Device for working a surface of a workpiece by means of a laser beam and method for operating the device

Abstract

The invention relates to a device (2) for working a surface (4) of a workpiece (6) by means of a laser beam (8), comprising a laser system (12) for providing the laser beam (8) and a plasma nozzle (14), which is designed to produce an atmospheric plasma jet (16), wherein the plasma nozzle (14) has a nozzle opening (24, 24′), from which a plasma jet (8) produced in the plasma nozzle (24, 24′) exits during operation, wherein the laser system (12) and the plasma nozzle (14) are arranged in relation to each other and designed in such a way that, during operation, the laser beam (8) exits from the nozzle opening (24, 24′) of the plasma nozzle (14) together with the plasma jet (16). The invention further relates to an assembly (100) having such a device and to a method for operating said device (2).

Claims

1. A device for cleaning a surface of a workpiece by means of a laser beam, comprising: a laser system comprising a laser source and optics, capable of producing a laser beam, and a plasma nozzle, configured for generating an atmospheric plasma beam, the plasma nozzle comprising a nozzle opening, out of which the plasma beam, generated in the plasma nozzle, emerges in operation, wherein the laser system and the plasma nozzle are arranged relative to one another and configured such that, in operation, the laser beam emerges out of the nozzle opening of the plasma nozzle together with the plasma beam, the plasma nozzle further comprising a tubular housing and, in operation, the laser beam runs through the tubular housing of the plasma nozzle, wherein the plasma nozzle further comprises an inner electrode and an inner channel, the inner electrode arranged inside the tubular housing, and in operation the laser beam runs through the inner channel to the nozzle opening, and wherein the laser system is configured to clean the surface and to continuously vary a beam direction of the laser beam such that the position of the laser beam in a cross-section of the nozzle opening changes continuously.

2. The device according to claim 1, wherein the plasma nozzle is configured to generate an atmospheric plasma beam by means of an arc-like discharge in a working gas, wherein the arc-like discharge can be generated by applying a high-frequency high voltage between the inner electrode and the inner channel.

3. The device according to claim 1, wherein the device is configured such that it can be attached to a robotic arm.

4. The device according to claim 1, further comprising a controller configured to operate the device by controlling the generation of the atmospheric plasma beam such that the plasma beam and the laser beam emerge out of the nozzle opening at the same time, and controlling the variation of the laser beam's direction, such that the position of the laser beam in the cross-section of the nozzle opening changes continuously.

5. A method for operating a device according to claim 1, comprising: generating an atmospheric plasma beam in the plasma nozzle, such that the plasma beam emerges out of the nozzle opening of the plasma nozzle, providing a laser beam with the laser system, such that the laser beam emerges out of the nozzle opening of the plasma nozzle at the same time as the plasma beam, and continuously varying the direction of the laser beam such that the position of the laser beam in the cross-section of the nozzle opening changes continuously.

6. The method according to claim 5, further comprising directing the plasma beam emerging out of the nozzle opening and the laser beam emerging out of the nozzle opening onto a surface of a workpiece to be worked.

7. The method according to claim 5, further comprising at least one of the steps of welding, laser soldering, or removing corrosion.

8. A system for working a surface of a workpiece by means of a laser beam, comprising: a robot arm; and a device according to claim 1, wherein the device can be mounted on the robot arm.

9. A device for working a surface of a workpiece by means of a laser beam, comprising: a laser system comprising a laser source and optics, capable of producing a laser beam, and a plasma nozzle, configured for generating an atmospheric plasma beam, the plasma nozzle comprising a nozzle opening, out of which the plasma beam, generated in the plasma nozzle, emerges in operation, wherein the laser system and the plasma nozzle are arranged relative to one another and configured such that, in operation, the laser beam emerges out of the nozzle opening of the plasma nozzle together and at the same time with the plasma beam, the plasma nozzle further comprising a tubular housing and, in operation, the laser beam runs through the tubular housing of the plasma nozzle, wherein the plasma nozzle further comprises an inner electrode and an inner channel, the inner electrode arranged inside the tubular housing, and in operation the laser beam runs through the inner channel to the nozzle opening, and wherein the laser system is configured to continuously vary a beam direction of the laser beam such that the position of the laser beam in a cross-section of the nozzle opening changes continuously.

