Device and method for checking a powder injection device of a laser cladding device

Abstract

The invention relates to a device (1) for checking a powder injection device (2) of a laser deposition welding device (3), comprising a first testing device (P1) with a camera (10) for checking a powder jet caustic and a powder mass flow (PM) and a second testing device (P2) for determining a position of a multi-jet powder nozzle (8). In the first testing device (P1), the camera (10), a lighting unit (13), a load cell (11) and a collecting tray (12) on the load cell (11) are arranged in a housing (14) which has an opening (15) for arranging a welding nozzle (5), wherein a camera focus of the camera (10) is aligned horizontally to a powder jet focus area and the lighting unit (13) is aligned to the powder jet focus area.The second testing device (P2) comprises an inclination sensor (16) for determining an inclination of the welding nozzle (5) and a distance sensor (17) for determining a distance (A) of the welding nozzle (5) to a reference plane (RE), which are arranged on an underside of a sensor holder (18) which can be fastened in a form-fitting manner centered on the welding nozzle (5), wherein the distance sensor (17) is arranged on the sensor holder (18) in such a way that it is positioned on a rotation axis of the welding nozzle (5) when the sensor holder (18) is fastened to the welding nozzle (5).

Description

The invention relates to an apparatus and a method for checking a powder injection device of a laser build-up welding device.As described in WO 2023 / 016993 A1, a method and a device for powder injection monitoring in laser beam build-up welding are known from the prior art. A powder jet is directed from a powder nozzle onto a workpiece. The powder in the powder jet is fused to the workpiece by a working laser beam irradiated on the workpiece. The powder beam is illuminated by an illuminating laser beam transverse to the direction of the powder beam. A camera having a viewing direction which runs parallel to the beam direction of the powder beam images the section of the powder beam which is illuminated by the illumination laser beam. The aforementioned steps take place simultaneously. An algorithm performs an actual assessment of the illuminated portion of the powder jet. If the actual evaluation deviates from a desired evaluation to a predetermined extent, a message is output.WO 2019 / 138038 A1 describes a system and a method for monitoring the production accuracy in the additive production of three-dimensional components. A combined illumination and detection element has a two-dimensional detector array and a laser radiation source, with which electromagnetic radiation is directed onto a region of a material in powder form or in paste form, with which a region of a three-dimensional component is produced as a result of a locally defined energy input. The detector array is arranged and configured such that speckle occurring in / on the surface irradiated by the laser radiation source can be detected in a spatially resolved manner. The speckle signals detected with the detector array in a spatially resolved manner can be fed to an electronic evaluation and control circuit which is connected to an electronic control and regulating device which is designed to influence the production process. A thermal speckle excitation can be achieved with a separate energy beam or an energy beam, with which the energy input takes place locally defined on the material for additive three-dimensional production, which material is present in powder form or in paste form.WO 2015 / 155116 A1 and DE 10 2014 206 767 B3 disclose a method and a device for measuring powder flows of a laser welding tool. The method comprises successively using a plurality of apertures having apertures of different sizes, wherein the aperture is arranged in each case in the working region of the laser welding tool, a powder jet is applied for each aperture for a predetermined period of time, and the powder mass respectively passed through the respective aperture is weighed.EP 3 900 869 A1 describes a method and an apparatus for optical quality control in laser build-up welding. In the process of laser build-up welding, the surface of a workpiece to be coated is fused by means of a high-energy laser beam directed onto a processing spot of the surface and focused by a focusing optics, whereby a melt pool is produced in the processing spot. A powdery coating material is applied to the melt bath at the processing spot. The electromagnetic radiation emitted as light by the molten bath is captured by means of an image capture device, wherein the brightness of the emitted light represents the intensity of the emitted electromagnetic radiation. The acquired image information of the melt pool is forwarded to an image evaluation unit. The location data of a region of the same intensity and / or of a region within a specific intensity interval in the captured image information are determined by calculation to form a contour of the region. A symmetrical surface element is assigned to the region of the same intensity by approximating a geometric figure to the contour of the region. Features characteristic of the geometric shape of the symmetrical planar body are determined and stored as a data record in a data storage device. A parameter of the laser build-up welding process that influences the quality of the coating is recorded, monitored and / or monitored by means of a process control device on the basis of the data of the characteristic features of the symmetrical sheet.DE 10 2020 123 479 A1 describes a method for monitoring the state of a laser processing head and a laser processing system for carrying it out. Current measurement data are recorded by a sensor unit arranged within the laser processing head. Based on the acquired current measurement data, an input vector is determined. By applying a machine learning trained model to the input vector, an output vector containing estimated current state data of two elements of the laser processing head is determined.DE 10 201 19 121 948 A1 and DE 10 201 121 948 B4 describe a device and a method for measuring a powder mass flow for powder nozzle build-up welding. By means of a powder mass determination device, the powder mass flow is set before the powder nozzle build-up welding and a powder mass flow sensor is calibrated after the setting. Then, powder nozzle build-up welding is started by a powder switch without stopping the conveyance of the powder mass. During powder mass build-up welding, the powder mass flow is monitored by means of the powder mass flow sensor.DE 10 2018 202 203 B4 discloses an arrangement for adjusting a powder flow with respect to the central longitudinal axis of an energy beam for a working head which is designed for powder build-up welding. On the working head there is a device for two- or three-dimensional alignment of a powder feed with respect to the central longitudinal axis of a laser beam in a plane aligned perpendicular to the central longitudinal axis of the laser beam. An electronic evaluation unit is designed such that a number of individual detected image points, at which a predeterminable intensity threshold value has been exceeded, which have been detected within the irradiated region, are determined and evaluated and / or pattern recognition is carried out with the image points detected within the irradiated region. The electronic evaluation unit is designed to determine the shape, size and / or length of an irradiated region in which spatially resolved intensities which exceed a predeterminable threshold value have been detected with an optical detector array and in the process the irradiated region extends, starting from the surfaces of particles of the pulverulent material on which the laser beam, which is operated with reduced power during the adjustment, impinges, as far as a partial region of the irradiated region in which the particles heated with the laser beam move divergently.KR 10 2004 0 084 309 discloses a position measuring device for a laser head of a laser welding device having a body and a robot controller. The body includes the laser head, a connection unit, an angle measurement sensor, a distance measurement sensor, a reference plane, a probe, a ball, a contact detection sensor, and a spring. The connection unit comprises a tap having a screw coupling structure. The angle measurement sensor detects an angle of the laser head. The contact detection sensor detects whether the probe contacts a welding object.JP 2001 023 918 A describes an apparatus for producing thin semiconductor layers. Pulsed UV rays supplied from the first and second excimer lasers EL1, EL2 are directed to a homogenizer via a class of mirrors and a class of lenses.The object of the invention is to specify a method which is improved in comparison with the prior art and a device which is improved in comparison with the prior art for checking a powder injection device of a laser