Method for welding pre-machined components

Abstract

The invention relates to a method for welding pre-processed components (B), wherein the components (B) are electrical conductors and conductor ends (L) of the electrical conductors, from which an insulating sheath (M) has been removed prior to welding, are welded, wherein, prior to welding, component surfaces of the components (B) in a butt geometry joined for welding are scanned by means of a measuring beam system and thereby a measurement signal (MS) is detected, wherein a shape of the detected measurement signal (MS) depends on a height profile of the butt geometry and an intensity (I) of the detected measurement signal (MS) depends on the materials of the conductor ends (L) and insulating sheaths (M), and wherein the welding is only carried out if the detected measurement signal (MS) corresponds in shape and intensity (I) to a predetermined signal pattern.

Description

[0001] The invention relates to a method for welding pre-machined components.

[0002] From the prior art, as described in DE 10 2020 120 649 A1, a method for determining a position of a workpiece for a laser processing process is known. The method comprises irradiating a measuring beam onto at least one workpiece and a carrier device surrounding the at least one workpiece along at least one first measuring path and along at least one second measuring path, wherein the first measuring path has a predetermined angle with the second measuring path, detecting a portion of the irradiated measuring beam reflected by the carrier device and the at least one workpiece along the first measuring path and along the second measuring path and generating a corresponding measuring signal, wherein the carrier device and the at least one workpiece have a different reflectivity from one another, and determining a position of the at least one workpiece based on the measuring signal.

[0003] DE 10 2020 210 778 A1 describes a method for monitoring and / or controlling a laser welding process based on an OCT-detected melt or weld bead geometry as well as an associated processing machine and an associated computer program product.In the method for monitoring and / or controlling a laser welding process for welding two workpieces made of metallic material by means of a processing laser beam which is directed onto adjacent end faces of the workpieces in order to melt a molten pool at the two end faces and subsequently a molten bead which then solidifies into a weld bead, the liquid molten pool and / or the liquid molten bead is scanned in a line scan during the laser welding process by means of an OCT measuring beam, an actual geometry of the molten pool and the molten bead is determined based on the line scan and a welding parameter is set based on a deviation of the determined actual geometry from a predetermined target geometry of the molten pool and the molten bead.After the laser welding process, the solidified weld bead is scanned using an OCT measuring beam in a line scan, an actual geometry of the weld bead is determined based on the line scan, and the quality of the weld bead is monitored based on a deviation of the determined actual geometry from a specified target geometry of the weld bead.

[0004] EP 3 865 242 A1 discloses a welding method and a welding device for welding conductor ends. The welding method comprises detecting a relative position of a first conductor end and a second conductor end of a conductor end group and controlling the welding energy input to the conductor ends to be welded depending on the detected relative position.

[0005] DE 10 2007 016 444 A1 describes a processing device comprising a processing head configured to provide a high-energy processing beam. Associated with the processing head is a scanning device configured as an optical coherence tomograph, which is designed for surface scanning.

[0006] The invention is based on the object of providing a method for welding pre-machined components that is improved compared to the prior art.

[0007] The object is achieved according to the invention by a method for welding pre-machined components having the features of claim 1.

[0008] Advantageous embodiments of the invention are the subject of the subclaims.

[0009] In a method for welding pre-machined components, it is provided in particular that the components are welded, wherein before and / or after welding, component surfaces of the components in the joint geometry joined together for welding are scanned by means of a measuring beam system and a measuring signal is thereby recorded, wherein a shape of the recorded measuring signal is dependent on a height profile of the joint geometry and / or an intensity of the recorded measuring signal is dependent on materials and surface conditions of the components, wherein the welding is only carried out if the recorded measuring signal corresponds to a predetermined signal pattern in terms of depth, shape and / or intensity, and wherein it is provided in particular that the quality of the components is determined in the initial state before and / or in the initial state after welding.

[0010] The components are in particular electrical conductors and conductor ends of the electrical conductors from which an insulating sheath was removed before welding.

[0011] In a method for welding pre-machined components, in particular in the method described above, it is provided in particular that the components are in particular electrical conductors, in particular of a stator coil of an electrical machine, in particular so-called hairpins, and conductor ends of the electrical conductors, from which an insulating sheath, for example a varnish or another insulating material, was removed before welding, are welded. It is provided in particular that, in particular before welding, component surfaces of the components are scanned by means of a measuring beam system in the joint geometry assembled for welding, iein particular are scanned by at least one measuring beam of the measuring beam system, and thereby a measuring signal is recorded, wherein a shape of the recorded measuring signal depends on a height profile of the joint geometry and / or an intensity of the recorded measuring signal depends on materials and / or surface conditions of the conductor ends and insulation sheaths. In particular, an OCT system (OCT = Optical Coherence Tomography) is used as the measuring beam system. The intensity of the recorded measuring signal is recorded in particular as a gray value. Sections of the measuring signal relating to the material of the insulation sheath in particular have a different intensity than sections of the measuring signal relating to the material of the conductor ends.

