Method for producing a cut edge by means of a laser beam and laser cutting machine

Abstract

The invention relates to a method for producing a cut edge by means of a laser beam (14). The laser beam (14) has a first beam region (16) and a second beam region (18). The second beam region (18) surrounds the first beam region (16). The method has the steps of: producing the cut edge by guiding the laser beam (14) along a trajectory (46) over a workpiece (12) at a feed rate, wherein the feed rate changes along the trajectory (46); and changing a ratio, which is formed from a power of the first beam region (16) and a power of the second beam region (18), in dependence on the feed rate.

Description

[0001] Title: Method for producing a cut edge using a laser beam and laser cutting machine

[0002] Description

[0003] The invention relates to a method for producing a cut edge using a laser beam and a laser cutting machine.

[0004] Typically, the quality of a laser-cut edge depends on the laser beam's feed rate. The quality of the cut edge can be described, for example, by the degree of roughness and / or burr formation. High quality can be understood as a cut edge exhibiting low roughness and / or a small or even no burr.

[0005] For example, if a cut edge has a straight section and a curved section, the curved section is often produced at a lower feed rate than the straight section. Because the quality of the cut edge depends on the feed rate, variations in quality can occur, resulting in the straight and curved sections not having the same quality.

[0006] WO 2010 / 028514 A1 describes a laser cutting system and a method for cutting workpieces, wherein the rules implemented in the control device can be determined depending on at least one of the respective registered values ​​of the speed of the processing head.

[0007] US 2018 / 0188544 A1 discloses an adjustment of beam parameters based on the thickness of the material.

[0008] The invention aims to provide a method for producing a cut edge using a laser beam and a laser cutting machine, each of which enables the production of a high-quality cut edge.

[0009] The invention solves this problem by providing a method with the features of claim 1 and a laser cutting machine with the features of claim 11. Advantageous embodiments and further developments of the invention are described in the dependent claims. A method according to the invention is designed for producing a cut edge using a laser beam. The laser beam has, particularly in its cross-section, a first beam region and a second beam region. The second beam region surrounds the first beam region, in particular circumferentially.The method comprises: producing the cutting edge by guiding the laser beam along a trajectory over a workpiece at a feed rate, wherein the feed rate changes along the trajectory; and changing a ratio formed from a power of the first beam area and a power of the second beam area as a function of the feed rate, in particular while guiding the laser beam along the trajectory over the workpiece.

[0010] Advantageously, this ensures that the cut edge maintains a consistently high quality even when the feed rate changes. In particular, it ensures that the cut edge quality remains consistently high, regardless of whether the cut edge was produced at a high or low feed rate.

[0011] The ratio can be formed by dividing the power of the first beam area by the power of the second beam area or by dividing the power of the second beam area by the power of the first beam area.

[0012] The ratio can be changed by changing the power of the first beam area and / or the power of the second beam area. The ratio can be changed continuously, in particular steplessly.

[0013] The power of the first beam region can be understood as the power of the laser beam in the first beam region. The power of the second beam region can be understood as the power of the laser beam in the second beam region.

[0014] Changing the ratio depending on the feed rate can be an adjustment of the laser beam to the feed rate. The change in the ratio can be made depending on a specific value of the feed rate.

[0015] By changing the ratio, the melting area of ​​the workpiece, which is melted during the cutting process using the laser beam, can be adjusted in size and / or shape. In particular, the size and / or shape of the melting area can be matched to the feed rate. This adjustment allows for optimal coupling of the cutting gas and efficient molten metal removal, resulting in a cut edge with low roughness and / or a small or no burr.

[0016] The first beam area can be circular. The second beam area can be annular. The second beam area can surround the first beam area. The first and second beam areas can be defined by having independently adjustable power levels.

[0017] Guiding the laser beam along its trajectory across the workpiece means that the point of impact, where the laser beam strikes the workpiece, is moved along this trajectory across the workpiece. The feed rate can be defined as the speed at which the point of impact moves relative to the workpiece.

[0018] The workpiece may have the cut edge.

[0019] The trajectory must be continuous. The laser beam can be guided along the trajectory in one continuous motion.

[0020] The production of the cutting edge can include: melting the workpiece by means of the laser beam at an impact point where the laser beam hits the workpiece; directing a cutting gas to the impact point; and expelling molten material by means of the cutting gas.

