Laval nozzle, method, laser working device

Abstract

The invention relates to a Laval nozzle (28) for a laser working device (10) for working a workpiece (12) by means of a laser beam (18, 20), the Laval nozzle (28) comprising: a nozzle inlet (68) having an inlet diameter (70), and a nozzle outlet (72) having an outlet diameter (74), a nozzle channel (76) which fluidically connects the nozzle inlet (68) and the nozzle outlet (72), extends along a flow direction (66) and has a compression portion (78) and an expansion portion (80), wherein the compression portion (78) tapers along the flow direction (66) and the expansion portion (80) tapers counter to the flow direction (66) toward a constriction (82) having a constriction diameter (84), wherein the compression portion (78) has a compression length (86) and the expansion portion (80) has an expansion length (88), wherein the ratio of the compression length (86) to the expansion length (88) is less than 0.6, and to a laser cutting method and a laser working installation (10).

Description

[0001] Title: Laval nozzle, process, laser processing device

[0002] Description

[0003] The invention relates to a Laval nozzle for a laser processing device for processing a workpiece by means of a laser beam, a method for laser cutting and a laser processing device.

[0004] From WO 2021 / 228 829 A1, a method for laser cutting three-dimensionally shaped sheet metal using two laser beams and a gas jet is known, which combines high cutting speed and good cut quality. Due to the complexity of the geometry of the workpieces to be processed and the increased cutting speed, the planning and monitoring of the cutting tool's movement path is of significant importance in order to prevent collisions between the cutting tool and the workpiece.

[0005] To apply gas pressure in a laser cutting process, it is known, among other things, from DE 10 2019 135 375, to use a laser cutting nozzle with an inner and an outer nozzle part. A disadvantage is that a small working distance is required to apply sufficient back pressure.

[0006] The invention is based on the objective of ensuring a substantially constant dynamic pressure of the gas jet during laser processing, in particular during laser cutting of three-dimensional workpieces, even with a changing working distance, especially in a range up to 50 mm.

[0007] The problem underlying the invention is solved by a Laval nozzle with the features of claim 1. The invention relates to a Laval nozzle for a laser processing device for processing a workpiece using a laser beam. The Laval nozzle comprises: a nozzle inlet with an inlet diameter and a nozzle outlet with an outlet diameter, as well as a nozzle channel fluidically connecting the nozzle inlet and the nozzle outlet and extending along a flow direction, with a compression section and an expansion section. The compression section tapers along the flow direction, and the expansion section tapers against the flow direction towards a constriction. The constriction has a constriction diameter, which preferably represents the smallest diameter of the nozzle channel. The compression section has a compression length, and the expansion section has an expansion length.The ratio between the compression length and the expansion length is less than 0.6.

[0008] Surprisingly, numerous tests have shown that when using such a Laval nozzle in a laser processing process, a substantially constant back pressure of over 2 bar is maintained even at a working distance in the range between 1 mm and 50 mm.

[0009] Furthermore, the position of the inner contour of the Laval nozzle can be adjusted as desired along the flow direction, while the outer contour of the Laval nozzle can be designed as desired. Additionally, angled cutting with an angle of attack of up to 30° is conceivable.

[0010] For the purposes of the invention, a Laval nozzle is understood to be a laser cutting nozzle with a Laval contour as its inner contour. For the purposes of the invention, the working distance is understood to be the actual distance between the Laval nozzle and the entry surface of the workpiece.

[0011] The dynamic pressure, or effective dynamic pressure, can be determined, for example, on a test rig with an impact plate. The impact plate is oriented so that it is directly exposed to the gas jet and, in particular, the laser beams. The gas jet and / or the laser beams are directed onto the sample surface, thereby creating an effective dynamic pressure on the sample surface that generates a measurable force or deformation. Sensors attached to the impact plate detect this force or deformation. The sensor data obtained in this way are statistically analyzed to determine the dynamic pressure, especially the average pressure, as well as any possible fluctuations.

[0012] An advantageous aspect of the invention provides that the ratio between the compression length and the expansion length lies in a range between 0.2 and 0.6, particularly at 0.5. Surprisingly, it has been found that such a length ratio has a particularly positive effect on the constancy of the stagnation pressure of the gas jet.

