Method for machining a metal workpiece, and laser device
Patent Information
- Application Number
- EP2023790321
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-10-21
- Filing Date
- 2023-10-16
- Publication Date
- 2025-08-27
AI Technical Summary
Existing methods for cutting metal workpieces often result in sharp edges, requiring additional processing steps for rounding, which is time-consuming and inefficient.
A method using a laser device with a processing beam comprising a first laser beam for cutting and a second laser beam with lower intensity for rounding, arranged next to or overlapping the first beam, to create a nano joint that allows for simultaneous cutting and rounding, reducing the need for separate edge rounding.
Enables fast and precise cutting with rounded edges, minimizing reworking and ensuring stable cutting edges without the need for subsequent edge rounding, thus enhancing processing efficiency.
Smart Images
Figure 1.1
Abstract
Description
[0001] METHOD FOR MACHINING A METAL WORKPIECE AND
[0002] LASER DEVICE
[0003] 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.
[0004] WO 2022 / 037797 A1 discloses a method for producing at least one workpiece part and a remaining workpiece from a workpiece using a laser beam emitted from a laser processing head. In this method, the workpiece is cut along a cutting line, forming cutting edges on the workpiece part and the remaining workpiece. Furthermore, the method involves modifying the workpiece in the form of a rounding while the workpiece part is connected to the remaining workpiece.
[0005] Furthermore, DE 102019 125 103 A1 discloses a method for laser cutting a workpiece. In this 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 temporally 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.
[0006] The object of the present invention is to provide a solution which enables particularly fast and precise cutting of a workpiece by means of a laser device, whereby sharp cutting edges are avoided.
[0007] The problem 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 drawings. Features, advantages, and possible embodiments presented 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, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.
[0008] The invention relates to a method for machining a metallic workpiece, which is in particular plate- or tubular in shape. In the method, it is provided that a machining beam is directed onto the workpiece and moved in a cutting direction relative to the workpiece. The machining beam is provided by a laser device. Directing the machining beam onto the workpiece means that the machining beam is provided by the laser device, is aligned with the workpiece, and impinges on the workpiece surface. 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 processing beam further comprises a second laser beam which, in addition to the first laser beam, impinges on a workpiece surface and has a second intensity which is lower than the first intensity of the first laser beam. The second laser beam creates a rounded cutting edge on the workpiece. The second laser beam can thus cause material in the workpiece to flow, rounding any cutting edges created when the workpiece is cut using the first laser beam. The amount of post-processing required for the workpiece can thus 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 eliminated.
[0009] 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 circumferentially encloses the image of the first laser beam. 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 annular 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 be adjacent to each other without overlap or spaced apart by a small separation gap.
[0010] The method further provides that, in order to create a material web on the metallic workpiece, the first intensity of the first laser beam is reduced in a stabilization region of the workpiece extending in the cutting direction compared 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 portion of its thickness. Leaving the at least one material web in place during cutting of the workpiece prevents two workpiece parts created by cutting the workpiece from tilting relative to one another during machining of the workpiece, whereby the workpiece can be cut with particular precision.If the workpiece parts were to tilt uncontrollably relative to each other during machining of the metal workpiece, the machining beam could deviate from a predetermined cutting line of the workpiece, causing the workpiece to be cut. Such cutting of the workpiece can be prevented by the at least one material web. After the cutting of the metal workpiece by means of the machining beam has been completed, the respective workpiece parts of the workpiece are cut by means of the at least one material web.
[0011] Material webs are held together. Subsequently, material webs of the workpiece that are held in advance are severed in order to separate the workpiece parts from one another. At least one of the severed workpiece parts can be a component that has thus been cut out of the metallic 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 it through. The severed process 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 skeleton 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 "nanojoint" only over a portion of the workpiece's thickness. Compared to so-called microjoints, which extend across the entire thickness of the workpiece, this use of the nanojoint as a material web has the advantage that the entire cutting edge can be rounded.
