Device for shaping a laser beam for material processing

Abstract

Device (1) for shaping a laser beam for material processing with a laser light source providing a raw beam (2) and at least one mirror (3, 4, 5), wherein a mirror (6) that can be changed in its shape and / or position directs the raw beam (2) at least partially as a processing beam (8) and that several rigidly arranged non-adjustable deflecting mirrors (3, 4, 5) are provided which divide the raw beam (2), wherein the adjustable mirror (6) recombines the divided raw beam (2) to form the processing beam (8), characterized by the fact that the variable mirror (6) is designed as an inflatable rotationally symmetric mirror body, which is designed as a cone depending on the pressure, or whose surface has a concave curvature inwards. and that the curvature is formed as a parabolic curvature wherein the control range for the variable mirror (6) lies between a concave curvature as the initial state and the cone as the final state.

Description

[0001] The invention relates to a device for shaping a laser beam for material processing according to the type defined in more detail in the preamble of claim 1.

[0002] Some laser material processing processes require a constant angle of incidence on the component surface. However, if the contour of the component is not uniform, this can become correspondingly complex to control. Since, according to the current state of the art, scanner optics, such as those used in laser welding, are typically used for such processing processes, a raw beam with a constant beam profile is deflected and can thus be positioned in position and angle using the scanner optics. However, it is disadvantageous if a complete reorientation of the beam in all spatial directions is necessary. For example, during cleaning processes, inaccuracies in the positioning of the laser beam can lead to overlaps in the individual paths. This then leads to an inhomogeneously processed surface, which is a serious disadvantage.

[0003] Scanner optics are known from the prior art, particularly for welding. DE 10 2020 121 283 A1 describes a method for processing a workpiece with a laser beam. The workpiece itself has a curved surface. The laser beam is adapted to this surface using a correspondingly complex optics system.

[0004] DE 11 2013 006 559 T5 discloses a laser processing device for forming a modified region in an object to be processed by irradiating the object with laser light. The laser processing device comprises a laser light source that emits the laser light L, a support table on which the object rests, and an optical system that converges a ring portion surrounding a central portion including an optical axis of the laser light in the laser light emitted from the laser light source onto a predetermined portion of the object resting on the support table. The optical system adjusts a shape of an inner and / or outer edge of the ring portion of the laser light according to a position of the predetermined portion in the object.

[0005] Korean patent application KR 10 2023 0 058 673 A discloses a device for laser sealing, which also discloses a device for shaping a laser beam. An incident laser beam is split by a plurality of mirrors and, after being combined, focused onto a workpiece as a processing beam. Both the focus position and the aperture angle of the focused annular beam depend on the shape of the reflecting surfaces. Furthermore, the document discloses a variety of different mirror shapes, but does not detail how these different mirror shapes are implemented in the device.

[0006] The American patent application US 2022 / 0137394 A1 discloses an advantageous device for controlling the mirror shape of a rotationally symmetrical mirror body for generating a ring beam by means of a conical mirror, with which a ring beam is inevitably produced.

[0007] DE 10 2020 205 948 A1 discloses a method for laser cutting a workpiece with a thickness of less than 6 mm, wherein a first laser beam, a second laser beam and a gas jet are directed onto an entrance surface of the workpiece, wherein the laser beams at least partially overlap one another on the workpiece, wherein the first laser beam has a smaller focus diameter than the second laser beam, wherein the beam parameter product of the first laser beam is at most 5 mm*mrad, wherein a power proportion of the second laser beam in the total laser power is less than 20%, and wherein a cutting gap with a broken cutting edge is formed on the entrance surface of the workpiece.The invention further relates to a laser cutting system for laser cutting a sheet-metal workpiece along a cutting line, comprising a laser light source device for superimposing a first laser beam and a second laser beam in a cutting zone, wherein the first laser beam has a smaller focus diameter than the second laser beam, wherein the beam parameter product of the first laser beam is at most 5 mm*mrad, and wherein a power proportion of the second laser beam in the total laser power is less than 20%, a nozzle for directing a gas jet onto the cutting zone, and a movement device for moving the cutting zone along the cutting line relative to the workpiece.

[0008] DE 10 2019 108 681 A1 discloses a device and a method for generating a multiple spot during laser material processing. According to the present invention, the power distribution is selected by inserting at least one first mirror into the laser beam. The light beam always falls on only one side of the mirror, allowing for simple and cost-effective manufacturing.

[0009] The object of the invention is to provide an improved device for shaping a laser beam for material processing, which enables homogeneous processing conditions with a constant angle of incidence even with complex component surfaces.

[0010] According to the invention, this object is achieved by a device having the features in claim 1.

[0011] The device according to the invention for shaping a laser beam comprises at least one mirror, similar to conventional scanner optics. This or an additional mirror can be changed in terms of its shape and / or position, and then redirects the raw beam received from a laser light source as a processing beam.

[0012] By changing the position and / or the surface of the mirror during processing, it is possible to actively adjust the processing beam in order to generate the desired parameters during laser processing, in particular without having to move the actual device in a complex manner, which can always lead to inaccuracies with regard to the positioning of this device.

[0013] According to the invention, rigidly arranged, non-adjustable deflecting mirrors are provided, which split the raw beam, with the adjustable mirror recombining the split raw beam into the processing beam. This ensures that the laser beam is always split uniformly via the deflecting mirrors before the laser beam, split into several partial beams, is combined into the processing beam via the adjustable mirror. The ability of the adjustable mirror to change its surface and / or position makes it possible to adapt the processing beam to the desired processing process and the specified surface contour of the component to be processed, in particular without the device itself having to be moved.

