WO1999056907A1

WO1999056907A1 - Material shaping device with a laser beam which is injected into a stream of liquid

Info

Publication number: WO1999056907A1
Application number: PCT/CH1999/000180
Authority: WO
Inventors: Bernold Richerzhagen
Original assignee: Synova S.A.
Priority date: 1998-04-30
Filing date: 1999-04-30
Publication date: 1999-11-11
Also published as: CA2330426A1; CN1134322C; CN1306467A; CA2330426C; KR100584310B1; KR20010043171A

Abstract

The invention relates to a method and device for shaping material of work pieces (45) using a laser beam which is injected into a stream of liquid (25). The liquid which is to be formed into a stream (25) by a nozzle channel (29) is fed to the nozzle channel opening (28) such that the flow does not swirl, especially without flow components which are tangential to the nozzle channel axis (32). The laser irradiation is focussed on the channel entry plane (30) and the liquid is fed to the channel opening (28) in such a way that a liquid retention space is avoided in the beam focussing ball (38) and in the immediate surroundings thereof.

Description

Material processing device with a laser beam coupled into a liquid jet

The invention relates to a method for material processing according to the preamble of patent claim 1 and a material processing device according to the preamble of patent claim 4.

State of the art

Material processing with laser radiation is used in a wide variety of ways for cutting, drilling, welding, marking and generally for material removal. In order to initiate material removal, a predetermined intensity of the radiation on the material surface to be processed must be achieved. This high radiation intensity was achieved by focusing the laser radiation at the focal point. The disadvantage here, however, is the small axial extent of the focal point (beam waist) in which this high intensity was achieved. Should make deep cuts or holes - 2 -

, the location of the focus point had to be observed very precisely or even adjusted. The beam tapers conically towards the focal point. I.e. In particular when cutting deep, enough material had to be removed from the surface that the conical jet could penetrate to the machining location. Deep cuts or holes therefore always had to be created with sloping side walls.

In order to avoid the focus point tracking and to make narrow cuts and bores with approximately vertical side walls, laser radiation has now been proposed in EP-A 0 515 983, DE-A 36 43 284 and WO 95/32834 to couple the liquid jet directed onto the workpiece to be machined as a light guide.

In DE-A 36 43 284, the laser radiation was supplied with a glass fiber. The end of this glass fiber was washed by a water jet, which was aimed at the workpiece to be machined. The known device had the disadvantage that the diameter of the water jet could never be smaller than that of the glass fiber supplying the laser radiation. Another disadvantage was a dead water area below the glass fiber end, which among other things Generated disturbances in the water jet flow, which ultimately led to its rapid dropping.

EP-A 0 515 983 now tried to avoid these disadvantages by constructing an optical unit with a water jet-shaping nozzle block. In front of the nozzle forming the water jet was a water accumulation chamber with a water inlet and a focusing lens that closes off the chamber from the nozzle inlet for focusing the laser radiation. The location and focal length of the focusing lens were chosen in such a way that the focal point of the laser radiation came to lie in the axial center within the nozzle channel. It was now shown in the machining operation that the nozzle was extremely quickly damaged by the laser radiation, as a result of which the radiation could no longer be formed properly.

An improvement in the laser beam coupling into the liquid jet was made in WO 95/32834, in which the focal point of the laser beam to be coupled is placed in the plane of the nozzle opening and the water accumulation chamber in front of the nozzle - 3 -

opening has been eliminated. This arrangement also resulted in damage to the nozzle during the material processing operation.

Object of the invention

The object of the invention is to provide a method for material processing and a material processing device with a laser beam coupled into a liquid jet, with which or with which material processing with a long machine running time is ensured. A machining interruption should only take place after specified service intervals. An unpredictable interruption, in particular as a result of damage to the nozzle block forming the liquid jet, should be ruled out.

