Method for machining metal workpiece and laser device

Abstract

The invention relates to a method in which a machining beam (18) is directed onto a workpiece (W) and moved relative to the workpiece (W) in a cutting direction (24), the machining beam (18) comprising: a first laser beam (20) having a first intensity for cutting the workpiece (W); a second laser beam (22) having a second smaller intensity, which is emitted next to the first laser beam (20) onto the workpiece surface (26) of the workpiece (W), whereby a rounded cutting edge (30) is produced by means of the second laser beam (22); in order to produce a material bridge (36) of the metal workpiece (W), the first intensity of the first laser beam (20) is reduced in a stabilization region (38) of the workpiece (W) compared to at least one cutting region (40) of the workpiece (W) adjoining the stabilization region (38), whereby the workpiece (W) is cut in the stabilization region (38) at most over a partial region of the thickness of the workpiece.

Description

Technical Field

[0001] The invention relates to a method for machining a metal workpiece and to a laser device for machining a metal workpiece by means of a machining beam. Background Art

[0002] WO 2022 / 037797 A1 discloses a method for producing at least one workpiece part and a workpiece remainder from a workpiece by means of a laser beam emitted from a laser processing head. In the method, the workpiece is cut along a cutting line, wherein cutting edges are formed on the workpiece part and the workpiece remainder. In addition, in the method, the workpiece is trimmed in the form of a rounding during the connection of the workpiece part to the workpiece remainder.

[0003] Furthermore, a method for laser cutting of a workpiece is known from DE 10 2019 125 103 A1. In this method, a machining laser beam is generated for rough machining of the workpiece. Here, two energy intensity regions of the machining laser beam are generated, wherein the first energy intensity region for rough machining of the workpiece has a greater time-integrated radiation energy than the second energy intensity region for at least partially fine machining of the cut edge. The workpiece is irradiated with the machining beam. Summary of the invention

[0004] The object of the present invention is to provide a solution which enables particularly rapid and precise cutting of workpieces by means of a laser device, wherein sharp cutting edges are avoided.

[0005] This object is achieved by the subject matter of the independent claims. Other possible embodiments of the invention are described in the dependent claims, the description and the drawings. The features, advantages and possible embodiments explained within the scope of the description of one of the subjects of the independent claims are at least similarly to the features, advantages and possible embodiments of the corresponding subject matter of the other independent claims and any possible combination of the subjects of the independent claims, if necessary in combination with one or more of the dependent claims.

[0006] The present invention relates to a method for processing a metal workpiece, which is particularly plate-shaped or tubular. In this method, it is proposed to direct a processing beam onto the workpiece and move the processing beam relative to the workpiece in a cutting direction. The processing beam is provided by means of a laser device. Directing the processing beam onto the workpiece should be understood as the processing beam being provided by the laser device, directed onto the workpiece and projected onto the workpiece surface of the workpiece. The processing beam includes a first laser beam with a first intensity, which is arranged to cut the workpiece in the thickness direction. In other words, when processing the metal workpiece, the workpiece is cut in the thickness direction of the workpiece by means of the first laser beam. In addition, the processing beam includes a second laser beam projected onto the workpiece surface of the workpiece next to the first laser beam, which has a second intensity that is smaller than the first intensity of the first laser beam. A rounded cutting edge of the workpiece is generated by means of the second laser beam. Therefore, the material of the workpiece can be made to flow by means of the second laser beam, whereby the possible cutting edge generated when the workpiece is cut by means of the first laser beam is rounded. Therefore, the reprocessing cost of the workpiece can be kept particularly low. The machining beam can thus cut the workpiece, wherein a rounded cut edge is produced. Subsequent rounding of the cut edge can thus be omitted.

[0007] Therefore, the processing beam includes a first laser beam and a second laser beam at least partially arranged next to the first laser beam. For example, the first laser beam and the second laser beam can overlap at least partially. It is feasible that the first laser beam and the second laser beam are arranged concentrically relative to each other. This should be understood as the image of the first laser beam on the workpiece surface of the workpiece forming the inner area of ​​the processing beam, and the image of the second laser beam surrounds the image of the first laser beam on the circumference. For this purpose, the image of the first laser beam can be at least substantially circular or elliptical, while the image of the second laser beam is designed annularly, thereby surrounding the image of the first laser beam annularly. In the plane of the workpiece surface, the images of the first laser beam and the second laser beam can be adjacent to each other without overlapping or spaced apart from each other by a small separation gap.

