Laser processing with scanner light

Abstract

The invention relates to a laser machining head comprising a scanner unit which is arranged in the beam path of the laser machining head and has a scanner mirror which is mounted so as to be pivotable about two axes of rotation. The scanner unit is arranged in the laser processing head such that the laser beam passing through the beam path impinges on the scanner mirror at an angle of incidence of at most 30 DEG, preferably at most 22.5 DEG, more preferably at most 15 DEG, with respect to the surface normal of the scanner mirror. The invention further relates to a scanner unit for such a laser machining head, to a laser machining system comprising a laser machining head, and to a method for laser cutting.

Description

Technical Field

[0001] The present invention relates to the field of laser processing of workpieces, preferably to laser cutting of metal workpieces. In particular, the present invention relates to a laser processing head having a scanner unit for deflecting a laser beam within the laser processing head. Background Art

[0002] For example, WO2019145536A1 discloses a technique for deflecting a laser beam in a laser processing head using a scanner device. Furthermore, systems are known in which a laser beam is deflected in two spatial directions using only one movably mounted mirror. Examples of such single-mirror scanners are described in DE10027148A1 and EP4000789A2.

[0003] When processing materials using laser scanners, increasing laser power imposes fundamental limitations on the movement speed of the beam deflection optics (particularly the scanner mirrors) and process stability, particularly due to the increased thermal load on the optical components. Furthermore, the scanner system's susceptibility to contamination is also critical.

[0004] The present invention is based on the object of improving the prior art. In particular, a scanner arrangement in a laser processing head, in particular a laser cutting head, makes it possible to increase the deflection speed of the laser beam. At the same time, the sensitivity of the sensitive scanner device at high laser powers in the kW and multi-kW range is reduced. Summary of the Invention

[0005] To achieve the object underlying the present invention, according to a first aspect, a laser processing head is provided, comprising a scanner unit arranged in the beam path of the laser processing head and having a scanner mirror that is tiltably supported about at least two rotational axes. The laser processing head is typically part of a laser processing system, wherein the laser beam is focused by the laser processing head and directed onto the workpiece to be processed. During operation of the laser processing head, the laser beam impinging on the scanner mirror can be deflected by a tilting movement. The predefined tilt angle of the scanner mirror about each of the rotational axes can be at most ±2°, preferably at most ±0.3°, relative to a rest position.

[0006] The scanner unit is arranged in the laser processing head such that the laser beam passing through the beam path impinges on the scanner mirror at an angle of incidence of at most 30°, preferably at most 22.5°, and more preferably at most 15° relative to the surface normal of the scanner mirror. The predetermined angle of incidence of the laser beam on the scanner mirror can apply relative to the equilibrium position (or zero position) of the scanner mirror. In other words, if the maximum deflection of the scanner mirror relative to the equilibrium position is 2°, the angle of incidence of the laser beam on the scanner mirror during operation of the laser processing head can be at most 32°, preferably at most 24.5°, and more preferably at most 17°.

[0007] Because the laser beam's angle of incidence on the scanner mirror is reduced, the projection of the laser beam on the scanner mirror can be kept small. Due to the relatively compact beam spot, the scanner mirror can be dimensioned smaller than in systems with larger angles of incidence, which also reduces its mass. The lower the mass of the scanner mirror, the faster it can be accelerated or decelerated, resulting in a more dynamic scanner unit and a higher potential deflection speed for the laser beam.

[0008] According to a preferred embodiment, the laser processing head further comprises a collimator unit designed to collimate the diverging laser beam entering the beam path. The collimator unit can preferably be a collimator lens, which is preferably arranged in the beam path of the laser processing head after the entry point of the diverging laser beam. Downstream of the collimator unit, the laser processing head can have a deflection unit designed to deflect the collimated laser beam onto the scanner mirror so that the collimated laser beam impinges on the scanner mirror at a predetermined angle of incidence. The deflection unit can preferably be a deflection mirror. The deflection mirror can preferably be arranged at a predetermined fixed angle in the beam path of the laser processing head. Downstream of the scanner unit, the laser processing head can further comprise a focusing unit, in particular a focusing lens, designed to receive the laser beam deflected by the scanner unit and focus it onto a target object. In particular, the target object can be a plate-shaped or tubular workpiece, in particular a metal workpiece. For example, the laser beam can be focused onto the surface of the workpiece. The beam entry and beam exit of the beam path in the laser processing head are usually arranged parallel or perpendicular to each other. By arranging a deflection unit in the beam path of the laser processing head, a predetermined angle of incidence on the scanner mirror can be achieved.

