EP1976658A1

EP1976658A1 - Laser machining nozzle

Info

Publication number: EP1976658A1
Application number: EP06818852A
Authority: EP
Inventors: Nicolai Speker; Florian Sepp
Original assignee: Trumpf Werkzeugmaschinen SE and Co KG
Current assignee: Trumpf Werkzeugmaschinen SE and Co KG
Priority date: 2005-11-25
Filing date: 2006-11-27
Publication date: 2008-10-08
Also published as: WO2007059787A1; ATE494981T1; US20080237207A1; JP2009517216A; DE502005010866D1; JP5039050B2; EP1957232A1; US8188403B2; WO2007060008A1; EP1957232B1; CN101321601A; CN101321601B

Abstract

A laser machining nozzle having at least one supply chamber for the laser beam and for a processing gas has a cavity arranged in the region of the orifice of the gas supply chamber, which cavity is open in the direction towards the workpiece to be machined, this opening having a wedge-shaped edge.

Description

DESCRIPTION

laser machining

The invention relates to a laser processing nozzle for use with a Abstandungsgegeiung.

Such a laser processing nozzle has become known, for example, from DE19906442.

Known laser processing nozzles are made entirely of an electrically conductive material, since the position of the laser processing head is measured by means of a capacitive Abstandgegeiung on the distance of the laser machining nozzle to the workpiece. The laser processing nozzle is opposite to the rest of the

Laser processing machine (and thus also the workpiece, usually sheet metal) electrically insulating (dielectric) attached. With the aid of a distance control sensor, the capacity of the "nozzle-plate" system is permanently measured, and the reduction in capacity is concluded by a reduction in the distance

Capacity change and the resulting change in distance are shown in Figure 5b. This principle of distance control can be used reliably for distances of the laser machining nozzle to the workpiece from 0.3 mm to 35 mm. In the distance range <0.4 mm, which may be relevant for high-performance machining, the known distance control works with the known laser processing nozzle due to the greater susceptibility not satisfactorily enough together. The sensor of the distance control determines measured values, which are evaluated by the distance control as a collision of the laser machining nozzle with the workpiece. In addition, the distance control operates towards smaller distances in a characteristic range with a larger slope. This means that the distance is controlled much more sensitively at low values, as z. B. at 1.0 mm is the case. If it comes now to a small disturbance of the electromagnetic field, z. B. by gas plasma, this entails an immediate change of the distance with it. These readjustments are in the optimized working range of the distance control (0.8 mm - 6 mm) without consequences for the cutting process. For special processes at a small distance, such. For example, with the aid of a high-performance machining nozzle ("QCN"), these deflections cause the melt output to be degraded and, in the worst case, a cut-off or collision message to occur, which is why a low susceptibility to interference is imperative, especially in this distance range. It is the task to be solved, a laser processing nozzle in such a way that a high-performance machining at a small distance from the workpiece is controlled possible.

This object is achieved by a laser processing nozzle of the aforementioned type, wherein the laser processing nozzle has a first component used for the distance control and a second component at least partially enveloping the first component, the distance control defined influencing component, wherein the second component via the first component in the longitudinal direction Laser processing nozzle protrudes.

It is proposed to form at least two or even three components of the laser processing nozzle with the introduction of a material in a component which only slightly influences the distance control and to return a core nozzle as a further component relative to this component. This ensures that the measured values depend on a greater distance from the workpiece than the distance that the entire laser processing nozzle actually has to the workpiece. If the distance control is based, for example, on the change in capacitance between the laser machining nozzle and the workpiece and the second component is made of a dielectric material, the capacitance of the resonant circuit laser processing nozzle is reduced according to the invention. Workpiece by increasing the distance from a comparable capacity of a one-piece metal laser machining nozzle. This has the consequence that disturbances are not evaluated as sensitive and thus the laser machining nozzle is guided more constant over the workpiece (sheet).

The backward displacement of the one component (core nozzle) relative to the other component (enveloping gas cap) causes the first component (core nozzle) to be arranged in a distance range in which the known control based on the capacitance measurement can work reliably. In this distance range capacity changes can be well processed and used for control. The susceptibility is low.

