Techniques for producing edge rounds

Abstract

The invention relates to a method for machining a metal workpiece (W) by means of a machining beam (20), which comprises a first laser beam (22) and a second laser beam (24) arranged at least partially next to the first laser beam (22), and which comprises a process gas beam. The method comprises the following steps: cutting the workpiece (W) by guiding the machining beam (20) along a cutting profile and using a first set of machining parameters; and finishing at least one cutting edge of the workpiece (W) produced during the cutting by guiding the machining beam (20) along a finishing profile, which runs corresponding to or parallel to the cutting profile, and using a second set of machining parameters. The invention further relates to a device for carrying out the method and to a metal workpiece which can be produced by means of the method.

Description

Technical Field

[0001] The invention relates to the field of laser processing of (especially plate-shaped or tubular) metal workpieces. In particular, the invention relates to a technique for finishing workpiece edges by means of a laser beam. Background Art

[0002] Methods for finishing the cut edges of metal workpieces are known from the prior art, in which a laser beam is used in order to irradiate the contour of a workpiece portion at least partially cut out of the workpiece with the aid of the laser beam and thereby cause the edge characteristics to change. For example, document WO 2020 / 173970 A1 describes a method in which, in a first processing step, a cutting gap is produced in the workpiece by means of laser cutting, and in a second processing step, the cutting gap is again at least partially swept over (abfahren) by means of other processing parameters of the laser cutting system in order to modify the cut edge. Document DE 10 2019 125 103 A1 describes a method in which roughing (in particular cutting to produce a cut edge) and finishing (in particular rounding and / or chamfering the produced cut edge) are simultaneously performed using a processing laser beam with different energy intensity regions. Summary of the invention

[0003] The invention is based on the object of improving the prior art, in particular to improve the possibilities for producing roundings at the transition between the workpiece surface and the cut flanks of metallic workpiece parts cut by means of laser beam cutting technology.

[0004] In order to solve the basic task of the present invention, a method for processing a metal workpiece by means of a processing beam is provided. 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 also (partially) overlap. In the plane of the workpiece surface, the images (Abbildung) of the first laser beam and the second laser beam are adjacent to each other, preferably do not overlap, or are separated from each other by a very small separation gap. The processing beam also includes a process gas beam (Prozessgasstrahl). In particular, nitrogen, a gas mixture including nitrogen, or another inert gas or gas mixture can be used as a process gas. Preferably, the process gas beam can be generated by means of a processing nozzle of a processing head and directed to the workpiece to be processed together with at least one of the laser beams. The workpiece can be a plate-shaped or tubular workpiece, which is preferably made of steel material.

[0005] The method comprises in a first step cutting a workpiece by directing a machining beam along a cutting contour and using a first set of machining parameters.

[0006] In a second step, in particular following the first machining step, the method comprises finishing at least one cut edge of the workpiece produced during cutting by guiding the machining beam along a finishing contour corresponding to or extending parallel to the cutting contour and using a second machining parameter set.

[0007] The first set of processing parameters and the second set of processing parameters can differ from one another, for example, at least with regard to the laser power used, the gas pressure used and / or the feed used.

[0008] The method provided allows the workpiece to be cut first in one operation and the resulting cut edges to be rounded in a targeted manner afterwards. Compared to the prior art, the method provided allows larger rounding radii (0.5 mm or more) to be achieved with a very good rounding quality. In particular, roundings with a continuous surface transition to the workpiece surface and to the cut side surface (i.e. without material protrusions) can be produced, which preferably have a uniform rounding radius (i.e. without flat roundings).

[0009] According to a preferred variant, the first laser beam can have a higher intensity than the second laser beam. Intensity is to be understood as the power of the respective laser beam per unit area. For example, the intensity ratio in the common focal plane of the laser beams can play a decisive role. Intensity can be understood in particular as the average intensity of the individual laser beams over the area in their focal plane. The area of ​​the laser beam in its focal plane can be determined, for example, by means of the 80% method or the second moment method.

[0010] The second laser beam can preferably be directed coaxially to the first laser beam toward the workpiece, wherein the second laser beam preferably has a closed beam contour, in particular an annular beam contour, so that the second laser beam surrounds the first laser beam.

