Material processing using a laser beam with oscillating motion

Abstract

A system for material processing by means of a laser beam, comprising a deflection unit (40) and a swing unit (60) for deflecting the laser beam (14), wherein the swing unit is configured to superimpose a swing motion of the laser beam (14) having a swing pattern and a swing frequency on a feed motion of the laser beam (14) corresponding to a processing path by controlling the deflection unit (40), wherein the swing unit (60) is configured to control the deflection unit (40) according to a compensated swing motion in order to implement the swing motion, wherein in the compensated swing motion, a control value for the deflection of the laser beam (14) along the swing pattern is adapted according to the swing frequency, and / or a trajectory speed of the swing motion that changes along the swing pattern is adapted according to a position of the laser beam (14) in the swing pattern and the swing frequency; and a method for material processing by means of a laser beam.

Description

Technical Field

[0001] The present invention relates to a system for processing materials with the aid of a laser beam, the system comprising an offset unit for deflecting the laser beam; and a swing unit, the swing unit being configured to superimpose a swinging motion of the laser beam corresponding to a swinging pattern and a swinging frequency on a feed motion of the laser beam corresponding to a processing path by means of control of the offset unit. Background Art

[0002] US 2016 / 0368089 A1 describes a laser welding head having a movable mirror in order to carry out a welding process with a wobble pattern.

[0003] DE 102019210618 A1 describes a laser material processing system, comprising: a material modification beam source for generating a process beam; a processing head coupled to the material modification beam source (Werkstoffmodifizierungsstrahlquelle) and having at least one process beam-scanning actuator for deflecting and moving the process beam on at least one axis at a processing location of a workpiece according to a wobbling pattern; and a control system for controlling at least the material modification beam source, the process beam-scanning actuator and the imaging beam-scanning actuator, wherein the control system is programmed to actuate the processing head so that the process beam scans in a wobbling pattern. In an example, the second mirror can be dimensioned smaller based on a smaller field of view and scanning angle, thereby enabling a higher speed movement of the second mirror.

[0004] EP 3157706 A1 describes a method for laser beam welding of at least two joint pairs by means of optical seam guidance, wherein a processing laser beam is scanned by a scanning device as a laser beam guide device with at least one oscillating mirror moved in a controlled manner over an optically detected guide edge corresponding to the desired weld seam course. High-frequency oscillations of the at least one oscillating mirror, which are adapted to the geometric conditions of the component and / or process-related conditions, are superimposed on the optical seam guidance by means of the scanning device. Summary of the invention

[0005] The system for material processing mentioned at the outset can be a system for material processing, in particular for laser beam welding or cutting, which guides the laser beam in a "pattern" (e.g., a circle, a figure of eight, etc.) over the workpiece by means of a deflection unit, such as a scanner. For this purpose, the shape of the "pattern" is additionally superimposed on the "main" relative movement of the laser beam and the workpiece by means of the scanner, which pattern defines the shape of the oscillating movement. Here, the main relative movement between the workpiece and the laser beam can also be implemented by the scanner or by another movement device, such as a robot, a gantry or the like. This main movement leads to an advantageous formation of the weld seam by superimposing the pattern, since the formation and width of the weld pool as well as the preheating and cooling of the base material or the weld can be influenced thereby.

[0006] A weakness of conventional two-dimensional scanner systems for superimposing the main relative and oscillating motions of the laser beam and the workpiece is that the size and geometry of the programmed pattern changes at higher oscillation frequencies at which the pattern is generated by the scanner. An example of this is shown in Figure 2 Shown in.

[0007] The object of the present invention is to provide a system for material processing by means of a laser beam in which the above-mentioned disadvantages are eliminated or at least reduced.

[0008] This object is achieved by the present invention. Advantageous embodiments and refinements are described below.

[0009] According to one aspect of the disclosure, a system for material processing by means of a laser beam is described, comprising: a deflection unit for deflecting the laser beam; and a swivel unit, which is configured to superimpose an oscillating motion of the laser beam having an oscillating pattern and an oscillating frequency on a feed motion of the laser beam corresponding to a processing path by means of control of the deflection unit, wherein the swivel unit is configured to control the deflection unit according to a compensated oscillating motion for implementing the oscillating motion, in which a control value for the deflection of the laser beam along the oscillating pattern is adapted according to the oscillating frequency and / or a path speed changed along the oscillating pattern is adapted according to a position of the laser beam in the oscillating pattern and the oscillating frequency. In particular, the control value for the deflection of the laser beam along the oscillating pattern can be adapted and stored according to the oscillating frequency and used to control the deflection unit according to the compensated oscillating motion, and / or the path speed changed along the oscillating pattern can be adapted and stored according to a position of the laser beam in the oscillating pattern and the oscillating frequency and used to control the deflection unit according to the compensated oscillating motion. The compensated oscillating motion can in particular contain a predetermined compensation. The adapted control value can be stored, for example, in the oscillating unit or in the control device or in a memory or in the software for control. The adapted path speed that changes along the oscillating pattern can be stored, for example, in the oscillating unit or in the control device or in a memory or in the software for control.