Solution of the task

The solution to the problem for the method according to the invention is described by the features of patent claim 1 and for the material processing device according to the invention by the features of patent claim 4. According to the invention, care is taken that, on the one hand, the radiation to be coupled into the liquid jet is focused into the nozzle entry plane of the liquid-shaping nozzle channel, and the liquid is supplied to the nozzle entry in a fast-flowing manner (free of liquid storage space) and free of fluid swirls. These three requirements together meet a corresponding configuration of an optical unit described below.

Embodiments of the invention

In the following, examples of the method according to the invention and the device according to the invention are explained in more detail with reference to figures. Further advantages of the invention result from the following description. 1 shows a cross section through an optical unit of the material processing device according to the invention,

2 shows a longitudinal section through the optical unit shown in FIG. 1 with an enlarged representation of the liquid feeds to the liquid jet-shaping nozzle block, - 4 -

3 shows a longitudinal section through the nozzle block shown in FIG. 2 and held in a nozzle holder,

Fig. 4 shows a cross section along the line IV - IV in Figure 2 and

FIG. 5 shows an enlargement for illustration in FIG. 3, which shows in particular the generation and guidance of the liquid jet in the nozzle channel.

The optical unit 1 of the material processing device according to the invention, shown with a cross section in FIG. 1, is connected to a laser radiation source 6 by means of a radiation conductor 3 via a radiation conductor plug 5. The radiation source 6 is only shown symbolically here. It is a high-power laser such as an Nd: YAG laser. The radiation 7 emerging from the radiation conductor 3 in the plug 5 is collimated with a collimator 9 to form a beam 10. The beam 10 is guided to a beam expansion unit 11. With the beam expansion unit 11, the diameter of the incoming beam 10 can be changed to that of the emerging beam 13, i. H. expandable. A diameter factor of two to eight is provided for the beam expansion. This expansion ratio permits a variation of the beam waist 15 (diameter of the focal point) of the laser beam 13 described below. The beam expansion factor of the beam expansion unit can be changed by a motor by signals from an adjusting unit (not shown) (“motorized beam expander”). The expanded beam 13 is then provided with a deflecting mirror 17 deflected by 90 ° and directed to a focusing lens 23 as a focusing unit with a further deflection mirror 21 having an adjusting unit 19. The mode of operation and use of the adjusting unit 19 is described below.

It should be pointed out that the theoretical focal point of the focusing optics 23 does not necessarily have to coincide with the beam waist 15 of the focused laser beam 13. A deviation of both locations is given by a beam divergence of the laser beam 13, which u. a. can be influenced with the beam expansion unit 11.

A nozzle block 27 with a nozzle channel 29 is used to form a liquid jet 25. The focusing optics 23 and the beam expansion unit 11 are set or arranged such that the beam waist 15 of the focused beam 13 comes to rest in the nozzle channel input plane 30 of the nozzle channel opening 28. The nozzle - 5 -

channel entrance plane 30 continues on both sides into the surface of the nozzle block 27. FIGS. 2 to 5 show the immediate area around the entrance to the liquid jet-shaping nozzle channel 29. The nozzle block 27 is shown in a further enlarged view in FIG. 3 compared to FIG. 2. The nozzle channel 29 is designed to be circular-cylindrical. The nozzle block 27 is made of a material that is transparent to the laser radiation (here with a wavelength of 1.06 μm) and is mechanically hard, such as quartz. However, since it is extremely small, it can also consist of diamond. A nozzle block 27 made of diamond has a longer service life than one made of quartz, the end of the service life being noticeable by a liquid jet 25 which bubbles up after a short liquid jet length.