[0013] An advantageous aspect of the invention is that the tapering of the compression section and / or the expansion section is continuous. This ensures optimal gas jet flow. Alternatively, the compression and / or expansion section could be conical or stepped.

[0014] An advantageous aspect of the invention provides that the compression length is in a range between 2 mm and 10 mm, in particular between 3 mm and 7 mm, preferably at 5 mm.

[0015] An advantageous aspect of the invention provides that the expansion length is in a range between 5 mm and 20 mm, in particular between 8 mm and 15 mm, preferably between 10 mm and 15 mm, preferably at 10 mm.

[0016] An advantageous aspect of the invention provides that the Laval nozzle has a nozzle length extending between the nozzle inlet and the nozzle outlet, wherein the nozzle length is in a range between 11.5 mm and 20 mm, in particular between 13 mm and 17 mm, preferably at 15 mm. If the Laval nozzle does not have a cylindrical section, the nozzle length corresponds to the sum of the compression length and the expansion length.

[0017] An advantageous aspect of the invention provides that the compression section extends from the nozzle inlet to the constriction. Another advantageous aspect of the invention provides that the expression section extends from the constriction to the nozzle outlet. Accordingly, the entire nozzle length is designed to be flow-relevant. Alternatively, a cylinder section with a constant diameter can be provided between the nozzle inlet and the compression section, which is at least substantially flow-irrelevant.

[0018] An advantageous aspect of the invention provides that the constriction diameter is in a range between 1 mm and 3 mm, in particular between 1.4 mm and 2.6 mm, preferably at 1.8 mm. Preferably, the constriction diameter is larger than 1.8 mm. This allows for particularly gas-efficient laser cutting processes.

[0019] An advantageous aspect of the invention provides that the area ratio of the nozzle channel between the constriction and the nozzle inlet is less than 40%, in particular less than 30%, preferably less than 25%.

[0020] An advantageous aspect of the invention provides that the area ratio of the nozzle channel between the nozzle outlet and the constriction is greater than 120%, in particular greater than 150%, preferably greater than 200%. This ensures sufficient compression of the cutting gas and / or a back pressure above 2 bar.

[0021] An advantageous aspect of the invention provides that a cylinder section with a constant cylinder diameter is provided at the nozzle inlet and / or at the nozzle outlet and / or at the constriction. Accordingly, the nozzle length of the Laval nozzle can be individually adjusted to the laser processing process.

[0022] An advantageous aspect of the invention provides that the nozzle channel has an elliptical or rotationally symmetrical cross-section. With a rotationally symmetrical cross-section, the Laval nozzle can be used regardless of direction. The problem underlying the invention is also solved by a method with the features of claim 11. The invention relates to a method for laser cutting a workpiece with a previously described Laval nozzle, wherein a first laser beam and / or a second laser beam and a gas jet are directed from the Laval nozzle along a flow direction onto an entry surface of the workpiece, and a working distance between the Laval nozzle and the entry surface is set in a range between 1 mm and 50 mm.

[0023] This offers the advantage that, unlike prior art, the Laval nozzle can maintain a significantly greater working distance from the workpiece. In this case, the planning and programming of the laser cutting nozzle's movement path is considerably simplified, as there is much greater flexibility in the working distance. Furthermore, the laser cutting nozzle's movement path can be ground down. Due to the greater working distance, the risk of collision with the workpiece is significantly reduced. Moreover, because the back pressure is provided, a distance control for the working distance can be omitted, resulting in cost savings. This also provides a solution for 2D and / or 3D laser processing devices.

[0024] An advantageous aspect of the invention provides that a back pressure of the gas jet of more than 2 bar acts at the inlet surface. Surprisingly, tests have shown that consistent cutting quality can be achieved even at a working distance of up to 50 mm if the back pressure at the inlet surface, particularly throughout, is more than 2 bar.