10. The device according to claim 9, further comprising a controller configured to operate the device by controlling the generation of the atmospheric plasma beam and controlling the variation of the laser beam's direction, such that the position of the laser beam in the cross-section of the nozzle opening changes continuously.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the present invention emerge from the following description of exemplary embodiments, in which reference is made to the attached figures.

(2) FIG. 1 shows an exemplary embodiment of the device according to the invention and of the method according to the invention in a schematic illustration,

(3) FIG. 2 shows a section of the device from FIG. 1 in an enlarged illustration,

(4) FIGS. 3a-c show three examples of nozzle openings and trajectories of the position of the laser beam in the cross-section of the nozzle openings,

(5) FIG. 4 shows an exemplary embodiment of the arrangement according to the invention and

(6) FIG. 5 shows an exemplary embodiment of the use according to the invention of the device or of the method.

DESCRIPTION OF THE INVENTION

(7) The device 2 for working a surface 4 of a workpiece 6 by means of a laser beam 8 has a housing 10, in which a laser system 12 is integrated for providing the laser beam 8, and to which a plasma nozzle 14 is attached for generating an atmospheric plasma beam 16.

(8) Firstly, the structure and the method of operation of the plasma nozzle 14 are described below with the aid of FIG. 2 which shows the area of the plasma nozzle 14 of the device 2 from FIG. 1 in an enlarged illustration.

(9) The plasma nozzle 14 has a tubular housing 18 in the form of a nozzle tube consisting of metal which is screwed to the housing 10 of the device 2. The nozzle tube 18 has a conical tapering 20 on its one end, on which a replaceable nozzle head 22 is mounted, the outlet of which forms a nozzle opening 24, out of which the plasma beam 16 emerges in operation.

(10) On the end opposite to the nozzle opening 24, the nozzle tube 18 is attached to a working gas feed pipe 26 of the housing 10. The working gas feed pipe 26 is in turn connected via a hose package 28, which is attached to the housing 10, to a working gas source (not shown) which is under pressure with a variable throughput. In operation, a working gas 30 is fed from the working gas source through the hose package 28 and the working gas feed pipe 26 into the nozzle tube 18.

(11) In addition, a swirl device 32 having a ring of holes 34 positioned obliquely in the circumferential direction is provided in the nozzle tube 18, through which holes 34 the working gas 30 fed into the nozzle tube 18 is swirled in operation.

(12) Thus, the downstream part of the nozzle tube 18 is flowed through by the working gas 30 in the form of a vortex 36, the core of which runs on the longitudinal axis of the nozzle tube 18.

(13) In addition, an inner electrode 38 is arranged centrally in the nozzle tube 18 and extends coaxially in the nozzle tube 18 in the direction of the nozzle opening 24. The inner electrode 38 is electrically connected to the swirl device 32. The swirl device 32 is electrically insulated against the nozzle tube 18 by a ceramic tube 40. A high-frequency high voltage, which is generated by a transformer 44, is applied to the inner electrode 38 via a high-frequency conductor 42 led through the hose package 28. The nozzle tube 18 is earthed by means of an earth conductor 46 which can also be led through the hose package 28. A high-frequency discharge in the form of an electric arc 48 is generated between the inner electrode 38 and the nozzle tube 18 by means of the applied voltage.

(14) The terms “electric arc”, “arc discharge” or “arc-like discharge” are in this case used as phenomenological descriptions of the discharge, since the discharge occurs in the form of an electric arc. The term “electric arc” is otherwise also used as a discharge form in direct voltage discharges with essentially constant voltage values. In this case, however, it is a high-voltage discharge in the form of an electric arc, i.e. a high-frequency arc-like discharge.

(15) Due to the swirling flow of the working gas, this electric arc 48 is channeled in the vortex core in the area of the axis of the nozzle tube 18, so that it only branches out in the area of the tapering 20 to the wall of the nozzle tube 18.

