Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/03—Observing, e.g. monitoring, the workpiece
  • B23K26/032—Observing, e.g. monitoring, the workpiece using optical means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/20—Bonding
  • B23K26/21—Bonding by welding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/20—Bonding
  • B23K26/21—Bonding by welding
  • B23K26/24—Seam welding
  • B23K26/244—Overlap seam welding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/70—Auxiliary operations or equipment
  • B23K26/702—Auxiliary equipment
  • B23K26/705—Beam measuring device
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
  • B23K31/12—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups relating to investigating the properties, e.g. the weldability, of materials
  • B23K31/125—Weld quality monitoring
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/22—Measuring arrangements characterised by the use of optical techniques for measuring depth
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
  • G01B5/0037—Measuring of dimensions of welds
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/0209—Low-coherence interferometers
  • G01B9/02091—Tomographic interferometers, e.g. based on optical coherence

Definitions

• the invention relates to a method for monitoring a laser welding process for welding two workpieces by means of a welding laser beam, which interacts with the workpieces in an interaction area to form a weld seam.
• the invention further relates to a monitoring device for monitoring a laser welding process for welding two workpieces by means of a welding laser beam, which interacts with the workpieces in an interaction area to form a weld seam.
• the invention further relates to a laser welding device for carrying out a laser welding process for welding two workpieces by means of a welding laser beam which interacts with the workpieces in an interaction area to form a weld seam.
• DE 10 2019 006 282 A1 discloses a method for process evaluation during laser beam welding of an upper joining partner with at least one lower joining partner, wherein optical coherence tomography is used to evaluate height information in a keyhole formed by laser beam welding and/or in an area surrounding the keyhole and wherein Height information signals of the optical coherence tomography are evaluated, which are assigned to a top side of the at least one lower joining partner.
• EP 0 573 474 B1 discloses a method for processing workpieces with laser radiation, in which the processing process, in particular the welding depth or the degree of penetration, is monitored by detecting optical and/or acoustic signals originating from a non-shielding, laser-induced plasma or vapor are subjected to a frequency analysis, the result of which is used to calculate a predetermined function Determination of an evaluation variable is applied. The mean amplitudes of two different frequency bands of the frequencies analyzed are used with the predetermined arithmetic function to determine the evaluation variable.
• a processing method for a workpiece is known from US 2020/0198050 A1, wherein a process beam is directed onto the workpiece for material processing and the material processing is monitored by means of an imaging beam directed onto the workpiece.
• the invention is based on the object of providing a method for monitoring a laser welding process, as mentioned at the outset, by means of which penetration welds can be detected with increased reliability.
• this object is achieved according to the invention in that, in order to monitor the laser welding process during the laser welding process, a measuring beam from an optical coherence tomograph is directed onto the interaction area to record measured values, with the measuring beam covering the workpieces in the interaction area at least if the workpieces are welded through partially penetrates and the measuring beam penetrating the workpieces strikes a reference element at a distance from the workpieces, a first measured value range is defined, which is associated with a detection of a material of the workpieces by the measuring beam in the interaction area, a second measured value range is defined, which is associated with a detection of the reference element is assigned by the measuring beam, and measured values recorded during the laser welding process are evaluated, with a ratio of a number of values lying in the first measured value range measured values and measured values lying in the second measured value range is formed and/or wherein a respective variance of measured values lying in the first measured value range and measured values lying in the second measured value range is determined.
• a vapor capillary is formed on the workpieces in the interaction area by means of the welding laser beam. From a technical point of view, the workpieces can be welded through both with the vapor capillary open and with it closed.
• penetration welding is to be understood as meaning penetration welding of the workpieces with the steam capillary open.
• this is to be understood as meaning a penetration weld which was formed or is being formed when the vapor capillary is open.
• penetration welding of the workpieces can be detected when the steam capillary is open.
• an opening state of the vapor capillary during the formation of the weld seam can be detected and/or evaluated.
