Laser processing system and method for laser processing

Abstract

The invention relates to a laser machining system (100), comprising: a first deflection optics (110) which is arranged for deflecting a machining laser beam (10) in two spatial directions (x, y); a second deflection optics (120) which is arranged for deflecting a measurement beam independently of the machining laser beam (10) (15) in two spatial directions (x, y); a coupling-in device (130) which is arranged in the beam path of the machining laser beam (10) and is arranged for coupling the measurement beam (15) into the beam path of the machining laser beam (10).

Description

[0001] This application is a divisional application of the invention patent application with application number 201880073395.4, application date October 17, 2018, and invention title "Laser Processing System and Method for Laser Processing". Technical Field

[0002] This invention relates to a laser processing system, and more particularly to a system for laser processing of materials using a laser beam, such as a laser processing head for laser welding or laser cutting, and to a method for laser processing. The invention particularly relates to weld measurement and weld tracking, for example, using optical coherence tomography. Background Technology

[0003] In material processing using laser beams, such as laser welding or laser cutting, a laser beam emitted from a laser source, such as the end of a laser transmission fiber, is focused onto the workpiece to be processed by beam guiding and focusing optics. By standard, a laser processing head with collimating and focusing optics is used, in which the laser is delivered via an optical fiber (also called a laser source). The laser passes through multiple optical elements (e.g., lenses) within the apparatus used for laser-based material processing (e.g., in a laser processing head).

[0004] In many welding processes, it is necessary to precisely align the incident point of the processing laser beam with the weld seam direction of the two mating components for a stable process. To achieve this, the weld seam position can be continuously determined during the welding process, allowing the laser to always track that position using a scanning device. However, known technical solutions for determining the weld seam position during welding typically rely on the projection of the laser line onto the component perpendicular to the weld seam extension and the evaluation of that laser line using a camera.

[0005] The drawback of this optical sectioning method is that the orientation of the laser line relative to the processing optics is fixedly predetermined, and the method therefore only works for welding directions that are fixedly predetermined for a given process. In other words, determining the weld orientation is not direction-independent. A possible solution in the optical cutting method is to rotate the entire optics to track the weld orientation; however, this can only be achieved to a limited extent, even in robot-guided processes.

[0006] DE 10 2009 057 209 B4 describes an apparatus for material processing using a laser, the apparatus having a scanner optics movable relative to the workpiece to be processed by guiding the machine. The apparatus includes a projector for projecting measurement light onto the workpiece in the form of a measurement structure, and an image sensor sensitive within the wavelength range of the measurement light emitted by the projector. The projector and image sensor are connected to the scanner optics and therefore move with the scanner optics during operation of the apparatus. Therefore, orientation-independent measurements cannot be performed. Summary of the Invention

[0007] The objective of this invention is to provide a laser processing system, particularly a system for processing materials using a laser beam, such as a laser processing head or a system for laser welding, and a method for laser processing that allows for precise weld seam tracking regardless of the processing direction.

[0008] This task is addressed through the subject matter of the independent claims. Advantageous configurations are described in the dependent claims.

[0009] According to an embodiment of the present invention, a laser processing system is provided. The laser processing system includes: a first deflecting optics configured to deflect a processing laser beam in two spatial directions; a second deflecting optics configured to deflect a measuring beam in the two spatial directions independently of the processing laser beam; and a coupling device arranged in the beam path of the processing laser beam and configured to couple the measuring beam into the beam path of the processing laser beam.

[0010] Preferably, the first deflecting optics comprises two independent first deflecting mirrors. Typically, the first deflecting optics are configured to process two-dimensional oscillations of the laser beam, such as movement along a line, preferably along a line perpendicular to the weld direction, circular movement, or "8"-shaped movement.

[0011] Preferably, the second deflecting optics comprises two independent second deflecting mirrors. Typically, the second deflecting optics are configured to measure the linear and / or circular motion of the beam.

[0012] Preferably, the second deflecting optics is configured to deflect the measuring beam onto at least one workpiece, and particularly onto the junction area of ​​two workpieces, regardless of the feed direction of the processing laser beam.