(16) The working gas 30, which rotates at a high flow velocity in the area of the vortex core and hence in close proximity to the electric arc 48, comes into intimate contact with the electric arc 48 and is as a result partly converted into the plasma state, so that an atmospheric plasma beam 16 emerges out of the plasma nozzle 14 through the nozzle opening 24.

(17) The laser system 12 integrated in the housing 10 of the device 2 has a laser source 62, for example a fibre laser, which in operation generates the laser beam 8. The laser source 62 is supplied with electrical energy via a supply line 64. As an alternative to the laser source 62, the device 2 can, for example, also have an optical fiber which is attached to an external laser source. The laser system 12 additionally has mirror optics 66, by means of which the laser beam 8 generated by the laser source 62 can be deflected.

(18) The laser system 12 and the plasma nozzle 14 are arranged relative to one another and configured such that in operation the laser beam 8 emerges out of the nozzle opening 24 of the plasma nozzle 14 together with the plasma beam 16. The inner electrode 38 of the plasma nozzle 14 has an inner channel 68 for this purpose, the longitudinal axis of which is aligned with the nozzle opening 24. A coupling tube 70 is attached to the inner electrode 38 and extends the inner channel 68 into the housing 10 all the way to the laser system 12. The mirror optics 66 of the laser system 12 are arranged in such a way that the laser beam 8 generated by the laser source 62 is directed into the coupling tube 70, runs through the inner channel 68 of the inner electrode 38 and the nozzle tube 18 all the way to the nozzle opening 24 and thus emerges out of the nozzle opening 24 together with the plasma beam 16.

(19) In this way, the laser beam 8 and the plasma beam 16 in operation reach the surface 4 of the workpiece 6 together and on the same area 72. The workpiece surface 4 is worked by the incident laser beam 8 on the area 72, in which material, such as a contaminant 74, on the surface 4 is vaporised by the laser beam 8. The material 76 vaporised by the laser beam 8 is disintegrated or transformed by the plasma beam 16, so that it cannot precipitate on the surface 4 again. In this way, in particular organic contamination can be removed from a surface, since the organic material removed by the laser beam is disintegrated and oxidised by the plasma beam.

(20) In addition, the device 2 can also be used for removing corrosion, in which corroded material, such as rust, is removed from a workpiece surface 4 by the laser beam 8. The corroded material is disintegrated or transformed by the means of the plasma beam 16, so that it does not precipitate on the surface 4 again. In order to prevent oxidation of the surface with the high temperatures due to the laser beam 8, forming gas is preferably used as the working gas 30, which as a plasma beam 16 has a strongly reducing effect.

(21) While the plasma beam has a diameter of typically several millimetres, the laser beam 8 typically has a diameter of less than 1 mm, in particular less than 200 μm, and therefore has a correspondingly small spot size on the surface 4 to be worked. For this reason, the laser beam 8 is preferably continuously swiveled, so that a larger area of the surface 4 can be worked independently of a relative movement between the plasma nozzle 14 and the surface 4.

(22) For this purpose, the laser system 12 is configured to continuously vary the beam direction of the laser beam 8 such that the position of the laser beam 8 in the cross-section of the nozzle opening 24 varies continuously. To that end, the laser system 12 has a mirror 78 which can be swiveled by means of a corresponding control (not illustrated). The beam direction of the laser beam 8 can be varied by swiveling the mirror 78, so that the laser beam 8 can be directed into the coupling tube 70 at different angles. The coupling tube 70, the inner channel 68 and the nozzle opening 24 are dimensioned in such a way that the laser beam 8 can also reach the nozzle opening 24 at the different angles and can exit through it and out of the plasma nozzle 14. Preferably, the plasma nozzle has a diameter of at least 3 mm, at least in one direction. In the case of a round nozzle opening, the diameter is preferably in the range from 3 mm to 6 mm. In the case of a slit-shaped nozzle opening, the slit length, i.e. the nozzle diameter in the slit direction, is preferably up to 30 mm.

(23) Three examples of nozzle openings 24, 24′ and trajectories 80, 80′ of the position of the laser beam 8 in the cross-section of the nozzle openings 24, 24′ are illustrated in FIGS. 3a-c. The figures each show the cross-section of the nozzle openings, the position of the laser beam in the nozzle opening cross-section (black dot) and the trajectory of the laser beam position in the nozzle opening cross-section by movement of the mirror 78 (dashed arrows).

