Device for laser cladding welding with coaxial material feed and distance measuring device

Abstract

Device (10) for laser cladding, comprising: a laser processing head (16) for emitting a laser beam (14); a distance measuring device (34) for measuring a distance by means of a measuring beam (36); a scanning device (50) for deflecting the measuring beam (36); a coupling device (56) for coupling the beam path of the measuring beam (36) into the beam path of the laser beam (14); a feeding device (20) for coaxially feeding a cladding material; a first reflector (26) and a second reflector (28) having a common central axis and arranged between the coupling device (56) and the feeding device (20) in a common beam path of the laser beam (14) and the measuring beam (36);and a control device (60) for controlling the scanning device (50), wherein the control device (60) is configured to control the scanning device (50) to position or move the measuring beam (36) based on a processing direction and / or a processing trajectory, wherein the first reflector (26) is configured to reflect the laser beam (14) and the measuring beam (36) outwards at an angle to the central axis onto the second reflector (28), and wherein the second reflector (28) is configured to reflect the laser beam (14) in the direction of a processing area.

Description

[0001] The present disclosure relates to a device for laser deposition welding in which a deposition material is fed coaxially to the laser beam, with a distance measuring device. Background and state of the art

[0002] Laser cladding is an additive manufacturing process in which a deposit material is melted using laser radiation and bonded to at least one workpiece.

[0003] WO 2018 / 178387 A1 describes a device for additive manufacturing, comprising a laser device, a feeding device for a feed material and an interferometer for measuring a distance to the workpiece by means of an optical measuring beam.

[0004] US 2022 / 0134440 A1 describes an apparatus for additive laser manufacturing, comprising a first reflective optic for receiving and reflecting the laser beam and a second reflective optic for receiving laser light reflected by the first reflective optic. The second reflective optic directs a portion of the received laser light onto the feedstock in a cylindrical configuration, coaxial with a supplied wire or powder feedstock. Summary

[0005] An object of the present invention is to provide a compact design that allows an optical measuring beam for distance measurement to be moved in and around the processing area independently of direction, while minimizing or eliminating the effects of shadowing, particularly on a measurement result. It is particularly desirable to move the optical measuring beam in the pre-travel, post-travel, and / or in the processing area (for in-process observation).

[0006] It is also an object to provide a device for laser deposition welding with coaxial material feed for additive manufacturing processes and a distance measurement, which enables the laser beam (in particular in the focus position) to be uniformly directed towards the supplied material and to melt it uniformly, as well as enabling a distance measurement at a plurality of measuring positions.

[0007] One or more of these objects are achieved by a device for laser metal deposition welding according to the independent claim. Preferred embodiments are the subject of the dependent claims.

[0008] The present disclosure relates to a device for laser cladding, comprising a feed device for coaxially feeding the deposited material, a distance measuring device for measuring a distance using a measuring beam, and a scanning device for deflecting the measuring beam. The feed device can be configured to deliver the deposited material to a feed location coaxially to the central axis or coaxially to the laser beam and / or to feed it coaxially from the feed location to the processing area. A first reflector and a second reflector are arranged on a common central axis of the two reflectors in the common beam path of the laser beam and the measuring beam in order to guide the laser beam and / or the measuring beam around the feed device.In particular, despite the coaxial feeding of the application material, the laser beam and the measuring beam can be irradiated with essentially no shadowing, as they are deflected around the feed location by the first reflector and the second reflector. Even if the feed itself may cause shadowing at one point, this is very minimal due to the positioning in the collimated working beam and can be neglected. The coaxially delivered application material thus represents an obstacle on the common central axis, which is bypassed by the beam path via the first reflector and the second reflector, so that the delivered application material does not cause any shadowing of the laser beam or the measuring beam.

[0009] The invention is based on reflecting the laser beam from the second reflector arranged on the common central axis toward the processing area to ensure uniform melting of the deposited material, while the scanning device allows the measuring beam to be moved in and / or around the processing area independently of direction and essentially without shadowing. The first reflector and the second reflector, as well as the feed device for coaxially feeding the deposited material, achieve a compact design of the laser processing head. In particular, the laser beam can be evenly directed toward the deposited material in the focus position.

[0010] According to one aspect of the invention, a device for laser deposition welding comprises a laser processing head for irradiating a laser beam; a distance measuring device for measuring a distance using a measuring beam; a scanning device for deflecting the measuring beam; a coupling device for coupling the beam path of the measuring beam into the beam path of the laser beam; a feeding device for coaxially feeding a deposition material; and a first reflector and a second reflector, wherein the first reflector is configured to reflect the laser beam and the measuring beam outwardly onto the second reflector at an angle to the central axis, and wherein the second reflector is configured to reflect the laser beam in the direction of a processing area.The first and second reflectors have a common central axis, and / or are arranged on a common central axis, and / or are arranged in a common beam path of the laser beam and the measuring beam. In other words, the first reflector and the second reflector have a common central axis, i.e., the first reflector and the second reflector are arranged in the common beam path such that they have a common central axis. The first and second reflectors can be arranged between the coupling device and the feed device, or upstream of the feed device in the beam propagation direction of the laser beam.

[0011] It is particularly advantageous that the scanning device for deflecting the measuring beam in conjunction with the first reflector and the second reflector makes it possible to measure the distance from a workpiece or an applied layer thickness at at least one defined measuring position, even with changing processing directions or feed speeds of the laser processing head, for example in the lead-up, in the follow-up, and / or in the processing area or at a processing position. Thus, in particular measurements that are defined with regard to a processing direction and / or a processing trajectory (e.g. in the lead-up) are made possible by targeted deflection of the measuring beam by means of the scanning device. In particular, the application of an interferometric measuring method with a 2D scanner with a reflective processing head that deflects the laser beam is made possible.

[0012] According to a further aspect of the invention, a device for laser material deposition comprises a laser processing head for irradiating a laser beam; a feed device for coaxially feeding a deposition material; and a first reflector and a second reflector having a common central axis, wherein the first reflector is configured to reflect the laser beam outwardly onto the second reflector at an angle to the central axis, and wherein the second reflector is configured to reflect the laser beam in the direction of a processing area. The first and second reflectors are arranged on the common central axis and / or coaxially. In other words, the first reflector and the second reflector are arranged in the beam path of the laser beam such that they have a common central axis. The first and second reflectors can be arranged upstream of the feed device in the beam propagation direction of the laser beam.

[0013] The device according to any of these aspects may comprise one or more of the following features: The processing area can refer to an area that includes a processing position (i.e., the position onto which the laser beam is irradiated) and / or its surroundings. In particular, the processing area can refer to an area that includes the processing position, a position or area in the lead-up (i.e., a position to be processed or its surroundings), and / or a position or area in the lead-up (i.e., a position that has already been processed or its surroundings). The arrangement of the first and second reflectors can be configured for a nearly rotationally symmetrical laser and / or measuring beam deflection.

[0014] The device can be a laser metal deposition device, also referred to as an LMD device or LMD system. The device can in particular be a device for laser metal deposition welding with central, coaxial feeding of the deposited material. The device can be a device for laser metal deposition welding of a workpiece. The processing area can be a processing area on a workpiece. The device can in particular be an LMD system with coaxial material feed and rotationally symmetrical or almost rotationally symmetrical beam guidance, comprising a distance measuring device with a variable measuring position. The device can be set up to apply material in several layers, each with predetermined layer thicknesses, along a first direction or axis (so-called vertical direction or axis). The layer thicknesses can therefore be defined in a vertical direction or axis. The vertical direction orAxis can be perpendicular to a workpiece surface.

[0015] The distance can be a height or a vertical distance or a layer thickness, e.g., relative to a reference plane. For example, the distance can be a distance perpendicular to an (unmachined) workpiece surface. The distance measuring device can be configured to determine the height or distance from an optical path length to a measurement position or to a position on a workpiece surface, in particular from an optical path length between a measurement position or a position on a workpiece surface and the distance measuring device.

[0016] The scanning device can be a 2D scanner and / or a galvo scanner with at least one, in particular two, reflective deflection elements, e.g. mirrors.

[0017] The device may further comprise a control device for controlling and / or regulating the device or components of the device, in particular for controlling the scanning device and / or the feeding device and / or a laser source.

[0018] The control device can be configured to deflect or move the measuring beam by means of the scanning device, e.g., along a predefined and / or freely selectable trajectory. In particular, the control device can be configured to control the scanning device depending on a feed rate or a change in the feed rate and / or depending on a processing position or a change in the processing position, in order to deflect or move the measuring beam. In particular, the control device can be configured to adapt a measuring position to the path coordinates of a predetermined processing trajectory for the production of an end product.For example, the control device can control or regulate a measuring beam position and / or a measuring beam movement depending on a feed movement of the device and / or depending on a laser power and / or depending on a material feed quantity and / or depending on a material feed speed.

[0019] The device may further comprise an evaluation device for evaluating data. The evaluation device may be part of a control and evaluation device of the device, which, for example, comprises the aforementioned control device. The distance measuring device may comprise an evaluation unit for determining the distance from the measured data. However, the evaluation unit may also be integrated into the evaluation device.

