Laser optical unit

Abstract

The invention relates to a beam deflection device for a laser welding device or laser device for guiding or deflecting a laser beam (L) and for generating a laser contour or laser line (S) on or in a material (W) by means of the guided laser beam (L), comprising a rotatable optical unit assembly (4a, 4b), which is directly downstream of a collimator (3) or a laser incoupling element in the beam direction of the laser beam (L), with the result that a laser light emerging from the collimator (3) or laser incoupling element can be directly incident on the rotatable optical unit assembly (4a, 4b), wherein the rotatable optical unit assembly (4a, 4b) makes it possible to position the laser beam (L) on the material (W) variably relative to the position of the beam deflection device.

Description

[0001] Laser optics

[0002] The invention relates to a laser optics system or beam deflection device, preferably for a laser welding device, in particular a device for guiding or deflecting a laser beam from a laser light source or a laser or welding laser, for example, for controlling the laser position on or in a material or for generating a laser contour or laser line or a laser pattern on or in a material. Furthermore, the invention relates to a laser welding device or laser device with a laser and such laser optics, as well as a method for generating a laser pattern on or in a material using the beam deflection device, and a program for this purpose.

[0003] In general, the invention lies in the field of laser beam welding, or laser welding, in which the energy is supplied via a laser. Laser beam welding processes are used, for example, to weld components that must be joined at high welding speeds, with a narrow and slender weld seam shape, and with low thermal distortion. The laser beam welding process is generally carried out without any filler material. One advantage of laser beam welding is the comparatively large working distance; for example, a welding process can be carried out at a distance of up to 500 mm from the component, allowing welding to be carried out even in hard-to-reach places. To process a workpiece with a laser beam, a high intensity is required. This intensity is characterized by the focal point and the processing speed.The smaller the focal point and the processing speed, the higher the intensity. The focal point is positioned using laser optics or a beam deflection device and changes during welding. This means that the laser optics or beam deflection device guides or directs the laser beam to the desired working point, usually in combination with a movable and controllable robot arm to which the beam deflection device is attached.

[0004] Generally, two types of laser welding are distinguished. Conduction welding is performed at intensities below 10 W / cm^2. This merely melts the workpiece surfaces or edges. In deep welding (intensities greater than 10^ W / cm^2), a plasma is created by the vaporization of the material being processed. The resulting plasma absorbs significantly more energy because less laser radiation is reflected. This allows the laser beam to penetrate deeper into the material, for example, to weld two sheet metal parts together. At high beam intensities in the focus, such as with steel materials, approximately 1 to 4 MW / cm^2 2 Depending on the travel speed, for example 0.5 to 2 m / min, a vapor capillary can also form in the melt in the direction of the jet.

[0005] The workpiece surface of the butt edge, i.e. the joint of the components to be welded, should be located in the immediate vicinity of the focus of the laser optics in the so-called focal spot. The position of the focus relative to the workpiece surface is therefore an important welding parameter and must therefore be controlled, for example using the laser optics, and also determines the welding depth. The focal spot typically has a diameter of a few tenths of a millimeter, which can result in very high energy concentrations if the laser used has the typical power of several kilowatts. The absorption of the laser power causes a rapid temperature rise on the workpiece surface above the melting temperature of metal, so that a melt forms. The subsequent cooling of the weld seam makes it very hard, depending on the material, and usually causes it to lose toughness.

[0006] The laser beam can be generated by a commercially available laser generator with, for example, 1 to 10 kilowatts of laser power as the laser beam source and guided from the laser beam source to the laser optics via a light guide, such as an optical fiber or glass fiber. Depending on the application, the laser generator can have a continuous wave or pulsed wave output.

[0007] The laser radiation can be focused using a preferably controllable laser optics, whereby dynamic laser beam guidance through the laser optics can be achieved using so-called scanner optics, i.e. a controllable beam deflection. This allows for more dynamic and precise beam positioning compared to pure focusing optics, which enables high process speeds. The position guidance or movement of the laser beam can also be carried out to follow specific contours with the aid of or by means of an industrial or gantry robot to which the controllable laser optics is attached or fastened. The position guidance or movement of the laser beam, in particular the focusing of the laser beam orThe position of the focal spot, in this case, is determined by two factors: the spatial position and alignment of the laser optics, controlled by the industrial robot, and the laser beam guidance within the laser optics, for example, using the scanner optics. Both elements, i.e., the robot and the laser optics, must then be operated in a coordinated manner and can be controlled, for example, by a computer-assisted control system, which must also know the position of the workpiece to be welded or the welding point in order to focus and position the laser beam or focal spot or focus at the desired location on the workpiece.