[0013] Preferably, the coupling device is a beam splitter. Typically, the coupling device is configured to substantially coaxially superimpose the processing laser beam and the measurement beam.

[0014] Preferably, the laser processing system includes a control device configured to control a first deflection device, such that the processing laser beam tracks the weld seam on the workpiece.

[0015] Preferably, the laser processing system includes an evaluation unit configured to measure the weld orientation, such as edge orientation and / or weld seam orientation, on the workpiece using a measuring beam. The evaluation unit is capable of measuring the edge orientation of the joint before processing the laser beam and / or the weld seam orientation after processing the laser beam. Specifically, the evaluation unit can be configured to determine the weld orientation using optical short coherence tomography.

[0016] According to another aspect of the present invention, a laser processing method is provided. The method includes: deflecting a processing laser beam in two spatial directions such that the processing laser beam performs two-dimensional motion on at least one workpiece; deflecting a measuring beam in two spatial directions independently of the processing laser beam; and coupling the measuring beam into the beam path of the processing laser beam.

[0017] Preferably, the laser beam is processed to perform oscillating motion (2D oscillation process), such as linear motion, circular motion, or "8"-shaped motion.

[0018] Preferably, the measuring beam performs a linear or circular motion along the weld direction, for example, along the edge direction and / or the weld direction.

[0019] Preferably, the method further includes: determining the weld orientation, such as the edge orientation of the two workpieces to be joined, using a measuring beam; and processing a laser beam to track the weld orientation based on the determined weld orientation. Preferably, optical short coherence tomography is used to determine the weld orientation.

[0020] Preferred and optional embodiments and special aspects of the invention are derived from the dependent claims, drawings and this specification.

[0021] According to the embodiments described herein, during laser processing, the weld orientation on a component can be measured independently of direction, and the laser beam can be precisely positioned at the desired weld location. The optical measurement beam is guided by its own actuation mechanism and coupled into the beam path of the processing laser via a coupling device following the actuation mechanism of the processing laser, and superimposed on the processing laser. With this arrangement, the component geometry can be measured approximately coaxially around the current position of the processing laser beam, independent of the movement of the processing laser beam during the processing.

[0022] Another advantage of the embodiment described herein for obtaining weld seams in optical sectioning over line projection is the achievable resolution. Particularly when using optical coherence tomography (OCT), the embodiment described herein provides accuracy for the measured interval values ​​of approximately 1 μm. This accuracy allows for the measurement of vertical structures on a component, such as the edge height of a fillet weld. In contrast, the resolution achievable in optical sectioning is primarily limited by the quality of line projection. Typical line widths range from approximately 20 to 100 μm. Consequently, the resolution for structure identification is approximately an order of magnitude lower by evaluating lines in the camera image. Attached Figure Description

[0023] Embodiments of the present invention are shown in the accompanying drawings and further described below. They show: Figure 1 A schematic diagram of a laser processing system according to an embodiment of the present invention. Figure 2 A schematic orientation of the processing laser beam and the measuring beam according to an embodiment of the present invention. Figure 3 Measurement data from line scans of optical coherence tomography, and Figure 4 A flowchart of a method for laser processing according to an embodiment of the present invention.

[0024] Unless otherwise specified, the same reference numerals shall be used for the same and identical elements. Detailed Implementation

[0025] Figure 1 A laser processing system 100 according to an embodiment of the present invention is shown, particularly for material processing using a laser beam, such as systems for laser welding. Figure 1 The left side schematically shows the beam path of the processing laser, and the right side shows the beam path of the optical sensor system. According to an embodiment, the optical sensor system can be a coherent interferometer.

[0026] The laser processing system 100 includes a first deflecting optics 110, a second deflecting optics 120, and a coupling device 130. The first deflecting optics is configured to deflect a processing laser beam 10 in two spatial directions x and y. The second deflecting optics is configured to deflect a measuring beam 15 (sensor beam) in the two spatial directions x and y independently of the processing laser beam 10. The coupling device is arranged in the beam path of the processing laser beam 10 and is configured to couple the measuring beam 15 into the beam path of the processing laser beam 10. Preferably, the second deflecting optics 120 is configured to deflect the measuring beam 15 independently of the feed direction or processing direction 20 of the processing laser beam 10 onto at least one workpiece 1, and particularly onto the mating region of two workpieces.

