Device and method for detecting and setting a weld penetration depth

Abstract

The invention relates to a device (1) for detecting and setting a weld penetration depth (ET) m1 , ET M2 ) in a laser beam welding process. According to the invention, the device comprises a laser emitter (5) for emitting two laser beams (LS1, LS2) onto the surface of a component (2) such that the laser beams (LS1, LS2) strike the surface in the welding direction (R) at successively arranged impact points and melt a material of the component (2) by forming at least one vapor capillary (DK), and a measuring device (4) for emitting two measuring beams (MS1, MS2) such that each measuring beam (MS1, MS2) is assigned to one of the laser beams (LS1, LS2) and is directed towards the corresponding impact point. The measuring device is used to determine the respective weld penetration depth (ET). m1 , ET M2) from component areas located below the points of impact below the measuring beams (MS1, MS2) reflected by at least one vapor capillary (DK). A control unit (3) is provided which controls the laser emitter (5) and at least sets parameters of the laser beam (LS2) further back in the welding direction (R) depending on the penetration depth (ET) determined in the area of ​​the front laser beam (LS1). M1 ) is trained. The invention further relates to a method for detecting and setting a weld penetration depth (ET) m1 , ET M2 ) in a laser beam welding process.

Description

[0001] The invention relates to a device for detecting and adjusting a welding depth in a laser beam welding process.

[0002] The invention further relates to a method for detecting and adjusting a welding depth in a laser beam welding process.

[0003] In laser beam welding, penetration depth is an important parameter for assessing weld quality. Defective welds with insufficient penetration depth require costly repairs (re-welding) or rejection.

[0004] EP 0 674 965 A1 discloses a method and device for monitoring the penetration depth in workpieces during laser beam welding. During a welding process, laser radiation reflected by a workpiece is continuously measured, and the penetration depth is determined by detecting a portion of the laser radiation reflected by the workpiece, which decreases accordingly when a vapor channel begins to form in the workpiece, simultaneously with a sudden increase in laser beam absorption. The device comprises a laser optics system arranged downstream of a laser in the beam path and focusing a laser beam onto a workpiece. The laser optics system has an element that decouples the laser radiation reflected from the workpiece, and a measuring device that detects the laser radiation is arranged downstream of the element in the direction of the decoupled, reflected laser radiation.

[0005] European patent application EP 1 923 165 A1 discloses a laser welding process with enhanced penetration. During laser welding of metal parts, a first laser beam is focused to form a keyhole, and a second laser beam is focused on the keyhole. The penetration depth of the second beam is greater than that of the first.

[0006] German patent application DE 10 2010 010 147 A1 relates to a beam welding method for welding multiple components. Furthermore, the invention relates to a beam welding device for carrying out the method. Disclosed is a beam welding method for welding multiple components, in which a preceding auxiliary welding beam generates an auxiliary molten pool, which is partially deepened transversely to the welding direction by a subsequent working welding beam to form a working molten pool. A vapor capillary formed by the auxiliary welding beam has a smaller penetration depth than a vapor capillary formed by the working welding beam.

[0007] PCT application WO 2018 / 136622 A1 discloses an apparatus comprising: a material processing beam source that generates a material processing beam applied to a sample location in a material modification process; an optical imaging source that generates imaging light; an optical interferometer that generates an interferometry output signal using at least one component of the imaging light directed onto the sample, the interferometry output signal being based on at least one length of an optical path to the sample compared to another length of an optical path; and a feedback controller that controls at least one processing parameter of the material modification process based on the interferometry output signal.

[0008] PCT application WO 2014 / 138 939 A1 discloses an apparatus comprising: an optical imaging source generating imaging light that is applied to a material processing system, the material processing system implementing a material modification process and generating a phase change region (PCR) in a material, at least one element directing the imaging light to a plurality of imaging beam positions proximate the PCR, at least one input / output port outputting a first component of the imaging light to an optical access port of the material processing system and receiving a reflection component of the imaging light, an optical combiner combining the reflection component and at least one other component of the imaging light to generate an interferometry output, the interferometry output being on a path length,traveled by the first component and the reflection component compared to a path length traveled by the at least one other component of the imaging light, and an interferometry output processor that processes the interferometry output to determine at least one characteristic of the PCR.

