LASER CUTTING NOZZLE FOR A LASER MACHINING UNIT AND METHOD FOR OPERATING SUCH A LASER MACHINING UNIT

Abstract

A laser cutting nozzle for a laser machining unit is described, the nozzle including a passage for the laser beam and cutting gas. The passage extends between a nozzle inlet and a nozzle mouth along a passage longitudinal axis. The passage comprises a convergence portion and a divergence portion. In the entire divergence portion, the wall of the passage forms an angle of inclination relative to the passage longitudinal axis of at most 5°. In addition, the length of the divergence portion is less than 5 times the diameter of the constriction.

Claims

1. (canceled)

2. A laser cutting nozzle for a laser machining unit, the laser cutting nozzle comprising: a passage for a laser beam and a cutting gas, the passage extending between a nozzle inlet and a nozzle mouth along a passage longitudinal axis, the passage converging continuously towards the nozzle mouth thereof, in a convergence portion, as far as a constriction of the passage, to less than 40% of a cross-sectional area at an inlet of the convergence portion, the passage diverging continuously in a divergence portion, proceeding from the constriction of the passage, as far as the mouth of the passage, to over 130% of a cross-sectional area at the constriction of the passage; wherein the convergence portion transitions in an edgeless manner into the divergence portion at the constriction; wherein, in the entire divergence portion, the wall of the passage is at an angle of inclination relative to the passage longitudinal axis of at most 5°; wherein the length of the divergence portion is less than 5 times the diameter of the constriction; and wherein the divergence portion has a length that is more than 1.4 times the length of the convergence portion.

3. The laser cutting nozzle of claim 2, wherein the average angle of inclination of the wall of the passage relative to the passage longitudinal axis in the convergence portion is greater than 7° and less than 13°.

4. The laser cutting nozzle of claim 2, wherein the average angle of inclination of the wall of the passage relative to the passage longitudinal axis in the divergence portion is less than 4.0° and greater than 1.0°.

5. The laser cutting nozzle of claim 2, wherein the convergence portion transitions directly into the divergence portion at the constriction.

6. The laser cutting nozzle of claim 2, wherein the passage additionally comprises a cylindrical inflow portion that is arranged upstream of the divergence portion, on the inlet side.

7. The laser cutting nozzle of claim 2, wherein the divergence portion is longer than the convergence portion, wherein the divergence portion has a length that is less than 1.7 times the length of the convergence portion.

8. The laser cutting nozzle of claim 2, wherein the length of the divergence portion is less than 3 times the diameter of the constriction and is more than twice the diameter of the constriction.

9. The laser cutting nozzle of claim 2, wherein the cross-sectional area of the mouth is more than 180% and less than 220% of the cross-sectional area of the constriction.

10. The laser cutting nozzle of claim 2, wherein the convergence portion comprises a wall that is curved towards the passage longitudinal axis, at least in portions, which wall has a radius of curvature of between 4 and 8 mm.

11. The laser cutting nozzle of claim 2, wherein the divergence portion comprises a wall that is curved towards the passage longitudinal axis, at least in portions, which wall has a radius of curvature of between 20 and 30 mm.

12. The laser cutting nozzle of claim 2, wherein the diameter of the mouth is between 1.8 and 3.5 mm, the diameter of the constriction is between 1.3 and 3.0 mm, the length of the convergence portion is between 3.5 and 4.5 mm, the length of the divergence portion is between 5.0 and 7.0 mm, and the outside diameter of the nozzle on the mouth side is between 3.0 and 5 mm.

13. The laser cutting nozzle of claim 2, wherein the nozzle comprises a conical peripheral surface on the mouth side that has a length of between 4.0 and 5.0 mm and is at an angle of inclination relative to the passage longitudinal axis of between 20° and 30°.

14. The laser cutting nozzle of claim 2, wherein the nozzle comprises an end face that extends perpendicularly to the passage longitudinal axis, annularly surrounds the mouth, and has a width between 0.3 and 0.7 mm.