[0021] The process can include: changing the ratio depending on the workpiece thickness. The workpiece thickness can be specified by a CAD model of the workpiece. This allows the power of the first beam area and / or the power of the second beam area to be adjusted to the workpiece thickness at the point of impact.

[0022] The workpiece can be made of aluminum. The workpiece can be an aluminum die-cast component.

[0023] Another aspect of the process is that changing the ratio alters the geometry of a cutting gap, thereby influencing the flow behavior of a cutting gas, which in turn affects the ejection of the melt. Preferably, the flow behavior can be influenced in such a way that the ejection of the melt results in little or no scoring.

[0024] Another aspect of the process can be that by changing the ratio, the cutting gas can be coupled in such an optimal way that cutting gas consumption is reduced.

[0025] Another aspect of the process may be that by changing the ratio, it may be unnecessary to adjust the cutting gas pressure to the feed rate.

[0026] Another aspect of the process may be that the manufacturing time of the cut edge is reduced, since changing the ratio depending on the feed rate can be done faster than adjusting the cutting gas pressure to the feed rate.

[0027] In a further development of the method, the cutting edge is kept constant by changing the ratio. Advantageously, this allows the cutting edge to be independent of the feed rate.

[0028] In a further development of the process, the ratio is changed depending on a value and / or a change in the feed rate.

[0029] A deviation below or above a predetermined value by the feed rate can initiate a change in the ratio.

[0030] A change in feed rate can initiate a change in the ratio.

[0031] In a further development of the method, the laser beam power is kept constant while the ratio is changed. Alternatively, the laser beam power is varied depending on the feed rate while the ratio is changed.

[0032] In a further development of the process, increasing the feed rate changes the ratio by increasing the power of the first jet area and / or reducing the power of the second jet area. Conversely, reducing the feed rate changes the ratio by reducing the power of the first jet area and / or increasing the power of the second jet area. Advantageously, this can result in a particularly high-quality cut edge.

[0033] In a further development of the method, the trajectory has a first section and a second section. The laser beam is guided along the first section of the trajectory at a first feed rate and along the second section at a second feed rate. The first and second feed rates differ, particularly in their magnitudes. Advantageously, this allows for the production of cut edges with complex profiles and consistent quality. Due to the different feed rates, the ratio value in the first section of the trajectory and the ratio value in the second section can differ.

[0034] In a further development of the method, the first section has a straight path. The second section has a curved path. For example, the second section can be shaped as a curve. In particular, the second section can be shaped like a circular segment.

[0035] In a further development of the method, the process comprises: forming the first and second beam regions using a beam shaping device. Advantageously, the first and second beam regions can be formed particularly easily with the beam shaping device. After passing through the beam shaping device, a portion of the laser beam can define the first beam region and another portion the second beam region. After passing through the beam shaping device, this portion and the additional portion can propagate along a common beam axis. The beam shaping device can be configured to coaxially superimpose this portion and the additional portion for the purpose of forming the laser beam.

[0036] In a further development of the method, the beam shaping device features an optical waveguide with a core and a cladding. The first beam region is formed by coupling a portion of the laser beam into the core, and the second beam region is formed by coupling a portion of the laser beam into the cladding. Advantageously, the waveguide allows for a particularly compact and stable design. The waveguide can be designed as an optical fiber.

[0037] The core and the cladding can each be configured to guide the laser beam via waveguides. The core can be surrounded by the cladding. The core can have a higher refractive index than the cladding. The core can have a diameter in the range of 60 pm (micrometers) to 90 pm, particularly 70 pm to 80 pm. The core can have a diameter of 75 pm. The cladding can have a diameter in the range of 200 pm to 400 pm, particularly 250 pm to 350 pm. The cladding can have a diameter of 300 pm.

[0038] In a further development of the method, the ratio is changed by altering the portion of the laser beam coupled into the core. Additionally or alternatively, the ratio is changed by altering the portion of the laser beam coupled into the cladding. Advantageously, the portions of the laser beam coupled into the core and / or the cladding can be changed particularly easily. The portions of the laser beam coupled into the core and the cladding can be changed independently of each other.