[0027] According to an embodiment of the invention, weld seam finding is performed, for example, during the welding of components, to precisely position the processing laser beam 10 relative to the weld seam. Here, the measuring beam 15, deflected in two directions by the second deflecting optics 120, enables the determination of the weld seam position independent of the current feed direction of a given processing procedure, such as a welding process. Through its own actuation mechanism within the beam path of the processing laser beam, laser beam oscillation in two directions (“2D oscillation process”) can be achieved, which can be performed independently of the movement of the measuring beam 15 within the measuring beam path.

[0028] According to an embodiment, the laser processing system 100 (also referred to as a "laser processing head") includes: a laser source (not shown), such as an optical fiber, for providing a processing laser beam; a collimating optics 140 configured to collimate the processing laser beam 10; and a focusing optics 150 configured to focus the processing laser beam 10 onto at least one workpiece 1 or component.

[0029] According to an embodiment, the laser processing system 100 or its components (e.g., a welding head) can move along a processing direction 20. The processing direction 20 can be the welding direction and / or movement direction of the laser processing system 100, such as the welding head, relative to the workpiece 1. The processing direction 20 can particularly be a horizontal direction. The processing direction 20 can also be referred to as the "feed direction" or "process direction".

[0030] In some embodiments, the laser processing system 100 is configured for welding. The laser processing system 100 is capable of forming a weld seam on a single workpiece, or of welding two workpieces (“joints”) to each other, such as... Figure 1As shown in the example, the laser processing system 100 can measure the weld orientation on the workpiece 1, such as the edge orientation 2 and / or the weld orientation 3, using the measuring beam 15. In particular, it can measure the edge orientation 2 of the joint before processing the laser beam 10 and / or the weld orientation 3 after processing the laser beam 10. In other words, it can measure or determine the weld orientation in the pre-processing orientation (Vorlauf) and / or post-processing orientation (Nachlauf) of processing the laser beam 10 using the measuring beam 15.

[0031] Preferably, the laser processing system 100 includes an evaluation unit configured to measure the weld orientation on the workpiece, such as edge orientation 2 and / or weld orientation 3, using a measuring beam 15. The evaluation unit is capable of measuring or determining the edge orientation of the joint with respect to the processing direction 20 before the processing laser beam 10 and / or the weld orientation after the processing laser beam 10. The evaluation unit can be included, for example, in an optical coherence tomography apparatus, and the reflected measuring beam is evaluated to determine the weld orientation.

[0032] Typically, the laser processing system 100 includes a control device configured to control a first deflection device 110 such that the processing laser beam 10 tracks the weld seam orientation on the workpiece. The control device is connectable to an evaluation unit and can obtain data regarding the weld seam orientation from the evaluation unit. Based on this data, the control device can control the first deflection device 110 such that the processing laser beam 10 tracks the weld seam orientation on the workpiece.

[0033] The laser processing system 100 is configured to deflect the processing laser beam 10 and the measuring beam 15 in two spatial directions, x and y. In other words, it provides two degrees of freedom for each of the two beams. The two spatial directions x and y can be directions of a Cartesian coordinate system, such as the X and Y directions. The two spatial directions can be orthogonal to each other and unfold into a plane. The coordinate system can be defined relative to the workpiece and, in particular, can be fixed or stationary relative to the workpiece. Alternatively, the coordinate system can be defined relative to a portion of the laser processing system 100 that moves along the processing direction 20, such as a welding head, and, in particular, can be fixed or stationary relative to the welding head.

[0034] Preferably, the first deflecting optics 110 includes at least one first deflecting mirror, and more particularly includes two independent first deflecting mirrors. The independent first deflecting mirrors are supported in a manner rotatable about respective axes of rotation, so as to deflect the processing laser beam 10 in two spatial directions. These axes of rotation are perpendicular to each other and provide two degrees of freedom by which the processing laser beam 10 can be deflected two-dimensionally.