[0009] German patent DE 10 2022 004 289 B3 discloses a method for determining the penetration depth of a weld seam produced by a processing laser beam with the formation of a vapor capillary at a joint during a laser beam welding process, wherein: - a first measuring beam is directed from a first direction into the vapor capillary or onto a component surface surrounding the vapor capillary, wherein: - a second measuring beam is directed from a second direction different from the first direction into the vapor capillary, wherein: - a first return signal is detected based on a first return reflection of the first measuring beam, wherein a first distance is determined from the first return signal, wherein: - a second return signal is detected based on a second return reflection of the second measuring beam, wherein a second distance is determined from the second return signal, wherein: - the penetration depth of the weld seam is determined from the first distance and the second distance,and a device for determining a welding depth of a weld seam produced by a processing laser beam (5) with the formation of a vapor capillary at a joint during a laser beam welding process.

[0010] The invention is based on the object of providing a novel device and a novel method for detecting and adjusting a welding depth in a laser beam welding process.

[0011] The object is achieved according to the invention by a device which has the features specified in claim 1 and by a method which has the features specified in claim 4.

[0012] Advantageous embodiments of the invention are the subject of the subclaims.

[0013] The device for detecting and adjusting a welding depth in a laser beam welding process comprises, according to the invention, at least one laser emitter for emitting two laser beams onto a surface of a component in such a way that the laser beams impinge on the surface in the welding direction at successively arranged impact points and melt a material of the component, forming at least one vapor capillary. Furthermore, the device comprises a measuring device with - at least one emitter for emitting two measuring beams such that each measuring beam is assigned to one of the laser beams and is directed to the corresponding point of incidence, - at least one detector for detecting measuring beams reflected from a component area located below the at least one vapor capillary and - an evaluation unit for determining a respective welding depth at the component areas located below the impact points from the reflected measuring beams.Furthermore, the device comprises a control unit which is designed to control the laser emitter and at least to adjust parameters of the rear laser beam in the welding direction as a function of the welding depth determined in the area of ​​the front laser beam.

[0014] In the method for detecting and adjusting a welding depth in a laser beam welding process, according to the invention two laser beams are emitted onto a surface of a component in such a way that the laser beams impinge on the surface at impact points arranged one behind the other in the welding direction and melt a material of the component, forming at least one vapor capillary. Furthermore, two measuring beams are emitted in such a way that each measuring beam is assigned to one of the laser beams and is directed onto the associated impact point. Furthermore, measuring beams reflected from a component region located below the at least one vapor capillary are detected, wherein a respective welding depth at the component regions located below the impact points is determined from the reflected measuring beams.At least parameters of the rear laser beam in the welding direction are adjusted depending on the welding depth determined in the area of ​​the front laser beam in such a way that a predetermined target welding depth is achieved.

[0015] In this case, a vapor capillary is understood to be a hollow space filled with metal vapor or partially ionized metal vapor, for example in the shape of a tube, which is also referred to as a keyhole.

[0016] The device and method enable the absolute, qualitative measurement of the penetration depth with a specific measured value using the targeted measuring beams, which penetrate directly to a local depth of at least one vapor capillary and are reflected there by the non-evaporating or evaporated soil. This means that integrated quality assurance is implemented. The use of two measuring beams allows for a plausibility check of the measured values.

[0017] By using two laser beams and their associated measuring beams, an insufficient welding depth detected at the position of the front laser beam can be specifically adjusted or corrected using the rear laser beam, which follows the front laser beam. This means that the dual-beam technology enables the measured values ​​to be processed and the rear laser beam to respond accordingly to set the desired welding depth.

