Nozzle for laser machining with high focal positions

Abstract

The invention relates to a nozzle for use in a laser machining system, the nozzle comprising: a main body having a through-opening which extends through the main body along a nozzle longitudinal axis from a first end to a second end of the main body; wherein the through-opening has a first diameter in the region of the first end; wherein the through-opening forms, in the region of the second end, a parallel-walled reflection section on the inside of the main body, the length of said reflection section being at least 2 mm; wherein the through-opening has, in the reflection section, a minimal second diameter which is smaller than the first diameter; wherein the main body has a coupling section at the first end; and wherein the main body has a step on its outer circumference adjacent to the coupling section, said step extending in the radial direction around the through-opening and forming a circumferential cooling surface which is oriented substantially perpendicular to the nozzle longitudinal axis. The invention further relates to a laser machining system comprising the nozzle, and to a method for laser machining using the nozzle.

Description

[0001] Nozzle for laser processing with high focus positions

[0002] Field of the invention

[0003] The present invention relates to the field of laser processing. In particular, the invention relates to a nozzle for use in a laser processing system, a laser processing system comprising the nozzle, and a laser processing method using the nozzle.

[0004] State of the art

[0005] There are laser cutting processes in which it is advantageous if the focus of the laser beam lies within the cutting nozzle. If cutting nozzles with a converging inner contour are used in such cases, it can happen that edge regions of the laser beam are reflected or absorbed on the inside of the nozzle in the area of ​​the nozzle orifice. One such case is illustrated schematically in Figures 2a and 2b. On the one hand, these reflections can change the divergence of the laser beam in the edge regions, which can have a disruptive effect on the cutting process. On the other hand, the cutting nozzle can be harmfully heated by absorbed laser radiation.

[0006] DE 40 16 199 A1 discloses a nozzle for a laser cutting process in which the focal point of the laser beam is located inside the nozzle. The cutting nozzle has two characteristic areas on its inside: a convergence area and a parallel-walled or diverging orifice area extending in the direction of beam propagation, through which the laser beam passes together with a cutting gas before exiting the nozzle. The nozzle allows reflection of the focused laser beam from the inner wall of the nozzle in the orifice area.

[0007] The present invention is based on the object of further improving the state of the art. In particular, a nozzle for laser processing with high focal positions is to be provided, which ensures high process quality in laser processing and, in particular, in laser cutting. The invention

[0008] To achieve the object underlying the invention, a nozzle for use in a laser processing system is provided. The laser processing system can preferably be a laser cutting system in which a laser beam is focused in a laser cutting head by means of focusing optics and, together with a cutting gas jet, is directed onto a workpiece to be cut via the nozzle, which can be attached to the laser cutting head.

[0009] The nozzle comprises a base body with a through-opening that extends through the base body along a longitudinal axis of the nozzle from a first end to a second end of the base body. The base body can preferably have a rotationally symmetrical shape with respect to the longitudinal axis of the nozzle. The nozzle channel can preferably have a circular cross-section.

[0010] The through-opening has a first diameter in the region of the first end. Furthermore, the through-opening forms a parallel-walled reflection section on the inside of the base body in the region of the second end, which has a length (in the direction of the nozzle's longitudinal axis) of at least 2 mm. The through-opening has a minimal, second diameter in the reflection section that is smaller than the first diameter. The term "parallel-walled" encompasses slight inclinations of the reflection section (or of the inner wall of the base body in the reflection section) of a few degrees, for example, of up to 2.5° relative to the nozzle's longitudinal axis.

[0011] At its first end, the base body has a coupling section. In the coupling section, the base body is designed for coupling to a nozzle holder of a laser processing head, in particular a laser cutting head. For this purpose, the base body can preferably have a thread in the coupling section. Adjacent to the coupling section, the base body has a step on its outer circumference that extends radially around the through-opening and forms a circumferential cooling surface oriented substantially perpendicular to the nozzle's longitudinal axis.

[0012] The nozzle is designed overall in such a way that edge regions of a laser beam whose focal point lies within the nozzle, specifically in front of the reflection section in the direction of beam propagation, can be reflected on the inner wall of the nozzle base body as it passes through the reflection section. Compared to a conical nozzle inner contour, this reduces the absorption of the laser radiation and thus the heating of the nozzle. The length of the reflection section is large enough to achieve these advantageous effects. If the through-opening in the reflection section has a circular cross-section, this advantageously improves the reflection properties in this region of the nozzle. In other words, in the reflection section, the base body can preferably have a cylindrical (possibly slightly conical) inner contour.

