Laser beam cutting device and method for laser beam cutting

Abstract

The invention relates to a laser beam cutting device 100 for cutting metal workpieces 12, having a cutting head 102 for directing a laser cutting beam 105 along a beam axis 105a onto a 5 process zone 13 of a workpiece 12; and a device 104 for generating a sound pressure directed onto the process zone by means of sound waves 107. The device 104 for generating the sound pressure directed towards the process zone has an array of a plurality of ultrasonic generators T and is designed to generate at least one pressure node of the sound pressure that is movable in its spatial position by adjusting the phase and at least one parameter from the group including 10 frequency and signal type of at least one of the ultrasonic generators T. A method for laser beam cutting is also specified.

Description

[0001] Bystronic Laser AG

[0002] Lawyer file: PAT 4511 / 035-PCT

[0003] Laser beam cutting device and method for laser beam cutting

[0004] The invention relates to a laser beam cutting device, in particular for cutting metal workpieces, a method for laser beam cutting, in particular for cutting metal workpieces, and a computer program product.

[0005] In laser cutting machines, a cutting gas is typically used to cut parts from metal workpieces, e.g. sheet metal, metal profiles or metal pipes. Such laser cutting machines have a laser power of at least 1 kW. The primary task of the cutting gas is to expel the molten material from the workpiece. Other tasks of the cutting gas include cooling the material and providing a protective gas effect, in particular against oxidation. There are different types of cutting gases used: In oxygen cutting, oxygen is used as a reactive gas. This typically results in low cutting speeds and good cutting quality, especially with higher sheet metal thicknesses. The disadvantage of this is the resulting oxide layer. In fusion cutting, pure nitrogen can be used to expel the melt. In contrast to the use of oxygen as a cutting gas, higher cutting speeds are possible and a sufficiently good cutting quality is achieved. Furthermore, compressed air can be used as a cutting gas instead of pure nitrogen for cutting. This is cheaper, but results in a lower cutting quality. A mixed gas, e.g. a mixture of nitrogen with approximately 3% oxygen by volume, can be used. This results in higher maximum cutting speeds and better quality, e.g. in terms of burr formation and roughness.

[0006] DE10012792 B4 describes a method for cutting components in which a molten phase is created by a local energy input with a laser beam. The component can be made to vibrate in the area of the molten phase by directing a protective or cutting gas with superimposed vibration onto the area of the molten phase. M. A. Andrade, N. Perez and J. Adamowski, “Review of Progress in Acoustic Levitation,” Brazilian Journal of Physics, 2017, no. 2, pages 190 to 213, describe methods for moving objects with sound waves. R. Morales, I. Ezcurdia, J. Irisarri, M. A. B. Andrade and A. Marzo, “Generating Airborne Ultrasonic Amplitude Patterns Using an Open Hardware Phased Array,” Applied Sciences, 26 March 2021 , 11 (7), 2981 , describe a generation of ultrasound amplitude patterns. WO2024104690 A1 describes process monitoring by microphone. WO2023166730 A1 discloses a laser processing head provided with a gas-filled chamber filled with a processing gas and is provided with: a casing that houses therein a processing lens for condensing the laser light; a nozzle that is attached to the casing and through which the laser light to be radiated on the workpiece and the processing gas to be jetted from the gas-filled chamber to the workpiece pass; and an ultrasonic wave generation unit that generates an ultrasonic wave for oscillating the processing gas in the gas-filled chamber. The laser processing head removes a molten product by the processing gas with ultrasonic oscillation being applied. JP6312476 B2 describes a laser cutting device comprising a laser beam irradiation device which can irradiate a laser beam, and a pressure wave irradiation device that gives shear force to a portion to be cut with the laser beam, through the irradiation of an ultrasound.

[0007] Disadvantages of laser beam cutting using cutting gases are the costs, and the availability and sustainability of the cutting gases, especially the low efficiency of the use of the cutting gases.

[0008] The object of the invention is to provide a method and a device that enable cost-effective and high-quality laser beam cutting of metal workpieces.

