Device and method for processing at least one workpiece by means of at least one laser beam

Abstract

The invention relates to a laser device (10) for processing, in particular laser welding, at least one workpiece (12) by means of at least one laser beam (14), having features of claim 1, and to a method for processing, in particular laser welding, at least one workpiece (12) by means of at least one laser beam (14), having features of the additional independent claim.

Description

[0001] Title: Device and method for machining at least one workpiece by means of at least one laser beam

[0002] Description

[0003] The invention relates to a laser device for processing at least one workpiece having features of claim 1 and a method for processing at least one workpiece having features of the independent claim.

[0004] When laser welding at least two components, CW (continuous wave) lasers with a constant power over the duration of the laser welding are usually used for deep welding. In particular when deep welding metallic materials with a low viscosity, instabilities can arise in the welding area, especially in the so-called keyhole. For example, spatter, pores and / or an irregular welding depth can arise. In order to reduce such instabilities, several laser beams can be superimposed. However, this cannot eliminate all instabilities, especially in the case of metallic materials with low viscosity. It is therefore the object of the present invention to provide a laser device and a method for processing, in particular laser welding, at least one workpiece, wherein the above disadvantages are eliminated.

[0005] The above object is achieved by a laser device for machining at least one workpiece by means of at least one laser beam having the features of claim 1. The machining may involve laser welding.

[0006] The laser device is set up to generate the laser beam with an output power, to focus it on the workpiece and to vary the output power of the laser beam with a variation frequency of at least 50 kHz (kilohertz) and a variation amplitude of at least 10% of the output power. The variation amplitude can be either positive or negative. In other words, the output power can be periodically increased (with a positive variation amplitude) or reduced (with a negative variation amplitude). The laser device is set up such that a rise time and / or a fall time of the variation amplitude is a maximum of 10 ps (microseconds).

[0007] In this case, rise time means the time required to increase the laser power to a maximum value (e.g. the positive variation amplitude). Correspondingly, fall time means the time required to reduce the laser power (output power) to a minimum value (e.g. the negative variation amplitude). This can achieve (additional) stabilization of the keyhole, particularly in workpieces with a lower viscosity, as a result of which spatter and pores decrease and the most continuous weld depth possible can be achieved. The instabilities of the keyhole can be avoided or at least reduced in particular by increasing and reducing the steam rate and steam pressure quickly enough to prevent the keyhole from collapsing. In other words, the keyhole can be prevented by specifically influencing the steam pressure (orthe steam rate ) can be stabilized, which can lead to less splashing, pores and a constant welding depth .

[0008] According to a further development of the laser device, the laser device for generating the laser beam can comprise a CW laser. The laser device can be configured such that the laser beam is modulated with a modulation frequency and a modulation amplitude. The modulation frequency can correspond to the variation frequency, and the modulation amplitude can correspond to the variation amplitude. The CW laser can have an average power of at least 0.2 kW, preferably at least 4 kW.

[0009] This allows the laser beam to be generated using simple means.

[0010] It is also conceivable that the laser device for generating the laser beam can comprise a pulsed laser. A pulse repetition rate of the pulsed laser can correspond to the variation frequency. The pulsed laser can have an average power of at least 0.2 kW (kilowatts), preferably at least 4 kW, and / or a pulse energy of at least 10 mJ (millijoule), preferably at least 50 mJ.

[0011] It is conceivable that the core region of the laser spot is generated by means of a pulsed laser (in particular an ns (nanosecond) pulsed laser) and the ring region of the laser spot is generated by means of a CW laser or vice versa.

[0012] The pulsed laser and / or the CW laser can each have a beam parameter product of a maximum of 8 mm*mrad (millimeters*millirad). The pulsed laser and / or the CW laser can each be designed as a (multi-mode) NIR (Near Infrared) laser. It is also conceivable that the pulsed laser and / or the CW laser can each be designed as a laser in the visible range (VIS laser) with a wavelength in a blue or green wavelength range. The pulsed laser and / or the CW laser can each be designed as a solid-state laser.

[0013] The laser device may include a control device. The control device may be configured to program and / or control the (high-frequency) modulation or pulsation with a variation frequency of at least 50 kHz.

[0014] The laser device may include a nozzle for supplying a shielding gas (cutting or welding gas) to the workpiece. This nozzle may have a Laval internal geometry.

[0015] According to a further development of the laser device, the laser device can be configured such that the laser beam generates a laser spot on the workpiece. The laser spot can have a core region and a ring region. The core region can be circular. The ring region can be ring-shaped. The core region can be arranged within the ring region. An average laser power density in the core region can be higher than an average laser power density in the ring region. The average laser power density in the ring region can, in particular, be a maximum of 5% of the laser power.