[0011] In particular, the first laser beam and the second laser beam can be sub-beams of a common laser beam. The total power of the laser beam is preferably distributed to the sub-beams in any proportion. For example, the applicant's WO 2011 / 124671 A1 describes a technique for variably dividing a laser beam into a plurality of sub-beams.

[0012] It is understood that the processing beam can also comprise more than two laser beams, wherein preferably two adjacent (sub-)laser beams have different intensities.

[0013] In the method according to the invention, the first set of processing parameters can include the simultaneous use of the first laser beam and the second laser beam. In other words, it can be provided that the first laser beam and the second laser beam are switched on (or activated) when cutting the workpiece. According to an alternative variant, it is also conceivable that only the first laser beam is activated during cutting.

[0014] The second processing parameter set can in particular include using the first laser beam without using the second laser beam. That is, the second laser beam can be turned off (or not activated) during the finishing of the cut edge. However, alternatively or additionally, the second laser beam can also be activated during the finishing process.

[0015] The finishing contour swept by the machining beam during finishing can have an offset in the direction of the cut edge to be finished relative to the cutting contour, which is between 0.1 mm and 1 mm. Due to the offset in the direction of the cut edge to be finished, the energy required for modifying the cut edge can be introduced more specifically into the desired workpiece area. In this way, the efficiency of the method can be increased.

[0016] According to a preferred variant of the method, during cutting, by irradiating the workpiece with the aid of a second laser beam, a rounding with a first radius or a chamfer with a chamfer height can be produced at the upper end of the cut edge to be finished, wherein during finishing, the rounding or the chamfer is increased to a rounding with a second radius, wherein the second radius is greater than the first radius or the chamfer height.

[0017] During cutting, a chamfer that is rounded at its end, i.e. a hybrid shape between a chamfer and a chamfer, can also be produced. The production of the chamfer and / or chamfer during cutting preferably includes material removal. In other words, it can be provided that the edge is not only melted by the second laser beam, but workpiece material is also removed by means of the process gas jet through the cutting gap. Since material removal has already taken place in the first method step, no material needs to be removed during the finishing process and in order to produce a larger chamfer, or only to a lesser extent. By removing material, a material protrusion of the chamfer relative to the workpiece surface and the cut side is generally avoided.

[0018] The first rounding radius (or chamfer height) can be, for example, between 0.1 mm and 0.7 mm. The second rounding radius increased in the finishing step can be, for example, between 0.2 mm and 1.5 mm.

[0019] The second processing parameter set can predetermine a process gas pressure that is lower than the process gas pressure according to the first parameter set. For example, during the finishing process, the pressure in the chamber (Kesselraum) of the processing nozzle used for processing can be an overpressure of up to 0.3 bar (preferably up to 0.1 bar) relative to the ambient pressure. The lower gas pressure used helps to reduce turbulence during the finishing process and helps to produce a particularly smooth surface along the chamfer. In this way, a particularly uniform and smooth chamfer can be produced. An excessively strong gas jet can deform the chamfer. In addition, the gas consumption can be kept low by the lower pressure during the finishing process.

[0020] Advantageously, it can be provided that according to the first set of machining parameters, the distance between the end face of the nozzle, through which the machining beam is directed toward the workpiece, and the workpiece surface is smaller than in the case according to the second set of machining parameters. In other words, the distance between the nozzle and the workpiece during finishing machining is greater than the distance between the nozzle and the workpiece during workpiece cutting.

[0021] Preferably, in the method according to the invention, in a first step, a workpiece portion is cut out of the workpiece along the cutting contour using a first set of machining parameters until at least one remaining material bridge (Materialsteg) connects the workpiece portion to the remainder of the workpiece or to an adjacent workpiece portion of the workpiece. Furthermore, in a second step, the cut edge of the workpiece portion can be finished using a second set of machining parameters. Thus, the cut edge produced can be swept again using the same machining head with changed parameters. In a subsequent third step, the at least one material bridge can be cut off.