[0025] The back pressure is preferably adjusted depending on the boiler pressure acting in the Laval nozzle and / or the internal geometry of the Laval nozzle. It is advantageous if the back pressure is more than 2 bar over a substantial part, in particular over the entire part, of the process. The workpiece is preferably cut along a three-dimensional cutting line. The laser cutting is preferably carried out by laser melt cutting. In laser melt cutting, the workpiece material is melted to form a cutting gap and blown out of the cutting gap in liquid form. The workpiece can be a sheet metal part, in particular a three-dimensionally shaped sheet metal part. The workpiece preferably consists of a metallic and / or electrically conductive material. The process according to the invention is preferably carried out with a laser processing device according to the invention described below.

[0026] In laser cutting, a first laser beam, a second laser beam, and a gas jet are directed at an entry surface of the workpiece. The two laser beams and the gas jet melt and remove material from the workpiece, creating a kerf. The entry surface is the surface of the workpiece onto which the beams strike. After the kerf has formed, portions of the beams typically exit the workpiece at the opposite exit surface. Typically, the first and second laser beams are each formed by a single laser beam. Alternatively, however, the first and / or, in particular, the second laser beam can each consist of several partial beams. The two laser beams can be generated with a common laser light source and separated from each other by a beam splitter.Alternatively, each of the two laser beams can be generated with a separate laser light source. The cutting gas directed towards the entry surface in the gas jet or blown into the cutting gap can be, for example, nitrogen or compressed air. In special cases, the cutting gas can also be argon or oxygen.

[0027] It is advantageous if the two laser beams emerge from a multi-core fiber with a first fiber core for the first laser beam and a second fiber core for the second laser beam. The multi-core fiber can have fibers running parallel to each other. Preferably, the second fiber core surrounds the first.

[0028] Fiber core. In other words, the first fiber core is arranged radially within the second fiber core. The second fiber core is thus formed as a ring fiber and surrounds the first fiber core in a ring shape. In particular, the first and second fiber cores can be concentric with each other. This allows the cutting gas to be coupled more efficiently into the kerf.

[0029] The first fiber core, from which the first laser beam emerges, preferably has a fiber diameter of at least 30 pm and / or at most 100 pm, in particular 75 pm. The second fiber core, from which the second laser beam emerges, preferably has a fiber diameter of at least 150 pm and / or at most 350 pm, in particular 300 pm.

[0030] It is further advantageous if the working distance between the inlet surface and the Laval nozzle is greater than 2 mm, in particular greater than 5 mm, preferably greater than 6 mm, and / or set in a range between 1 mm and 50 mm, preferably between 2 mm and 20 mm. The working distance can preferably be set between 1 mm and 8 mm. Consequently, a substantially constant back pressure is ensured.

[0031] An advantageous further development provides that the dynamic pressure of the gas jet at the inlet surface is set to more than 3 bar, in particular more than 3.5 bar, preferably more than 4 bar or 5 bar. This ensures that the workpiece material is reliably blown out of the cutting gap, especially without a burr forming on the exit surface. Preferably, the gas jet is directed parallel to the jet direction towards the inlet surface.

[0032] The workpiece to be processed has a thickness that is preferably equal to or less than 20 mm, particularly equal to or less than 8 mm, and preferably equal to or less than 2 mm. The workpiece can preferably be metallic or non-metallic, in particular made of LSN-CFRP or LSN non-metals. If the workpiece is non-metallic, the tracking can be coarser. It is advantageous if the working distance is varied during laser cutting. The variation of the working distance is preferably at least 1 mm, 2 mm, 3 mm, 4 mm, 7 mm, or 10 mm. This allows for greater flexibility in planning the movement path. Furthermore, the working distance can be varied depending on the processing conditions, in particular workpiece thickness, cut quality, linear cutting / corner cutting, etc.It is advantageous if, when changing the working distance, the focus position of the first laser beam and / or the second laser beam, in particular the focus position of the laser beam waist, is adjusted relative to the entrance surface. Due to the variation of the working distance, the movement path of the Laval nozzle can be further refined.

[0033] It is further advantageous if the laser beam divergence of the first light beam and / or the second light beam is set to 100 mrad or less. This ensures high process stability, particularly when using laser beams with increased Rayleigh length.

[0034] Preferably, a cutting gas with a boiler pressure of at least 12 bar, in particular at least 16 bar and / or at most 35 bar, in particular at most 22 bar, is supplied to the inlet side of the Laval nozzle to provide the gas jet.

