MATERIAL PROCESSING BY MEANS OF A LASER BEAM IN A WOBBLE MOVEMENT

Abstract

A system for machining materials by means of laser beam includes a deflection device for deflecting the laser beam and a wobble device configured to superimpose a wobble movement of the laser beam with a wobble figure and a wobble frequency onto a feed movement of the laser beam corresponding to a machining path by controlling the deflection device. The wobble device is configured, for carrying out the wobble movement, to control the deflection device according to a compensated wobble movement. Control values for a deflection of the laser beam along the wobble figure are adapted as a function of the wobble frequency and/or a path speed of the wobble movement that varies along the wobble figure is adapted as a function of a position of the laser beam in the wobble figure and as a function of the wobble frequency.

Claims

1. A system for machining materials by means of laser beam, comprising: a deflection device for deflecting the laser beam; and a wobble device configured to superimpose a wobble movement of said laser beam with a wobble figure and a wobble frequency onto a feed movement of said laser beam corresponding to a machining path by controlling said deflection device; wherein; said wobble device is configured, for carrying out the wobble movement, to control said deflection device according to a compensated wobble movement; and control values for a deflection of said laser beam along the wobble figure are adapted as a function of the wobble frequency and/or a path speed of the wobble movement that varies along the wobble figure is adapted as a function of a position of said laser beam in the wobble figure and as a function of the wobble frequency.

2. The system according to claim 1, wherein controlling said deflection device according to the compensated wobble movement comprises at least one of: compensating for a reduction in amplitude of at least a portion of the wobble figure as a function of the wobble frequency; and compensating for a shape deviation of at least a portion of the wobble figure as a function of the wobble frequency.

3. The system according to claim 1, wherein the control values for a deflection of said laser beam along the wobble figure are scaled with a factor dependent on the wobble frequency.

4. The system according to claim 1, wherein control values for a deflection of said laser beam along the wobble figure are stored in a memory and/or in a table for different wobble frequencies.

5. The system according to claim 1, wherein said deflection device comprises a first deflection device and a second deflection device, wherein said first deflection device is configured to deflect said laser beam in a first direction, said second deflection device is configured to deflect said laser beam in a second direction, and wherein said first deflection device and said second deflection device have substantially the same dynamic characteristics.

6. The system according to claim 1, wherein said deflection device comprises a first deflection device and a second deflection device, wherein said first deflection device is configured to deflect said laser beam in a first direction, said second deflection device is configured to deflect said laser beam in a second direction, and wherein said first deflection device and said second deflection device are configured substantially identically.

7. The system according to claim 1, wherein said deflection device comprises a first deflection device and a second deflection device, said first deflection device is configured to deflect said laser beam in a first direction, said second deflection device is configured to deflect said laser beam in a second direction, and wherein said first deflection device and said second deflection device are arranged at an angle of 90° to one another.

8. The system according to claim 1, wherein said wobble device is configured to control a power modulation of said laser beam as a function of a position of said laser beam in the wobble figure.

9. A method for material machining by means of a laser beam, comprising: superimposing a wobble movement of the laser beam according to a wobble figure and a wobble frequency onto a feed movement of said laser beam corresponding to a machining path by deflecting said laser beam by means of a deflection device; wherein; for carrying out the wobble movement, said deflection device is controlled according to a compensated wobble movement; and control values for a deflection of said laser beam along the wobble figure are adapted as a function of the wobble frequency and/or a path speed of the wobble movement that varies along the wobble figure is adapted as a function of a position of said laser beam in the wobble figure and as a function of the wobble frequency.

10. The method according to claim 9, wherein: in a preceding calibration step, control values for a deflection of said laser beam are determined for a plurality of wobble frequencies such that, when said deflection device is controlled according to the control values, a deflection of said laser beam corresponds to the desired wobble movement, in particular the desired wobble figure; and/or wherein, in a preceding calibration step, a path speed of the wobble movement that varies along the wobble figure is determined for a plurality of wobble frequencies such that, when the wobble movement is carried out with the varying path speed determined for the corresponding wobble frequency, a figure reproduction error is reduced.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention is described in detail below with reference to figures. In the figures:

[0052] FIG. 1 shows a schematic diagram of a system for material machining by means of laser beam according to embodiments of the present disclosure;

[0053] FIG. 2 shows a schematic diagram of the change in a wobble figure as a function of a wobble frequency with otherwise identical control values of deflection devices of a system for material machining by means of laser beam;

[0054] FIG. 3 shows a schematic diagram of a wobble figure as a function of a wobble frequency in a system for material machining according to embodiments of the present disclosure; and

[0055] FIG. 4 shows a schematic diagram of a deflection device in the form of a symmetrically configured 2D scanner of a system for material machining according to embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[0056] Unless otherwise noted, the same reference symbols are used for identical and equivalent elements below.

[0057] FIG. 1 shows a schematic diagram of a system for material machining by means of laser beam according to embodiments of the present disclosure. The system comprises a laser machining head 10 including a process beam guiding device 20 for guiding a laser beam 14 relative to a workpiece 12. The laser head has a feed speed {right arrow over (v)} relative to the workpiece 12, for example.

[0058] The laser machining head 10 is configured to focus or collimate a laser beam 14 emerging from a laser light source or an end of a laser optical fiber 16 with the aid of collimation and focusing optics 30, 32 onto a workpiece 12 to be machined in order to thereby carry out machining or a machining process. Machining may comprise laser cutting, soldering or welding, for example.