[0009] This object is achieved by a laser beam cutting device for cutting metal workpieces according to claim 1 , a method for laser beam cutting metal workpieces according to claim 8, and a computer program product according to claim 15.

[0010] One embodiment relates to a laser beam cutting device for cutting metal workpieces, including a cutting head for directing a laser cutting beam along a beam axis onto a process zone of a workpiece; and a device for generating a sound pressure directed onto the process zone by means of sound waves; wherein the device for generating the sound pressure directed towards the process zone has an array of multiple ultrasonic generators and is designed to generate at least one pressure node of the sound pressure, movable in its spatial position, by adjusting the phase and at least one parameter from the group including frequency and signal type of at least one of the ultrasonic generators. The device for generating the sound pressure directed towards the process zone can be designed to generate the sound waves in the gaseous medium. The sound pressure can be an air sound pressure or a gas sound pressure.

[0011] The frequency may be in the range of 5 kHz to 100 MHz, preferably 20 kHz to 30 MHz. The phase may, for example, be in the range from 0° to 180°. The signal type may be selected from sine waves, square waves, triangular waves, sawtooth waves, modulated waves, in particular with amplitude modulation or frequency modulation, or any combination thereof.

[0012] The laser beam cutting device makes it possible to use no or significantly less cutting gas during laser beam cutting. Molten material of the workpiece can be removed from the process zone using at least one pressure node of the sound pressure. If laser beam cutting is carried out without the use of, for example, oxygen as a cutting gas, equipment for supplying cutting gas, such as regulators and lines for the cutting gas, is not required. If the laser beam cutting is based on, for example, oxygen, low-pressure lines and low-pressure regulators, e.g. for pressures below 1 bar, are sufficient. These advantages in turn enable a simple construction of a cutting head for laser beam cutting. Furthermore, fewer wearing parts, such as an assortment of nozzles for the cutting head, are required. This enables cost-effective and high-quality laser cutting of metal workpieces. In particular, laser beam cutting can be carried out without cutting gas or with a low consumption of cutting gas. In addition, in some embodiments the use of high- pressure cutting gas can be avoided. Furthermore, the laser beam cutting device enables high cutting quality, so that post-processing of the cut metal workpieces can be avoided or is only required to a limited extent.

[0013] The array can be understood as a spatial arrangement, e.g. a two- or three-dimensional arrangement, of the ultrasonic generators. The process zone can be understood as a cutting zone. The signal type can be, for example, a sinusoidal and / or rectangular signal.

[0014] Since the device for generating the sound pressure directed at the process zone has several ultrasonic generators, the sound waves of the ultrasonic generators can be superimposed. By superimposing the sound waves of the ultrasonic generators, a desired sound pressure, in particular a high sound pressure, can be generated. By superimposing the sound waves from the array of ultrasonic generators, such as ultrasonic loudspeakers, it is possible to influence the spatial position of one or more acoustic pressure nodes in a time-dependent manner. By changing the pressure node position(s) in space over time, the molten material of the workpiece can be moved.

[0015] With the help of the sound waves generated by the ultrasonic generators, the molten material of the workpiece can be expelled during laser cutting. This can be done without cutting gas or in combination with a cutting gas. The cutting gas used can be, for example, nitrogen alone, a mixed gas, e.g. a mixture of nitrogen with approx. 3% oxygen by volume, oxygen alone or compressed air alone. When using sound waves during laser cutting performed with nitrogen or compressed air as the cutting gas, the amount of cutting gas can be reduced or the cutting gas can be omitted altogether, since nitrogen and compressed air are not used due to the reactive nature of the gas. A reactive mixed gas or oxygen can be used when the sheet metal of the workpiece has a high thickness and / or when a substantially burr-free cutting result is desired. The positions of the pressure nodes of the sound waves that can be adjusted or set with the ultrasonic generators can depend on the gaseous medium flowing through them. Depending on the gaseous medium used, i.e. air, a cutting gas and / or an auxiliary gas, the positions of the pressure nodes can therefore vary. The auxiliary gas may contain or be a cutting gas.

