Method for laser cutting a component, and laser-cutting apparatus

Abstract

The invention relates to a method for laser cutting a component (16) in which a laser beam (12) is directed onto a component surface (14) of the component (16), the laser beam (12) being directed onto the component surface (14) at a specified inclination in or counter to a feed direction, as a result of which the component (16) is cut along a cutting contour in the feed direction (18) by means of the inclined laser beam (12).

Description

[0001] METHOD FOR LASER CUTTING A COMPONENT AS WELL AS

[0002] LASER CUTTING DEVICE

[0003] The invention relates to a method for laser cutting a component and a laser cutting device.

[0004] When cutting sheets with large sheet thicknesses, significant burr adhesion can occur in the areas of the respective cut edges of the cut sheets.

[0005] The object of the present invention is to provide a solution by which burr adhesion to cut edges can be avoided particularly well.

[0006] The object of the invention is achieved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are specified in the dependent claims, the description, and the drawings. Features, advantages, and possible embodiments set forth 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 of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0007] The invention relates to a method for laser cutting a component, in which a laser beam is directed onto a component surface. In particular, the laser beam is provided by means of a laser cutting device and directed onto the component surface. This laser cutting device can, for example, be a 2D laser flatbed machine which provides a support for the component. The component can be placed on this support while it is cut by means of the laser beam. The alignment of the laser beam onto the component surface results in the laser beam striking the component surface. Consequently, laser power from the laser beam is introduced into the component, creating a kerf in the component and thereby cutting the component.By aligning the laser beam with the component surface, the component is cut along a cutting contour in the feed direction. The cutting contour defines the line along which the component is to be cut. The laser cutting device aligns the laser beam with the cutting contour, thereby cutting the component along this contour. The feed direction characterizes the direction in which the laser beam moves across the component surface during cutting. The laser beam is thus moved across the component surface at a predetermined feed rate in the feed direction. In this process, the laser beam is directed at the component surface at a predetermined angle, either in the direction of feed or against the feed direction.This means that a defined inclination of the laser beam is specified for cutting the component, at which the laser beam is directed either in or against the feed direction onto the component surface during cutting. By tilting the laser beam, the formation of burrs on the cut edges of the component can be particularly well reduced when the laser beam is tilted in the feed direction. Nanojoints can be created particularly easily by switching the laser beam inclination between a trailing inclination (i.e., tilting the laser beam against the feed direction) and a penetrating inclination. Depending on whether the laser beam inclination is changed from trailing to penetrating or vice versa, nanojoints can be created on the top or bottom of the component.The process involves cutting the component with the inclined laser beam at least in one longitudinal section of the cutting contour, whereby the laser beam has a constant inclination in or against the feed direction in that longitudinal section.

[0008] In a possible further development of the invention, the laser beam is inclined towards the component surface in the feed direction, whereby a beam position of the laser beam on the underside of the component leads a beam position of the laser beam on the top side of the component. Thus, a piercing cut is achieved using the laser beam. Due to the orientation of the laser beam in the feed direction, the formation of burrs on the resulting cut edges of the component can be significantly reduced. Consequently, particularly thick components can be cut with exceptionally high cut quality using this method, especially components with a thickness of up to 20 millimeters when using a fusion cutting process, particularly a solid-state laser fusion cutting process, with a nominal power of twelve kilowatts.In a further possible embodiment of the invention, the laser beam is directed at the component surface from a perpendicular orientation at an angle of 4 degrees to 20 degrees, particularly at an angle of 15 degrees, either in or against the feed direction. In particular, the laser beam is directed at the component surface at an angle of 4 degrees to 20 degrees, particularly at an angle of 15 degrees, with a piercing angle in the feed direction. This allows the resulting melt to exit predominantly from the resulting kerf in the lead-up to the cut and less so at the sides of the cutting edge. Consequently, very little melt adheres to the underside of the cut edge, resulting in very little burr formation.

[0009] In a further possible embodiment of the invention, the laser beam is aligned perpendicular to the feed direction onto the component surface at changes in the cutting contour's direction. A reorientation can thus be programmed for these changes in direction, resulting in a change in the laser beam's inclination shortly before and shortly after the direction change. At a change in direction, which can be defined by a point or a small radius, the component can be cut using the laser beam, which is neither inclined in nor against the feed direction. This allows the component to be cut with particular precision using the laser beam, especially in the area of ​​each change in the cutting contour's direction.

[0010] In a further possible embodiment of the invention, the laser beam is additionally directed at the component surface at an angle around the feed direction for angled cutting. This allows the component to be cut at an angle particularly easily within the process. This angled cutting is possible with particularly large sheet thicknesses and minimal burr formation when the laser beam is inclined in the feed direction, thus enabling a shear cut of the component. This allows for particularly easy angled cutting within the process. As a result, a workpiece with a chamfer can be easily cut from the component, requiring very little, and in particular no, post-processing due to the minimal burr formation.