• An open vapor capillary means that the vapor capillary extends through the workpieces in such a way that the measuring beam can penetrate a combination of the workpieces to be welded, i.e. that it enters the vapor capillary in particular on a first side of the combination and on one to the first Side spaced second side of the combination of the vapor capillary at least partially emerges again.
• the reference element is used to generate clearly assignable measured values when the weld seam is formed. Based on these measured values, it can therefore be reliably determined whether there are penetration welds at the weld seam.
• a spatial density of penetration welds on the weld seam formed can also be reliably determined.
• this density of penetration welds on the weld seam for example, its fluid tightness can be evaluated, with a higher number and/or higher density of penetration welds indicating greater fluid tightness.
• the fluid-tightness of welded joints can be relevant, for example, in the manufacture of fuel cells.
• the method according to the invention is suitable for detecting penetration welds in the laser welding process and in particular for determining a spatial number and/or density of penetration welds on a formed weld seam.
• the reference element is in particular an element that is independent of the workpieces and in particular independent of an arrangement and/or design of the workpieces.
• the reference element is not part of the workpiece and/or is not connected to the workpiece and/or is not arranged on the workpiece.
• the reference element is preferably arranged and/or formed on a holding device on which the workpieces are arranged for carrying out the laser welding process.
• the interaction area is an area in which the welding laser beam strikes a material of the workpieces when the laser welding process is carried out, and/or in which an interaction of the welding laser beam with a material of the workpieces takes place, with the material being heated in particular by the laser beam and /or is melted.
• the workpieces consist of a material that is opaque and/or non-transparent for a wavelength of the welding laser beam.
• the welding laser beam is absorbed by the workpieces in the interaction area.
• At least partial penetration of the workpieces by the measuring beam is to be understood in particular as meaning that the measuring beam is at least partially transmitted through a combination of the workpieces to be welded.
• the measured values recorded by means of the measuring beam are recorded and/or evaluated during the laser welding process.
• the measured values recorded during the laser welding process can be evaluated at a later point in time, for example after the laser welding process has ended.
• the weld seam can be monitored with a high spatial resolution and, in particular, can be monitored for penetration welds.
• the measuring beam of the optical coherence tomograph is used to record measured values at a spatial distance of at most 10.0 ⁇ m, preferably at most 5.0 ⁇ m and particularly preferably at most 3.0 ⁇ m during the laser welding process.
• the spatial distance is at least 1.0 pm.
• a spatial density of penetration welds of the weld seam formed and/or a fluid tightness of the weld seam formed and/or an open state of a Laser welding process trained vapor capillary is rated or can be rated.
• the spatial number and/or density of penetration welds can thus be assessed particularly reliably.
• a fluid-tightness of the weld seam can be assessed on the basis of the number or density of penetration welds at the weld seam.
• based on the ratio whether the vapor capillary is opened or not when the weld is formed, and more specifically, how often the vapor capillary is opened when the weld is formed, can be evaluated based on the ratio.
• Sufficient fluid tightness can be provided, for example, when at least 10% and in particular at least 50% and in particular at least 90% of the recorded measured values are in the second measured value range.
• a spatial density of penetration welds of the weld seam formed and/or a fluid-tightness of the weld seam formed and/or an open state a vapor capillary formed during the laser welding process is evaluated or can be evaluated.
• the variance it is possible to evaluate whether or not the vapor capillary is open when the weld seam is formed and, in particular, how often the vapor capillary is open when the weld seam is formed.
• a variance of the recorded measured values which is assigned to a detection of the reference element by the measuring beam, is greater than a variance of the recorded measured values, which is assigned to a detection of the material of the workpiece by the measuring beam in the interaction area.
• Adequate fluid tightness can be provided, for example, when the variance of the measured values in the second measured value range is smaller than the variance of the measured values in the first measured value range.
• the measured values used for the evaluation are recorded in a defined time interval, with the time interval being at least 1 ms and/or at most 50 ms. This results in the weld seam being monitored along a specific route.
• the measuring beam is oriented parallel and/or coaxially to the welding laser beam.
• the measuring beam can be directed onto the interaction area in a technically simple manner. one at that The measuring beam reflected by the reference element can thus be detected in a technically simple manner during the welding process.