[0010] In this way, graphical representation errors can be pre-compensated or minimized. Graphic representation errors indicate deviations of the oscillation pattern, i.e., the shape or geometry of the oscillating movement from the desired oscillation pattern, which deviation results from the actual oscillation pattern being dependent on the oscillation frequency when the deflection unit is controlled. In order to achieve the desired oscillation pattern or the desired oscillation movement, the deflection unit must therefore be controlled in accordance with a compensated oscillation movement, in which the deflection and / or the trajectory speed of the laser beam along the oscillation pattern is adapted as a function of the oscillation frequency.

[0011] The feed motion can also be referred to as the relative motion of the laser beam and the workpiece. The oscillating motion of the laser beam can denote a repetitive motion along a predefined oscillating pattern at a predefined oscillating frequency. Here, the oscillating frequency can denote the frequency at which the oscillating pattern is repeated during the oscillating motion. The compensated oscillating motion can be respectively predefined for the number of oscillating frequencies. The compensated oscillating motion can be determined, for example, empirically and stored in a lookup table or a memory.

[0012] Thus, by controlling the deflection unit according to the compensated oscillating movement, a deflection of the laser beam can be achieved, which corresponds to a desired oscillating movement, in particular a desired oscillating pattern. In particular, when the deflection unit is controlled according to the control value, a deflection of the laser beam along a desired oscillating movement, in particular a desired oscillating pattern, can be achieved, or when a oscillating movement is carried out with a path speed determined for a corresponding oscillating frequency, image display errors can be reduced.

[0013] This superposition can be referred to as modulation. Thus, the position of the laser beam is modulated in at least one spatial dimension, preferably in at least two spatial dimensions, by the oscillating movement, corresponding to a two-dimensional oscillating pattern.

[0014] Basically, the oscillating motion of the laser beam to be realized is defined by a predetermined oscillating pattern and an oscillating frequency. The oscillating motion corresponding to the oscillating pattern should be implemented at a predetermined oscillating frequency. By controlling the compensated oscillating motion, the actual oscillating motion can be better approximated to the predetermined oscillating pattern, especially at relatively high oscillating frequencies. The basic idea of ​​the present invention is to counteract this effect when the graphic accuracy of the offset (deflection) of the laser beam deteriorates with increasing oscillating frequency, for example, by a targeted increase in the motion component according to the position in the oscillating pattern. The compensated oscillating motion can be understood as a theoretical oscillating motion, which is obtained theoretically under the condition of ignoring inertial effects and material flexibility and ignoring the movement limitations and speed of the offset unit. In other words, the control according to the compensated oscillating motion can be understood as a control with a compensated control value. Here, the concepts (of the laser beam) deflection and offset can be used interchangeably.

[0015] The control values ​​or control data for the compensated oscillating movements can be stored in a memory, for example. The control values ​​or control data for the respective compensated oscillating movements can be output, for example, in the form of a series of control parameters for controlling the deflection unit.

[0016] Compensation of graphical representation errors means that a predetermined compensation is carried out in order to compensate for expected graphical representation errors. Thus, instead of reacting only (only) to deviations from the setpoint movement, the control of the deflection unit is already carried out in advance based on a compensated swivel movement that includes the compensation. The compensation is therefore carried out in advance. Independently of this, the deflection unit, the swivel unit and / or the control unit for outputting electrical control signals to the deflection unit can have a regulator for implementing the swivel movement; in this case, not only better graphical accuracy can be achieved by the compensation, but also graphical representation errors that occur even with regulation when the swivel frequency increases can be compensated in advance, for example. In particular, regulation errors can be compensated in advance.

[0017] Thus, display errors of the oscillating pattern can be at least partially pre-compensated. Thus, the following effect can be counteracted: the size and geometry of the oscillating pattern change with increasing frequency, with which the corresponding oscillating movement is generated by the displacement unit. This effect can be determined, for example, by the inertia of the moving parts of the displacement unit, because the inertia acts more strongly with increasing movement frequency and causes the current actual oscillating position to remain behind the theoretical oscillating position according to the movement along the oscillating pattern on the section of the oscillating pattern. Thus, a certain deviation of the actual (actual) oscillating movement from the ideal oscillating movement corresponding to the oscillating pattern can be counteracted in advance by providing different compensated oscillating movements.