[0011] In this context, it is specifically intended that the laser beam will be used for the

[0012] Bevel cutting at an angle of more than 20 degrees, particularly 30 degrees, is performed with the feed direction inclined towards the component surface. This method makes it particularly easy to create a chamfer on the workpiece when cutting it out of the component. The process allows such bevel cutting to be carried out at very high feed rates with minimal burr formation, even with very thick sheets.

[0013] In a further possible embodiment of the invention, the component is cut using the laser beam in a fusion cut, in particular a solid-state laser fusion cut. In other words, the laser beam is directed onto the component surface by means of a laser, in particular a solid-state laser, as the laser beam source of the laser cutting device. Solid-state lasers are optically excited lasers whose amplifying and thus active medium consists of a crystalline or glassy, ​​and therefore amorphous, solid. Laser-active ions are contained in this so-called host material or host crystal in a specific concentration and thus doping. Solid-state lasers are typically pumped with visible light or infrared radiation.As an alternative to using a solid-state laser, other laser beam sources, such as a CO2 laser or a diode laser, or combinations of similar or different laser beam sources, can also be used to implement the present invention. Laser melt cutting separates all fusible materials, such as metals. In laser melt cutting, high-alloy steels and non-ferrous metals are heated to their melting temperature. The molten material is expelled from the kerf created during cutting using the kinetic energy of an inert gas such as nitrogen or argon. The component can thus be cut without the formation of an oxide layer in the respective kerfs created during cutting.

[0014] In a further possible embodiment of the invention, a cutting gas nozzle supplying a cutting gas is aligned with the same orientation as the laser beam on the component surface. This allows the cutting gas to assist the ejection of the melt from the kerf in a direction determined by the inclination of the laser beam. The cutting gas and the laser beam are thus aligned parallel to each other on the component surface. Preferably, the laser beam is aligned coaxially with the cutting gas through the opening of the cutting gas nozzle onto the component surface. In an alternative embodiment of the invention, the cutting gas nozzle supplying the cutting gas is aligned perpendicular to the component surface. This means that the orientation of the cutting gas nozzle can be selected independently of the orientation of the laser beam.By directing a cutting gas jet supplied by the cutting gas nozzle perpendicularly onto the component surface, reliable expulsion of the molten material generated during cutting from the underside of the component can be ensured. In the configuration described here, the laser beam and the cutting gas can preferably be directed onto the component surface by the same cutting gas nozzle. However, in this case, the nozzle opening on the component side can be made particularly large, so that the laser beam can be directed at an angle through the nozzle opening onto the component surface, independent of the cutting gas jet being directed perpendicular to the component surface. In this case, the (maximum) diameter of the nozzle opening of the cutting gas nozzle can, for example, be at least 7 mm. A suitable cutting gas nozzle is described, for example, in EP 3 315243 A1.Even more preferable for vertically aligning the cutting gas jet while simultaneously tilting the laser beam is a so-called mounted nozzle, in which a gap between the nozzle body and the workpiece surface is laterally limited by an axially movable nozzle sleeve. Such a nozzle is described, for example, in WO 2016 / 177595 A1. By using a mounted nozzle in combination with an inclined laser beam, a particularly high cutting quality can be achieved while simultaneously reducing gas consumption compared to the use of conventional cutting gas nozzles.

[0015] The invention further relates to a laser cutting device with a laser cutting head configured to direct a laser beam inclined in or against a feed direction onto a component surface for cutting a component, whereby the component is cut along a cutting contour in the feed direction by means of the laser beam. In particular, the laser cutting device is configured to carry out a method as already described in connection with the method according to the invention. The laser cutting device specifically comprises a solid-state laser as a laser beam source, which is configured to provide the laser beam.

[0016] Further features of the invention may become apparent from the following description of the figures and from the drawings. 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 themselves, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0017] The drawing shows in:

[0018] Fig. 1 shows a schematic sectional view of a laser cutting device and a component cut by means of the laser cutting device; and

[0019] Fig. 2 shows a schematic perspective view of a workpiece cut from the component using the laser cutting device.

[0020] Identical or functionally equivalent elements are marked with the same reference symbols in the figures.

[0021] Figure 1 shows a laser cutting head 10 of a laser cutting device. This laser cutting head 10 is configured to direct a laser beam 12 onto a component surface 14 of a component 16. The component 16 is cut by means of the laser beam 12 directed onto the component surface 14 of the component 16. The component 16 is cut using the laser cutting head 10 in this case by means of a fusion cut.

