DE102022127956A1 - METHOD FOR MACHINING A METAL WORKPIECE AND LASER DEVICE - Google Patents

Abstract

The invention relates to a method in which a processing beam (18) is directed at a workpiece (W) and moved in a cutting direction (24) relative to the workpiece (W), wherein the processing beam (18) comprises a first laser beam (20) with a first intensity for cutting the workpiece (W) and a second laser beam (22) with a lower second intensity which impinges on a workpiece surface (26) of the workpiece (W) next to the first laser beam (20), whereby a rounded cutting edge (30) is produced by means of the second laser beam (22); and for producing a material web (36) of the metallic workpiece (W), the first intensity of the first laser beam (20) is reduced in a stabilization region (38) of the workpiece (W) in comparison to at least one cutting region (40) of the workpiece (W) adjacent to the stabilization region (38), whereby the workpiece (W) is cut in the stabilization region (38) over at most a partial region of its thickness.

Description

The invention relates to a method for machining a metallic workpiece and a laser device for machining a metallic workpiece by means of a machining beam.

From the WO 2022/037797 A1 A method is known for producing at least one workpiece part and a remaining workpiece from a workpiece by means of a laser beam emerging from a laser processing head. In the method, the workpiece is cut along a cutting line, with cutting edges being formed on the workpiece part and on the remaining workpiece. In the method, the workpiece is also modified in the form of a rounding, while the workpiece part is connected to the remaining workpiece.

In addition, the EN 10 2019 125 103 A1 a method for laser cutting a workpiece is known. In the method, a processing laser beam is generated for rough machining of the workpiece. Two energy intensity ranges of the processing laser beam are generated, with a first energy intensity range for rough machining of the workpiece having a greater time-integrated radiation energy than the second energy intensity range for at least partial fine machining of a cutting edge. The workpiece is irradiated with this processing beam.

The object of the present invention is to provide a solution which enables a particularly fast and precise cutting of a workpiece by means of a laser device, whereby sharp cutting edges are avoided.

The object is solved by the subject matter of the independent claims. Further possible embodiments of the invention are specified in the subclaims, the description and the drawing. Features, advantages and possible embodiments that are set out in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages and possible embodiments of the respective subject matter of the other independent claims and of any possible combination of the subject matter of the independent claims, if appropriate in conjunction with one or more of the subclaims.

The invention relates to a method for machining a metallic workpiece, which is in particular plate-shaped or tubular. In the method, it is provided that a machining beam is directed at the workpiece and moved in a cutting direction relative to the workpiece. The machining beam is provided by means of a laser device. Directing the machining beam at the workpiece means that the machining beam is provided by the laser device, is aligned with the workpiece and strikes the workpiece surface of the workpiece. The machining beam comprises a first laser beam with a first intensity, which is provided for cutting the workpiece in a thickness direction. In other words, when machining the metallic workpiece, the workpiece is cut in its thickness direction by means of the first laser beam. The machining beam further comprises a second laser beam which strikes a workpiece surface of the workpiece in addition to the first laser beam and has a second intensity that is lower than the first intensity of the first laser beam. A rounded cutting edge of the workpiece is produced by means of the second laser beam. The second laser beam can be used to make the material of the workpiece flow, rounding off any cutting edges that may arise when the workpiece is cut using the first laser beam. The amount of post-processing work required on the workpiece can therefore be kept to a minimum. The processing beam thus enables the workpiece to be cut, creating rounded cutting edges. Subsequent rounding of cutting edges can therefore be omitted.

The processing beam thus comprises the first laser beam and the second laser beam arranged at least partially next to the first laser beam. For example, the first laser beam and the second laser beam can at least partially overlap. It is possible for the first laser beam and the second laser beam to be arranged concentrically to one another. This means that an image of the first laser beam on the workpiece surface of the workpiece forms an inner region of the processing beam and the image of the second laser beam encloses 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 ring-shaped and thus surrounds the image of the first laser beam in a ring. In a plane of the workpiece surface, the images of the first laser beam and the second laser beam can adjoin one another without overlapping or spaced apart by a small separation gap.