[0018] By ensuring improved accuracy of the graphic representation, process parameters such as laser power, oscillation frequency and feed speed can also be linearly increased relative to one another within certain ranges while approximately maintaining the quality of the weld seam. That is, the scalability of the found process parameters can be improved.

[0019] Therefore, in particular when the processing speed is increased, a corresponding increase in the oscillation frequency can be achieved while maintaining the oscillation pattern, i.e. the size or amplitude and shape (geometry) of the oscillating movement as much as possible. For example, an oscillation frequency in the range of less than 200 Hz and / or up to more than 500 Hz, in particular more than 600 Hz, can be used.

[0020] Furthermore, it is possible that the oscillation frequency can be predetermined by the user in another context. In this way, for example, the melt pool dynamics can be influenced in a targeted manner.

[0021] In particular, when the system is constructed from two different offset units, for example in order to optimize the structural space and / or the scanning field size, which have different inertias, a high image display accuracy can be achieved even with increasing oscillation frequency by a compensated oscillating movement that deviates from an ideal oscillating movement corresponding to the oscillating pattern, i.e. a shape and size of the oscillating movement that remain as constant as possible.

[0022] By setting different compensated oscillating movements for different oscillating frequencies, for example, the control of the displacement unit for the corresponding oscillating frequency can be calibrated so that the desired oscillating pattern is as close as possible to the actual oscillating movement. This can be done, for example, by empirically determining a compensated oscillating movement or a corresponding control value for at least one oscillating pattern to be used and for a certain oscillating frequency, respectively, so that the pattern and the amplitude of the oscillating movement remain approximately constant for all frequencies under consideration. The control values ​​or control data (e.g., control parameters) for the compensated oscillating movement can be stored, for example, in the software for controlling the displacement device and used accordingly in the process. In addition, the control values ​​for the corresponding compensated oscillating movement, for example, the control parameters for the amplitude, can be obtained by means of suitable algorithms or alternative automation methods, such as from the field of "artificial intelligence".

[0023] The empirical determination of the oscillation frequency of the compensated oscillating motion can be carried out, for example, by the following method: A laser (pilot laser) processes a medium, for example a sheet of paper, according to a predefined oscillating motion. Optionally, a camera can record the processing path, for example from the rear side of the medium. The processing steps are repeated for different oscillation frequencies and / or oscillation patterns, wherein the control values ​​or control data (control parameters) for the compensated oscillating motion are changed. The control values ​​for the compensated oscillating motion are changed until the result (processing path) obtained is adapted to the predefined oscillation pattern.

[0024] The sway pattern produced in this way can be determined at the support points and further control parameters can be inserted between the support points.

[0025] The control value for controlling the deflection unit according to the compensated oscillating motion can, for example, include a control parameter, in particular a sequence of control parameters, for controlling the deflection unit. The control parameter can, for example, include an amplitude for controlling the deflection in a first direction. The control parameter can, for example, include or define an amplitude for controlling the deflection in a first direction or an amplitude for controlling the deflection in a second direction. The second direction can be transverse or perpendicular to the first direction. In the case of a deflection mirror or a scanner mirror, the relevant amplitude for controlling the deflection can give a (rated) deflection of the mirror.

[0026] The control parameters may include an orientation or an orientation vector, which describes a position in the motion path of the compensated oscillating motion. The orientation may provide at least one coordinate for the offset position of the laser beam. The orientation vector may be described in a series of control parameters relative to the previously given orientation vector. The series of control parameters may, for example, be described for a series of support points corresponding to the motion path of the compensated oscillating motion. The segments of the compensated oscillating motion may be defined by the control parameters or by the difference between successive control parameters in a series of control parameters, for example as an orientation vector. The number of support points or the length of a series of control parameters may, for example, be in a range of up to 32 or more, preferably in a range of up to 64 or more, and particularly preferably in a range of up to 128 or more.

[0027] The control parameters can be defined for a fixed time, for example a fixed time period or time point, for example corresponding to the period duration of the oscillating motion, divided by the length of the series of control parameters (the number of elements of the series). For example, the maximum possible number of support points on a predetermined trajectory can be derived from the minimum value of the time period (the time interval between successive control parameters) and the trajectory speed along the oscillating motion trajectory, for example, which is predetermined by the user. The trajectory speed can be, for example, at least 1 m / s. The time period can be, for example, in the range of up to 10 μs or less.