[0016] Through the adjustable position of the pressure nodes and / or the adjustable strength of the sound waves, the dynamics, e.g. the mobility and the state of aggregation, of the melt pool can also be specifically influenced, e.g. disturbed, reduced or amplified. For example, high dynamics of the melt pool, which generates splashes and / or waves of the melt, can be damped. In addition, the cutting quality can be positively influenced by the combination of sound waves and cutting gas. With process monitoring, e.g. using a microphone, a camera and / or optical coherence tomography (OCT), the melt pool dynamics can be recorded and specifically influenced using sound waves.

[0017] The number of pressure nodes that can be generated and / or a range of the adjustable spatial position of the pressure node(s) can be predetermined and / or adjusted by the number, arrangement and / or orientation of the ultrasonic generators. The number of pressure nodes and / or the spatial position of the pressure node(s) can further be adjusted by means of the frequency, phase and / or signal type of at least one of the ultrasonic generators.

[0018] The metal workpiece can be, for example, a sheet metal, a pipe or a profile. The term “laser beam cutting” can be referred to synonymously as laser cutting or simply cutting. The same applies to word combinations and grammatical variations of this term.

[0019] The device for generating the sound pressure directed towards the process zone can be designed to set at least one constructive interference of the sound waves when generating the at least one pressure node movable in its spatial position in the region of the process zone, which generates an expulsion force directed towards molten material of the workpiece for expelling the molten material from the process zone. By setting a constructive interference, a targeted force can be applied to the material of the workpiece that is molten in the cutting area of the process zone, which removes the molten material from the workpiece.

[0020] The device for generating a sound pressure directed towards the process zone can be designed to oscillate the position of the at least one movable pressure node and / or a position of the at least one constructive interference and / or to specify it depending on the cutting direction. In this way, the pressure node can be precisely and / or flexibly aligned to the target area, i.e. the process zone.

[0021] The ultrasonic generators of the array can span at least one array surface that is arranged at least partially about the beam axis and is flat and / or curved. For example, the array may form at least one flat surface or a partially spherical arrangement. At least one of the ultrasonic generators of the array can be arranged such that a central axis of an angular range, emanating from the ultrasonic generator, of the sound wave generated by the ultrasonic generator is aligned parallel to or at an angle to the beam axis. At least one of the ultrasonic generators may have an adjustment device designed to statically and / or dynamically adjust the orientation of the central axis of the sound wave generated by the respective ultrasonic generator. At least one of the ultrasonic generators and / or at least one of the adjustment devices can be designed to be controllable. This allows the spatial position of at least one of the pressure nodes to be changed quickly. The central axes of several ultrasonic generators can be aligned the same or differently.

[0022] A control unit for controlling the array of ultrasonic generators may be provided, wherein the control unit is designed to control at least one of the ultrasonic generators of the array individually and / or a plurality of the ultrasonic generators in at least one defined group. This allows the strength and orientation of the sound wave to be varied. The adjustment devices can also be designed to be controllable in such a way that the orientations of the ultrasonic generators are adjusted individually and / or in a coordinated manner.

[0023] The laser beam cutting device may include a device for calibrating the spatial position of the movable pressure node of the sound pressure, which device includes at least one element selected from a force sensor, an ultrasonic microphone and an optical measuring device, e.g. OCT. Furthermore, a device for process monitoring of the spatial position of the movable pressure node of the sound pressure can be provided, which device has at least one element selected from a force sensor, an ultrasonic microphone and an optical measuring device, e.g. OCT. The process monitoring device may include the calibration device, or conversely, the calibration device may include the process monitoring device. Calibration can be used to specify target values for the position of the pressure node. Deviations from the target values can be compensated for by process monitoring. At least one resonator may also be provided to amplify or attenuate sound waves. For example, one or more cavities can be provided as a resonator.

[0024] In the laser beam cutting device, a device for introducing an auxiliary gas into the process zone and for additionally expelling molten material of the workpiece from the process zone by means of the auxiliary gas may be provided. The auxiliary gas may be selected from at least one inert gas, at least one reactive gas, compressed air, and a combination thereof. The inert gas can be selected from nitrogen, noble gas, compressed air and any combination thereof. The reactive gas can be selected from oxygen and a reactive mixed gas, e.g. nitrogen with approximately 3% oxygen by volume. The auxiliary gas may contain or be a cutting gas.