• the measuring beam and the welding laser beam are directed onto the workpieces from the same direction and/or impinge on the workpieces from the same direction.
• the measuring beam and the welding laser beam impinge on a first side of a combination of the workpieces to be welded.
• the measuring beam exits from a second side of the combination of workpieces to be welded if the workpieces are welded through, the second side being spaced apart from the first side in a beam propagation direction of the welding laser beam and/or the measuring beam .
• the reference element is spaced apart from the workpieces in a beam propagation direction of the welding laser beam and/or the measuring beam and in particular is spaced apart from the second side of the combination of workpieces to be welded.
• the measuring beam penetrating the workpieces in the case of penetration welding is reflected on the reference element and a measuring beam reflected on the reference element is detected by means of the optical coherence tomograph.
• a measuring beam reflected at the reference element can thus be detected in a technically simple manner during the welding process.
• the reflected measuring beam is directed in the opposite direction to the welding laser beam and/or if the reflected measuring beam penetrates the interaction area before it is detected by the optical coherence tomograph.
• the measuring beam is reflected in the interaction area on a material of at least one of the workpieces and a measuring beam reflected on the material is detected by means of the optical coherence tomograph .
• the measuring beam is not reflected at the reference element if there is no penetration welding.
• measured values are then recorded in the first measured value range.
• the laser welding process is a deep welding process and/or that a vapor capillary is formed on the workpieces in the interaction area during the laser welding process by means of the welding laser beam.
• the workpieces are welded by means of the welding laser beam as an overlap joint and/or parallel joint.
• the measuring beam penetrates the workpiece at least partially through the vapor capillary.
• measured values are then detected in the second measured value range.
• the measuring beam cannot penetrate the workpieces on the vapor capillary.
• measured values are then detected in the first measured value range.
• a feed rate between the welding laser beam and the workpieces is at least 0.5 m/s and/or at most 1.5 m/s.
• a monitoring device comprising an optical coherence tomograph for providing a measuring beam for acquiring measured values during the laser welding process, the measuring beam being set up such that it is directed onto the interaction area during the laser welding process and if the workpieces are welded through, it at least partially penetrates the workpieces in the interaction area, a reference element which is at a distance from the workpieces and on which the measuring beam penetrating the workpieces strikes, and an evaluation device for evaluating measured values recorded during the laser welding process, with the evaluation device Ratio of a number of measured values in a first measured value range and measured values in a second measured value range is formed and/or a respective variance of measured values in a first measured value range and in a second measured value range is formed by means of the evaluation device, with the first measured value range is assigned to a detection of a material of the workpieces by the measuring beam in the interaction area and the second measured value area is assigned to a detection of the reference element by the measuring beam is arranged.
• the monitoring device according to the invention has in particular one or more features and/or advantages of the method according to the invention.
• the method according to the invention can be carried out using the device according to the invention.
• the device according to the invention carries out the method according to the invention.
• a laser welding device mentioned at the outset comprising a monitoring device according to the invention.
• the laser welding device comprises a holding device on which the workpieces can be arranged or are arranged for carrying out the laser welding process, the reference element being arranged and/or formed on the holding device.
• the reference element can thus be integrated into the laser welding device in a technically simple manner and can be arranged at a defined distance from the workpieces to be welded.
• the holding device is or includes a clamping device on which the workpieces can be clamped and arranged.
• the terms “at least approximately” or “approximately” generally mean a deviation of at most 10%. Unless otherwise stated, the terms “at least approximately” or “approximately” mean in particular that an actual value and/or distance and/or angle deviates by no more than 10% from an ideal value and/or distance and/or angle .
• Fig. 1 is a schematic representation of an embodiment of a
• Laser welding device for carrying out a laser welding process, which has a monitoring device for monitoring the laser welding process;
• FIG. 2 shows an example of measured values recorded by means of the monitoring device during a laser welding process.
• FIG. 1 An exemplary embodiment of a laser welding device is shown schematically in FIG. 1 and is denoted by 100 there.