[0035] The laser optics therefore include a actuator, such as a scanning optics device, which consists of two independent scanning mirrors through which the processing laser beam 10 can be deflected on the component in two directions. This enables precise positioning of the processing laser beam 10 on the component in two spatial directions, so as to track the weld direction during the welding process, such as in the case of fillet welds.

[0036] According to an embodiment, the first deflecting optics 110 is configured for two-dimensional oscillation of the processing laser beam 100. The processing laser beam 10 is particularly capable of oscillating in two directions during this process to specifically increase the influence range of the processing laser beam 10 on the component and thereby achieve a more stable weld connection. During this 2D oscillation, the processing laser beam 10 can be offset on a defined two-dimensional scan pattern on the component, the two-dimensional scan pattern being, for example, composed of lines, circles (…). Figure 2 (a) or by the shape of "8" ( Figure 2 (b) and (c) constitute the oscillation. Typically, the oscillation occurs at a frequency in the range of about 50 to 1000 Hz, and preferably at a frequency in the range of about 100 to 800 Hz.

[0037] By manipulating the high-frequency motion of the laser beam 10 on a two-dimensional pattern, process parameters such as laser velocity, weld penetration depth, and weld width can be selectively adjusted regarding the amplitude and frequency of the motion. Therefore, for example, for a given weld geometry, matching the amplitude of the laser oscillation can increase the laser's influence range, thereby achieving better gap bridging. Furthermore, for the hybrid joining of two different materials (such as copper and aluminum), the mixing ratio in the melt can be selectively adjusted by choosing the amplitude and frequency.

[0038] In some embodiments, the second deflecting optics 120 includes at least one second deflecting mirror, and more particularly, two independent second deflecting mirrors. The independent second deflecting mirrors are supported in a manner rotatable about a respective axis of rotation for deflecting the measurement beam 15 in two spatial directions. The axes of rotation are perpendicular to each other and provide two degrees of freedom by which the measurement beam 15 can be deflected two-dimensionally. Typically, the second deflecting optics 120 is configured to measure the linear and / or circular motion of the beam, as shown in reference [reference needed]. Figure 2 As explained in detail.

[0039] According to an embodiment of the invention, the coupling device 130 is a beam splitter. Typically, the coupling device 130 is configured to superimpose the processing laser beam 10 and the measurement beam 15 substantially coaxially. The coupling device 130 can be located upstream of the focusing optics 150 such that both the processing laser beam 10 and the measurement beam 15 pass through the focusing optics 150.

[0040] According to the embodiment described herein, the measuring light of the sensor system is coupled into the beam path of the processing laser, wherein the position of the measuring beam 15 on the component can be moved by its own actuation mechanism or scanner unit. The sensor principle for distance measurement can be, for example, based on optical short coherence interferometry (OCT). The coupling of the measuring beam 15 can be achieved by a beam splitter located in the beam path of the thermal laser beam after the actuation mechanism of the processing laser. With this arrangement, an approximately coaxial superposition of the measuring beam 15 and the processing laser beam 10 is achieved, wherein each of the two beams can be deflected independently of each other in two directions by its own actuation mechanism. A practical advantage is that the geometry of the component around the current position of the processing laser beam 10 can be measured using the measuring beam 15, independent of the movement of the processing laser beam 10 during the process.

[0041] Therefore, the measuring beam 15 can, for example, first move repeatedly along a line preceding the laser position in the welding direction to detect and adjust the precise position of the weld. Then, the measuring beam 15 can, for example, move repeatedly along a line following the laser position in the welding direction to measure the weld geometry (see...). Figure 1 and Figure 2 (a) and (b)). Another feasible movement of the measuring beam 15 on the component is a repeated circular pattern movement, thereby enabling weld detection in the pre-machining path and monitoring the weld profile of the completed weld in the post-machining path (see...). Figure 2 (c)).