[0022] For example, the cutting can also be achieved by means of a machining beam, for example using a first set of machining parameters. Alternatively, the at least one material bridge can also be removed mechanically, in particular by pressing, chiseling or vibrating the workpiece portion out of the surrounding workpiece remainder (or residual grid) of the workpiece, or by bending or vibrating a plurality of workpiece portions held together by the material bridge. The material bridge can extend over the entire thickness of the workpiece as a so-called "microjoint" or can also have a reduced height (so-called "nanojoint"). The advantage of using a nanojoint is that the cut edge can be finished along the entire periphery of the workpiece portion during the finishing process. In addition, the material bridge can be constructed as a so-called "microweld", i.e. a welding point, preferably located at the upper end of the cutting gap, which holds the parts of the workpiece separated by the cutting gap (workpiece parts and / or workpiece remainders or residual grid parts) together.

[0023] In order to achieve the object underlying the present invention, a device for machining a metal workpiece by means of a machining beam is also provided. The machining beam comprises a first laser beam and a second laser beam arranged at least partially adjacent to the first laser beam, and also a process gas beam.

[0024] The device comprises a workpiece support for supporting the workpiece during the machining process. In addition, the device comprises at least one laser beam source for providing laser radiation for the first laser beam and the second laser beam. Preferably, the laser beam source can be a solid-state laser, for example a fiber laser with one or more fiber laser modules, or a disk laser, or a diode laser. The device also includes a process gas supply device for providing process gas and a machining head with focusing optics, wherein the machining head is configured to direct the machining beam to the workpiece surface. The device comprises a multi-clad optical fiber, which has a core region and at least one annular region surrounding the core region, wherein the multi-clad optical fiber is configured to guide (or transmit) the first laser beam in the core region and the second laser beam in the annular region from the laser beam source to the machining head. The device also comprises a control device, which is configured to control the device for performing the method according to one of the above-mentioned variants.

[0025] The device can be, in particular, a laser cutting system, for example a flat-plate laser cutting system or a tube laser cutting system.

[0026] The device according to the invention can preferably include a beam splitting device, which is arranged between the laser beam source and the multi-clad optical fiber and is designed to split the laser input beam provided by the laser beam source into a first laser beam and a second laser beam, wherein the first laser beam can be coupled into the core region of the multi-clad optical fiber and the second laser beam can be coupled into the ring region of the multi-clad optical fiber by means of the beam splitting device. As already mentioned above, the processing beam can also include more than two laser beams. Correspondingly, the multi-clad optical fiber can also have a plurality of (preferably concentrically arranged) ring regions, which are each designed for guiding the corresponding (sub-) laser beams. The beam splitting device can, for example, include a so-called wedge splitter, which is arranged in the beam path of the laser input beam and couples parts of the laser input beam into the core region and / or the ring region of the multi-clad optical fiber in a controllable manner by lateral displacement relative to the laser input beam. The principle of beam splitting by means of a wedge-shaped splitter is described, for example, in document WO 2011 / 124671 A1 or also in the applicant's German patent application with official document number 10 2022 110 078.2.

[0027] According to another aspect of the present invention, a metal workpiece is provided. The workpiece comprises a substrate having an upper side and a lower side opposite to the upper side. The substrate further comprises an edge extending laterally along an outer contour or an inner contour of the substrate. The substrate has a rounding at the transition between the upper side and the edge along at least a portion of the outer contour and / or the inner contour, the rounding extending at a height of at least 0.2 mm (preferably at least 0.5 mm), wherein the substrate has a smaller surface roughness along the rounding than along the rest of the edge.

[0028] The edge surface of the base body preferably extends substantially perpendicularly to the surface of the base body and can in particular correspond to the cutting side surface.

[0029] The workpiece according to the invention can preferably have a rounding with a height of 0.2 mm to 1.5 mm. The height of the rounding corresponds to the rounding radius. Furthermore, the rounding can be characterized in that it has no material overhangs that protrude upwards from the workpiece surface or that protrude laterally beyond the edge surface. In other words, the rounding can have a continuous transition on the workpiece surface and on the edge surface. This can improve the tactile feel of the upper end of the workpiece edge. When the workpiece is coated with a coating agent (e.g. paint), the uniformity of the coating on the workpiece edge can be improved by the rounded, soft transition. In addition, the risk of injury when handling the workpiece (or workpiece parts) is reduced by the smooth rounding.