[0025] A further embodiment relates to a method for laser beam cutting of metal workpieces, in particular with a device according to the above embodiment and modifications thereof, including directing a laser cutting beam along a beam axis onto a process zone of a workpiece; and generating a sound pressure directed onto the process zone by means of sound waves, wherein an array of multiple ultrasonic generators generates at least one pressure node of the sound pressure that is movable in its spatial position and wherein the phase and at least one parameter from the group including frequency and signal type of at least one of the ultrasonic generators is adjusted. The signal type can be, for example, a sinusoidal and / or rectangular signal. The sound pressure directed towards the process zone can be generated in the gaseous medium. The sound pressure can be an air sound pressure or a gas sound pressure.

[0026] The frequency may be in the range of 5 kHz to 100 MHz, preferably 20 kHz to 30 MHz. The phase may, for example, be in the range from 0° to 180°. The signal type may be selected from sine waves, square waves, triangular waves, sawtooth waves, modulated waves, in particular with amplitude modulation or frequency modulation, or any combination thereof.

[0027] When generating the at least one pressure node movable in its spatial position in the region of the process zone, at least one constructive interference of the sound waves can be set, which generates an expulsion force directed towards molten material of the workpiece for expelling the molten material from the process zone.

[0028] The position of the at least one movable pressure node and / or a position of the at least one constructive interference can be oscillated and / or specified depending on the cutting direction.

[0029] The array of ultrasonic generators can generate at least one modulated or modulatable sound wave. The position of the movable pressure node can be moved by adjusting at least one parameter from the group including a frequency and a phase position of the at least one sound wave.

[0030] The spatial position of the movable pressure node of the sound pressure can be calibrated using at least one element selected from a force sensor, an ultrasonic microphone and an optical measuring device. Furthermore, process monitoring can be carried out with at least one element selected from a force sensor, an ultrasonic microphone and an optical measuring device. In addition, sound waves can be amplified or attenuated using at least one resonator.

[0031] An auxiliary gas can be introduced into the process zone and molten material from the workpiece can also be expelled from the process zone using the auxiliary gas. The auxiliary gas may be selected from at least one inert gas, at least one reactive gas, compressed air, and a combination thereof. The auxiliary gas may contain or be a cutting gas. The sound waves may be introduced into the process zone of the workpiece via a gaseous medium.

[0032] A further embodiment relates to a computer program product, including one or more program modules that cause the laser beam cutting device according to the preceding embodiment or variations thereof to carry out the steps of the method according to the preceding embodiment or modifications thereof, in particular when the program modules are loaded into a memory unit or a computing unit of the laser beam cutting device. With the above embodiment or modifications of the method for laser beam cutting of metal workpieces, the same advantages and functions can be achieved as with the embodiment or modifications of the laser beam cutting device for cutting metal workpieces, in particular with identical and / or analogous features.

[0033] It is understood that the above-mentioned features and those to be explained below can be used not only in the combinations indicated, but also in other combinations or on their own, without departing from the scope of the present invention.

[0034] In the following, the invention is explained in more detail on the basis of exemplary embodiments with reference to the accompanying drawings, which likewise disclose features that are essential to the invention. These exemplary embodiments are used for illustration purposes only and are not to be construed as limiting. For example, a description of an exemplary embodiment with a large number of elements or components should not be interpreted to the effect that all of these elements or components are necessary for implementation. Rather, other exemplary embodiments can also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different exemplary embodiments can be combined with one another, unless otherwise indicated. Modifications and variations which are described for one of the exemplary embodiments can also be applied to other exemplary embodiments. To avoid repetition, elements that are the same or that correspond to one another are denoted by the same reference signs in different figures and are not explained more than once. In the figures:

[0035] Figure 1 schematically shows an example of a laser beam cutting device 100 for cutting a metal workpiece;

[0036] Figure 2 schematically shows another example of the laser beam cutting device 100;

[0037] Figure 3 schematically shows a further example of the laser beam cutting device 100;

[0038] Figure 4 schematically shows an example of the laser beam cutting device 100;

[0039] Figure 5 schematically shows an example of the laser beam cutting device 100;

[0040] Figure 6 schematically shows an example of the laser beam cutting device 100; and

[0041] Figure 7 schematically shows an exemplary method for laser beam cutting.

