DEVICE, SYSTEM AND METHOD FOR CALIBRATING A LASER DEVICE

Description

[0001] The present invention relates to a device, a system and a method for calibrating a laser device configured to freely position a working laser beam in a predetermined working area.

[0002] 3D printing makes it possible to produce a wide variety of three-dimensional components with complex geometries. Three-dimensional workpieces are built up layer by layer. The build process is computer-controlled and uses one or more liquid or solid materials, designed according to predefined dimensions and shapes (CAD). Physical or chemical hardening or melting processes take place during the build process. Typical materials for 3D printing include plastics, resins, ceramics, and metals.

[0003] 3D printing is a generative or additive manufacturing process. The most important 3D printing techniques are selective laser melting (SLM) and electron beam melting (EBM) for metals, and selective laser sintering (SLS) for polymers, ceramics, and metals.

[0004] Another additive manufacturing process is selective melting and solidification. In this type of process, metal powder or metal wire is melted and solidified layer by layer, allowing for the creation of a three-dimensional component. Due to the locally limited energy input via a laser beam, the size of the resulting melt pool is small. This makes it possible to produce intricate structures. These processes are commercially available as Laser Engineered Net Shaping (LENS), Direct Metal Deposition (DMD), Laser Additive Manufacturing (LAM), Selective Laser Melting (SLM), or Laser Metal Deposition (LMD).

[0005] In selective laser sintering (SLS / LMF), a layer of powder material is applied to a build platform. The loose powder is melted at specific points by a laser beam. Depending on the material used, the powder particles are then bonded within the layer and to the layer below. Two fundamental development paths can be distinguished for the production of metallic components. Besides the direct solidification of metallic powder materials by laser radiation (direct metal laser sintering), the production of metallic components via a combination of SLS with plastic-coated metal powder and subsequent thermal treatment (IMLS) has become established early on.

[0006] Direct metal laser sintering (DMLS) uses either single- or multi-component metal materials. In particular, DMLS multi-component powders consisting of various alloying elements are used. The low-melting-point component contained in the powder is melted by a laser beam and flows around the high-melting-point component, which serves as the structure formator.

[0007] Electron beam melting (EBM) essentially follows the same process as laser-based methods. Loose metal powder, either in a powder bed or via a nozzle, or a wire, is melted at specific points and then solidifies into the desired shape. The energy required for this is supplied by an electron beam. The process usually takes place in a vacuum chamber flooded with inert gas.

[0008] Electron beam melting, similar to selective laser melting (SLM), involves the application of high energy that melts the build material. However, the energy is not supplied by a high-power laser, but rather by a powerful electron beam, which is deflected and positioned precisely using strong magnetic coils. The electron beam melting process must be carried out under high vacuum, which significantly limits the build volume of devices that utilize this technique.

[0009] In recent years, processes have been developed to improve the processing of single-component metal materials. These processes are commercially available, for example, under the name Selective Laser Melting (SLM).

[0010] In contrast to Selective Laser Sintering (SLS), Selective Laser Melting (SLM) introduces significantly more energy into the powder bed via a laser beam, resulting in a true molten material in the affected areas. This produces a more homogeneous object with higher density compared to the SLS process.

[0011] Laser cladding is a type of welding process in which a surface layer of almost any material is applied to a workpiece by melting and simultaneously depositing it. This can be done with powdered material, such as metal powder, or with a welding wire or strip. Laser cladding uses a high-power laser as the heat source, primarily a diode laser or fiber laser; previously, CO2 and Nd:YAG lasers were also used.

[0012] In laser cladding with powder, the laser heats the workpiece, usually in a defocused beam, and melts it locally. Simultaneously, an inert gas mixed with fine metal powder is introduced. At the heated area, the metal powder melts and bonds with the metal of the workpiece. In addition to metal powders, ceramic powder materials, especially hard materials, can also be used. Laser cladding with wire or strip works analogously to the process with powder, but with wire or strip as the filler material.

[0013] Accordingly, additive manufacturing processes utilize a powder bed, powder feeder, or wire feeder, whereby these starting materials are melted and subsequently solidified using a laser beam, electron beam, or plasma / electric arc. Furthermore, inert or active gases are used as process gases in additive manufacturing processes.