[0009] The collimation device can preferably have a collimation focal length of f≦100 mm, preferably f≈70 mm.

[0010] Preferably, the collimation unit can be arranged in the laser processing head so as to be displaceable along the beam path (longitudinally) and / or transversely to the beam path. Alternatively or additionally, the deflection unit can be mounted rotatably or pivotally in the laser processing head. The laser beam can be supplied to the optical component via a fiber optic cable. The interface between the optical cable and the optical component, which can be designed as a plug and socket, can also be arranged displaceably. By adjusting the input interface, collimation unit, and / or deflection unit, the laser beam, in particular the beam centroid of the laser beam, can be precisely aligned with the center of the scanner mirror. This enables the aperture design of the scanner mirror to have narrow tolerances, which has a beneficial effect on the size and, therefore, the quality of the scanner mirror. In particular, the laser beam input interface and / or the collimation unit can be displaceable perpendicularly or transversely to the beam path and / or the deflection unit can be mounted rotatably. The scanner unit can preferably be arranged fixedly within the laser processing head, in particular fixedly on an axis defined by the beam outlet opening of the laser processing head (in particular of the cutting nozzle). Alternatively, the scanner unit can also be arranged to be displaceably and / or rotatably supported in the laser processing head.

[0011] In addition to the aforementioned variations, the laser processing head may also preferably include a widening unit or beam widening unit, in particular a widening lens. The widening lens may preferably be designed as a negative lens. The widening unit may be arranged between the scanner unit and the focusing unit. The widening unit may preferably have a focal length between f = -40 mm and f = -200 mm, in particular a focal length of f ≈ -50 mm. This arrangement with a widening unit or beam widening unit facilitates adjustment to a predetermined imaging ratio while maintaining a relatively small beam diameter upstream of the beam widening unit. A small beam diameter, in turn, facilitates the design of a small scanner mirror aperture. If the laser processing head is designed as a laser cutting head for laser burning or laser melting cutting, for example, an imaging ratio of 1.5 may be desired for the entire optical assembly. When using a collimator unit with a relatively short focal length (e.g. f = 70 mm), this leads to several design conflicts when using a conventional focusing lens (e.g. f = 105 mm) which must also have a correspondingly short focal length. Therefore, the workpiece-side cutting width of the focusing lens assembly, including the widening unit and the subsequent focusing unit, can preferably be designed such that the last optical element has a sufficiently large distance from the cutting nozzle of the laser cutting head.

[0012] The widening unit can be arranged in the laser processing head so that it can be displaced, preferably motorized, along the beam path. This makes it easy to change the focal position of the laser beam. For example, the conversion ratio between the displacements of the widening unit designed as a negative lens can be selected such that a longitudinal displacement of the negative lens by ±5 mm results in a focal position displacement of +10 mm to -30 mm.

[0013] The scanner unit can preferably be suspended in the laser processing head. In other words, during operation of the laser processing head, the reflective surface of the scanner mirror can be at least partially directed downward (in the direction of gravity) in the main processing position. This suspended arrangement of the scanner unit in the laser processing head can reduce the scanner unit's susceptibility to contamination.

[0014] The collimating unit can preferably be designed as a collimating lens. The collimating lens can preferably be arranged upright in the laser processing head. It should be understood that this description relates to a preferred orientation of the laser processing head during operation. An upright or vertical arrangement of the collimating lens is generally less susceptible to contamination than a horizontal arrangement.