[0008] It is known to achieve laser beam guidance using two mirrors positioned on rotation axes offset by 90° to each other. Due to the offset arrangement, one mirror is responsible for determining the position of the laser beam on the working plane in the x-direction, and the other mirror is responsible for the y-position.

[0009] DE 10 2014 012 453 A1 discloses an optical beam guidance unit for a laser drilling process, which can be driven in rotation about an optical axis. To adjust the beam offset, a plane-parallel plate is provided, which can be rotated about an axis that forms an acute angle with both the optical axis and the normal of the plane surfaces. By rotating the plane-parallel plate about the tilted axis, the angle of inclination of the plane surfaces to the optical axis can be varied. To adjust the beam inclination, two wedge prisms are provided, which are mounted so as to be rotatable relative to each other about the optical axis.

[0010] Another device for drilling using a laser beam is known from DE 10 2005 047 328 B3.

[0011] DE 10 2020 113 693 A1 discloses a laser device for treating a cornea, comprising a mirror element for spatially displacing a laser beam and rotating dispersive optical elements for generating a rotation pattern. EP 3 460 523 A1 discloses a method for correcting a distance measurement value of a laser scanner.

[0012] It is an object of the present invention to propose an improved laser optics and an improved laser welding process.

[0013] This object is achieved by the subject matter of the independent claims. Advantageous embodiments emerge from the dependent claims.

[0014] A beam deflection device for a laser welding device or laser device for guiding or deflecting a laser beam or for generating a laser contour or laser line or a laser pattern formed by the temporal sequence of the positions of the laser beam or focal spot or.Focus, on or in a material to be welded by means of the guided laser beam has a rotatable optical arrangement which is arranged in the laser beam direction, i.e. in the path direction of the laser beam, directly, i.e. without further optical elements in between, behind a laser entry point in the beam deflection device, for example behind a laser coupling or behind a collimator, so that a laser light coming from the laser entry point, for example the laser light exiting the collimator, can strike the rotatable optical arrangement directly and without redirection or deflection, i.e. also without a deflection mirror, wherein by means of the rotatable optical arrangement a deflection or positioning of the preferably focused laser beam on the material is possible that can be changed relative to the position of the beam deflection device, i.e. for example dynamically. The laser contour or laser line generated on the material can then, for example, form the weld seam.The rotatable optical arrangement is preferably the only deflection arrangement of the beam deflection device, with which the direction of the laser beam emerging from the beam deflection device can be controlled or influenced. For example, the direction or deflection of the laser beam impinging on the rotatable optical arrangement can be adjusted or modified by an adjustable angle depending on the rotational position of the rotatable optical arrangement.

[0015] The deflection or deflection of the laser beam by means of the rotatable optical arrangement serves to preferably continuously guide or position a laser beam to create a laser contour or laser line or weld seam on or in the material to be welded and is not intended to create a recurring rotation pattern, such as with a drill.

[0016] The inventive design of a beam deflection device for a laser device in a laser optics system enables a compact system design, i.e., a compact construction, and in particular, a reduction in the size of the scanner optics. Since additional beam deflection units, in particular reflective elements such as mirrors, are dispensed with, the beam deflection device can be simply installed in a direct line, i.e., one above the other. It is also insensitive to temperature changes and exhibits high thermal stability, since an increase in the temperature of prisms leads to smaller optical deviations compared to scanner optics consisting of mirrors. This also allows for a low overall weight, for example, through a compact aluminum construction. The beam deflection device is therefore well suited for continuous welding operations.

[0017] According to the invention, the rotatable optical assembly is the sole laser deflection or laser positioning unit of the optical beam deflection device, which can be controlled for variable or variable guidance of the laser beam to generate a laser contour, laser line, or weld seam. As mentioned, a movable robot arm can also be used, which can also influence the position of the laser beam or the focal point on the material or the object(s) to be welded if the beam deflection device is attached to it.