[0039] Changing the portion of the laser beam coupled into the core can be understood as changing the power of that portion. Changing the portion of the laser beam coupled into the cladding can be understood as changing the power of that portion.

[0040] Changing the portion of the laser beam coupled into the core and / or the portion coupled into the cladding can be achieved by means of a movable optical wedge plate. Advantageously, the wedge plate can allow stepless adjustment. Details regarding the movable optical wedge plate can be found in WO 2011 / 124671 A1. In particular, the description of the wedge plate in WO 2011 / 124671 A1 is hereby incorporated by reference into this description.

[0041] Alternatively, a beam from one laser resonator can be coupled into the core and a beam from another laser resonator into the cladding. The beam from the first laser resonator can be coupled into the core via a waveguide spliced ​​to it. The beam from the second laser resonator can be coupled into the cladding via a waveguide spliced ​​to it. Changing the ratio of the power of the first beam region to the power of the second beam region can be achieved by controlling the power of the beam from the first laser resonator and / or by controlling the power of the beam from the second laser resonator.

[0042] A laser cutting machine according to the invention is designed for producing a cut edge using a laser beam. The laser cutting machine comprises a laser beam source, a beam guidance device, and a control unit. The laser beam source is designed to generate a laser beam that has a first beam region and a second beam region surrounding the first beam region, in particular circumferentially. The beam guidance device is suitable for guiding the laser beam along a trajectory over a workpiece at a feed rate. The control unit is suitable for controlling the laser beam source to change a ratio formed by the power of the first beam region and the power of the second beam region, depending on the feed rate.

[0043] The laser cutting machine can be configured to perform the previously described process. In particular, the previously described process can be configured to operate the laser cutting machine. The above description of the process can apply to identical or functionally equivalent features of the laser cutting machine and / or vice versa.

[0044] The beam guidance device can be designed as a scanner optic, a flying optic, or a processing head.

[0045] The control unit may include an electrical computing unit, in particular a computer and / or a microcontroller.

[0046] The control unit can be configured to control the beam guidance device for guiding the laser beam along the trajectory across the workpiece at the feed rate. In other words, the control unit can guide the laser beam across the workpiece at the feed rate and change the ratio.

[0047] Further advantages and advantageous embodiments of the invention can be seen from the figures, their description, and the claims. All features disclosed in the figures, their description, and the claims can be essential to the invention, both individually and in any combination. The figures show:

[0048] Fig. 1 shows a schematic representation of a laser cutting machine,

[0049] Fig. 2 is a schematic representation of a cross-section of a laser beam of the laser cutting machine of Fig. 1, and

[0050] Fig. 3 shows a schematic representation of a workpiece before a cutting edge is made into the workpiece using the laser cutting machine of Fig. 1.

[0051] Fig. 1 shows a laser cutting machine 10. The laser cutting machine 10 is suitable for producing a cut edge in a workpiece 12 using a laser beam 14.

[0052] In the illustrated embodiment, the workpiece 12 is made of aluminum. The workpiece 12 is a sheet. The width and / or length of the first workpiece 12 is more than five times, in particular ten times, its thickness. In an alternative embodiment not shown, the workpiece is an aluminum die-cast component.

[0053] Fig. 2 schematically shows a cross-section of the laser beam 14 of the laser cutting machine 10. The laser beam 14 has a first beam region 16 and a second beam region 18. The first beam region 16 is completely surrounded by the second beam region 18. The first beam region 16 is circular. The second beam region 18 is annular. The second beam region 18 borders the first beam region 16. The power of the first beam region 16 and the power of the second beam region 18 can be adjusted independently of each other.

[0054] Fig. 1 shows that the laser cutting machine 10 has a laser beam source 22. The laser beam source 22 is designed to generate the laser beam 14.

[0055] The laser beam source 22 has a laser resonator 26 and a beam shaping device 28. After the laser beam 14 is generated by the laser resonator 26, the laser beam 14 passes through the beam shaping device 28. The beam shaping device 28 shapes the laser beam 14 such that the laser beam 14 has the first beam region 16 and the second beam region 18 in the arrangement shown in Fig. 2. The beam shaping device 28 has an optical waveguide 30 and a coupling device 32 for coupling the laser beam 14 into the optical waveguide 30. The optical waveguide 30 is designed as an optical fiber with a core and a cladding. The coupling device 32 is configured to couple a portion of the laser beam 14 into the core and another portion of the laser beam 14 into the cladding. After passing through the optical waveguide 30, the laser beam 14 has the cross-section shown in Fig. 2.The portion of the laser beam 14 that has passed through the core forms the first beam region 16 and the portion of the laser beam 14 that has passed through the shell forms the second beam region 18.