[0028] The segments can be designed to be equidistant in time. Alternatively, in a series of control parameters, a control parameter can additionally include a time point or a trajectory speed with respect to a reference time point of the compensated oscillating motion, such as a trajectory speed assigned to the corresponding segment. The trajectory speed of the oscillating motion can be derived from the predetermined time sequence of the control parameters. The instantaneous rated trajectory speed of the oscillating motion can be derived, for example, from the currently retained (zurückzulegenden) orientation vector and the assigned time, wherein the time can be a fixed time period. The (actual) trajectory speed of the oscillating motion can be different from the rated trajectory speed. Here, the trajectory speed is understood to be the value of the trajectory speed in the oscillating motion of the laser beam, that is, a directionless value.

[0029] The compensated oscillating movement can include a larger control value for the deflection of the laser beam at a larger oscillating frequency at least in one direction of movement. As a result, for example, the inertia of a scanner mirror can be taken into account in the deflection.

[0030] The control value according to the compensated oscillating motion can be different from the control value corresponding to the oscillating pattern at a lower oscillating frequency by at least one overmodulated amplitude depending on the oscillating frequency. The amplitude can relate to a part of the oscillating pattern or a movement section of the oscillating motion. The overmodulation or additional amplitude can increase with increasing oscillating frequency. Here, the amplitude (or movement amplitude) is understood to be the degree of change of the oscillating position of the (compensated) oscillating motion in a single cycle, for example the maximum deviation of the oscillating position from the average position of the oscillating pattern.

[0031] In an embodiment, the system for material processing by means of a laser beam may further comprise: a control unit for outputting an electrical control signal to an offset unit based on a control value for a compensated swinging motion, wherein the swinging unit is configured to output a control value for a corresponding compensated swinging motion to the control unit via the control unit in order to control the offset unit.

[0032] A system for material processing by means of a laser beam may include a process beam guidance unit for guiding the laser beam relative to a workpiece according to a processing path.

[0033] The swivel unit can be implemented as a program unit, for example, as software or a computer program. The swivel unit can be part of a control unit. The control unit can be designed, for example, to implement the functions of the swivel unit.

[0034] The wobble pattern to be used may be, for example, a predefined wobble pattern or a selectable wobble pattern, for example, selectable by a user.

[0035] Material processing by means of a laser beam can include, for example, laser welding, laser metal deposition, 3D printing, laser cutting or laser soldering.

[0036] In an embodiment, the control of the displacement unit according to the compensated oscillating movement comprises at least one of the following: compensation of a reduction in amplitude of at least one section of the oscillating pattern, in particular according to the oscillating frequency; and compensation of shape deviations of at least one section of the oscillating pattern, in particular according to the oscillating frequency. In the case of an increase in the oscillating frequency, for example, without compensation, graphic display errors in the form of a reduced amplitude (extended dimension) of a section of the oscillating pattern and / or in the form of a (comprehensive) shape that differs from the oscillating pattern can occur. By (pre)compensation, it is possible to achieve the greatest possible retention of the pattern and amplitude even when the oscillating frequency is increased.

[0037] In some embodiments, the compensated oscillating motion used corresponds to an oscillating pattern scaled by a factor according to the oscillating frequency. The control value for the deflection of the laser beam along the oscillating pattern can be scaled, for example, by a factor that depends on the oscillating frequency. The coefficient can be referred to as a scaling factor or a stretching factor. The coefficient may include two components, corresponding to separately defined scalings along a first direction and a second direction, such as x and y. The coefficient may present different values ​​depending on the oscillating frequency. Preferably, a plurality of different compensated oscillating motions for different oscillating frequencies and / or for different oscillating patterns are provided, wherein the absolute values ​​of the coefficients or their components increase as the oscillating frequency increases, respectively. At low frequencies in the setting range of the oscillating frequency, the coefficient may, for example, be equal to 1, or each component of the coefficient may be equal to 1.

[0038] In one embodiment, control values ​​for the deflection of the laser beam along the weaving pattern can be stored in a memory and / or in a table for different weaving frequencies.

[0039] The compensated oscillating motion can, for example, define or determine the trajectory speed according to the position in the oscillating pattern. Therefore, the pre-compensation can be implemented in such a way that the contour accuracy or the graphic accuracy is improved, but the trajectory speed at the key points of the graphic should, for example, deviate from the specified value by a defined limit. To this end, for example, the trajectory speed specified value can first be changed by a certain limit in some sections (for example, areas or segments of the graphic) until the measured graphic overlaps with the desired graphic as well as possible. Such empirically obtained variations of the trajectory speed are then stored accordingly in the control device (i.e. the oscillating unit) and applied in the corresponding oscillating patterns and oscillating frequencies. In particular, the corresponding control values ​​or control data for each compensated oscillating motion are stored. The changed trajectory speed can, for example, exceed the trajectory speed pre-set for the oscillating pattern and the associated oscillating frequency at least at one position of the oscillating pattern. The changed trajectory speed can, for example, exceed the subsequent possible displacement unit at least at one position of the oscillating pattern for the oscillating frequency.