build-up welding device.The object is achieved according to the invention by a device for checking a powder injection device of a laser deposition welding device having the features of claim 1 and a method for checking a powder injection device of a laser deposition welding device having the features of claim 3.Advantageous embodiments of the invention are the subject matter of the dependent claims.A laser deposition welding device has a laser welding head with a welding nozzle which is fastened via a ball joint to a robot which has in particular three translatory and three rotatory degrees of freedom or at least three translatory and three rotatory degrees of freedom. Furthermore, the laser build-up welding device has a powder injection device. The welding nozzle has a multi-jet powder nozzle of the powder injection device for discharging a powder jet of a powder conveyed by means of a powder conveyor of the powder injection device.A device according to the invention for checking in particular the laser deposition welding device, in particular the powder injection device, has a first checking device for checking a powder jet caustic, in particular a powder jet focus diameter of the powder jet, and a powder mass flow. The device further comprises a second test device for determining a position of the multi-jet powder nozzle.The first test device has a camera, a load cell, a collecting tray for collecting powder sprayed through the multi-jet powder nozzle, an illumination unit, in particular designed as an LED (light-emitting diode), and a housing in which the camera, the illumination unit, the load cell and the collecting tray are arranged on the load cell. The housing has an opening for arranging the welding nozzle. A camera focus of the camera is aligned horizontally with a powder jet focus region in the housing, in which a powder jet focus of the powder jet is positioned when the welding nozzle is arranged at the opening and the powder jet is discharged. The illumination unit is aligned with the powder beam focus region.The second test device has an inclination sensor for determining an inclination of the welding nozzle and a distance sensor for determining a distance of the welding nozzle from a reference plane. The inclination sensor and the distance sensor are arranged on an underside of a sensor holder, which can be fastened to the welding nozzle in a positively centered manner. The distance sensor is arranged on the sensor holder in such a way that, in the state of the sensor holder fastened to the welding nozzle, it is positioned on an axis of rotation, in particular axis of rotational symmetry, of the welding nozzle.In one embodiment, the second inspection device further comprises a marking plate having two coaxial circular markings with different diameters. The markings are in particular formed as a engraving.In a method according to the invention for checking, in particular, the laser application welding device, in particular the powder injection device of the laser application welding device, by means of the device, which is in particular not carried out during a laser application welding process, but advantageously before the laser application welding process, the powder jet caustic and the powder mass flow are checked by means of the first checking device by the welding nozzle being moved by means of the robot to a predetermined, in particular first, reference point at which the welding nozzle docks at the opening of the housing, the powder is conveyed, a weight of the collecting tray filling with the powder is dynamically measured and stored by means of the load cell and a temporal change in the powder mass flow is thereby detected, the powder jet focus is illuminated by means of the illumination unit, an image or video of the powder jet caustic is recorded by means of the camera, and weight values measured by means of the load cell and the image or video recorded by means of the camera can be evaluated. For this purpose, the housing is arranged, for example, on a processing table, in particular a rotary tilting table, of the laser deposition welding device.Furthermore, the position of the multi-jet powder nozzle is determined by means of the second test device by fastening the sensor holder in a positively centered manner on the welding nozzle, moving the welding nozzle to a predetermined, in particular second, reference point above the reference plane, determining the distance of the welding nozzle from the reference plane by means of the distance sensor, and determining the inclination of the welding nozzle by means of the inclination sensor by determining a respective acceleration in all three spatial axes of a three-dimensional coordinate system and a respective rotation about all three spatial axes. The second reference point may correspond to or deviate from the first reference point. The reference plane is formed here, for example, by the processing table.In one embodiment of the method, the marking plate is fastened in an accurate position on a table, in particular on the processing table. The welding nozzle is moved to a predetermined, in particular third, reference point above the marking plate, wherein the reference point is predetermined such that the powder jet focus lies on the marking plate. This third reference point may correspond to the first and / or second reference point or may deviate therefrom. Pilot lasers of the welding nozzle, which are oriented such that pilot laser beams of the pilot lasers intersect in the powder beam focus, in particular within a powder beam focus diameter, are switched on. A position of a measurement spot generated by the pilot lasers on the marking plate with respect to the two coaxial circular markings is evaluated.In one embodiment of the method, the powder beam focus is measured by means of edge detection in the image or video recorded by means of the camera.In one embodiment of the method, a respective partial powder mass flow is checked by successively conducting only one partial powder mass flow to one of a plurality of nozzle openings of the multi-jet powder nozzle by means of a powder divider.For example, it is provided that the welding nozzle is exchanged when the powder jet caustic and / or the powder mass flow and / or at least one powder partial mass flow deviate from a respective specification.For example, it is provided that a position of the welding nozzle relative to the Z axis of the three-dimensional coordinate system relative to a nozzle holder holding the welding nozzle is corrected if the distance of the welding nozzle to the reference plane determined by means of the distance sensor deviates from a predefined value.For example, it is provided that the welding nozzle is exchanged or the inclination of the welding nozzle is corrected if the inclination of the welding nozzle determined by means of the inclination sensor deviates from a predetermined value.For example, it is provided that a position of the welding nozzle with respect to the X axis and the Y axis of the three-dimensional coordinate system is corrected in a robot controller of the robot when the measurement spot exceeds the outer circular mark to the outside.The described solution enables in particular a calibration and in particular also an adjustment of the laser build-up welding device.The described solution enables in particular a control of the welding nozzle with respect to a wear of bores of the multi-jet powder nozzle from which the powder jet exits. The optical recognition allows the characteristic of the powder beam focus to be measured easily and quickly. In comparison with data from the database of previous tests, it is possible to infer the wear state of the nozzle and, if appropriate, exchange measures can be initiated. In addition, it is possible to predict the next exchange time on the basis of the evaluation of previous data sets. This is referred to as predictive maintenance.The device additionally advantageously measures the powder mass flow at short time intervals. As a result, changes during a starting behavior, a closure of a powder line or problems of the powder supply before the process begins are recognized, since a comparison with previous measurement curves of the same material from the database advantageously takes place. The powder mass flow can also be set in advance to a specific value, wherein the device determines the point in time at which the mass flow is constantly in a defined tolerance range. This can now be used as a waiting time before the welding for the process. This ensures a uniform weld seam height, whereby less scrap, a higher quality and overall a stabilization of the welding process is achieved.Furthermore, with the aid of the inclination sensor and distance sensor, a rotation or displacement of the welding nozzle or of the entire laser welding head can be detected as soon as a predefined reference point is approached. This identifies both an adjustment of the robot axes due to vibrations in the process and a