[0012] Welding is only performed if the measured signal corresponds to a specified signal pattern in terms of depth, shape, and / or intensity, or deviates from it only within specified limits. Welding is performed primarily using laser beam welding.

[0013] The described solution is therefore particularly a method for both quality control and laser welding of machined component joints.

[0014] The solution described is primarily based on the problem that welding pre-machined components, such as hairpins, using a laser beam can only be successful with good pre-processing. The quality of the pre-processing processes, such as paint stripping, must be carefully ensured and tested, as inadequate component preparation, particularly from residual pre-processing, can result in poor weld seam quality, caused, for example, by the evaporation of paint residues during the welding process and the resulting pore formation in the melt. Therefore, a separate quality inspection has been performed immediately after the pre-processing process, for example, using a camera or fluorescence analysis. However, this is very complex and costly.This can be avoided by the solution described, in particular by examining the joined joint geometry of the components before welding in the manner described using the measuring beam system.

[0015] The described solution thus utilizes one, particularly multiple, application of the measuring beam system, for example, OCT, to determine the quality of the pre-processing process, for example, paint stripping or other removal of the insulation jacket and / or a cutting process, by scanning the component surfaces in the joined joint geometry. Information on the status of the pre-processing process and the component arrangement can be obtained directly from the measurement signal, so that a processing laser beam for laser beam welding can be positioned immediately to execute the welding operation, provided the measurement signal is correct.

[0016] As already mentioned, sections of the acquired measurement signal differ, on the one hand, in their height profile due to the scanned joint geometry, and, on the other hand, in their intensity, particularly in the form of gray values, due to the different materials traversed by the measurement beam during the scan. Different sections of the measurement signal occur in hairpins that have been partially stripped of paint, i.e., freed from the insulation sheath, with a bare copper base material and the surrounding insulation sheath, especially paint.

[0017] After this first scan using the measuring beam system and the subsequent welding operation, in one possible embodiment of the method, a further scan can be performed using the measuring beam system to assess the weld quality. In this embodiment, the measuring beam system is used both for the incoming inspection and positioning of the components to be welded and for the outgoing inspection of the welded joint, advantageously in a single cycle. The described solution thus advantageously enables time and cost savings due to multiple applications of the measuring beam system in a single cycle.

[0018] By means of the measuring beam system, in particular from the signal intensities of the recorded measuring signal, it is possible to detect different surface conditions, for example, detection of oxidation and / or detection of paint residues and / or other defects in the pre-processing.

[0019] The described solution can be implemented particularly advantageously with a system technology that is already in use, so that no adjustments or additions of components are required on the device side.

[0020] The described solution is applicable to all weldable joint geometries, such as fillet welds, butt welds, and other weld seam variants. The described solution is also applicable to all material combinations.

[0021] The described solution is particularly suitable for applications in combination with laser beam welding, in particular in combination with laser scanner welding optics, in particular for welding stripped hairpins for an electrical machine.

[0022] The described solution enables a reduction in rejects and an improvement in welding quality through the incoming goods inspection carried out in the manner described using the measuring beam system.

[0023] As an alternative to the components designed as electrical conductors, other pre-processed components can also be scanned using the measuring beam system in a corresponding manner using the method and, if the acquired measuring signal corresponds in form and intensity to at least a predetermined signal pattern, can be welded together.

[0024] Embodiments of the invention are explained in more detail below with reference to drawings.

[0025] Showing: Fig. 1 schematically shows a process for welding pre-machined components with a correct measurement signal, Fig. 2 schematically shows a process for welding pre-machined components in the case of an incorrect measurement signal, and Fig. 3 schematically shows an exemplary depth signal and intensity signals of the scanning of a component and a brightness curve as a function of an intensity level.

[0026] Corresponding parts are provided with the same reference numerals in all figures.

[0027] The Fig. 1 and Fig. 2 show two different processes for welding pre-machined components B. An alignment of the components B in the y-direction y and z-direction z is shown using a Fig. 1 and Fig. 2 shown coordinate system.

[0028] In the illustrated examples, the method is carried out using a device 1 comprising a combination of a laser beam welding system and a measuring beam system. In the illustrated example, the measuring beam system is integrated into a laser welding optics 2 of the laser beam welding system, with at least some mirrors 3, in particular a scanner mirror 4, being used by both the measuring beam system and the laser beam welding system.

[0029] An OCT system is used as the measuring beam system.

[0030] In the examples shown, components B are electrical conductors, in particular of a stator coil of an electrical machine, specifically so-called hairpins. The conductor ends L of the electrical conductors, from which an insulating sheath M, for example, a varnish or other insulating material, was removed prior to welding, are welded.

[0031] The components B are in the Fig. 1 and Fig. 2 are shown on the left in a joint geometry intended for welding.