The nozzle block does not necessarily have to be made of a material which is transparent to the laser radiation in order to take advantage of the conditions of total reflection on the nozzle channel wall. It can also consist of a non-transparent, radiation-absorbing material, provided that the nozzle channel wall is provided with a coating which reflects the laser radiation and which should be abrasion-resistant to the liquid jet. In the case of a non-transparent nozzle stone material, the nozzle surface should also have a reflective coating (protection in the event of adjustment errors) and also the underside of the nozzle stone (protection against radiation which is reflected by the workpiece or the plasma cloud on the workpiece). The nozzle block 27 shown in FIG. 3 has a flat surface 30, to which the axis 32 of the nozzle channel 29 extends perpendicularly. The edge 31 on the nozzle channel opening 28 between the surface 30 and the channel wall is sharp-edged and preferably has a radius of less than 5 μm. This rounded edge 31 is one of further requirements described below for generating a liquid jet 25 with a large liquid jet length. It suppresses the formation of fluid swirls. The nozzle block 27 is inserted into a nozzle holder 33. The transition 34 between the nozzle holder 33 and the nozzle block 27 is designed such that there is no step. A step would also produce fluid vortices which would continue into the fluid jet 25 formed with the nozzle channel 29. The nozzle block 27 shown in FIG. 3 has an outside diameter of 2 mm and a height of 0.9 mm. A copy made of a diamond is still within a reasonable cost range with this size. - 6 -

As already explained above, the liquid jet-shaping nozzle channel 29 is circular-cylindrical, here for example with a diameter of 150 μm and a length of approximately 300 μm. The length of the nozzle channel 29 should not be greater than twice the diameter of the nozzle channel. A conically widened opening 26 adjoins the outlet of the nozzle channel 29. The cone tip angle here is eighty degrees. The inner jacket 35 of this cone continues in the nozzle holder 33.

The conical design of the inner jacket 35 facilitates the application of a reflective coating, in no way disturbs the liquid jet and, by virtue of its inclination, reinforces the reflection behavior for possibly from the liquid jet 25 as a result of mechanical inhomogeneities (shock wave, impurities which have slipped despite filtering ...) emerging radiation. The cone angle is chosen so large that radiation emerging from the liquid jet does not hit it at all or only at a very flat angle. The liquid supply to the nozzle channel 29 takes place via a narrow, disk-shaped interior 36, the height of which corresponds approximately to half the diameter of the nozzle channel 29. The diameter of the interior 36 corresponds to the diameter of the nozzle holder 33. In this interior 36, radially to the axis 32 of the nozzle channel 29 in a star-shaped arrangement twenty feed lines 37 are round in cross section, the adjacent side walls of which merge into one another when they open into the interior 36. This arrangement of the supply lines 37 supports a vortex-free (radial) liquid supply to the nozzle channel 27. A pressure-reducing filter 39 is arranged on the inlet side of the supply lines 37. An annular space 40 adjoins this filter 39 and is supplied with liquid via a supply line 41. The filter 39 serves to generate a uniform liquid pressure in the twenty supply lines 37, as a result of which there is a symmetrical liquid flow towards the nozzle inlet. Since the supply line 41 takes place on only one side, the feed lines 37 adjacent to the supply line 41 would have a higher pressure than the opposite ones without a filter 39. Tangential flow components in the region of the nozzle channel opening 28 cannot therefore develop. So that the laser radiation can penetrate to the nozzle inlet opening, the disk-shaped interior 36 is covered in a liquid-tight manner with a cover 43 which is transparent for the laser radiation used. - 7 -

The low height of the interior 36 gives the liquid a high flow rate. As a result of the high flow rate, heating of the liquid in the focusing cone 38 by the laser radiation penetrating it is excluded (or greatly reduced). Due to the configuration described above, the disk-shaped interior 36 is such that, in particular in the radiation focusing cone 38 of the laser radiation, no liquid stowage space, which would favor the formation of a thermal lens preferably by radiation absorption, cannot form. A thermal lens would make it impossible to focus the laser beam properly and in the center (axis 32) of the nozzle channel opening 28. The presence of a thermal lens would result in poorer focusing of the radiation since the thermal lens acts as a diverging lens. The laser radiation would hit the opening edge of the nozzle and / or the nozzle surface and thus damage it. Furthermore, the thermal lens formed by heating the liquid would not be stable in place. An optimal radiation coupling into the liquid jet 25 would then no longer exist.