previous collision of the robot. As a result, long-term fault finding and rejects in production can be prevented and the shutdown of the plant can be shortened. A new welding nozzle or the entire laser welding head can also be adjusted to a predefined desired ideal position with little time expenditure, which considerably simplifies the otherwise long calibration method of the machining head. In this way, a height error of a generated weld is effectively and easily corrected.On the basis of the measurement data and the database it is possible to monitor the wear state of the components. Furthermore, maintenance intervals or points in time can be found, which give the user instructions for checking the components. The database additionally advantageously serves as a knowledge store, as a result of which the operation of the installation, i.e. of the laser deposition welding device, becomes less dependent on the experience of an installation operator.The described solution has a simple design, enables detection of collision travel and a rotation of the laser welding head or a displacement of the welding nozzle in the laser welding head, measurement of the powder mass flow or its partial flows at short intervals for creating a run-on curve with which wear or errors of the powder feed components can be detected and the time for a constant powder mass flow can be determined, and digital evaluation of the state data with the aid of a database. As a result, maintenance intervals of components can be determined reliably and early and wear predictions can be made.The described solution also offers a simple expansion possibility, in particular by integrating further sensor systems, in particular on a single-board computer of the device.Exemplary embodiments of the invention are explained in more detail below with reference to drawings.The following are shown: FIG. 1 schematically shows a laser deposition welding device, FIG. 2 schematically shows a laser welding head, FIG. 3 schematically shows a mode of operation of a welding nozzle, FIG. 4 schematically shows a comparison of an ideal welding nozzle with a worn welding nozzle, FIG. 5 schematically shows a dynamic profile of a powder mass flow, FIG. 6 schematically shows a micrograph comparison, FIG. 7 schematically shows a device for checking a powder injection device of the laser build-up welding device, FIG. 8 schematically shows a program flow diagram of an overall sequence of a method for checking the powder injection device of the laser build-up welding device, FIG. 9 schematically shows a first test device for checking a powder jet caustic and a powder mass flow, FIG. 10 schematically shows an edge recognition in an image, FIG. 11 schematically shows a dynamic profile of a powder mass flow in a normal state and during wear, FIG. 12 schematically shows a flow diagram of a subroutine of the method from FIG. 8, FIG. 13 schematically shows a second test device for determining a position of a multi-jet powder nozzle, FIG. 14 schematically shows a further illustration of a laser welding head, FIG. 15 schematically shows an extension of the second test device, FIG. 16 schematically shows a flow diagram of a subroutine of the method from FIG. 8, and FIG. 17 schematically shows a profile of a powder beam focus diameter over time.Corresponding parts are provided with the same reference numerals in all figures.With reference to FIGS. 1 to 17, a device 1 and a method for checking, in particular, a laser deposition welding device 3, in particular a powder injection device 2 of the laser deposition welding device 3, are described below.FIG. 1 shows an exemplary schematic illustration of the laser deposition welding device 3. it has as essential components a laser welding head 4 with a welding nozzle 5, which is fastened via a ball joint 6 shown in FIGS. 2 and 14 to a robot 7, which has in particular three translatory and three rotational degrees of freedom or at least three translatory and three rotational degrees of freedom. Furthermore, the laser build-up welding device 3 has the powder injection device 2. The welding nozzle 5 has a multi-jet powder nozzle 8 of the powder injection device 2, which nozzle is shown in more detail in FIG. 3, for discharging a powder jet PS of a powder conveyed by means of a powder conveyor 9 of the powder injection device 2.In the following, first some features of the device 1 and of the method for checking the powder injection device 2 are described in summary. Next, a more detailed description will be given of the examples shown in the figures.The device 1 schematically shown in FIG. 7 for checking the powder injection device 2 has a first checking device P 1 for checking a powder jet caustic, in particular a powder jet focus diameter PD of the powder jet PS shown in FIGS. 4 and 10, and a powder mass flow PM. The apparatus 1 furthermore has a second test apparatus P 2 for ascertaining a position of the multi-jet powder nozzle 8.The first test device P 1 has a camera 10, a load cell 11, a collecting tray 12 for collecting powder sprayed through the multi-jet powder nozzle 8, an illumination unit 13 designed in particular as an LED, and a housing 14, in which the camera 10, the illumination unit 13, the load cell 11 and the collecting tray 12 are arranged on the load cell 11, as shown in FIG. 9. The housing 14 has an opening 15 for arranging the welding nozzle 5. A camera focus of the camera 10 is aligned horizontally with a powder jet focus region in the housing 14, in which a powder jet focus PF of the powder jet PS is positioned when the welding nozzle 5 is arranged at the opening 15 and the powder jet PS is discharged. The illumination unit 13 is aligned with the powder beam focus region.The second test device P 2 has an inclination sensor 16 for determining an inclination of the welding nozzle 5 and a distance sensor 17 for determining a distance A of the welding nozzle 5 from a reference plane RE, which are arranged on an underside of a sensor holder 18, which can be fastened to the welding nozzle 5 in a positively centered manner, as illustrated in FIG. 13. The distance sensor 17 is arranged on the sensor holder 18 in such a way that, in the state in which the sensor holder 18 is fastened to the welding nozzle 5, it is positioned on an axis of rotation, in particular axis of rotational symmetry, of the welding nozzle 5.In one embodiment, the second inspection device P 2 also has a marking plate 19 with two coaxial circular markings M 1, M 2 with different diameters. The markings M 1, M 2 are in particular formed as a engraving.In the method for checking the powder injection device 2 of the laser deposition welding device 3 by means of the device 1, the powder jet additives and the powder mass flow PM are checked by means of the first checking device P 1 by the welding nozzle 5 being moved by means of the robot 7 to a predetermined, in particular first, reference point at which the welding nozzle 5 docks on the opening 15 of the housing 14, the powder is conveyed, a weight of the collecting tray 12 filling with the powder is dynamically measured and stored by means of the load cell 11 and a temporal change in the powder mass flow PM is thereby detected, the powder jet focus PF is illuminated by means of the illumination unit 13, an image or video of the powder jet additives is recorded by means of the camera 10, and weight values measured by means of the load cell 11 and the image or video recorded by means of the camera 10 can be evaluated. For this purpose, the housing 14 is arranged, for example, on a processing table 20 shown in FIG. 1, in particular a rotary tilting table, of the laser build-up welding device 3.Furthermore, the position of the multi-jet powder nozzle 8 is determined by means of the second test device P 2 by the sensor holder 18 being fastened in a positively centered manner to the welding nozzle 5, the welding nozzle 5 being moved to a predetermined, in particular second, reference point above the reference plane RE, the distance A of the welding nozzle 5 from the reference plane RE being determined by means of the distance sensor 17 and the inclination of the welding nozzle 5 being determined by means of the inclination sensor 16 by a determination of a respective acceleration in all three spatial axes X, Y, Z of a three-dimensional coordinate system and a respective rotation about all three spatial axes X, Y, Z, i.e. about the rotational angles α, β, γ. The second reference point may correspond to or deviate from the first reference point. The reference plane RE is formed here, for example, by the processing table 20.In one embodiment of the method, the marking plate 19 is fastened in an accurate position on a table, in particular on the processing table 20. The welding nozzle 5 is moved to a predetermined, in particular third, reference point above the marking plate 19, wherein the reference point is predetermined such that the powder jet focus PF lies on the marking plate 19. This third reference point may correspond