[0014] One goal of the aforementioned additive manufacturing processes is to ensure the most efficient energy input possible, so that a safe manufacturing process and high component quality are achieved.

[0015] These processes attempt to mitigate critical influences and processes during energy input through appropriate measures. In this context, the use of a substrate plate on which the component is fixed, process control under a protective gas atmosphere, or the application of new scanning strategies for exposing the powder with laser energy are known approaches.

[0016] German patent DE 10 2011 006 553 A1 discloses a method for determining the focus position or beam profile of a light beam using a pinhole aperture and a downstream detector. Instead of a single pinhole aperture, a perforated plate with multiple holes, each defining a measurement point, can also be used.

[0017] German patent DE 10 2009 016 585 A1 discloses a method and a device for calibrating an irradiation device, in particular a device for the additive manufacturing of components, in which an image intensifier plate is provided that is locally irradiated with energy-containing radiation. The image intensifier plate converts the radiation energy into detectable light, which is detected by a detector.

[0018] DE 10 2020 122 670 A1 describes a further device for calibrating an irradiation device, in particular a 3D printing device, in which detection elements are provided outside the working area to calibrate the position of a light beam. The detection elements can have openings behind which optical sensors for detecting the light beams are arranged. DE 10 2020 100 217 A1 describes a method for the automated beam positioning of a laser beam with respect to a nozzle of a laser processing head.

[0019] Documents US 2021 / 379665 A1 and US 2021 / 308771 A1 also represent the state of the art.

[0020] The object of the present invention is to provide a device and a method for calibrating a laser device, which are designed to freely position a working laser beam in a predetermined working area, and to arrange a working laser beam with a predetermined accuracy in a working area.

[0021] A further object of the present invention is to provide a device and a method for calibrating a laser system that enable high reproducibility. Furthermore, an object of the present invention is to provide an improved device and an improved method for additive manufacturing in order to produce components more easily, faster, and / or with higher quality.

[0022] Another object of the present invention is to provide an alternative method for additive manufacturing.

[0023] One or more of these problems are solved by features of the independent claims. Advantageous embodiments are specified in the dependent claims. According to the invention, a device for calibrating a laser device is provided, which is configured to freely position a working laser beam in a predetermined working area. This device comprises a sensor plate with one or more sensor fields for arrangement in a working area. a perforated plate gauge with several calibration openings, wherein the several calibration openings are each arranged in the area of ​​one of the several sensor fields, a control device for determining the relative position of the sensor fields to each other after exposure of the same through the calibration openings of the perforated plate gauge, a pilot laser device for providing a pilot laser beam along the beam path of the working laser beam in order to calibrate a laser device by scanning the pilot laser beam using the sensor fields.

[0024] When calibrating the laser device using sensor fields whose relative positions are determined, the perforated plate gauge can be positioned on or away from the sensor plate. Since the relative positions of the sensor fields are determined, the relative position of the pilot laser beam directed at one of the sensor fields can be determined relative to other positions of the pilot laser beam directed at the same or a different sensor field.

[0025] The laser device is preferably a laser unit of a device for the additive manufacturing of components. Alternatively, however, other laser devices, for example for laser cutting, laser drilling, or the like, can also be calibrated with the device according to the invention within the scope of the present invention. These devices have in common that a working laser beam of the laser device can be moved along a working area in order to carry out a predetermined work process there. The working area is preferably a build platform of a device for additive manufacturing.

[0026] In the context of the present invention, a laser device preferably refers to a processing head that is connected to a laser or a device for providing a laser beam in order to emit a laser beam, or that has its own laser or a device for providing a laser beam in order to emit a laser beam. Unless otherwise described, in the context of the present invention, a laser beam is understood to be a laser beam segment emitted from a processing head in the direction of the processing area.