Due to the star-shaped (radial) arrangement of the inlets 37, a pressure-reducing filter 39 between the inlet of the inlets 37 and the annular space 40, a stepless transition 34 in the flow area of the liquid between the nozzle block 27 and the nozzle holder 33 and the small (rounding radius <5 μm) rounding of the Edge 31 at the liquid inlet into the nozzle is only a vortex-free flow as a prerequisite for a liquid jet 25 of great jet length. Degassing of the liquid and removal of particles from the liquid also have a positive effect on the generation of a long jet length. Care must also be taken to ensure that the fluid supply is free of pressure pulsations. The cylindrical shape of the free liquid jet is namely unstable. Due to its surface tension, the liquid tries to achieve a different shape, namely that of a sphere. The liquid jet thus disintegrates into individual drops after a certain length of propagation. An infinitesimally small radial disturbance of the liquid jet during its formation quickly increases, so that jet constrictions can occur, which can drip the jet. The air surrounding the jet, which is carried away by friction, also increases this effect. A liquid jet of great jet length can only be generated by the measures listed above for carrying out a trouble-free liquid supply. - 8th -

It has also surprisingly been found that when the liquid jet 25 strikes an as yet unprocessed workpiece surface, a shock wave begins to run upward therein. As a result of this shock wave, the liquid flow is no longer laminar and part of the laser radiation coupled into the liquid jet 25 at the entrance of the nozzle opening emerges from the liquid jet 25 as a result of irregularities generated by the shock wave on the surface of the surface of the liquid jet. This emerging radiation would hit the nozzle block 27, pass through it and then hit the metal wall of the nozzle holder 33. The radiation would then be absorbed here under local heating. This could cause the material of the nozzle holder 33 to melt or evaporate, which would result in destruction of the nozzle holder 33 and the nozzle block 27. To prevent this process, the inner wall 35 is conical and provided with a reflective coating. The laser radiation emerging as a result of irregularities in the surface of the liquid jet jacket is thus reflected here and cannot penetrate through the nozzle block 27 to the materials to be absorbed. If the workpiece 45 is pierced or cut through, there are no or shock waves with only minimal energy.

The nozzle block 27, although durable in the arrangement described here, is easily replaceable. To replace it, only an insert 46 has to be unscrewed.

For tightness control, the insert 48 receiving the transparent cover 43 has a groove 54 which runs around its outer jacket and which opens into a control bore 50. If there is liquid in the control bore 50, the sealing ring 58a has become leaky. If the sealing ring 58b now also leaked, liquid could reach the surface 60 of the transparent cover 43, which would lead to a severe impairment in the focusing and guiding of the laser beam. To avoid this, the sealing rings 58a and 58b are replaced whenever liquid is registered in the control bore 50.

A force sensor 47 is arranged below the workpiece 45 to be machined. The position of the force sensor 47 is selected such that it emits a maximum electrical signal to a control device 49 when it is hit completely by the liquid jet 25 (without deflection). The force sensor 47 is in the geometric axis 32 of the - 9 -

Liquid jet 25 arranged. If the liquid jet 25 strikes a still unprocessed workpiece 45 with the laser beam coupled in, then no signal is present, since the workpiece 45 first has to be pierced by the jet 25. If the workpiece 45 has already been drilled through or has an incision through which the beam 25 passes, then the beam 25 strikes the slot side or borehole wall when the workpiece 45 is moved. In this case, only a part of the beam 25 still hits the force sensor 47. The signal emitted to the control device 49 is smaller than when the beam 25 is fully incident. The degree of material removal can thus be determined with the force sensor 47.

The control device 49 is also connected to a displacement device of the workpiece 45. The displacement device is only symbolically indicated in FIG. 1 by two double arrows in the horizontal directions x and y 51a and 51b, which are intended to indicate a flat, two-dimensional displacement possibility. Depending on the determined value of the force sensor 47, the control device 49 now controls the displacement speed of the workpiece 45 according to a predetermined cutting pattern in the two directions 51a and 51b. The force sensor 47 can thus regulate the feed of the workpiece 45 to be machined in an energy-optimized manner, in which the workpiece 45 is always moved when sufficient material removal has been achieved.