to the first and / or second reference point or may deviate therefrom. Pilot lasers 21 of the welding nozzle 5, which are aligned such that pilot laser beams of the pilot lasers 21 intersect in the powder beam focus PF, in particular within the powder beam focus diameter PD, are switched on. These pilot lasers 21 are also referred to as cross lasers. A position of a measurement spot generated by the pilot lasers 21 on the marking plate 19 with respect to the two coaxial circular markings M 1, M 2 is evaluated.In one embodiment of the method, the powder beam focus PF is measured by means of edge detection in the image or video recorded by means of the camera 10.In one embodiment of the method, a respective partial powder mass flow is checked by successively conducting only one partial powder mass flow by means of a powder divider 22 to one of a plurality of nozzle openings 23 of the multi-jet powder nozzle 8. In the example according to FIG. 1, the powder divider 22 is designed as a 3-jet divider. Thus, three partial powder mass streams can be generated. The multi-jet powder nozzle 8 accordingly has in particular three nozzle openings 23.For example, it is provided that the welding nozzle 5 is exchanged when the powder jet caustic and / or the powder mass flow PM and / or at least one powder partial mass flow deviate from a respective specification.For example, it is provided that a position of the welding nozzle 5 relative to a nozzle holder 24 holding the welding nozzle 5 is corrected with respect to the Z axis Z of the three-dimensional coordinate system when the distance A of the welding nozzle 5 from the reference plane RE determined by means of the distance sensor 17 deviates from a predetermined value.For example, it is provided that the welding nozzle 5 is exchanged or the inclination of the welding nozzle 5 is corrected if the inclination of the welding nozzle 5 determined by means of the inclination sensor 16 deviates from a predetermined value.For example, it is provided that a position of the welding nozzle 5 with respect to the X axis X and the Y axis Y of the three-dimensional coordinate system is corrected in robot control of the robot 7 when the measurement spot exceeds the outer circular mark M 2 outward.The problems underlying the solution described here and the solution are described in detail below with reference to FIGS. 1 to 17.In metal laser build-up welding, there are many factors that affect the process in terms of manufacturing quality. In addition to parameters such as laser power, travel speed and system settings, which must be matched to one another in advance, a functioning system technique is also a basic prerequisite in order to ensure a stable build-up welding process.The installation used, i.e. laser deposition welding device 3, is schematically shown in FIG. 1. It has a laser beam source 25, for example in the form of a diode laser, the powder conveyor 9, which is in particular designed as a plate powder conveyor, and the robot 7 with a robot arm, which realizes the necessary travel movements. The robot 7 has, for example, a linear unit 30 or is arranged thereon. By means of the linear unit 30, the robot 7 is linearly movable, for example, in the direction of the X axis X and / or the Y axis Y of the three-dimensional coordinate system.A substrate SB is placed on the processing table 20, which is in particular configured as a rotary tilting table. The laser beam source 25 generates a laser beam LS, which is guided into a processing optical unit 27 by means of a light guide cable 26. In the processing optics 27, the laser beam LS is focused on the substrate surface with the focal distance of the welding nozzle 5 and the substrate SB set. With the aid of the multi-jet powder nozzle 8, also referred to as multi-jet welding nozzle, a protective gas is supplied via a protective gas supply 28 and the powder mass flow PM realized by the powder conveyor 9 is supplied to the welding process via a process gas and powder supply 29, wherein the powder is melted by the laser beam LS and is applied in a targeted locally materially bonded manner. In this case, the powder is transported from the powder conveyor 9 to the welding nozzle 5 by means of a transport gas or process gas, for example via a line about 15 m to 20 m long, which changes in its shape in accordance with a respective position of the laser welding head 4.FIG. 2 shows, as an overview, a schematic diagram of the laser welding head 4, also referred to as a laser machining head. Furthermore, the ball clamping, i.e. the ball joint 6, is shown as a connection of the laser welding head 4 to a robot flange 31 of the robot arm of the robot 7. At the lower end of the laser welding head 4 there is the welding nozzle 5, which is secured to the laser welding head 4 in a rotationally secure manner.In detail, FIG. 3 shows the mode of operation of the welding nozzle 5 and the relationship of powder beam focus PF and laser beam focus LF. The laser beam LS emerges centrally from the welding nozzle 5 and impinges on the surface of the substrate SB in the laser beam focus LF. Furthermore, protective gas flows out centrally from the welding nozzle 5 via the protective gas supply 28 and protects a melt bath SA formed from oxygen.Laterally, the powder mass flow PM, divided into individual jets, exits the welding nozzle 5. The focal point of the three individual beams of the powder beam PS is likewise located on the substrate surface. Ideally, the center of powder beam focus diameter PD and laser focus diameter exactly coincides.A machining direction for forming a weld seam SN is schematically illustrated by means of a directional arrow RP. Furthermore, a heat influence zone WZ is shown in the substrate SB.In general, in laser build-up welding tests, in spite of the same initial conditions, for example travel paths, laser power and / or powder mass flow PM, different welding results can result. In a series production, for example when repairing forming tools, a search is made as a reaction to a manufacturing deviation for a cause which is very time-consuming due to a large number of influencing factors.A main cause of a varying quality, which has an effect on component properties and / or accuracy, is an inadequate build-up height of the individual welding tracks, which result in a position arranged at a defined offset with respect to one another. If the actual build height of the layer is smaller than the preset offset of the individual layers in the Z-axis direction of the three-dimensional coordinate system in the robot program, this results in an additional reduction in the build height of the component to be manufactured, since the laser beam LS is now outside the focus range. The result are melt sprays which lead, for example, to pores in the component, to a poorer surface or to termination of the welding process. The result is waste and / or a collision with the welding nozzle 5, which can lead to damage.The factors which contribute to a too low build height are explained below.1. Wear of the multi-jet powder nozzle 8:The multi-jet powder nozzle 8 of the laser welding head 4 has a directed supply of the individual partial powder jets to a focal point which has a defined diameter and is located on the substrate surface. The abrasive action of the powder particles and a wear resulting therefrom in bores of the multi-jet powder nozzle 8 mean that the diameter of the individual partial powder jet becomes wider after the exit. The widened partial powder jets result in poorer powder jet caustic and an increased powder jet focus PF, so that less powder is melted in percent in the melting bath SA. As a result, a powder utilization rate and the build-up height decrease.In FIG. 4, an ideal welding nozzle 5 is shown schematically on the left and a worn welding nozzle 5 on the right. In the ideal welding nozzle 5, the powder beam focus PF and the laser beam focus LF are similar. In the worn welding nozzle 5, the powder beam focus PF is substantially larger than the laser beam focus LF.2. Dynamic change of the powder mass flow PM:The powder mass flow PM is set by means of the powder conveyor 9 before the beginning of the welding process, since no direct monitoring or regulation takes place in the current process. Therefore, the powder mass flow PM that has been set must already be checked beforehand for its constancy. In the case of brief deviations in the powder mass flow PM, defects in particular can occur in the component to be additively manufactured, since the powder mass flow PM directly influences the build height and thus the height offset in the Z-axis direction of the three-dimensional coordinate system, which is defined in advance in the robot code. In addition, voids may arise and the laser beam LS may come out of focus, so that the component is to be assigned to the waste and / or the additive structure collides with the welding nozzle 5, which may lead to damage.To solve this problem, a quantity of powder per unit time, for example