[0015] As already mentioned above, the laser processing head can include a connection socket for introducing the laser beam into the beam path of the laser processing head. The connection socket can preferably be arranged horizontally or pointing downward on the laser processing head. Here, the position description also relates to the orientation of the laser processing head in the preferred operating state. A horizontal orientation of the connection socket is particularly preferred, as this has proven in practice to be less susceptible to contamination. Furthermore, the horizontal orientation of the connection socket facilitates the upright arrangement of the collimating lens. Therefore, it can generally be preferred to integrate the scanner unit into the laser processing head with a so-called "delta bend." Here, the connection socket is arranged perpendicular to the exit opening of the laser beam from the laser processing head. After entering via the connection socket, the laser beam is collimated and then deflected twice via the deflection unit (e.g., by 60°) and the scanner unit (e.g., by 30°).

[0016] As also mentioned above, the laser processing head can preferably be designed as a laser cutting head. As a laser cutting head, the laser processing head comprises at least one cutting nozzle and a process gas supply. The laser beam, along with the process gas, is directed through the cutting nozzle onto the object to be processed, in particular a plate-shaped or tubular workpiece, preferably a metal workpiece. The laser beam is movable within the outlet opening of the cutting nozzle by a scanner unit. The range of motion within the outlet opening of the cutting nozzle can be up to 3 mm, preferably up to 2.5 mm, transversely to the longitudinal axis of the nozzle. This small beam deflection can be achieved by very small movements of the scanner mirror. The small mirror movement also limits the elliptical extension of the beam projection on the mirror surface. This in turn keeps the mirror size, and therefore the mirror mass, small, thereby increasing the dynamics or speed of the mirror movement.

[0017] To achieve the objectives underlying the present invention, according to a second aspect, a scanner unit for a laser processing head according to one of the aforementioned variations is provided. The scanner unit includes a scanner mirror. The scanner mirror preferably has a circular or approximately circular cross-section. The scanner unit also includes a drive unit for tilting the scanner mirror about (at least) two rotation axes. These rotation axes are preferably arranged perpendicular to one another.

[0018] The scanner unit also includes an aperture arranged on the reflective side of the scanner mirror that faces the laser beam during operation of the scanner unit. The aperture has a funnel-shaped inner wall, and the inner wall is tilted at an angle of at most 30°, preferably at most 22.5°, and more preferably at most 15° relative to the surface normal of the scanner mirror. The design of the aperture, for example, blocks scattered radiation and limits the projection of the incident laser beam onto the scanner mirror. Furthermore, the drive unit is shielded from the incident laser beam and thus protected. Overall, this provides the prerequisites for keeping the cross-section of the scanner mirror small, thereby reducing its mass, and increasing the speed of the mirror movement.

[0019] The scanner mirror together with the frame and the drive unit can be designed, for example, as described in EP 4 000 789 A2, wherein the magnet pairs of the scanner drive are preferably arranged on the mirror frame.

[0020] The aperture is preferably made of a material with good thermal conductivity, such as a metal or metal alloy. In particular, it can be made of steel. This allows the aperture to additionally dissipate heat that enters the system, for example due to scattered radiation. This protects the scanner mirror frame and the scanner driver from overheating.

[0021] The aperture of the scanner mirror can preferably be 1.2 to 1.8 times larger, preferably 1.5 times larger, than the projection area of ​​the laser beam on the reflective surface. The second-moment method, for example, can be used to determine the projection area. Currently, the aperture of the scanner mirror is typically predetermined by the inner diameter of the mirror frame. The preferred minimum size of the scanner mirror aperture relative to the projection area of ​​the laser beam prevents diffraction effects caused by fringe fields and heating of the mirror frame.

[0022] To ensure freedom of movement of the scanner mirror, the aperture is separated from the surface (reflecting surface) of the scanner mirror by a gap. This gap should preferably be kept as small as possible and, in the neutral or equilibrium position of the scanner mirror, can be, for example, <10 mm, preferably ≤1.5 mm. Minimizing the gap maximizes the shielding effect of the aperture.