The control device 49 is also connected to the radiation source 6. The laser output power can thus also be set as a function of the measured value of the force sensor and the workpiece displacement speed. If, for example, a step mode for workpiece displacement is used in a pulsed laser, the laser emits a number of pulses at one point before the workpiece 45 is moved on by one step. The step mode can, for example, take place with a step repetition frequency of 100 Hz.

In addition to the beam guidance of the laser beam already explained above, the optical unit 1, as can be seen in FIG. 1, has means for optimal adjustment and monitoring of the position of the laser beam waist (focal point of the radiation) with respect to the nozzle inlet opening or the axis 32 of the nozzle channel 29. For this purpose, the radiation 52 of a white light source 53 is superimposed on the expanded laser beam 13. This is done with the deflection mirror 17. The deflection mirror 17 reflects the laser radiation completely, but transmits the white light radiation 52 from the white light source 53 located behind it. - 10 -

The radiation from the source 53 is guided together with the laser radiation via the deflecting mirror 21 into the focusing unit 23 and, with correct optical alignment, is focused in the nozzle inlet plane 30 at the location of the axis 32. The deflection mirror 21 is partially transparent to the white light radiation 52. To check the correct beam adjustment, only the radiation from source 53 is used without a laser beam. If there is a misalignment, the white light radiation focused with the focusing unit 23 illuminates the nozzle edge 31 or its surroundings. The surface surrounding area of the nozzle inlet opening is viewed with a video camera 55 via a telescope 56 and the deflecting mirror 21, which is partially transparent to the white light radiation. The white light experiences a beam displacement as it passes through the deflecting mirror 21 due to its thickness. This beam displacement is corrected by a plane-parallel glass plate 57.

The deflecting mirror 21 can be tilted by an adjustment unit 19. The deflection mirror 21 is now tilted with the adjusting elements in such a way that the focal point of the white light beam comes to lie symmetrically to the location of the channel axis 32.

To achieve this, proceed as follows: the deflecting mirror 21 is tilted until a radiation reflex can be detected at the nozzle channel edge 31, and then is tilted in the opposite direction while measuring the tilt angle (~ displacement path of the jet on the nozzle channel opening) until on on the opposite nozzle channel edge 31, a radiation reflex of the same reflected intensity can also be determined, followed by a renewed tilting movement with half the tilt angle. The focal point now lies in a plane which contains the nozzle channel axis 32. To align with the location of the channel axis 32, a further analog beam axis setting is now made perpendicular to the previous tilt direction. The white light source 53 can be dispensed with if the deflecting mirror 21 is made slightly transparent (approximately 2%) for the radiation from the laser source 6. The telescope and the glass plate 57 must then also be designed and non-reflective for the laser radiation. The video camera 55 must be provided with a chip that is sensitive to the laser radiation. In the event of incorrect adjustment, the laser radiation is then reflected from the nozzle edge or its surroundings. The reflected radiation is then viewed via the telescope with the video camera 55 and an adjustment is made via the above-mentioned adjustment unit 19 and the beam expansion unit 11. To be - 11 - To avoid damage to the nozzle channel and the nozzle surface, the adjustment is carried out with reduced laser power. Since the laser beam properties can change at high beam intensities compared to those at lower power, the deflection mirror 21 and possibly the beam expansion unit 11 are started to be adjusted while continuously increasing the laser power.