[0030] The surface roughness along the rounding can preferably be at most Rz 30.

[0031] The workpiece can be produced particularly efficiently by means of the method according to one of the above-described variants. Thus, the workpiece can be at least partially cut out of a (for example plate-shaped) workpiece as a workpiece part in a process step and can be finished in the region of the resulting cut edge to form an advantageous edge rounding. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following description of the preferred embodiments in conjunction with the accompanying drawings is used to illustrate the present invention in more detail.

[0033] In the attached picture:

[0034] Figure 1a to Figure 1b A diagram is shown for illustrating a processing method according to the invention according to a variant;

[0035] Figure 2 Another diagram for illustrating the processing method according to the present invention is shown;

[0036] Figure 3 a schematic front view showing a cut edge of a workpiece or a workpiece part according to the invention; and

[0037] Figures 4 to 5 A diagrammatic representation of a workpiece portion according to the invention is shown. DETAILED DESCRIPTION

[0038] Next, based on Figure 1a and Figure 1b The processing method according to the invention is described by way of example. A component for laser processing a metal workpiece W is schematically shown. A processing beam 20 comprising a first laser beam 22, a second laser beam 24 and a process gas beam (not shown in the figure) is directed to the surface of the workpiece W by means of a processing nozzle (also not shown). According to the example shown, the first laser beam 22 and the second laser beam 24 are sub-beams of a common laser beam, which is provided by means of a multi-clad optical fiber, which is a 2-in-1 optical fiber 10 here, wherein the first sub-beam 22 is provided by the core region 12 of the 2-in-1 optical fiber 10 and the second sub-beam 24 is provided by the annular region of the 2-in-1 optical fiber 10. These laser beams 22 and 24 are focused in the direction of the workpiece W by means of focusing optics (which are schematically shown here by a focusing lens 30) and are directed to the workpiece surface together with the process gas via the processing nozzle. In order to process the workpiece W, the processing beam is moved relative to the workpiece surface using predetermined processing parameters.

[0039] In a first method step, the workpiece W is cut using a first parameter set, wherein the workpiece part W1 and the workpiece remainder W2 are locally separated from one another by a cutting gap. During the cutting, a rounding 42a or a chamfer 42b is simultaneously produced at the upper end of the cut side surface by the action of a second laser beam 24, which has a lower intensity than the first laser beam 22 (see Figure 2 , step a)). During the production of the rounding 42a or the chamfer 42b, material is removed under the action of a process gas directed at a high pressure toward the workpiece W. It may be preferred that the rounding 42a has a flat shape similar to a chamfer.

[0040] In a second method step, the generated cut edge is again scanned by means of the machining beam 20 using a second parameter set (see Figure 1b and Figure 2 b) In this case, the rounding 42 a or chamfer 42 b produced during cutting is enlarged, so that a high-quality final rounding 44 is obtained.

[0041] For example, according to the present invention, a plate-shaped workpiece W made of CrNi steel and having a thickness of 2 mm can be processed on a 2D laser flatbed machine with a laser power of 12 kW by means of this method. Here, the first method step of cutting can first be implemented using a first set of processing parameters. Here, a beam splitter located in the laser input beam can couple the laser power simultaneously into the core region 12 and the ring region 14 of the two-in-one optical fiber. The core beam (first laser beam 22) produces the separating cut, and the ring beam (second laser beam 24) is responsible for melting and thus at least partially for the rounding 42a of the workpiece surface (or the upper cutting edge), wherein material removal also occurs in the region of the rounding 42a. For cutting, by way of example, a first sub-beam 22 with a laser power of approximately 8 kW is coupled into the core region 12 with a diameter of 100 μm. A second sub-beam 24 with a laser power of approximately 4 kW is coupled into the ring region 14 with an outer diameter of 400 μm. The imaging ratio is 2.1. The focal diameter (of the second laser beam 24) is 840 μm. The feed rate is 40 m / min. The focal position is located in the region of the workpiece surface or at a short distance below the surface, for example 0.5 mm below the workpiece surface. Nitrogen is used as cutting gas. At a distance of 4 mm between the nozzle and the workpiece surface, the cutting gas pressure is 23 bar (overpressure compared to the ambient pressure). The machining nozzle (or cutting nozzle) has a diameter of 2.3 mm. The rounding 42 a produced during cutting has a height of approximately 0.2 mm.