[0022] For cutting the component 16 along a predetermined cutting contour, the laser beam 12 is moved in a feed direction 18 relative to the component 16. The laser beam 12 is directed at the component surface 14 at an angle either in the feed direction 18 or opposite to the feed direction 18. In this case, the component 16 is cut by means of the laser beam 12. This means that the laser beam 12 is directed at the component surface 14 of the component 16 at an angle in the feed direction 18, as can be seen particularly well in Fig. 1. Specifically, the laser beam 12 is directed at the component surface 14 at an angle 22 of 4 degrees to 20 degrees, particularly at an angle 22 of 15 degrees, starting from a perpendicular orientation 20. As shown in Fig.Because the laser beam 12 can be detected particularly well, its beam position on the underside 24 of component 16 precedes it on the top side 26 of component 16 due to the penetrating orientation of the laser beam 12. The top side 26 of component 16 is the side on which the laser beam 12 first strikes in its longitudinal direction. In this case, the top side 26 is therefore the side of component 16 facing the laser cutting head 10. The underside 24 is located opposite the top side 26 and is thus on a side of component 16 facing away from the laser cutting head 10.In order to be able to cut the component 16 with particularly high precision in the area of ​​changes in direction of the cutting contour, it is provided that in the area of ​​this change in direction the laser beam 12 is directed perpendicular to the feed direction 18 onto the component surface 14 of the component 16.

[0023] As can be further seen in Fig. 1, the laser cutting head 10 comprises a cutting gas nozzle 28, which is configured to direct a cutting gas jet 30, comprising a cutting gas, onto the component surface 14 of the component 16. Here, it is provided that the cutting gas jet 30 is directed perpendicularly onto the component surface 14 of the component 16, regardless of the inclination of the laser beam 12, in or against the feed direction 18. Alternatively, the cutting gas nozzle 28 can be used to direct the cutting gas jet 30 parallel to the laser beam 12 onto the component surface 14 of the component 16.

[0024] It is possible to cut the component 16 at an angle using the laser beam 12. This allows a workpiece 32 to be cut out of the component 16, as shown in Fig. 2. The angled cutting allows the workpiece 32 to be provided with at least one chamfer. The angled cutting process creates respective angled cut surfaces 34 on the workpiece 32. For the angled cutting, the laser beam 12 is directed at the component surface 14 at an angle of more than 20 degrees around the feed direction 18. This allows the workpiece 32 with at least one chamfer to be cut out of the component 16 with very little material waste and in very few work steps.

[0025] The described method is based on the understanding that significant burr formation prevents the use of fusion cutting, for example with nitrogen or a mixed gas of nitrogen and oxygen as the cutting gas, for larger sheet thicknesses. The maximum sheet thickness at which the resulting burr formation is still acceptable depends on the rated power, focusing conditions, and cutting nozzle. For a rated power of twelve kilowatts and when using simple single-hole nozzles, the maximum sheet thickness in structural steel and chromium-nickel steel is eight millimeters with a perpendicular orientation of the laser beam 12 with respect to the feed direction 18. This problem of burr formation is to be solved by tilting the laser beam 12 in the feed direction 18.Due to the laser beam 12 being oriented in the feed direction 18 with a piercing direction, in which the beam position of the laser beam 12 on the underside 24 of the component leads the beam position of the laser beam 12 on the top side 26 of the component, the formation of burrs can be reduced particularly strongly, so that acceptable cutting qualities can be achieved up to a thickness of 20 millimeters.

[0026] To improve the cut edge quality, specifically burr height, during fusion cutting, particularly solid-state laser fusion cutting, on a 2D laser flatbed machine as well as on hybrid machines, the laser beam 12 is inclined at the laser cutting head 10 by means of an inclined cutting kinematic. In this case, the laser cutting head 10 is inclined. The inclination of the laser cutting head 10 is performed at an angle of 4 degrees to 20 degrees in the feed direction 18. This allows the molten material to escape predominantly from the resulting kerf in the lead-up to the cut and less so from the sides of the cutting front. Consequently, significantly less molten material adheres to the underside of the cut edge, resulting in less burr formation.

[0027] The cutting gas nozzle 28 can have the same orientation as the laser beam 12. Alternatively, the cutting gas nozzle 28 can be oriented perpendicular to the top surface 26 of the component, with only the laser beam 12 being angled. A single-hole nozzle is typically used as the cutting gas nozzle 28. Other nozzle geometries are also possible, allowing adjustment of the roughness depth, appearance, and burr height of the cut edge. For example, a 15-millimeter-thick structural steel component 16 can be cut on a twelve-kilowatt flatbed laser cutting machine with a kinematic angled cutting head. The laser cutting head 10 is oriented perpendicular to the component surface 14 for the initial cut. The cutting orientation of the laser beam 12 is adjusted during the approach to the cutting contour, specifically in parallel with the approach process to the cutting contour.The piercing orientation of the laser beam 12 is maintained while cutting all linear sections of the cutting contour. A reorientation can be programmed at changes in the direction of the cutting contour, which is to be executed in the area immediately before and immediately after the change in direction. At the change in direction, which can be a point or a small radius, the process uses a perpendicular orientation and adapted, in particular pulsed, cutting parameters. This method allows for the use of particularly high nominal powers. For example, with a nominal power of twelve kilowatts and a piercingly oriented laser beam 12, structural steel up to a thickness of 20 millimeters can be cut with comparable quality to a nominal power of 24 kilowatts with a perpendicularly oriented laser beam 12.