To check the centric setting, the output lens of the beam expansion unit 11 can now be adjusted such that the diameter of the beam waist of the laser beam 13 is increased until the nozzle channel edge 31 (ie the nozzle channel opening 28) is illuminated uniformly. Only with uniform lighting has a central alignment been achieved beforehand. The exit lens of the beam expansion unit 11 is now shifted in the opposite direction until a uniform nozzle opening edge illumination occurs again. The intermediate position then results in a setting for optimal focusing on the nozzle channel entrance plane, the focused beam being symmetrical about the channel axis 32. When using an Nd: YAG laser, water can be used as the liquid for the liquid jet. Water has a low radiation absorption at 1.06 μm. However, this low absorption can be sufficient to form thermal lenses in front of the nozzle inlet. A silicone oil, in particular from the group of the polymethylsiloxanes, is therefore preferably used in certain applications. If water is used as the liquid, then laser radiation should be used which has an absorption of less than 0.2 cm ^"1 , preferably less than 0.15 cm ^1. If radiation with a higher absorption is used, the liquid jet is used If the radiation absorption in the liquid is high, evaporation effects can occur, for example, the formation of the thermal lens at the focal point before the nozzle entry cannot be sufficiently suppressed even when the flow is optimized, resulting in low absorption values for water as the liquid used with radiation in the wavelength range from 150 nm to 1100 nm, preferably from 190 nm to 920 nm and between 1040 nm and 1080 nm (in the range around 1000 nm there is an absorption peak). It is therefore preferred to use diode lasers, YAG lasers, frequency-doubled YAG - Lasers, excimer lasers and copper vapor lasers can be used. A YAG laser has, for example - 12 -

the advantage that mature, commercially available units are available; they can also be used to achieve high average performance.

The radiation can be continuous or pulsed. In the case of pulsed radiation, the liquid can cool cut edges produced using the method explained above. Heat generated by absorbed radiation in the liquid jet is also dissipated. Because water has a very high heat capacity, high radiation powers can be pulsed into the liquid jet. When using a Nd'.YAG laser and water as the liquid, up to 20 kW pulse power with pulse lengths of 20 to 500 μs, an average power of 600 W and a pulse rate of up to 5 kHz are coupled in.

However, quality-switched Nd: YAG lasers (Q-switched YAG) with pulse lengths of typically 50 to 250 ns with an average power of 20 to 120 W and a pulse rate of up to 60 kHz can also be used. It is also possible to use mode-coupled lasers with pulse lengths in the femtosecond range. Continuously radiating lasers (e.g. cw YAG) can also be used. Here, however, the average power is limited by the lack of radiation interruption. Then only about 700 W radiation power of an Nd: YAG laser can be coupled into an 80 μm thick water jet. At higher laser power densities, the water would heat up so much due to the radiation absorption that evaporation would start from a certain beam length. This would cause the beam to drip; proper radiation control would no longer exist.

The nozzle block 27 described above was produced from quartz or diamond, that is to say from a material transparent to the laser radiation. The nozzle outlet and also the adjoining wall of the nozzle holder 33 were conical and were mirrored for the laser radiation. The nozzle block 27 can now also be produced from a material that strongly reflects the laser radiation. A gold nozzle block can be used for a laser radiation of 1.06 μm. Since pure gold is too soft, traces of copper and silver must be added to achieve a hardness of 150 to 225 HV.

Claims

- 13 patent claims

1. A method for the material processing of workpieces (45) with a laser beam coupled into a liquid jet (25), characterized in that the liquid to be formed with a nozzle channel (29) into a jet (25) for the nozzle channel opening (28) is free of eddies, in particular without a flow component tangential to the nozzle channel axis (32), the laser radiation focused on the channel entrance plane (30) and the liquid being guided to the channel opening (28) in such a way that a liquid storage space is avoided in the radiation focusing cone (38) and its immediate vicinity.

2. The method according to claim 1, characterized in that the presence of a liquid jet (25) is detected at the location of an extension of the nozzle channel axis (32) below the workpiece (45) and the workpiece (45) is only displaced upon detection and / or the laser power to be coupled in is changed.