[0040] The deflection unit may comprise a first deflection unit and a second deflection unit for deflecting the laser beam in various directions, for example the first and second directions mentioned. The deflection in the second direction may be carried out independently of the deflection in the first direction and may be controlled. The deflection unit may be a 2D deflection unit, for example a 2D scanning system. The second direction may be offset by 90° relative to the first direction or by an angle different from 90° relative to the first direction. The first deflection unit and the second deflection unit may comprise, for example, a first scanner unit and a second scanner unit.

[0041] The deflection unit may include at least one mirror. The deflection unit may include a drive unit, for example a galvanometer drive or a piezoelectric drive. The deflection unit may include at least one drive unit for each mirror. The first deflection unit may include, for example, a drive unit and a mirror, and the second deflection unit may include a drive unit and a mirror. The respective drive units may include, for example, a galvanometer drive or a piezoelectric drive. For example, a deflection in the X direction (for example as a first direction) and an independent deflection in the Y direction (for example as a second direction) may be realized by the respective deflection units.

[0042] The offset unit may comprise at least one galvanometer mirror. The first offset unit may, for example, comprise a first (galvanometer) mirror and the second offset unit may comprise a second (galvanometer) mirror. The axes of rotation of the (galvanometer) mirrors may be arranged perpendicularly to one another or at an angle different from 90°. For example, an offset in the X direction (e.g. as a first direction) and an offset in the Y direction (e.g. as a second direction) independent of this may be achieved by means of corresponding offset units. An offset unit with a galvanometer mirror may also be referred to as a galvanometer scanner. The galvanometer mirror operates according to the galvanometer principle, in which the mirror follows an applied current or electric field. Although embodiments are described with respect to galvanometer mirrors, the embodiments are not limited thereto and the offset unit may also comprise a piezoelectric-based drive unit.

[0043] In an embodiment, the offset unit may include a first offset unit and a second offset unit, wherein the first offset unit is configured to offset the laser beam in a first direction and the second offset unit is configured to offset the laser beam in a second direction. The first direction may be different from the second direction, or the first direction and the second direction may be perpendicular to each other, i.e., form two axes of a Cartesian coordinate system. Here, the first offset unit and the second offset unit may have substantially the same dynamic properties. The first offset unit and the second offset unit may, for example, have substantially the same inertia and / or substantially the same rigidity. This simplifies the implementation of a graphically accurate swinging motion. The first offset unit and the second offset unit may have substantially the same moving parts or consist of substantially the same moving parts, i.e., be constructed identically. The first offset unit and the second offset unit may in particular each have mirrors of the same size and / or drive units of the same type. This may result in substantially the same dynamics of the two offset units.

[0044] The image accuracy can be improved by a design of the displacement unit, for example a 2D scanning system, that is as symmetrical as possible. To this end, the displacement unit can be constructed from two identical displacement units, so that the mechanical properties of the displacement units are as identical as possible. Alternatively, it is also possible for the two displacement units to be constructed differently, but it must be ensured that the properties of the displacement units with respect to inertia and rigidity are as identical as possible and that the displacement units thus have the same dynamic properties.

[0045] Additionally, the contour accuracy can be improved by arranging two (eg identical) offset units at an angle of 90° relative to one another. This configuration is optimized with regard to contour accuracy. Thus, the first direction and the second direction can be oriented at 90° relative to one another.

[0046] In an embodiment, the oscillating unit is further configured to control the power modulation of the laser beam as a function of the position in the oscillating pattern when the deflection unit is controlled as a function of the compensated oscillating motion. The power modulation of the laser can lead to particularly advantageous properties of the oscillating motion in that the energy input can be determined spatially in a more targeted manner. The energy input in the extension of the current processing point during the movement of the processing point along the main trajectory segment (processing path) can be controlled both by the oscillating motion and additionally by the power modulation. The system can, for example, have a modulation unit for modulating the power of the laser beam, and the oscillating unit can be configured to control the power modulation of the laser beam by actuating the modulation unit as a function of the position in the oscillating pattern. This correlation can be given by a fixed time profile of the compensated oscillating motion.