Since the sensor of the distance control is hardly influenced by the dielectric material, real nozzle spacings of <0.3 mm can be achieved without problems.

Furthermore, the laser processing nozzle according to the invention is significantly less susceptible to interference than the known arrangement due to the mechanical and electrical insulation. The fault is further away from the capacitive surface. By means of the laser processing nozzle according to the invention, the sensitivity of the distance control is reduced, and very small distances between the laser processing nozzle and the workpiece can be realized.

In summary, the invention consists in that the laser processing nozzle has two components (inner part, in particular made of copper, outer part made of a dielectric), the distance control taking place between the inner part and the workpiece. The outer part is located at a small distance from the workpiece (<0.4 mm) during laser processing, so that the positive flow characteristics of the laser processing nozzle are still maintained, while the distance control can operate in a region of lower sensitivity. These flow characteristics are understood to mean the following: The laser processing nozzle may have a cavity arranged in the area of the mouth of the gas supply space of the laser processing nozzle, ie in the area between the dielectric cap and the set back copper nozzle, which is open only in the direction of the workpiece to be machined Opening has a wedge-shaped edge. The effect of this design of the laser processing nozzle according to the invention aims to obtain a greater degree of coverage of the cutting front, without the mouth diameter of the laser processing nozzle must be increased. This avoids that in effect a diffuser arises, which has a lower impulse on the melt. The wedge-shaped edge leads to the formation of a roller flow. The roll flow causes the main gas jet first flows into a volume (storage volume), the pressure of which is increased in relation to the environment. The processing gas thereby achieved in comparison to known laser processing nozzles a higher outflow velocity from the mouth, whereby an improved momentum transfer to the plate or on the cutting front is possible. By the rectified velocities in the transition area between the roll flow and the main gas jet, the friction losses between the main gas jet and the environment are reduced in comparison to known laser processing nozzles. The roll flow also has a supporting effect for the main gas jet in the area above the workpiece. Another support effect is created inside the kerf. The main gas jet dissolves in comparison to known laser processing nozzles only further down from the cutting front. This leads to an improved cutting edge.

In a preferred embodiment of the invention, the cavity is arranged rotationally symmetrical to the mouth of the gas supply space.

By this arrangement, a sheath of the results Processing gas jet with a storage volume of processing gas. This produces a rotationally symmetrical overlap of the cutting front.

When the mouth of the gas supply space is retreated behind the nozzle tip of the laser processing nozzle, the processing gas can be very well stowed and flow into the cavity.

Embodiments of the invention are shown schematically in the drawing and are explained below with reference to the figures of the drawing. It shows in detail:

Figure 1 shows the structure of a laser cutting machine;

FIG. 2 shows a first longitudinal section of a first laser processing nozzle according to the invention;

FIGS. 3a, 3b further laser processing nozzles according to the invention;

FIGS. 4a, 4b show further laser processing nozzles according to the invention; Figures 5a, 5b, the principle of the distance control between the laser processing nozzle according to the invention and the workpiece.

FIG. 1 shows the construction of a laser processing system 1 for laser cutting with a CO ₂ laser 2, a laser processing head 4 (laser processing nozzle 4 a) and a workpiece support 5. A generated laser beam 6 is guided by means of deflection mirrors to the laser processing head 4 and directed by means of mirrors on a workpiece 8.

Before a continuous kerf is formed, the laser beam 6 must penetrate the workpiece 8. The sheet 8 must be spot-molten or oxidized at one point, and the melt must be blown out.

Both piercing and laser cutting are assisted by the addition of a gas. As cutting gases 9 oxygen, nitrogen, compressed air and / or application-specific gases can be used. Which gas is ultimately used depends on which materials are cut and what quality requirements are placed on the workpiece. Resulting particles and gases can be sucked by means of a suction device 10 from a suction chamber 11.