[0028] Furthermore, the process enables sheet thickness expansion during bevel cutting with particularly good cutting quality. When bevel cutting with nitrogen, a burr can form on the lower edge of the sheet at the limit of the sheet thickness. This problem can be addressed by bevel cutting. Here, in addition to being inclined around the feed direction 18, the laser beam 12 is tilted in the feed direction 18 by 4 to 20 degrees, particularly by 4 to 15 degrees. This makes it possible to reduce cutting front lag and expel the molten metal particularly well. The process enables sheet thickness expansion or angle enlargement to be achieved during bevel cutting with good cutting quality. In total, the laser beam 12 assumes two tilt positions during bevel cutting: one tilt position to generate the chamfer on the component 16 and one tilt position cutting directly in the feed direction 18.The cutting feed rate can be at the level of a standard feed rate for cutting a chamfer or up to 20 percent higher. Standard nozzles can be used for the cutting process. The nozzle spacing can range from three to five millimeters, and the cutting gas pressure can be from 15 to 24 bar. For example, the process can be used to prepare a 30-degree weld edge in 12-millimeter structural steel at 12 kilowatts of power. The cut begins with the laser cutting head 10 piercing the component 16. The laser cutting head 10 is then reoriented along a short approach path. This means that the laser cutting head 10 is tilted by 30 degrees to generate the chamfer and is set at a 15-degree angle in the feed direction 18. Once the cutting contour is reached, the chamfer is cut at these angles. The nozzle spacing for this process is, in particular, four millimeters, and the gas pressure is 24 bar.The focus diameter used for cutting is 210 micrometers. REFERENCE MARK LIST.

[0029] 10 Laser cutting head

[0030] 12 Laser beam 14 Component surface

[0031] 16 components

[0032] 18 Feed direction

[0033] 20 vertical alignment

[0034] 22 Angles 24 Component underside

[0035] 26 Component top

[0036] 28 Cutting gas nozzle

[0037] 30 cutting gas jet

[0038] 32 Workpiece 34 Cutting surface

Claims

PATENT CLAIMS 1. Method for laser cutting a component (16) in which a laser beam (12) is directed onto a component surface (14) of the component (16), wherein the laser beam (12) is directed onto the component surface (14) at a predetermined inclination in or against a feed direction, whereby the component (16) is cut along a cutting contour in the feed direction (18) by means of the inclined laser beam (12).

2. Method according to claim 1, characterized in that the laser beam (12) is inclined in the feed direction (18) towards the component surface (14), whereby a beam position of the laser beam (12) on a lower surface (24) of the component (16) precedes a beam position of the laser beam (12) on a upper surface (26) of the component (16).

3. Method according to claim 1 or 2, characterized in that the laser beam (12) is directed towards the component surface (14) at an angle (22) of 4 to 20 degrees, in particular at an angle (22) of 15 degrees, starting from a perpendicular orientation to the component surface (14) at or against the feed direction (18).

4. Method according to one of the preceding claims, characterized in that at changes in direction of the cutting contour the laser beam (12) is aligned perpendicular to the feed direction (18) onto the component surface (14).

5. Method according to one of the preceding claims, characterized in that the laser beam (12) is additionally directed towards the component surface (14) at an angle about the feed direction (18) for oblique cutting.

6. Method according to claim 5, characterized in that The laser beam (12) is directed towards the component surface (14) at an angle of more than 20 degrees around the feed direction (18) for bevel cutting.

7. Method according to one of the preceding claims, characterized in that the component (16) is cut by means of the laser beam (12) within the framework of a melt cut.

8. Method according to one of the preceding claims, characterized in that a cutting gas nozzle (28) providing a cutting gas is aligned with the same orientation as the laser beam (12) on the component surface (14).

9. Method according to one of claims 1 to 7, characterized in that a cutting gas nozzle (28) providing a cutting gas is aligned perpendicularly to the component surface (14).

10. Laser cutting device, with a laser cutting head (10) which is configured to direct a laser beam (12) inclined in or against a feed direction (18) onto a component surface (14) of the component (16) for cutting a component (16), whereby the component (16) is cut in the feed direction (18) along a cutting contour by means of the laser beam (12).

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