[0018] According to one embodiment, the rotatable optical arrangement is realized by rotating dispersive optical elements, such as wedge prisms, i.e., a Risley prism arrangement, wherein at least two cylindrical wedge prisms are arranged one above the other on a rotation axis. Optionally, a third prism or additional prisms can be integrated to increase the dynamics of beam positioning. A laser beam incident on the rotation axis or parallel to the rotation axis is deflected by the one-sided bevel of the wedge prisms. The rotational position, i.e., the controlled rotational position, of the two wedge prisms can create a circular deflection area. This means that, depending on the rotational position of the wedge prisms, an incoming laser beam can be deflected to a location within the deflection area or on the circular deflection area.To align the wedge prisms to a specific point on the work area, for example, Cartesian coordinates on the work area or workpiece are converted into the required angles of rotation of the two wedge prisms.

[0019] The rotating, dispersive optical element or Risley prism pair can be rigidly fixed to each other and have a relative angle of, for example, 180 degrees. The Risley prisms are preferably arranged at a fixed distance from each other in a beam path of the laser beam or along the optical axis. The respective Risley prisms can be designed such that they are rotationally fixed or secured against rotation relative to each other, for example, they are always rotated or turned at the same angle.

[0020] Alternatively, it can be provided that the distance between the Risley prisms in the beam path of the laser device is adjustable and / or that the respective Risley prisms can be rotated or controlled in such a way that the relative angle between the prisms is variable, i.e., not constant.

[0021] The rotatable optics assembly can be mounted in the beam deflection device so that its rotational axis is parallel to the direction of laser light entering the beam deflection device or parallel to the laser beam direction after the collimator. The rotational position can be changed or adjusted, for example, using an electric motor, such as a hollow-shaft motor. This allows for a direct and compact connection of the beam deflection device within the motor(s).

[0022] The beam deflection device can be designed so that only the angle of rotation of the rotatable optical arrangement influences the position or focal point of the laser beam on the material, thus generating the laser contour, laser line, or weld seam in a temporal sequence of the focal points. Thus, the beam deflection device can be controlled, for example, exclusively by specifying the temporal sequence of rotation angles.

[0023] The beam deflection device preferably comprises a coupling element or an optical fiber for coupling the laser light and / or a collimator, which is arranged downstream of the coupling element and upstream of the rotatable optical arrangement in the laser beam direction. Thus, the laser light, which is generated, for example, by an external laser light source and supplied via a fiber optic cable, can be coupled into the beam deflection device and rectified before it strikes the rotatable optical arrangement, from where it is deflected in a controlled manner to the desired focal point on the material.

[0024] According to an alternative embodiment, which can also be configured as described above, a beam deflection device for a laser device for guiding or deflecting a laser beam and for generating a laser contour or laser line on or in a material using the guided laser beam comprises a rotatable optical assembly rotatably mounted in a hollow shaft motor for rotating the rotatable optical assembly. The hollow shaft motor can be a brushless motor or a torque motor.

[0025] The rotatable optical arrangement can be connected to the rotatable hollow shaft of the hollow shaft motor in a rotationally secure manner and / or no gear can be provided between the rotatable optical arrangement and the hollow shaft of the hollow shaft motor, so that a rotational movement of the hollow shaft is equal to the rotational movement of the rotatable optical arrangement.

[0026] Optionally, a rotation sensor can be provided for determining the rotational position or angular position of the hollow shaft or the rotatable optical arrangement, which can be designed, for example, as a magnetic encoder disk which is connected in a rotationally fixed manner to the hollow shaft and whose coding can be detected by a sensor or incremental signal generator in order to determine the current rotational position or the rotational angle.

[0027] According to a further aspect, the invention relates to a laser device comprising a laser light source and a beam deflection device as described above.

[0028] The laser light source can be a high-power laser or a laser with a high spectral energy density for welding or ablating material, in particular a laser with a power greater than 1 kW, for example from 1 to 10 kW, preferably between 4 and 8 kW. The high-power laser should preferably have or be able to generate an energy density sufficient for welding or ablating material. The wedge prisms can be made of quartz glass, for example a high-purity non-crystalline silicate glass that is specially coated for a high-power laser or a laser with a high spectral energy density in order to reduce thermal influences within the optical structure. For example, the wedge prisms can consist practically only of silicon and oxygen (silicon dioxide), which is also referred to as synthetic fused silica.