[0020] In laser cladding, a structure can be built from a deposited material. For example, the structure can be built on a workpiece, or the structure can form the workpiece itself. The buildup can occur layer by layer along a processing trajectory. For example, a wall (wall-shaped structure) can be built up by recurring or repeated deposition along a processing contour, each layer offset in the height direction of the structure.

[0021] The device can be configured or usable for laser deposition welding along a processing trajectory. The welding or deposition direction or processing direction then runs along the processing trajectory. The processing trajectory can also be referred to as a processing path. The terms processing direction or processing trajectory refer to the processing direction (in particular the welding direction) or the processing trajectory of the laser beam relative to the workpiece. The processing trajectory can, in particular, define a processing direction. The processing trajectory can include a corner or curve. The processing trajectory can be defined by a geometry of the workpiece or by a geometry of an end product to be formed in a respective layer or plane.

[0022] The device can be configured to position the processing area relative to the workpiece. The device can comprise a positioning device for positioning the processing area relative to the workpiece. The positioning device can comprise, for example, a robot arm or a gantry and / or an axis system for positioning or moving the laser processing head and / or the workpiece. The positioning device can be configured to position and / or move and / or align the laser processing head and the workpiece relative to one another. The positioning device can be configured to move and / or align the workpiece relative to the device or to the laser processing head.The positioning device can be configured to move and / or align the device or the laser processing head with the distance measuring device, scanning device, coupling device, first reflector, and second reflector arranged thereon and / or carried thereon relative to the workpiece. The positioning device can comprise a robot arm or a gantry to which the laser processing head is attached. The positioning device can comprise an axis system for positioning the workpiece. The positioning device can be configured to move the laser beam along the processing trajectory.

[0023] The laser processing head can, in particular, comprise a housing through which the beam path of the laser beam is guided. The laser beam can also be referred to as a processing laser beam. The laser processing head can be configured to irradiate a laser beam emerging from a laser beam source or an end of a laser guide fiber. The laser processing head can be configured to irradiate the laser beam onto a workpiece. Beam guidance optics can be integrated into the laser processing head.

[0024] The distance measuring device can be a time-of-flight sensor. The measuring beam is an optical measuring beam. The distance measuring device can be an interferometric distance measuring device, e.g., an optical coherence tomography (OCT) distance measuring device. The interferometric distance measuring device can comprise a light source for the measuring beam, a detector for the measuring beam superimposed with light from a reference arm, and / or the reference arm. In other words, the distance measurement can be based on optical coherence tomography. This type of distance measurement is based on the principle of utilizing the coherence of light that has traveled an optical path length with the aid of an interferometer. For this purpose, the optical measuring beam is irradiated onto the processing area or the workpiece. Part of the optical measuring beam is irradiated into a reference arm of the distance measuring device.The portion of the optical measuring beam reflected back from the processing area or the workpiece is superimposed with light from the reference arm and caused to interfere. By evaluating the superimposed light, information can be obtained about the difference in the optical path length between the measuring arm and the reference arm. This makes it possible to obtain information about the distance to the workpiece or about the surface profile of the workpiece. The distance to the workpiece corresponds to a height of the workpiece at the relevant measuring position, e.g. with respect to a reference plane. Thus, by evaluating the superimposed light, information can be obtained about an existing height of the workpiece or about the surface profile of the workpiece, for example information about an existing height of the workpiece at a position where deposition material is to be applied and / or where deposition material has already been applied.Preferably, the distance measuring device is a frequency-domain OCT distance measuring device. This device can measure a distance based on spectral components of the superimposed light. The reference arm can therefore have a constant length (optical path length). The distance measuring device can be stationary relative to the laser processing head. In other words, the scanning device can be configured to deflect the measuring beam relative to the laser beam.

[0025] The distance measuring device can be configured to detect a distance measurement value based on a portion of the measuring beam reflected in the processing area and / or by the workpiece. The distance measuring device can be configured: to detect at least one distance measurement value of a distance between the laser processing head radiating the laser beam and the workpiece, in particular a distance to a measuring position on the workpiece (i.e., the distance to the workpiece at the measuring position), and / or to detect at least one distance measurement value along a scan figure of the measuring position or of the measuring beam based on a portion of the measuring beam reflected in the processing area and / or by the workpiece and / or to detect surface profile data of a surface of the workpiece, in particular surface profile data along a scan figure of the measuring position or of the measuring beam.The distance can be determined from the at least one distance measurement value. The scan pattern can also be referred to as a scan pattern, scanning pattern, scanning path, or trajectory of the measuring position on the workpiece. The measuring position(s) or the scan pattern can be determined relative to a machining position and with respect to a machining direction and / or a machining trajectory.

[0026] The scanning device can be a scanner optics or scanning optics. The scanning device can be configured to deflect the measuring beam over or within a scanning area, e.g., on the workpiece. The scanning device can comprise at least one movable deflection element for the measuring beam, in particular at least one movable mirror (scanning mirror). The deflection element or the scanning mirror is rotatable about at least one axis. The scanning device can comprise one movable mirror or two movable mirrors (scanning mirrors) for deflecting the measuring beam. The first movable mirror can be rotatable about a first axis of rotation, and the second movable mirror can be rotatable about a second axis of rotation, the first axis of rotation and the second axis of rotation being at an angle to one another, e.g., at an angle between 45° and 135°, in particular of approximately 75° or 90°.Alternatively, the scanning device can have a movable mirror that is rotatable or pivotable about at least two axes. To move the mirror or the first and second mirrors, the scanning device can accordingly comprise at least one galvanometer drive. Accordingly, the mirror or the first and second mirrors can be designed as galvanometer mirrors, or galvo mirrors for short. Accordingly, the scanning device can be designed as a galvanometer or galvo scanner, in particular as an XY galvo scanning system. Alternatively, the scanning device can have MEMS-based, piezoelectric and / or inductive drives. The scanning device can also be designed as a prism scanner or lens scanner. The scanning mirror can also be referred to as a scanning mirror.

[0027] The scanning device can be arranged between the distance measuring device and the arrangement comprising the first and second reflector, in particular between the distance measuring device and the coupling device. The coupling device can be arranged in the beam path of the measuring beam after the scanning device, i.e. the scanning device can be arranged between the distance measuring device and the coupling device. In the case of an interferometric distance measuring device, the scanning device can be arranged in a measuring arm. The scanning device can be arranged in the beam path of the measuring beam between a light source for the measuring beam and the coupling device. The scanning device can be a 2D scanning device. The scanning device can be configured to deflect the measuring beam in a first direction and in a second direction transverse to the first direction. The first and second directions can be orthogonal to one another.The scanning device can be configured to deflect the measuring beam from a zero position. The zero position can refer to a non-deflected orientation of the measuring beam, in which the measuring beam runs coaxially with an optical axis of the laser beam path.

[0028] The scanning device can be configured to deflect the measuring beam independently of the laser beam. The scanning device allows the measuring beam to be deflected and to be directed onto the processing area or the workpiece at a measuring position or along a scanning pattern. In particular, the scanning device can be configured to deflect the measuring beam in the beam path of the measuring beam to the processing area before coupling the measuring beam into the beam path of the laser beam. The measuring beam can thus be positioned relative to the processing position on the workpiece and can, in particular, be freely positioned on the workpiece within a scanning range of the scanning device. The scanning range can also be referred to as the deflection range or scanning range.

[0029] The scanning device can be configured to return light of the measuring beam, which is coupled out by the coupling device and reflected from the processing area or from the workpiece, to the distance measuring device. In particular, the light path of the measuring beam through the scanning device can be the same in both directions, i.e., the light path of the measuring beam reflected from the input device and the light path of the measuring beam returning to the distance measuring device (at any time or for a given working position or deflection position of the scanning device).

[0030] The distance measuring device and the scanning device can together form a distance measuring device with a variable measuring position, in particular an OCT distance measuring device with a variable measuring position.

[0031] The distance measuring device and / or the scanning device can be configured to adjust the focus position of the measuring beam, preferably independently of the focus position of the laser beam. In particular, the distance measuring device and / or the scanning device can be configured to focus the measuring beam onto the workpiece, in particular onto a surface of the workpiece.

[0032] The scanning device can be configured to adjust and / or modify a propagation direction and / or a propagation of the measuring beam. Such adjustment of the propagation makes it possible to place the measuring beam on the first and second reflector such that it is directed from the correct direction onto the interaction zone and at the correct offset therefrom. In particular, the scanning device can be configured to adjust and / or modify an offset of the measuring beam from the optical axis of the scanning device, an inclination of the measuring beam from the optical axis, and / or a beam diameter of the measuring beam. For this purpose, the scanning device can comprise the at least one mirror and, if appropriate, further optical elements. The scanning device can comprise, for example, collimating optics (e.g., at least one collimating lens) for collimating the measuring beam, and / or focusing optics.Offsetting and / or tilting the measuring beam relative to the optical axis can make it possible to observe specific positions around the focal point (i.e., to perform the distance measurement there). A more pronounced beam propagation and a clear assignment of the measuring beam position and / or measuring beam movement to the feed direction and / or feed speed (processing direction and / or processing speed) can contribute to the unambiguous measurement result of the distance measurement. The scanning device and / or the control device for controlling the scanning device can be configured to place the measuring beam on the first and / or second reflector at positions with a respective clear reflection direction. This can prevent interference peaks that could result in an ambiguous measurement.In particular, the scanning device and / or a control device for controlling the scanning device can be configured to exclude a central point of the first reflector (e.g. a reflector tip) as the position of the measuring beam.