[0018] The device and method thus make it possible to determine the penetration depth during laser welding and to adjust it via inline control if the penetration depth deviates from a target value. This minimizes the effort required to repair defective welds, which in particular means carrying out additional welding processes, as well as component rejection in laser-welded components. This is particularly advantageous when laser welding thicker components, for example with material thicknesses of more than 2 mm, at moderate welding speeds. Furthermore, the device and method can be used flexibly for all laser-welded joints and lead to high process stability. The device can be implemented easily by combining it with modern system technology. It also enables the targeted creation of welds with different penetration depths.

[0019] Embodiments of the invention are explained in more detail below with reference to drawings.

[0020] Showing: Fig. 1 schematically shows a block diagram of a device for laser beam welding and a component during a welding process and Fig. 2 schematically shows a progression of welding depths and powers of laser beams as a function of a weld seam length or during the course of a weld.

[0021] Corresponding parts are provided with the same reference numerals in all figures.

[0022] In Fig. 1 shows a block diagram of a possible embodiment of a device 1 according to the invention for laser beam welding and a component 2 during a welding process.

[0023] The device 1 comprises a control unit 3 and a measuring device 4 with two emitters 4.1, 4.2, two detectors 4.3, 4.4, an evaluation unit 4.7, and two movable scanner mirrors 4.5, 4.6. Furthermore, the device 1 comprises at least one laser emitter 5 and a focusing lens 5.1.

[0024] To create a weld seam S, two laser beams LS1, LS2 are emitted by the laser emitter 5 and directed by the focusing lens 5.1 onto a surface of the component 2 such that the laser beams LS1, LS2 impinge on the surface in the welding direction R at consecutively arranged impact points and melt a material of the component 2. Alternatively, the laser emitter 5 comprises a laser beam source for emitting a source laser beam and a beam splitter for generating the two laser beams LS1, LS2 from the source laser beam.

[0025] At the same time, two measuring beams MS1, MS2 are emitted onto the scanner mirrors 4.5, 4.6 by means of the emitters 4.1, 4.2 of the measuring device 4 in such a way that each measuring beam MS1, MS2 is assigned to one of the laser beams LS1, LS2 and is directed to the corresponding point of incidence of the respective laser beam LS1, LS2.

[0026] The two laser beams LS1, LS2 melt the material of component 2, forming a vapor capillary DK which is elongated counter to the welding direction R and into which the measuring beams MS1, MS2 are directed.

[0027] Based on the measuring beam MS1 assigned to the front laser beam LS1 in the welding direction R, a welding depth ET M1up to a component area located below the vapor capillary DK at the position of the laser beam LS1. For this purpose, a reflection of the measuring beam MS1 is measured by means of the detector 4.3 of the measuring device 4. Furthermore, a welding depth ET is determined based on the measuring beam MS2 assigned to the rear laser beam LS2 in the welding direction R. M2 up to a component area located below the vapor capillary DK at the position of the laser beam LS2. For this purpose, a reflection of the measuring beam MS2 is measured using the detector 4.4 of the measuring device 4.

[0028] To reliably detect and distinguish the reflections of the measuring beams MS1, MS2, the two measuring beams MS1, MS2 can be emitted and detected at different wavelengths using separate emitters 4.1, 4.2 and separate detectors 4.3, 4.4. In one possible embodiment, the measuring beams MS1, MS2 are each emitted at a different wavelength than the laser beams LS1, LS2. In one possible embodiment, the measuring beams MS1, MS2 are designed as laser beams.

[0029] To determine the corresponding welding depth ET M1 , ET M2 the measured values ​​of the reflections of the measuring beams MS1, MS2 are fed to the evaluation unit 4.7.