[0047] According to another aspect of the disclosure, a method for material processing by means of a laser beam is described, the method comprising: superimposing a feed movement of the laser beam corresponding to a processing path with a wobbling movement of the laser beam corresponding to a wobbling pattern and a wobbling frequency by means of a deflection of the laser beam by means of a deflection unit, wherein, in order to implement the wobbling movement, the deflection unit is controlled according to a compensated wobbling movement, in which a control value for the deflection of the laser beam along the wobbling pattern is adapted according to the wobbling frequency and / or a trajectory speed of the wobbling movement that changes along the wobbling pattern is adapted according to a position of the laser beam in the wobbling pattern and according to the wobbling frequency. In particular, the control value for the deflection of the laser beam along the wobbling pattern can be adapted and stored according to the wobbling frequency and used to control the deflection unit according to the compensated wobbling movement, and / or the trajectory speed that changes along the wobbling pattern can be adapted and stored according to a position of the laser beam in the wobbling pattern and the wobbling frequency and used to control the deflection unit according to the compensated wobbling movement. The compensated wobbling movement can in particular include a predetermined compensation. The adapted control value can be stored in the swing unit or in the control device or in the memory or in the software for control, for example. The adapted track speed that changes along the swing pattern can be stored in the swing unit or in the control device or in the memory or in the software for control, for example.

[0048] In the previous calibration step, a control value for the deflection of the laser beam can be determined for multiple oscillation frequencies, so that when the offset unit is controlled according to the control value, the deflection of the laser beam corresponds to the desired oscillation motion, especially the desired oscillation pattern. In the previous calibration step, the trajectory speed of each oscillation motion along the oscillation pattern change can also be determined for multiple oscillation frequencies, so that the graphic display error is reduced in the implementation of the oscillation motion with the trajectory speed determined for the corresponding oscillation frequency. In other words, the control value or control parameter can be determined empirically for the determined oscillation pattern and / or oscillation frequency, so that the oscillation pattern or shape of the oscillation motion remains unchanged for all the oscillation frequencies studied. Finally, these control values ​​can be stored in the oscillation unit for controlling the offset unit and used accordingly in the method. Similarly, the trajectory speed along the oscillation pattern can be changed for the determined oscillation pattern and / or oscillation frequency until the generated oscillation pattern overlaps as well as possible with the desired oscillation pattern. Subsequently, the trajectory speed changed along the oscillation pattern obtained in this way can be stored in the oscillation unit for controlling the offset unit and applied in the method.

[0049] The method may be a method for operating a system for material processing by means of a laser beam, as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present invention is described in detail below with reference to the accompanying drawings. In the accompanying drawings:

[0051] Figure 1 A schematic illustration of a system for material processing by means of a laser beam according to an embodiment of the present disclosure;

[0052] Figure 2 A schematic illustration of the change in the oscillation pattern as a function of the oscillation frequency for identical control values ​​of a deflection unit of a system for material processing by means of a laser beam;

[0053] Figure 3 A schematic diagram of a swing pattern according to a swing frequency in a system for material processing according to an embodiment of the present disclosure; and

[0054] Figure 4 Schematic illustration of an offset unit in the form of a symmetrically configured two-dimensional scanner of a system for material processing according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0055] Unless otherwise indicated, the same reference numerals are used below for identical and identically acting elements.

[0056] Figure 1 A schematic diagram of a system for material processing by means of a laser beam according to an embodiment of the present disclosure is shown. The system comprises a laser processing head 10 having a process beam guidance unit 20 for guiding a laser beam 14 relative to a workpiece 12. The laser head has, for example, a feed speed relative to the workpiece 12.

[0057] The laser processing head 10 is provided for focusing or concentrating a laser beam 14 emerging from a laser source or the end of a laser conducting fiber 16 onto a workpiece 12 to be processed by means of collimating and focusing optics 30, 32, in order to thereby carry out processing or a processing process. The processing may include, for example, laser cutting, laser soldering or laser melting.

[0058] The laser processing head 10 comprises a deflection unit 40 in the form of a scanner module, such as a two-dimensional scanner, for deflecting the laser beam 14 and for positioning the processing point of the laser beam 14 in the x-direction and the y-direction.

[0059] The displacement unit 40 comprises a first displacement unit 40.1 for positioning the laser beam 14 in the x-direction and a second displacement unit 40.2 for positioning the laser beam 14 in the y-direction. In the example shown, the displacement units 40.1, 40.2 each comprise a galvano mirror 42.

[0060] The system further comprises a control unit 50 having drive electronics 52 for outputting analog electrical control signals to the deflection units 40.1, 40.2 for controlling the current mirrors 42. The control signals each have an amplitude which causes a corresponding deflection movement of the associated current mirror 42.

[0061] The system further comprises a control computer 54, in which a swivel unit 60 is active. The swivel unit 60 is configured to output control values ​​for a compensated swivel motion to the control unit 50 in order to control the deflection unit 40 by the control unit 50. The control computer 54 is configured to control the relative motion of the laser beam 14 and the workpiece 12 by the process beam guidance unit 20 according to the basic machining path. The swivel unit 60 is configured to superimpose an swivel motion of the laser beam 14 corresponding to the swivel pattern and the swivel frequency on the relative motion by means of the deflection unit 40 by the control unit 50. The swivel pattern to be used is selected by the user, for example, and can be, for example, a circle, a figure of eight, or another closed shape.