[0023] The diaphragm preferably has a smaller diaphragm opening than the aperture of the scanner mirror. This ensures that the mirror frame and the drive unit are shielded even in the event of misaligned incident laser beams. Preferably, the aperture of the scanner mirror and the diaphragm opening can each have a circular contour, with the aperture of the scanner mirror being larger than the smallest inner diameter of the diaphragm opening. The aperture of the scanner mirror can in particular be predetermined by the inner diameter of the mirror frame in which the scanner mirror is mounted.

[0024] The scanner mirror can preferably include a mirror substrate made of a transparent material, in particular quartz glass. This allows the inevitable residual transmission of laser radiation through the scanner mirror when the laser beam impinges on the reflective surface to be directed in a targeted manner to the back of the scanner mirror. This prevents lateral heat dissipation in the direction of the mirror frame and the drive unit. The mirror substrate preferably has a thickness-to-diameter ratio of at most 1:10. This ensures the necessary rigidity of the scanner mirror. For example, the scanner mirror can have a diameter of 25 mm and a thickness of 2.5 mm.

[0025] The scanner mirrors may also have an oxidic interference coating.

[0026] The scanner unit may further comprise a heat removal element arranged on the back side of the scanner mirror, wherein the heat removal element is separated from the back side of the scanner mirror or from the frame structure by a gap that is just large enough to ensure free tilting of the scanner mirror together with the frame structure about the axis of rotation. The gap between the heat removal elements, which may also be referred to as heat sinks or cooling bodies, is preferably at most 3 mm, more preferably at most 1 mm, for example, approximately 0.8 mm. This ensures, on the one hand, that the freedom of movement of the scanner mirror is not affected, and, on the other hand, that heat can be removed from the scanner mirror via the heat removal element by natural or forced convection. The heat removal element preferably comprises a conical section that connects to a cylindrical section, wherein the cylindrical section is arranged in a groove formed by the back side of the scanner mirror and the mirror frame in which the scanner mirror is supported or fastened. The lateral distance between the heat removal element and the mirror frame may preferably be at most 3 mm, more preferably at most 1 mm, for example, approximately 0.8 mm. The heat removal element is preferably made of a material with good thermal conductivity, in particular a metal or a metal alloy. The heat removal element is preferably made of steel. The heat removal element helps to efficiently remove heat from the scanner mirror and, in particular, protects the delicate mirror frame and drive unit (see EP 4 000 789 A2) from damage caused by thermal overload.

[0027] According to another preferred embodiment, the aperture and / or the heat removal element can be actively cooled. For example, the aperture and / or the cooling element can each have one or more cooling channels, through which a cooling fluid can flow. Active cooling can more efficiently remove heat input into the scanner unit due to unwanted radiation, such as scattered light in the beam path, directional reflections from optical interfaces, or process feedback.

[0028] Furthermore, cooling gas can be circulated in the gap between the heat dissipation element and the unit consisting of the scanner mirror and the mirror frame in order to further improve the cooling of these components.

[0029] In order to monitor its operating state, the scanner unit can be monitored contactlessly with the aid of a thermal sensor such as a thermopile. For example, thermal changes on the back side of the scanner mirror or on the frame mechanism or on the suspension of the scanner mirror can be monitored with the aid of the thermopile. When observing the frame mechanism, the part to be observed can preferably be painted black to increase and limit the radiation emission at this part. Alternatively or additionally, in order to monitor the operating state of the scanner unit, a scattered light diode can be arranged in the beam path of the incident laser beam, which monitors the beam path and can very quickly identify incipient contamination on the surface of the scanner mirror. In the case of particle ablation, the measurement level of the scattered light diode rises significantly and in steps. The scattered light diode can preferably be oriented perpendicularly or essentially perpendicularly to the reflective surface of the scanner mirror.

[0030] To achieve the objectives underlying the present invention, according to a third aspect, a laser processing system, in particular a laser cutting system, is provided. The laser processing system comprises at least: a laser beam source for providing a laser beam; and a laser processing head according to one of the aforementioned variations. The laser beam has a power of at least 0.3 kW, in particular several kW (e.g., at least 4 kW or even 10 kW or more). Furthermore, the beam parameter product of the laser beam (upon entry into the laser processing head) is at most 4 mm*mrad, preferably at most 2.5 mm*mrad.