The method further provides that, for producing a material web of the metallic workpiece, the first intensity of the first laser beam is adjusted in a direction extending in the cutting direction extending stabilization region of the workpiece is reduced in comparison to at least one cutting region of the workpiece adjacent to the stabilization region in the cutting direction. As a result, the workpiece is cut in the stabilization region over at most a partial region of its thickness. Leaving the at least one material web standing when cutting the workpiece makes it possible for two workpiece parts created by cutting the workpiece to be prevented from tilting towards one another during machining of the workpiece, as a result of which the workpiece can be cut particularly precisely. If the workpiece parts were to tilt towards one another in an uncontrolled manner during machining of the metallic workpiece, the machining beam could deviate from a predetermined cutting line of the workpiece, as a result of which the workpiece would be cut. Such cutting of the workpiece can be avoided by the at least one material web. After the cutting of the metallic workpiece by means of the machining beam has ended, respective workpiece parts of the workpiece are held together by means of the at least one material web. Material webs of the workpiece that are held in place are then severed in order to separate the workpiece parts of the workpiece from one another. At least one of the separated workpiece parts can be a component, which has thus been cut out of the metal workpiece as part of the process. The at least one material web can be severed by means of the processing beam or mechanically, for example by breaking through. The severing can be carried out, for example, by pressing, knocking out or shaking out a first workpiece part, in particular the component, from a surrounding second workpiece part, which is thus a residual workpiece or a residual grid of the workpiece. Alternatively, the material web can be severed by bending or shaking off several workpiece parts held together by material webs. The at least one material web extends as a so-called "nano joint" only over a partial area of the thickness of the workpiece. This use of the nano joint as a material web has the advantage, compared to so-called micro joints, which extend over the full thickness of the workpiece, that the entire cutting edge can be provided rounded.

The workpiece is cut in the stabilization area. The material web, which only extends over part of the thickness of the workpiece, is thus left in the stabilization area. In the cutting area, the workpiece is completely cut through in its thickness. The cutting area can adjoin the stabilization area to the front or to the back in the cutting direction. In particular, the workpiece comprises at least two cutting areas, one of which adjoins the stabilization area to the front in the cutting direction and the other adjoins the stabilization area to the back in the cutting direction. The stabilization area is thus delimited to the front and to the back in the cutting direction by respective cutting areas. In particular, the workpiece can have a stabilization area surrounded by respective cutting areas for each material web to be produced.

In order to cut the metallic workpiece in a single process step using the processing beam and to provide it with the rounded cutting edge, whereby the at least one material web is produced, at least the intensity of the first laser beam is changed while being guided in the cutting direction over the surface of the workpiece in order to leave the nano joint standing. The first intensity of the first laser beam thus has an initial value in the cutting direction in the cutting area, is reduced to a reduced value in the stabilization area adjacent in the cutting direction and is increased again to the initial value in the further cutting area adjacent to the stabilization area in the cutting direction. The processing beam can thus be guided continuously along the workpiece surface of the workpiece in order to completely cut through the workpiece in the cutting area and to leave the material web standing in the stabilization area, whereby a rounded cutting edge of the workpiece is produced. Reworking the workpiece in several different processing steps, such as cutting the workpiece while leaving at least one material web standing and then separately rounding the edges, can thus be omitted. The process thus enables particularly fast and extensive processing of the metallic workpiece.

In a possible development of the invention, it is provided that the first laser beam and the second laser beam are arranged next to each other in a line running perpendicular to the cutting direction on the workpiece surface. In other words, the processing beam is moved in the cutting direction relative to the workpiece surface, whereby the laser beams are guided next to each other over the workpiece surface of the workpiece. As a result, the laser beams are arranged next to each other in a plane spanned by the workpiece surface perpendicular to the cutting direction. In particular, the laser beams can be arranged perpendicular to the cutting direction and perpendicular to the thickness direction of the workpiece, which coincides with a beam direction in which the laser beams impinge on the workpiece, arranged next to each other. The second laser beam is thus arranged closer to a part of the workpiece that remains when the workpiece is cut than the first laser beam, whereby cutting edges created when the workpiece is cut using the first laser beam can be rounded off by melting and thus flowing material. The cutting edges are rounded off in particular immediately after they are created using the second laser beam, whereby the risk of creating sharp cutting edges can be kept particularly low.

