Machining head and method for the laser-beam cutting of components

Abstract

In the machining head, a cutting gas, as first gas stream, and a laser beam are directed at a component to be cut through a nozzle arranged in the direction of the component. The cutting-gas feed is, at least in the region of the nozzle of the cutting-gas feed, enclosed by an annular or polygonal split nozzle or by an annular or polygonal arrangement of individual nozzles that are arranged separately from one another, and is arranged such that this nozzle d is arranged in the centre of the circle or at the centroid of the area. A second gas stream is directed through the annular or polygonal split nozzle or the nozzles of the annular or polygonal arrangement in the direction of a surface of the component to be cut. The pressure of the cutting gas and the pressure of the second gas stream can each be adjusted independently of one another and a pressure of the cutting gas at the outlet opening of the nozzle for the cutting gas is greater than the pressure of the second gas stream but at most three times as great.

Description

[0001] Processing head and method for laser beam cutting of components

[0002] The invention relates to a processing head designed for laser beam cutting of components and a method for laser beam cutting. These components can preferably be metallic.

[0003] When cutting with laser radiation, a coaxially arranged gas jet is used as the cutting gas to expel the material melted by the laser beam from the cutting gap. Especially when laser cutting metals, almost vertical grooves are formed on the cutting edge. These largely determine the roughness of the cutting edges and form typical horizontal zones with characteristic properties regarding wavelength and roughness. Furthermore, the grooves are spatially related to the burr formation on the lower edge of the cut material and are therefore a quality-determining feature of the cutting result.

[0004] To shape the gas jet, nozzles arranged coaxially with the laser beam are usually used; their diameter is generally significantly larger than the resulting cutting gap. In addition to simple nozzles, such as those tapering conically downwards, there are also nozzle designs with internal division of the gas flow into separate flow channels within the nozzle, which are then rejoined in or below the respective nozzle and on the workpiece. It is also common to have specially designed nozzle interiors and undersides to influence the flow characteristics of the cutting gas.

[0005] To reduce gas loss on the top side of a component to be cut and to improve gas utilization, an attachment nozzle concept has been used in which a movable outer ring of the nozzle is guided directly over the workpiece surface.

[0006] However, none of the nozzle concepts has yet succeeded in significantly influencing the structure formation on the surfaces of the cutting edges or even completely preventing the formation of scoring.

[0007] JP 2011 - 224 600 A shows how holes can be created in workpieces using a laser beam.

[0008] WO 2018 / 008400 Al concerns laser processing, in particular of plastic parts reinforced with carbon fibres.

[0009] A laser welding process and a corresponding device are described in EP 1 153 696 A2.

[0010] JP H06 - 304 777 A shows possibilities for hermetically sealing batteries.

[0011] It is therefore an object of the invention to provide possibilities with which an improved surface quality can be achieved on cutting edges obtained by laser beam cutting, if possible without additional post-processing.

[0012] According to the invention, this object is achieved with a processing head having the features of claim 1. Claim 940 relates to a method for laser beam cutting. Advantageous embodiments and further developments of the invention can be realized with features defined in the dependent claims.

[0013] In the machining head according to the invention, a cutting gas supply is provided along its central longitudinal axis, through which a cutting gas as the first gas stream and a laser beam are directed through a nozzle arranged in the direction of the component onto a component to be cut to form a cutting gap. The cutting gas supply is enclosed, at least in the region of the nozzle of the cutting gas supply, by an annular or polygonal gap nozzle or by an annular or polygonal arrangement of individual, separately arranged nozzles and is arranged such that the nozzle of the cutting gas supply is located at the center of the circle defined by the annular gap nozzle or the nozzles of the annular arrangement or the center of gravity of the polygonal gap nozzle or the polygonal arrangement of nozzles.A second gas stream is directed through the annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement toward the respective surface of the component to be cut. The pressure of the cutting gas supplied through the nozzle of the cutting gas supply and the pressure of the second gas stream flowing through the annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement are each independently adjustable. Furthermore, the pressure of the cutting gas supplied through the nozzle of the cutting gas supply at the outlet opening of this nozzle is greater than the pressure of the second gas stream at the outlet opening(s) of the annular or polygonal gap nozzle or the outlet openings of the nozzles of the annular or polygonal arrangement.The pressure in the nozzle of the cutting gas supply is a maximum of three times the pressure of the second gas stream at the outlet(s) of the annular or polygonal gap nozzle or the outlet(s) of the nozzles of the annular or polygonal arrangement. This essentially refers to the pressures in the area of ​​the outlet(s) of the cutting gas nozzle and the annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement. Advantageously, the pressure of the cutting gas supplied through the nozzle at the outlet of the cutting gas nozzle should be set to be at least 1.5 times and at most twice, in particular at least 1.7 and at most 1.9 times, the pressure of the second gas stream at the outlet(s) of the annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement.