one minute, has been measured statically for checking up to now. It is thus possible to determine the powder mass flow PM by calculation. In this context, the term static describes a measurement method in which only the difference between the starting point and the end point is compared. However, this method does not consider the dynamic profile of the powder mass flow PM and also inflow or stabilization times of the components, which can result, for example, in the case of a high line length, a bending of the line and / or due to discontinuities in the powder delivery.FIG. 5 shows, by way of example, the dynamic profile of the powder mass flow PM over time t with fluctuations. A start-up range AB and a subsequent measuring range MB and a target range SO are shown, within which the powder mass flow PM is to lie in the measuring range MB. This figure relates to the ideal mass flow of 18 g / min. The target range SO is between 17.5 g / min and 18.5 g / min in order to ensure process safety. The increase at the beginning is to be explained by the stabilization and lead-in times.In the conventional static measurement, a brief underrunning or exceeding of the desired range SO cannot be detected. In addition, it is not possible to detect the point in time at which the powder mass flow PM is constantly in the desired range SO.In contrast, the solution described here enables a dynamic measurement with a plurality of measurement intervals per unit time and thus a comparison with previously recorded curves, so that deviations can be detected with the same setting of the powder conveyor 9 and the same positioning of the line. Thus, conclusions can be drawn about the wear of the individual components, for example of the powder line, which is not possible hitherto, in particular with the conventional measurement method.3. Displacement of the laser welding head 4 with respect to a virtual model:For a stable laser build-up welding process, the robot 7 must be calibrated at time intervals. This serves for the precise positioning of the robot attachments in space. The background is that the real spatial positions of the system components must correspond to the virtual model of the system, since in the CAM software the travel movements of the laser welding head 4 during build-up welding are created with this model.The laser welding head 4 is connected to the robot 7 by the ball joint 6, which can be displaced and / or rotated by vibrations or by a collision during the course of the process. The resulting malposition of the laser welding head 4 cannot be detected during the ongoing production operation. Particularly in the case of complex travel paths of the laser welding head 4, a large distance deviation of the welding nozzle 5 from the component is subsequently produced. The result is waste and / or a collision of the welding nozzle 5 with the component to be welded, which can lead to damage.4. Displacement of the welding nozzle 5 resulting from the malposition in the laser welding head 4:In the event of a collision of the welding nozzle 5 and the substrate SB, the welding nozzle 5 can be displaced in the laser welding head 4 in the X, Y and Z axis directions of the three-dimensional coordinate system. In this case, powder beam focus PF and laser beam focus LF deviate from one another, as a result of which an uneven heat influence zone WZ is realized in the substrate SB and a lower powder application takes place.In FIG. 6, an exemplary micrograph of an ideal weld seam SN is shown on the right and, in comparison thereto, a micrograph of a poor weld seam SN is shown on the left, in each case at the top in a plan view and at the bottom in a sectional illustration. As can be seen, in the left-hand illustration, the two focuses PF, LF are not located one above the other, but offset from one another. As a result, the powder utilization rate is lower. Furthermore, the required volume energy density is no longer correct, since the laser beam LS melts a smaller powder volume in the laser beam focus LF and the volume energy density is thus higher. The result is pores due to evaporation. The powder which is applied outside the laser beam focus LF does not absorb sufficient laser energy for melting, pores are formed as a result of unmelted powder. As a result, the heat influence zone WZ and the welding track become non-uniform and the component becomes defective, which leads to rejects.In particular, the solution described here attaches at this point. The solution to the problem is monitoring and error detection with the aim of efficiently eliminating the above-mentioned error sources, the correction of which is currently based on the experience knowledge of the plant operators or long measurement methods. An efficient elimination of these sources of error has not yet existed. For example, when a welding nozzle 5 is changed, the robot arm needs to be re-measured in the Z-axis direction of the three-dimensional coordinate system, which means a longer standstill of the facility.In the solution described here, it is provided in particular that the listed influencing factors and associated characteristic numbers are determined by measurement prior to the production process and used during maintenance. This ensures a permanently constant quality, reduces waste and reduces a possible risk of collision between the welding nozzle 5 and the component.The solution described here ensures the process stability of laser deposition welding, wherein the solution includes in particular approaches for avoiding a fluctuating and / or too low welding track height.By means of the described device 1 and the described method, which are schematically illustrated by way of example in FIG. 7, it is possible in particular to detect and correct the four errors described above. This is effected in particular with the aid of different measured values and parameters, which are stored in a database 32 of the device 1 for quality assurance.FIG. 7 shows the schematic structure of the device 1. in the example shown, the device 1 has a computer 33 which is connected to the database 32. In this computer 33, the respective measurement is started, in particular by an operator BD. In the example shown, the device 1 furthermore has a single-board computer 34 connected to the computer 33, which in this example accesses the camera 10 and load cell 11 directly. In the example shown, the inclination sensor 16 and distance sensor 17 are connected to a controller 35, in particular a controller board. The controller 35 reads out the signals of the inclination sensor 16 and distance sensor 17 and forwards them to the single-board computer 34 in the example shown. The evaluation, in particular a comparison with respective values stored in the database 32, is carried out in particular in the computer 33.The dashed lines represent, on the one hand, the component for measuring the powder mass flow PM and the powder jet focus diameter PD, i.e. the first test apparatus P 1, and, on the other hand, the component for ascertaining the position of the multi-jet powder nozzle 8, i.e. the second test apparatus P 2.A possible rough configuration of the method, in particular for the detection and removal of all the error influencing factors mentioned, is illustrated in FIG. 8. First, a start S of the method takes place. Thereafter, for example, a position calibration and adjustment of the welding nozzle 5 is carried out first in a first overall step GS 1, then a calibration and, for example, an adjustment of the powder mass flow PM and a determination of the powder jet caustic system are carried out in a second overall step GS 2, and a data evaluation for a prediction of an exchange and / or maintenance time of the components is carried out in a third overall step GS 3. This is also referred to as predictive maintenance. End E of the method is then reached.In this case, the position calibration and adjustment of the welding nozzle 5 in the first overall step GS 1 takes place in particular on the basis of the subroutine shown in FIG. 16, and the calibration and, for example, adjustment of the powder mass flow PM and the determination of the powder jet caustic, in particular of the powder jet focus diameter PD, in the second overall step GS 2 take place in particular on the basis of the subroutine shown in FIG. 12.FIG. 9 schematically shows an example of the first test device P 1 for checking the powder jet caustic and the powder mass flow PM. As described above, the robot 7 travels to the first reference point. The welding nozzle 5 in this case adheres to the housing 14, in particular to its opening 15, and begins to convey powder. During the measurement, the load cell 11 dynamically measures and stores the weight of the filling collecting pan 12.Furthermore, the camera 10 with the camera focus horizontally directed at the powder beam focus PF records an image or video of the powder beam caustic. The illumination unit 13, which is in particular designed as an LED, serves here to illuminate the