In a further possible embodiment of the invention, it is provided that the processing beam is provided by means of a laser device. This laser device comprises an optical waveguide, a laser beam generation unit and a beam splitting device. The laser device is in particular a fiber laser. The optical waveguide can thus be a so-called fiber, in particular a multiple clad fiber, such as a 2-in-1 fiber or a 3-in-1 fiber. The optical waveguide comprises a core region and at least one ring region. If the optical waveguide is designed as a 2-in-1 fiber, then the optical waveguide comprises the core region and a ring region that encloses the core region on the circumference. If the optical waveguide is designed as a 3-in-1 fiber, then the optical waveguide comprises the core region and two ring regions, an inner ring region and an outer ring region. The inner ring region encloses the core region on the circumference and the outer ring region encloses both the core region and the inner ring region on the circumference. Here, the core region and the two ring regions are arranged concentrically to one another. The laser beam generation unit is set up to generate a laser input beam. In the method, the laser input beam is thus generated by means of the laser beam generation unit. The beam splitting device splits the laser input beam into the core region for generating the first laser beam and into the at least one ring region for generating the second laser beam. The beam splitting device can be used to set which portion of the laser input beam is to be coupled into the core region and which portion of the laser input beam is to be coupled into the at least one ring region. The intensity of the respective laser beams can thus be set by means of the beam splitting device. As an alternative to the design of the laser device with the laser beam generation unit, by means of which the one laser input beam is generated, the laser device can have at least two separate laser beam generation units, wherein a first laser input beam is coupled into the core region and a second laser input beam is coupled into the ring region by means of a first of the laser beam generation units. In particular, the laser device can have a separate laser beam generation unit for each area of the optical waveguide. By providing the respective separate laser beam generation units, the intensities of the laser beams of the processing beam can be controlled individually in a particularly simple manner. The provision of the laser device with the beam splitting device enables the intensities of the first laser beam and the second laser beam to be set particularly precisely over an entire intensity range from 0 to 100% by splitting the one laser input beam.

In this context, it can be provided in particular that in the cutting area a first portion of at least 80% of a laser power of the laser input beam is coupled into the core area and a second portion of at most 20% of the laser power of the laser input beam is coupled into the at least one ring area. This ensures that the workpiece in the respective cutting area is reliably severed across its entire thickness by means of the first laser beam and that respective cutting edges of the workpiece are rounded by means of the second laser beam without causing excessive flow of material from the workpiece.

In this context, in a further possible embodiment of the invention, it can be provided that the first intensity of the first laser beam is set by adjusting 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, whereby the portion of the laser input beam which is coupled into the core region for generating the first laser beam by means of the beam splitting device is adjusted in its intensity. By adjusting the intensity of the laser input beam, the intensity of the first laser beam can be modified particularly easily.

In a further possible embodiment of the invention, it can be provided that the first intensity of the first laser beam is adjusted by adjusting a portion of the laser input beam coupled into the core region by means of the beam splitting device. The division of the laser input beam between the core region and the at least one ring region can thus be adjusted in order to adjust the intensity of the first laser beam.

In a further possible embodiment of the invention, it is provided that the second intensity of the second laser beam is the same in the stabilization area and in the cutting area. This makes it possible to ensure that the rounding radius on the cutting edge of the metal workpiece is constant in all areas along the cutting direction. Differences in the rounding radius in areas of the workpiece in which the material web is provided compared to areas in which no material web is provided can thus be avoided. A particularly evenly rounded cutting edge can thus be achieved on the workpiece.

In particular, to adjust the intensity of the first laser beam, both the intensity of the laser input beam can be adjusted and the division of the laser input beam can be divided between the core region and the at least one ring region, since this allows the intensity of the first laser beam to be reduced, whereas despite the reduced intensity of the laser input beam, the intensity of the second laser beam can be kept constant due to the adjustment of the division of the laser input beam. If only the laser power of the laser input beam for generating the material web in the stabilization region of the workpiece is reduced, for example by approximately 20%, then both the power of the first laser beam and the power of the second laser beam, which is available for rounding, are each reduced by 20%. This can result in a rounding radius being reduced in the stabilization region compared to the cutting regions. To avoid this, the power reduction of the laser input beam, which is required in the stabilization region to reduce the intensity of the first laser beam for generating the material web, is partially coupled into the ring region of the optical waveguide. Thus, with the beam splitting device, a larger proportion of the laser input beam is coupled into the ring region when processing the workpiece in the stabilization region than into the cutting region. However, the proportion of the laser input beam which is coupled into the ring region when processing the stabilization region of the workpiece is only increased 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 thus essentially constant during processing of the metallic workpiece.