[0056] The coupling device 32 is designed to continuously change the proportion of the laser beam 14 coupled into the core and the proportion of the laser beam 14 coupled into the cladding. This changes the ratio formed by the power of the first beam region 16 and the power of the second beam region 18.

[0057] The coupling device 32 can include an optical wedge plate for changing the ratio. In particular, the optical wedge plate can partially project into the beam path of the laser beam 14 generated by the laser resonator and thereby deflect a portion of the laser beam 14 such that it is coupled into the cladding. By changing the position of the optical wedge plate, the magnitude of the portion of the laser beam coupled into the cladding can be altered.

[0058] In an alternative embodiment not shown, the laser beam source has a first laser resonator and a second laser resonator. The first laser resonator can generate a beam that is coupled into the core, and the second laser resonator can generate a beam that is coupled into the cladding. The beam from the first laser resonator can be coupled into the core by means of a waveguide spliced ​​onto the core. The beam from the second laser resonator can be coupled into the cladding by means of a waveguide spliced ​​onto the cladding. After passing through the core and the cladding, the beam from the first laser resonator and the beam from the second laser resonator can combine to form the laser beam.Changing the ratio formed by the power of the first beam region and the power of the second beam region can be achieved by changing the output power of the first laser resonator and / or the output power of the second laser resonator. The laser cutting machine 10 has a beam guidance device 34 for guiding the laser beam 14 from the laser beam source 22 to the workpiece 12. The beam guidance device 34 has a processing head 36. The processing head 36 is nozzle-shaped. To produce the cutting edge, the laser beam 14 and a cutting gas 38 are supplied to the processing head 36. The cutting gas 38 exits the processing head 36 together with the laser beam 14. The laser beam 14 strikes the workpiece 12 at an impact point 40 and locally melts the workpiece 12.The cutting gas 38 is directed by the machining head 36 towards the point of impact 40 in such a way that the cutting gas 38 expels the molten material from the locally melted workpiece 12. If the machining head 36 is simultaneously moved along a direction of movement 42, the cutting edge is formed in the workpiece 12.

[0059] The laser cutting machine 10 has a control unit 44. The control unit 44 is an electronic computing unit in the form of a computer. The control unit 44 is designed to control the beam guidance device 34 for guiding the laser beam 14 along a trajectory over the workpiece 12 at a feed rate, and the laser beam source 22 for changing the ratio depending on, in particular, a value of, the feed rate. This allows the control unit 44 to adjust the ratio to the feed rate.

[0060] Fig. 3 shows the workpiece 12 before the cutting edge is produced using the laser cutting machine 10. The control unit 44 is predefined by the thickness of the workpiece 12 and the trajectory 46 along which the laser beam 14 is guided over the workpiece 12. The trajectory 46 is rectangular with rounded corners. Therefore, the trajectory 46 has straight sections 48 and curved sections 50. The thickness of the workpiece 12 is constant along the trajectory 46.

[0061] The control unit 44 determines a feed rate at which the laser beam 14 is guided along the trajectory 46 across the workpiece 12 to produce the cut edge. The determined feed rate is higher for the straight sections 48 than for the curved sections 50. Therefore, the laser beam 14 is not guided along the trajectory 46 across the workpiece 12 at a constant feed rate. In other words, the feed rate changes along the trajectory 46. The cut edge is produced by guiding the laser beam 14 along the trajectory 46 across the workpiece 12 at the determined feed rate. While guiding the laser beam 14 along the trajectory 46, the control unit 44 changes the ratio of the beam shaping device 28 depending on the feed rate.Changing the ratio depending on the feed rate is an adjustment of the laser beam to the feed rate.

[0062] Changing the ratio ensures a constant quality of the cut edge. This results in the same quality of cut edge in the straight sections 48 and in the curved sections 50.