[0008] In addition, it is proposed in the method that in order to produce a material bridge of the metal workpiece, the first intensity of the first laser beam is reduced in the stabilization area of ​​the workpiece extending along the cutting direction compared with at least one cutting area of ​​the workpiece adjacent to the stabilization area along the cutting direction. As a result, the workpiece is cut into at most a partial area of ​​the thickness of the workpiece in the stabilization area. Leaving at least one material bridge when cutting the workpiece makes it possible to achieve: when processing the workpiece, no tilting of the two workpiece parts generated by cutting the workpiece relative to each other occurs, thereby the workpiece can be cut particularly accurately. If the workpiece parts tilt relative to each other uncontrolled during the processing of the metal workpiece, the processing beam may deviate from the preset cutting line of the workpiece, thereby the workpiece is miscut. Such miscutting of the workpiece can be avoided by the at least one material bridge. After the cutting of the metal workpiece by means of the processing beam is completed, the corresponding workpiece parts of the workpiece are held on each other by means of the at least one material bridge. Subsequently, the remaining material bridge of the workpiece is disconnected so that the workpiece parts of the workpiece are separated from each other. At least one of the separated workpiece parts can be a component, which is therefore cut out of the metal workpiece within the scope of the method. The at least one material bridge can be broken by means of a machining beam or mechanically, for example by breaking. The breaking can be achieved, for example, by pressing, knocking or vibrating the first workpiece part, in particular the component, out of the surrounding second workpiece part, so that the second workpiece part is the remaining part of the workpiece or the remaining grid of the workpiece. Alternatively, the material bridge can be broken in that a plurality of workpiece parts held together by the material bridge are bent apart or vibrated apart. The at least one material bridge extends as a so-called "Nano Joint" only over a partial area of ​​the thickness of the workpiece. Compared to so-called micro joints extending over the entire thickness of the workpiece, the use of nano joints as material bridges has the advantage that the entire cutting edge can be provided in a rounded manner.

[0009] The workpiece is cut into in the stabilization region. Thus, a material bridge remains in the stabilization region, which extends only over a portion of the thickness of the workpiece. In the cutting region, the workpiece is completely cut through in its thickness. The cutting region can adjoin the stabilization region forward or backward in the cutting direction. In particular, the workpiece comprises at least two cutting regions, wherein one cutting region adjoins the stabilization region forward in the cutting direction and the other cutting region adjoins the stabilization region backward in the cutting direction. Thus, the stabilization region is bounded forward and backward in the cutting direction by the respective cutting region. In particular, the workpiece can have a stabilization region surrounded by the respective cutting region for each material bridge to be produced.

[0010] In order to cut a metal workpiece with the aid of a machining beam in a single method step and to provide it with a rounded cutting edge, wherein at least one material bridge is generated, the intensity of the first laser beam is changed at least during the guidance on the surface of the workpiece in the cutting direction in order to leave a nanojoint. Thus, the first intensity of the first laser beam has an initial value in the cutting direction in the cutting region, is reduced to a reduced value in the stabilization region adjacent to the cutting direction and is increased to the initial value again in another cutting region adjacent to the stabilization region in the cutting direction. Thus, the machining beam can be continuously guided along the workpiece surface of the workpiece in order to completely cut through the workpiece in the cutting region and leave a material bridge in the stabilization region, wherein a rounded cutting edge of the workpiece is generated. Thus, reprocessing of the workpiece in a plurality of processing steps different from one another can be omitted, for example, cutting the workpiece while leaving at least one material bridge and subsequently rounding the edges individually. Thus, the method enables particularly fast and large-scale processing of metal workpieces.

[0011] In a feasible improvement of the present invention, it is proposed that the first laser beam and the second laser beam are arranged next to each other on a line extending on the workpiece surface perpendicular to the cutting direction. In other words, the machining beam moves relative to the workpiece surface in the cutting direction, whereby these laser beams are guided next to each other on the workpiece surface of the workpiece. Thus, these laser beams are arranged next to each other perpendicular to the cutting direction in a plane extending through the workpiece surface. In particular, the laser beams can be arranged next to each other perpendicular to the cutting direction and perpendicular to the thickness direction of the workpiece, which coincides with the beam direction of the laser beams projecting onto the workpiece. Therefore, the second laser beam is arranged closer to the workpiece part retained when cutting the workpiece than the first laser beam, whereby the cutting edge generated by means of the first laser beam when cutting the workpiece can be rounded by melting recasting and thus by the flow of the material. The cutting edge is rounded by means of the second laser beam, especially at the moment of its generation, whereby the risk of generating a sharp cutting edge can be kept particularly small.