[0062] If a wobbling motion corresponding to the same movement path or a wobbling motion with the same control command is always used in a predetermined wobbling pattern with a gradually increasing wobbling frequency, the size and geometry (shape) of the wobbling motion actually performed at high frequencies may change due to the inertia of the displacement units 40.1, 40.2 and may not be as good as the desired wobbling motion, for example, in terms of the movement amplitude. Figure 2 Schematically shown as a comparative example for a swaying pattern in the form of a horizontal figure eight. From left to right, swaying movements with swaying frequencies of 50 Hz, 195 Hz, 390 Hz, 520 Hz and 625 Hz are shown. A graphical display error is shown, which is indicated by a reduced amplitude of movement in the x direction and in particular in the y direction, and thus also includes the changing geometry of the graphical display error.

[0063] exist Figure 1 In the embodiment, the oscillating unit 60 is configured to pre-compensate the graphic display errors of the superimposed oscillating movement that occur when the oscillating frequency increases. To this end, the oscillating unit 60 controls the displacement unit 40 according to the compensated oscillating movement that is dependent on the oscillating frequency and that differs from the normal oscillating movement that corresponds to the oscillating pattern and does not take into account the oscillating frequency.

[0064] Figure 3The resulting, actually implemented oscillating motion is schematically shown. In this example, the compensated oscillating motion is generated by multiplying the control value for the reference oscillating motion at 50 Hz with the corresponding stretching factors for the motion amplitude. In this case, an x ​​stretching factor and a y stretching factor are used respectively, which can be different from each other.

[0065] exist Figure 3 From left to right, the Figure 2 The oscillating motion at the same oscillating frequency in the example, wherein the stretching factor (1,0; 1,0) is used at an oscillating frequency of 50 Hz, the stretching factor (1,04; 1,09) is used at an oscillating frequency of 195 Hz, the stretching factor (1,2; 1,35) is used at an oscillating frequency of 390 Hz, the stretching factor (1,3; 2,1) is used at an oscillating frequency of 520 Hz, and the stretching factor (1,3; 4,0) is used at an oscillating frequency of 625 Hz. Figure 2 (without the preceding stretch factor for the amplitude), a clear improvement in the contour accuracy with respect to a predefined wobble pattern can be seen.

[0066] Therefore, by presetting the changed motion amplitude which can be stored in the memory 62, it is possible to pre-compensate for the Figure 2 The amplitude reduction shown in , can also pre-compensate for the shape deviations associated therewith. Due to the amplitude of the overshoot (übersteuert) of the control parameters for the control unit 50 by the stretch factor, the actual oscillating movement corresponds to the desired oscillating movement, since the control of the deflection unit 40 is based on the compensated oscillating movement. In this case, the changed path speed (path speed) in the course of the oscillating movement can be determined from the quantitative value.

[0067] exist Figure 1 In the embodiment, the control computer 54 can also be configured to control the power modulation of the laser beam 14 as a function of the position in the wobble pattern via the power module 56. The power module 58 can, for example, control a laser source.

[0068] exist Figure 3 In the example of FIG. 4 , the displacement units 40 . 1 and 40 . 2 have, for example, mirrors 42 of different sizes, so that deflections of different sizes of the movement amplitude in the x-direction and the y-direction are necessary, while Figure 4 In both views, a symmetrically designed displacement unit 40 of a further specific embodiment of a system for material processing by means of a laser beam is shown by way of example. Figure 4The displacement unit 40 of the embodiment of the present invention has two symmetrically designed first and second displacement units 40.1, 40.2, which in particular have mirrors 42 of the same size and identical galvanometer drive units 44 for the mirrors 42. Due to the identical design of the two displacement units 40.1 and 40.2 and the identical dynamics caused, shape deviations of the oscillating movement can be better pre-compensated. In addition, the system can be similar to Figure 1 system structure.

[0069] In the example described, the adjustment angle of the deflection unit can be, for example, approximately 1°-2°, and the deflection of the laser beam is, for example, in the range of 10 mm to 20 mm. Thus, for a swivel movement with an amplitude in the range of, for example, 1 mm to 2 mm, a deflection angle of approximately 5-10 arc minutes is obtained for the swivel.