[0042] In addition to the precise positioning of the laser beam along the weld seam of the joint, what is also beneficial to the quality of the welding process and the stability of the joint is that the laser beam oscillates around the previously determined weld seam position, a process known as oscillation. For example, during the high-frequency movement of the laser around the center point of this oscillation, only that center point can coincide with the weld seam position. Depending on the weld geometry and the material of the component, this movement can be performed on a linear track perpendicular to the weld seam, or it can be performed on a pre-given two-dimensional pattern (e.g., a circle or an "8" shape). Therefore, using the embodiment described here, the high-frequency laser beam oscillation can be performed along a two-dimensional scanning pattern, its position tracking the weld seam's direction with great precision, regardless of the weld seam's orientation on the component.

[0043] Figure 2A schematic orientation of the processing laser beam 10 and the measuring beam 15 according to an embodiment of the present invention is shown. In particular, different scan patterns of the measuring beam 15, used for weld seam finding and weld quality monitoring, are shown while the processing laser performs high-frequency laser oscillation (2D oscillation process). Arrows indicate the feed direction of the welding process along the curved weld seam orientation 11. Three sequentially closed scan patterns along the weld seam are shown for both the measuring laser and the processing laser.

[0044] By rapidly scanning the surface using the measuring beam 15, a height profile can be established along the scanning pattern. The weld position is obtained by scanning a line before the laser beam, and the height profile of the completed weld bead is obtained by scanning a line after the laser beam. Simultaneously, the processing laser beam 10 can perform a high-frequency two-dimensional oscillation process along, for example, a line perpendicular to the weld direction. Figure 2 (a)). Another feasibility for processing the scanning pattern of laser 10 is a circular pattern or an "8" shape ( Figure 2 (b) and Figure 2 (c)). An alternative to the scanning pattern of the measuring beam 15 is a circle (along with two lines in the pre-processing and post-processing directions) that includes the area for weld seam searching before laser treatment and the area for weld quality assessment after laser treatment. Figure 2 (d) Of course, the scanning pattern of the measuring beam 15 and the scanning pattern of the processing beam 10 can be arbitrarily combined with each other. In addition, other shapes other than straight lines or shapes other than circles or "8" shapes can also be used.

[0045] The advantage of a circular pattern is that the actuation mechanism used for deflecting the measuring beam 15 or machining the beam 10 must perform less abrupt braking and acceleration movements, and thus a higher repetition frequency of the pattern can be achieved. For the same reason, an "8" pattern is advantageous as a scanning pattern for machining the beam 10. The specific requirements of the process, such as weld geometry, precise weld orientation, or feed rate, determine whether a linear or circular scan is used.

[0046] Another advantage of scanning the measurement beam 15 on a circle is that the weld orientation does not need to be known during the preparation stage of actual processing. Two lines, one representing the orientation before processing and the other after processing, should always be perpendicular to the weld orientation for measurement. To this end, information about the weld orientation is transmitted to the control software of the actuator used to measure the beam, so that the lines can always be oriented perpendicular to the current weld direction during the process. In the case of circular scanning, the orientation of the scan pattern is eliminated because for any weld orientation, whether before or after the laser incident point, a defined arc segment of the circle always extends perpendicular to the weld.

[0047] Figure 3Measurement data for a line scan recorded using an optical short coherence tomography (OCT) system for fillet weld configuration is shown. This line scan consists of lines oriented before and after machining. The data shown are OCT measurements of a line scan performed by a machining optics system during the welding process of an aluminum fillet weld joint. The intervals of the OCT measurements are plotted in micrometers on the Y-axis, while the positions on the component (in arbitrary units) are plotted on the X-axis. The height and precise location of the fillet weld can be determined using the measurement data of the lines in the region before the laser (see [link to documentation]). Figure 3 (1) Measurement data of the lines in the region behind the laser can be used to monitor the profile and quality of the completed weld (see...). Figure 3 (2)).

[0048] Figure 4 A flowchart of a method for laser processing according to an embodiment of the present invention is shown. The method can include reference... Figures 1 to 3 The aspects described.

[0049] The method includes deflecting the processing laser beam in two spatial directions such that the processing laser beam performs two-dimensional motion on at least one workpiece, deflecting the measuring beam independently of the processing laser beam in two spatial directions, and coupling the measuring beam into the beam path of the processing laser beam. Preferably, the processing laser beam performs oscillating motion (“2D oscillation process”). For example... Figure 2 As shown, the measuring beam is capable of linear or circular motion along the weld orientation, such as the edge orientation and / or the weld seam orientation. Typically, the method also includes, for example, using the measuring beam in the pre-processing orientation of the processing laser beam to determine the weld orientation and the processing laser beam tracking the determined weld orientation based on the determined weld orientation.