[0012] The workpiece is cut in the stabilization zone. The material web, which extends over only part of the thickness of the workpiece, is thus left in the stabilization zone. In the cutting zone, the workpiece is cut completely through its thickness. The cutting zone can adjoin the stabilization zone to the front or to the rear in the cutting direction. In particular, the workpiece comprises at least two cutting zones, one of which adjoins the stabilization zone to the front in the cutting direction and the other adjoins the stabilization zone to the rear in the cutting direction. The stabilization zone is thus delimited to the front and rear in the cutting direction by respective cutting zones. In particular, the workpiece can have a stabilization zone surrounded by respective cutting zones for each material web to be created.
[0013] In order to cut the metallic workpiece in a single process step using the processing beam and provide it with the rounded cutting edge, thereby creating at least one material web, 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 in place. The first intensity of the first laser beam thus has an initial value in the cutting direction in the cutting region, is reduced to a reduced value in the stabilization region adjacent in the cutting direction, and is increased again to the initial value in the further cutting region adjacent to the stabilization region in the cutting direction.The processing beam can thus be guided continuously along the workpiece surface in order to completely cut through the workpiece in the cutting area and to leave the material web in the stabilization area, creating a rounded cutting edge of the workpiece. Reworking the workpiece in several different processing steps, such as cutting the workpiece while leaving at least one material web and then separately rounding the edges, can thus be eliminated. The method thus enables particularly fast and extensive processing of the metallic workpiece. In one possible development of the invention, it is provided that the first laser beam and the second laser beam are arranged next to one another 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 side by side over the workpiece surface. As a result, the laser beams are arranged side by side in a plane spanned by the workpiece surface and perpendicular to the cutting direction. In particular, the laser beams can be arranged side by side 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. The second laser beam is thus arranged closer to a part of the workpiece that remains during cutting of the workpiece than the first laser beam, whereby cutting edges created when the workpiece is cut using the first laser beam can be rounded off by remelting and thus flowing of material.The cutting edges are rounded off immediately upon their creation by means of the second laser beam, whereby the risk of creating sharp cutting edges can be kept particularly low.
[0014] 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 fiber, a laser beam generation unit, and a beam splitting device. The laser device is, in particular, a fiber laser. The optical fiber can thus be a so-called fiber, in particular a multi-clad fiber, such as a 2-in-1 fiber or a 3-in-1 fiber. The optical fiber comprises a core region and at least one ring region. If the optical fiber is designed as a 2-in-1 fiber, then the optical fiber comprises the core region and a ring region surrounding the core region on the circumference. If the optical fiber is designed as a 3-in-1 fiber, then the optical fiber 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. The core region and the two ring regions are arranged concentrically to one another. The laser beam generation unit is configured 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 between the core region for generating the first laser beam and between 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.Thus, the intensity of the respective laser beams can be adjusted using the beam splitting device. As an alternative to the configuration 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 region of the optical fiber. By providing the respective separate laser beam generation units, the intensities of the laser beams of the processing beam can be individually controlled particularly easily.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 adjusted particularly precisely over an entire intensity range from 0 to 100% by splitting the one laser input beam.
[0015] In this context, it can be provided, in particular, that in the cutting area, a first portion of at least 80% of the 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 annular area. This ensures that the workpiece is reliably severed across its entire thickness in the respective cutting area by means of the first laser beam, and that the respective cutting edges of the workpiece are rounded by means of the second laser beam without causing excessive flow of the workpiece material.
[0016] In this context, a further possible embodiment of the invention may provide for the first intensity of the first laser beam to be adjusted by adjusting the intensity of the laser input beam. In other words, the intensity of the laser input beam is modified by the laser beam generation unit, whereby the intensity of the portion of the laser input beam that is coupled into the core region for generating the first laser beam by the beam splitting device is adjusted. By adjusting the intensity of the laser input beam, the intensity of the first laser beam can be modified particularly easily.
[0017] 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. Thus, the splitting of the laser input beam between the core region and the at least one annular region can be adjusted to adjust the intensity of the first laser beam.