[0016] This allows for further stabilization of the weld area, especially the keyhole. This can further reduce instability (within the keyhole), resulting in fewer spatters and pores, and a consistent weld penetration.

[0017] According to a further development of the laser device, the laser device for generating the laser beam and / or the laser spot can comprise a fiber (2 in 1 fiber) with a core region and a ring region. The core region of the fiber can have an outer diameter of at most 30 pm (micrometers), in particular of at most 20 pm, preferably of at most 10 pm (e.g. for fundamental mode or single mode). Alternatively, the core region of the fiber can have a larger outer diameter, in particular of at least 50 pm or 100 pm (e.g. for multi-mode). Alternatively or additionally, the ring region can have an outer diameter of 200 pm or 400 pm. The core region can be arranged within the ring region. The ratio between the outer diameter of the core region and the outer diameter of the ring region can be in the range from 1:2 to 1:9, in particular 1:3, 1:4 or 1:6. The core region can have a cladding.The sheath can be arranged between the core region and the ring region.

[0018] The sheath can have a maximum thickness of 10 gm.

[0019] This allows for further stabilization of the weld area, especially the keyhole. This can further reduce instability (within the keyhole), resulting in fewer spatters and pores, and a consistent weld penetration.

[0020] According to a further development of the laser device, the laser device can be configured such that at least two laser beams are generated and focused on the workpiece. In particular, at least four laser beams can be generated and focused on the workpiece. In particular, all laser beams can be identically configured. Accordingly, all laser spots generated on the workpiece by the respective laser beams can also be identically configured. To generate multiple laser beams, the laser device can comprise an optical element for beam splitting, in particular a wedge switch.

[0021] This allows for further stabilization of the weld area, especially the keyhole. This can further reduce instability (within the keyhole), resulting in fewer spatters and pores, and a consistent weld penetration.

[0022] According to a further development of the laser device, the laser device can comprise a scanner optics system for moving the laser beam across the workpiece. The scanner optics system can have an imaging ratio in a range of 1:1 to 5:1, preferably 1.9:1 or 3.4:1. This allows the laser beam to be optimally focused on the workpiece and / or moved across the workpiece using simple means.

[0023] According to a further development of the laser device, the laser device can comprise an optical sensor for detecting the position of the laser beam and / or the workpiece. The optical sensor can be designed as a camera-based sensor or as a camera. It is also conceivable for the optical sensor to be designed as an interferometer-based sensor system. The laser beam and the optical sensor can be calibrated to one another.

[0024] This allows for simple position control of the laser beam and / or the workpiece. This allows for machining, particularly laser welding, of the workpiece to be carried out with the greatest possible precision.

[0025] The above object is further achieved by a method for machining at least one workpiece having the features of the independent claim. The machining may involve laser welding. The method comprises the following steps:

[0026] Providing the workpiece. The workpiece can be made of metal, in particular aluminum and / or copper. The workpiece can have a viscosity of maximum 5 mPa*s (millipascals*second) in the molten state (at melting temperature). The workpiece can have a thickness of maximum 4 mm. Generating and focusing at least one laser beam with an output power onto the workpiece.

[0027] Varying, in particular pulsing or modulating, the laser beam with a variation frequency of at least 50 kHz, a variation amplitude of at least 10% of the output power, and a rise and / or fall time of the variation amplitude of no more than 10 ps (microseconds). The variation amplitude can be either positive or negative. In other words, the output power can be periodically increased (with a positive variation amplitude) and / or reduced (with a negative variation amplitude).

[0028] This can lead to (additional) stabilization of the keyhole, particularly in workpieces with a lower viscosity, which reduces spatter and pores and allows the most consistent weld penetration depth to be achieved. The instabilities of the keyhole can be avoided or at least reduced in particular by increasing and reducing the steam rate and steam pressure quickly enough to prevent the keyhole from collapsing. In other words, the keyhole can be stabilized by specifically influencing the steam pressure (or the steam rate), which can lead to fewer spatter, pores and a constant weld penetration depth.

[0029] The method may comprise the step of:

[0030] Supplying a protective gas (cutting or welding gas) to the workpiece, particularly in the area where the workpiece is being processed. This can be achieved using a nozzle, particularly one with a Laval internal geometry.

[0031] According to a further development of the method, the method may comprise the step:

[0032] Moving the laser beam and / or the workpiece to generate a feed rate of the laser beam generated on the workpiece. The laser beam can be moved across the workpiece using scanner optics. The movement of the laser beam and / or the workpiece can be a relative movement between the laser beam and the workpiece. In other words, either the laser beam or the workpiece, or both, can be moved.