[0042] Subsequently, the second method step of finishing is implemented using the second processing parameter set. The laser beam can preferably be turned off between cutting and finishing, and the cutting head is moved back to the starting point of cutting. In order to finish or round the cut edge, the cutting head can be offset by 0.2 mm relative to the cutting contour in the direction of the cut edge to be finished (qualified part contour), and the cut edge is re-scanned with the processing parameters changed according to the second processing parameter set. Here, when the focus diameter of the first (sub) laser beam 22 is 210 μm and the laser power is 370 W, the distance between the nozzle and the workpiece W can be 5 mm. Preferably, the laser power used in the finishing process can also be significantly smaller than that in the cutting case. For finishing, the second (sub) laser beam 24 can be turned off according to the exemplary variant described. The process gas pressure is, for example, 0.2 bar, and the focal plane of the first laser beam 22 can be located about 2 mm above the nozzle end face (i.e., in the nozzle body). The feed speed can be 2.2 m / min. The feed rate according to the second processing parameter set can also be significantly lower than the feed rate according to the first processing parameter set. The quality of the rounding can be improved. The rounding produced with the above processing parameters can have a rounding radius of about 0.5 mm.

[0043] exist Figure 2 A variant of the method according to the invention is shown in FIG. 4 , in which a chamfer 42 b is produced during cutting (see step a)). In the case of producing a chamfer 42 b, the chamfer 42 a at the same height (see step b) is not necessarily the same as in the case of producing a chamfer 42 b. Figure 1a ) compared to the material removal is maximized. The size or radius or height of the final rounding 44 depends primarily on the material removal at the rounding location during cutting. During the finishing process in the second method step (see Figure 2 In step b)), preferably no material removal occurs. Therefore, the process gas pressure can be selected to be significantly lower than during cutting, thereby improving the shape and surface quality of the rounding.

[0044] exist Figure 2 The figure also shows that the machining jet 20 is displaced relative to the cutting contour in the direction of the cut edge to be finished for finishing. In order to improve the process gas coverage, in particular during the finishing step, a nozzle with the largest possible nozzle diameter can be used for the entire machining process. For example, when using a nozzle with an outlet diameter of 10 mm, the cutting gas pressure can be reduced compared to the above example. In addition, the protective gas coverage of the machining area can be improved when the cut edge is rounded in the finishing step, and in this way the formation of oxidation color (Anlauffarben) on the workpiece surface can be prevented.

[0045] exist Figure 3 , a front view of a workpiece edge of a workpiece or workpiece part W1 according to the invention is shown. The workpiece part W1 is not completely cut out in the first method step and is connected to the surrounding workpiece remainder or adjacent workpiece parts via a material bridge, here in the form of a nano-connection 50. Due to the reduced height of the nano-connection 50, a rounding 44 can be produced along the entire workpiece periphery in the second method step, and then the nano-connection 50 can be cut off to separate the workpiece part W1. The surface of the workpiece part W1 along the rounding 44 has a roughness of at most Rz30.

[0046] exist Figure 4 and Figure 5 The workpiece parts W1 according to the present invention are shown in Figure 5 Diagram and basis Figure 3 The schematic diagram of is roughly corresponding to that of. Figure 4 and Figure 5 In the figure, the smooth surface along the generated roundings 44 can be seen, which (see Figure 4 ) extends along the inner contour and the outer contour of the workpiece part W1.

Claims

1. A method for machining a metal workpiece (W) by means of a machining beam (20), the machining beam comprising a first laser beam (22) and a second laser beam (24) arranged at least partially adjacent to the first laser beam (22), and the machining beam comprising a process gas beam, the method comprising the following steps: cutting the workpiece (W) by directing the machining beam (20) along a cutting contour and using a first set of machining parameters; as well as At least one cut edge of the workpiece (W) produced during the cutting is finish-machined by guiding the machining beam (20) along a finishing machining contour corresponding to the cutting contour or extending parallel to the cutting contour and using a second set of machining parameters.