[0013] The nozzle according to the invention enables cutting with a comparatively large beam diameter within the nozzle, which allows high cutting speeds and good cutting edge quality to be achieved, particularly in the higher power range (e.g., with a laser power of 6 kW and above), especially when flame cutting metallic workpieces, especially structural steel, and less frequently also non-ferrous metals, using oxygen as the cutting gas. In particular, the beam diameter within the nozzle can be selected to be only slightly smaller than the diameter of the through-hole in the reflection section.

[0014] Despite the optimized inner contour of the nozzle compared to a nozzle with a conical nozzle opening, heating of the nozzle when laser radiation hits the reflection area cannot be completely avoided. Therefore, an appropriate cooling concept is required to ensure high dimensional stability of the nozzle during laser processing and / or to avoid, for example, tarnishing of the base body in the reflection area, which can negatively affect the absorption properties. To improve cooling, the nozzle according to the invention has the cooling surface. Heat is dissipated to the environment or to a cooling medium via the cooling surface. When the nozzle is in operation, the cooling surface is located in the immediate vicinity of a preferably actively cooled nozzle holder of a laser processing head. In this way, heat can be dissipated even more efficiently and the nozzle can be efficiently integrated into the active cooling of the laser processing head.

[0015] Overall, when using a nozzle according to the invention for laser processing, in particular for laser cutting with high laser power, with high focus positions, an improved process quality can be achieved compared to the prior art.

[0016] Preferably, the second diameter of the through-opening is at least 1.4 mm, preferably at least 1.6 mm.

[0017] The length of the reflection section of the through hole can be at most

[0018] 10 mm, preferably a maximum of 7.5 mm. It has been shown that an excessively long reflection section, particularly during laser cutting, has a negative impact on the machining process, especially when piercing the material to be cut. According to a preferred variant, the length of the reflection section can be between 2 mm and 5 mm. A parallel-walled reflection section that is too long can have a disruptive effect if the machining process is to be observed through the nozzle using a camera.

[0019] The cooling surface of the base body can preferably have a width of at least 4 mm. For example, the cooling surface of the base body can have a width - which corresponds in particular to a difference between the inner diameter and the outer diameter of the cooling surface - of approximately 5 mm. The cooling effect can be improved by enlarging the cooling surface. The base body of the nozzle can preferably have a thickness (or a wall thickness) of at least 2 mm, preferably at least 3 mm, in a region between the cooling surface and the second end of the base body. A solid design of the nozzle with the minimum thickness or minimum strength of the nozzle wall formed by the base body can ensure sufficient heat dissipation from the second end to the cooling surface and to the coupling section. In the coupling section, i.e. between the cooling surface and the first end of the base body, the base body can have a smaller thickness orwall thickness, since during operation of the nozzle it is in direct mechanical contact with a nozzle holder, through which the heat is dissipated.

[0020] The base body preferably has a thread in the coupling section. The thread can be used to connect the nozzle to a nozzle holder of a laser processing head. Furthermore, the base body can have a chamfer at the transition between the coupling section and the circumferential step, which forms a stop surface when the nozzle is screwed into the nozzle holder. The chamfer or stop bevel is preferably dimensioned such that a gap remains between the cooling surface and the nozzle holder when the nozzle is screwed into the nozzle holder. The gap serves to prevent stresses due to different thermal expansions. Furthermore, the chamfer can serve to center the nozzle when screwing it into the nozzle holder of the processing head.

[0021] The base body of the nozzle can preferably be constructed from a material that has a high thermal conductivity, for example of at least 300 W / mK, preferably of at least 350 W / mK, for example of approximately 355 W / mK. In this way, heat dissipation from the nozzle can be improved. Furthermore, for implementing a distance sensor for a laser processing method, the base body can preferably be constructed from an electrically conductive material. In particular, the base body can be made of copper or a copper alloy. Furthermore, the base body is preferably formed in one piece. The base body can have a surface roughness on its inner surface in the region of the reflection section of at most Rz 10, preferably at most Rz 8, for example of Rz 6 or less. By reducing the surface roughness, the reflection properties of the nozzle in this region can be improved.By improving the reflection properties in the reflection area, the heating of the nozzle during operation can be further reduced. Preferably, the surface of the base body in the area of ​​the reflection section can be polished. Alternatively or additionally, the base body in the area of ​​the reflection section can have a highly reflective surface coating, for example, a nickel-based coating. Nickel plating can, for example, counteract a deterioration in the reflection properties of the base body in the area of ​​the reflection section (e.g., due to the formation of tarnish) during nozzle operation.