According to FIG. 2, the laser processing nozzle 4a according to the invention is constructed from two components 12 and 13 which are connected to one another. The laser processing nozzle 4a designed as a hole nozzle has a central feed space 14 for the cutting gas and the laser beam.

A cylindrical mouth 15 of the hole nozzle 4 a is withdrawn behind a nozzle tip 16 as seen in the flow direction. Rotationally symmetrical to the mouth 15, an annular cavity 17 is provided for receiving cutting gas. The cavity 17 is only to the bottom of the laser processing nozzle 4a, i. towards the workpiece and the mouth 15 out, open and has a circular bottom 18. The storage volume available for the cutting gas thus spreads radially and also beyond the nozzle orifice 15. Arrows (main gas jet 19 and jammed gas jet 19 ') indicate in FIG. 2 the flow of the cutting gas. At the nozzle tip 16, the laser processing nozzle 4a has a diameter much larger than the mouth 15 itself.

The additional storage space provided by means of the cavity 17 is therefore mounted and shaped so that parts of the radially outflowing Gas are recycled via a "roll flow" and encase the cutting gas jet. The closer the nozzle tip 16 is arranged to the sheet to be processed, the higher the flow resistance and the more effective the dynamic pressure profile can be radially expanded. For the formation of the roll flow is primarily the wedge-shaped tapered edge 18 'at the bottom of the laser processing nozzle 4a responsible. Radial outflowing processing gas is partially deflected from here into the cavity 17 and flows along the inner surfaces 17 'and 17 "of the cavity 17 via the outlet edge 18" back to the main gas jet 19. On the one hand, the wedge-shaped geometry causes the flow separation of the radially outflowing processing gas and, on the other hand, acts as a flow-guiding geometry for the formation of the roll flow. In addition to the edge 18 ', the shape of the cavity 17 and the extent of the cavity 17 to behind the nozzle orifice 15 for the formation of the roll flow are relevant.

In order for the roll flow to occur, moreover, the cutting distance, that is the distance between the nozzle lower edge of the nozzle tip 16 and the sheet surface, must be relatively small (<0.7 mm, the best cutting distance being 0.3 to 0.5 mm) become. If the cutting distance is greater, a pressure cushion is created on the sheet surface, which prevents effective momentum transfer of the processing gas. In addition, it no longer comes to the formation of the roll flow.

This results in a higher degree of coverage of the cutting front, which is positive

- quality (melt cut instead of plasma cut in the thick sheet metal area, uniform groove structure);

- feed (+ 10 to + 20%, in some cases +80 to + 100%); - plasma wave (melt cut in the thick sheet metal area);

- Gas consumption

effect.

With the same orifice diameter, the cutting gas consumption is below the current standard values. Preliminary studies indicate that it can also be cut with smaller orifice diameters so that cutting gas consumption can be further reduced.

For a satisfactory function of the laser processing nozzle 4a, the inside of the cavity 17, which adjoins the nozzle opening, may be inclined outwardly. Depending on the angle of inclination, ie the angle between the inner side 17 'and the workpiece, the deflection of the radially outflowing gas takes place so lossless, the greater the inclination, ie the more acute the angle of inclination. For the best possible shaping of the roll flow, it is necessary to withdraw the storage volume behind the plane of the mouth region. The geometry in the region of the bottom 18 and the subsequent flanks 18 'can be circular or elliptical.

FIGS. 3a and 3b show alternatives to the hole nozzle 4a according to FIG. 1. As shown in FIG. 3a, a laser machining nozzle 20 has a conical mouth 21 (Laval nozzle). As shown in FIG. 3b, a laser processing nozzle 22 has an annular gap 23. These alternative embodiments are combined with a storage volume that is unchanged with respect to the laser processing nozzle 4a according to FIG. The operation according to the invention therefore remains.