[0033] The coupling device is arranged downstream of the scanning device in the beam path of the measuring beam. This means that the coupling device is arranged downstream of the scanning device in the beam path of the measuring beam in the direction of the processing area. In other words, the scanning device is arranged between the distance measuring device and the coupling device. Thus, the coupling device is configured to couple the measuring beam (e.g. emitted by a light source of the measuring beam) into the beam path of the laser beam after it has passed through the scanning device in the direction of the processing area. Coupling the beam path of the measuring beam into the beam path of the laser beam can comprise coupling the measuring beam in the direction of the workpiece into the beam path of the laser beam and / or coupling out light of the measuring beam reflected (by the workpiece) from the beam path of the laser beam passed through in the return direction.The coupling device can comprise a beam splitter, for example, a dichroic mirror. The coupling device can be referred to as a coupler or beam coupler. The coupling device can be configured to couple the beam path of the measuring beam (or its optical axis) parallel to the optical axis of the beam path of the laser beam. The measuring beam or its optical axis can thus be guided parallel to the laser beam, in particular via the first reflector and / or the second reflector.

[0034] The feed device is configured to feed the application material coaxially, i.e. coaxially to the central axis (common central axis of the first reflector and the second reflector) or coaxially to the beam path of the laser beam (in front of the reflectors). The feed device can be configured to feed the application material coaxially and / or centrally, i.e. centrally to the central axis or to the beam path of the laser beam. The feed device can be configured to deliver the application material at a feed location coaxially to the central axis (common central axis of the first reflector and the second reflector) or coaxially to the beam path of the laser beam (i.e. in a direction coaxial to the central axis or to the beam path of the laser beam). The feed device can be configured to feed the application material from the feed location to the processing area coaxially to the central axis. The feed device can have a discharge opening for the application material at the feed location.

[0035] The processing area can be located on the central axis of the first and second reflectors in the beam path of the laser beam behind the first reflector and / or behind the feed location.

[0036] The first reflector and the second reflector are arranged such that they have a common central axis. The arrangement of the first and second reflectors can be arranged between the coupling device and the delivery device. The common beam path of the laser beam and the measuring beam can be defined or extend between the coupling device and the delivery device.

[0037] By means of the first and second reflectors arranged on a common central axis, a compact structure for beam shaping of the laser beam can be achieved, in which structure the laser beam can be directed towards the deposited material from several sides, in particular in a ring shape. The first reflector and the second reflector each represent an optical deflection element. The first reflector can be configured to reflect the laser beam outwards (i.e., relative to the central axis or the axis of the beam path of the laser beam). The first reflector prevents the measuring beam from being irradiated along or parallel to the optical axis of the laser beam onto the processing area or the workpiece. The common central axis of the first reflector and the second reflector can be coaxial to the beam path of the laser beam or to the axis of the laser beam incident on the first reflector.The first reflector can be configured to reflect the laser beam outward from a path along the optical axis and / or parallel to the optical axis. The first reflector can be configured to reflect the laser beam and the measurement beam outward onto the second reflector at an angle to the central axis.

[0038] The second reflector can be arranged concentrically to the first reflector. In other words, the central axis of the first reflector and the central axis of the second reflector run coaxially and are referred to as the common central axis. The second reflector can be configured to reflect the laser beam in the direction of the processing area rotationally symmetrically or concentrically to the central axis or the optical axis of the laser beam, for example into a cylindrical or cylinder-shell-shaped beam configuration or a conically converging or cone-shell-shaped beam configuration. The second reflector can be configured to reflect the laser beam from multiple circumferential directions concentrically toward the processing area or concentrically toward the deposition material fed and / or dispensed by the feed device.

[0039] The first reflector is configured to reflect the laser beam and the measuring beam outwards onto the second reflector at an angle to the central axis. "Central axis" can here refer in particular to the central axis of the first and / or the second reflector. The central axis can run coaxially to the beam path of the laser beam, in particular to the beam path of the laser beam in front of the first and / or second reflector in the beam propagation direction. The angle with respect to the central axis can be greater than 90°, for example, so that reflection outwards in the backward direction occurs. The second reflector can be arranged above the first reflector and / or at the same height as the first reflector with respect to the beam path of the laser beam to the processing area. This enables a particularly compact design. The first reflector can accordingly be configured to reflect the laser beam and the measuring beam opposite to the direction of incidence.

[0040] The second reflector can be configured to reflect the laser beam parallel to the central axis or at an angle to the central axis in the direction of the processing area. The second reflector can be configured to reflect the laser beam concentrically and / or from multiple sides in the direction of the processing area. This allows the laser beam to be directed particularly evenly to the applied deposit material in the focal position. By evenly directing the laser beam to the deposit material, particularly in the focal position of the laser beam, a particularly uniform melting of the deposit material can be achieved.

[0041] The arrangement comprising the first and second reflector can be configured to deflect the laser beam rotationally symmetrically to the axis of the laser beam incident on the first reflector. The deflected laser beam can have an annular cross-section, i.e. a cross-section in the center of which the laser beam has an intensity of approximately zero. The deflected measuring beam can have a circular or ellipsoidal cross-section, i.e. a circular or ellipsoidal cross-section in the center of which the measuring beam has an intensity maximum and / or within which the measuring beam consistently has an intensity greater than zero. The first reflector and / or the second reflector can have at least one reflective surface, in particular at least one reflective, metallic surface.The first reflector and the second reflector can together form a beam-shaping optic configured to generate an annular beam profile (or annular beam configuration) of the laser beam. For example, the feed location of the deposition material and / or the discharge opening for the deposition material can be surrounded by the annular beam profile of the laser beam. The beam profile of the laser beam can, for example, be cylindrical and / or conical, converging after the second reflector.

[0042] The laser beam and the measuring beam can run parallel in the common beam path. The laser beam and the measuring beam can run parallel and / or coaxially in the common beam path, at least in the zero position of the measuring beam. In particular, the coupling device can be configured to couple the measuring beam into the beam path of the laser beam parallel and / or coaxially to the laser beam.

[0043] The processing area can also be referred to as an interaction zone. In the processing area, an interaction can occur between the workpiece, the deposition material, and the laser beam. The deposition material can be applied to the workpiece, resulting in the deposition material being welded to the workpiece. The energy of the laser beam can melt the deposition material and / or the material of the workpiece. The first and second reflectors can be configured to guide the laser beam evenly to the applied deposition material in the focus position.

[0044] The laser processing head can be configured to irradiate a laser beam emerging from a laser (light) source or an end of a laser guide fiber onto the processing area or the workpiece. The laser processing head can be configured to feed the laser beam to the coupling device or the first reflector with a circular or ellipsoidal beam cross-section and / or a (transverse) beam profile in which a main intensity range encompasses the optical axis (of the laser beam). For example, a maximum or a plateau of the beam intensity can be present on the optical axis. For example, the laser processing head can be configured to irradiate the laser beam with a Gaussian beam profile of the

[0045] The device may further comprise a collimation device for collimating the laser beam. The collimation device for the laser beam may be arranged upstream of the coupling device in the beam propagation direction of the laser beam. The collimation device for the laser beam, or a part thereof, may be adjustable along an optical axis of the collimation device and / or along a beam propagation direction of the laser beam in order to adjust a focus position of the laser beam.

[0046] The device may further comprise a laser source for generating the laser beam or be configured to couple the laser beam from a laser source for generating the laser beam into the laser processing head, e.g., through a fiber coupler. The laser source may also be referred to as a laser for short. The laser may be configured as a single-mode laser, a multi-mode laser, a solid-state laser, and / or a fiber laser. The device may comprise an optical fiber for guiding the laser beam from the laser source to the laser processing head. The device may further comprise an interface for transmitting data to an external system.

[0047] The device for laser cladding can be configured to focus the laser beam into the processing area, for example, into a focal plane, e.g., into a focal point or an annular focus. Accordingly, the device can comprise focusing optics for focusing the laser beam and / or the measuring beam. The focusing optics can be or comprise a lens, a focusing lens, a converging lens, a lens group, a telecentric lens, or an f-theta lens, in particular a telecentric f-theta lens. The f-theta lens is preferably designed for both the wavelengths of the measuring beam and those of the laser beam. The focusing optics can be arranged downstream of the second reflector in the beam path of the laser beam. The focusing optics can comprise two or more lenses, the distances from one another of which can be at least partially varied in order to adjust or change the focus position.