[0022] The base body can have an outer contour which, starting from the first end, can be divided into further sections after the coupling section. After the coupling section, the base body can therefore have an engagement section which, starting from the step, extends towards the second end, wherein the base body has its largest outer diameter in the engagement section and / or wherein the base body has a polygonal cross-section or a polygonal outer contour in the engagement section. The engagement section can preferably be designed such that it can be gripped by means of a gripping tool (such as an open-end wrench) and inserted, in particular screwed, into the socket of a nozzle holder. This can be done, for example, automatically by means of a nozzle changer, as described, for example, in EP 2 589 458 B1 by the applicant.Preferably, the base body has 6 flat engagement surfaces along its outer circumference in the engagement section, wherein two engagement surfaces adjacent in the circumferential direction are arranged at an angle of 60° to one another. The distance between two opposite engagement surfaces is preferably between 23 mm and 25 mm, in particular between 23.9 mm and 24 mm. Further towards the second end, the nozzle base body can have a bearing section in which the outer diameter of the base body preferably tapers continuously. In other words, the base body has a conical shape in the bearing section that tapers towards the second end. The bearing section can be divided into several stages into regions with different cone angles, wherein the cone angle preferably becomes smaller towards the second end compared to the nozzle longitudinal axis.The conically tapered circumferential surface in the bearing section of the base body can serve as a contact surface for a nozzle holder, for example in a nozzle changer.

[0023] A parallel-walled, preferably cylindrical, transition section can adjoin the support section toward the second end of the base body. The transition section can preferably have a length that is at least as long as the length of the reflection section of the through-opening, wherein the diameter of the base body in the transition section can be at least 8 mm, preferably at least 10 mm.

[0024] The transition section can preferably be followed by an orifice section in which the diameter of the base body tapers from the transition section to the second end of the base body. In other words, the orifice section forms a chamfer at the second end of the base body. The base body preferably has its smallest outer diameter at its second end. The (smallest) outer diameter at the second end of the base body, i.e. adjacent to a nozzle end face, is preferably at least 1 mm larger, more preferably at least 3 mm larger, than the inner diameter of the base body in the reflection region. The angle of the chamfer forming the orifice section is at least 30° and preferably between 40° and 60° relative to the nozzle longitudinal axis, or a maximum of 60° and preferably between 30° and 50° relative to the nozzle end face. In this way, the required minimum wall thickness of the base body can be maintained.One advantage of the chamfer is that the nozzle can glide better over unevenness on the workpiece surface or over cut-out workpiece parts that are slightly tilted in the residual skeleton.

[0025] A cumulative length of the transition section and the mouth section of the base body along the nozzle longitudinal axis can be at least 8 mm, preferably between 8 mm and 11 mm.

[0026] Overall, the base body can have a length between 24 mm and 27 mm, preferably approximately 25.5 mm. Furthermore, the outer contour of the base body preferably has an outer diameter of no more than 18 mm in a region extending from the second end of the base body over at least 15 mm and at most 20 mm in the direction of the nozzle's longitudinal axis, in order to enable a compact design of the nozzle and to minimize any interference contour of the nozzle adjacent to the nozzle outlet opening (collision with parts tilted during laser cutting).

[0027] The preferred boundary conditions for the outer diameter of the nozzle body ensure that the wall thickness of the nozzle in the area of ​​the cylindrical nozzle channel is sufficiently large to allow heat dissipation along the nozzle wall in the direction of the coupling section and the cooling surface.