[0029] Optionally, the laser device can have a movable and / or controllable robot arm to which the beam deflection device is or can be attached. To control the laser device and in particular to position the laser focal point, two control signals are then generally required: a first control signal for positioning the beam deflection device using the robot arm and a second control signal for beam deflection within the beam deflection device, for example, for adjusting the rotational position of the rotatable optical arrangement.

[0030] A method for generating a laser focus line or weld seam on or in a material, in particular for welding the material, by means of a beam deflection device or a laser device as described above, comprises the following steps: a laser beam is coupled into the beam deflection device; the laser beam strikes the rotatable optical arrangement as the laser positioning unit directly, in particular without intermediate optical elements, and is deflected by this rotatable optical arrangement depending on the rotational position of the optical arrangement or is focused onto the material relative to the position of the beam deflection device in order to generate the laser focus line or weld seam there.

[0031] In this process, the laser beam is preferably guided in such a way that it does not experience any axial offset and only a tilt, so that mirror elements can be dispensed with.

[0032] According to a further aspect, the invention relates to a computer program with instructions which, when the program is executed by a computer, cause the beam deflection device to be controlled according to one of the claims; and / or a computer-readable storage medium on which the program is stored; and / or a computer with at least one processor and the program storage medium, wherein the processor executes or can execute the program; and / or a data carrier signal which carries the program; and / or a data stream with the program.

[0033] The invention is described below using an exemplary embodiment. Figure 1 shows a schematic representation of a laser welding arrangement;

[0034] Fig. 2 is a perspective view of a laser beam deflection device (laser scanner);

[0035] Fig. 3 is a cross-sectional view of the laser beam deflection device shown in Fig. 2;

[0036] Fig. 4 is a perspective sectional view of a torque motor assembly;

[0037] Fig. 5 is a cross-sectional view of the prism holder (embodiment 1); and Fig. 6 is a cross-sectional view of the prism holder (embodiment 2);

[0038] Fig. 1 shows a laser device with a laser generator 1 as the laser light source, which feeds a laser beam into an optical fiber 2, which directs it (shown schematically) to a rotatable optical arrangement, which in the embodiment shown is formed by two rotatable prisms 4a and 4b. The prism 4a, located at the top in Figure 1, is mounted in the hollow shaft motor 6a and can be rotated by it. The prism 4b, located at the bottom in Figure 1, is mounted in the hollow shaft motor 6b and can also be rotated by it.

[0039] Control electronics 7 are connected to the hollow shaft motor 6a via a control connection 8a, to the hollow shaft motor 6b via a control connection 8b, and to the laser generator 1 via a control connection 8c. The control electronics 7 receives control signals from a control computer 9 or an industrial controller via a corresponding control connection, for example 8d, in order to control the laser generator 1 and the hollow shaft motors 6a and 6b such that the shown laser contour or laser line can be traced on a workpiece W, for example as a weld seam S. The control connections 8a, 8b, 8c, and 8d can be known electrical cables or radio connections. Control electronics 7 integrated into the laser optics enables so-called "stand-alone" operation, so that this laser optics can, in principle, be connected to any external laser source 1.

[0040] For example, a user can enter the desired course of the laser contour, laser line, or weld seam S to be generated on the workpiece W into a control computer 9, which is then transmitted to the control electronics 7 and automatically implemented by it. In particular, the motors 6a and 6b are controlled such that the prisms 4a and 4b mounted therein are rotated such that the laser contour or laser line S, which represents a series of many laser focus points, is generated on the workpiece W. Fig. 2 shows a perspective view of a laser beam deflection device or laser scanner, which has a collimator 3 on its upper side, which can be connected to the optical fiber 2 shown in Figure 1, so that the laser beam is coupled into the laser beam deflection device. The laser beam deflection device has a robot connection 10, by means of which it can be attached to a robot arm (not shown).