[0031] By using the proposed laser processing head with the proposed scanner unit, the laser processing system according to the invention is particularly suitable for deflecting a high-brightness laser beam in the high-power range.

[0032] Preferably, a solid-state laser is used as the laser beam source, in particular a disk laser or a fiber laser. However, a CO2 laser or a diode laser can also be used.

[0033] The beam quality of the laser beam and the collimation focal length of the collimation unit are preferably selected such that the diameter of the collimated laser beam, and therefore also the diameter of the beam projection on the surface of the scanner mirror, remains small. For example, with a collimation focal length of f≈70 mm, the beam parameter product can be approximately 2.5 mm*mrad.

[0034] In order to achieve the purpose on which the present invention is based, according to a fourth aspect, a method for laser beam cutting is provided, in which method a laser machining beam together with a process gas is directed through a cutting nozzle of a laser cutting head onto the surface of a workpiece to be machined, wherein a secondary movement of the laser beam in the cutting nozzle is superimposed on a main feed movement of the laser cutting head, and wherein, in order to generate the secondary movement in the laser cutting head, the laser beam is directed onto a scanner mirror which is flippable about (at least) two rotation axes, so that the angle of incidence of the laser beam on the scanner mirror is at most 30°, preferably at most 22.5°, more preferably at most 15° relative to the surface normal of the scanner mirror.

[0035] In summary, compared to the systems known so far from the prior art, in particular compared to previous single-mirror scanners, the present invention offers advantages, in particular for laser cutting, with regard to the dynamics, contour accuracy, repeatability, susceptibility to contamination, compactness and thermal tolerance when the laser beam is deflected in the cutting nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The following description of preferred embodiments is used to explain the present invention in more detail with reference to the accompanying drawings.

[0037] In the attached figure:

[0038] Figure 1 shows a schematic perspective view of a laser cutting system for laser beam cutting;

[0039] Figure 2a shows a schematic diagram of a laser cutting head according to the invention according to a first variant;

[0040] Figure 2b shows a schematic diagram of a laser cutting head according to the invention according to a second variant;

[0041] Figure 3a A cross-sectional view showing a scanner unit according to the present invention; and

[0042] Figure 3b Shown as Figure 3a A further cross-sectional view of the scanner unit is shown. DETAILED DESCRIPTION

[0043] Figure 1A laser processing system is shown in the form of a laser cutting system 10. The laser cutting system 10 comprises a laser beam source 12. The laser beam source 12 can be a CO2 laser, a solid-state laser or a diode laser. Although the current diagram shows a CO2 laser configuration in which the generated laser beam L is guided via a deflection mirror to a laser processing head, in this case a laser cutting head 20, a solid-state laser, in particular a disk laser or a fiber laser, can also be preferred as a beam source. In the case of a solid-state laser, the laser beam 20 is usually directed by means of an optical fiber ( Figure 1 ) is transmitted to the laser cutting head 20 and fed into the laser cutting head 20 via the connecting socket.

[0044] The laser cutting system 10 also includes a cutting gas supply 14, here in the form of a gas cylinder 14, through which cutting gas, typically containing nitrogen and / or oxygen, is supplied via a line to a laser processing head 20 and directed, along with the laser beam L, through a cutting nozzle at a predetermined pressure onto a workpiece 30 to be processed—in this case, a plate-shaped workpiece. The workpiece 30 is supported on a workpiece support 20 for processing by the processing beam consisting of the laser beam L and the cutting gas beam. The workpiece 30, preferably a metal workpiece 30, is locally melted by the relative movement between the workpiece 30 and the laser cutting head 20, and the resulting melt is discharged downward, forming a kerf 32 in the workpiece 30. The laser cutting system 10 also includes a control device programmed to move the cutting head 20 relative to the workpiece 30 according to the cutting contour.