[0042] Figure 1 schematically shows a side view of an exemplary laser beam cutting device 100 for cutting a metal workpiece 12. In this example, the workpiece 12 is a sheet metal. The device 100 includes a cutting head 102 for directing a laser cutting beam 105 (shown in dashed lines) along a beam axis 105a (shown in dotted lines) onto a process zone 13 of the workpiece 12. In the figures, only the end of the cutting head 102 facing the workpiece, also called the lower end of the cutting head 102, is shown as a partial view of the laser beam cutting device 100. The cutting head 102 has a device 104 for generating a sound pressure directed towards the process zone 13 by means of sound waves 107. The device 104 for generating the sound pressure directed towards the process zone includes an array of several ultrasonic generators T. The nominal frequency of one or more of the ultrasonic generators T may be in the range from 1 kHz to 300 MHz. The power of one or more of the ultrasonic generators T may be in the range of 10 to 200 W. In this example, the ultrasonic generator used was an S7394 shear wave EMAT ultrasonic transducer from ACS Group with a maximum power of 3 MHz. In the present example, the device 104 with the ultrasonic generators is provided at the end of the cutting head 102 facing the workpiece. The device 104 is designed to generate at least one pressure node of the sound pressure that is movable in its spatial position by adjusting the phase and at least one parameter from the group including frequency and signal type of at least one of the ultrasonic generators T. A laser source 103, shown schematically as an example in Figure 2, for generating the laser cutting beam 105 of the laser beam cutting device 100 can be coupled to the cutting head 102 in all examples. The laser source can generate a laser cutting beam with a laser power of at least 1 kW, preferably 2 to 80 kW, more preferably 5 to 40 kW. In this example, the sound pressure is air sound pressure.

[0043] During operation of the laser beam cutting device 100, which is schematically illustrated in Figure 7, the laser cutting beam 105, also called the laser beam 105, is directed along the beam axis 105 onto the process zone 13 of the workpiece in a step S1 . The workpiece 12 is cut. In a step S2, a sound pressure directed towards the process zone 13 is generated by means of the sound waves 107. The sound pressure level can, for example, be 100 to 160 dB. In the present example, the sound waves are introduced into the process zone 13 of the workpiece 12 via a gaseous medium, i.e. air. In a step S3, the array of ultrasonic generators T generates at least one pressure node of the sound pressure that is movable in its spatial position, wherein in a step S4 the phase and at least one parameter from the group including frequency and signal type of at least one of the ultrasonic generators is adjusted. The frequency can be set, for example, in the range from 5 kHz to 100 MHz, preferably 20 kHz to 30 MHz. The phase can be adjusted, for example, in the range from 0° to 180°. The signal type may be selected from sine waves, square waves, triangular waves, sawtooth waves, modulated waves, in particular with amplitude modulation or frequency modulation, or any combination thereof. By adjusting and / or varying at least one of these parameters, the position of the pressure node can be selected and / or changed such that material of the workpiece 12 provided in the process zone 13 and melted by the laser cutting beam 105 is driven out of the process zone by an expulsion force. In this way, the molten material can be removed from the process zone during cutting without the gas pressure of a cutting gas.

[0044] The device 104 for generating the sound pressure directed towards the process zone is designed, for example, to set at least one constructive interference of the sound waves 107 when generating the at least one pressure node movable in its spatial position in the region of the process zone 13, which generates an expulsion force directed towards molten material 14 of the workpiece 12 for expelling the molten material from the process zone. Thus, when generating the at least one pressure node movable in its spatial position in the region of the process zone 13, at least one constructive interference of the sound waves 107 can be set, which generates an expulsion force directed towards molten material of the workpiece for expelling the molten material from the process zone. The position of the at least one movable pressure node and / or a position of the at least one constructive interference can be oscillated and / or specified depending on the cutting direction. In this way, the expulsion force can be increased and generated in a targeted manner.