[0035] It is also advantageous if the beam parameter product of the first laser beam and / or the second laser beam is set to be equal to or less than 4 mm*mrad.

[0036] The problem underlying the invention is also solved by a laser processing device with the features of claim 13. The invention relates to a laser processing device for laser processing, in particular for laser cutting, of a workpiece with a previously described gas jet running parallel to a flow direction.

[0037] An advantageous aspect of the invention provides that the laser processing device has a laser light source with a first fiber core and a second fiber core surrounding the first fiber core, and wherein, in particular, the first fiber core can be or is supplied with laser radiation to generate a first laser beam running parallel to a flow direction and the second fiber core can be supplied with laser radiation to generate a second laser beam running parallel to the beam direction and surrounding the first laser beam in a ring shape.

[0038] An advantageous aspect of the invention provides that the laser processing device is configured such that, when a working distance between the Laval nozzle and an entry surface of the workpiece is in a range between 2 mm and 50 mm, the stagnation pressure of the gas jet on the entry surface is more than 2 bar.

[0039] Furthermore, the invention can also be implemented by using a laser processing device for processing, preferably laser cutting, workpieces, particularly metallic and / or non-metallic workpieces, with a variable working distance. The laser processing device comprises a laser source and a Laval nozzle as previously described. The working distance extends between an entry surface of the workpiece and, in particular, an opening of the Laval nozzle, and lies in a range between 1 mm and 50 mm, preferably between 2 mm and 50 mm, and more specifically between 2 mm and 20 mm. The working distance can preferably be set between 1 mm and 8 mm. Laser cutting systems known from the prior art are used for laser cutting with a working distance of less than 5 mm, particularly less than 3 mm.The laser source comprises a first fiber core and a second fiber core surrounding the first fiber core. The first fiber core can be or is illuminated with laser radiation to generate a first laser beam parallel to a beam direction, and the second fiber core can generate a second laser beam parallel to the beam direction, surrounding the first laser beam in a ring-like fashion. Based on the surprising findings of the investigations, a laser processing device can also be used safely with a working distance greater than 2 mm, thereby reducing the risk of collision with the workpiece.

[0040] The description also includes a cutting head with an integrated cutting gas supply and a previously described Laval nozzle.

[0041] Further advantages, features, and details will become apparent from the following description, in which various embodiments of the invention are illustrated with reference to the drawing. The features mentioned in the claims and the description can each be essential to the invention individually or in any combination.

[0042] They show:

[0043] Fig. 1 shows a schematic view of a method for

[0044] Laser cutting;

[0045] Fig. 2 a schematic cross-sectional view through a

[0046] More core fibers of a laser light source;

[0047] Fig. 3 shows a schematic cross-sectional view through a first

[0048] laser beam and by a second laser beam; and

[0049] Fig. 4-6 shows a Laval nozzle according to the invention.

[0050] Fig. 1 shows a laser processing device 10 in the form of a laser cutting device in a method for processing, in particular laser cutting, a workpiece 12. In the laser cutting method, a cutting gap 14 is introduced into the workpiece 12 to cut the workpiece 12. The workpiece 12 is sheet-shaped and has a workpiece thickness 16, which is less than 6 mm, in particular less than 4 mm, and preferably less than 2 mm. The workpiece 12 can be three-dimensionally curved, at least in some areas, in a manner not shown in detail. To create the cutting gap 14 in the workpiece 12, a first laser beam 18, a second laser beam 20, and a gas jet 22 are directed along a flow direction 66 onto an entry surface 24 of the workpiece 12, as shown in Fig. 1. The two laser beams 18, 20, and typically also the gas jet 22, overlap each other in a cutting zone 26.In laser melt cutting, the material of the workpiece 12 is liquefied in the cutting zone 26 and driven out by the gas jet 22, forming the cutting gap 14.

[0051] The first laser beam 18, the second laser beam 20, and the gas jet 22 are generated and directed onto the entry surface 24 of the workpiece 12. The gas jet 22 and the two laser beams 18 and 20 exit a Laval nozzle 28. The two laser beams 18 and 20 and the gas jet 22 overlap in the cutting zone 26. The cutting gap 14 in the workpiece 12 is created by the two laser beams 18 and 20 and the gas jet 22.