2. The method according to claim 1, in, The first laser beam (22) has a higher intensity than the second laser beam (24).

3. The method according to claim 1 or 2, in, The second laser beam (24) is directed toward the workpiece (W) coaxially with the first laser beam (22); and The second laser beam (24) preferably has a closed beam contour, in particular an annular beam contour, so that the second laser beam (24) surrounds the first laser beam (22).

4. The method according to claim 1, in, The first set of processing parameters includes using the first laser beam (22) and the second laser beam (24) simultaneously.

5. The method according to any one of the preceding claims, in, The second set of processing parameters includes using the first laser beam (22) and not using the second laser beam (24).

6. The method according to any one of the preceding claims, in, The finishing contour has an offset relative to the cutting contour in the direction of the cutting edge to be finished, the offset being between 0.1 mm and 1 mm.

7. The method according to any one of the preceding claims, in, During the cutting, a rounding (42a) having a first radius or a chamfer (42b) having a chamfer height is generated at the upper end of the cut edge to be finished by irradiating the workpiece (W) with the aid of the second laser beam (24); and During the finishing process, the rounding (42a) or the chamfer (42b) is increased to a rounding (44) having a second radius, wherein the second radius is greater than the first radius or the chamfer height.

8. The method according to any one of the preceding claims, in, The second set of process parameters predetermines a process gas pressure which is lower than the process gas pressure according to the first set of process parameters.

9. The method according to any one of the preceding claims, in, The machining beam (20) is directed toward the workpiece (W) through a nozzle of a machining head; and Wherein, according to the first processing parameter set, the distance between the nozzle end face and the workpiece surface is smaller than that according to the second processing parameter set.

10. The method according to any one of the preceding claims, in, In a first step, a workpiece portion (W1) is cut out from the workpiece (W) along the cutting contour to at least one remaining material bridge (50), the at least one material bridge connecting the workpiece portion (W1) to a workpiece remainder (W2) or an adjacent workpiece portion of the workpiece (W), using the first set of machining parameters; wherein, in a second step, the cut edge of the workpiece part (W1) is subjected to finishing machining using the second machining parameter set; and Therein, in a third step, the at least one material bridge (50) is severed.

11. A device for machining a metal workpiece (W) by means of a machining beam (20), the machining beam comprising a first laser beam (22) and a second laser beam (24) arranged at least partially adjacent to the first laser beam (22), and the machining beam comprising a process gas beam, the device comprising: a workpiece support for supporting the workpiece (W) during a machining process; at least one laser beam source for providing laser radiation of the first laser beam and the second laser beam (22, 24); a process gas supply device for providing process gas; A machining head having a focusing optical device (30), wherein the machining head is configured to direct the machining beam toward a workpiece surface; A multi-clad optical fiber (10) having a core region (12) and at least one annular region (14) surrounding the core region (12), wherein the multi-clad optical fiber (10) is configured to transmit the first laser beam (22) in the core region (12) and the second laser beam (24) in the annular region (14) from the laser beam source to the processing head; and A control device is designed to control an apparatus for carrying out a method according to one of claims 1 to 10.

12. The device according to claim 11, further comprising: A beam splitting device is arranged between the laser beam source and the multi-clad optical fiber (10), and is configured to split a laser input beam provided by the laser beam source into the first laser beam (22) and the second laser beam (24), wherein the first laser beam (22) can be coupled into the core region (12) of the multi-clad optical fiber (10) and the second laser beam (24) can be coupled into the ring region (14) of the multi-clad optical fiber (10) by means of the beam splitting device.

13. A metal workpiece (W), comprising: a base body having an upper side and a lower side opposite to the upper side; wherein the base body has an edge extending laterally along an outer contour or an inner contour of the base body; wherein the base body has a rounding (44) at the transition between the upper side and the edge along at least a portion of the outer contour and / or the inner contour, the rounding extending over a height of at least 0.2 mm, preferably at least 0.5 mm; and Therein, the base body has a lower surface roughness along the rounding (44) than along the rest of the edge.

14. The workpiece according to claim 13, in, The workpiece edge can be produced by means of a method according to one of claims 1 to 10 .

Images