[0012] In another feasible design scheme of the present invention, it is proposed to provide a processing beam by means of a laser device. The laser device includes an optical waveguide, a laser beam generating unit and a beam distribution device. The laser device is in particular a fiber laser. Therefore, the optical waveguide can be a so-called optical fiber, in particular a multi-clad optical fiber, such as a 2-in-1 optical fiber or a 3-in-1 optical fiber. The optical waveguide includes a core region and at least one annular region. If the optical waveguide is configured as a 2-in-1 optical fiber, the optical waveguide includes a core region and an annular region surrounding the core region on the circumferential side. If the optical waveguide is configured as a 3-in-1 optical fiber, the optical waveguide includes a core region and two annular regions, namely an inner annular region and an outer annular region. The inner annular region surrounds the core region on the circumferential side, and the outer annular region surrounds not only the core region but also the inner annular region on the circumferential side. Here, the core region and the two annular regions are arranged concentrically relative to each other. The laser beam generating unit is configured to generate a laser input beam. Therefore, in this method, the laser input beam is generated by means of a laser beam generating unit. The laser input beam is distributed to the core region for generating a first laser beam and to at least one annular region for generating a second laser beam by means of a beam splitting device. By means of the beam splitting device, it can be adjusted: how much of the laser input beam is to be coupled into the core region and how much of the laser input beam is to be coupled into the at least one annular region. Therefore, the intensity of the corresponding laser beam can be adjusted by means of the beam splitting device. As an alternative to the design of a laser device having a laser beam generating unit by means of which a laser input beam is generated, the laser device can have at least two separate laser beam generating units, wherein the first laser input beam is coupled into the core region by means of a first laser beam generating unit in the laser beam generating unit, and the second laser input beam is coupled into the annular region. The laser device can have a separate laser beam generating unit for each region of the optical waveguide in particular. By providing a corresponding separate laser beam generating unit, the intensity of the laser beam of the processing beam can be controlled in an individualized manner in a particularly simple manner. A laser device provided with a beam splitter makes it possible to adjust the intensity of the first laser beam and the second laser beam particularly accurately over the entire intensity range from 0 to 100% by splitting a laser input beam.

[0013] In this context, provision can be made in particular for a first portion of at least 80% of the laser power of the laser input beam to be coupled into the core region in the cutting region and for a second portion of at most 20% of the laser power of the laser input beam to be coupled into the at least one annular region, thereby ensuring that the workpiece is reliably cut through the entire thickness in the respective cutting region by means of the first laser beam and that the respective cut edges of the workpiece are rounded by means of the second laser beam without causing a strong flow of material of the workpiece.

[0014] In this context, in another possible embodiment of the invention, it can be provided that the first intensity of the first laser beam is set by adapting the intensity of the laser input beam. In other words, the intensity of the laser input beam is modified by means of the laser beam generation unit, thereby adapting the intensity of the portion of the laser input beam that is coupled into the core region by means of the beam splitter for generating the first laser beam. By adapting the intensity of the laser input beam, the intensity of the first laser beam can be modified particularly easily.

[0015] In another possible embodiment of the present invention, it can be provided that the first intensity of the first laser beam is adjusted by adapting the portion of the laser input beam coupled into the core region by means of a beam splitter. Thus, the distribution of the laser input beam between the core region and the at least one annular region can be adapted in order to adjust the intensity of the first laser beam.

[0016] In another possible embodiment of the present invention, it is proposed that the second intensity of the second laser beam is the same in the stabilization region and in the cutting region. This makes it possible to achieve that the rounding radius at the cut edge of the metal workpiece is constant in all regions along the cutting direction. This makes it possible to avoid differences in the rounding radius in the region of the workpiece where the material bridge remains relative to the rounding radius in the region where the material bridge does not remain. This makes it possible to achieve a particularly uniformly rounded cut edge on the workpiece.

[0017] In particular, in order to set the intensity of the first laser beam, both the intensity of the laser input beam and the distribution of the laser input beam to the core region and the at least one annular region can be adapted, since the intensity of the first laser beam can thereby be reduced, but despite the reduced intensity of the laser input beam, the intensity of the second laser beam can still remain constant due to the adapted distribution of the laser input beam. If only the laser power of the laser input beam is reduced, for example by approximately 20%, in order to produce material bridges in the stabilization region of the workpiece, then both the power of the first laser beam and the power of the second laser beam provided for rounding are reduced by 20% each. As a result, it can occur that the rounding radius is reduced in the stabilization region compared to the cutting region. In order to circumvent this, the power reduction (power reduction) of the laser input beam in the stabilization region, which is required to reduce the intensity of the first laser beam in order to produce material bridges, is partially coupled into the annular region of the optical waveguide. Thus, when machining the workpiece in the stabilization region, a larger portion of the laser input beam is coupled into the annular region by means of the beam splitter than in the cutting region. However, the portion of the laser input beam coupled into the annular region during machining of the stabilization region of the workpiece is increased only to such an extent that the power of the second laser beam in the stabilization region and in the cutting region is the same and is thus substantially constant during machining of the metal workpiece.