In a further possible embodiment of the invention, it is provided that the workpiece is cut in the stabilization area over at least half of its thickness, in particular over at least 2/3 of its thickness. The workpiece can be cut in the stabilization area, in particular over at least 3/4 of its thickness, in particular over at least 4/5 of its thickness. The resulting material web thus produced consequently extends over less than half, in particular over less than a third, in particular over less than a quarter, in particular over less than a fifth of the thickness of the workpiece. The greater the respective height of the remaining material web, the more stable the material web produced, but the more force is required in order to separate workpiece parts that arise during machining of the workpiece from one another. The lower the height of the material web produced, the less mass of residues of the material web may have to be removed from the respective workpiece parts after the material web has been severed. Cutting the workpiece in the stabilization area at least over half the thickness of the workpiece ensures that a reliably rounded cutting edge can be provided by means of the second laser beam.

In a further possible embodiment of the invention, it is provided that the processing beam comprises at least three laser beams with mutually different intensities, which are arranged next to one another in a line running perpendicular to the cutting direction on the workpiece surface. The laser device which has the optical waveguide designed as a 3-in-1 fiber can be used to generate the processing beam with the at least three laser beams. Alternatively, the respective laser beams can be provided by means of separate laser devices, with a separate laser device being provided for each laser beam. By providing the three laser beams with mutually different intensities, the workpiece can be cut by means of the first laser beam, while a rounded cutting edge of the workpiece can be provided by means of the second laser beam and the third laser beam, which also have mutually different intensities. By providing the second and third laser beams with mutually different intensities, a rounding contour of the cutting edge can be specified particularly precisely.

If the optical waveguide includes the core area and two further ring areas, then when the laser input beam is coupled into both the core area and both ring areas, a first laser beam, a second laser beam and a third laser beam are created. The third laser beam is arranged next to the first and second laser beams and thus hits the first and second laser beams. the workpiece surface of the workpiece when aligning the processing beam onto the workpiece. In particular, the third laser beam can enclose the second laser beam circumferentially and have a ring-shaped image on the workpiece surface. The processing beam can thus have the first laser beam in the middle, the second laser beam, which surrounds the first laser beam in a ring, and the third laser beam, which surrounds the second laser beam in a ring.

The invention further relates to a laser device for processing a metallic workpiece by means of a processing beam in a method as has already been described in connection with the method according to the invention. The workpiece can be stored on a workpiece support during the processing process, for example. The laser device can be part of a laser cutting system, such as a flatbed laser cutting system or a tube laser cutting system, for example. The processing beam comprises a first laser beam with a first intensity for cutting the workpiece in a thickness direction and a second laser beam impinging on a workpiece surface of the workpiece next to the first laser beam with a second intensity that is lower than the first intensity, whereby a rounded cutting edge can be generated by means of the second laser beam. The laser device comprises at least one laser beam generation unit, which is set up to generate a laser input beam. The laser device further comprises an optical waveguide with a core region and at least one ring region, wherein when at least one laser input beam is coupled into the optical waveguide, the core region is designed to provide the first laser beam and the at least one ring region is designed to provide the second laser beam. In addition, the laser device comprises a control device which is designed to control the laser device to adjust the first intensity of the first laser beam. The laser device can be designed as a solid-state laser, such as in particular a fiber laser 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 fiber with a core region and at least one ring region surrounding the core region. The multi-clad fiber is designed in particular to guide the first laser beam within the core region and the second laser beam within the ring region from the laser beam generation unit to a processing head. The processing beam can be directed onto the workpiece surface of the workpiece by means of the processing head.