[0028] The main body of the nozzle can have an inner contour formed by the through-opening, which, in addition to the reflection section at the second end of the main body, further comprises a funnel-shaped convergence section that opens into the reflection section. The main body can have a maximum inner diameter at the end of the convergence section remote from the reflection section. Furthermore, the inner surface of the main body in the convergence section can have a preferably constant angle of inclination of at most 25°, preferably at most 20°, relative to the nozzle's longitudinal axis in order not to compromise the required minimum wall thickness of the main body. Finally, the convergence region can have a length that is greater than the length of the reflection section. In this way, a uniform gas flow of the cutting gas through the nozzle can be achieved when used in a laser cutting system.Overall, the convergence region can have a maximum length equal to the difference between the length of the base body and the length of the reflection section.

[0029] In addition to the convergence section and the reflection section, the inner contour of the base body may further comprise a parallel-walled connecting section extending from the first end of the base body to the beginning of the convergence section.

[0030] In principle, it may be preferable for the nozzle base body to have a circular cross-section on the outside, at least in the transition section and the orifice section, and on the inside, at least in the reflection section. In this way, the wall thickness of the base body can be maximized in the critical area of ​​the reflection section, where the base body heats up particularly strongly during operation at high focal positions, while simultaneously maintaining the smallest possible outer diameter of the nozzle.

[0031] To further improve heat dissipation, the nozzle can further comprise a heat-conducting element made of a flexible material that can be attached to the cooling surface of the base body. In the context of the present invention, a flexible material can be understood to mean a material with a modulus of elasticity between 400 MPa and 1100 MPa. During operation of the nozzle, the heat-conducting element can therefore be arranged in the gap between the cooling surface of the nozzle and a surface of a nozzle holder opposite the cooling surface. The heat-conducting element improves heat dissipation from the nozzle via the cooling surface to the (preferably actively cooled) nozzle holder, without significantly influencing the freedom of movement ensured by the gap between the cooling surface and the nozzle holder. The heat-conducting element can be made of graphite, for example. The heat-conducting element can be glued to the cooling surface or to the coupling section orbe clamped at the transition between the coupling section and the cooling surface. The heat-conducting element can preferably be annular or, for example, C-shaped and have a width that corresponds at most to the width of the cooling surface. The thickness of the heat-conducting element can preferably be selected such that it is somewhat larger (e.g., approximately 1 mm larger) than the thickness of the gap formed between the cooling surface and a surface of a nozzle holder opposite the cooling surface when the nozzle is attached to the nozzle holder (in particular, screwed into it).

[0032] Additionally or alternatively, the main body of the nozzle can have at least two cooling channels, which are preferably arranged at equal intervals along the circumference of the main body around the longitudinal axis of the nozzle. Each of the cooling channels can extend from the cooling surface of the step through the engagement section and open at the bearing section of the main body. During operation of the nozzle, the cooling channels can be supplied with a cooling liquid, in particular water, via a nozzle holder to which the nozzle can be attached. The cooling liquid can be passed under pressure through the cooling channels and directed onto the workpiece surface to be machined, e.g. to be cut. This creates a spray mist that cools the workpiece during machining. In this way, both the nozzle and the workpiece can be actively cooled during machining.

[0033] To achieve the object underlying the invention, a laser processing system for processing a workpiece using a laser beam is further provided. The laser processing system can, in particular, be a laser cutting system. The laser processing system comprises at least one laser beam source for generating a processing laser beam. Furthermore, the laser processing system comprises at least one laser processing head with laser processing optics, a nozzle holder, and a nozzle according to one of the variants described above. During operation of the laser processing system, the laser processing beam can be focused by means of the laser processing optics and directed through the nozzle holder and the nozzle onto the workpiece to be processed.

[0034] The nozzle holder preferably comprises a cooling device. The cooling device can, for example, comprise a channel system through which a cooling fluid (e.g., a cooling liquid or a cooling gas) can be conducted in order to remove heat from the nozzle holder and thus actively cool the nozzle holder.

[0035] To achieve the object underlying the invention, a method for laser processing a workpiece using a laser processing system is further provided, which has a nozzle according to one of the variants described above. According to the method, a laser beam is directed through the base body of the nozzle onto a workpiece to be processed, with a focus of the laser beam lying within the base body and above the reflection section, so that portions of the diverging laser beam are reflected within the reflection section on the inner wall of the base body.

[0036] Preferably, the divergence angle of the laser beam, at which the edge regions of the laser beam can impinge on the inner surface of the nozzle base body with a reflection section with exactly parallel walls, is at most 3°. In particular, the divergence angle of the laser beam can be between 1.5° and 2.75° (relative to the nozzle's longitudinal axis).