[0018] In a further possible embodiment of the invention, the second intensity of the second laser beam is the same in the stabilization region and in the cutting region. This ensures that the rounding radius at the cutting edge of the metallic workpiece is constant in all regions along the cutting direction. Differences in the rounding radius between regions of the workpiece in which the material web is provided and regions in which no material web is provided can thus be avoided. This makes it possible to achieve a particularly evenly rounded cutting edge on the workpiece.
[0019] In particular, to adjust the intensity of the first laser beam, both the intensity of the laser input beam can be adjusted and the distribution of the laser input beam can be divided between the core region and the at least one annular 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 distribution 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 zone compared to the cutting zones. To avoid this, the power reduction of the laser input beam, which is required in the stabilization zone to reduce the intensity of the first laser beam for generating the material web, is partially coupled into the ring zone of the optical fiber. Thus, with the beam splitting device, a larger portion of the laser input beam is coupled into the ring zone when machining the workpiece in the stabilization zone than into the cutting zone.However, the portion of the laser input beam which is coupled into the ring region during machining of the stabilization region of the workpiece is only increased to such an extent that the power of the second laser beam is the same in the stabilization region and in the cutting region and thus essentially constant during machining of the metallic workpiece.
[0020] In a further possible embodiment of the invention, it is provided that the workpiece is cut in the stabilization region over at least half its thickness, in particular at least over 2 / 3 of its thickness. The workpiece can be cut in the stabilization region, in particular over at least 3 / 4 of its thickness, in particular over at least 4 / 5 of its thickness. The resulting material web 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 produced material web, but the more force is required to separate workpiece parts created during machining of the workpiece.The lower the height of the created material web, the less mass of material web residue that may need to be removed from the respective workpiece parts after the material web has been severed. Cutting the workpiece in the stabilization area at least half the thickness of the workpiece ensures that a reliably rounded cutting edge can be provided using the second laser beam.
[0021] In a further possible embodiment of the invention, 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. To generate the processing beam with the at least three laser beams, the laser device can be used which has the optical waveguide designed as a 3-in-1 fiber. Alternatively, the respective laser beams can be provided by separate laser devices, with a separate laser device being provided for each laser beam.By providing three laser beams with different intensities, the workpiece can be cut using the first laser beam, while the second and third laser beams, which also have different intensities, can produce a rounded cutting edge of the workpiece. By providing the second and third laser beams with different intensities, a rounded contour of the cutting edge can be specified with particular precision.
[0022] If the optical fiber comprises the core region and two further ring regions, then when the laser input beam is coupled into both the core region and both ring regions, 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 strikes the workpiece surface next to the first laser beam and the second laser beam when the processing beam is aligned with 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 therefore have the first laser beam in the center, 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.
[0023] The invention further relates to a laser device for processing a metallic workpiece by means of a processing beam in a method as already described in connection with the method according to the invention. The workpiece can be supported, for example, on a workpiece support during the processing process. The laser device can, for example, be part of a laser cutting system, such as a flatbed laser cutting system or a tube laser cutting system. 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 which impinges on a workpiece surface of the workpiece next to the first laser beam and has a second intensity that is lower than the first intensity, whereby a rounded cutting edge can be produced by means of the second laser beam.The laser device comprises at least one laser beam generation unit configured to generate a laser input beam. Furthermore, the laser device comprises an optical waveguide having a core region and at least one ring region. When 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 ring region is configured to provide the second laser beam. Furthermore, the laser device comprises a control device configured to control the laser device to adjust the first intensity of the first laser beam. The laser device can be configured 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 fiber 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 particularly designed 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 by means of the processing head.
[0024] The laser device can further comprise a beam splitting device arranged between the laser beam generation unit and the optical waveguide, in particular the multi-clad fiber. The beam splitting device is configured to split the laser input beam provided by the laser beam generation unit into respective regions of the multi-clad fiber. 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, wherein the first laser beam is coupled into the core region of the multi-clad fiber and the second laser beam is coupled into the ring region of the multi-clad fiber.If the processing beam comprises more than two laser beams, the multiclad fiber can have several, preferably concentrically arranged, ring regions, 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 multiclad fiber.