The laser device can further comprise a beam splitting device which is arranged between the laser beam generation unit and the optical waveguide, in particular the multi-clad fiber. The beam splitting device is designed to split the laser input beam provided by the laser beam generation unit into respective regions of the multi-clad fiber. In this case, the beam splitting device can split the laser input beam provided by the laser beam generation unit into the first laser beam and the second laser beam, with the first laser beam being coupled into the core region of the multi-clad fiber and the second laser beam being coupled into the ring region of the multi-clad fiber. If the processing beam comprises more than two laser beams, the multi-clad fiber can have a plurality of ring regions which are preferably arranged concentrically to one another and which are each designed to guide a corresponding laser beam. The beam splitting device can, for example, comprise a so-called wedge switch, which is arranged in the beam path of the laser input beam and, by lateral displacement relative to the laser input beam, controllably couples portions of the laser input beam into the core region and/or the at least one ring region of the multi-clad fiber.

The laser device enables the workpiece to be processed in one go, whereby the workpiece is cut during processing and provided with a rounded cutting edge and at least one material web, which is a so-called nano joint, is provided for holding together respective workpiece parts resulting from the cutting of the workpiece.

Further features of the invention can be seen from the following description of the figures and from the drawing. The features and combinations of features mentioned above in the description as well as the features and combinations of features shown below in the description of the figures and/or in the figures alone can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the invention.

• 1 eine schematische Seitenansicht einer Lasereinrichtung, mittels welcher ein metallisches Werkstück bearbeitet wird;
• 2 eine schematische Schnittansicht des mittels eines Bearbeitungsstrahls der Lasereinrichtung bearbeiteten metallischen Werkstücks;
• 3 eine schematische Seitenansicht des bearbeiteten metallischen Werkstücks;
• 4 eine Perspektivansicht des bearbeiteten metallischen Werkstücks; und
• 5 eine Seitenansicht des bearbeiteten metallischen Werkstücks.

The drawing shows in:

• 1 a schematic side view of a laser device by means of which a metallic workpiece is processed;
• 2 a schematic sectional view of the metallic workpiece processed by means of a processing beam of the laser device;
• 3 a schematic side view of the machined metallic workpiece;
• 4 a perspective view of the machined metallic workpiece; and
• 5 a side view of the machined metal workpiece.

Identical or functionally equivalent elements are provided with the same reference symbols in the figures.

In 1 individual components of a laser device are shown. For example, in 1 an optical waveguide 10 and a focusing lens 12 of a focusing optics are shown. The focusing lens 12 is designed to focus light beams provided by the optical waveguide 10. The laser device comprises a laser beam generation unit (not shown in the figures) which is designed to generate a laser input beam. Furthermore, the laser device comprises the laser beam generator shown in 1 shown optical waveguide 10, which in the present case is designed as a multi-clad fiber, specifically as a 2-in-1 fiber. This 2-in-1 fiber comprises a core region 14 and a ring region 16 that surrounds the core region 14 on the circumference. As an alternative to the design of the multi-clad fiber as a 2-in-1 fiber, the multi-clad fiber can be designed as a so-called 3-in-1 fiber with a core region 14, an inner ring region and an outer ring region, wherein the inner ring region surrounds the core region 14 on the circumference and the outer ring region surrounds the inner ring region on the circumference. The laser device further comprises a beam splitting device (not shown in the figures), by means of which the laser input beam provided by the laser beam generation unit can be split between the core region 14 and the ring region 16. In particular, the beam splitting device is designed to adjust the proportional distribution of the laser input beam to the core region 14 and the ring region 16.

For processing a metallic workpiece W, a processing beam 18 is provided by the laser device and directed at the workpiece W. In this case, the processing beam 18 comprises a first laser beam 20 and a second laser beam 22. In this case, the first laser beam 20 and the second laser beam 22 are respective partial beams of a common laser beam that is provided by means of the multi-clad fiber. The first laser beam 20 is provided via the core region 14 and the second laser beam 22 via the ring region 16 of the 2-in-1 fiber. The laser beams 20, 22 are focused in the direction of the workpiece W by means of focusing optics, in this case the focusing lens 12. In order to process the metallic workpiece W, the processing beam 18 is moved relative to the workpiece W in a cutting direction 24 running into the image plane. The processing beam 18 is thus moved in the cutting direction 24 over 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 striking 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 designed to cut the workpiece W in its thickness direction 28. The workpiece W can be cut through across its entire thickness in the thickness direction 28 by means of the first laser beam 20. The second laser beam 22 is designed to produce a rounded cutting edge 30. In other words, when processing the workpiece W, the workpiece W is divided into a first workpiece part W1 and a second workpiece part W2 by means of the processing beam 18, wherein the second laser beam 22 ensures that the respective cutting edges 30 of the first workpiece part W1 and the second workpiece part W2 are rounded after processing.