FIGS. 4a and 4b show alternatives to the storage volume of the laser processing nozzle 4a according to FIG. 1. As shown in FIGS. 4a and 4b, angular shapes of the cavity in the laser processing nozzles 24 (cavity 25) and 26 (cavity 27) are conceivable in addition to round geometries. FIG. 5a illustrates the use of the laser processing nozzle according to the invention according to FIG. 2 in combination with a distance control, as is known, for example, from DE19906442. The use of the laser processing nozzle according to FIG. 2 described below can be transferred analogously to the laser processing nozzles according to FIGS. 3 a to 4 b. The laser processing nozzle 4a comprises the component 12 as an inner part made of an electrically conductive material (metal) and the component 13 as an outer part made of a dielectric material (plastic or ceramic). The distance control is based on the evaluation of the capacitance between the workpiece 8 and the component 12 of the laser processing nozzle 4a. A sensor of the distance control permanently measures the capacitance between the component 12 and the workpiece 8. This results in a depiction of the change in the distance D between the component 12 and the workpiece 8 by means of the measured capacitance C. As shown schematically in FIG. 5 b, For example, the increase in the capacitance C (x-axis) can be used as a measure of the increase in the distance D (y-axis). At a great distance of the laser processing nozzle 4a, a smaller capacity C is measured than at a small distance. Due to the production of the component 13 from a dielectric material, the laser processing nozzle 4a according to the invention can be used in a distance range (distance E <0.3 mm), which is indicated by dashed lines in FIG. 5b. In This distance range uses high-power laser cutting nozzles. To work with this small distance range, ie to cut on the one hand with high precision and on the other hand to use a reproducible distance control is possible because the actual required for capacitance measurement component 12 has a greater distance D to the workpiece 8, which allows a reliable capacitance measurement. The further of this component 12 enclosing the

High-power laser processing required component 13 has a smaller distance E to the workpiece 8, which allows a high-power laser processing. Consequently, the laser processing nozzle 4a according to the invention can be used in a small distance range to the workpiece 8. The flow conditions described above can be adjusted while the distance control is optimized at the same time. Trained as Hüllgaskappe component 13 acts mechanically and electrically insulating.

Due to the dielectric property of the component 13, this component 13 is indeed taken into account in the distance measurement. Due to the material, the contribution is low, constant and predictable. The actual nozzle (component 12) made of copper is set back relative to the component 13 by about 1 mm. At a measured distance of 1 mm, the component 13 completely closes off with the workpiece. There will be a gas injection of almost 100% reached. At a selected distance of 1.3 mm, a distance of 0.3 mm is effectively effected. In this case, the distance control can work in the optimum range. Sporadically occurring plasma igniters hardly affect the distance control.

Claims

P AT EN TA NSPR O CHE

A laser processing nozzle (4a; 20; 22; 24; 26) for use with a capacitive pitch control between the laser processing nozzle and the workpiece (8), characterized in that the laser processing nozzle (4a; 20; 22; 24; 26) is a first for the distance control used component (12) and a second the first component (12) at least partially enveloping, the distance control defined influencing component (13), wherein the second component (13) via the first

Component (12) in the longitudinal direction of the laser processing nozzle (4a; 20; 22; 24; 26) protrudes.

2. Laser processing nozzle according to claim 1, characterized in that the second component (13) is designed as a cap.

3. Laser processing nozzle according to claim 1 or 2, characterized in that the first component (12) made of an electrically conductive material and the second component (13) is made of a dielectric material.

4. Laser processing nozzle according to one of the preceding claims, characterized in that the first component (12) is made of metal.

5. Laser processing nozzle one of the preceding claims, characterized in that the second component (13) is made of plastic.

6. Laser processing nozzle according to one of the preceding claims, characterized in that the second component (13)

Ceramics is.

7. Laser processing nozzle according to one of the preceding claims, characterized in that the second component (13) is made of a high temperature resistant material.

8. Laser processing nozzle according to one of the preceding claims, characterized in that the second component (13) is made of a UV / infrared-resistant material.

9. Laser processing nozzle according to one of the preceding claims, characterized in that the Laser processing nozzle has a in the region of the mouth of the gas supply space of the laser processing nozzle, ie in the region between the dielectric member and set back component, arranged cavity, which is open only in the direction of the workpiece to be machined, wherein the opening has a wedge-shaped edge.