[0025] The laser device enables processing of the workpiece in a single step, wherein 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 to hold together respective workpiece parts created by cutting the workpiece. Further features of the invention can be derived 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 respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention.
[0026] The drawing shows:
[0027] Fig. 1 is a schematic side view of a laser device by means of which a metallic workpiece is processed;
[0028] Fig. 2 is a schematic sectional view of the metallic workpiece machined by means of a machining beam of the laser device;
[0029] Fig. 3 is a schematic side view of the machined metallic workpiece;
[0030] Fig. 4 is a perspective view of the machined metallic workpiece; and
[0031] Fig. 5 a side view of the machined metallic workpiece.
[0032] Identical or functionally equivalent elements are provided with the same reference numerals in the figures.
[0033] Fig. 1 shows individual components of a laser device. Thus, Fig. 1 shows an optical waveguide 10 and a focusing lens 12 of a focusing optics system. The focusing lens 12 is configured 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 configured to generate a laser input beam. Furthermore, the laser device comprises the optical waveguide 10 shown in Fig. 1, which is embodied as a multi-clad fiber, specifically as a 2-in-1 fiber. This 2-in-1 fiber comprises a core region 14 and an annular region 16 circumferentially surrounding the core region 14.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 circumferentially encloses the core region 14 and the outer ring region circumferentially encloses the inner ring region. 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 configured to adjust the proportional splitting of the laser input beam between the core region 14 and the ring region 16.
[0034] For processing a metallic workpiece W, a processing beam 18 is provided by the laser device and directed onto 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 provided by 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. For processing the metallic workpiece W, the processing beam 18 is moved relative to the workpiece W in a cutting direction 24 extending 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 impinging 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 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 configured to produce a rounded cutting edge 30.In other words, during machining of 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 ensures that the respective cutting edges 30 of the first workpiece part W1 and the second workpiece part W2 are rounded after machining. If a 3-in-1 fiber is used as the multi-clad fiber, the machining 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.
[0035] In Fig. 2, the area in which the workpiece W is cut by means of the processing beam 18 is shown in an enlarged manner. It can be seen particularly clearly 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. In this case, the second laser beam 22 can have an annular image on the unprocessed workpiece surface 26, which image 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 be arranged only next to the first laser beam 20 and not completely enclose 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 towards the resulting cutting edge 30, whereby the cutting edge 30 is rounded.
[0036] Fig. 3 shows a side view of one of the workpiece parts obtained by machining the workpiece W, 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 was created by cutting the workpiece W using the first laser beam 20. The rounded cutting edge 30 adjoins the cutting surface 34. In Fig. 3, in the region of the cutting surface 34, a material web 36 can be seen, which was held in place when the workpiece W was cut and which is 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 W adjoin 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 is reduced in the stabilization region 38 compared 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 is only incised 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 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.
[0037] 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 region 38, and the second intensity of the second laser beam 22 is the same in the stabilization region 38 and in the respective cutting regions 40. The second intensity of the second laser beam 22 thus remains constant throughout 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, the rounding at the upper end of the cutting flanks is simultaneously created 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 creates a separating cut, and the second laser beam 22 thus serves as a ring beam, which ensures melting and thus at least partially rounding of the workpiece surface or the upper cutting edge 30.
[0038] 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 output 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 28, the portion of the laser input beam coupled into the core region 14 is adjusted by means of the beam splitting device to ensure that the second intensity of the second laser beam 22 is kept constant.
[0039] Fig. 4 shows the first workpiece part W1 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 clearly. Fig. 5 shows the first workpiece part W1 in a side view, in which the created and severed material web 36, which extends only over a partial area of the thickness of the workpiece part W1, can be seen particularly clearly.