powder beam focus PF.Advantageously, the entire measuring device is located in the, in particular closed, housing 14, which in particular has a filter that prevents the powder from leaking into the environment.In the example shown, a protective glass 36 is also arranged in the housing 14, which protects the electronic components from the electrically conductive powder. By means of the protective glass 36, an interior space of the housing 14 is divided into two sections A 1, A 2 separated from one another by the protective glass 36. The collecting tray 12 is located in the first section A 1, to which the welding nozzle 5 is docked via the opening 15 and into which the powder flows. The camera 10 and the illumination unit 13 are located in the second section A 2. In the example shown, the load cell 11 is located in the first section A 1 with a region arranged below the collecting tray 12 and an electronics region of the load cell 11 is located in the second section A 2.The values of the load cell 11 and the images or videos of the camera 10 are evaluated in particular with the aid of the single-board computer 34 on the basis of a program which, in particular with the aid of the respective recorded image, directly measures the powder beam focus PF by edge detection. The values can then be displayed, for example, on a display unit, for example of the computer 33.The method of operation for determining the powder focus diameter PD is described below. The powder jet caustic can draw conclusions as to the wear state of the welding nozzle 5, in particular of the multi-jet powder nozzle 8.FIG. 10 shows the sequence of image recognition of an image or video or single image from the video recorded by the camera 10. The image or video is recorded when the powder mass flow PM is in a stable range.On the left in FIG. 10, the recorded and still unprocessed image is shown, which is blurred. Gray scale analysis is performed, sharpening the image and eliminating noise as shown in the middle of Figure 10. Edges KT are then recognized, in particular by means of software, i.e. cat recognition is carried out and best-fit lines are drawn into the image, as shown on the right in FIG. 10. Thereafter, the measured line distance of the lines, i.e. of the depicted compensation straight lines, is measured in the powder beam focus PF and the powder beam focus diameter PD is thereby determined. In the case of a new welding nozzle 5, in particular multi-jet powder nozzle 8, the line spacing of the lines in the powder jet focus PF determined in this way, i.e. the determined powder jet focus diameter PD, can be stored, for example, in the database 32 as a reference. In addition, the recorded image is advantageously stored together with the measured powder beam focus diameter PD in the database 32, for example in order to be able to check the result manually.When the powder jet focus diameter PD is larger than a predetermined value, the welding nozzle 5 needs to be replaced. This value is advantageously determined and stored as a limit value, in particular stored in the database 32. For example, this value is determined at one or more worn welding nozzles 5.By way of the temporal comparison with previously determined powder beam focus diameters PD, a prediction for an exchange time AT is also possible. This is referred to as predictive maintenance.The described image evaluation can be extended, for example, by a downstream artificial intelligence, which is trained for the evaluation of the images. This can be trained, for example, by means of old images in the database 32 and / or by means of newly recorded images from measurements carried out. As a result, special functions, for example a detection of clogged individual nozzles, in particular nozzle openings 23, of the multi-jet powder nozzle 8, can be added, for example.The second function is the powder mass flow measurement of the total mass flow or of individual partial flows. By changing the powder feed from the powder divider 22 to the three individual powder jets, an individual partial powder jet can be measured, by means of which one third of the total mass flow is conveyed into the calibration unit of the powder jet PS. In this way, blockages of the feed bores in the multi-jet powder nozzle 8 or generally uneven powder mass flows of the individual jets are detected. In addition, the measurement with the load cell 11 allows a material-independent mass flow measurement, since no reflection properties need to be taken into account here.FIG. 11 shows the multiple value of a dynamic measurement of the powder mass flow PM at small time intervals. A normal curve K 1 of the powder mass flow PM and a curve K 2 of the powder mass flow PM during wear are shown. A time T 1 of reaching the target range SO can be accurately determined. In addition, the profile of the powder mass flow PM after the startup time is determined, so that a time T 2 is likewise detected, from which the powder mass flow PM is constantly in the setpoint range SO. In comparison with earlier curves from the database 32, it is likewise possible to draw a conclusion as to whether parts of the powder feed system are worn out if setting parameters such as the disk rotational speed of the powder conveyor 9 are the same and the powder mass flow PM after the startup time is constantly lower than in the case of previous measurements.FIG. 12 shows a possible sequence of the powder mass flow measurement for determining the described relationship of time t and powder quantity and for measuring the powder jet focus diameter PD.After the start S, in a first step S 1, the first test device P 1, also referred to as calibration unit, more precisely the housing 14, is mounted, for example, on the processing table 20. Subsequently, in a second step S 2, the welding nozzle 5 is moved by means of the robot 7 to the predetermined first reference point and is thereby docked to the housing 14, more precisely to its opening 15. In a third step S 3, the powder is conveyed and the measurement of the powder mass flow PM is started. In a fourth step S 4, the waiting time and the measurement range time are maintained. In a fifth step S 5, the powder jet caustic is recorded by means of the camera 10 and the powder delivery is ended. In a sixth step S 6, the image recorded by the camera 10 is evaluated with the edge recognition. Furthermore, a comparison with database values takes place, in particular with respect to the powder mass flow PM and the powder beam focus diameter PD. In a seventh step S 7, the evaluated image and the powder mass flow curve are output. In an eighth step S 8, the determined values are stored in the database 32; in a ninth step S 9, a check is made as to whether a predefined tolerance range has been observed. If n, then in a correction step KS, correction measures are taken, and then the process proceeds to the third step S 3, i.e. steps S 3 to S 9 are repeated. If yes, then in a tenth step S 10 the first inspection device P 1, more precisely the housing 14, is removed from the processing table 20.FIG. 13 schematically shows the second test device P 2 for determining the position of the multi-jet powder nozzle 8, in particular for checking and calibrating the welding nozzle 5 and thus also the multi-jet powder nozzle 8. In the example shown, it also has an upper plate 37, which secures this structure, i.e. the sensor holder 18 with the distance sensor 17 and inclination sensor 16 arranged thereon, against undesired detachment. The connection of the top plate 37 to the sensor holder 18 is effected in the example shown by means of screws 38.The distance sensor 17 is arranged below the welding nozzle 5 on the nozzle rotation axis on the sensor holder 18. On the same Z-plane, the inclination sensor 16 is arranged on the sensor holder 18, which measures both the rotation and the acceleration in all three spatial axes of the three-dimensional coordinate system. The inclination sensor 16 is in particular designed as a gyroscope.The two sensors 16, 17 are read out by the controller 35, for example by an arabino controller. The read-out data are displayed directly, for example, on a display 39 of the second test device P 2, which is arranged on the sensor holder 18 in the example shown, and are also sent to the single-board computer 34, for example.For the described nozzle position determination, this structure, i.e., the second inspection device P 2 mounted on the welding nozzle 5, is moved to the second reference point by the robot 7 and the measurement is started. The second inspection device P 2 enables the detection of a rotation by collision of the robot 7, in particular the welding nozzle 5, or a displacement of the welding nozzle 5 in the Z-axis direction of the three-dimensional coordinate system.The distance sensor 17 detects the distance A from the reference plane RE and thus a displacement in the Z-axis direction that may be present. The reference plane RE is, for example, the processing table 20. The inclination sensor 16, which