[0048] The focusing optics can be arranged on the common central axis to focus the laser beam and / or the measuring beam. The second reflector can be configured to reflect the laser beam and / or the measuring beam through the focusing optics at an angle to the central axis onto the processing area. Accordingly, the focusing optics can be configured to direct the laser beam reflected by the second reflector onto the focusing optics at an angle to the central axis onto the processing area. The focusing optics can, in particular, comprise or be a focusing lens. For example, the second reflector can be configured to reflect the laser beam as a parallel beam.

[0049] The second reflector can be configured to direct the laser beam onto the processing area directly or via at least one additional optical element at an angle to the central axis. The at least one additional optical element can be the focusing optics.

[0050] The second reflector can be configured to focus the laser beam and / or the measuring beam, in particular to focus it with respect to a processing point and / or to focus it into the processing area. The second reflector can be, for example, a (parabolic) focusing mirror. The second reflector can, for example, be a ring segment of a parabolic mirror or have reflective surfaces in the form of segments of a paraboloid of revolution.

[0051] The control device for controlling the scanning device can be configured to control the scanning device for positioning or moving the measuring beam based on a processing direction and / or a processing trajectory (in particular based on a processing direction and / or a processing trajectory of the device or the laser processing head). Thus, a measuring position and / or a scanning figure can be adjusted and / or aligned based on a processing direction and / or a processing trajectory. The control device can be configured to control the scanning device for positioning or moving the measuring beam along the processing trajectory with or without the superimposition of a scanning figure or an oscillating movement. The measuring beam can thus be positioned in the lead-up or lag-up, for example, adapted to the current processing direction or the processing trajectory.For example, if machining is performed in the X-direction, the measuring beam can be positioned in the X-direction during the pre-travel or post-travel phase. If the machining direction then changes and now occurs in the Y-direction, the measuring beam can be immediately positioned in the Y-direction during the pre-travel or post-travel phase by controlling the scanning device.

[0052] In particular, the control device can be configured to control the scanning device for positioning or moving the measuring beam based on a machining direction and / or machining trajectory and a current machining position. The control device can, for example, be configured to position the measuring beam on the machining trajectory with an offset corresponding to a predetermined temporal offset (in particular according to a machining speed along the machining trajectory) or with an offset corresponding to a predetermined distance along the machining trajectory, relative to the current machining position. The offset can, for example, be 0 mm to 10 mm, in particular 0 mm to 5 mm, 0 mm to 2 mm, or 2 mm to 5 mm.

[0053] The distance measuring device can be configured to measure a distance at a measuring position in the lead-in, in the processing area (or at the processing point), and / or in the follow-up, in particular based on a processing direction and / or a processing trajectory. The control device can be configured to position (in particular move) the measuring beam based on a processing direction and / or a processing trajectory. The control device can be configured to position (in particular move) the measuring beam in the lead-in, in the processing area (or at the processing point), and / or in the follow-up (to the current processing position), in particular based on a processing direction and / or a processing trajectory.For example, a measurement of the distance in the lead-up or lag-up can be performed on the machining trajectory even if the machining trajectory includes a curve or corner between the measurement position and the current machining position. The respective positioning can be superimposed by a scan pattern or an oscillating movement. The scan pattern can include an oscillating movement. Controlling the movement of the measuring beam can include controlling the variable positioning of the measuring beam. The movement of the measuring beam can occur along or on a scan path. The scan path can, in particular, include a scan pattern.

[0054] The control device can be configured to control the scanning device to move the measuring beam according to a predetermined scanning pattern or an oscillating movement. The scanning pattern can comprise an oscillating movement. The control device can be configured to position and / or align the scanning pattern based on a processing direction and / or a processing trajectory (of the laser processing head). The control device can be configured to position the scanning pattern at a predetermined measuring position and / or to align it at the measuring position based on a processing direction and / or a processing trajectory. The scanning pattern can be positioned accordingly on the processing trajectory, wherein the positioning can occur depending on a processing direction and / or in advance or after the processing position. The positioning occurs with respect to the processing position.For example, the scan figure can be positioned at a position and with an orientation depending on the machining trajectory. The scan figure can be formed, for example, as a line or an arc, in particular as a line or arc perpendicular to or at an angle to the machining trajectory. The scan figure can intersect the machining trajectory, in particular intersect it at right angles.

[0055] The control device can be configured to control the scanning device to adjust and / or modify an offset of the measuring beam from the processing position, an inclination of the measuring beam to the optical axis of the device or the focusing optics, and / or a beam diameter of the measuring beam. The measuring beam can thus be offset and / or directed at an angle, for example. The optical axis of the scanning device is the optical axis of the beam path of the measuring beam on the side of the scanning device at which the measuring beam enters the scanning device from the distance measuring device. It can correspond to the optical axis of the beam path of the laser beam at the coupling device and / or correspond to the zero position of the deflection of the measuring beam. The measuring beam can deviate from the zero position at any time, in particular deviate on one side.

[0056] The device can comprise a memory for calibration data, in particular for calibration data that takes into account an optical distortion and / or reference height data of a beam path of the measuring beam via the first reflector and / or the second reflector and / or the at least one optical element, in particular these or other calibration data depending on the position of the measuring beam, the deflection of the measuring beam by the scanning device, and / or the orientation of the beam deflection and / or the orientation of the coupling device and / or the orientation or arrangement of the scanning device. The calibration data can comprise reference height data and / or data from an XY calibration. In other words, calibration data from an XY calibration or a calibration of the XY plane or reference plane can ensure that positions on the workpiece are correctly mapped, i.e., that measuring positions can be correctly set.In addition, this coordinate system can be supplemented with the reference height data (in the Z direction). The control device can be configured to control the scanning device to position or move the measuring beam based on the calibration data stored in the memory. By correcting the optical distortion of the position on the work plane or workpiece surface, it can be ensured that measurements are taken at the correct location. This is because the correct height value, i.e. the measured value at the correct position, in relation to a reference plane is required to control the material feed. The control device can be configured to control the scanning device to position or move the measuring beam based on the calibration data stored in the memory, in particular on the XY calibration data, and / or based on the machining direction (welding direction) and / or a machining trajectory or scan figure.In particular, the relationship between the position of the measuring beam or the orientation of the beam deflection (scanner and other elements) can be correlated with the welding direction, i.e. the position of the measuring beam or the orientation of the beam deflection by the scanning device can be controlled depending on the machining direction. The reference height data can, for example, vary (i.e., comprise different values) depending on the deflection of the measuring beam by the scanning device, in particular depending on an offset and / or an orientation of the deflection of the measuring beam. This means that the reference height data can include or be optical path lengths to the respective measuring positions with respect to a reference plane, so that a path length change due to the scanning position or measuring position can be taken into account.The evaluation based on the reference height data thus makes it possible to take into account a change in the optical path length of the measuring beam when the position of the measuring beam changes. If, for example, a change in the deflection of the measuring beam results in a different path of the measuring beam across the first and second reflector, which has a different optical path length, the reference height data can enable a correspondingly adjusted distance measurement. Thus, in particular, the measuring beam can be positioned or moved at a measuring position according to a measuring position and / or a predetermined scanning pattern of the measuring beam, whereby an optical distortion and / or a varying optical path length of the beam path of the measuring beam can be compensated.In particular, in each of the positioning or movement of the measuring beam described in the present disclosure, the control device may be configured to control the scanning device for positioning or moving the measuring beam based also on the calibration data stored in the memory.

[0057] The deposit material may be a deposit material in the form of a wire, a powder-filled wire, or a powder. The deposit material may comprise at least one metal. The deposit material may also be referred to as a feed material. The feed device may comprise a wire guide. The deposit material may comprise an alloy and / or materials for forming an alloy, in particular materials for forming an alloy during laser deposition welding of the deposit material.

[0058] The laser processing head can be a deposition material application head, in particular a powder application head and / or a wire application head. The laser processing head can comprise the feed device. The laser processing head can comprise the first reflector and the second reflector.

[0059] The device can be used, for example, for the following applications: Laser cladding can include: layering of deposition material, creating a homogeneous connection between workpieces, applying deposition material in the form of a powder-filled wire or a wire alloy, coating a turbine blade, or producing a part (workpiece). For example, the workpiece can be or comprise a turbine blade, and laser cladding can include: coating the turbine blade with the deposition material, for example, for coating with an alloy. An alloy can be created, for example, by applying a deposition material in the form of a powder-filled wire or a wire alloy.A powder-filled wire may, for example, comprise a first material as the wire and a second material as the powder filling of the wire, so that an alloy of the first material and the second material can be formed during laser cladding.