If a 3-in-1 fiber is used as the multi-clad fiber, the processing beam 18 can comprise three laser beams with mutually different intensities, which are arranged next to one another in a line running perpendicular to the cutting direction 24 on the workpiece surface 26.

In 2 the area in which the workpiece W is cut by means of the processing beam 18 is shown enlarged. It can be seen particularly well that the first laser beam 20 and the second laser beam 22 are arranged next to one another in a line 32 running perpendicular to the cutting direction 24 on the unprocessed workpiece surface 26. The second laser beam 22 can have an annular image on the unprocessed workpiece surface 26, which encloses an image of the first laser beam 20, which can in particular be circular, on the outer circumference. Alternatively, the second laser beam 22 can only be arranged next to the first laser beam 20 and not completely enclose the image of the first laser beam 20. The second laser beam 22 is arranged next to the first laser beam 20 towards the resulting cutting edge 30, whereby the cutting edge 30 is rounded.

In 3 is one of the workpiece parts obtained by machining the workpiece W in a side view, in this case the first workpiece part W1. Here it can be seen that the first workpiece part W1 has the rounded cutting edge 30. Furthermore, a cutting surface 34 can be seen, which has been created by cutting the workpiece W by means of the first laser beam 20. The rounded cutting edge 30 adjoins the cutting surface 34. In 3 Furthermore, in the area of the cutting surface 34, a material web 36 can be recognized which was held in place when the workpiece W was cut and which was severed in order to divide the workpiece W after machining into the first workpiece part W1 and the second workpiece part W2. This material web 36 is a so-called nano joint which extends over less than half, in particular over less than a third, in particular over less than a quarter, in particular over less than a fifth of the thickness of the workpiece W. The material web 36 extends over a length of a stabilization region 38 of the workpiece W running in the cutting direction 24. In the cutting direction 24, respective cutting regions 40 of the workpiece Wan close before and after the stabilization region 38.

In the method for machining the metallic workpiece W, the first intensity of the first laser beam 20 in the stabilization region 38 is reduced in comparison to the cutting regions 40 in order to produce the material web 36. As a result, the workpiece W is completely cut through in its thickness direction 28 by means of the first laser beam 20 in the respective cutting regions 40 and only cut in the stabilization region 38. As a result, the material web 36 remains while the workpiece W is machined in the cutting direction 24 by means of the machining beam 18. The first workpiece part W1 and the second workpiece part W2 are held together by means of the material web 36 during this machining of the workpiece W by means of the machining beam 18, thereby preventing the workpiece parts W1, W2 from tilting relative to one another. After the workpiece W has been completely machined by means of the machining beam 18, the at least one material web 36 is severed in order to separate the first workpiece part W1 from the second workpiece part W2.

In order to keep a rounding radius constant along the entire cutting edge 30, it is provided that only the intensity of the first laser beam 20 is adjusted in the stabilization area 38 and the second intensity of the second laser beam 22 is the same in the stabilization area 38 and in the respective cutting areas 40. The second intensity of the second laser beam 22 thus remains constant during the entire processing of the workpiece W by means of the processing beam 18. While the workpiece W is being cut by means of the first laser beam 20, the rounding at the upper end of the cutting flanks is simultaneously produced by the action of the second laser beam 22, which has a lower second intensity than the first intensity. The first laser beam 20 thus serves as a core beam, which produces a separating cut, and the second laser beam 22 thus serves as a ring beam, which ensures melting and thus at least partial rounding of the workpiece surface or the upper cutting edge 30.