[0063] The ratio is changed based on a feed rate value. Since the determined feed rate is greater for the straight sections 48 than for the curved sections 50, the ratio is changed when transitioning from a straight section 48 to a curved section 50 by reducing the power of the first beam area 16 and increasing the power of the second beam area 18, and when transitioning from a curved section 50 to a straight section 48 by increasing the power of the first beam area 16 and reducing the power of the second beam area 18. The power of the laser beam 14 is kept constant during the ratio change.

[0064] By changing the ratio, the size of the melting area of ​​the workpiece 12, which is melted during the production of the cutting edge by means of the laser beam 14, is adjusted. In other words, the size of the melting area is matched to the feed rate. Matching the size of the melting area to the feed rate serves to modify the geometry of a cutting gap, thereby influencing the flow behavior of the cutting gas 38, which in turn affects the ejection of the molten metal. This allows the cutting gas 38 to be optimally coupled and the molten metal to be optimally ejected, so that the cutting edge has low roughness and no burr, regardless of the trajectory 46.

[0065] In an alternative embodiment not shown, the thickness of the workpiece can vary along the trajectory. The thickness can be specified to the control unit, in particular by a CAD model of the workpiece. The control unit can be configured to additionally change the ratio depending on the thickness of the workpiece.

Claims

Patent claims 1. Method for producing a cut edge using a laser beam (14), wherein the laser beam (14) has a first beam region (16) and a second beam region (18), wherein the second beam region (18) surrounds the first beam region (16), in particular circumferentially, wherein the method comprises: Producing the cutting edge by guiding the laser beam (14) along a trajectory (46) over a workpiece (12) at a feed rate, wherein the feed rate changes along the trajectory (46), and changing a ratio formed from a power of the first beam area (16) and a power of the second beam area (18) as a function of the feed rate.

2. Method according to claim 1, wherein the shape of the cutting edge is kept constant by changing the ratio.

3. Method according to one of the preceding claims, wherein the changing of the ratio is carried out depending on a value and / or a change in the feed rate.

4. Method according to one of the preceding claims, wherein the power of the laser beam (14) is kept constant during the changing of the ratio, or wherein the power of the laser beam (14) is changed during the changing of the ratio depending on the feed rate.

5. Method according to one of the preceding claims, wherein, when the feed rate is increased, the ratio is changed by increasing the power of the first beam area (16) and / or by reducing the power of the second beam area (18), wherein, when the feed rate is reduced, the ratio is changed by reducing the power of the first beam area (16) and / or by increasing the power of the second beam area (18).

6. Method according to one of the preceding claims, wherein the trajectory (46) has a first section (48) and a second section (50), wherein the laser beam (14) is guided along the first section (48) of the trajectory (46) at a first feed rate and along the second section (50) of the trajectory (46) at a second feed rate, wherein the first feed rate and the second feed rate differ from each other, in particular in their magnitudes.

7. Method according to claim 6, wherein the first section (48) has a straight course, and wherein the second section (50) has a curved course.

8. Method according to one of the preceding claims, wherein the method comprises: forming the first beam area (16) and the second beam area (18) by means of a beam shaping device (28).

9. Method according to claim 8, wherein the beam shaping device (28) has an optical waveguide (30) with a core and a cladding, wherein the formation of the first beam region (16) is carried out by coupling a portion of the laser beam (14) into the core and the formation of the second beam region (18) is carried out by coupling a portion of the laser beam (14) into the cladding.

10. Method according to claim 9, wherein the changing of the ratio is effected by changing the portion of the laser beam (14) coupled into the core, and / or wherein the changing of the ratio is effected by changing the portion of the laser beam (14) coupled into the cladding.

11. Laser cutting machine (10) for producing a cutting edge by means of a laser beam (14), comprising: a laser beam source (22) for generating the laser beam (14), which has a first beam area (16) and a second beam area (18) surrounding the first beam area (16), in particular circumferentially, 2018P00204WG 15 25.08.2025 a beam guidance device (34) for guiding the laser beam (14) along a trajectory (46) over a workpiece (12) at a feed rate, a control unit (44) for controlling the laser beam source (22) for changing a Ratio formed from the power of the first beam area (16) and the power of the second beam area (18), depending on the feed rate.

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