[0018] In another feasible design of the present invention, it is proposed that the workpiece is cut into the workpiece in the stabilization region at least to half of the thickness of the workpiece, in particular to at least 2 / 3 of the thickness of the workpiece. The workpiece can be cut into at least 3 / 4 of its thickness, in particular to at least 4 / 5 of its thickness in the stabilization region. Therefore, the material bridge generated thereby extends over less than half of the thickness of the workpiece, in particular less than one-third of the thickness of the workpiece, in particular less than one-quarter of the thickness of the workpiece, in particular less than one-fifth of the thickness of the workpiece. The greater the corresponding height of the retained material bridge, the more stable the material bridge generated, but the greater the force required to separate the workpiece parts generated when processing the workpiece. The smaller the height of the generated material bridge, the smaller the mass of the residue of the material bridge that is to be removed from the corresponding workpiece part when the material bridge is disconnected. Cutting into the workpiece at least to half of the thickness of the workpiece in the stabilization region ensures that a reliably rounded cutting edge can be provided by means of the second laser beam.

[0019] In another feasible design of the present invention, it is proposed that the processing beam includes at least three laser beams with different intensities, and the laser beams are arranged next to each other on a line extending on the workpiece surface perpendicular to the cutting direction. In order to generate the processing beam with the at least three laser beams, a laser device with an optical waveguide configured as a 3-in-1 optical fiber can be used. Alternatively, the corresponding laser beams can be provided by means of laser devices that are separated and independent from each other, wherein a separate laser device is provided for each laser beam. By providing three laser beams with different intensities, the workpiece can be cut by means of the first laser beam, and the rounded cutting edge of the workpiece can be provided by means of the second laser beam and the third laser beam, which also have different intensities. By providing the second laser beam and the third laser beam with different intensities, the rounded contour of the cutting edge can be preset particularly accurately.

[0020] If the optical waveguide includes a core region and two further annular regions, a first laser beam, a second laser beam and a third laser beam are generated when the laser input beam is coupled not only into the core region but also into the two annular regions. The third laser beam is arranged next to the first laser beam and the second laser beam and thus strikes the workpiece surface of the workpiece next to the first laser beam and the second laser beam when the machining beam is directed onto the workpiece. In particular, the third laser beam can surround the second laser beam on the circumference and have an annular image on the workpiece surface. Therefore, the machining beam can have the first laser beam in the center and the second laser beam that surrounds the first laser beam in an annular manner and the third laser beam that surrounds the second laser beam in an annular manner.

[0021] The invention also relates to a laser device for machining a metal workpiece by means of a machining beam in a method as already described in conjunction with the method according to the invention. The workpiece can be supported, for example, on a workpiece support during the machining process. The laser device can be, for example, part of a laser cutting facility, such as a flat-plate laser cutting facility or a tube laser cutting facility. The machining beam comprises a first laser beam having a first intensity for cutting the workpiece in the thickness direction, and a second laser beam having a second intensity smaller than the first intensity, which is projected onto the workpiece surface of the workpiece next to the first laser beam, whereby a rounded cutting edge can be generated by means of the second laser beam. The laser device comprises at least one laser beam generating unit, which is configured to generate a laser input beam. In addition, the laser device comprises an optical waveguide having a core region and at least one annular region, wherein, when the at least one laser input beam is coupled into the optical waveguide, the core region is configured to provide the first laser beam, and the at least one annular region is configured to provide the second laser beam. In addition, the laser device comprises a control device, which is configured to control the laser device for adapting the first intensity of the first laser beam. The laser device can be designed as a solid-state laser, such as a fiber laser, in particular with one or more fiber laser modules, a disk laser or a diode laser. The optical waveguide can be designed as a so-called multi-clad optical fiber with a core region and at least one annular region surrounding the core region. The multi-clad optical fiber is designed in particular for guiding a first laser beam in the core region and a second laser beam in the annular region from a laser beam generating unit to a processing head. With the aid of the processing head, the processing beam can be directed onto a workpiece surface of the workpiece.