[0040] The invention described is based on the finding that when edge rounding using an optical element, in particular a 2-in-1 fiber or a 3-in-1 fiber, workpiece parts which are held in the residual skeleton with a micro joint cannot be completely rounded. No rounding can be applied at the location of the micro joint because the micro joint extends across the entire component thickness. 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 skeleton by means of a micro joint, would melt. This would render the component unusable and could only possibly be saved through very complex, time-consuming and costly remachining. This problem is solved by using nano joints instead of micro joints to hold components to the residual skeleton during machining of 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 one-third of the thickness of the workpiece. The nano joint extends in particular over a maximum of one-quarter of the thickness of the workpiece W, in particular over a maximum of one-fifth of the thickness of the workpiece W.
[0041] Within the scope of the method, the rounding of the cutting edge 30 takes place with the 2-in-1 fiber or with the 3-in-1 fiber in direct cutting or during the cutting process. Here, 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 finished 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.
[0042] If the laser power at the nano joint is reduced, for example, by approximately 20%, the laser power in the fiber cladding available for rounding is also reduced by 20%. This reduces the rounding radius of the cutting edge 30. To circumvent this, the power reduction required to create the nano joint can be partially coupled into the fiber cladding of the optical fiber 10. For this purpose, the wedge switch of the beam splitting device is changed in its switching position, whereby a higher percentage of the power and thus a larger portion of the laser input beam is coupled into the fiber cladding and thus into the ring region 16.In this case, the portion of the laser power of the laser input beam which 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 thus be kept constant over the entire cutting edge 30.
[0043] The following describes an example of machining a 5 mm thick structural steel workpiece W during a high-speed cut, in this case a nitrogen cut, with a total laser power of 12 kW. 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 represents approximately 83.3% of the total laser power. 2 kW of laser power is coupled into the fiber cladding for rounding, which represents approximately 16.7% of the total laser power. To prevent the workpiece from tipping over and causing a collision with a laser cutting head of the processing device, a nano joint is created, particularly at one cut end. 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% into the fiber cladding. Alternatively, the laser power for the fiber core and 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.
[0044] The laser device comprises the 2-in-1 fiber or in particular the 3-in-1 fiber as optical waveguide 10, wherein a large portion, 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 portion of the total laser power, in particular at most 20%, is coupled into the fiber cladding. To prevent tilting of the resulting workpiece parts, at least one nano joint is placed at the end of the cutting contour or in the center of the cutting contour by reducing the laser power of the fiber core by approximately 20%. Overall, the invention shows how collision-free edge rounding can be implemented.
[0045] LIST OF REFERENCE SYMBOLS
[0046] 10 optical fibers
[0047] 12 Focusing lens
[0048] 14 Core area
[0049] 16 ring area
[0050] 18 Processing beam
[0051] 20 first laser beam
[0052] 22 second laser beam
[0053] 24 Cutting direction
[0054] 26 Workpiece surface
[0055] 28 Thickness direction
[0056] 30 cutting edge
[0057] 32 Line
[0058] 34 cutting surface
[0059] 36 Material bridge
[0060] 38 Stabilization area
[0061] 40 cutting area
[0062] W workpiece
[0063] W1 first workpiece part
[0064] W2 second workpiece part
Claims
PATENT CLAIMS 1. A method for machining a metallic workpiece (W), in which a machining beam (18) is directed onto 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) having 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) in addition to the first laser beam (20) and having a second intensity which 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) compared 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) at most over a partial region of its thickness.; 2. Method 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).
3. Method 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 the at least one ring region (16) for generating the second laser beam (22). The method 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). The method according to claim 3 or 4, wherein the first intensity of the first laser beam (20) is set by adjusting the intensity of the laser input beam. The method according to one of claims 3 to 5, wherein the first intensity of the first laser beam (20) is set by adjusting a portion of the laser input beam coupled into the core region (14) by means of the beam splitting device. The method according to one of claims 3 to 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 over at least 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 machining a metallic workpiece (W) by means of a machining 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 which is lower than the first intensity, whereby a rounded cutting edge (30) can be produced by means of the second laser beam (22). - at least one laser beam generation unit which is designed 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 designed to provide the first laser beam (20) and the at least one ring region (16) is designed 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).