In the respective cutting regions 40, 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 to provide the initial value of the first intensity of the first laser beam 20, and a second portion of at most 20% of the laser power of the laser input beam can be coupled into the ring region 16 to provide the second intensity of the second laser beam 22. The first intensity of the first laser beam 20 is set at the transition between the cutting region 40 and the stabilization region 38 by adjusting the intensity of the laser input beam. In addition, to set the first intensity of the first laser beam 2ß by means of the beam splitting device, the portion of the laser input beam coupled into the core region 14 is adjusted to ensure that the second intensity of the second laser beam 22 is kept constant.

In 4 the first workpiece part W1 is shown in a perspective view in which the rounded cutting edges 30 along an inner contour and an outer contour of the first workpiece part W1 can be seen particularly well. In 5 the first workpiece part W1 is shown in a side view, wherein the produced and severed material web 36, which extends only over a partial area of the thickness of the workpiece part W1, can be seen particularly well.

The invention described is based on the knowledge that when rounding edges using an optical element, in particular a 2-in-1 fiber or a 3-in-1 fiber, workpiece parts that are held in the residual grid with a micro joint cannot be completely rounded. No rounding can be applied at the location of the micro joint, since the micro joint extends over the entire thickness of the component. If an edge rounding process were to be carried out at the location of the micro joint, the component, which is still fixed to the residual grid by means of a micro joint, would melt. The component would then become unusable and could only be repaired using very complex, time-consuming and costly This problem is solved by using nano joints instead of micro joints to hold components to the residual skeleton when machining the workpiece W. The cutting edge 30 can be rounded via the nano joint, the height of which extends in particular over no more than a third of the thickness of the workpiece. The nano joint extends in particular over a maximum of a quarter of the thickness of the workpiece W, in particular over a maximum of a fifth of the thickness of the workpiece W.

As part of the method, the cutting edge 30 is rounded with the 2-in-1 fiber or with the 3-in-1 fiber in a direct cut or during the cutting process. In this case, cutting is carried out with the laser power of the fiber core and thus by means of the first laser beam 20 and the cutting edge 30 is rounded with the laser power of the fiber cladding and thus by means of the second laser beam 22. In order to protect tilting parts, in particular the good part, from collisions with a cutting head of a processing device having the laser device for processing the metallic workpiece W, these workpiece parts W1, W2 are fixed with nano joints. These nano joints are found in particular in a lower third of the cutting surface 34 and are created during the cutting process by reducing the laser power. This allows an edge rounding to be applied above the nano joint.

If the laser power at the nano joint is reduced, for example by approximately 20%, then the laser power in the fiber cladding that is available for rounding is also reduced by 20%. This reduces the rounding radius of the cutting edge 30. To avoid this, the power reduction that is required to create the nano joint can be partially coupled into the fiber cladding of the optical waveguide 10. For this purpose, the wedge switch of the beam splitting device is changed in its switching position, whereby a higher percentage of power and thus a larger proportion of the laser input beam is coupled into the fiber cladding and thus into the ring region 16. In this case, the proportion of the laser power of the laser input beam that is coupled into the ring region 16 is only increased to such an extent that the rounding radius of the cutting edge 30 in the cutting region 40 and in the stabilization region 38 is the same and can therefore be kept constant over the entire cutting edge 30.

The following describes an example of processing a 5 mm thick structural steel as workpiece W as part of a high-speed cut, in this case a nitrogen cut, with 12 kW total laser power. The maximum available laser power is 12 kW. When using a 3-in-1 fiber, 10 kW can be coupled into the fiber core for cutting, which is approximately 83.3% of the total laser power. 2 kW of laser power is coupled into the fiber cladding for rounding, which is approximately 16.7% of the total laser power. To prevent the good part from tipping over and causing a collision with a laser cutting head of the processing device, a nano joint is set, particularly at one end of the cut. For this purpose, the laser power is reduced by 20% in the fiber core to 8 kW. In the fiber cladding, the laser power remains constant at 2 kW. This is achieved by a general reduction in the total laser power to 10 kW. By moving the wedge switch to a different position, 80% of the 10 kW total laser power is coupled into the fiber core and 20% is coupled into the fiber cladding.

Alternatively, the laser power for the fiber core and for the fiber cladding can come from two different laser beam sources. To create the material web 36, the laser power of the laser beam source whose laser beam is coupled into the fiber core can be reduced at the nano joint to be created.