[0014] According to the invention, the adjustable mirror can be designed as an inflatable, rotationally symmetrical mirror body, which, depending on the pressure, is shaped as a cone or whose surfaces have a concave inward curvature, and the curvature is parabolic, with the control range being formed between the concave curvature as the starting point and the conical shape as the end point. The surface of the mirror can thus be curved inward, in particular parabolically, or straight. This allows the focus, orientation, and diameter of the processing beam to be influenced accordingly.

[0015] The adjustable mirror can therefore be realized, in particular, as a rotationally symmetrical structure, which in one state is formed as a cone. Preferably, the rotational axis of the cone coincides with the center of the processing beam, which is formed as a ring beam, so that the adjustable mirror sits centrally in the processing beam it recombines.

[0016] Further advantageous embodiments of the device and method according to the invention also emerge from the exemplary embodiments which are illustrated in more detail below with reference to the figures.

[0017] Showing: Fig. 1 is a schematic representation of a possible structure of a device according to the invention; Fig. 2 a representation of the variable mirror in an initial state; Fig. 3 a representation of the variable mirror in a final state; Fig. 4 a beam profile of the machining beam according to the intersection line AA and BB in Fig. 1; Fig. 5 an exemplary application for laser cleaning of hollow bodies using active beam shaping; Fig. 6 an exemplary application for laser cleaning of components with non-constant surfaces using active beam shaping; Fig. 7 a representation analogous to that in Fig. 5 with an adjustment of the processing beam in the height direction.

[0018] In the presentation of the Fig. 1 shows a device 1 for shaping a laser beam for material processing. From a laser source (not shown here), a raw beam designated 2 enters the device 1. The raw beam is split by several rigidly arranged deflecting mirrors 3 and 4 and guided further as a ring beam. This ring beam is then directed back to the center of the device 1 via two further rigid deflecting mirrors 5 and recombined there by a variable mirror 6. The laser beam, from then on referred to as the processing beam 8, is focused via a focusing lens 7 and, if necessary, coupled out of the device 1 via an optional, not shown wedge plate for adjusting the intensity of the processing beam 8. The processing beam 8 can then be directed onto the component to be processed. In the illustration of the Fig. 1, the processing beam 8 is shown only up to its focal point designated F.

[0019] The processing beam 8 is designed as a ring beam and has, for example, in the areas marked AA and BB, the Fig. 4 shown cross sections.

[0020] The crucial component of the device 1 is the adjustable mirror 6, which can be adjusted both in terms of its surface or shape and also in terms of its position. The adjustable mirror 6 is rotationally symmetrical and can be moved along its rotation axis, as indicated by the double arrow marked 9, in this case in a Fig. 1 with Z. The adjustable mirror 6 can now be designed in particular as an inflatable mirror with a parabolic curvature. In the illustration of the Fig. 2, it is shown in its initial state with a parabolic curvature of its surface inwards, i.e. a concave curvature. In the adjacent figure of the Fig. 3, when inflated, it has straight surfaces, thus ultimately forming a cone. Typically, an adjustment range between the conical design on the one hand and the concave parabolic design on the other is sufficient.

[0021] The representation of the Fig. The rotation axis of the variable mirror 6, designated R in Figures 1 to 3, coincides with the center of the processing beam 8. By moving in the Z direction and / or changing the curvature by inflating or deflated with a medium, the processing beam 8, and in particular the position of its focal point F, can be varied during the processing of a component.

[0022] In the presentation of the Fig. Figure 5 shows, purely by way of example, a laser cleaning of a hollow body designated 10 in two different processing states. Without the device 1 having to be moved in the Z direction, an aperture angle above and below the focal point F can be changed solely by actively shaping the processing beam. In the exemplary embodiment shown here, two exemplary angles α1 and α2 are shown, which are designed differently and thus lead to different processed areas of the inner surface of the hollow body 10.

[0023] This concept can now be applied not only to hollow bodies 10, but also analogously to other component surfaces with a non-constant surface profile. In the example of the Fig. Figure 6 shows such a component surface 11 in two processing states. By varying the angle α, which here is α1 on the one hand and α2 on the other, the angle of incidence β of the laser beam on the surface can be kept constant, thus enabling the desired processing to be carried out simply and efficiently. Here, too, the example involves laser cleaning of the corresponding surface.

[0024] Alternatively, the device 1 as a whole or the adjustable mirror 6 could of course also be moved accordingly in its position in the vertical direction Z. Analogous to the illustration in Fig. 5 then results in the representation of the Fig.7. The two angles α1 and a2 are equal here, but the focal point F moves downwards by the distance z1 in the height direction Z, in particular by adjusting the height position of the adjustable mirror 6. In principle, adjusting the entire device in the height direction Z would also be conceivable here; however, with the device described, adjusting the mirror alone is typically the better and simpler option, leading to a very precise positioning result.

Claims

[1] Device (1) for forming a laser beam for material processing with a laser light source supplying a raw beam (2) and at least one mirror (3, 4, 5), wherein a mirror (6) which is variable in shape and / or position transmits the raw beam (2) at least partially as a processing beam (8) and that several rigidly arranged non-changeable deflecting mirrors (3, 4, 5) are provided, which split the raw beam (2), wherein the changeable mirror (6) recombines the split raw beam (2) to form the processing beam (8), characterized by , that the variable mirror (6) is designed as an inflatable, rotationally symmetrical mirror body which, depending on the pressure, is designed as a cone or whose surface has a concave curvature inwards and that the curvature is designed as a parabolic curvature wherein the control range for the variable mirror (6) lies between a concave curvature as the initial state and the cone as the final state.

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