(24) FIG. 3a firstly shows a round nozzle opening 24 which, for example, can have a diameter of 5 mm. The mirror 78 is controlled such that it continuously moves forwards and backwards in one direction, so that correspondingly the position of the laser beam 8 in the nozzle opening cross-section moves forwards and backwards on a straight trajectory 80. The surface 4 can thereby be worked on a linear area without movement of the plasma nozzle 14.

(25) The device 2 or the plasma nozzle 14, on the one hand, and the surface 4, on the other hand, can be moved relative to one another in order to work a larger surface area on the surface 4. The plasma nozzle 14 is preferably moved transverse to the greatest extension of the trajectory 80 (indicated by the arrow 82). In this way, when the plasma nozzle 14 is moved a strip as wide as possible on the surface 4 of the workpiece 6 is worked.

(26) FIG. 3b shows an alternative slit-shaped nozzle opening 24′ with a slit which is approximately 5 mm long. The trajectory 80 of the position of the laser beam 8 is, as in FIG. 3a, linear and aligned corresponding to the slit direction.

(27) FIG. 3c again shows the round nozzle opening 24 with a diameter of 5 mm. In this exemplary embodiment, the mirror 78 is swiveled in two directions in such a way that the position of the laser beam 8 moves on a circle, i.e. a circular trajectory 80′ results.

(28) A circular trajectory, as in FIG. 3c, has the advantage that the same strip width results independently of the movement direction of the plasma nozzle 14. On the other hand, a linear trajectory, as in FIGS. 3a and 3b, has the advantage that the control of the mirror 78 is simplified and the strip width can be varied continuously by setting the angle between the axis of the trajectory 80 and the movement direction 82.

(29) The previously described device 2 allows workpiece surfaces to be worked in a way which is reliable in terms of the process. It is ensured that the laser beam 8 and the plasma beam 16 strike the same area on the surface to be worked by the fact that the laser beam 8 and the plasma beam 16 emerge out of the nozzle opening 24 together. An elaborate and continuous control for aligning the laser beam 8 and the plasma beam 16 in relation to one another can therefore be dispensed with.

(30) This enables the device to be used for working surfaces which are formed in a complicated way or for working different surface positions which make a swiveling of the device 2 necessary. Such a surface work can be advantageously carried out using a multi-axis robot arm.

(31) FIG. 4 shows an arrangement 100 having such a robot arm 102, in this case a 6-axis robot arm, and the device 2 which is mounted onto the robot arm 102. For this purpose, the device 2 can have mounting means, such as threaded holes, for mounting it on the robot arm 102.

(32) The device 2 can now be moved in any position and aligned arbitrarily using the robot arm 102, in order, for example, to move over a surface of a workpiece which is complicated to work. For this purpose, the arrangement 100 comprises another control device 104 in the form of a computer, by means of which the movements of the robot arm 102 and preferably also the operation of the device 2 can be controlled.

(33) FIG. 5 shows an exemplary embodiment of the use of the device or of the method. The device 2 from FIG. 1 can in particular be used for laser soldering or laser welding. In the case of laser soldering, the laser beam 8 fuses a solder, by means of which two workpieces 112, 114 to be joined are wetted and after the solder has solidified are joined by the soldered seam 116 produced in this way. Here, the surfaces of the workpieces 112, 114 are worked to the extent that they are joined together by the soldered seam 116. The solder is preferably at least partly guided through the plasma nozzle 14. In particular, tin-solder 120 in powder form, for example, can be introduced by a feed 118 provided in the nozzle head 22 into the plasma nozzle 14 and as a consequence into the plasma beam 16. The tin-solder is then fused by the plasma beam 16 and reaches the joint at the soldered seam 116 through the flow of the plasma beam 16 in a targeted manner.

(34) Correspondingly, the device 2 can also be used for laser welding, wherein in this case a welding filler can be introduced through the feed 118 into the plasma nozzle 14.

(35) The arrangement 100 can in particular also be used for laser soldering or laser welding. In this way, soldered or welded joints can be produced controlled by computer at various places on a workpiece.