[0041] Fig. 3 shows a sectional view of the laser beam deflection device or laser scanner from Fig. 2. The fiber optic cable or fiber optic guide 2, which comes from the laser beam source 1, can be mounted above the collimator 3. The collimator 3 parallels the incoming laser beam L and directs it onto the wedge prism 4a below it, so that it can be deflected by the rotatable wedge prisms 4a and 4b. Below the collimator 3 is a cooling plate that can be flushed with cooling water during operation. Each wedge prism 4a or 4b, together with a torque motor 6a or 6b, forms a self-contained assembly. The two wedge prisms 4a and 4b are positioned so that the flat sides of the wedge prisms 4a or 4b are directly opposite each other.

[0042] At the lower end of the laser scanner is the F-theta lens 5, which focuses the deflected laser beam L onto a flat work surface, such as the workpiece W shown in Fig. 1. In Fig. 3, the control unit of the laser scanner 7 is installed to the right of the beam deflection device. From this unit, the control commands are sent to the torque motors 6a and 6b to trace the desired contours S.

[0043] To allow the laser scanner to be connected to an industrial robot, a robot connection 10 is mounted on the far right. This can be designed as a quick-change plate and enables quick assembly and disassembly of the laser scanner.

[0044] Beam deflection is therefore realized exclusively by the torque motor assembly. This assembly is installed twice in the laser scanner, with these assemblies arranged so that the distance between the wedge prisms 4a and 4b is as small or minimal as possible.

[0045] The assembly consists, as shown in Fig. 4, of the actual torque motor 6 with the internal rotor, an encoder 11 with encoder disk 12, a ball bearing support, and a cover for securing the components in the housing. The encoder 11 and encoder disk 12 are required to detect the actual position of the torque motor 6, which is possible, for example, with an accuracy of 1 / 100 of a degree. This enables control of the motor 6. A ball bearing is installed in the upper and lower sections, which accommodates the hollow shaft inside. The prism mount is integrated into this in the lower section. Spacer sleeves 13 ensure correct positioning of the hollow shaft together with the rotor in relation to the torque motor 6.

[0046] Fig. 5 shows a detailed view of the prism mount (Example 1). The wedge mount 14 in the upper part is secured against rotation by means of a dowel pin. It has the same wedge angle as the prism 4. An O-ring 15a is located between the prism 4 and the mount 14. A second O-ring 15b is installed below the wedge prism 4. The prism 4 is secured using the counter-pressure piece 16, which has an external thread. The two O-rings 15a and 15b compensate for manufacturing tolerances and reduce the stresses in the wedge prism 4 that occur due to temperature changes.

[0047] Fig. 6 shows a detailed view of the prism mount (Example 2). The wedge mount 14 and the prism 4 have the same wedge angle. They both also have a groove into which a dowel pin 18 is inserted to secure the individual parts against rotation. The prism 4 is secured using the counter-pressure piece 16, which has an external thread. A flat seal 18 is installed between the prism 4 and the counter-pressure piece 16. This compensates for manufacturing tolerances and reduces the stresses that occur in the wedge prism 4 due to temperature changes.

[0048] List of reference symbols:

[0049] 1 laser generator

[0050] 2 optical fibers

[0051] 3 Collimator

[0052] 4 rotatable optics arrangement

[0053] 4a (wedge) prism 4b (wedge) prism

[0054] 5 F-Theta lens 6a Motor

[0055] 6b engine

[0056] 7 Control electronics 8a, 8b, 8c and 8d control connections

[0057] 9 control computers

[0058] 10 Robot connection

[0059] 11 Encoder 12 Encoder disk

[0060] 13 spacer sleeves

[0061] 14 Wedge holder

[0062] 15a O-ring

[0063] 15b O-ring 16 Counter pressure piece

[0064] 17 Flat gasket

[0065] 18 Dowel pin

[0066] S Laser contour or laser line, weld seam

[0067] W Workpiece, material L Laser beam

Claims

Patent claims 1. Beam deflection device for a laser welding device or laser device for guiding or deflecting a laser beam (L) and for generating a laser contour or laser line (S) on or in a material (W) by means of the guided laser beam (L), with a rotatable optical arrangement (4a, 4b) which is arranged in the beam direction of the laser beam (L) directly behind a collimator (3) or a laser coupling element, so that a laser light emerging from the collimator (3) or laser coupling element can strike the rotatable optical arrangement (4a, 4b) directly, wherein by means of the rotatable optical arrangement (4a, 4b) a variable positioning of the laser beam (L) on the material (W) relative to the position of the beam deflection device is possible.

