, if applicable, further information known from the welding process, such as the depth of a vapor capillary in a generated melt, the method enables control of the welding process, for example by adjusting the focus and / or power of the laser beam.

[0014] The determination of reference distances in a welding process where multiple welds are produced can be carried out, in particular, before each individual weld, i.e., separately for each weld. It is also possible to determine the reference distances for several or all welds to be produced in such a welding process before the welding operations are carried out. This enables unambiguous and reliable referencing.

[0015] 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.

[0016] Furthermore, the process is at least almost cycle time-neutral and consequently cost-neutral, while simultaneously improving measurements and ensuring high process reliability.

[0017] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0018] 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. Fig. 2 schematically a course of measurement beam data of a surface of the components according to Fig. 1 before the creation of the weld joint and the course superimposed with measuring ranges and a reference plane and Fig. 3 schematically shows a course of measurement beam data of a surface of a welded joint according to Fig. 1 and the curve superimposed with measuring ranges and a reference plane.

[0019] Corresponding parts are marked with the same reference symbols in all figures.

[0020] 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.

[0021] 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.

[0022] The laser welding device 1 further comprises a measuring device 5 integrated into the laser optics 4.2, with a measuring unit 5.1 configured to emit a measuring beam MS onto an optical element 5.2 arranged in the laser optics 4.2. The optical element 5.2 is configured to direct the measuring beam MS onto the optical element 4.2.1. For this purpose, the optical element 5.2 is designed to pivot 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 A1 to An on the components 2, 3 and a reference plane RE. Furthermore, the measuring unit 5.1 is configured to detect reflected components of the measuring beam MS and to determine the measurement beam based on the reflected components and the values ​​stored in the optical elements 4.2.1 to 4.2.3. Fig. 2 and Fig. 3. Based on the measurement beam data MD1, MD2 shown in more detail, a distance from the respective point of impact A1 to An to the laser optics 4.2 is determined automatically on the basis of optical coherence tomography.

[0023] Furthermore, the laser welding device 1 has a control unit 6 which is digitally coupled to the laser emitter 4.1, the optical elements 4.1.1, 4.1.2, 5.2 and the measuring unit 5.1 for controlling the laser emitter 4.1, the optical elements 4.1.1, 4.1.2, 5.2 and the measuring unit 5.1.

[0024] 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.

[0025] To fix components 2, 3 relative to each other and to realize a technical zero gap between components 2, 3, these are arranged in a holding tool 7 of the laser welding device 1.

[0026] For a mechanical connection, and, if the components 2 and 3 are configured as hairpins, an electrical connection, they are joined together by means of the laser beam LS emitted by the laser welding device 1 and directed onto their surfaces, forming the weld joint S. For this purpose, the surfaces of the components 2 and 3 facing the laser optics 4.2 are melted, whereby the weld joint S forms in the area of ​​a solidified melt eS.

[0027] To determine the quality of the welded joint S, it is necessary, among other things, to measure the welded joint S at least after its creation. In order to obtain meaningful results from the measurement data, it is necessary to reference it to the state of components 2, 3 before they were welded.

[0028] To create the weld joint S, in the illustrated embodiment, the surfaces of components 2 and 3 are completely melted, including their upper edges facing the laser optics 4.2. Therefore, it is not possible to reference the resulting weld joint S to the surfaces of components 2 and 3 and their edges.

[0029] To still allow for referencing, it is planned that at least one [unclear] will be [unclear] before welding. Fig. 2. Reference distance shown in more detail z 1.1 , z 1.2 The reference plane RE of at least one surface of each of the components 2, 3 is determined to at least one reference plane RE formed on the laser welding device 1. In this case, the reference plane RE is formed on a surface of the holding tool 7 facing the laser optics 4.2.

[0030] Determining the reference distances z 1.1 , z 1.2In the present embodiment, this is carried out by means of the measuring unit 5.1, which – as described above – guides the measuring beam MS over the optical elements 5.2, 4.2.1 to 4.2.3 onto the surface of the components 2, 3 and the reference plane RE and determines, based on optical coherence tomography, the distances of the impact points A1 to An located on the surface of the components 2, 3 and the reference plane RE to the laser optics 4.2. The measuring unit 5.1 and the optical elements 5.2, 4.2.1, 4.2.2 are controlled accordingly by the control unit 6. This is shown in the left-hand illustration of the Fig. 1 shown.

[0031] The measurement beam data MD1 determined using measuring unit 5.1 are in Fig. 2 are shown schematically for the present embodiment and are transferred to the control unit 6, which stores them.

[0032] Alternatively or additionally, the measuring device 5 can, in a manner not shown in detail, include at least one distance measuring sensor which measures the reference distances z. 1.1 , z 1.2 determined based on a triangulation principle.