• a laser welding process in particular a deep welding process, can be carried out using the laser welding device 100 to produce a welded connection between at least two workpieces.
• a welded connection is produced between a first workpiece 102 and a second workpiece 104 by means of the laser welding device 100 .
• the workpieces 102, 104 to be welded are in particular plate-shaped and/or panel-shaped.
• the workpieces 102, 104 consist of a metallic material and/or are designed as sheet metal.
• the workpieces 102, 104 to be welded preferably each have a thickness D of approximately 75 ⁇ m.
• the laser welding device 100 includes a laser source 106, by means of which a welding laser beam 108 is provided to form the welded connection.
• the welding laser beam 108 has a wavelength of at least 500 nm and/or at most 1100 nm, for example.
• the welding laser beam preferably has a wavelength of at least 515 nm and/or at most 535 nm or at least 1030 nm and/or at most 1070 nm.
• the workpieces 102, 104 consist of a material that is opaque and/or impermeable to the wavelength of the welding laser beam 108.
• the welding laser beam 108 is directed onto the first workpiece 102 in the example shown and then moved at a feed rate relative to the first workpiece 102 and the second workpiece 104. As a result, a weld seam is formed between the first workpiece 102 and the second workpiece 104 along a trajectory of the welding laser beam 108 .
• the feed rate is preferably approx. 1.0 m/s.
• the second workpiece 104 is positioned behind the first workpiece 102 and/or below the first workpiece 102 with respect to a beam propagation direction 110 of the welding laser beam 108 .
• the workpieces 102, 104 are welded by means of the welding laser beam 108 as an overlap joint and/or parallel joint.
• the first workpiece 102 and the second workpiece 104 each have outer sides 112 which are perpendicular or approximately perpendicular to a Thickness direction of the respective thickness D of the first workpiece 102 and the second workpiece 104 are oriented.
• first workpiece 102 and the second workpiece 104 are in particular flat against one another, with opposite and/or abutting outer sides 112 of the first workpiece 102 and the second workpiece 104 being oriented parallel or approximately parallel to one another.
• the welding laser beam 108 is preferably oriented perpendicularly or approximately perpendicularly to an outer side 112a of the first workpiece 102, onto which the welding laser beam 108 is directed.
• the welding laser beam 108 is oriented parallel or approximately parallel to the thickness direction of the first workpiece 102 and/or the second workpiece 104 .
• the welding laser beam 108 interacts with the formation of the weld seam with the material of the first workpiece 102 and in particular also the second workpiece 104 in an interaction region 114.
• the welding laser beam 108 penetrates the outside 112a of the first workpiece 102 in this interaction region 114 into the first Workpiece 102 and in particular also into the second workpiece 104 .
• the welding laser beam 108 is absorbed in particular by the material of the first workpiece 102 or of the second workpiece 104 .
• a penetration weld is formed in particular when the vapor capillary 116 formed during the laser welding process completely penetrates a combination 118 of the first workpiece 102 and second workpiece 104 to be welded. In this case, we are dealing with a penetration weld with an open vapor capillary 116.
• weld penetration refers to a weld penetration that was formed or is being formed when the vapor capillary 116 is open.
• the vapor capillary 116 extends in the case of a mentioned full penetration from a first side 120 of the combination 118 to be welded to a second side 122 of the combination 118, the second side 122 being spaced apart from the first side 120 in the beam propagation direction 110 of the welding laser beam 108.
• the welding laser beam 108 is directed onto the first side 120 to form the welded joint, the welding laser beam 108 being coupled into the combination 118 in particular through this first side 120 .
• the first side 120 with respect to the beam propagation direction 110 is an upper side of the combination 118 and the second side 122 is an underside of the combination 118.
• Laser welding device 100 includes a monitoring device 124 for monitoring the laser welding process.
• monitoring device 124 can be used to monitor the weld seam formed during the laser welding process for a sufficient number and/or density of penetration welds.
• the number or the density of penetration welds on the weld seam formed can be used in particular as a criterion for evaluating a Fluid tightness of the weld serve.