3. The method according to claim 1 or 2, characterized in that the nozzle channel opening (28) and its edge region is optically imaged, the beam axis of the laser beam focused on the channel entrance plane, which has a non-material-processing energy or a congruent with the laser beam

Illumination beam is shifted parallel to the nozzle axis (32) until a radiation reflex can be detected at the nozzle edge, then a beam axis movement is carried out in the opposite direction while measuring the displacement path until a radiation reflex with a more reflected intensity can be determined at the opposite nozzle edge region, then a backward movement with the half of the displacement path and then perpendicular to this displacement direction, also parallel to the nozzle axis (32), a further analog beam axis setting is carried out in order to align the laser beam centrally on the liquid jet-shaping nozzle channel (29). - 14 -

4. Material processing device for processing workpieces (45) according to a method according to one of claims 1 to 3 with a laser radiation source (6) and by means of a nozzle channel (29) of a nozzle block (27) shaped liquid jet (25), in the an optical focusing unit (23) the laser beam

Laser source (6) is coupled in and guided therein, characterized in that the focusing unit (23) is arranged in relation to the inlet opening (28) of the nozzle channel (29) such that the focal point of the laser radiation in the plane (30) of the nozzle opening (28) lies and the liquid supply (36, 37, 39, 40) to the nozzle opening (28) is designed in such a way that there are no liquid vortices in the region of the

Nozzle opening (28) and of the nozzle channel (29) occur, and the liquid supply area irradiated or radiated by the focusing cone (38) and its immediate surroundings are designed to be free of liquid storage space.

5. Material processing device according to claim 4, characterized by a disk-shaped antechamber (36) surrounding the nozzle channel opening (28) with a plurality of liquid supply lines (37) opening into it radially, the height of the antechamber (36) corresponding to the nozzle channel radius, also in the area of the nozzle channel opening (28) in order to avoid a liquid storage space, to have a flow velocity of the liquid which is only slightly lower than in the nozzle channel (29), and the side walls of the liquid feed lines (37) merge into one another at the point of entry into the anteroom (36) and in particular the liquid supply lines (37) are arranged in the form of a beam, the axes of adjacent liquid supply lines (37) preferably having the same central angles so that the liquid flowing to the nozzle channel opening (28) does not receive any tangential flow components with respect to the nozzle channel axis (32).

6. The device according to claim 4 or 5, characterized by the shortest possible nozzle channel length, which is preferably smaller than twice the nozzle channel diameter. - 15 -

ser, and the nozzle channel outlet (26) has a conically shaped output part, the opening angle of which is larger than a possible partial radiation of the injected laser radiation emerging from the liquid jet (25) due to instabilities, and preferably with a laser radiation with a wavelength in the range from 150 nm to 1100 nm, in particular in the range from 190 nm to 920 nm and 1040 nm to 1080 nm, is greater than sixty degrees, in particular eighty degrees.

7. The device according to claim 6, characterized in that the cone (35) designed nozzle outlet (26) for the laser radiation is reflection-coated and preferably the nozzle block (27) at a wavelength of the radiation source used in the range from 150 nm to 1100 nm, preferably in the range from 1040 nm to 1080 nm made of quartz, in particular of diamond.

8. Device according to one of claims 4 to 6, characterized in that the nozzle block (27) is made of a material which strongly reflects the laser radiation.

9. The device in particular according to one of claims 4 to 8, characterized by an in the extension of the nozzle channel axis (32) below the nozzle outlet arranged force sensor (47) above which the workpiece (45) to be machined can be attached, the sensor (47) such is designed so that it emits a signal when the liquid jet (25) strikes, so that it can be determined when the workpiece (45) has been penetrated approximately in the nozzle channel axis direction by the liquid jet (25) guiding the laser beam.

10. Device according to one of claims 4 to 9, characterized by a liquid supply control unit, which eliminates liquid pressure pulsations of the liquid to be supplied to the nozzle inlet, preferably degasses the liquid and in particular removes this particle. - 16 -

11. The device according to one of claims 4 to 10, characterized by a viewing unit (21, 57, 56, 55) of the nozzle channel opening (28) and its surroundings and an adjusting unit (19, 21) for displacing the falling on the nozzle channel opening (28) focused laser beam (13) such that it comes to rest in the center of the opening (28).