[0060] The first reflector can be substantially conical and / or pyramid-shaped, and / or the first reflector can have at least one reflective surface with continuous or discrete rotational symmetry with respect to the common central axis. The first reflector can accordingly be configured to reflect the laser beam rotationally symmetrically with respect to the central axis. Rotational symmetric here can comprise continuously rotationally symmetrical (i.e., rotationally symmetrical to every angle) or discretely rotationally symmetrical (i.e., flat surfaces for specific, evenly distributed angular ranges, e.g., pyramids with equilateral bases). The discrete rotational symmetry can be at least threefold discrete rotational symmetry. The first reflector can be configured to deflect the laser beam rotationally symmetrically, substantially rotationally symmetrically, or nearly rotationally symmetrically.The first reflector can be configured to reflect the incident laser beam in an annular beam configuration (in an annular beam profile), in particular to reflect it in an annularly widening beam configuration. In other words, the laser beam has an annular beam configuration (an annular beam profile) after reflection at the first reflector. The first reflector can be configured, in particular, to generate an annular beam profile of the laser beam by reflecting the laser beam. The first reflector can have the shape of a cone or a regular pyramid. The annular beam configuration or the annular beam profile can be continuously rotationally symmetrical or discretely rotationally symmetrical. Accordingly, the annular beam configuration orThe annular beam profile can be continuously annular or annular with several separate and / or spaced segments, in particular at least three segments. The first reflector can have a reflective conical surface. The beam profile can be segmented annular, for example if the first reflector is not in the shape of a round cone, but rather in the shape of a pyramidal cone (pyramid). The first reflector can be configured to split the laser beam evenly in directions radial to the central axis or the optical axis of the beam path. The first reflector can be arranged in the center of the second reflector.

[0061] The second reflector can have at least one reflective surface with continuous or discrete rotational symmetry with respect to the common central axis. This allows the laser beam to be guided particularly evenly to the supplied application material in the focus position. The second reflector can be designed to reflect the laser beam reflected by the first reflector in an annular beam configuration (or with an annular beam profile). The second reflector can be designed to reflect the laser beam reflected by the first reflector rotationally symmetrically with respect to the central axis. Rotationally symmetrical here can mean continuously rotationally symmetrical (i.e. rotationally symmetrical to every angle) or discretely rotationally symmetrical (i.e. flat surfaces for certain evenly distributed angular ranges, e.g. pyramids with equilateral bases, orrotationally symmetrical for certain rotation angles, in particular sub-divisions of 360°). The discrete rotational symmetry can be at least threefold discrete rotational symmetry. The second reflector can be configured to deflect the laser beam rotationally symmetrically, substantially rotationally symmetrically, or nearly rotationally symmetrically. The annular beam configuration or the annular beam profile can be continuously annular or annular with a plurality of separate and / or spaced segments, in particular at least three segments.

[0062] The second reflector can be annular and / or have a circular recess concentric to the central axis surrounding a reflective surface, and / or the second reflector can be a ring segment of a parabolic mirror. This allows the laser beam to be guided particularly evenly to the supplied deposition material in the focus position. The second reflector can have a reflective surface in the form of an annular segment of a paraboloid of revolution. The second reflector can have reflective surfaces in the form of segments of a paraboloid of revolution. The second reflector can be arranged concentrically to the first reflector and / or radially outside the first reflector. The second reflector can form a ring or have several separate segments or parts.The second reflector may be straight in a radial cross-section (radial with respect to the central axis) or may have a curvature, in particular a concave curvature.

[0063] The first reflector and / or the second reflector can be configured to deflect the laser beam rotationally symmetrically, substantially rotationally symmetrically, or nearly rotationally symmetrically. This allows the laser beam to be directed particularly evenly toward the applied coating material in the focal position.

[0064] The first reflector and / or the second reflector may have a metallic surface. In particular, the first reflector and / or the second reflector may be made of metal.

[0065] The laser beam may be annular after exiting the laser processing head, and / or the measuring beam may be circular after exiting the laser processing head or move along a circular scanning path. In particular, the laser beam may have an annular beam profile after exiting the laser processing head.

[0066] The device can comprise an evaluation device for determining a surface geometry from distances measured by the distance measuring device, e.g. height values. The surface geometry can in particular be a surface geometry along a scan figure or a scan path. In particular, a surface geometry of a previous material application can be determined. The surface geometry can comprise a height profile, in particular a height profile along the scan figure or the scan path, and / or a height or depth of a workpiece at a measuring position on a processing trajectory, and / or a height or depth of an applied application material at a measuring position on a processing trajectory. The evaluation device can be configured to determine the surface geometry in the pre-run, in the processing area, and / or in the post-run.For example, a distance measurement can be performed in the melt, for example, close to the center axis or the machining point. The surface geometry can be determined from a point measurement and / or from distance measurements along a scan figure or scan path.

[0067] The evaluation device can be configured to determine a height based on a surface geometry. For example, a mean value of a bead profile (height profile of a weld bead) can be determined as the height, or a maximum value of a bead profile can be determined as the height. The evaluation device can be configured to detect a deposition edge (of the previously applied deposition material). Based on the surface geometry in the pre- or post-processing phase, it can be detected whether a previous material application was too high or too low. For example, a deposition edge can be monitored. A product to be produced (the workpiece) can be monitored.

[0068] The device may comprise a job control device for controlling and / or regulating the material feed by the feed device. The job control device may be integrated into the control device or into the control and evaluation device. The job control device may be configured to control or regulate the material feed or material application as a function of a laser power of the laser beam and / or a distance measured by the distance measuring device and / or a specific surface geometry.to regulate, in particular depending on a distance measured by the distance measuring device and / or a surface geometry at a surface position or measuring position that corresponds to the current processing area, and / or in particular depending on distance measured values ​​measured by the distance measuring device at a measuring position in the lead-up, in the processing area and / or in the follow-up and / or based on the surface geometry determined by the evaluation device. The distance, the distance measured values ​​or the distances can in particular be a distance, distance measured values ​​or distances that were measured at a measuring position in the lead-up, in the processing area and / or in the follow-up that corresponds to the current processing area or processing point. Regulation is understood to mean control with feedback, e.g.when measuring distance in the machining area or in the lead-up to a same machining pass or when measuring distance in the machining area or in the lead-up to a previous machining pass.

[0069] The job control device can be configured to control and / or regulate the material feed through the feed device as a function of a surface geometry determined by the evaluation device. The job control device can, for example, be configured to compensate for any deviations of a surface geometry from a target height (i.e. a layer thickness to be applied) on the processing trajectory. Based on a measurement of the existing height or depth in the pre-run, the material feed can be regulated directly at the current processing point, with or without a time offset. The job control device can, in particular, comprise a PI (proportional-integral) controller, in particular a PI controller with a time offset. In laser deposition welding, corner points or threshold points in particular are susceptible to too much material deposition, too little material deposition, or too great or too low a height.For example, bumps or other unevenness in an applied material structure can be compensated for in the next processing pass at the corresponding point along the processing trajectory. The distance measurement can be performed either before the current processing pass or after the previous processing pass. Errors such as deviations from a target height, such as unevenness in a bead and / or deviations from a target height caused by capillary forces, can thus be corrected. When applying the material layer by layer, a particularly high level of uniformity in the application height can be achieved, and / or an accumulation of errors can be avoided.

[0070] The control and / or regulation of the material supply can comprise a control and / or regulation of an amount of application material supplied to the processing area, an application material flow and / or a height of a material structure applied in the processing area.

[0071] The application control device can be configured to control a power of the irradiated laser beam (i.e., the laser power). The application control device can be configured to control the power of the irradiated laser beam as a function of or together with the material feed. The application control device can therefore be configured to control a power of the laser beam and / or to control the material feed and / or to control the feed device to control and / or regulate the material feed, in particular to control and / or regulate the amount of application material supplied to the processing area, the application material flow, and / or the height of a material structure applied in the processing area. Brief description of the drawings

[0072] The invention is described in detail below with reference to figures. Fig. 1 shows a schematic view of a laser cladding apparatus according to embodiments of the invention; Fig. 2 shows a schematic view of a laser cladding apparatus according to embodiments of the invention; Fig. 3 shows a schematic representation of positions of a measuring beam on a first reflector; Fig. 4 shows a schematic representation of a measuring beam at different times of a scanning figure of the measuring beam; Fig. 5 shows schematically a scan figure of a measuring beam at a measuring position in the forward run as well as a height profile; Fig. 6 shows schematically a scan figure of a measuring beam at a measuring position in the wake and a height profile; Fig. 7 shows schematically a scan figure of a measuring beam at a measuring position in the processing point as well as a height profile; and Fig. 8, Fig. 9 and Fig. 10 each show a schematic view of a respective device for laser cladding according to embodiments of the invention. Detailed description of the drawings

[0073] In the following, unless otherwise stated, the same reference symbols are used for identical and equivalent elements.

[0074] Fig. 1 shows a schematic representation of a device 10 for laser cladding according to embodiments of the present disclosure. The device 10 can be coupled to a laser source 12 for generating a laser beam 14, also referred to as a processing laser beam, in order to couple the laser beam 14 into a laser processing head 16 of the device 10. The device 10 comprises the laser processing head 16 for irradiating and directing the laser beam 14 onto a processing area of ​​a workpiece 18.

[0075] The device 10 further comprises a feed device 20 for a coating material, which is configured to feed the coating material to the processing area coaxially to the laser beam 14.