[0045] The oscillation of the position of the at least one movable pressure node and / or the position of the at least one constructive interference can be effected by varying the frequency and / or phase of the sound waves 107, by rapidly changing the signal type and / or by activating and / or deactivating the individual ultrasonic generators T.

[0046] Figure 2 schematically shows an example of the laser beam cutting device 100, wherein the upper illustration shows a lateral illustration of the cutting head 102 and the lower illustration shows a view of the cutting head 102 from below, i.e. seen from the end of the cutting head facing the workpiece. The ultrasonic generators T of the array span an array surface 104a, which is arranged about the beam axis 105a and is flat. The ultrasonic generators T of the array are arranged such that a central axis M of an angular range, emanating from the ultrasonic generator, of the sound wave generated by the respective ultrasonic generator T is aligned parallel to the beam axis 105a.

[0047] In the present example, the ultrasonic generators T are provided at the lower end of the cutting head 102 at equal distances from one another in the form of a cross that spans the flat array surface 104a. The flat array surface 104a is arranged at a 90° angle to the beam axis 105a. The laser beam 105 passes centrally through the array surface 104a.

[0048] In some examples of the laser beam cutting device 100, at least one of the ultrasonic generators has an adjustment device 109 which is designed to statically and / or dynamically adjust the orientation of the central axis M of the sound wave 107 generated by the respective ultrasonic generator. The adjustment device 109 is shown as an example in Figure 2. The adjustment device 109 has, for example, an angle-adjustable holder that supports the ultrasonic generator and an actuator for adjusting an angle of the central axis M relative to the beam axis 105a. At least one of the ultrasonic generators T and / or at least one of the adjustment devices 109 can be designed to be controllable.

[0049] A control unit 108 of the laser beam cutting device 100 shown as an example in Figure 2, e.g. a central control unit of the device 100, can in all examples be designed to control the array of ultrasonic generators T and can be connected to them in a data-conducting manner. This allows at least one of the ultrasonic generators T of the array to be controlled individually and / or allows several of the ultrasonic generators T to be controlled in at least one defined group. In this way, the strength and orientation of the sound waves and the position of the pressure node(s) can be varied. The adjustment devices of the ultrasonic generators T can further be designed to be controllable in such a way that the orientations of the ultrasonic generators T can be adjusted individually and / or in a coordinated manner. The control unit 108 may include a memory unit and / or a computing unit.

[0050] Figure 3 schematically shows an example in which the ultrasonic generators T have the same or different distances from each other and are arranged in a combined cross shape and in a diamond shape around the laser beam 105. The upper illustration in Figure 3 shows a side view of the cutting head 102 and the lower illustration shows a view of the cutting head 102 from below. In this example, the laser beam cutting device 100 includes a device 110 for measuring ultrasonic pressure. In this example, the device 110 is also provided at the lower end of the cutting head 102 and has at least one sound measuring device 112 with which the ultrasound can be measured. In this example, a piezoelectric force sensor 9215A from Kistler is used to measure the sound pressure. Alternatively or additionally, an ultrasonic microphone FG black from Batlogger, 10 to 150 kHz, is provided for measuring the sound level. The device 110 for measuring the ultrasonic pressure is connected to the control unit 108 in a data-conducting manner. The device 110 can be used for process monitoring and / or for controlling the ultrasonic pressure by adjusting the phase and at least one parameter from the group including frequency and signal type of at least one of the ultrasonic generators T.

