DE102024111675A1 - METHOD FOR LASER CUTTING A COMPONENT AND LASER CUTTING DEVICE - Google Patents

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), wherein the laser beam (12) is directed at 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).

Description

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

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

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

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.

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 onto the component surface, the component is cut in the feed direction along a cutting contour. The cutting contour defines a line along which the component is to be cut. By means of the laser cutting device, the laser beam is aligned onto the cutting contour, thereby cutting the component along the cutting 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 or against the feed direction. This means that a defined angle is specified for the laser beam during cutting, at which the laser beam must be directed at the component surface, either in or against the feed direction. By tilting the laser beam, the formation of burrs on the cut edges of the component can be significantly reduced, especially when the laser beam is tilted in the feed direction. Nanojoints can be created particularly easily by alternating the laser beam's angle between a trailing angle (tilting the laser beam against the feed direction) and a penetrating angle. Depending on whether the laser beam's inclination changes from trailing to piercing or vice versa, nanojoints can be created on either the top or bottom of the component. The process involves cutting the component with the inclined laser beam along at least one longitudinal section of the cutting contour, where the laser beam maintains a constant inclination in or against the feed direction within that section.

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 another possible embodiment of the invention, it is provided that the laser beam, starting from a perpendicular orientation to the component surface, is inclined at an angle of 4 degrees to 20 degrees, in particular at an angle of 15 degrees, in or against the feed direction to the component surface. In particular, the laser beam is designed to be directed at the component surface at an angle of 4 to 20 degrees, especially at an angle of 15 degrees, with a piercing angle in the feed direction. 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 edge. Consequently, very little molten material adheres to the underside of the cut edge, resulting in minimal burr formation.

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 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.

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.

In this context, it is particularly important that the laser beam for bevel cutting is inclined at more than 20 degrees, especially at an angle of 30 degrees, around the feed direction and directed towards the component surface. This makes it particularly easy to create a chamfer on the workpiece when cutting it out of the component. The process enables such bevel cutting to be carried out at particularly high feed rates with minimal burr formation, even with very thick sheets.

In another possible embodiment of the invention, the component is cut using a laser beam in a fusion cutting process, particularly a solid-state laser fusion cutting process. In other words, the laser beam is directed onto the component surface by means of a laser, especially 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. This so-called host material or host crystal contains laser-active ions in a specific concentration and thus doping. Solid-state lasers are typically pumped with visible light or infrared radiation. However, as an alternative to using a solid-state laser, other laser beam sources, for example 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 fusion 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 then expelled from the kerf created during cutting using the kinetic energy of an inert gas such as nitrogen or argon. This allows the component to be cut without the formation of an oxide layer in the kerf.

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 alignment of the cutting gas nozzle is independent of the laser's alignment. The laser beam can be selected. By perpendicularly aligning a cutting gas jet supplied by the cutting gas nozzle 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 also preferably be aligned onto the component surface through the same cutting gas nozzle. However, in this case, the component-side nozzle opening 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 oriented perpendicular to the component surface. In this case, a (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, for example, available in the... EP 3 315 243 A1 described. Even more preferably, for the vertical alignment of the cutting gas jet while simultaneously tilting the laser beam, a so-called mounted nozzle can be used as a cutting gas nozzle, in which a gap between the nozzle body and the component surface is laterally limited by an axially movable nozzle sleeve. Such a nozzle is used, for example, in the WO 2016/177595 A1 described. By using an attached 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.

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.

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.

• 1 eine schematische Schnittansicht einer Laserschneidvorrichtung sowie eines mittels der Laserschneidvorrichtung geschnittenen Bauteils; und
• 2 eine schematische Perspektivansicht eines aus dem Bauteil mittels der Laserschneidvorrichtung ausgeschnittenen Werkstücks.

The drawing shows in:

• 1 a schematic sectional view of a laser cutting device and of a component cut by means of the laser cutting device; and
• 2 A schematic perspective view of a workpiece cut from the component using the laser cutting device.

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

In 1 A laser cutting head 10 of a laser cutting device is shown. 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.

For cutting component 16 along a predefined cutting contour, the laser beam 12 is moved in a feed direction 18 relative to the component 16. The laser beam 12 is directed towards the component surface 14 at an angle 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 using a piercing cut.

This means that the laser beam 12 is inclined in the feed direction 18 and aligned towards the component surface 14 of the component 16, as shown in 1 can be recognized particularly well. Here, it is provided that the laser beam 12, starting from a vertical orientation 20, is inclined at an angle 22 of 4 degrees to 20 degrees, in particular at an angle 22 of 15 degrees, in the feed direction 18 and directed towards the component surface 14. As in 1 As can be seen particularly well, due to the piercing orientation of the laser beam 12, a beam position of the laser beam 12 on a component underside 24 of component 16 precedes a beam position of the laser beam 12 on a component upperside 26 of component 16. Here, the component upperside 26 of component 16 is the side on which the laser beam 12 first strikes in a longitudinal direction. In this case, the component upperside 26 is therefore the side of component 16 facing the laser cutting head 10. The component underside 24 is located opposite the component upperside 26 and is situated thus on a side of the 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.

As in 1 As can be further identified, the laser cutting head 10 comprises a cutting gas nozzle 28, which is configured to direct a cutting gas jet 30, comprising 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.

It is possible to cut component 16 at an angle using the laser beam 12. This allows a workpiece 32 to be cut out of component 16, as shown in 2 As shown. By means of bevel cutting, the workpiece 32 can be provided with at least one chamfer. The bevel cutting process creates respective beveled cut surfaces 34 on the workpiece 32. It is intended that the laser beam 12 for bevel cutting is inclined at more than 20 degrees around the feed direction 18 and directed onto the component surface 14. Thus, the workpiece 32 with at least one chamfer can be cut from the component 16 with very little waste and with very few work steps.

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.

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.

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 of the cut edge, and burr height. 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 piercing process. The piercing 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 during the cutting of 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. cut as with a nominal power of 24 kilowatts with a vertically oriented laser beam 12.

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 a sheet at the limit of 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 allows 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 create 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 an edge chamfer or up to 20 percent higher. Standard nozzles can be used for the cutting process. Nozzle spacing can range from three to five millimeters, and cutting gas pressures from 15 to 24 bar. For example, a 30-degree weld edge preparation can be achieved in 12-millimeter structural steel using this process at 12 kilowatts of power. The cut begins with 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 bevel and is set at a 15-degree angle in the feed direction 18. Once the cutting contour is reached, the bevel 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

10

laser cutting head

12

laser beam

14

Component surface

16

component

18

Feed direction

20

vertical alignment

22

angle

24

Component underside

26

Component top

28

Cutting gas nozzle

30

Cutting gas jet

32

workpiece

34

Cut surface

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 3 315 243 A1 [0013]
• WO 2016/177595 A1 [0013]

Claims (10)

Method for laser cutting of 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). Procedure 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 component underside (24) of the component (16) precedes a beam position of the laser beam (12) on a component topside (26) of the component (16). Procedure 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). 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). 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. Procedure according to Claim 5 , characterized in that the laser beam (12) is inclined at more than 20 degrees about the feed direction (18) towards the component surface (14) for bevel cutting. 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. 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). Procedure according to one of the Claims 1 until 7 , characterized in that a cutting gas nozzle (28) providing a cutting gas is aligned perpendicularly to the component surface (14). 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).