2. Beam deflection device for a laser device according to the preceding claim, wherein the deflection or the deflection angle of the laser beam (L) can be adjusted by the rotational position of the rotatable optical arrangement (4a, 4b).

3. Beam deflection device for a laser device according to one of the preceding claims, wherein the rotatable optical arrangement (4a, 4b) is the only laser beam deflection unit or the only laser positioning unit of the beam deflection device.

4. Beam deflection device for a laser device according to one of the preceding claims, wherein the rotatable optical arrangement (4a, 4b) is formed by rotating wedge prisms or a Risley prism arrangement.

5. Beam deflection device for a laser device according to one of the preceding Claims, wherein the rotatable optical arrangement (4a, 4b) in the Beam deflection device is rotatably mounted such that the axis of rotation of the rotatable optical arrangement (4a, 4b) is parallel to the laser beam entry direction of the laser light (L) into the beam deflection device or parallel to the laser beam direction after the collimator (3).

6. Beam deflection device for a laser device according to one of the preceding claims, wherein the beam deflection device is designed such that only the The angle of rotation of the rotatable optical arrangement (4a, 4b) influences the position or focus point of the laser beam (L) on the material (W).

7. Beam deflection device for a laser device according to one of the preceding claims with a coupling element or an optical fiber for coupling the laser light and a collimator (3) which is arranged in the laser beam direction after the coupling element and before the rotatable optical arrangement (4a, 4b).

8. Beam deflection device for a laser device for guiding or deflecting a laser beam (L) and for generating a laser contour or laser line (S) on or in a material (W) by means of the guided laser beam (S), with a rotatable optical arrangement (4a, 4b) which is rotatably arranged in at least one hollow shaft motor (6a, 6b) for rotating the rotatable optical arrangement (4a, 4b), wherein the beam deflection device can be designed according to one of the preceding claims.

9. Beam deflection device for a laser device according to the preceding claim, wherein the rotatable optical arrangement (4a, 4b) consists of two optical elements or wedge prisms, wherein the first optical element or wedge prism (4a) is connected in a rotationally secure manner to a rotatable hollow shaft of a first hollow shaft motor (6a), the second optical element or wedge prism (4b) is connected in a rotationally secure manner to a rotatable hollow shaft of a second hollow shaft motor (6b) and / or wherein no gear is provided between a rotatable optical arrangement and a hollow shaft of a hollow shaft motor, so that a rotational movement of a hollow shaft is equal to the rotational movement of the rotatable optical arrangement (4a, 4b) mounted therein.

10. Beam deflection device for a laser device according to one of the two preceding claims with a rotation sensor for determining the rotational position or angular position of the hollow shaft or the rotatable optical arrangement (4a, 4b), which can be designed as a magnetic encoder disk (12) which is connected in a rotationally fixed manner to the hollow shaft, and a sensor or incremental signal generator.

11. Laser device with a laser light source (1) and a beam deflection device according to one of the preceding claims.

12. Laser device according to the preceding claim, wherein the laser light source (1) is a high-power laser or laser with high spectral energy density for welding or ablating material, in particular with a power of 1 to 10 kW.

13. Laser device according to one of the two preceding claims with a movable and / or controllable robot arm to which the beam deflection device is or can be attached.

14. Method for generating a laser focus line (S) on or in a material (W), in particular for welding the material, by means of a beam deflection device according to one of claims 1 to 10 or a laser device according to one of the three preceding claims, wherein a laser beam (L) is coupled into the beam deflection device, the laser beam (L) strikes the rotatable optical arrangement (4a, 4b) as a laser positioning unit directly, in particular without intermediate optical elements, and is deflected by this rotatable optical arrangement (4a, 4b) depending on the rotational position of the optical arrangement (4a, 4b) or is directed onto the material (W) in a focused manner relative to the position of the beam deflection device.

15. Method according to the preceding claim, wherein the laser beam (L) is directed such that it experiences no axial offset and only a tilt.

16. A computer program with instructions which, when executed by a computer, cause the beam deflection device to be controlled according to one of claims 14 or 15; and / or a computer-readable storage medium on which the program is stored; and / or a computer with at least one processor (7) and the program storage medium, wherein the processor executes or can execute the program; and / or a data carrier signal carrying the program; and / or a data stream with the program.

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