[0033] This allows continuous machining of the workpiece, e.g. a weld seam, to be carried out using simple means.

[0034] According to a further development of the method, the method may comprise the step:

[0035] Determining the position of the laser beam and / or the workpiece. This can be achieved using an optical sensor.

[0036] Possible readjustment of a processing position of the laser beam and / or the workpiece.

[0037] This allows for simple position control and, in the event of a deviation, appropriate adjustment of the laser beam and / or the workpiece. According to a further development of the method, a laser device as described above can be used to carry out the method.

[0038] With regard to the advantages that can be achieved, reference is made to the relevant explanations regarding the laser device. The measures described in connection with the laser device and / or those explained below can be used to further refine the method.

[0039] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of an embodiment with reference to the drawings. They show:

[0040] Fig. 1 is a schematic representation of a laser device for processing at least one workpiece;

[0041] Fig. 2 is a schematic diagram of a power curve of a CW laser of the laser device according to Figure 1.

[0042] In the following description and in the figures, corresponding components and elements have the same

[0043] Reference sign .

[0044] Figure 1 schematically shows a laser device 10 for processing at least one workpiece 12 by means of at least one laser beam 14. In the present case, the processing involves laser welding. The laser device 10 is set up to generate the laser beam 14 with an output power 16 (cf. Figure 2) and to focus it onto the workpiece 12. The laser device 10 is further set up to vary the output power 16 of the laser beam 14 with a variation frequency of at least 50 kHz and a variation amplitude 18 of at least 10% of the output power 16. The laser device 10 is set up such that a rise time 20 and / or a fall time 22 of the variation amplitude 18 is a maximum of 10 ps.

[0045] The laser device 10 can comprise a CW laser for generating the laser beam 14. The laser device 10 can be configured such that the laser beam 14 is modulated with a modulation frequency and a modulation amplitude. The modulation frequency can correspond to the variation frequency, and the modulation amplitude can correspond to the variation amplitude 18. The CW laser can have an average power of at least 1 kW, in particular of at least 4 kW.

[0046] The laser device 10 comprises a scanner optics 24 for moving the laser beam 14 over the workpiece 12. The scanner optics 24 can have an imaging ratio in a range from 1:1 to 5:1, preferably from 1.9:1 or 3.4:1.

[0047] In this case, the laser device 10 also comprises an optical sensor 26 for detecting the position of the laser beam 14 and / or the workpiece 12.

[0048] The laser device 10 can be configured such that the laser beam 14 generates a laser spot on the workpiece 12. The laser spot can have a core region, in particular a circular one. The laser spot can have a ring region, in particular a ring-shaped one. The core region of the laser spot can be arranged in the ring region of the laser spot. An average laser power density in the core region of the laser spot can be higher than an average laser power density in the ring region of the laser spot.

[0049] To generate the laser beam 14 and / or the laser spot, the laser device 10 can comprise a fiber. The fiber can comprise a core region and a ring region. The core region can be arranged within the ring region. The core region can have an outer diameter of 50 pm or 100 pm. The ring region can have an outer diameter of 200 pm or 400 pm.

[0050] The laser device 10 can be configured such that at least two, in particular at least four, laser beams 14 are generated and focused onto the workpiece 12. All laser beams 14 (or the laser spots generated by the respective laser beams 14) can be identically configured.

[0051] Figure 2 shows a schematic diagram of a power curve of the CW laser of the laser device 10 according to Figure 1 .

[0052] In the diagram shown, the power 28 of the CW laser of the laser device 10 is plotted in watts over time 30 in seconds. In other words, the x-axis represents time 30 in seconds, and the y-axis represents power 28 in watts.

[0053] The power 28 of the CW laser is modulated in this case with the modulation frequency and the modulation amplitude. In other words, the output power 16 of the CW laser is periodically varied by at least 10% (modulation amplitude). The output power 16 of the CW laser is thus changed by the modulation amplitude or the variation amplitude 18 at regular intervals of a maximum of 20 ps (since the modulation frequency or variation frequency is at least 50 kHz). In the example shown, the output power 16 is reduced by the variation amplitude 18 at intervals of a maximum of 20 ps and increased again to the value of the output power 16. In this case, the variation amplitude is greater than 10% and less than 100% of the output power 16.

[0054] The rise time 20 is the time required to increase the power 28 of the CW laser from a minimum value to a maximum value (in this case, the value of the output power 16). Similarly, the fall time 22 is the time required to reduce the power 28 of the CW laser from the maximum value to the minimum value. In this case, the rise time 20 and the fall time 22 each amount to a maximum of 10 ps.