[0030] The evaluation unit 4.7 determines whether the welding depth ET generated by the front laser beam LS1 M1 from a specified target welding depth ET SIf this is the case, the measuring device 4 sends a command to adjust the parameters of the rear laser beam LS2 to the control unit 3, which, for example, increases the welding depth ET M1 , ET M2 one in Fig. 2 increases the power P2 of the rear laser beam LS2 or reduces the welding depth ET M1 , ET M2 the power P2 of the rear laser beam LS2 is reduced. Using the measuring beam MS2 assigned to the rear laser beam LS2, the welding depth ET generated by the rear laser beam LS2 can then be determined. M2 can be checked using the evaluation unit 4.7.

[0031] Fig. 2 shows a possible course of the welding depths ET M1 , ET M2 , the target welding depth ET S . and powers P1, P2 of the laser beams LS1, LS2 depending on a weld seam length X or a weld path.

[0032] These curves illustrate that when determining a welding depth ET generated by the front laser beam LS1 with power P1 M1 which is temporarily less than the target welding depth ET S is, the power P2 of the rear laser beam LS2 at the positions of the reduced welding depth ET M1 is increased such that the resulting welding depth ET M2 the weld seam S over the entire weld seam length X of the target welding depth ET S corresponds.

Claims

[1] Device (1) for detecting and setting a welding depth (ET m1 , ET M2 ) in a laser beam welding process, characterized by - a laser emitter (5) for emitting two laser beams (LS1, LS2) onto a surface of a component (2) in such a way that the laser beams (LS1, LS2) impinge on the surface in the welding direction (R) at successively arranged impact points and melt a material of the component (2) to form at least one vapor capillary (DK), - a measuring device (4) with - at least one emitter (4.1, 4.2) for emitting two measuring beams (MS1, MS2) such that each measuring beam (MS1, MS2) is assigned to one of the laser beams (LS1, LS2) and is directed to the associated point of incidence, - at least one detector (4.3, 4.4) for detecting measuring beams (MS1, MS2) reflected from a component area located below the at least one vapor capillary (DK), - an evaluation unit (4.7) for determining a respective welding depth (ET M1 , ET M2 ) at the component areas below the impact points from the reflected measuring beams (MS1, MS2), - a control unit (3) which is used to control the laser emitter (5) and at least to adjust parameters of the rear laser beam (LS2) in the welding direction (R) as a function of the welding depth (ET m1 ) is trained. [2] Device (1) according to claim 1, characterized by that the laser emitter (5) comprises a laser beam source for emitting a source laser beam and a beam splitter for generating the two laser beams (LS1, LS2) from the source laser beam. [3] Device (1) according to claim 1, characterized by that the laser emitter (5) comprises two laser beam sources for the separate emission of the two laser beams (LS1, LS2). [4] Method for detecting and setting a welding depth (ET M1, ET M2 ) in a laser beam welding process, characterized by , that - two laser beams (LS1, LS2) are emitted onto a surface of a component (2) in such a way that the laser beams (LS1, LS2) impinge on the surface in the welding direction (R) at successively arranged impact points and melt a material of the component (2) to form at least one vapor capillary (DK), - two measuring beams (MS1, MS2) are emitted in such a way that each measuring beam (MS1, MS2) is assigned to one of the laser beams (LS1, LS2) and is directed to the corresponding point of incidence, - reflected measuring beams (MS1, MS2) are detected at a component area located below the at least one vapor capillary (DK), - a respective welding depth (ET m1 , ET M2 ) is determined from the reflected measuring beams (MS1, MS2) at the component areas below the impact points, - at least parameters of the rear laser beam (LS2) in the welding direction (R) as a function of the welding depth (ET) determined in the area of ​​the front laser beam (LS1) M1 ) can be adjusted in such a way that a specified target welding depth (ET S ) is reached. [5] Method according to claim 4, characterized by that the two measuring beams (MS1, MS2) are emitted with a different wavelength. [6] Method according to claim 4 or 5, characterized bythat the two measuring beams (MS1, MS2) are emitted with a different wavelength than the laser beams (LS1, LS2). [7] Method according to one of claims 4 to 6, characterized by that the two measuring beams (MS1, MS2) are laser beams.

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