[0033] After determining and storing the reference distances z 1.1 , z 1.2 The welding process – as shown in the right-hand illustration – Fig. 1 shown - carried out, wherein during welding the laser beam LS is directed onto the surfaces of the components 2, 3, the surfaces of the components 2, 3 facing the laser optics 4.2 are completely melted and the weld joint S is created by solidification of a generated melt.

[0034] For this purpose, the control unit 6 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 melted on their surface. A melt (not shown in detail) is thereby created, whereby a vapor capillary (not shown in detail) forms in the melt in the area of ​​the laser beam LS.

[0035] In one possible embodiment, the control unit 6 simultaneously controls the measuring unit 5.1 during welding in such a way that the measuring unit uses a measuring beam MS in a scanning motion to automatically scan the generated melt and automatically determine depth data of the vapor capillaries generated in the melt based on optical coherence tomography. In particular, the measuring beam MS is positioned such that it is directed onto the same point of impact A1 to An as the laser beam LS is directed onto components 2, 3.

[0036] In particular, the laser scanner 4 is controlled by the control unit 6 during welding in such a way that the welding process is regulated. Depending on the depth data of the vapor capillary acquired during welding, the regulation can, for example, be carried out such that a minimum melting depth of the components 2, 3 is reached or exceeded by adjusting the focus and / or power of the laser beam LS.

[0037] If it is planned that several weld joints S will be produced in succession, the previously described determination of the reference distances z can be used. 1.1 , z 1.2 S must be performed before each welding process, either separately or for several or all weld joints to be produced, before the welding processes are carried out.

[0038] Furthermore, after welding and solidification of the melt, the control unit 6 activates the measuring unit 5.1 such that a measuring beam MS scans the surface of the solidified melt eS. This process automatically generates data based on optical coherence tomography from received and processed data. Fig. 3 more detailed measurement beam data MD2 determines at least one surface distance z2 of a surface of the solidified melt eS to at least one reference plane RE.

[0039] Between the reference distances z 1.1 , z 1.2 For each surface distance z2, a ratio is determined, and depending on the size of the ratio, it is determined whether the welded joint S produced meets specified quality requirements.

[0040] Depending on whether the generated weld joint S meets specified quality requirements, parameters of the laser beam LS are set for post-processing of the weld joint S and / or for generating further weld joints S and / or a declaration of a component arrangement having the weld joint S as a good part or bad part is carried out.

[0041] Fig. Figure 2 shows the course of the measurement beam data MD1 of the surface of components 2, 3 according to the left-hand diagram. Fig. 1 before the creation of the weld joint S. From the measuring beam data MD1, analogous to the description of the Fig. 1 the reference distances z 1.1 , z 1.2 The surface of components 2 and 3 is determined in relation to the reference plane RE. The reference distances z are determined in this process. 1.1 , z 1.2 in the vertical direction z along the longitudinal direction x.

[0042] In the right-hand representation of the Fig. Figure 2 shows the course of the measurement beam data MD1 with measurement ranges MB1 to MB3 and a visualization of the reference plane RE superimposed.

[0043] The measuring ranges MB1 to MB3 represent windows with regions of interest, where the measuring beam data MD1 running in measuring range MB1 represents the distance of the surface of component 2 to the laser optics 4.2, the measuring beam data MD1 running in measuring range MB2 represents the distance of the surface of component 3 to the laser optics 4.2, and the measuring beam data MD1 running in measuring range MB3 represents the distance of the surface of the reference plane RE to the laser optics 4.2 in the initial state of components 2, 3 and the reference plane RE before welding components 2, 3.

[0044] The reference distances z are determined from the distances of the surfaces of components 2, 3 to the laser optics 4.2 relative to the distance of the reference plane RE to the laser optics 4.2. 1.1 , z 1.2the surfaces of components 2, 3 are formed relative to the reference plane RE. Additionally, z describes... 1m the mean of the reference distances z 1.1 z 1.2 .

[0045] In Fig. Figure 3 in the left-hand diagram shows the course of the measurement beam data MD2 of the surface of the solidified melt eS according to Fig. 1 after the creation of the weld joint S is shown. From the measuring beam data MD2, analogous to the description of the Fig. 1. The surface distance z2 of the surface of the solidified melt eS to the reference plane RE is determined. The surface distance z2 is determined in the vertical direction z along the longitudinal direction x.

[0046] In the right-hand representation of the Fig. Figure 3 shows the course of the measurement beam data MD2 with measurement ranges MB3, MB4 and a visualization of the reference plane RE superimposed.

[0047] The measuring ranges MB3 and MB4 represent windows with regions of interest, where the measuring beam data MD2 running in the measuring range MB4 represents the distance of the surface of the solidified melt eS to the laser optics 4.2 and the measuring beam data MD2 running in the measuring range MB3 represents the distance of the surface of the reference plane RE to the laser optics 4.2 after the creation of the weld joint S.