[0076] The device 10 can be configured to apply the supplied deposition material to a workpiece 18 by laser deposition welding or to form at least one workpiece 18 from the supplied deposition material by laser deposition welding. The deposition material can be, for example, wire, a metal powder, or a powder-filled wire. In several processing passes, structures can be formed from the deposition material on the workpiece 18, for example. Fig. 1 schematically shows the construction of a structure, for example a wall, whose height in the already machined area of ​​the workpiece 18 protrudes compared to the area still to be machined.

[0077] The laser beam 14 is transmitted via an optical fiber 15 from the laser source 12 to the laser processing head 16 and coupled into the laser processing head 16 from one end of the optical fiber 15, e.g., by means of a fiber coupler. The laser processing head 16 can further have collimator optics 22 for collimating the laser beam 14 emerging divergently from the end of the optical fiber 15. With the aid of the collimator optics 22, the focus position of the laser beam 14 can be set or corrected. The focus position can be adjustable, for example, along an optical axis of the laser processing head 16. The axis can be referred to as the z-axis. The laser processing head 16 further comprises a focusing device 23 with focusing optics 24 for focusing the laser beam 14 onto the processing area. The focusing optics 24 can, for example, comprise a lens.

[0078] The laser processing head 16 further comprises a first reflector 26 and a second reflector 28, which are arranged concentrically on a common central axis corresponding to the optical axis O of the laser processing head 16. The first reflector 26 is a conical metal reflector whose reflective surface has continuous rotational symmetry with respect to the common central axis. The laser beam 14 concentrically incident on the first reflector 26 is reflected outward by the first reflector 26 at an angle to the central axis onto the second reflector 28. The first reflector 26 thus splits the laser beam 14 and generates an annular beam profile of the laser beam 14.

[0079] The second reflector 28 is, for example, annular and reflects the laser beam 14 in a direction offset parallel to the central axis. The laser beam 14 reflected by the second reflector 28 can have an annular, for example, cylindrical, beam profile. The laser beam 14 reflected by the second reflector 28 is then focused by the focusing optics 24 into the processing area. The second reflector 28 thus reflects the laser beam 14 via the focusing optics 24 in the direction of the processing area. The second reflector 28 is thus configured to reflect the laser beam 14 through the focusing optics 24 onto the processing area at an angle to the central axis. The second reflector has, for example, a reflective surface with continuous rotational symmetry with respect to the common central axis. The second reflector 28 is annular and has a circular recess 29 concentric with the central axis.The reflective surface surrounds the circular recess 29. The second reflector is made of metal, for example. The laser beam 14, which passes through the focusing device 23 and is freely directed onto the processing area, is directed by the focusing optics 24 in a ring-shaped and converging pattern into the processing area and / or onto the circumference of the coaxially fed deposit material. The laser beam 14, which is freely directed onto the processing area, thus has an annular beam profile whose diameter decreases toward the processing area. The deposit material is melted by the laser beam 14 and applied to the workpiece 18.

[0080] In order to apply the deposition material along a processing trajectory and to irradiate the laser beam along the processing trajectory, the device 10 further comprises a positioning device 30 that can move the laser processing head 16 relative to the workpiece 18 in an x-direction, a y-direction, and additionally in the z-direction. A current processing direction A is in Fig. 1 and corresponds to a (current) feed direction of the laser processing head 16.

[0081] The device 10 further comprises a distance measuring device 34 for interferometric distance measurement or optical distance measurement by means of an optical measuring beam 36. The distance measuring device 34 is configured, for example, to measure a distance between the laser processing head 16 and the workpiece 18.

[0082] According to the embodiment, the distance measuring device 34 comprises an optical coherence tomograph or can be designed as an optical coherence tomograph. In other words, the distance measurement can be based on optical coherence tomography (OCT). The distance measuring device 34 comprises an evaluation unit 38 with a broadband light source 39, for example, a superluminescent diode. The light source 39 couples measurement light into an optical fiber 40. In a beam splitter 42, which is preferably designed as a fiber coupler, the measurement light is split into a reference arm 44 and a measurement arm 46. The measurement light from the measurement arm 46 is transmitted as the optical measurement beam 36 via an optical fiber to a scanning device 50 for deflecting the measurement beam 36.

[0083] The scanning device 50 is a 2D scanning device for deflecting or directing the optical measuring beam 36 relative to the laser beam 14 or relative to the optical axis O of the laser processing head 16. The scanning device 50 is configured to move and deflect the optical measuring beam 36 relative to the workpiece 18 along two directions. The two directions can correspond to the x-direction and y-direction. The measuring beams 36a and 36b schematically represent the orientation of the measuring beam 36 at two different positions, or at two different times. With the aid of the scanning device 50, the surface of the workpiece 18 can be scanned in a position relative to the processing position.

[0084] According to embodiments, the scanning device 50 comprises two movable mirrors 54a, 54b that are rotatable about different axes of rotation. The mirrors 54a, 54b can be designed as galvanometer mirrors. In this case, the scanning device 50 can be referred to as a galvanometer scanner or galvo scanner.

[0085] The scanning device 50 further comprises a beam-shaping optics 52 with at least one optical lens 52a, 52b, 52c for beam expansion and / or collimation and / or focusing of the measuring beam 36. In particular, the beam-shaping optics 52 can comprise a first lens 52a for collimating the measuring beam 36, a second lens 52b for focusing the measuring beam 36 on the scanning device 50, and a third lens 52c for re-collimating or beam expanding the measuring beam 36.

[0086] The laser processing head 16 further comprises a coupling device 56 for coupling the optical measuring beam 36 into the laser processing head 16. The coupling device 56 is configured to superimpose the optical measuring beam 36 with the laser beam 14. The coupling device 56 comprises, for example, a beam splitter, which can be designed as a dichroic mirror or can comprise one. The beam splitter can reflect light from the optical measuring beam 36 and allow light from the processing laser beam 14 to pass through. According to embodiments, the (undeflected) optical measuring beam 36 and the laser beam 14 can run parallel and / or coaxial to one another at least in sections.The coupling of the optical measuring beam 36 into the laser processing head 16 by the coupling device 56 takes place in the beam propagation direction of the measuring beam 36 after the scanning device 50 and takes place in the subsequent joint beam propagation alignment of the measuring beam 36 and the laser beam 14 in front of the first reflector 26 and second reflector 28. In particular, the measuring beam 36 and the laser beam 14 pass through the first reflector 26 and the second reflector 28 in a common beam path and are jointly reflected by the first reflector 26 and jointly reflected by the second reflector 28 in the direction of the processing area and directed onto the processing area by the focusing optics 24.

[0087] Since the coupling device 56 is arranged in the beam path of the measuring beam after the scanning device 50, the optical measuring beam 36 is deflected by the scanning device 50 relative to the laser beam 14.

[0088] The distance measurement principle described here is based on the principle of optical coherence tomography, which utilizes the coherence properties of light with the aid of an interferometer. For distance measurement, the optical measuring beam 36 is irradiated onto a surface of the workpiece 18. The portion of the optical measuring beam 36 reflected back from the surface is imaged onto the end of the optical fiber of the measuring arm 46, superimposed in the beam splitter 42 with the reflected portion of the measuring light from the reference arm 44, and caused to interfere. The superimposed light contains information about the path length difference between the reference arm 44 and the measuring arm 46. This information is evaluated by the evaluation unit 38. This allows information about the distance to the workpiece 18 or between the workpiece 18 and the laser processing head 16 to be obtained.

[0089] According to embodiments, the reference arm 44 can be designed as a dynamic reference arm. This allows the measuring range of the measuring device 34 to be expanded.

[0090] The device 10 further comprises a control and evaluation device 60. The control and evaluation device 60 performs the function of a control device for controlling the scanning device 50 to move the measuring beam 36 along a scan path, in particular according to a predetermined scan pattern. The scan pattern defines, for example, a temporal progression of the scan path in the x-direction and y-direction. The scan pattern can define a temporal progression of the scan path relative to the machining direction.

[0091] The control and evaluation device 60 includes a memory 62 for calibration data. The calibration data takes into account an optical distortion and an optical path length (or a reference height) of a beam path of the measuring beam 36 across the first reflector 26 and the second reflector 28. The control and evaluation device 60 can control the scanning device 50 to position or move the measuring beam 36 based on the stored calibration data.

[0092] The control and evaluation device 60 further assumes the function of an evaluation device for determining a surface geometry of the workpiece 18 based on the stored reference height data and from distances measured by the distance measuring device 34. For a current measuring position of the measuring beam 36 in accordance with the corresponding control of the scanning device 50, the control and evaluation device 60 receives certain raw distance data, for example a distance, from the evaluation unit 38. The control and evaluation device 60 can, for example, determine an actual distance to the workpiece 18 or a height of the workpiece 18 at the corresponding measuring position from the raw distance data determined by the evaluation unit 38 based on the reference height data. The control and evaluation device 60 can determine a surface geometry from the respectively measured distances, for example a height profile along the scan path orof the scan figure based on the stored reference elevation data.