[0014] The nozzle opening through which the cutting gas exits the nozzle should preferably have an inner diameter that corresponds to the outer diameter of the laser beam used for cutting, this can further prevent the formation of scoring on the cutting edge.

[0015] Nozzles arranged in an annular or polygonal arrangement should be geometrically designed, dimensioned and spaced apart from one another in such a way that a second gas flow can be formed emerging from their outlet openings, which encloses the cutting gas flow in an annular or polygonal shape and the second gas flow is formed at least almost as a closed ring in which at least almost equal flow velocities and pressures are maintained over its circumference.

[0016] For a polygonal shape, geometries with at least four corners are preferable.

[0017] The nozzles of an annular or polygonal arrangement can be rotationally symmetrical and / or slit-shaped, at least in the region of their outlet openings with their free cross-sectional areas through which gas for the second gas stream flows. Slits can also be shaped in the form of partial circles, concave in the direction of the nozzle for the cutting gas. The same design and dimensions of free cross-sections can be selected for the nozzles of the respective annular or polygonal arrangement, but also, for example, alternating, differently designed and dimensioned free cross-sectional areas can be selected for nozzles of an annular or polygonal arrangement. The pressure in the region of the outlet openings of the nozzles of the second gas stream should be maintained in the range between 0.05 MPa and 2.5 MPa relative to the ambient pressure, whereby flow velocities of the gases exiting the outlet nozzles of more than 300 m / s can be achieved.For laser beam cutting with oxygen, pressures in the range 0.05 MPa to 0.1 MPa can be used.

[0018] Advantageously, the nozzle of the cutting gas supply, the annular or polygonal gap nozzle, and / or the nozzles of the annular or polygonal arrangement should be designed to converge in the direction of their outlet(s), so that the smallest free cross-section through the cutting gas or the second gas stream is / are arranged at the outlet of the nozzle for the cutting gas supply or the annular or polygonal gap nozzle or the outlet openings of the nozzles of the annular or polygonal arrangement. For this purpose, in particular and preferably, the respective inner lateral surfaces on the outward-facing surface of the respective nozzle can be designed to taper continuously conically in the direction of the central longitudinal axis of the cutting gas supply, i.e., towards the center of the outlet opening of the nozzle on the cutting gas supply, over a length beginning at least 15 mm before the respective outlet opening is reached.At least 40% of the circumferential surface of the respective inner surface should be tapered.

[0019] The cone angle can be larger on the inner wall of the annular or polygonal slotted nozzle, or on the nozzles of the annular or polygonal arrangement, than on the cutting gas supply nozzle. This ensures that the pressure of the individual gas streams is maintained up to the outlet openings and prevents a reduction in the energy content of the cutting gases that can be converted into work within the machining head.

[0020] The continuously tapered design allows for the pressure and flow velocity distribution within each nozzle to be influenced and prevents the cutting gas from accelerating to supersonic speeds within the nozzle. The laser beam should be directed coaxially through the cutting gas supply nozzle onto the component and preferably have a beam cross-sectional area that fills at least 80% and no more than 100% of the free cross-section of the cutting gas supply nozzle in the area of ​​its outlet opening. This allows for gap widths in the formed cutting gap during laser beam cutting that correspond to the inner diameter of the cutting gas nozzle outlet opening.

[0021] The smallest inner diameter of the cutting gas supply nozzle at the outlet opening should correspond to the gap width of the cutting gap to be created, with a maximum deviation of ± 20%, and should be in the range between 0.5 mm and 2 mm. This smallest inner diameter should preferably correspond exactly to the gap width of the cutting gap to be created.

[0022] Advantageously, the width of the gap of the annular or polygonal gap nozzle or the width or the outer diameter of the nozzles of the annular arrangement can correspond at least to the width of the inner diameter of the nozzle of the cutting gas supply in the region of its outlet opening and preferably be twice this inner diameter.

[0023] The outer diameter in the area of ​​the outlet opening can be at least twice as large as the diameter of the nozzle of the cutting gas supply at its outlet opening and can be a maximum of 10.00 mm.