[0045] Figure 2aA laser cutting head 20 according to the present invention is schematically shown, which has a beam path in the form of a so-called "Z-bend". The beam path is determined by the optical arrangement within the laser cutting head 20. The laser beam L enters the laser cutting head 20 through an inlet opening 21. Preferably, the inlet opening 21 can be designed as a connection socket for a fiber optic cable, via which the laser beam L is transmitted from the laser beam source to the laser cutting head 20. The divergent laser beam L emitted from the fiber optic cable is collimated by means of a collimating lens 22. The collimated laser beam L is then deflected by a deflection mirror 23 so that the laser beam is directed at a predefined angle of incidence onto a scanner mirror 242 of a scanner unit 24, which is suspended in the laser cutting head 20. The scanner unit 24 is designed to tilt the scanner mirror 242 about two rotation axes relative to the equilibrium position within a relatively small range of movement of up to ±2°, preferably up to ±0.3°. The scanner unit 24 also includes an aperture 246, which is arranged in front of the scanner mirror 242 and shields the sensitive scanner mechanism from unwanted radiation. The laser beam L is deflected at the scanner mirror 242 by an angle α of at most 60°, preferably at most 45°, and more preferably at most 30°, i.e., twice the angle of incidence according to the present invention, and directed onto the outlet opening 28 of the laser cutting head 20. The deflection can vary slightly depending on the tilt position of the scanner mirror 242. On its way to the outlet opening 28, which is preferably designed as a cutting nozzle, the laser beam L is first widened by a negative lens 25 and then focused by a focusing lens 26 toward the outlet opening 28. The laser beam leaves the laser cutting head 20 through this outlet opening together with a cutting gas jet (not shown) and is directed as a cutting beam onto the workpiece to be processed.

[0046] By controlled tilting of the scanner mirror 242, the laser beam L can be deflected very quickly within a predetermined range of motion within the outlet opening 28—that is, within the cutting nozzle—in a plane transverse to the emission direction (here, the xy plane). This means that a relatively small and rapid secondary motion of the laser beam can be superimposed on the main feed motion of the cutting beam during the cutting process. This superimposed secondary oscillating or scanning motion of the laser beam L allows the cutting process to be influenced in a targeted manner, for example, by widening the kerf in certain locations or changing the inclination of the cutting front.

[0047] The plug receiving portion of the plug socket at the inlet opening 21 of the laser cutting head 20 and / or the collimating lens 22 can be displaceable transversely to the beam path (here in the X direction). In addition, the deflection mirror 23 can be rotatably supported and thus have an inclination adjustment. As a result, the laser beam L can be accurately aligned with the center of the scanner mirror 242. The negative lens 25 can be displaceably supported along the beam path (here in the Z direction). By displacing the negative lens 25 in the Z direction, the focus position L of the laser beam can be easily changed. f .

[0048] Figure 2b The laser cutting head 20 according to the present invention is schematically shown. Figure 2a The laser cutting heads 20 of FIG. 1 differ in the arrangement of the optical elements and thus in the course of the beam path. Figure 2b The beam path shown describes the so-called "delta bending". Figure 2a The main difference between the Z-bend and the Z-bend is that the orientation of the inlet opening 21 is perpendicular to (rather than parallel to) the outlet opening 28. The horizontal arrangement of the inlet opening 21 is generally less susceptible to contamination than a vertical arrangement. Due to the horizontal arrangement of the inlet opening 21, the collimating lens 22 is oriented upright in the laser cutting head 20. The upright arrangement of the collimating lens 22 is also less susceptible to contamination because particles are less likely to settle on the lens surface.

[0049] Figure 3a and Figure 3b The scanner unit 24 according to the present invention is shown in each cross-sectional view. The scanner unit 24 comprises a scanner mirror 242, which is laterally supported in a mirror frame 243. The unit consisting of the scanner mirror 242 and the mirror frame is in turn movably supported in the frame 241 via a mechanical suspension. For example, the mirror frame 243 can be suspended by solid joints at four locations evenly distributed on its periphery. The drive unit 244 (here briefly shown in a dotted frame) is designed to flip the mirror frame 243 together with the scanner mirror 242 around at least two rotation axes at a high frequency, and the at least two rotation axes are preferably oriented perpendicular to each other. The scanner mirror 242, the mirror frame 243 and the drive unit 244 can be implemented, for example, as described in EP4000789A2, wherein the magnet pair of the scanner drive can preferably be arranged on the mirror frame 243.