15. A laser machining unit comprising: a machining head; and the laser cutting nozzle of claim 2 secured to the machining head.

16. The laser machining unit of claim 15, further comprising a capacitive distance control of the nozzle-workpiece distance that determines the capacitance between the nozzle and the workpiece for the purpose of the control.

17. The laser machining unit of claim 15, wherein the laser cutting nozzle is configured to perform three-dimensional laser cutting machining.

18. The laser machining unit of claim 15, further comprising a laser source, the laser source comprising at least one of a laser diode, a CO.sub.2 laser, a solid-state laser, and a disc laser, the laser source having a maximum power of at least 2 kW.

19. The laser machining unit of claim 15, wherein a laser source of the unit can generate a laser beam having a beam parameter product of less than or equal to 2 mm mrad.

20. A method of performing three-dimensional cutting machining on a metal profile, the method comprising: feeding a cutting gas to a laser cutting nozzle, the laser cutting nuzzle comprising a passage for a laser beam and a cutting gas, the passage extending between a nozzle inlet and a nozzle mouth along a passage longitudinal axis, the passage converging continuously towards the nozzle mouth thereof, in a convergence portion, as far as a constriction of the passage, to less than 40% of a cross-sectional area at an inlet of the convergence portion, the passage diverging continuously in a divergence portion, proceeding from the constriction of the passage, as far as the mouth of the passage, to over 130% of a cross-sectional area at the constriction of the passage, wherein, in the entire divergence portion, the wall of the passage is at an angle of inclination relative to the passage longitudinal axis of at most 5°, and the length of the divergence portion is less than 5 times the diameter of the constriction, wherein the cutting gas is fed on the inlet side, at a pressure of between 8 and 23 bar; and cutting, at least intermittently, the metal profile at a distance between the nozzle and a workpiece surface that is in a distance range of between 2 and 6 mm; wherein the metal profile has a workpiece thickness of between 1 to 4 mm.

21. A laser cutting nozzle for a laser machining unit, the laser cutting nozzle comprising: a passage for a laser beam and a cutting gas, the passage extending between a nozzle inlet and a nozzle mouth along a passage longitudinal axis, the passage converging continuously towards the nozzle mouth thereof, in a convergence portion, as far as a constriction of the passage, to less than 40% of a cross-sectional area at an inlet of the convergence portion, the passage diverging continuously in a divergence portion, proceeding from the constriction of the passage, as far as the mouth of the passage, to over 130% of a cross-sectional area at the constriction of the passage; wherein the convergence portion transitions in an edgeless manner into the divergence portion at the constriction; wherein, in the entire divergence portion, the wall of the passage is at an angle of inclination relative to the passage longitudinal axis of at most 5°; wherein the length of the divergence portion is less than 5 times the diameter of the constriction and more than twice the diameter of the constriction.

22. A laser cutting nozzle for a laser machining unit, the laser cutting nozzle comprising: a passage for a laser beam and a cutting gas, the passage extending between a nozzle inlet and a nozzle mouth along a passage longitudinal axis, the passage converging continuously towards the nozzle mouth thereof, in a convergence portion, as far as a constriction of the passage, to less than 40% of a cross-sectional area at an inlet of the convergence portion, the passage diverging continuously in a divergence portion, proceeding from the constriction of the passage, as far as the mouth of the passage, to over 130% and less than 250% of a cross-sectional area at the constriction of the passage; wherein the diameter of the mouth is between 1.8 and 3.5 mm; wherein the diameter of the constriction is between 1.3 and 3.0 mm; wherein, in the entire divergence portion, the wall of the passage is at an angle of inclination relative to the passage longitudinal axis of at most 5°; and wherein the length of the divergence portion is less than 5 times the diameter of the constriction.

Description

DESCRIPTION OF DRAWINGS

[0039] FIG. 1 is a central cross-sectional view of a laser cutting nozzle,

[0040] FIG. 2 is a side view of the laser cutting nozzle according to FIG. 1, and

[0041] FIG. 3 shows a laser machining unit that comprises a laser cutting nozzle according to FIG. 1 for three-dimensional workpiece machining.