• the weld seam is monitored for the presence of penetration welds during or after its formation by means of the monitoring device 124 .
• the monitoring device 124 includes an optical coherence tomograph 126, by means of which a measuring beam 128 is provided for recording measured values during the formation of the weld seam.
• a wavelength of the measuring beam 128 is at least 800 nm and/or at most 1600 nm.
• distance information of a distance A with respect to a zero point position 129 can be detected by means of the measuring beam 128, wherein this distance information can preferably be detected one-dimensionally and/or with respect to a spatial direction.
• the distance information can be detected with regard to the beam propagation direction 110 and/or with regard to the thickness direction of the respective thickness D of the workpieces 102, 104.
• the measuring beam 128 is directed onto an object and reflected on it.
• the reflected measurement beam is then detected by a detector element 130 of the optical coherence tomograph 126 .
• Monitoring device 124 includes, in particular, an evaluation device 132 for evaluating and/or temporarily storing measured values recorded by means of optical coherence tomograph 126.
• the measuring beam 128 is directed onto the interaction region 114, with the measuring beam 128 preferably being oriented parallel and/or coaxially to the welding laser beam 108.
• the measuring beam 128 is projected onto the first side 120 of the Combination 118 directed and/or coupled into combination 118 through first side 120 .
• a beam propagation direction of measuring beam 128 corresponds at least approximately to beam propagation direction 110 of welding laser beam 108.
• the vapor capillary 116 formed in the interaction region 114 during the laser welding process is open at least towards the first side 120 of the combination 118 so that the measuring beam 128 can penetrate into it.
• the vapor capillary 116 is closed on the second side 122 .
• the measuring beam 128 is consequently reflected in the interaction region 114 on a material of the first workpiece 102 and/or the second workpiece 104 which is arranged in particular on a boundary 131 of the vapor capillary 116 .
• this material can be in a solid or liquid state.
• measurement beam 128 is used to generate measured values, in particular, which can be assigned to a position of the material of workpieces 102 , 104 at boundary 131 of vapor capillary 116 in interaction region 114 .
• the material on which the measurement beam 128 is reflected if no vapor capillary 116 is open is positioned in particular at a lowest point 133 (indicated in FIG. 1) of the vapor capillary 116 that is at a distance from the first side 120 in the beam propagation direction 110 .
• the measured values recorded by means of the measuring beam 128 are then assigned, for example, to a welding depth of the laser welding process.
• the vapor capillary 116 is open towards the second side 122 .
• the vapor capillary 116 then extends in particular continuously between the first side 120 and the second side 122 of the combination 118 of workpieces 102, 104 to be welded.
• measuring beam 128 is transmitted at least partially and/or at least in sections through combination 118 of workpieces 102, 104.
• the measuring beam 128 penetrates, for example, the vapor capillary 116 and/or the workpieces 102, 104 in the interaction area 114, so that it exits at least partially on the second side 122.
• the transmitted measuring beam 128 then strikes a reference element 134, which is assigned to the monitoring device 124 and/or is part of the monitoring device 124, and is reflected on it.
• This reference element 134 is arranged at a reference position 136 and/or at a reference distance.
• the reference position 136 is at a distance from the zero point position 129 by the reference distance.
• a reflected measuring beam 135 is formed by reflection of the measuring beam 128 on the reference element 134 , which is preferably transmitted back through the vapor capillary 116 and is then detected by the detector element 130 .
• measured values are consequently generated by means of the measuring beam 128 which are to be assigned to the reference position 136 .
• the wavelength of the measuring beam 128 is selected in particular such that the measuring beam is transmitted through the vapor capillary 116 and is reflected by the material of the workpieces 102, 104, so that in particular measurement values are recorded in the case of penetration welding on the reference element and in the case of no penetration welding and/or there is no penetration welding with the vapor capillary 116 open on the material of the workpieces 102, 104.
• the laser welding device 100 includes in particular a holding device 137 on which the first workpiece 102 and the second workpiece 104 are arranged for carrying out the laser welding process.
• a holding device 137 comprises a clamping device for clamping the first workpiece 102 and the second workpiece 104.