[0050] The scanner unit 24 further comprises an aperture 246 having a funnel-shaped inner wall 245, wherein the maximum inclination angle of the inner wall 245 relative to the surface normal of the scanner mirror 242 (in the equilibrium position of the scanner mirror 242) is 30°, preferably 22.5°, and more preferably 15°. The minimum opening diameter of the aperture 246 on the side facing the scanner mirror 242 is smaller than the aperture of the scanner mirror 242. In this way, the mirror frame 243 and the scanner drive 244 can be effectively shielded by the aperture and protected from unwanted radiation. A heat removal unit 248 in the form of a heat sink 248 is arranged on the back side of the scanner mirror 242. The aperture 246 and the heat sink 248 are connected to each other via the lateral frame 241 of the scanner unit 24. An elastic sealing membrane 245 is arranged between the mirror frame 243 and the lateral frame 241 to protect the drive unit from contamination.

[0051] The aperture 246 and heat sink 248 are each separated from the scanner mirror 242 and mirror frame 243 by a narrow gap to ensure freedom of movement of the scanner mirror and mirror frame during tilting. At the same time, the distance between the aperture 242 and / or heat sink 248 and the scanner mirror 242 and mirror frame 243 is kept as small as possible to ensure efficient heat dissipation. To improve heat dissipation from the scanner mirror 242 and / or mirror frame 243, the aperture 246 and heat sink 248 are preferably made of steel or another material with good thermal conductivity. Furthermore, the aperture 246 and heat sink 248 can be actively cooled. This facilitates natural convection in small air gaps. To this end, the aperture and heat sink can each have one or more cooling channels 247. The cooling channels can be connected to a cooling circuit via a cooling fluid connection 249, in which a liquid or gaseous cooling fluid flows through the cooling channels, dissipating heat from the aperture 246 and / or heat sink 248.

[0052] Reference Signs List

[0053] 10 Laser cutting system

[0054] 12 Laser beam source

[0055] 14 Cutting gas supply

[0056] 16 Workpiece support

[0057] 20 Laser cutting head

[0058] 21 Entrance opening

[0059] 22 Collimating lens

[0060] 23 Deflecting mirror

[0061] 24 Scanner Unit

[0062] 241 Framework

[0063] 242 Scanner Mirror

[0064] 243 Mirror Frame

[0065] 244 drive unit

[0066] 245 Sealing Film

[0067] 246 Aperture

[0068] 2462 Inner wall of the aperture

[0069] 247 cooling channels

[0070] 248 heat removal element

[0071] 249 Cooling fluid connector

[0072] 25 Negative lens 26 Focusing lens

[0073] 28 Exit openings

[0074] 30 workpieces

[0075] 32 Slit

[0076] L laser beam

[0077] L f Focus of the laser beam

[0078] Deflection angle on the α scanner mirror

Claims

1. A laser processing head (20), comprising: a scanner unit (24) which is arranged in the beam path of the laser processing head (20) and has a scanner mirror (242) which is supported so as to be tiltable about two rotation axes; The scanner unit (24) is arranged in the laser processing head (20) so that the laser beam (L) passing through the beam path impinges on the scanner reflector (242) at an incident angle α of at most 30°, preferably at most 22.5°, and more preferably at most 15° relative to the surface normal of the scanner reflector (242).

2. The laser processing head (20) according to claim 1, further comprising: a collimation unit (22), in particular a collimation lens (22), which is designed to collimate a divergent laser beam (L) entering the beam path; a deflection unit (23), in particular a deflection mirror (23), which is designed to deflect a collimated laser beam (L) onto the scanner mirror (242) so that the collimated laser beam (L) impinges on the scanner mirror (242) at a predetermined angle of incidence α; as well as A focusing unit (26), in particular a focusing lens (26), is designed to receive the laser beam (L) deflected by the scanner unit (24) and to focus it onto a target object (30).