DETAILED DESCRIPTION

[0042] FIG. 1 is a cross-sectional view of a laser cutting nozzle 1 for a laser machining unit. The nozzle 1 is a single-hole nozzle which is produced integrally from copper. FIG. 1 is a central longitudinal section along the nozzle longitudinal axis 3. The nozzle 1 is substantially formed as a body that is rotationally symmetric with respect to the longitudinal axis 2.

[0043] The nozzle 1 comprises a central passage 2 for a laser beam and cutting gas, which passage extends from a nozzle inlet 4 as far as a nozzle mouth 5, along a passage longitudinal axis 6. The passage longitudinal axis 6 coincides with the nozzle longitudinal axis 3.

[0044] The passage 2 consists of a cylindrical inflow portion 7, a continuously converging convergence portion 8, and a divergence portion 9. The passage 2 has a circular cross section over the entire length L.sub.ges thereof, i.e. over all the portions 7, 8, 9. The convergence portion 8 transitions continuously, in an edgeless manner and gradually, into the divergence portion 9 at a constriction 10.

[0045] In order to form an emergent gas flow that has ratios that are homogenous and are favorable for laser melting cutting over a large distance range of up to 6 mm, in the embodiment shown the passage 2 is formed in the following manner.

[0046] At the inflow portion 7, the passage 2 has a diameter d.sub.E of 4.4 mm. At the constriction, the diameter d.sub.min is 1.6 mm. The mouth d.sub.MI has a diameter of 1.94 mm. Consequently, the cross-sectional area 11 at the constriction 10 is less than 40% of the cross-sectional area 12 at the inlet 13 of the convergence portion 8 (corresponds to the cross-sectional area over the entire inflow portions since said portion is cylindrical). In particular, the constriction cross section 12 is only 13% of the cross-sectional area 12 at the inlet 13 of the convergence portion 8. By the mouth 5, the passage 2 has widened continuously again to over 130%, in particular to 147%, of the cross-sectional area 11 at the constriction. The cross-sectional area 14 of the mouth 5 is only 19% of the cross-sectional area 12 at the inlet 14 of the passage 2.

[0047] In order to prevent the flow from “breaking off” in the edge region, the wall of the passage 2 is at an angle of inclination relative to the passage longitudinal axis 6 of at most 5°, over the entire divergence portion 9. The average angle of inclination α.sub.D of the wall of the passage relative to the passage longitudinal axis 6 in the divergence portion 9 is 1.5°. In contrast, the average angle of inclination α.sub.D of the wall of the passage relative to the passage longitudinal axis 6 in the convergence portion 8 is significantly greater, at 12°.

[0048] The length L.sub.E of the inflow portion 7 is 1.3 mm, the length L.sub.K of the convergence portion 8 is 4.0 mm, and the length L.sub.D of the divergence portion 9 is 6.5 mm. The overall length L.sub.ges of the passage 2 is consequently 11.8 mm. The length L.sub.D of the divergence portion 9 is approximately 1.63 times the length L.sub.K of the convergence portion 8.

[0049] It is also significant that the length L.sub.D of the divergence portion 9 is less than 5 times the diameter d.sub.min of the constriction 10. In particular, the length L.sub.D is 4.1 times the constriction diameter d.sub.min.

[0050] The convergence portion 8 and the divergence portion 9 are not strictly conical. The wall is curved towards the passage longitudinal axis 6 at least in portions (convergence portion 8: radius of curvature of e.g. 6 mm; divergence portion 9: radius of curvature of e.g. 26 mm).

[0051] The outside diameter d.sub.MA of the nozzle 1 on the mouth side is 3.15 mm. The width of the end face 15 extending perpendicularly to the passage longitudinal axis 6, which face annularly surrounds the mouth 5, is 0.605 mm. This makes it possible to achieve a sufficiently high response characteristic for capacitive distance control that also allows for distance control in the range of up to 6 mm. Machining at a greater working distance increases the process reliability, with the result that error-free machining can be carried out at high speeds, at a feed rate in the range of 10-50 m/min.