[0051] In further examples, the device 110 for measuring the ultrasonic pressure is designed to calibrate the spatial position of the movable pressure node of the sound pressure. In some examples, the ultrasonic pressure measuring device 110 is configured for process monitoring of the spatial position of the movable pressure node of the sound pressure. Calibration can be used to specify target values for a control system to adjust the position of the pressure node. Deviations from the target values can be compensated for by process monitoring. Alternatively or additionally to the sound measuring device 112, an optical measuring device, such as a camera, can be provided for process observation and / or calibration. For example, the melt pool dynamics can be measured using a camera arranged and recording coaxially to the beam axis 105a. With an additional camera mounted on the side, for example, the position of the pressure node can be measured using smoke or the penetration depth into a liquid medium, e.g. in this case the melt of the workpiece material, and used for calibration. The cutting head 102 may also include at least one resonator (not shown) for amplifying or attenuating sound waves. For example, one or more cavities can be provided as a resonator. Figures 4 to 6 schematically show further exemplary arrangements of the ultrasonic generators T of the array, also in the respective upper illustration with a lateral illustration of the cutting head 102 and in the respective lower illustration with a view of the cutting head 102 from below. The arrangement of the ultrasonic generators in Figure 4 differs from that in Figure 3 in that four additional ultrasonic generators T are inserted symmetrically. In the array shown in Figure 5, the ultrasonic generators T span a curved array surface 104a in which the central axes M of the ultrasonic generators T are each aligned at an angle to the beam axis 105a, wherein the angles of immediately adjacent ultrasonic generators differ. Figure 6 shows an arrangement of the ultrasonic generators T, which span different flat partial surfaces of the array surface 104a. The ultrasonic generators T of the same surface are aligned at the same angle to the beam axis 105a. The ultrasonic generators T of different surfaces have different orientation angles to the beam axis 105a.

[0052] The example of the device 100 shown in Figure 6 has a device 120 for introducing an auxiliary gas into the process zone 13. The device 120 has a reservoir 122 for an auxiliary gas. The auxiliary gas is selected, for example, from at least one inert gas, at least one reactive gas, compressed air and a combination thereof. The auxiliary gas can also be used as cutting gas. The reservoir 122 is fluidly connected to the interior of the cutting head 102 by means of a valve 124 that can be controlled by the control unit, wherein the gas pressure can be adjusted. Molten material from the workpiece can also be expelled from the process zone using the auxiliary gas. In this example, the sound pressure is a gas sound pressure. A nozzle 106, shown schematically in Figure 6 as an example, e.g. tapering towards the outlet opening of the cutting head, can be provided in or on the cutting head 102 in all examples. The device 120 for introducing an auxiliary gas into the process zone can also be provided in or on the cutting head 102 in all examples.

[0053] List of reference signs

[0054] 12 Workpiece

[0055] 13 Process zone

[0056] 100 Laser beam cutting device

[0057] 102 Cutting head

[0058] 103 Laser source

[0059] 104 Device for generating a sound pressure directed towards the process zone

[0060] 105 Laser cutting beam

[0061] 105a Beam axis

[0062] 106 Nozzle

[0063] 107 Sound wave

[0064] 108 Control unit

[0065] 109 Adjustment device

[0066] 110 Device for calibrating the spatial position of the pressure node, device for measuring ultrasonic pressure

[0067] 112 Sound measuring device

[0068] 120 Device for introducing an auxiliary gas into the process zone

[0069] 122 Reservoir

[0070] 124 Valve

[0071] M Central axis

[0072] T Ultrasonic generator

Claims

Bystronic Laser AGLawyer file: PAT 451 1 / 035-PCTClaims1 . A laser beam cutting device (100) for cutting metal workpieces, including- a cutting head (102) for directing a laser cutting beam (105) along a beam axis (105a) onto a process zone (13) of a workpiece (12); and- a device (104) for generating a sound pressure directed towards the process zone(13) by means of sound waves (107); characterised in that the device (104) for generating the sound pressure directed towards the process zone has an array of multiple ultrasonic generators (T) and is designed to generate at least one pressure node of the sound pressure, movable in its spatial position, by adjusting the phase and at least one parameter from the group including frequency and signal type of at least one of the ultrasonic generators (T).