[0093] The control and evaluation device 60 further assumes the function of a job control device for controlling or regulating the material feed by the feed device 20. The control and evaluation device 60 is particularly configured to control the material feed as a function of a distance measured by the distance measuring device 34 or as a function of an actual distance determined based on the reference height data. For example, the material feed can be carried out based on a measured distance or a measured height of the workpiece 18 along the machining direction in the feed direction by a proportional-integral controller with a time offset in order to regulate the current material application at the corresponding point on the workpiece where the distance was measured.

[0094] In addition to the described deflection of the measuring beam 36 by the scanning device 50, the scanning device 50 can also be configured to adjust or modify an inclination of the measuring beam 36 to the optical axis and / or a beam diameter of the measuring beam. For example, in the example of Fig. 1, the lenses 52b, 52c of the beam-shaping optics can be adjustable in the beam propagation direction to modify a beam diameter. For this purpose, the scanning device 50 can have respective actuators 55b, 55c for the lenses 52b, 52c, which are controlled by the control and evaluation device 60.

[0095] Based on the Fig. 2, further embodiments are described below which differ from the embodiments of the Fig. 1 by a different structure of the second reflector 28. Otherwise, the device 10 corresponds to the Fig. 2 the structure of the device 10 of the Fig. 1.

[0096] In Fig. 2, the second reflector 28 is configured to reflect the laser beam 14 at an angle to the central axis directly toward the processing area. Furthermore, the second reflector 28 is configured to focus the laser beam with respect to the processing point, in particular to create an annular focus. The second reflector 28 is, for example, a ring segment of a parabolic mirror and can, for example, focus both the laser beam and the measuring beam 36a, 36b. Instead of the focusing optics 24 formed by at least one lens of the Fig. 1, the focusing of the laser beam 14 and the measuring beam 36a, 36b is thus achieved by the curvature of the reflecting surface of the second reflector 28. The second reflector 28 reflects the laser beam 14 at an angle to the central axis in the direction of the processing area.

[0097] In the examples described, the feed material is fed coaxially to the laser beam 14 into the processing area, wherein the feed material is fed into the interior of the annular beam profile of the laser beam 14, as in Fig. 1 and Fig. 2, passes through a region in which the laser beam 14 is radially divided into a ring. This minimizes shadowing of the laser beam 14 and the measuring beam 36. The feed device 20 can, for example, comprise a metallic protective cover for the feed material in this region, which can be reflective.

[0098] In Fig. 1 and Fig. 2, the coupling device 56 is configured to reflect light from the optical measuring beam 36a, 36b and to allow light from the laser beam 14 to pass through. However, the present disclosure is not limited thereto. The coupling device 56 can also be configured to allow light from the optical measuring beam 36a, 36b to pass through and to reflect light from the laser beam 14.

[0099] Fig. 3 and Fig. 4 schematically show examples of different deflections of the measuring beam 36 at different times of a scan figure 64 of the measuring beam 36. Fig. 3 schematically shows the respective position of the measuring beam 36 on the first reflector 26 in a plan view in the beam propagation direction of the laser beam 14. The scan figure 64 is, for example, circular and defines a circular revolution of the position of the measuring beam 36 around the optical axis O. In the left part of the Fig. 3, the measuring beam 36 is located to the right of the optical axis O. The left part of Fig. 4 schematically shows the corresponding beam path of the measuring beam 36 and the laser beam 14 in the area between the coupling device 56 and the workpiece 18. The right part of the Fig. 3 shows the measuring beam 36 at a position on the left side of the optical axis O. Accordingly, the right side of Fig. 4 the path of the optical measuring beam 36 and the path of the laser beam 14 in the area between the coupling device 56 and the workpiece 18. In the figures, arrows indicate the rotational movement of the measuring beam 36 about the optical axis O.

[0100] Fig. Figure 5 shows an example and schematic representation of a distance measurement in the pre-processing stage with a line-shaped scanning figure 64 perpendicular to the processing trajectory. Along the scanning figure 64, for example, the Fig. 5, the profile of the height of the workpiece 18 is shown schematically on the right. In the example, the scan figure 64 is arranged transversely to a deposited wall structure, the height of which can be determined from the height profile. In the current processing pass, another layer is applied to the wall structure along the processing direction A. The material feed in the processing area B shown can be controlled at the current time based on the height previously measured for the same position of the workpiece, for example, in order to create the most uniform possible profile of the target height of the structure to be deposited.

[0101] Fig. Figure 6 shows a schematic view of a measurement position during the wake. The height profile obtained here along scan figure 64, in Fig. 6 shown on the right, can be temporarily stored, for example, in a memory of the control and evaluation device 60 until the corresponding position on the workpiece 18 is reached again in a subsequent processing pass. The application quantity of the feed material can then be controlled accordingly, for example, in order to again achieve the most uniform possible overall application height of the application material along the structure to be applied.

[0102] In the examples of Fig. 5 and Fig. 6, the control and evaluation device 60 positions the scan figure 64 based on the machining direction A and / or based on the machining trajectory and aligns the scan figure 64 accordingly. In the example shown of the line-shaped scan figure 64, the alignment occurs, for example, transversely to the machining trajectory. The control and evaluation device 60 accordingly controls the scanning device 50 to position and move the measuring beam 36 based on the machining direction and / or the machining trajectory.

[0103] Fig. Figure 7 shows an example of a circular scan figure 64 positioned around the processing point or optical axis O. The example shows a plotted structure in which the processing path (the processing trajectory) includes segments of different directions. The right part of Fig. Figure 7 shows the height profile obtained along scan figure 64 in the height direction z above the circulating roll α of scan figure 64. Taking into account the course of the processing trajectory, the distance can be measured along the processing trajectory both in the lead-up and in the follow-up. The control and evaluation device 60 can regulate the material feed by the feed device 20 depending on the determined height or the measured distance on the processing trajectory (in the lead-up), for example, to achieve a uniform material application height along the processing trajectory.

[0104] In addition to the described control of the feed device 20, the control and evaluation device for controlling the material application height can, for example, also control the laser source 12 in order to control an intensity of the laser beam.

[0105] While the Fig. 5 and Fig. 6 Show distance measurements at measuring positions in the lead-in or the lag-in and the Fig. 7 show distance measurements at measuring positions at a distance from the processing area, the control and evaluation device 60 can also be configured to measure a distance measurement at a measuring position in the processing area, for example near the optical axis O, and to use it, for example, to control the material feed.

[0106] In the embodiments of the Fig. 1 and Fig. 2, instead of the described conical first reflector 26, a pyramid-shaped first reflector 26 with a rotationally symmetrical arrangement of reflecting surfaces (facets) can also be used, for example, to split the laser beam 14 and reflect it outward onto the second reflector. The second reflector 28 can then be constructed, for example, from annularly arranged segments. In particular, the first and / or second reflector can have a discrete rotational symmetry of their reflecting surface(s).

[0107] Fig. Figure 8 shows another example of a device 10 for laser deposition welding according to embodiments of the invention. Fig. The device 10 shown in Figure 8 differs from that shown in Fig. 2 in that the laser beam 14 is fed from the laser source 12 to the laser processing head 16 via a fiber array of optical fibers 15. The laser beam 14 thus comprises a plurality of (partial) laser beams, which are deflected by the first reflector 26 into a radial distribution of beams and reflected onto the second reflector 28. The laser beam 14 can, for example, already have an annular beam profile when passing through the coupling device 56 and upon impact with the first reflector 26. The annular beam profile of the laser beam 14 is expanded by the first reflector 26 and the second reflector 28 and guided around the coaxial material feed.

[0108] In Fig. 9 shows a further embodiment of the device 10. This embodiment differs from the embodiment in Fig. 1 merely in that the measuring beam 36 is only collimated, and the beam-shaping optics 52 of the scanning device 50 accordingly comprises only one lens 52a for collimation. With the scanning device 50, the collimated measuring beam 36 is deflected so that it is not entirely parallel to the optical axis O. This allows the measuring beam 36 to strike the workpiece slightly offset from the laser beam 14. This embodiment has the advantage of a compact and simple design.

[0109] In Fig. 10 shows a further embodiment of the device 10. This embodiment differs from the embodiment in Fig. 2 merely by the fact that the measuring beam 36 is analogous to Fig.9, and the beam-shaping optics 52 of the scanning device 50 accordingly comprises only one lens 52a for collimation. With the scanning device 50, the collimated measuring beam 36 is deflected such that it is not entirely parallel to the optical axis O. This allows the measuring beam 36 to strike the workpiece slightly offset from the laser beam 14. This embodiment also has the advantage of a compact and simple design.