[0052] The two laser beams 18, 20 are generated by a laser light source device 30, as shown in Fig. 1. The laser light source device 30 comprises a single laser light source 32, for example, a solid-state laser. The laser light source 32 emits a single output laser beam 34. In a beam splitter 36, the output laser beam 34 is split into the first laser beam 18 and the second laser beam 20. The two laser beams 18, 20 are guided by a multi-core fiber 38 to an optic 40, from where the laser beams 18, 20 then enter the Laval nozzle 28 and are directed from there onto the entrance surface 24.

[0053] The multi-core fiber 38, as shown in Fig. 2, has a first fiber core 42 for the first laser beam 18 and a second fiber core 44 for the second laser beam 20. The second fiber core 44 is configured as a ring fiber that surrounds the first fiber core 42. The first and second fiber cores 44, 44 can be arranged concentrically. The first fiber core 42, from which the first laser beam 18 emerges, preferably has a first fiber diameter 46 of at least 30 pm and / or at most 100 pm, in particular 75 pm. The second fiber core 44, from which the second laser beam 20 emerges, preferably has a second fiber diameter 48 of at least 150 pm and / or at most 350 pm, in particular 300 pm. The focal points of the two laser beams 18, 20 can be located at a single point.

[0054] As shown in Fig. 3, the first beam diameter 50 of the first laser beam 18 is smaller than the second beam diameter 52 of the second laser beam 20 in the area of ​​the workpiece 12 to be cut. In particular, the first focus diameter 54 of the first laser beam 18 is smaller than the second focus diameter 56 of the second laser beam 20. The first focus diameter 54 of the second laser beam 20 can be four times larger than the second focus diameter 56 of the first laser beam 18. The beam parameter product of the first laser beam 18 and / or the second laser beam 20 is less than 5 mm*mrad, for example, 2 mm*mrad or 4 mm*mrad.

[0055] The laser beam divergence of the first laser beam 18 and / or the second laser beam 20 is preferably less than 100 mrad. The laser beam divergence and / or the beam diameters 50, 52 approach each other and are of equal size in the far field.

[0056] The power output of the second laser beam 20 is less than 40% of the total laser power (the sum of the laser powers of the two laser beams 18 and 20). For example, with a workpiece thickness 16 of 2 mm, the power output of the second laser beam 20 can be 5%. This 5% laser power of the second laser beam 20 can form a small radius at the kerf entry point, allowing the cutting gas to be efficiently coupled into even a narrow kerf. With such a laser beam configuration, cutting can be performed faster with a narrow kerf, while still achieving burr-free cutting. This applies to both low and high feed rates. Preferably, the working distance 64 is greater than 1 mm, particularly greater than 5 mm, more preferably greater than 6 mm, and / or set in a range between 1 mm and 50 mm, preferably between 2 mm and 50 mm.The working distance 64 can preferably be set between 1 mm and 8 mm.

[0057] Preferably, the back pressure is set to more than 3 bar, in particular more than 3.5 bar, and preferably more than 4 bar. This ensures that the workpiece material 12 is reliably blown out of the cutting gap 14, especially without a burr forming on the exit surface. To provide the back pressure, the Laval nozzle 28 can be supplied with a cutting gas at a tank pressure of at least 12 bar, in particular 15 bar. By using a 1.6 mm nozzle and / or a tank pressure of 12 bar, a reduction in cutting gas consumption of 50% can be achieved compared to conventional systems. This results in a significant reduction in operating costs for the laser processing device 10.

[0058] As shown in Fig. 1, the first laser beam 18, the second laser beam 20, and the gas jet 22 are guided coaxially and / or parallel to the beam direction 62 through the Laval nozzle 28 onto the entry surface 24 of the workpiece 12. This results in optimal cutting quality even at larger working distances 64 up to 50 mm. In this case, the planning and programming of the movement path of the Laval nozzle 28 is considerably simplified, as there is significantly greater flexibility in the working distance 64. Furthermore, the movement path of the Laval nozzle 28 can be ground down. Due to the larger working distance 64, the risk of collision with the workpiece 12 is significantly reduced. Moreover, because the back pressure is provided, a distance control for the working distance 64 is unnecessary, leading to cost savings.