[0024] For a polygonal gap nozzle or a polygonal arrangement of nozzles, a maximum distance parallel to the cutting gap to be formed between the respective oppositely arranged outlet opening(s) should be maintained that is smaller than the maximum distance between the outlet opening(s) arranged in an axial direction oriented perpendicular to it. For example, for a rectangular gap nozzle or arrangement of nozzles, a rectangle length of approximately 10 mm can be selected, with these longer edges then pointing parallel to the cutting gap or feed movement direction. The length of the edges oriented perpendicular to this can then be 2 mm to 5 mm. A square shape is advantageous compared to a triangle or geometries with more than four corners.A rectangle can be selected whose longer edges are preferably aligned at least approximately parallel to the cutting gap to be created, rather than the width of the edges aligned perpendicular to it. A length-to-width ratio of at least 5 to 1 is particularly advantageous.

[0025] The distance between the outlet openings of the nozzle of the cutting gas supply and the annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement to the surface of the component to be cut should differ by a maximum of 1 mm and a distance of the outlet nozzles to the component surface on which the cutting gap is to be formed with the laser beam in the range between 0.2 mm and 2 mm must be maintained during laser beam cutting.

[0026] The invention can therefore be a nozzle arrangement with an inner nozzle opening and an annular gap nozzle concentrically surrounding it, or concentrically arranged nozzles in an annular arrangement, wherein the centrally arranged outlet opening through which cutting gas exits and the annular gap nozzle or the nozzles of the annular arrangement each have a separate gas supply with independently adjustable or controllable gas pressure. The respective gas pressure can be influenced by means of valves arranged in the respective gas supply. In a polygonal gap nozzle or a polygonal arrangement of nozzles, the nozzle from which the cutting gas exits should be arranged at the respective centroid of the polygon.

[0027] The outer diameter of the outlet opening through which the cutting gas exits the machining head should approximately correspond to the cutting gap width; preferably, it should be the same size as the gap width of the kerf. The diameter of the annular gap nozzle or the diameter of the ring in which the nozzles of an annular arrangement are arranged can be a multiple of the cutting gap width. The outlet opening for the cutting gas can preferably be positioned at the same height as the annular or polygonal gap nozzle or the nozzles in an annular or polygonal arrangement above the surface of the component to be cut, or slightly above or below it.

[0028] The outlet opening distance from the component surface used during cutting can be smaller than the diameter of the outlet opening from which the cutting gas exits the processing head.

[0029] The gas pressures or the pressure ratio should preferably be set so that a pressure ratio of the absolute pressures between the inner arranged outlet opening for the cutting gas and the outlet opening(s) of the annular or polygonal gap nozzle or the outlet openings of the nozzles of the annular or polygonal arrangement pi / p a of less than 2.

[0030] The gas supply for the internally arranged cutting gas nozzle can be connected via the standard cutting gas supply in the machining head. The gas supply to the annular or polygonal slotted nozzle, or the nozzles of the annular or polygonal arrangement, can be connected via additional connections to the machining head.

[0031] Particularly advantageously, with an absolute pressure at the outlet opening of the nozzle for the cutting gas of 2.0 MPa, the absolute pressure of the second gas stream at the outlet opening of the annular or polygonal gap nozzle or the outlet openings of the nozzles of the annular or polygonal arrangement can be set at 1.1 MPa.

[0032] The nozzle for the cutting gas can be designed in its interior, at least in the region near its outlet opening, in the form of a convergent nozzle in which the smallest diameter is arranged at the outlet opening.

[0033] The smallest diameter of the nozzle of the cutting gas supply at the outlet opening should correspond almost to the gap width of the cutting gap to be formed and a maximum deviation of the smallest diameter in relation to the gap width of ± 20%, preferably ± 10%, should be maintained.

[0034] A laser beam with a beam cross-sectional area of ​​at least 80% and a maximum of 100% of the free cross-section of the cutting gas supply nozzle in the area of ​​its outlet opening creates a cutting gap with a width approximately the size of the cutting gas outlet opening. This results in a direct and straight inflow of the cutting gas stream into the forming cutting gap. Compared to the prior art, the upper edge of the cutting gap then does not act as a flow obstruction in the form of a forward-directed step, and an unhindered inflow of the cutting gas stream into the cutting gap can occur. The invention can thus prevent the detachment of the inflowing cutting gas from the upper edge of the cutting gap and the formation of a recirculation region at the upper edge of the gap during laser beam cutting.Compared to the state of the art, the amplification of spatial and temporal disturbances in the boundary layer of the cutting gas flow on the cutting edge is prevented or greatly reduced, and the cutting gas flow can achieve a uniform expulsion of the melt formed with the energy of the laser beam from the kerf.