[0032] The method provides that, prior to welding, the component surfaces of the components B are scanned in the joint geometry assembled for welding using the measuring beam system, i.e., in particular, they are scanned by at least one measuring beam MST generated, in the example shown, by a measuring beam control unit 5 of the measuring beam system. In the examples shown, this scanning is performed by moving the measuring beam MST across the assembled joint geometry of the components B using the scanner mirror 4.

[0033] This way, a measurement signal MS is acquired, whereby a shape of the acquired measurement signal MS depends on a height profile of the impact geometry in the z-direction z. In the example according to Fig. 1, the upper lines of the measurement signal MS result from scanning a surface of the conductor ends L and the lower lines result from scanning a surface of the insulation sheaths M.

[0034] Furthermore, the intensity I of the recorded measurement signal MS depends on the materials of the components B, ie the conductor ends L and insulation sheaths M. The intensity I of the recorded measurement signal MS is recorded in particular as a gray value, as shown for example in Fig. 3. Here, the scanning of one of the components B is shown as an example. Sections of the measurement signal MS that relate to the material of the insulation jacket M, in particular a varnish from which the insulation jacket M is formed, have a different intensity I than sections of the measurement signal MS that relate to the material of the conductor ends L, in particular copper.

[0035] In Fig. 3 The component B is shown below, along whose surface the scanning is carried out from left to right or from right to left. The intensity I of the measurement signal MS is shown above this. As can be seen here, the measurement signal MS has a lower intensity I in the section resulting from the scanning of the insulation sheath M than in the section resulting from the scanning of the conductor end L, since the material of the insulation sheath M, in particular varnish, has a lower reflectivity for the measurement signal MS than the material of the conductor end L, in particular copper. The intensity I is also shown as a gray value of the measurement signal MS. The higher the intensity I of the measurement signal MS, the brighter the displayed measurement signal MS or the respective section of the measurement signal MS, as in Fig. 3 shown in an intensity curve at the top right.

[0036] In Fig. 3, depth information T or height information of the measurement signal MS corresponding to the height profile of the scanned surface of the component B is also shown at the top left.

[0037] The welding is only carried out if the measured signal MS corresponds to a given signal pattern in depth and / or shape and / or intensity I. In Fig. 1, this is the case, so that the components B, in particular their conductor ends L, are subsequently welded, in the example shown by laser beam welding. For this purpose, a laser processing beam LST is directed onto the components B to be welded by means of the laser welding optics 2 and, in particular, is moved over an area of ​​the components B to be welded by means of the scanner mirror 4. In Fig. 1 the two components B welded together are shown on the right.

[0038] In contrast to the example according to Fig. 1 corresponds in the example according to Fig. 2 the recorded measurement signal MS in form and intensity I does not correspond to the specified signal pattern. In the example shown, this results from the fact that the insulation sheath M on the component B shown on the right was not removed from the conductor end L. As a result, the sections of the measurement signal MS that result from the scanning of the insulation sheath M of the component B shown on the right, in particular, have different depth information T, ie they are located at the same height in the measurement signal MS as the section of the measurement signal MS that results from the scanning of the conductor end L of the component B shown on the right. Due to this, the welding in the example according to Fig.2 is not performed. For example, an error message or other information is output so that these components B, or at least the component B shown on the right, can be removed and the process can be performed with other components B. The incorrectly pre-machined component B on the right can then, for example, be sent for pre-machining again. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 120 649 A1

[0002] DE 10 2020 210 778 A1

[0003] EP 3 865 242 A1

[0004] DE 10 2007 016 444 A1

[0005]

Claims

[1] Method for welding pre-machined components (B), wherein the components (B) are electrical conductors and conductor ends (L) of the electrical conductors, from which an insulating sheath (M) was removed before welding, are welded, wherein before welding, component surfaces of the components (B) are scanned by means of a measuring beam system in a joint geometry joined together for welding, and a measuring signal (MS) is thereby recorded, wherein a shape of the recorded measuring signal (MS) is dependent on a height profile of the joint geometry and an intensity (I) of the recorded measuring signal (MS) is dependent on materials of the conductor ends (L) and insulating sheaths (M), and wherein welding is only carried out if the recorded measuring signal (MS) corresponds in shape and intensity (I) to a predetermined signal pattern. [2] Method according to claim 1, characterized by that the intensity (I) of the acquired measurement signal (MS) is recorded as a gray value. [3] Method according to one of the preceding claims, characterized by that sections of the detected measuring signal (MS) relating to the material of the insulation sheath (M) have a different intensity (I) than sections of the detected measuring signal (MS) relating to the material of the conductor ends (L). [4] Method according to one of the preceding claims, characterized by that an OCT system is used as the measuring beam system. [5] Method according to one of the preceding claims, characterized by that the welding is carried out by laser beam welding.

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