[0048] From the distance of the surface of the solidified melt eS to the laser optics 4.2 relative to the distance of the reference plane RE to the laser optics 4.2, the surface distance z2 of the surface of the solidified melt eS to the reference plane RE is formed.

[0049] With the reference distances z 1.1 , z 1.2 A ratio V to the surface distance z2 is then determined according to V=z1m / z2 educated.

[0050] The following criteria, for example, are used as a basis: z1m≤1.5*z2 Δz1m=z1.1−z1.2≤|3,0 mm| z1m=(z1.1+z1.2) / 2

[0051] The ratio V is then used to determine whether the resulting weld S meets specified quality requirements. For example, the weld S is classified as "OK" and thus meets the quality requirements if V ≤ 0.3. In such a case, a component assembly featuring the weld S is declared a good part. Conversely, the weld S is classified as "not OK" and thus does not meet the quality requirements if V > 0.3. In such a case, a component assembly featuring the weld S is declared a defective part.

[0052] In contrast to the two-dimensional representation of the measurement beam data MD1, MD2 shown, the measuring unit 5.1 and control unit 6 can also be designed in such a way that emission of measurement beams MS and acquisition of the measurement beam data MD1, MD2 in several planes is possible, so that a complete three-dimensional profile of the respective acquired surface of the components 2, 3 and the reference plane RE before welding, the melt and the vapor capillary during welding and the solidified melt eS after welding can be created from the measurement beam data MD1, MD2.

Claims

[1] Method for producing a welded joint (S) in the area of ​​a joint between at least two components (2, 3) by means of a laser beam (LS) emitted by means of a laser welding device (1), wherein - at least one reference distance (z) before welding. 1.1 , z 1.2 ) at least one surface of each of the components (2, 3) is determined to at least one reference plane (RE) formed on the laser welding device (1), - then, during welding, the laser beam (LS) is directed onto the surfaces of the components (2, 3), the components (2, 3) are at least partially melted, and the weld joint (S) is created by the solidification of a generated melt, - after welding and solidification of the melt, at least a surface distance (z2) of a surface of the solidified melt (eS) to which at least one reference plane (RE) is determined, - a ratio between at least one reference distance (z 1.1 , z 1.2 ) and at least one surface distance (z2) is determined and - depending on the size of the ratio, it is determined whether the produced welded joint (S) meets specified quality requirements. [2] Method according to claim 1, wherein the at least one reference distance (z 1.1 , z 1.2 ) and / or at least one surface distance (z2) is determined from measurement beam data (MD1, MD2) determined on the basis of optical coherence tomography, wherein the measurement beam data (MD1, MD2) are determined by means of a measuring unit (5.1) by which a measurement beam (MS) is emitted onto the surfaces of the components (2, 3) and the surface of the solidified melt (eS) and the measurement beam data (MD1, MD2) is formed from detected components of the measurement beam (MS) reflected at the respective surface. [3] Method according to claim 2, wherein the measuring beam (MS) is guided into a laser optic (4.2) of the laser beam device (1) by means of the measuring unit (5.1) and is directed by means of this onto the surfaces of the components (2, 3) and the surface of the solidified melt (eS). [4] Method according to claim 3, wherein the measuring beam (MS) is guided together with the laser beam (LS) to the same point of impact (A1 to An) during welding by means of the laser optics (4.2). [5] Method according to claim 1 or 2, wherein the at least one reference distance (z 1.1 , z 1.2 ) and / or at least one surface distance (z2) is determined / will be determined using a distance measuring sensor based on a triangulation principle. [6] Method according to one of the preceding claims, wherein, depending on whether the produced weld joint (S) meets specified quality requirements, parameters of the laser beam (LS) are set for post-processing of the weld joint (S) and / or for producing further weld joints (S) and / or a declaration of a component arrangement having the weld joint (S) as a good part or bad part is carried out. [7] 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 device (5) which is designed to determine a distance to a surface, - a control unit (6) which is designed, - to activate the measuring device (5) before welding, at least one reference distance (z) in each case 1.1 , z 1.2 ) to determine at least one surface of each of the components (2, 3) to at least one reference plane (RE) formed on the laser welding device (1), - then, during welding, to control the laser scanner (4), to direct the laser beam (LS) onto the surfaces of the components (2, 3) in such a way that the components (2, 3) are at least partially melted and the weld joint (S) is created by the solidification of a generated melt, - after welding and solidification of the melt, to control the measuring device (5) to determine at least one surface distance (z2) of a surface of the solidified melt (eS) to the at least one reference plane (RE), - a ratio between at least one reference distance (z 1.1 , z 1.2 ) and to determine at least one surface distance (z2) and - to determine, depending on the size of the ratio, whether the produced welded joint (S) meets specified quality requirements.

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