[0050] According to the embodiment described herein, two independent deflecting optics are used to deflect the processing laser beam and the measurement beam in two dimensions, respectively. The measurement beam is coupled into the beam path of the processing laser beam and superimposed substantially coaxially with the processing laser beam to perform, for example, optical coherence tomography. Therefore, for example, direction-independent weld seam detection can be achieved during 2D oscillation. In particular, this weld seam detection can be performed independently of the processing direction of the processing laser beam.

Claims

1. A laser processing system (100), comprising: A first deflection optics (110) is configured to deflect a processing laser beam (10) in two spatial directions (x, y), wherein the first deflection optics (110) is configured to cause two-dimensional oscillation of the processing laser beam (10) around the weld seam direction in a closed scan pattern. The second deflecting optics (120) includes two independent second deflecting mirrors, which are configured to deflect the measuring beam (15) in two spatial directions (x, y) independently of the processing laser beam (10), wherein the two spatial directions (x, y) are the directions of a Cartesian coordinate system, which is stationary relative to the portion of the laser processing system (100) that moves along the processing direction (20); and A coupling device (130) is configured to couple the measuring beam (15) into the beam path of the processing laser beam (10); Its features are, The coupling device (130) is arranged in the beam path of the processing laser beam (10) after the first deflecting optics (110).

2. The laser processing system (100) according to claim 1, wherein, The first deflecting optics (110) includes two independent first deflecting mirrors.

3. The laser processing system (100) according to claim 1 or 2, wherein, The second deflecting optics (120) is configured for linear or circular motion of the measuring beam (15).

4. The laser processing system (100) according to any one of claims 1 to 3, wherein, The second deflecting optics (120) is configured to deflect the measuring beam (15) onto at least one workpiece (1) regardless of the feed direction (20) of the processing laser beam (10).

5. The laser processing system (100) according to any one of claims 1 to 4, wherein, The coupling device (130) is a beam splitter.

6. The laser processing system (100) according to any one of claims 1 to 5, wherein, The coupling device (130) is configured to coaxially superimpose the processing laser beam (10) and the measurement beam (15).

7. The laser processing system (100) according to any one of claims 1 to 6, the laser processing system further comprising an evaluation unit configured to determine the weld orientation on the workpiece (1) using the measuring beam (150).

8. The laser processing system (100) according to any one of claims 1 to 7 further includes a control device configured to control a first deflection device (110) such that the processing laser beam (10) tracks the weld seam on the workpiece (1).

9. The laser processing system (100) according to claim 8, wherein, The evaluation unit includes an optical coherent interferometer.

10. A method for laser processing, comprising: The processing laser beam (10) is deflected in two spatial directions (x, y) using a first deflection optics device (110), so that the processing laser beam (10) performs a two-dimensional motion around the weld direction in a closed scan pattern on at least one workpiece (1); The measuring beam (15) is deflected independently of the processing laser beam (10) in two spatial directions (x, y) using a second deflecting optics (120). The second deflecting optics (120) comprises two independent second deflecting mirrors, wherein the two spatial directions (x, y) are directions of a Cartesian coordinate system, the portion of the Cartesian coordinate system that moves relative to the laser processing system (100) along the processing direction (20) is stationary; and The measuring beam (15) is coupled into the beam path of the processing laser beam (10); Its features are, The measurement beam (15) is coupled in by a coupling device (130) arranged in the beam path of the processing laser beam (10) after the first deflection optics (110).

11. The method according to claim 10, wherein, The processing laser beam (10) undergoes oscillating motion.

12. The method according to claim 10 or 11, wherein, The measuring beam (15) performs a linear or circular motion.

13. The method according to any one of claims 10 to 12, further comprising: The weld orientation is determined by optical coherence tomography when using the measurement beam (15); and Based on the determined weld direction, the processing laser beam (10) tracks the weld direction.

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