[0037] Preferably, the laser processing method is a flame cutting method, and the workpiece is preferably a plate- or tubular workpiece made of structural steel. The flame cutting method is characterized by the use of oxygen or an oxygen-containing gas as the cutting gas, which induces an exothermic reaction with the material to be cut during cutting, thus increasing the cutting performance.

[0038] Preferably, the laser processing process involves a (possibly cumulative)

[0039] A laser processing beam input power of at least 6 kW is used. As the laser power increases, the risk of critical heating of the nozzle also increases. Therefore, as the laser power increases, so do the requirements for an appropriate cooling concept for the nozzle, which is provided by the present invention.

[0040] When applying the method according to the invention as a flame cutting process, the focus diameter of the laser beam within the nozzle can preferably be between 170 pm and 1100 pm. Furthermore, a solid-state laser beam can preferably be used as the laser processing beam, which is guided from the laser beam source to the laser processing head by means of an optical fiber (a so-called transport fiber). The optical imaging of the fiber end onto the workpiece surface to be processed can be carried out with a magnification of 1.8 to 3, controlled by the processing optics in the laser processing head. Oxygen at a pressure between 0.4 bar and 1.2 bar, in particular, can be used as the process gas for laser flame cutting.

[0041] The present invention enables laser processing, particularly cutting, with a larger beam diameter within the nozzle. In laser cutting, especially in laser flame cutting with oxygen as the process gas, higher laser powers of at least 6 kW can be used, resulting in higher cutting speeds while maintaining good cutting edge quality.

[0042] Examples of implementation

[0043] The following description of preferred embodiments, in conjunction with the drawings, serves to explain the invention in more detail.

[0044] They show:

[0045] Fig. 1 shows a laser processing head suitable for receiving a nozzle according to the invention; Figs. 2a-b show schematic reflections on a nozzle inner wall according to the prior art;

[0046] Fig. 3 Schematic reflections on a nozzle inner wall according to the present invention;

[0047] Figs. 4a-c Different views of a nozzle according to the invention;

[0048] Figs. 5a-b Various nozzles according to the invention in a sectional view;

[0049] Figs. 6a-c Further nozzles according to the invention in a sectional view; and

[0050] Fig. 7 A laser processing system suitable for using a nozzle according to the invention.

[0051] For the sake of simplicity, features with the same or similar functions are provided with the same reference numerals in the figures.

[0052] Figure 1 shows a laser processing head 10 for a beam processing system, for example, a laser cutting system. The processing head 10 has a nozzle 12 for a processing beam, in this case a laser beam, and a process gas, in this case a cutting gas. During operation of the processing head 10, the laser beam and the process gas exit the nozzle 12 in a beam exit direction 14. Furthermore, the processing head 10 has several (covered here) optical elements, for example, one or more protective glasses and a focusing lens 18.

[0053] The machining head 10 also has a nozzle holder 20 with a cooling element. To cool the machining head 10, a cooling gas, for example, compressed air or nitrogen, is passed through the cooling element of the nozzle holder. A cooling gas connection 22 is provided for introducing the cooling gas into the cooling element 20. The process gas is introduced into the machining head 10 through a separate process gas connection 24. The cooling gas and the process gas are also guided separately within the machining head 10 so that they do not mix.

[0054] Figures 2a and 2b schematically show aspects of laser cutting with a high focus position using a conventional convergent nozzle 12. Due to the high focus position, the laser beam already diverges within the nozzle 12, so that edge regions of the laser beam – shown here as an example using line B – can impinge on the inner surface of the nozzle. Due to the large angle of incidence compared to the converging inner surface of the nozzle, a comparatively large portion of the grazing laser radiation can be absorbed in the nozzle, which leads to heating of the nozzle. Reflected laser radiation greatly expands the laser beam as it exits the nozzle, which can disrupt the cutting process. For example, edge regions of the laser beam can be deflected by reflection at the nozzle mouth in such a way that they miss the cutting gap and couple into the workpiece 68 to be cut next to the cutting gap (see Fig.2a), or at a large angle in the upper area of ​​the cutting gap into the workpiece 68 (see Fig. 2b). Both constellations have negative effects on the cutting process.