is in particular designed as a gyroscope, detects a possible rotation of the entire laser welding head 4 with the aid of the solid angles, i.e. the rotation angles α, β, γ. Deviations from an ideal position of the laser welding head 4, which is stored in the database 32 and is set in the virtual model, can thus be recognized quickly and reliably without the need for an entire robot calibration. Furthermore, even after a necessary replacement of the welding nozzle 5, the proper installation of the welding nozzle 5 in the Z-axis direction of the three-dimensional coordinate system can be controlled.FIG. 14 schematically shows a further illustration of the laser welding head 4; it can be seen from this that the welding nozzle 5 is connected to the laser welding head 4 in a rotationally fixed manner via the nozzle holder 24. In the example shown, the nozzle holder 24 is fastened to the laser welding head 4 in a clamping plane 40 by means of a clamping plate 41.After compensating for the rotation of the laser welding head 4 if this was required and after setting the correct distance A in the Z-axis direction, i.e. after a change ΔZ in the Z-axis direction has been made, for example by a corresponding displacement of the welding nozzle 5 in the nozzle holder 24 if this was required, the alignment of the welding nozzle 5 in the X-axis direction and Y-axis direction of the three-dimensional coordinate system is still a missing component for an exact restoration of the position of the welding nozzle 5.FIG. 15 shows an extension of the second inspection device P 2, i.e. in particular of the calibration unit of the welding nozzle 5. as already described, the second inspection device P 2 has in this extension the marking plate 19 with the two coaxial circular markings M 1, M 2, which are in particular designed as engraving, with different diameters, illustrated on the left in a plan view from the top and on the right in a side view.In the example shown, the marking plate 19 has four bores 42. It is or is fastened in a positionally accurate manner on the processing table 20, in particular by means of these bores 42. The robot 7 moves the laser welding head 4 with the welding nozzle 5 to the third reference point, which corresponds in particular to the focal point, and both pilot lasers 21 of the welding nozzle 5 are switched on, as shown on the right in FIG. 15.The pilot lasers 21 are arranged within the welding nozzle 5 similar to the feed bores, i.e. in particular similar to the nozzle openings 23, so that the intersection of both pilot laser beams is exactly in the powder beam focus diameter PD with the focus distance set. The radiation of the pilot lasers 21 is harmless to the human eye. An operator BD can now evaluate the size and position of the measurement spot with respect to the markings M 1, M 2. In the ideal case, the measurement spot corresponds exactly to the inner circle, i.e. to the inner first marking M 1. If the measurement spot exceeds the second circle, i.e. the outer second marking M 2, the permissible deviations in the X-axis direction and the Y-axis direction of the three-dimensional coordinate system are exceeded and the position must be adjusted, for example, in the robot controller. Alternatively or additionally, in order to correct the position of the welding nozzle 5 in the X-axis direction and / or in the Y-axis direction, for example, the nozzle holder 24 can be correspondingly displaced on the laser welding head 4, in particular in the clamping plane 40, for example by releasing the clamping plate 41, displacing the nozzle holder 24 in the described manner and re-fastening the clamping plate 41.Overall, this method advantageously replaces the entire long calibration of the robot axes, since the position of the welding nozzle 5 is advantageously completely determined in all axes X, Y, Z of the three-dimensional coordinate system and all rotational angles α, β, γ and can advantageously be brought back into the previous ideal position, in particular stored in the database 32.A possible embodiment of the method sequence for determining the position of the welding nozzle 5 and thus of the multi-jet powder nozzle 8 and in particular for calibrating the laser welding head 4 or the multi-jet powder nozzle 8 is schematically illustrated in FIG. 16.After the start S, in a first step S 1, the first component of the second test device P 2, i.e. the sensor holder 18 with inclination sensor 16 and distance sensor 17, is first mounted on the welding nozzle 5 and the second reference point is approached. In a second step S 2, the inclination and distance values are measured, stored and compared with values in the database 32. In a third step S 3, the measured inclination and distance values are displayed on the display 39. In a fourth step S 4, it is checked whether a predefined tolerance range is complied with. If n, in a first correction step KS1, correction actions are taken to correct the rotational angles α, β, γ and / or the Z-axis position where necessary, respectively, and the flow then proceeds to the second step S2. If yes, i.e. if the predefined tolerance range is complied with, in a fifth step S 5 the first component of the second test device P 2, i.e. the sensor holder 18 with inclination sensor 16 and distance sensor 17, is dismounted from the welding nozzle 5, the marking plate 19 is mounted on the machining table 20, the pilot lasers 21 are switched on and the third reference point is approached. In a sixth step S 6, the measurement spot is monitored with respect to the two markings M 1, M 2. In a seventh step S 7, it is checked whether the tolerance range in this respect is complied with, i.e. in particular whether the measurement spot does not exceed at least the second marking M 2 outwards. If n, i.e. if the tolerance range is not complied with, in a second correction step KS 2, correction measures are carried out with respect to the position of the welding nozzle 5 and thus of the multi-jet powder nozzle 8 in the X-axis direction and / or Y-axis direction of the three-dimensional coordinate system, and the process then continues with the sixth step S 6. If yes, i.e. if the tolerance range is maintained, the marking plate 19 is removed from the processing table 20 in an eighth step S8. End E is then reached.The results recorded by the two individual components of the device 1, in particular by the two test devices P 1, P 2, are stored in the database 32 in particular by means of the computer 33. In comparison of these results with earlier data sets, the change in the state of the machine, i.e. of the laser build-up welding device 3, in particular the change in the position of the laser welding head 4 and the change in the powder jet caustic, can be detected. Overall, the solution described achieves a transparent detection of the state of the laser build-up welding device 3 even without many years of experience. In addition, a defined desired state can be restored.The database 32 is advantageously incorporated into maintenance software which gives the user of the laser deposition welding device 3 an overview of the state of all plant components. This makes sense because, up to now, there have been only experience values for the wear of the multi-jet powder nozzle 8 and the position deviation of the welding nozzle 5 with the multi-jet powder nozzle 8 integrated therein, but no defined characteristic values. By evaluating the data sets, the necessary component exchange and a necessary position calibration of the laser welding head 4 can also be predicted and scheduled as maintenance. This reduces unscheduled stoppages of the laser deposition welding device 3 due to complex fault finding and also increases productivity by stabilizing the welding process. The maintenance operations carried out are advantageously subsequently logged in the software and can also be planned early before a failure.In general, the described solution allows control of the welding nozzle 5 with respect to the wear of the feed bores, i.e. in particular of the nozzle openings 23, of the multi-jet powder nozzle 8, from which the powder stream exits. The optical recognition allows the characteristic of the powder beam focus PF to be measured easily and quickly. In comparison with data from the database 32 of previous tests, it is possible to infer the wear state of the welding nozzle 5, in particular of the multi-jet powder nozzle 8, and optionally to initiate replacement measures. In addition, a prediction of the next exchange time AT is possible on the basis of the evaluation of previous data sets.The device 1 also measures the powder mass flow PM at short time intervals. As a result, changes during the starting behavior, a closure of the powder line and / or problems of the powder supply before the process begins are recognized, since a comparison with previous measurement curves of the same material from the database 32 takes place. The powder mass flow PM can also be set in advance to a specific value, wherein