[0059] The laser machining head 10 includes a deflection device 40 in the form of a scanner module, such as a 2D scanner, for deflecting the laser beam 14 and for positioning the machining point of the laser beam 14 in the x-direction and y-direction.

[0060] The deflection device 40 comprises a first deflection device 40.1 for positioning the laser beam 14 in the x-direction and a second deflection device 40.2 for positioning the laser beam 14 in the y-direction. In the example shown, the deflection devices 40.1, 40.2 each include a galvanic mirror 42.

[0061] The system further comprises a control device 50 including driver electronics 52 for outputting analog electrical control signals to the deflection devices 40.1, 40.2 in order to control the galvanic mirrors 42. The control signals each have an amplitude which brings about a movement of the respective galvanic mirror 42 towards a corresponding deflection of the galvanic mirror 42.

[0062] The system further comprises a control computer 54 in which a wobble device 60 is implemented. The wobble device 60 is configured to output control values for a compensated wobble movement to the control device 50 so that the deflection device 40 can be controlled by the control device 50. The control computer 54 is configured to control a relative movement of the laser beam 14 and the workpiece 12 according to a primary machining path via the process beam guiding device 20. The wobble device 60 is configured to superimpose a wobble movement of the laser beam 14 corresponding to a wobble figure and a wobble frequency onto the relative movement by controlling the deflection device 40 via the control device 50. The wobble figure to be used is selected, for example, by a user and may be, for example, one of a circle, a figure eight, or another closed shape.

[0063] If a wobble movement corresponding to a same movement path or with same control commands is always used for a given wobble figure with increasing wobble frequency, the size and geometry (shape) of the wobble movement actually performed would change and, for example, would lag behind the desired wobble movement with regard to a movement amplitude. FIG. 2 shows this schematically as a comparative example of a wobble figure in the form of a figure eight. Shown from left to right are wobble movements with a wobble frequency of 50 Hz, 195 Hz, 390 Hz, 520 Hz and 625 Hz. A figure reproduction error is reflected in a reduced movement amplitude in the x-direction and especially in y-direction and thereby also comprises a changed geometry of the figure.

[0064] In FIG. 1, the wobble device 60 is configured to perform a precompensation for the figure reproduction error of the superimposed wobble movement that occurs with increasing wobble frequency. For this purpose, the wobble device 60 controls the deflection device 40 according to a compensated wobble movement which is a function of the wobble frequency and deviates from a generic wobble movement which corresponds to the wobble figure and does not take the wobble frequency into account.

[0065] FIG. 3 schematically shows the resulting wobble movements that are actually carried out. In this example, the compensated wobble movements are generated by multiplying the control values for a reference wobble movement at 50 Hz by respective stretch factors for the movement amplitudes. In each case, an x stretch factor and a y stretch factor are used, which may be different from one another.

[0066] The wobble movements at the same wobble frequencies as in FIG. 2 are shown in FIG. 3 from left to right, wherein the stretch factors (1.0; 1.0) are used at the wobble frequency of 50 Hz, the stretch factors (1.04; 1.09) are used at the wobble frequency of 195 Hz, the stretch factors (1.2; 1.35) are used at the wobble frequency of 390 Hz, the stretch factors (1.3; 2.1) are used at the wobble frequency of 520 Hz and the stretch factors (1.3; 4.0) are used at the wobble frequency of 625 Hz. Compared to FIG. 2 (without provision of stretch factors for the amplitudes), a significant improvement in the contour accuracy with regard to the specified wobble figure is apparent.

[0067] By providing the changed movement amplitudes, which may be stored in a memory 62, both the amplitude reductions shown in FIG. 2 and the associated shape deviation may be pre-compensated for. Due to the amplitudes of the control variables for the control device 50 being overdriven by the stretch factors, the actual wobble movement corresponds to the desired wobble movement since the control of the deflection device 40 is based on the compensated wobble movement. This may result in path speeds that vary in absolute value over the course of the wobble movement.

[0068] In FIG. 1, the control computer 54 may also be configured to control a power modulation of the laser beam 14 as a function of a position in the wobble figure by means of a power module 56. For this purpose, the power module 58 may control the laser light source, for example.

[0069] While, in the example in FIG. 3, the deflection devices 40.1 and 40.2 have mirrors 42 of different sizes so that different deviations in the movement amplitudes in x and y directions are required, FIG. 4 shows, in two views, an example of a symmetrically configured deflection device 40 of a further embodiment of a system for material machining by means of laser beam. The deflection device 40 of FIG. 4 has two symmetrically configured first and second deflection devices 40.1, 40.2, which in particular have mirrors 42 of the same size and galvanometer driving devices 44 of the same type for the mirrors 42. Due to the identical structure and the resulting identical dynamics of the two deflection devices 40.1 and 40.2, an even better precompensation for a shape deviation of the wobble movement may be achieved. Otherwise, the system may be configured similarly to the system in FIG. 1.

[0070] In the examples described, the adjustment angles of the deflection devices may be, for example, approximately 1°-2°, with deflections of the laser beam, for example, in the range of 10 mm to 20 mm. For a wobble movement with an amplitude in the range of 1 mm to 2 mm, for example, this results in deflection angles for wobbling of about 5-10 arc minutes.