[0110] A preferred aspect of the invention and its specific embodiments are set forth below: 1. A laser cladding device according to this aspect comprises: a laser processing head for irradiating a laser beam; a feeding device for coaxially feeding a deposition material; and a first reflector and a second reflector having a common central axis, wherein the first reflector is configured to reflect the laser beam outwardly onto the second reflector at an angle to the central axis, and wherein the second reflector is configured to reflect the laser beam toward a processing area. 2. Device according to number 1, wherein the first and second reflectors are arranged in front of the feeding device in the beam propagation direction of the laser beam. 3. Device according to number 1 or 2, wherein the second reflector is arranged to reflect the laser beam offset parallel to the central axis or at an angle to the central axis in the direction of the processing area. 4. Device according to number 1, 2 or 3, wherein the second reflector is arranged to focus the laser beam and / or the measuring beam with respect to a processing point. 5. Device according to number 1, 2, 3 or 4, further comprising: a job control device for controlling and / or regulating the material feed and / or a laser power. 6. Device according to one of numbers 1 to 5, wherein the coating material is a coating material in the form of a wire, a powder-filled wire or a powder. 7. Device according to one of numbers 1 to 6, wherein the first reflector is substantially conical and / or pyramidal. 8. Device according to one of numbers 1 to 7, wherein the first reflector has at least one reflecting surface with continuous or discrete rotational symmetry with respect to the common central axis. 9. Device according to one of numbers 1 to 8, wherein the second reflector has at least one reflecting surface with continuous or discrete rotational symmetry with respect to the common central axis. 10. Device according to one of numbers 1 to 9, wherein the second reflector is annular and / or has a circular recess concentric with the central axis surrounding a reflective surface. 11. Device according to one of numbers 1 to 10, wherein the second reflector is a ring segment of a parabolic mirror. 12. Device according to one of numbers 1 to 11, wherein the first reflector and / or the second reflector are made of metal. 13. Device according to one of numbers 1 to 12, wherein the laser beam is annular after exiting the laser processing head. 14. The device according to any one of claims 1 to 13, further comprising: a distance measuring device for measuring a distance using a measuring beam; and a scanning device for deflecting the measuring beam. 15. Device according to number 14, further comprising: a coupling device for coupling the beam path of the measuring beam into the beam path of the laser beam. 16. Device according to number 15, wherein the first reflector and the second reflector are arranged between the coupling device and the feeding device and are located in a common beam path of the laser beam and the measuring beam. 17. Device according to number 14, 15, or 16, further comprising: a control device for controlling the scanning device, wherein the control device is configured to control the scanning device for positioning or moving the measuring beam. 18. Device according to number 14, 15, 16 or 17, wherein the device comprises a memory for calibration data, wherein the calibration data take into account an optical distortion and / or an optical path length of a beam path of the measuring beam, in particular an optical path length of a beam path of the measuring beam via the first reflector and / or via the second reflector and / or via further optical components. 19. Device according to number 18, wherein the control device is arranged to control the scanning device for positioning or moving the measuring beam based on data of an XY calibration stored in the memory. 20. Apparatus according to number 18 or 19, wherein the distance measuring device is arranged to determine a relative height at a respective measuring position based on the reference height data stored in the memory and the measured distances. 21. Device according to number 14, 15, 16, 17, 18, 19 or 20, wherein the distance measuring device is arranged to measure the distance at a measuring position in the pre-run, in the processing area and / or in the post-run. 22. Device according to number 14, 15, 16, 17, 18, 19, 20 or 21, wherein the distance measuring device comprises an optical coherence tomography (OCT) device or a time-of-flight (ToF) sensor. 23. Device according to number 14, 15, 16, 17, 18, 19, 20, 21 or 22, further comprising an evaluation device for determining a surface geometry from distances measured by the distance measuring device. 23. Device according to one of numbers 1 to 22, further comprising focusing optics arranged on the common central axis for focusing the laser beam. 24. Device according to number 23, wherein the second reflector is arranged to reflect the laser beam through the focusing optics at an angle to the central axis onto the processing area. 25. Device according to number 14, 15, 16, 17, 18, 19, 20, 21 or 22, further comprising focusing optics arranged on the common central axis for focusing the laser beam and / or the measuring beam. 26. Device according to number 25, wherein the second reflector is arranged to reflect the laser beam and / or the measuring beam through the focusing optics at an angle to the central axis onto the processing area. 27. Device according to number 14, 15, 16, 17, 18, 19, 20, 21, 22, 25 or 26, further comprising a job control device for controlling and / or regulating a laser power and / or the material feed by the feed device as a function of a distance measured by the distance measuring device and / or of a surface geometry determined from distances measured by the distance measuring device. List of reference symbols 10 Device for laser cladding 12 Laser source 14 Laser beam 15 optical fibers 16 laser processing head 18 Workpiece 20 Feeding device 22 Collimator optics 23 Focusing device 24 Focusing optics 26 first reflector 28 second reflector 29 recess 30 Positioning device 34 Distance measuring device 36 measuring beam 38 Evaluation unit 39 Light source 40 optical fibers 42 beam splitters 44 Reference arm 46 measuring arm 50 scanning device 52 Beam shaping optics 52a, 52b, 52c lenses 52c collimation lens 54a, 54b Mirror 55b, 55c Actuators 56 Coupling device 60 Control and evaluation device 62 storage 64 scan figure 70 scanning device 72a, 72b Scanning mirror QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2018 / 178387 A1

[0003] US 2022 / 0134440 A1

[0004]

Claims

[1] Device (10) for laser cladding, comprising: a laser processing head (16) for irradiating a laser beam (14); a distance measuring device (34) for measuring a distance by means of a measuring beam (36); a scanning device (50) for deflecting the measuring beam (36); a coupling device (56) for coupling the beam path of the measuring beam (36) into the beam path of the laser beam (14); a feeding device (20) for coaxially feeding a coating material; and a first reflector (26) and a second reflector (28) which have a common central axis and which are arranged between the coupling device (56) and the feeding device (20) in a common beam path of the laser beam (14) and the measuring beam (36), wherein the first reflector (26) is arranged to reflect the laser beam (14) and the measuring beam (36) outwardly onto the second reflector (28) at an angle to the central axis, and wherein the second reflector (28) is configured to reflect the laser beam (14) in the direction of a processing area. [2] Device according to claim 1, wherein the second reflector (28) is arranged to reflect the laser beam (14) offset parallel to the central axis or at an angle to the central axis in the direction of the processing area. [3] Device according to claim 1 or 2, wherein the second reflector (28) is arranged to focus the laser beam (14) and / or the measuring beam (36) with respect to a processing point. [4] Device according to one of the preceding claims, further comprising: a control device (60) for controlling the scanning device (50), wherein the control device (60) is configured to control the scanning device (50) for positioning or moving the measuring beam (36) based on a processing direction and / or a processing trajectory. [5] Device according to claim 4, wherein the control device (60) is configured to control the scanning device (50) to move the measuring beam (36) according to a predetermined scanning figure (64), wherein the control device (60) is configured to position and / or align the scanning figure (64) based on a machining direction and / or a machining trajectory. [6] Device according to claim 4 or 5, wherein the device (10) comprises a memory (62) for calibration data which takes into account an optical distortion and / or an optical path length of a beam path of the measuring beam (36) via the first reflector (26) and / or via the second reflector (28) and / or via further optical components, and wherein: the control device (60) is configured to control the scanning device (50) for positioning or moving the measuring beam (36) based on the reference height data stored in the memory (62); and / or the distance measuring device (34) is configured to determine a relative height at a respective measuring position based on the reference height data stored in the memory (62) and the measured distances. [7] Device according to one of the preceding claims, wherein the distance measuring device (34) is arranged to measure the distance at a measuring position in the pre-run, in the processing area and / or in the post-run. [8] Device according to one of the preceding claims, further comprising: an evaluation device (60) for determining a surface geometry from distances measured by the distance measuring device (34). [9] Device according to one of the preceding claims, wherein the distance measuring device (34) comprises an optical coherence tomography (OCT) device or a time-of-flight (ToF) sensor. [10] Device according to one of the preceding claims, wherein the deposition material is a deposition material in the form of a wire, a powder-filled wire or a powder. [11] Device according to one of the preceding claims, wherein the first reflector (26) is substantially conical and / or pyramidal, and / or wherein the first reflector (26) has at least one reflective surface with continuous or discrete rotational symmetry with respect to the common central axis. [12] Device according to one of the preceding claims, wherein the second reflector (28) has at least one reflective surface with continuous or discrete rotational symmetry with respect to the common central axis. [13] Device according to one of the preceding claims, wherein the second reflector (28) is annular, and / or has a circular recess (29) concentric with the central axis surrounding a reflecting surface, and / or wherein the second reflector (28) is a ring segment of a parabolic mirror. [14] Device according to one of the preceding claims, wherein the first reflector (26) and / or the second reflector (28) are made of metal. [15] Device according to one of the preceding claims, wherein the device further comprises a focusing optics (24) arranged on the common central axis in order to focus the laser beam (14) and / or the measuring beam (36), and wherein the second reflector (28) is arranged to reflect the laser beam (14) and / or the measuring beam (36) through the focusing optics (24) at an angle to the central axis onto the processing area. [16] Device according to one of the preceding claims, wherein the laser beam (14) is annular after exiting the laser processing head (16). [17] Device according to one of the preceding claims, further comprising: a job control device (60) for controlling and / or regulating the material feed by the feed device (20) and / or a laser power as a function of a distance measured by the distance measuring device (34) and / or of a surface geometry determined from distances measured by the distance measuring device (34).

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