the device 1 determines the point in time at which the powder mass flow PM is constantly in a defined tolerance range. This can now be used as a waiting time before the welding for the process. This ensures a uniform weld seam height, whereby less scrap, a higher quality and overall a stabilization of the welding process is achieved.Furthermore, with the aid of the inclination sensor 16 and the distance sensor 17, a rotation or displacement of the welding nozzle 5 or of the entire laser welding head 4 can be detected as soon as a predefined reference point is approached. As a result, both an adjustment of the robot axes due to vibrations in the process and a previous collision of the robot 7 are detected. As a result, long-term fault finding and rejects in production can be prevented and the standstill of the laser build-up welding device 3 can be shortened. A new welding nozzle 5 or the entire laser welding head 4 can also be adjusted to a predefined desired ideal position with little time expenditure, which considerably simplifies the otherwise long calibration method of the laser welding head 4. In this way, the height error of the weld SN of FIG. 6 is effectively and easily corrected.On the basis of the measurement data and the database 32, it is possible to monitor the wear state of the components of the laser deposition welding device 3, in particular of the welding nozzle 5 with multi-jet powder nozzle 8, as shown in FIG. 17. Furthermore, maintenance intervals or points in time can be found, which give the user instructions for checking the components. The database 32 additionally advantageously serves as a knowledge store, as a result of which the operation of the laser deposition welding device 3 becomes less dependent on the experience of the system operator.FIG. 17 shows, by way of example, a profile of the powder jet focus diameter PD in the time profile represented as day d and an actual or predicted replacement time AT for replacing, in particular, the welding nozzle 5 when a predefined wear limit VG is exceeded. The illustrated profile of the powder beam focus diameter PD is, for example, completely a predicted profile or a profile actually determined until the predetermined wear limit VG is reached and thus the replacement time AT. The further course from the replacement time AT is a prediction of how the powder jet focus diameter PD would develop further if no replacement of the welding nozzle 5 were to take place.The device 1 has a simple structure. The solution described makes it possible to detect collision travel of the robot 7 and a rotation of the laser welding head 4 or a displacement of the welding nozzle 5 in the laser welding head 4. The described solution enables a measurement of the powder mass flow PM or of its partial flows at short intervals for establishing a run-on curve, with which wear or errors of the powder feed components can be detected and the time for a constant powder mass flow PM can be determined. Furthermore, the described solution enables a digital evaluation of the state data with the aid of the database 32. The described solution offers a simple expansion possibility by integrating further sensor systems on the single-board computer 34.

Claims

Device (1) for checking a powder injection device (2) of a laser application welding device (3), wherein the laser application welding device (3) has a laser welding head (4) with a welding nozzle (5) which is fastened via a ball joint (6) to a robot (7) which has three translatory and three rotational degrees of freedom, wherein the welding nozzle (5) has a multi-jet powder nozzle (8) of the powder injection device (2) for applying a powder jet (PS) of a powder conveyed by means of a powder conveyor (9) of the powder injection device (2), - having a first checking device (P1) with a camera (10) for checking a powder jet caustic and a powder mass flow (PM), characterized bya second checking device (P2) for determining a position of the multi-jet powder nozzle (8), wherein the first test apparatus (P1) comprises: - a load cell (11), - a collecting tray (12) for collecting powder sprayed through the multi-jet powder nozzle (8), - an illumination unit (13), and - a housing (14) in which the camera (10), the illumination unit (13), the load cell (11) and the collecting tray (12) are arranged on the load cell (11), wherein the housing (14) has an opening (15) for arranging the welding nozzle (5), wherein a camera focus of the camera (10) is aligned horizontally with a powder jet focus region in the housing (14), in which a powder jet focus (PF) of the powder jet (PS) is positioned when the welding nozzle (5) is arranged at the opening (15) and the powder jet (PS) is discharged, and wherein the illumination unit (13) is aligned with the powder jet focus region, and wherein the second test apparatus (P2) has: - an inclination sensor (16) for determining an inclination of the welding nozzle (5) and a distance sensor (17) for determining a distance (A) of the welding nozzle (5) from a reference plane (RE) which are arranged on an underside of a sensor holder (18) which can be fastened in a positively centered manner to the welding nozzle (5), wherein the distance sensor (17) is arranged on the sensor holder (18) in such a way that, in the state of the sensor holder (18) fastened to the welding nozzle (5), it is positioned on an axis of rotation of the welding nozzle (5).Device (1) according to claim 1, characterised in that the second test device (P2) has a marking plate (19) with two coaxial circular markings (M1, M2) with different diameters.Method for checking a powder injection device (2) of a laser deposition welding device (3) by means of a device (1) according to one of the preceding claims, wherein - the powder jet caustic and the powder mass flow (PM) are checked by means of the first checking device (P1) by the welding nozzle (5) being moved by means of the robot (7) to a predetermined reference point at which the welding nozzle (5) docks on the opening (15) of the housing (14), the powder is conveyed, a weight of the collecting tray (12) filling with the powder is dynamically measured and stored by means of the load cell (11) and a change over time in the powder mass flow (PM) is thereby detected, the powder jet focus (PF) is illuminated by means of the illumination unit (13), an image or video of the powder jet caustic is recorded by means of the camera (10), and weight values measured by means of the load cell (11) and the image or video recorded by means of the camera (10) are evaluated, and - the position of the multi-jet powder nozzle (8) is determined by means of the second test device (P2) by fastening the sensor holder (18) in a positively centered manner to the welding nozzle (5), the welding nozzle (5) being moved to a predetermined reference point above the reference plane (RE), The distance (A) of the welding nozzle (5) from the reference plane (RE) is determined by means of the distance sensor (17), and the inclination of the welding nozzle (5) is determined by means of the inclination sensor (16) by determining a respective acceleration in all three spatial axes of a three-dimensional coordinate system and a respective rotation about all three spatial axes.Method according to Claim 3, characterized in that the marking plate (19) is fastened in an accurate position on a table, the welding nozzle (5) is moved to a predetermined reference point above the marking plate (19), the reference point being predetermined such that the powder jet focus (PF) lies on the marking plate (19), pilot lasers (21) of the welding nozzle (5) which are aligned such that pilot laser beams of the pilot lasers (21) in the powder jet focus (PF) intersect within a powder jet focus diameter (PD) are switched on and a position of a measurement spot generated by the pilot lasers (21) on the marking plate (19) is assessed with respect to the two coaxial circular markings (M1, M2).Method according to Claim 3 or 4, characterized in that the powder beam focus (PF) is measured by means of edge detection in the image or video recorded by means of the camera (10).Method according to one of Claims 3 to 5, characterized in that a respective powder part-mass flow is checked by in each case only one powder part-mass flow being conducted successively by means of a powder divider (22) to one of a plurality of nozzle openings (23) of the multi-jet powder nozzle (8).Method according to one of Claims 3 to 6, characterized in that the welding nozzle (5) is exchanged if the powder jet caustic and / or the powder mass flow (PM) and / or at least one powder partial mass flow deviate from a respective specification.Method according to one of Claims 3 to 7, characterized in that the welding nozzle (5) is exchanged or the inclination of the welding nozzle (5) is corrected if the inclination of the welding nozzle (5) determined by means of the inclination sensor (16) deviates from a predefined value.

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