3. The laser processing head (20) according to claim 2, in, At least the collimation unit (22) is arranged in the laser processing head (20) in a manner that it can be displaced in a longitudinal direction relative to the beam path and / or in a transverse direction relative to the beam path; and / or The deflection unit (23) is rotatably mounted in the laser processing head (20).

4. The laser processing head (20) according to claim 2 or 3, further comprising: A widening unit (25), in particular a negative lens (25), is arranged between the scanner unit (24) and the focusing unit (26).

5. The laser processing head (20) according to claim 4, in, The widening unit (25) is arranged in the laser processing head (20) in a displaceable manner in a longitudinal direction relative to the beam path.

6. The laser processing head (20) according to any one of the preceding claims, in, The scanner unit (24) is arranged suspended in the laser processing head (20).

7. The laser processing head (20) according to any one of claims 2 to 6, in, The collimating lens (22) is arranged upright in the laser processing head (20).

8. The laser processing head (20) according to any one of the preceding claims, further comprising: a connecting socket, the connecting socket being used to allow the laser beam (L) to enter the beam path of the laser processing head (20); The connecting socket is arranged horizontally or pointing downward on the laser processing head (20).

9. The laser processing head (20) according to any one of the preceding claims, in, The laser processing head (20) is designed as a laser cutting head (20) and comprises at least one cutting nozzle and a process gas supply, wherein the laser beam (L) is directed together with the process gas through the cutting nozzle onto an object (30) to be processed, and wherein the laser beam (L) can be moved in an outlet opening (28) of the cutting nozzle by means of the scanner unit (24), the object being in particular a plate-shaped or tubular workpiece (30), preferably a metal workpiece.

10. A scanner unit (24) for a laser processing head (20) according to any one of the preceding claims, the scanner unit (24) comprising: Scanner reflector (242); A drive unit (244) configured to flip the scanner reflector around two rotation axes; as well as An aperture (246) is arranged on the reflecting side of the scanner reflector (242), wherein the aperture (246) has a funnel-shaped inner wall (2462), and wherein the inclination angle of the inner wall (2462) relative to the surface normal of the scanner reflector (242) is at most 30°, preferably at most 22.5°, and more preferably at most 15°.

11. The scanner unit (24) according to claim 10, in, The diaphragm (246) has a diaphragm opening that is smaller than the aperture of the scanner mirror (242).

12. The scanner unit (24) according to claim 10 or 11, in, The scanner mirror (242) comprises a mirror substrate which is made of a transparent material, in particular quartz glass.

13. The scanner unit (24) according to any one of claims 10 to 12, further comprising: A heat removal element (248) is arranged on the back side of the scanner reflector (242), wherein the heat removal element (248) is separated from the back side of the scanner reflector (242) by a gap, and the gap is just large enough to ensure free tilting of the scanner reflector (242) about the rotation axis.

14. The scanner unit (24) according to any one of claims 10 to 13, in, The aperture (246) and / or the heat removal element (248) can be actively cooled.

15. A laser processing system (10), comprising at least: a laser beam source (12) for providing a laser beam (L); and The laser processing head (20) according to any one of claims 1 to 9; wherein the laser beam (L) has a power of at least 0.3 kW; and Therein, the beam parameter product of the laser beam (L) is at most 4 mm*mrad, preferably at most 2.5 mm*mrad.

16. A method for laser beam cutting, in which a laser machining beam (L) is directed together with a process gas through a cutting nozzle of a laser cutting head (20) onto a surface of a workpiece (30) to be machined, in, A secondary movement of the laser beam (L) in the cutting nozzle is superimposed on the main feed movement of the laser cutting head (20), and In order to generate the secondary movement within the laser cutting head (20), the laser beam (L) is directed onto a scanner mirror (242) that can be flipped around two rotation axes, so that the incident angle of the laser beam (L) on the scanner mirror (242) relative to the surface normal of the scanner mirror (242) is at most 30°, preferably at most 22.5°, and more preferably at most 15°.

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