[0022] The laser device may further comprise a beam splitting device, which is arranged between the laser beam generating unit and the optical waveguide, in particular a multi-clad optical fiber. The beam splitting device is configured to distribute the laser input beam provided by the laser beam generating unit to the corresponding regions of the multi-clad optical fiber. Here, the beam splitting device may split the laser input beam provided by the laser beam generating unit into a first laser beam and a second laser beam, wherein the first laser beam is coupled into the core region of the multi-clad optical fiber and the second laser beam is coupled into the ring region of the multi-clad optical fiber. If the processing beam comprises more than two laser beams, the multi-clad optical fiber may have a plurality of ring regions, which are preferably arranged concentrically relative to one another and are respectively designed to guide the corresponding laser beams. The beam splitting device may, for example, comprise a so-called wedge beam splitter, which is arranged in the beam path of the laser input beam and controllably couples a portion of the laser input beam into the core region and / or the at least one ring region of the multi-clad optical fiber by lateral displacement relative to the laser input beam.

[0023] The laser device enables uninterrupted processing of a workpiece, wherein the workpiece is cut during processing and provided with rounded cut edges and at least one material bridge remains for holding together the respective workpiece parts produced by cutting the workpiece, the material bridge being a so-called nanojoint.

[0024] Other features of the invention can be derived from the following description of the drawings and from the drawings. The features and feature combinations mentioned above in the specification and the features and feature combinations described below and / or shown individually in the drawings can be used not only in the respectively described combination but also in other combinations or individually without departing from the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings show:

[0026] Figure 1 A schematic side view of a laser device is shown, with the aid of which a metal workpiece is processed;

[0027] Figure 2 A schematic sectional view shows a metal workpiece which is machined by means of a machining beam of a laser device;

[0028] Figure 3 shows a schematic side view of a machined metal workpiece;

[0029] Figure 4 showing a perspective view of a machined metal workpiece; and

[0030] Figure 5 A side view of a machined metal workpiece is shown. DETAILED DESCRIPTION

[0031] Identical elements or elements with the same function are provided with the same reference symbols in the figures.

[0032] exist Figure 1 The various components of the laser device are shown in FIG. Figure 1 1 and 2. The optical waveguide 10 and the focusing lens 12 of the focusing optical device are shown in the figure. The focusing lens 12 is configured to focus the optical beam provided by the optical waveguide 10. The laser device comprises a laser beam generating unit (not shown in the figure) which is configured to generate a laser input beam. In addition, the laser device comprises Figure 1, which is currently configured as a multi-clad optical fiber, in particular as a 2-in-1 optical fiber. The 2-in-1 optical fiber comprises a core region 14 and an annular region 16 surrounding the core region 14 on the circumferential side. As an alternative to the design of a multi-clad optical fiber as a 2-in-1 optical fiber, the multi-clad optical fiber can be configured as a so-called 3-in-1 optical fiber having a core region 14, an inner annular region and an outer annular region, wherein the inner annular region surrounds the core region 14 on the circumferential side, and the outer annular region surrounds the inner annular region on the circumferential side. In addition, the laser device comprises a beam splitting device (beam splitting device) not shown in the figure, by means of which a laser input beam provided by a laser beam generating unit can be distributed to the core region 14 and the annular region 16. In particular, the beam splitting device is configured to adjust the distribution of the laser input beam to the core region 14 and the annular region 16 in terms of proportions.

[0033] In order to process a metal workpiece W, a processing beam 18 is provided by a laser device and directed onto the workpiece W. The processing beam 18 comprises a first laser beam 20 and a second laser beam 22. The first laser beam 20 and the second laser beam 22 are respective sub-beams of a common laser beam, which is provided by means of a multi-clad optical fiber. The first laser beam 20 is provided via the core region 14 of a 2-in-1 optical fiber, and the second laser beam 22 is provided via the ring region 16 of the 2-in-1 optical fiber. The laser beams 20, 22 are focused toward the workpiece W by means of focusing optics, in the present case a focusing lens 12. In order to process a metal workpiece W, the processing beam 18 is moved relative to the workpiece W in a cutting direction 24 extending into the plane of the drawing. Therefore, the processing beam 18 moves in the cutting direction 24 on a workpiece surface 26 of the workpiece W. The workpiece W is processed by means of the laser beams 20, 22 of the processing beam 18 that impinge on the workpiece surface 26. The first laser beam 20 has a first intensity, and the second laser beam 22 has a second intensity that is lower than the first intensity of the first laser beam 20. The first laser beam 20 is configured to cut the workpiece W in a thickness direction 28 of the workpiece W. In this case, the workpiece W can be cut through its entire thickness in the thickness direction 28 by means of the first laser beam 20. The second laser beam 22 is configured to generate a rounded cut edge 30. In other words, when machining the workpiece W, the workpiece W is divided into a first workpiece part W1 and a second workpiece part W2 by means of the machining beam 18, wherein the second laser beam 22 is used to achieve that the respective cut edges 30 of the first workpiece part W1 and the second workpiece part W2 are rounded after machining.