[0052] Further details of the outer contour of the nozzle 1 will be explained with reference to FIG. 2, which is a side view of the laser cutting nozzle 1.

[0053] A conical peripheral surface 16 having a length L.sub.KON of 4.5 mm and an angle of inclination α.sub.KON relative to the passage longitudinal axis 6 of 28° adjoins the end face 15 on the mouth side. Approximately at the height of the constriction 10, the conical peripheral surface 16 transitions into a cylindrical peripheral surface 17, the largest outside diameter d.sub.max of which is 8.0 mm. The cylindrical peripheral surface 17 is provided with a knurling 18 which functions as a gripping element during handling, e.g. when screwing the nozzle 1 into a nozzle receptacle of a machining head. An external thread 19 is formed on the peripheral surface of the nozzle 1, by means of which thread the nozzle can be screwed into a nozzle receptacle of a machining head of a laser machining unit for example.

[0054] The laser cutting nozzle 1 according to FIG. 1 is a preferred embodiment of a laser cutting nozzle 1 for three-dimensional laser cutting machining of metal profiles. The shaping of the passage 2 brings about distance-independent, constant fluid dynamic radios at the workpiece surface and in the cutting gap. The shaping of the outer contour is characterized by favorable characteristics for capacitive distance control of the nozzle-workpiece distance.

[0055] The parameters of further preferred embodiments of a laser cutting nozzle are set out in Table 1, together with the corresponding parameters of the nozzle 1 according to FIG. 1, all the example nozzles coinciding at least with respect to the overall length L.sub.ges, the inside (d.sub.E) and outside diameter on the inlet side, the lengths L.sub.E, L.sub.K, L.sub.D of the inflow, convergence and divergence portion 7, 8, 9, the maximum outside diameter d.sub.max, and the length L.sub.KON of the conical peripheral surface 16.

TABLE-US-00001 TABLE 1 Parameters of a plurality of embodiments of laser cutting nozzles. Example No. 1 corresponds to the nozzle according to FIG. 1. d.sub.MI d.sub.MA d.sub.min α.sub.D α.sub.KON α.sub.K No. [mm] [mm] [mm] [°] [°] [°] L.sub.D/d.sub.min d.sub.MI.sup.2/d.sub.min.sup.2 d.sub.MI.sup.2/d.sub.E.sup.2 d.sub.min.sup.2/d.sub.E.sup.2 1 1.94 3.15 1.6 1.5 28 12 4.1 19% 147% 13% 2 2.352 3.15 1.8 2.4 28 11 3.6 29% 171% 17% 3 2.855 4.15 2 3.8 23 10 3.3 42% 204% 21% 4 3.398 4.15 2.6 3.5 23 8 2.5 60% 171% 35% 5 3.7 4.5 2.6 4.8 21 8 2.5 71% 203% 35%

[0056] FIG. 3 shows a laser machining unit 20 comprising a laser cutting nozzle 1 according to one of the above examples. The laser machining unit 20 comprises a machining head 21 that is equipped with a laser cutting nozzle 1 and is intended for three-dimensional laser cutting machining. A laser diode, CO.sub.2 or solid-state laser (not shown in greater detail), in particular a disc laser, having a maximum power of at least 2 kW, is used as the laser source.

[0057] The unit 21 has capacitive distance control of the nozzle-workpiece distance.

[0058] The unit 21 for example carries out three-dimensional laser cutting machining using the nozzle 1, during which machining a cutting gas (e.g. nitrogen or argon) is fed at a pressure of between 8 and 23 bar. A metal profile 22 having a workpiece thickness of from 1 to 4 mm is cut, at least intermittently, at a distance between the nozzle 1 and the workpiece surface that is in a distance range of between 3 and 6 mm.

[0059] For example, construction steel and stainless steel having a sheet thickness of 1 mm is cut at 50 m/min using a laser source at a power of 5 kW.