[0055] A method for processing, in particular laser welding, at least one workpiece 12 is described below with reference to Figures 1 and 2. The method comprises the following steps: Providing the workpiece 12. The workpiece 12 can be made of metal, in particular aluminum and / or copper. The workpiece 12 can have a viscosity of a maximum of 5 mPa*s in the molten state.

[0056] Generating and focusing at least one laser beam 14 with an output power 16 onto the workpiece 12.

[0057] Varying, in particular pulsing or modulating, the laser beam 14 with a variation frequency of at least 50 kHz, a variation amplitude 18 of at least 10% of the output power 16 and a rise time 20 and / or a fall time 22 of the variation amplitude 18 of a maximum of 10 ps.

[0058] The method may comprise the step of:

[0059] Moving the laser beam 14 and / or the workpiece 12 to generate a feed of the laser beam 14 focused on the workpiece 12.

[0060] The method may further comprise the step of:

[0061] Determining the position of the laser beam 14 and / or the workpiece 12. This can be implemented using an optical sensor 26.

[0062] To carry out the method, a laser device 10 according to the above embodiments, in particular the laser device 10 shown in Figure 1, can be used.

Claims

Patent claims 1. Laser device (10) for processing, in particular laser welding, at least one workpiece (12) by means of at least one laser beam (14), wherein the laser device (10) is configured to generate the laser beam (14) with an output power (16), to focus it on the workpiece (12) and to vary the output power (16) of the laser beam (14) with a variation frequency of at least 50 kHz and a variation amplitude (18) of at least 10% of the output power (16), wherein the laser device (10) is configured such that a rise time (20) and / or a fall time (22) of the variation amplitude (18) is a maximum of 10 ps.

2. Laser device (10) according to claim 1, characterized in that the laser device (10) for generating the laser beam (14) comprises a CW laser, wherein the laser device (10) is set up such that the laser beam (14) is modulated with a modulation frequency and a modulation amplitude, wherein the modulation frequency corresponds to the variation frequency and the modulation amplitude corresponds to the variation amplitude (18), in particular wherein the CW laser has an average power of at least 0.2 kW, preferably at least 4 kW.

3. Laser device (10) according to claim 1 or 2, characterized in that the laser device (10) is designed such that the laser beam (14) generates a laser spot on the workpiece (12), wherein the Laser spot has a, in particular circular, core region and a, in particular annular, ring region, wherein an average laser power density in the core region is higher than an average laser power density in the ring region.

4. Laser device (10) according to the preceding claim, characterized in that the laser device (10) for generating the laser beam (14) and / or the laser spot comprises a fiber with a core region and a ring region.

5. Laser device (10) according to one of the preceding claims, characterized in that the laser device (10) is configured such that at least two, in particular at least four, laser beams (14) are generated and focused onto the workpiece (12), in particular wherein all laser beams (14) are each identically designed.

6. Laser device (10) according to one of the preceding claims, characterized in that the laser device (10) comprises a scanner optics (24) for moving the laser beam (14) over the workpiece (12), in particular wherein the scanner optics (24) has an imaging ratio in a range of 1:1 to 5:1, preferably of 1.9:1 or 3.4:

1.

7. Laser device (10) according to one of the preceding claims, characterized in that the laser device (10) comprises an optical sensor (26) for detecting the position of the laser beam (14) and / or the workpiece (12).

8. Method for processing, in particular laser welding, at least one workpiece (12) comprising the steps: Providing the workpiece (12), in particular wherein the workpiece (12) is made of metal, preferably aluminum and / or copper, and has a viscosity of at most 5 mPa*s in the molten state; Generating and focusing at least one laser beam (14) with an output power (16) onto the workpiece (12); Varying, in particular pulsing or modulating, the laser beam (14) with a variation frequency of at least 50 kHz, a variation amplitude (18) of at least 10% of the output power (16) and a rise time (20) and / or a fall time (22) of the variation amplitude (18) of at most 10 ps.

9. The method according to claim 8, characterized in that the method comprises the step: Moving the laser beam (14) and / or the workpiece (12) to generate a feed of the laser beam (14) focused on the workpiece (12).

10. The method according to claim 8 or 9, characterized in that the method comprises the step: Determining a position of the laser beam (14) and / or the workpiece (12), in particular by means of an optical sensor (26) and Possible readjustment of a processing position of the laser beam (14) and / or the workpiece (12).

11. Method according to one of claims 8 to 10, characterized in that for carrying out the method a laser device (10) according to one of claims 1 to 7 is used.

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