[0055] In contrast, Figure 3 schematically shows conditions during laser beam cutting with a high focus position using a nozzle 12 according to the invention. Due to a parallel-walled reflection section of the through-opening at the lower end of the nozzle 12, grazing edge regions B of the diverging laser beam are reflected into the cutting gap. Due to the small angle of incidence on the inner wall of the nozzle, the proportion of absorbed laser radiation in the nozzle is also reduced, thus counteracting excessive heating of the nozzle.

[0056] Figures 4a to 4c show several external views of a nozzle 12 according to the invention. The structure of the nozzle 12 shown is described in more detail below in conjunction with Figures 5a and 5b. Figures 5a and 5b show two different variants of a nozzle 12 according to the invention. In both cases, the nozzle 12 has a base body 120 with a through-opening 121. The nozzles 12 according to Figures 5a and 5b differ only in the design of the through-opening 121. The external shape of the nozzles 12 corresponds to the illustrations according to Figures 4a to 4c.

[0057] The base body 120 of the nozzle 12 extends rotationally symmetrically around the nozzle's longitudinal axis 12x and has a first, upper end 120-a and a second, lower end 120-z. The outer contour of the base body 120 can be divided into several sections, starting from the first end 120-a. At the first end 120-a, the base body 120 has a coupling section 120-1. A thread 122 is preferably formed in the coupling section 120-1, with which the nozzle 12 or its base body 120 can be screwed into a complementary thread of a nozzle holder. Following the coupling section 120-1, the diameter of the base body 120 increases abruptly in the form of a circumferential step, which introduces an engagement section 120-2. Several flat surfaces can be arranged on the engagement section 120-2, which are designed for the engagement of a tool for screwing in or loosening the nozzle 12. The engagement surfaces can be seen in Figures 4a-c.A cooling surface 123 is formed on the upper side of the step, through which heat can be dissipated from the base body 120 to the environment in the direction of a nozzle holder during operation of the nozzle 12. At the transition between the coupling section 120-1 and the cooling surface, a bevel 124 or chamfer 124 is formed, which acts as a stop and centering aid when screwing the nozzle 12 into the nozzle holder.

[0058] Adjacent to the engagement section 120-2 is a tapered support section 120-3. On the inclined support surface of this section, which may have several sub-sections with different cone angles, the nozzle 12 can be stored in a nozzle magazine when it is not currently attached to a laser processing head. Below the support section 120-3 is a parallel-walled transition section 120-4, which transitions into a tapered outlet section 120-5 at the second end of the base body 120.

[0059] On the inside, the base body 120 can also be divided into sections that are predetermined by the shape of the through-opening 121. At the second, lower end 120-z, a parallel-walled reflection section 121-3 is formed. Further up in the base body 120, the through-opening 121 forms a funnel-shaped convergence section 121-2, which opens into the reflection section 121-3. The convergence section 121-2 can basically extend from the first end 120-a of the base body 120 to the reflection section 121-3 (cf. Fig. 6c). In addition, however, as shown in Figures 5a and 5b, a parallel-walled connection section

[0060] 121-1 may be provided, which extends between the first end of the base body 120 and the convergence section 121-2.

[0061] The through-opening 121 has an inlet diameter 121-4 at the first end 120-a of the base body 120 and an outlet diameter 121-5 at the second end 120-z of the base body 120, wherein the outlet diameter 121-5 corresponds to the diameter of the through-opening 121 in the reflection section 121-3. The diameter 121-5 can preferably be at least 1.4 mm (e.g., between 1.6 mm and 3 mm), with a length of the reflection section 121-3 of at least 2 mm. For example, the diameter 121-5 can be between 1.5 mm and 1.6 mm, with a length of the reflection section of approximately 3.5 mm. If the inner wall of the base body 120 in the reflection region 121-3 has a slight angle with respect to the nozzle longitudinal axis 12x, the minimum inner diameter of the base body 120 can be decisive as diameter 121-5 in the reflection section 121-3.