[0059] According to Figures 4 to 6, a laser cutting nozzle in the form of a Laval nozzle 28 is used, which has a substantially conical outer contour 58 and a Laval-shaped inner contour 60. The Laval nozzle 28 is formed in one piece and is preferably made of a metal or of a plastic using an additive manufacturing process. The Laval nozzle 28 is preferably rotationally symmetrical with respect to the flow direction 66.

[0060] The Laval nozzle 28 is preferably designed such that a homogeneous gas flow with a substantially constant dynamic pressure of more than 2 bar is provided over a working distance 64 of between 2 mm and 50 mm extending between the Laval nozzle 28 and the inlet surface 24 of the workpiece 12. The Laval nozzle 28 is preferably designed for an ambient pressure of less than 2 bar, preferably for 1.013 bar.

[0061] The Laval nozzle 28 has a nozzle inlet 68 with an inlet diameter 70 and a nozzle outlet 72 with an outlet diameter 74. Furthermore, the Laval nozzle 28 has a nozzle channel 76, which fluidically connects the nozzle inlet 68 and the nozzle outlet 72 and extends along a flow direction 66. The channel 76 comprises a compression section 78 and an expansion section 80. The compression section 78 tapers continuously along the flow direction 66 towards a constriction 82 with a constriction diameter 84. The expansion section 80 tapers continuously against the flow direction 66 towards the constriction 82. By definition, the constriction 82 forms the smallest diameter of the inner contour 60. The compression section 78 has a compression length 86 and the expansion section 80 has an expansion length 88.The ratio between the compression length 86 and the expansion length 88 is less than 0.6, particularly in a range between 0.2 and 0.55, especially at 0.5.

[0062] The compression length 86 is in a range between 2 mm and 10 mm, in particular between 3 mm and 7 mm, preferably 5 mm. The expansion length 88 is in a range between 5 mm and 20 mm, in particular between 8 mm and 15 mm, preferably between 10 mm and 15 mm, preferably 10 mm.

[0063] The Laval nozzle 28 has a connection from the nozzle inlet 68 to the

[0064] Nozzle outlet 72 extending nozzle length 90, wherein the nozzle length 90 is in a range between 11.5 mm and 20 mm, in particular between 13 mm and 17 mm, preferably at 15 mm.

[0065] The constriction diameter 84 is in a range between 1 mm and 3 mm, in particular 1.4 mm - 2.6 mm, preferably at least 1.8 mm.

[0066] The Laval nozzle 28 has an area ratio of the nozzle channel 76 between the constriction 82 and the nozzle inlet 68 that is less than 40%, in particular less than 30%, preferably less than 25%. The Laval nozzle 28 additionally or alternatively has an area ratio of the nozzle channel 76 between the nozzle outlet 72 and the constriction 82 that is greater than 120%, in particular greater than 150%, preferably greater than 200%.

[0067] Reference numeral list for laser processing: 50 First beam diameter, device; 52 Second beam diameter, workpiece; 54 First focus diameter, cutting gap; 56 Second focus diameter, workpiece thickness; 30; 58 Outer contour of first laser beam; 60 Inner contour of second laser beam; 62 Beam direction, gas jet; 64 Working distance, inlet surface; 66 Flow direction, cutting zone; 35; 68 Nozzle inlet, Laval nozzle; 70 Inlet diameter, laser light sources; 72 Nozzle outlet, device; 74 Outlet diameter, laser light source; 76 Nozzle channel, output laser beam 78 Compression section beam splitter 80 Expansion section multi-core fiber 82 Constriction optics 84 Constriction diameter first fiber core 86 Compression length second fiber core 45 88 Expansion length first fiber diameter 90 Nozzle length second fiber diameter

Claims

Patent claims 1. Laval nozzle (28) for a laser processing device (10) for processing a workpiece (12) by means of a laser beam (18, 20), the Laval nozzle (28) comprising: a nozzle inlet (68) with an inlet diameter (70) and a nozzle outlet (72) with an outlet diameter (74), a nozzle channel (76) fluidically connecting the nozzle inlet (68) and the nozzle outlet (72) and extending along a flow direction (66) with a compression section (78) and an expansion section (80), wherein the compression section (78) tapers along the flow direction (66) and the expansion section (80) tapers towards a constriction (82) with a constriction diameter (84) opposite the flow direction (66), wherein the compression section (78) has a compression length (86) and the expansion section (80) has an expansion length (88) exhibits, wherein the ratio between the compression length (86) and the expansion length (88) is less than 0.