• the first workpiece 102 and the second workpiece 104 are arranged clamped by means of the clamping device and/or arranged clamped against one another.
• the reference element 134 is in particular part of the laser welding device 100 and/or the monitoring device 124. In particular, the reference element 134 is arranged and/or formed on the holding device 137.
• FIG. 2 An example of measured values recorded by means of the measuring beam 128 during the formation of the weld seam as a function of time is shown in FIG. 2 .
• the measured values recorded during the implementation of the laser welding process are essentially (apart from outliers) in a first measured value range 138, which can be assigned to a detection of the material of the workpieces 102, 104 in the interaction area 114, and in a second measured value range 140, which can be assigned to a detection of the Reference element 134 is assigned.
• the first measured value range 138 is defined in such a way that those measured values fall within it that are to be assigned to the detection of the material of the workpieces 102 , 104 in the interaction region 114 .
• the first measured value range 138 includes those measured values which are to be assigned to a distance range 142 in which the workpieces 102, 104 extend from the zero point position 129 with respect to the beam propagation direction 110.
• the second range of measured values 140 is defined in such a way that those measured values which are to be assigned to the detection of the reference element 134 fall within it.
• the second range of measured values includes those measured values which are to be assigned to a distance between the reference position 136 and the zero point position 129 .
• the laser welding device 100 with the monitoring device 124 works as follows:
• the workpieces 102, 104 to be welded are arranged on the holding device 137.
• the welding laser beam 108 generated by the laser source 106 is directed onto the first workpiece 102 and moved relative to it in order to produce a weld seam.
• the welding laser beam 108 interacts with the material of the workpieces 102, 104 in the interaction area 114, with a vapor capillary 116 being formed.
• the measuring beam 128 is directed onto the interaction area 114 while the weld seam is being produced.
• the measuring beam 128 is reflected there on the material of the workpieces 102, 104, so that measured values are recorded which lie within the first measured value range 138. In particular, no measured values that are in the second measured value range 140 are then recorded.
• measuring beam 128 is at least partially transmitted through the material of workpieces 102, 104 at least at this point, so that measured values that lie within second measured value range 140 are recorded. In the event of partial transmission of measuring beam 128, it may happen that two measured values are generated at this point, with one being assigned to first measured value range 138 and one to second measured value range 140.
• the measured values recorded during the formation of the weld seam are temporarily stored and/or evaluated by means of evaluation device 132, for example.
• evaluation device 132 In order to evaluate the weld seam with regard to a spatial density of penetration welds, in particular measured values are considered which were recorded within a specific time interval and/or which are assigned to a specific spatial section of the weld seam formed.
• a ratio of a respective number of measured values that lie in the first measured value range 138 and in the second measured value range 140 with respect to a specific time interval and/or spatial section is determined.
• a weld seam with sufficient tightness and/or with a sufficient density of penetration welds is present in particular when at least one defined proportion, for example a proportion of at least 50%, of the measured values under consideration are in the second measured value range 140.
• those measured values which can be assigned to a reflection of the measuring beam 128 on the material of the first workpiece 102 and/or the second workpiece 104 in the interaction region 114 typically have a greater variance and/or scatter than those measured values which are to be assigned to a reflection of the measuring beam 128 at the reference element 134 .
• a spatial position of the boundary 131 of the vapor capillary 116, at which solid and/or liquid material of the workpieces 102, 104 is detected by means of the measuring beam 128, varies in particular.
• measurement beam 128 is always reflected at reference element 134 at reference position 136 of reference element 134.
• a weld seam with sufficient tightness and/or with a sufficient density of penetration welds is present in particular when the variance of the measured values under consideration in the first measured value range 140 is greater than the variance of the measured values in the second measured value range 142.

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• 2021
  • 2021-07-07 DE DE102021117524.0A patent/DE102021117524A1/de active Pending
• 2022
  • 2022-06-21 WO PCT/EP2022/066793 patent/WO2023280559A1/de active Application Filing
  • 2022-06-21 EP EP22735850.4A patent/EP4366906A1/de active Pending
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