[0062] The base body 120 can have a total length L of 23 mm to 27 mm, in particular of approximately 25.5 mm. In the transition section 120-4, the base body 120 can have an outer diameter 120-8 of at least 8 mm, preferably of at least 10 mm. Furthermore, the base body 120 can have a maximum thickness of 18 mm up to a distance of at least 15 mm and at most 20 mm from the second end 120-z. In the mouth region 120-5, the base body 120 can have a cone angle of at least 30° and at most 50° relative to the nozzle end face at the second end 120-z of the base body 120. The nozzle end face can be aligned substantially perpendicular to the nozzle longitudinal axis 12x and have an outer diameter 120-7 which is at least 1 mm, preferably at least 3 mm, larger than the (inner) diameter 121-5 in the reflection region 121-3 of the nozzle.The convergence region 121-2 in the nozzle interior can preferably have a cone angle of a maximum of 50°, preferably a maximum of 40°, and a length of at least 4 mm, preferably at least 6 mm, and even more preferably at least 8 mm. In the bearing section 120-3, the outer surface of the base body 120 can have an inclination of, for example, 50° relative to the nozzle longitudinal axis 12x in a first partial region bordering the engagement section 120-2. In a second partial region of the bearing section 120-3 bordering the transition section 120-4, the outer surface of the base body can be inclined by 33.55° relative to the nozzle longitudinal axis 12x.

[0063] Figures 6a to 6c show further nozzles 12 according to the invention, each in a sectional view. The nozzle 12 according to Figure 6a has a heat-conducting element 125a, which has a ring shape and is adhesively bonded to the cooling surface 123 of the base body 120. The nozzle 12 according to Figure 6b also has a heat-conducting element 125b, which is clamped to the base body 125b directly above the cooling surface 123. The heat-conducting elements can be made of graphite, for example, and serve to improve heat dissipation during operation of the nozzle 12 from the cooling surface 123 into an adjacent surface of a nozzle holder. The nozzle 12 according to Figure 6c has at least two cooling channels 126. During operation of the nozzle, the cooling channels 126 can be supplied with a cooling fluid, in particular with water, whereby the nozzle 12 and additionally the workpiece to be machined, onto which the cooling fluid is directed through the cooling channels, are actively cooled.Figure 7 shows a beam processing machine 62, here in the form of a laser cutting system. The laser cutting system 62 shown in Figure 7 has, by way of example, a CO2 laser as the beam source 64. Alternatively, the beam source can be, for example, a solid-state laser or a diode laser. The laser cutting machine 62 further has a movable processing head 10 (see Figure 1) and a (stationary) workpiece support 66 on which a workpiece 68 is arranged. A laser beam 70 is generated in the beam source 64 and guided from the beam source 64 to the processing head 10. The laser beam 70 is directed onto the workpiece 68 by means of focusing optics arranged in the processing head 10.

[0064] The laser cutting system 62 is connected to a gas supply device 72. The gas supply device 72 provides the process gas, in this case the cutting gas. The process gas can be nitrogen or oxygen, for example. Particularly in a flame cutting process, the process gas, in this case oxygen, can be supplied to the nozzle 12 of the processing head 10 at an overpressure of between approximately 0.4 bar and 1.2 bar.

[0065] The gas supply device 72, on the other hand, provides the cooling gas for the cooling element 20. The cooling gas can be, for example, nitrogen or compressed air.

[0066] The laser cutting system 62 further includes a machine control 74 programmed to move the processing head 10 relative to the workpiece 68, which is stationary here, according to a cutting contour. The machine control 74 also controls the power of the beam source 64, for example, for performing a flame cutting process.

Claims

Patent claims 1. Nozzle (12) for use in a laser processing system, the nozzle (12) comprising: A base body (120) with a through-opening (121) extending along a nozzle longitudinal axis (12x) from a first end (120-a) to a second end (120-z) of the base body (120) through the base body (120); Where the through-opening (121) in the region of the first end (120-a) has a first diameter (121-4); wherein the through-hole (121) in the region of the second end (120-z) forms a parallel-walled reflection section (121-3) on the inside of the base body (120) which has a length of at least 2 mm, wherein the through-hole (121) in the reflection section (121-3) has a minimum second diameter (121-5) which is smaller than the first diameter (121-4); wherein the basic body (120) has a coupling section (120-1) at the first end (120-a); and The base body (120) has a step on its outer circumference adjacent to the coupling section (120-1) which extends radially around the through-hole (121) and forms a circumferential cooling surface (123) which is oriented essentially perpendicular to the nozzle longitudinal axis (12x).

2. Nozzle (12) according to claim 1, wherein the second diameter (121-5) is at least 1.4 mm, preferably at least 1.6 mm.

3. Nozzle (12) according to one of the preceding claims, wherein the length of the reflection section (121-3) is at most 10 mm, preferably at most 7.5 mm.