[0035] The outer annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement can prevent the cutting gas from becoming contaminated by ambient gas and shield the melt that is formed. This can prevent oxidation in the process zone during fusion cutting with an inert process gas, preferably nitrogen and an annular gap flow or a second annular or polygonal gas flow with a process gas that is also inert. If, on the other hand, oxygen is used as the cutting gas in laser cutting, with which energy is provided to the process through oxidation to melt the material and the melt is to be expelled from the kerf, oxygen or an inert process gas such as, for example,Nitrogen flows towards the component surface, which can influence the oxygen content in the cutting gas that reaches the melt.

[0036] With the outer annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement, the effective area of ​​the cutting gas for melt expulsion in the gap and thus the cuttable material thickness can be increased.

[0037] By considering the pressure ratio at the cutting gas outlets, the annular or polygonal gap nozzle, or the nozzles of the annular or polygonal arrangement of less than a maximum of 2, the pressure distribution between the nozzle outlets and the component surface can be adjusted in such a way that the cutting gas flowing out of the outlet can be prevented from reaching the speed of sound. This prevents shocks from forming in the exiting cutting gas flow and the flow within the cutting gap, thereby increasing the gas energy that can be converted into work compared to the state of the art and suppressing disturbances to the gas boundary layer in the process zone caused by shock-boundary layer interactions.At pressure ratios between 2 and 3 of the absolute pressure at the outlet openings of the cutting gas nozzle and the slotted nozzle, or the nozzles in a ring-shaped or polygonal arrangement, the cutting gas flow reaches the speed of sound. Compared to the state of the art, the speed is lower, the pressure higher, and the resulting shocks weaker, which also increases the energy of the gas that can be converted into work compared to the state of the art and prevents losses due to strong shocks. However, if the pressure ratio is less than 2, i.e., the absolute pressure at the outlet opening of the cutting gas nozzle is less than twice the absolute pressure at the outlet openings of the slotted nozzles or the outlet openings of the nozzles arranged in a ring-shaped or polygonal arrangement, the cutting gas flow does not reach the speed of sound.