[0034] If a 3-in-1 fiber is used as the multi-clad fiber, the machining beam 18 can include three laser beams having mutually different intensities which are arranged next to each other on a line extending perpendicularly to the cutting direction 24 on the workpiece surface 26 .

[0035] exist Figure 2 2 shows an enlarged view of the region in which the workpiece W is cut by means of the machining beam 18. It can be seen particularly clearly here that the first laser beam 20 and the second laser beam 22 are arranged next to each other on a line 32 extending perpendicularly to the cutting direction 24 on the unmachined workpiece surface 26. In this case, the second laser beam 22 can have an annular image on the unmachined workpiece surface 26, which surrounds the image of the first laser beam 20, which can be particularly circular, on the circumference. Alternatively, the second laser beam 22 can be arranged only next to the first laser beam 20 and not completely surround the image of the first laser beam 20. In this case, the second laser beam 22 is arranged next to the first laser beam 20 in the direction of the generated cutting edge 30, whereby the cutting edge 30 is rounded.

[0036] exist Figure 3 1 shows a side view of one of the workpiece parts obtained by machining a workpiece W, in the present case a first workpiece part W1. It can be seen here that the first workpiece part W1 has a rounded cutting edge 30. Furthermore, a cut surface 34 produced by cutting the workpiece W with the aid of the first laser beam 20 can be seen. The rounded cutting edge 30 adjoins the cut surface 34. Furthermore, in Figure 3 In the figure, in the region of the cut surface 34, a material bridge 36 can be seen which remains when the workpiece W is cut and which is completely severed in order to separate the workpiece W into the first workpiece part W1 and the second workpiece part W2 after this machining. The material bridge 36 is a so-called nanojoint which extends over less than half the thickness of the workpiece W, in particular less than one-third the thickness of the workpiece, in particular less than one-quarter the thickness of the workpiece, in particular less than one-fifth the thickness of the workpiece. The material bridge 36 extends over the length of the stabilization region 38 of the workpiece W extending in the cutting direction 24. In the cutting direction 24, the stabilization region 38 is followed by a corresponding cutting region 40 of the workpiece W.

[0037] In the method for machining a metal workpiece W, in order to produce a material bridge 36, a first intensity of the first laser beam 20 is reduced in a stabilization region 38 compared to a cutting region 40. As a result, the workpiece W is completely cut through in its thickness direction 28 in the respective cutting region 40 by means of the first laser beam 20 and is only cut into in the stabilization region 38. Thus, during machining of the workpiece W in a cutting direction 24 by means of the machining beam 18, the material bridge 36 remains. During machining of the workpiece W by means of the machining beam 18, the first workpiece part W1 and the second workpiece part W2 are held together via the material bridge 36, thereby preventing the workpiece parts W1, W2 from tipping relative to each other. After machining of the workpiece W by means of the machining beam 18 is completed, the at least one material bridge 36 is broken in order to separate the first workpiece part W1 from the second workpiece part W2.

[0038] In order to keep the rounding radius constant along the entire cutting edge 30, it is proposed that only the intensity of the first laser beam 20 is adapted in the stabilization region 38 and that the second intensity of the second laser beam 22 is the same in the stabilization region 38 and in the corresponding cutting region 40. The second intensity of the second laser beam 22 is therefore kept constant during the entire processing of the workpiece W by means of the processing beam 18. During the cutting of the workpiece W by means of the first laser beam 20, a rounding is simultaneously produced at the upper end of the cut flank by the action of the second laser beam 22 having a second intensity that is smaller than the first intensity. The first laser beam 20 thus serves as a core beam for producing the separating cut, and the second laser beam 22 thus serves as an annular beam for melting and thus at least partially for rounding the workpiece surface or the upper cutting edge 30.

[0039] In the respective cutting region 40, in order to provide an initial value for the first intensity of the first laser beam 20, at least 80% of the laser power of the laser input beam can be coupled into the core region 14 of the optical waveguide 10, and in order to provide a second intensity of the second laser beam 22, a second portion of at most 20% of the laser power of the laser input beam can be coupled into the annular region 16. At the transition between the cutting region 40 and the stabilization region 38, the first intensity of the first laser beam 20 is set by adapting the intensity of the laser input beam. In addition, in order to set the first intensity of the first laser beam 20 by means of the beam splitter, the portion of the laser input beam coupled into the core region 14 is adapted in order to ensure that the second intensity of the second laser beam 22 remains constant.