2. The laser beam cutting device according to claim 1 , wherein a control unit (108) is provided for controlling the array of ultrasonic generators, wherein the control unit is designed to control at least one of the ultrasonic generators of the array individually and / or a plurality of the ultrasonic generators in at least one defined group, and wherein the device (104) for generating the sound pressure directed towards the process zone is designed to set at least one constructive interference of the sound waves (107) in the region of the process zone (13) when generating the at least one pressure node movable in its spatial position, which generates an expulsion force directed towards molten material (14) of the workpiece (12) for expelling the molten material from the process zone.

3. The laser beam cutting device according to one of the preceding claims, wherein a control unit (108) is provided for controlling the array of ultrasonic generators, wherein the control unit is designed to control at least one of the ultrasonic generators of the array individually and / or a plurality of the ultrasonic generators in at least one defined group, and wherein the device (104) for generating a sound pressure directed towards the process zone is designed to oscillate the position of the at least one movable pressure node and / or a position of the at least one constructive interference and / or to specify it as afunction of the cutting direction.

4. The laser beam cutting device according to one of the preceding claims, wherein the ultrasonic generators of the array span at least one array surface that is arranged at least partially about the beam axis (105a), is flat and / or curved; and / or wherein at least one of the ultrasonic generators of the array is arranged such that a central axis (M) of an angular range, emanating from the ultrasonic generator, of the sound wave generated by the ultrasonic generator is aligned parallel to or at an angle to the beam axis (105a).

5. The laser beam cutting device according to any of claims 1 and 4, wherein a control unit (108) is provided for controlling the array of ultrasonic generators, wherein the control unit is designed to control at least one of the ultrasonic generators of the array individually and / or a plurality of the ultrasonic generators in at least one defined group.

6. The laser beam cutting device according to one of the preceding claims, wherein a device (110) for calibrating the spatial position of the movable pressure node of the sound pressure is provided, which device has at least one element selected from a force sensor, an ultrasonic microphone and an optical measuring device.

7. The laser beam cutting device according to one of the preceding claims, wherein a device is provided for introducing an auxiliary gas into the process zone and for additionally expelling molten material of the workpiece from the process zone by means of the auxiliary gas.

8. A method for laser beam cutting of metal workpieces, in particular with a device according to one of the preceding claims, including- directing a laser cutting beam along a beam axis onto a process zone of a workpiece (S1 ); and- generating a sound pressure directed onto the process zone by means of sound waves (S2); characterised in that an array of multiple ultrasonic generators generates at least one pressure node of the sound pressure that is movable in its spatial position (S3), wherein the phase and at least one parameter from the group including frequency and signal type of at least one of the ultrasonic generators is adjusted (S4).- 15 -9. The method according to claim 8, wherein when generating the at least one pressure node movable in its spatial position in the region of the process zone, at least one constructive interference of the sound waves is set, which generates an expulsion force directed towards molten material of the workpiece for expelling the molten material from the process zone.

10. The method according to one of claims 8 and 9, wherein the position of the at least one movable pressure node and / or a position of the at least one constructive interference are oscillated and / or predetermined depending on the cutting direction.11 . The method according to one of claims 8 to 10, wherein the array of ultrasonic generators generates at least one modulated or modulatable sound wave; and / or wherein the position of the movable pressure node is moved by adjusting at least one parameter from the group including a frequency and a phase position of the at least one sound wave.

12. The method according to one of claims 8 to 11 , wherein a calibration of the spatial position of the movable pressure node of the sound pressure is carried out with at least one element selected from an ultrasonic microphone and an optical measuring device.

13. The method according to one of claims 8 to 12, wherein an auxiliary gas is introduced into the process zone and molten material of the workpiece is additionally expelled from the process zone by means of the auxiliary gas.

14. The method according to one of claims 8 to 13, wherein the auxiliary gas is selected from at least one inert gas, at least one reactive gas, compressed air and a combination thereof; and / or wherein the sound waves are introduced into the process zone of the workpiece via a gaseous medium.

15. A computer program product including one or more program modules, which cause the laser beam cutting device according to one of claims 1 to 7 to carry out the steps of the method according to one of claims 8 to 14, in particular when the program modules are loaded into a memory unit or a computing unit of the laser beam cutting device.

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