Claims

Claims Processing head for laser beam cutting of components, in which along its central longitudinal axis a cutting gas supply, through which a cutting gas as a first gas stream and a laser beam through a nozzle arranged in the direction of the component are directed onto a component to be cut to form a cutting gap, and the cutting gas supply is enclosed and arranged at least in the region of the nozzle of the cutting gas supply by an annular or polygonal gap nozzle or by an annular or polygonal arrangement of individual nozzles arranged separately from one another, such that the nozzle of the cutting gas supply is arranged in the center of the circle or in the center of gravity of the polygonal gap nozzle or the polygonal arrangement of nozzles,and a second gas stream is directed through the annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement in the direction of a surface of the component to be cut, and the pressure of the cutting gas supplied through the nozzle of the cutting gas supply and the pressure of the second gas stream,which flows through the annular or polygonal gap nozzle or the nozzles of the annular or polygonal arrangement, each independently adjustable, and a pressure of the cutting gas supplied through the nozzle of the cutting gas supply at the outlet opening of the nozzle for the cutting gas is greater than the pressure of the second gas stream at the outlet opening of the annular or polygonal gap nozzle or the outlet openings of the nozzles of the annular or polygonal arrangement and is a maximum of three times as large, whereby in the case of a polygonal gap nozzle or a polygonal arrangement of nozzles, a maximum distance parallel to the cutting gap to be formed of the respective oppositely arranged outlet openingsf) is maintained, which is smaller than the maximum distance of the, Outlet opening(s) arranged in an axial direction perpendicular to the latter or the distance between the outlet openings of the nozzle of the cutting gas supply and the annular or polygonal slit nozzle or the nozzles of the annular or polygonal arrangement to the surface of the component to be cut deviates by a maximum of 1 mm and a distance in the range between 0.2 mm and 2 mm is maintained during laser cutting.Machining head according to claim 1, characterized in that the nozzle of the cutting gas supply, the annular or polygonal slit nozzle, and / or the nozzles of the annular or polygonal arrangement are / are convergent in the direction of their outlet opening(s), so that the smallest free cross-section through the cutting gas or the second gas stream is / are arranged at the outlet opening of the nozzle for the cutting gas supply or the annular or polygonal slit nozzle or the outlet openings of the nozzles of the annular or polygonal arrangement. Machining head according to one of the preceding claims, characterized in that the laser beam is directed coaxially through the nozzle of the cutting gas supply onto the component and preferably has a beam cross-sectional area that fills at least 80% and at most 100% of the free cross-section of the nozzle of the cutting gas supply in the region of its outlet opening.Machining head according to one of the preceding claims, characterized in that the smallest internal diameter of the nozzle of the cutting gas supply at the outlet opening corresponds to the gap width of the respective cutting gap to be formed with a maximum deviation of ± 20%, preferably exactly to the gap width of the respective cutting gap to be formed and lies in the range between 0.5 mm and 2 mm. Machining head according to one of the preceding claims, characterized in that the width of the gap of the annular. or polygonal gap nozzle or the width or the outer diameter of the nozzles of the annular or polygonal arrangement corresponds at least to the width of the inner diameter of the nozzle of the cutting gas supply in the region of its outlet opening and is at most twice this inner diameter. Machining head according to one of the preceding claims, characterized in that the outer diameter of the annular gap nozzle or the diameter of the annular arrangement of nozzles in the region of the outlet opening(s) is at least twice as large as the diameter of the nozzle of the cutting gas supply at its outlet opening and is at most 10.00 mm.Machining head according to one of the preceding claims, characterized in that the inner lateral surfaces on the outwardly facing surface of the nozzle of the cutting gas supply, the annular or polygonal gap nozzle and / or nozzles of the annular or polygonal arrangement are / are tapered conically in the direction of the central longitudinal axis of the cutting gas supply, i.e. towards the center of the outlet opening of the nozzle on the cutting gas supply over a length beginning at least 15 mm before the respective outlet opening is reached.Processing head according to one of the preceding claims, characterized in that the pressure of the cutting gas supplied through the nozzle of the cutting gas supply at the outlet opening of the nozzle for the cutting gas is at most twice as great as the pressure of the second gas stream at the outlet opening of the annular or polygonal gap nozzle or the outlet openings of the nozzles of the annular or polygonal arrangement. Method for laser beam cutting of components with a processing head for cutting gas supply, by means of which a cutting gas as a first gas stream and a laser beam are directed via a nozzle in the direction of a component to be cut, so that a cutting gap is formed in the respective component, and via an annular or. polygonal slit nozzle or nozzles arranged in an annular or polygonal arrangement, in which the polygonal slit nozzle or a polygonal arrangement of nozzles maintains a maximum distance parallel to the cutting gap to be formed of the respective oppositely arranged outlet opening(s), which is smaller than the maximum distance of the outlet opening(s) arranged in an axial direction perpendicular thereto, or the distance between the outlet openings of the nozzle of the cutting gas supply and the annular or polygonal slit nozzle or the nozzles of the annular or polygonal arrangement to the surface of the component to be cut deviates by a maximum of 1 mm and a distance in the range between 0.2 mm and 2 mm is maintained during laser cutting, a second gas stream is directed onto a surface of the component to be cut,wherein the pressure of the cutting gas supplied through the first nozzle and the pressure of the second gas stream supplied via the annular or polygonal gap nozzle or nozzles arranged in an annular or polygonal arrangement are adjusted independently of one another, and the pressure of the cutting gas supplied through the nozzle at the outlet opening of the cutting gas nozzle is a maximum of three times greater than the pressure of the second gas stream at the outlet opening(s) of the annular or polygonal gap nozzle or nozzles arranged in an annular or polygonal arrangement. Method according to the preceding claim, characterized in that the smallest inner diameter of the nozzle of the cutting gas supply at the outlet opening is selected such that it corresponds to the gap width of the respective cutting gap to be formed with a deviation of a maximum of ± 20%.preferably corresponds exactly to the gap width of the respective cutting gap to be formed. Method according to the preceding claim, characterized in that a pressure of the cutting gas supplied through the nozzle is adjusted at the outlet opening of the nozzle for the cutting gas, which is at least 1.5 times as large and at most twice as large, in particular at least 1.7 and at most 1.9 times as large, as the pressure of the second gas stream at the outlet opening(s) of the annular or polygonal slit nozzle or the nozzles of the annular or polygonal arrangement.