6.

2. Laval nozzle (28) according to claim 1, wherein the ratio between the compression length (86) and the expansion length (88) is in a range between 0.2 and 0.55, in particular 0.

5.

3. Laval nozzle (28) according to claim 1 or 2, wherein the tapering of the compression section (78) and / or the expansion section (80) is continuous.

4. Laval nozzle (28) according to claim 1 or 2, wherein the compression length (86) is in a range between 2 mm and 10 mm, in particular between 3 mm and 7 mm, preferably at 5 mm, and / or wherein the expansion length (88) is in a The range is between 5 mm and 20 mm, in particular between 8 mm and 15 mm, preferably between 10 mm and 15 mm, preferably at 10 mm.

5. Laval nozzle (28) according to one of the preceding claims, wherein the Laval nozzle (28) has a nozzle length (90) extending between the nozzle inlet (68) and the nozzle outlet (72), wherein the nozzle length (90) is in a range between 11.5 mm and 20 mm, in particular between 13 mm and 17 mm, preferably at 15 mm.

6. Laval nozzle (28) according to one of the preceding claims, wherein the compression section (78) extends from the nozzle inlet (68) to the constriction (82) and / or wherein the expansion section (80) extends from the constriction (82) to the nozzle outlet (72).

7. Laval nozzle (28) according to one of the preceding claims, wherein the constriction diameter (84) is in a range between 1 mm and 3 mm, in particular between 1.4 mm and 2.6 mm, preferably at 1.8 mm.

8. Laval nozzle (28) according to one of the preceding claims, wherein the area ratio of the nozzle channel (76) between the constriction (82) and the nozzle inlet (68) is less than 40%, in particular less than 30%, preferably less than 25%, and / or between the nozzle outlet (72) and the constriction (82) is greater than 120%, in particular greater than 150%, preferably greater than 200%.

9. Laval nozzle (28) according to one of the preceding claims, wherein a cylinder section with a constant cylinder diameter is provided at the nozzle inlet (68) and / or at the nozzle outlet (72) and / or at the constriction (82). 19 10. Laval nozzle (28) according to one of the preceding claims, wherein the nozzle channel (76) has an elliptical, rectangular, square, star-shaped or rotationally symmetrical cross-section.

11. Method for laser processing, in particular laser cutting, of a workpiece (12) with a Laval nozzle (28) according to one of claims 1 to 10, wherein a first laser beam (18) and / or a second laser beam (20) and a gas jet (22) are directed from the Laval nozzle (28) along a flow direction (66) onto an entry surface (24) of the workpiece (12), wherein a working distance (64) between the Laval nozzle (28) and the entry surface (24) is set in a range between 1 mm and 50 mm.

12. Method according to claim 11, wherein a dynamic pressure of the gas jet (22) of more than 2 bar acts on the inlet surface (24).

13. Laser processing device (10) for laser processing, in particular for laser cutting, of a workpiece (12) with a Laval nozzle (28) according to one of claims 1 to 10 for generating a gas jet (22) running parallel to a flow direction (66).

14. Laser processing device (10) according to claim 13, wherein the laser processing device (10) comprises a laser light source (32) with a first fiber core (42) and a second fiber core (44) surrounding the first fiber core (42), and wherein in particular the first fiber core (42) is configured to generate a first laser beam (18) parallel to a flow direction (66) and the second fiber core (44) is configured to generate a first laser beam (18) parallel to the beam direction (62) and in a ring shape. 20 surrounding second laser beam (20) can be exposed to or is exposed to laser radiation.

15. Laser processing device (10) according to claim 13 or 14, wherein the laser processing device (10) is configured such that when a working distance (64) between the Laval nozzle (28) and an entry surface (24) of the workpiece (12) is in a range between 2 mm and 50 mm, a stagnation pressure of the gas jet (22) on the entry surface (24) is more than 2 bar.

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