[0040] exist Figure 4 , the first workpiece part W1 is shown in a perspective view, in which the rounded cutting edges 30 along the inner contour and the outer contour of the first workpiece part W1 can be seen particularly clearly. Figure 5, the first workpiece part W1 is shown in a side view, wherein the produced and severed material bridges 36 can be seen particularly clearly, which extend only over a partial region of the thickness of the workpiece part W1 .

[0041] The invention described is based on the following recognition that when edge rounding is performed by means of an optical element, especially a 2-in-1 optical fiber or a 3-in-1 optical fiber, a workpiece part held in a residual grid by a micro-joint cannot be completely rounded. At the position of the micro-joint, rounding cannot be applied because the micro-joint extends over the entire component thickness. If the edge rounding process should be performed at the position of the micro-joint, the component that is also fixed to the residual grid by means of the micro-joint will be melted. Thus, the component will not be usable and may only be repaired by very laborious, time-consuming and costly reprocessing. The problem is solved in the following manner by using a nano-joint instead of a micro-joint to hold the component on the residual grid when processing the workpiece W. The cutting edge 30 can be rounded above the nano-joint, and the nano-joint extends with its height, especially on no more than one-third of the thickness of the workpiece. The nano-joint extends, in particular, on at most a quarter of the thickness of the workpiece W, in particular, on at most a fifth of the thickness of the workpiece W.

[0042] Within the scope of the method, the rounding of the cutting edge 30 is carried out by means of a 2-in-1 optical fiber or by means of a 3-in-1 optical fiber in direct cutting or during the cutting process. Here, the cutting is carried out by means of the laser power of the optical fiber core and thus by means of the first laser beam 20, and the cutting edge 30 is rounded by means of the laser power of the optical fiber jacket and thus by means of the second laser beam 22. In order to protect the tipped parts, in particular the good parts, from colliding with the cutting head of the processing device with a laser device for processing the metal workpiece W, the workpiece parts W1, W2 are fixed by means of a nano joint. The nano joint is located in particular in the lower third of the cutting surface 34 and is produced by reducing the laser power during the cutting process. As a result, the edge rounding can be applied above the nano joint.

[0043] If the laser power is reduced at the nano-joint by, for example, about 20%, the laser power available for rounding in the fiber jacket is also reduced by 20%. The rounding radius of the cutting edge 30 is thereby reduced. In order to circumvent the situation, the power reduction required for producing the nano-joint can be partially coupled into the fiber jacket of the optical waveguide 10. For this purpose, the switching position of the wedge-shaped beam splitter of the beam splitting device is changed, whereby a percentage-wise greater power and thus a larger share of the laser input beam is coupled into the fiber jacket and thus into the annular region 16. Here, the share of the laser power of the laser input beam coupled into the annular region 16 is only increased so that the rounding radius of the cutting edge 30 is the same in the cutting region 40 and the stabilization region 38 and can thus remain constant over the entire cutting edge 30.

[0044] The following describes an example of processing a 5 mm thick structural steel as a workpiece W with a total laser power of 12 kW in the context of high-speed cutting, currently nitrogen cutting. Here, the maximum available laser power is 12 kW. When using a 3-in-1 optical fiber, 10 kW can be coupled into the optical fiber core for cutting, which involves about 83.3% of the total laser power. 2 kW of laser power is coupled into the optical fiber sleeve for rounding, which involves about 16.7% of the total laser power. In order to prevent the qualified parts from tipping over and causing a collision with the laser cutting head of the processing device, a nano joint is provided, especially at the end of the cut. For this purpose, the laser power is reduced by 20% to 8 kW in the optical fiber core. In the optical fiber sleeve, the laser power is kept constant at 2 kW. This is achieved by reducing the total laser power to 10 kW in general. By reaching another wedge-splitting position of the wedge-shaped beam splitter, 80% of the 10 kW total laser power is coupled into the optical fiber core and 20% is coupled into the optical fiber sleeve.

[0045] Alternatively, the laser power for the fiber core and for the fiber jacket can come from two different laser beam sources. To produce the material bridge 36, the laser power of the laser beam source whose laser beam is coupled into the fiber core can be reduced at the nanojoint to be produced.

[0046] The laser device comprises a 2-in-1 optical fiber or in particular a 3-in-1 optical fiber as an optical waveguide 10, wherein a large portion of the total laser power, in particular at least 80%, is coupled into the fiber core and is thus available for cutting the workpiece W. For the rounding process, a smaller portion of the total laser power, in particular up to 20%, is coupled into the fiber jacket. In order to avoid tipping of the resulting workpiece part, at least one nano-joint is arranged at the end of the cutting contour or in the middle of the cutting contour by reducing the laser power of the fiber core by approximately 20%.