The laser device comprises the 2-in-1 fiber or in particular the 3-in-1 fiber as an optical waveguide 10, whereby a large part, in particular at least 80% of the total laser power is coupled into the fiber core and is thus available for cutting the workpiece W. For the rounding process, a smaller part of the total laser power, in particular at most 20%, is coupled into the fiber cladding. In order to prevent the resulting workpiece parts from tilting, at least one nano joint is placed 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 approx. 20%.

Overall, the invention shows how collision-free edge rounding can be implemented.

LIST OF REFERENCE SYMBOLS

10

optical fiber

12

Focusing lens

14

Core area

16

Ring area

18

Processing beam

20

first laser beam

22

second laser beam

24

Cutting direction

26

Workpiece surface

28

Thickness direction

30

Cutting edge

32

line

34

Cutting surface

36

Material bridge

38

Stabilization area

40

Cutting area

W

workpiece

W1

first workpiece part

W2

second workpiece part

QUOTES INCLUDED IN THE DESCRIPTION

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Cited patent literature

• WO 2022037797 A1 [0002]
• DE 102019125103 A1 [0003]

Claims (10)

Method for machining a metallic workpiece (W), in which - a machining beam (18) is directed at the workpiece (W) and moved in a cutting direction (24) relative to the workpiece (W), wherein the machining beam (18) comprises a first laser beam (20) with a first intensity for cutting the workpiece (W) in a thickness direction (28) and a second laser beam (22) impinging on a workpiece surface (26) of the workpiece (W) next to the first laser beam (20) with a second intensity that is lower than the first intensity, whereby a rounded cutting edge (30) is produced by means of the second laser beam (22); and - for producing a material web (36) of the metallic workpiece (W), the first intensity of the first laser beam (20) is reduced in a stabilization region (38) of the workpiece (W) extending in the cutting direction (24) in comparison to at least one cutting region (40) of the workpiece (W) adjacent to the stabilization region (38) in the cutting direction (24), whereby the workpiece (W) is cut in the stabilization region (38) over at most a partial region of its thickness. Procedure according to Claim 1 , wherein the first laser beam (20) and the second laser beam (22) are arranged next to one another in a line (32) running perpendicular to the cutting direction (24) on the workpiece surface (26). Procedure according to Claim 1 or 2 , wherein the processing beam (18) is provided by means of a laser device which comprises - an optical waveguide (10) which has a core region (14) and at least one ring region (16), - a laser beam generation 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 between the core region (14) for generating the first laser beam (20) and between the at least one ring region (16) for generating the second laser beam (22). Procedure according to Claim 3 , wherein in the cutting region (40) a first portion of at least 80% of a 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 ring region (16). Procedure according to Claim 3 or 4 , wherein the first intensity of the first laser beam (20) is adjusted by adjusting the intensity of the laser input beam. Method according to one of the Claims 3 until 5 , wherein the first intensity of the first laser beam (20) is adjusted by adjusting a portion of the laser input beam coupled into the core region (14) by means of the beam splitting device. Method according to one of the Claims 3 until 6 , wherein the second intensity of the second laser beam (22) is the same in the stabilization region (38) and in the cutting region (40). Method according to one of the preceding claims, wherein the workpiece (W) is cut in the stabilization region (38) over at least half its thickness, in particular at least over two thirds of its thickness. Method according to one of the preceding claims, wherein the processing beam (18) comprises at least three laser beams with mutually different intensities, which are arranged next to one another in a line (32) running perpendicular to the cutting direction (24) on the workpiece surface (26). Laser device for processing a metallic workpiece (W) by means of a processing beam (18) in a method according to one of the preceding claims, which comprises a first laser beam (20) with a first intensity for cutting the workpiece (W) in a thickness direction (28) and a second laser beam (22) impinging on a workpiece surface (26) of the workpiece (W) next to the first laser beam (20) with a second intensity that is lower than the first intensity, whereby a rounded cutting edge (30) can be produced by means of the second laser beam (22), with - at least one laser beam generation unit that is set up to generate a laser input beam, - an optical waveguide (10) with 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 set up to provide the first laser beam (20), and the at least one ring region (16) is set up to provide the second laser beam (22), - a control device which is designed to control the laser device for adjusting the first intensity of the first laser beam (20).

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