Claims

1. A system for material processing by means of a laser beam, comprising: a deflection unit (40) for deflecting the laser beam (14); and A swing unit (60) is configured to superimpose a swing motion of the laser beam (14) having a swing pattern and a swing frequency on a feed motion of the laser beam (14) corresponding to a processing path by controlling the offset unit (40), in, The oscillating unit (60) is configured to control the displacement unit (40) according to the compensated oscillating movement in order to implement the oscillating movement, wherein a control value for the deflection of the laser beam (14) along the oscillating pattern in the compensated oscillating movement is adapted and stored according to the oscillating frequency and is used to control the displacement unit (40) according to the compensated oscillating movement, and / or a trajectory speed of the oscillating movement that changes along the oscillating pattern is adapted and stored according to the position of the laser beam (14) in the oscillating pattern and the oscillating frequency and is used to control the displacement unit (40) according to the compensated oscillating movement, Wherein, the control of the offset unit (40) according to the compensated swinging motion includes at least one of the following: a reduction in the amplitude of at least one section of the swinging pattern according to compensation of the swinging frequency; and a shape deviation of at least one section of the swinging pattern according to compensation of the swinging frequency.

2. The system according to claim 1, wherein: The control value for the deflection of the laser beam (14) along the oscillation pattern is scaled by a factor that is dependent on the oscillation frequency.

3. The system according to claim 1 or 2, wherein: A control value for the deflection of the laser beam (14) along the oscillation pattern is stored in a memory and / or in a table for different oscillation frequencies.

4. The system according to claim 1 or 2, wherein the offset unit (40) comprises a first offset unit (40.1) and a second offset unit (40.2), wherein: The first deflection unit (40.1) is configured to deflect the laser beam (14) in a first direction (x), and the second deflection unit (40.2) is configured to deflect the laser beam (14) in a second direction (y), wherein the first deflection unit (40.1) and the second deflection unit (40.2) have substantially the same dynamic characteristics.

5. The system according to claim 1 or 2, wherein the offset unit (40) comprises a first offset unit (40.1) and a second offset unit (40.2), wherein: The first deflection unit (40.1) is configured to deflect the laser beam (14) in a first direction (x), and the second deflection unit (40.2) is configured to deflect the laser beam (14) in a second direction (y), wherein the first deflection unit (40.1) and the second deflection unit (40.2) are constructed substantially identically.

6. The system according to claim 1 or 2, wherein the offset unit (40) comprises a first offset unit (40.1) and a second offset unit (40.2), wherein: The first deflection unit (40.1) is configured to deflect the laser beam (14) in a first direction (x), and the second deflection unit (40.2) is configured to deflect the laser beam (14) in a second direction (y), wherein the first deflection unit (40.1) and the second deflection unit (40.2) are arranged at an angle of 90° relative to each other.

7. The system according to claim 1 or 2, in which the oscillation unit (60) is configured to control a power modulation of the laser beam (14) as a function of a position of the laser beam (14) in the oscillation pattern.

8. A method for material processing by means of a laser beam, comprising: By means of a displacement unit (40), a feed movement of the laser beam (14) corresponding to the processing path is superimposed on an oscillating movement of the laser beam (14) corresponding to an oscillation pattern and an oscillation frequency by deflecting the laser beam (14). wherein, in order to implement the oscillating motion, the displacement unit (40) is controlled according to the compensated oscillating motion, in the compensated oscillating motion, a control value for the deflection of the laser beam (14) along the oscillating pattern is adapted and stored according to the oscillating frequency and used to control the displacement unit (40) according to the compensated oscillating motion, and / or a trajectory speed of the oscillating motion that changes along the oscillating pattern is adapted and stored according to the position of the laser beam (14) in the oscillating pattern and the oscillating frequency and used to control the displacement unit (40) according to the compensated oscillating motion, Wherein, the control of the offset unit (40) according to the compensated swinging motion includes at least one of the following: a reduction in the amplitude of at least one section of the swinging pattern according to compensation of the swinging frequency; and a shape deviation of at least one section of the swinging pattern according to compensation of the swinging frequency.

9. The method according to claim 8, wherein: In a calibration step preceding the superposition, control values ​​for the deflection of the laser beam (14) are determined for a plurality of oscillation frequencies, so that when the displacement unit is controlled in accordance with the control values, the deflection of the laser beam (14) corresponds to a desired oscillating movement, and / or Therein, in a calibration step preceding the superposition, a respectively modified path speed of the oscillating movement along the oscillating pattern is determined for a plurality of oscillating frequencies, so that when the oscillating movement is carried out with the modified path speed determined for the respective oscillating frequency, graphic display errors are reduced.

10. The method according to claim 8, wherein: In a calibration step preceding the superposition, control values ​​for the deflection of the laser beam (14) are determined for a plurality of oscillation frequencies, so that when the displacement unit is activated in accordance with the control values, the deflection of the laser beam (14) corresponds to a desired oscillation pattern.

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