[0047] In summary, the present invention shows how collision-free edge rounding can be achieved.

[0048] Reference numerals list

[0049] 10. Optical waveguide

[0050] 12 Focusing lens

[0051] 14 core area

[0052] 16 Ring Area

[0053] 18 Processing beam

[0054] 20 First laser beam

[0055] 22 Second laser beam

[0056] 24 Cutting direction

[0057] 26 Workpiece surface

[0058] 28 Thickness direction

[0059] 30 Cutting edges

[0060] 32 lines

[0061] 34 Cut surface

[0062] 36 Material bridge

[0063] 38 Stabilization Area

[0064] 40 Cutting area

[0065] W Workpiece

[0066] W1 First workpiece part

[0067] W2 Second workpiece part

Claims

1. A method for machining a metal workpiece (W), in which method, - directing a machining beam (18) onto the workpiece (W) and moving the machining beam relative to the workpiece (W) in a cutting direction (24), wherein: The machining beam (18) comprises: a first laser beam (20) having a first intensity for cutting the workpiece (W) in a thickness direction (28); and a second laser beam (22) having a second intensity that is smaller than the first intensity and incident on a workpiece surface (26) of the workpiece (W) next to the first laser beam (20), whereby a rounded cutting edge (30) is generated by means of the second laser beam (22); and - In order to produce a material bridge (36) of the metal workpiece (W), a first intensity of the first laser beam (20) is reduced in a stabilization region (38) of the workpiece (W) extending along a cutting direction (24) compared to at least one cutting region (40) of the workpiece (W) adjacent to the stabilization region (38) along the cutting direction (24), thereby cutting into the workpiece (W) in the stabilization region (38) at most in a partial region of the thickness of the workpiece.

2. The method according to claim 1, wherein: The first laser beam (20) and the second laser beam (22) are arranged next to each other on a line (32) extending perpendicularly to the cutting direction (24) on the workpiece surface (26).

3. The method according to claim 1 or 2, wherein: The processing beam (18) is provided by means of a laser device, the laser device comprising: - an optical waveguide (10) having a core region (14) and at least one annular region (16), a laser beam generating unit, by means of which a laser input beam is generated, and - a beam splitting device, by means of which the laser input beam is split onto the core region (14) for generating the first laser beam (20) and onto the at least one annular region (16) for generating the second laser beam (22).

4. The method according to claim 3, wherein: In the cutting region (40), a first portion of at least 80% of the laser power of the laser input beam is coupled into the core region (14), and a second portion of at most 20% of the laser power of the laser input beam is coupled into the at least one annular region (16).

5. The method according to claim 3 or 4, wherein: A first intensity of the first laser beam (20) is set by adapting the intensity of the laser input beam.

6. The method according to any one of claims 3 to 5, wherein: A first intensity of the first laser beam (20) is set by adapting the portion of the laser input beam coupled into the core region (14) by means of the beam splitting device.

7. The method according to any one of claims 3 to 6, wherein: A second intensity of the second laser beam (22) is the same in the stabilization region (38) and in the cutting region (40).

8. A method according to any one of the preceding claims, wherein: The workpiece (W) is cut into in the stabilization region (38) at least to half the thickness of the workpiece, in particular at least to two thirds of the thickness of the workpiece.

9. A method according to any one of the preceding claims, wherein: The machining beam (18) comprises at least three laser beams having mutually different intensities, which are arranged next to each other on a line (32) extending perpendicularly to the cutting direction (24) on the workpiece surface (26).

10. A laser device for machining a metal workpiece (W) by means of a machining beam (18) in a method according to any one of the preceding claims, the machining beam comprising: a first laser beam (20) having a first intensity for cutting the workpiece (W) in a thickness direction (28); and, a second laser beam (22) having a second intensity that is lower than the first intensity and which impinges on a workpiece surface (26) of the workpiece (W) next to the first laser beam (20), whereby a rounded cutting edge (30) can be produced by means of the second laser beam (22), the laser device comprising: - at least one laser beam generating unit configured to generate a laser input beam, - an optical waveguide (10) having a core region (14) and at least one ring region (16), wherein, when at least one laser input beam is coupled into the optical waveguide (10), the core region (14) is configured to provide the first laser beam (20) and the at least one ring region (16) is configured to provide the second laser beam (22), A control device configured to control the laser device for adapting a first intensity of the first laser beam (20).

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