4. Nozzle (12) according to one of the preceding claims, wherein the cooling surface (123) has a width of at least 4 mm.

5. Nozzle (12) according to one of the preceding claims, wherein the base body (120) has a thickness of at least 2 mm, preferably at least 3 mm, in a region between the cooling surface (123) and the second end (120-z).

6. Nozzle (12) according to one of the preceding claims, wherein the base body (120) has a thread in the coupling section (120-1); and wherein the base body (120) has a chamfer (124) at the transition between the coupling section (120-1) and the step, which forms a stop surface when screwing the nozzle (12) into a nozzle holder (20) of a laser processing head (10).

7. Nozzle (12) according to one of the preceding claims, wherein the base body (120) is made of a material having high thermal conductivity, in particular copper or a copper alloy.

8. Nozzle (12) according to one of the preceding claims, wherein the base body (120) has a surface roughness of at most Rz 10, preferably at most Rz 8, more preferably at most Rz 6 on its inner surface in the area of ​​the reflection section (121-3).

9. Nozzle (12) according to one of the preceding claims, wherein the base body (120) has an outer contour which, starting from the first end (120-a) after the coupling section (120-1), can be subdivided into the following sections: an engagement section (120-2) which extends from the step towards the second end (120-z), wherein the base body (120) has its largest outer diameter in the engagement section (120-2). and / or wherein the base body (120) has a polygonal cross-section in the engagement section (120-2); a bearing section (120-3) in which the outer diameter of the base body (120) preferably tapers continuously; a parallel-walled, preferably cylindrical transition section (120-4) wherein the transition section (120-4) has a length that is at least as long as the length of the reflection section (121-3) of the through-opening (121) and wherein the diameter of the base body (120) in the transition section (120-4) is at least 8 mm, preferably at least 10 mm; and an outlet section (120-5) in which the diameter of the base body (120) tapers from the transition section (120-4) to the second end (120-z) of the base body (120).

10. Nozzle (12) according to one of the preceding claims, wherein the base body (120) has an inner contour formed by the through-opening (121) which, in addition to the reflection section (121-3) at the second end (120-z) of the base body (120), further comprises a funnel-shaped convergence section (121-2) which opens into the reflection section (121-3); wherein the base body (120) has a maximum inner diameter at its end of the convergence section (121-2) furthest from the reflection section (121-3); wherein the inner surface of the base body (120) in the convergence section (121-2) has an inclination angle, preferably constant, of at most 50°, preferably at most 40°, relative to the nozzle longitudinal axis (12x); and / or wherein the convergence section (121-2) has a length greater than the length of the reflection section (121-3).

11. Nozzle (12) according to one of the preceding claims, the nozzle (12) further comprising: A heat conducting element (125a, 125b) made of a flexible material which can be attached to the cooling surface (123) of the base body (120).

12. Nozzle (12) according to one of the preceding claims, wherein the base body (120) further comprises at least two cooling channels (126) which are preferably arranged at uniform intervals along the circumference of the base body (120) around the nozzle longitudinal axis (12x); wherein each of the cooling channels (126) extends from the cooling surface (123) of the stage through the engagement section (120-2) and opens at the bearing section (120-3).

13. Laser processing system (62) for processing a workpiece (68) using a laser beam (B), the laser processing system (62) comprising: At least one laser beam source (64) for generating a processing laser beam (B); At least one laser processing head (10) with a laser processing optic, a nozzle holder (20) and a nozzle (12) according to one of the preceding claims; The laser processing beam (B) can be focused by means of the laser processing optics and directed through the nozzle holder (20) and the nozzle (12) onto the workpiece (68) to be processed.

14. Laser processing system (62) according to claim 12, wherein the nozzle holder (20) comprises a cooling device.

15. Method for laser processing of a workpiece (68) using a laser processing system (62) which has a nozzle (12) according to one of claims 1 to 12, wherein a laser beam (B) is directed through the base body (120) of the nozzle onto a workpiece (68) to be processed; and Where a focus of the laser beam (B) lies within the base body (120) and above the reflection section (121-3), so that parts of the diverging The laser beam (B) is reflected within the reflection section (121-3) at the inner wall of the base body (120).

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