[0027] The present invention is based on the understanding that in laser devices with multiple processing heads, each emitting a laser beam, the relative positioning of the processing heads to one another must be set very precisely, whereas the absolute positioning of all processing heads within the working area is not as critical. In a device for the additive manufacturing of components, it is irrelevant to the component itself whether it is manufactured at a predetermined position within the working area or slightly offset from it. However, it is extremely important that the individual sections of the component are positioned precisely relative to one another. Therefore, it is possible to calibrate a laser device using a sensor plate and a perforated plate gauge, which are designed independently of the laser device.During the calibration process, both the sensor plate and the gauge block are first inserted into the laser device to pre-calibrate the sensor plate, ensuring the relative position of the sensor fields is known. The gauge block can then be removed. The sensor plate should maintain its exact position within the laser device during the calibration process. However, its precise orientation relative to the laser device is of secondary importance. The crucial factor is that it maintains its position throughout the calibration process, allowing for precise calibration of the individual working heads relative to one another.

[0028] The combination of a sensor plate with multiple sensor fields and a perforated plate gauge creates a simple yet highly precise calibration device. A sensor plate with multiple sensor fields is typically a printed circuit board on which several area scan cameras are arranged, each forming a sensor field. Such a circuit board can warp slightly due to the material properties. This warping is primarily temperature-dependent. Therefore, the relative positioning of the sensor fields is not always perfectly accurate. By placing the perforated plate gauge with multiple calibration passes, each positioned within one of the sensor fields, on top of the sensor plate, only those areas of the sensor fields are used to calibrate the laser device. These areas are precisely aligned with each other due to the exact alignment of the perforated plate gauge's calibration passes.Using the perforated plate gauge, only areas of the sensor fields that are in an exact local relationship to each other are initially accessible, so that the relative positions of the sensor fields can be determined on the basis of this local relationship known through the perforated plate gauge.

[0029] Since the pre-calibration first determines the relative positions of the sensor fields, the calibration of the laser beams can be performed with the resolution provided by the sensor fields, unlike the prior art methods and devices described above, and is not limited to the diameter of the calibration apertures. Because the sensor fields have pixels that are generally much smaller than the calibration apertures, a resolution defined by the size of the sensor field pixels can be achieved. This device can therefore precisely measure both the location of the respective pilot laser beam and the area over which it strikes the respective sensor field. The latter allows for the optimization of the pilot laser beam's focus.

[0030] If the laser heads are calibrated using the sensor field areas defined by the perforated plate gauge, they can be precisely aligned spatially. In other words, the combination of sensor plate and perforated plate gauge forms a common, unified coordinate system to which all working heads are calibrated. This coordinate system defined by the sensor plate and the perforated plate gauge can therefore be called the common primary coordinate system.

[0031] In particular, the diameter of the pilot laser beam can be smaller than the corresponding calibration apertures. Since the spatial reference of the sensor fields is known, it is possible to determine the positions of the pilot laser beam with a higher resolution than is limited by the diameter of the calibration apertures. The resolution is then limited solely by the size of the pixels of the sensor fields, which, in conventional camera chips such as CMOS or CCD sensors, is significantly smaller than the size of the calibration apertures. A typical pixel size of the sensor fields is no larger than 2 µm x 2 µm and preferably no larger than 1.5 µm x 1.5 µm. The diameter of the calibration apertures is preferably at least 2 mm, and more particularly at least 3 mm or at least 5 mm. The area of ​​a calibration aperture thus encompasses a multitude of pixels of a sensor field.

[0032] The sensor plate is designed in such a way that it is subject to the same distortion due to the thermal influence of the working laser beam as a build platform and / or a component produced on the build platform.

[0033] The perforated plate can be made of an extremely stable material or a material with high mechanical strength, ensuring that the holes do not change their position even under thermal stress and are arranged in precise relation to each other to achieve high accuracy. The calibration through-holes are mapped onto the sensor fields of the sensor plate.

[0034] According to the invention, a pilot laser beam is used to calibrate a working laser beam. The sensor plate is positioned on a working area of ​​a laser device, in particular a build platform of an additive manufacturing system. The perforated plate gauge is then placed on this sensor plate. Subsequently, the sensor fields of the sensor plate are illuminated through the calibration aperture of the perforated plate gauge to determine the relative position of the sensor fields. A pilot laser beam is then positioned on the sensor fields through the calibration aperture of the perforated plate gauge, based on control information, using a laser device. Thus, the pilot laser beam is directed onto the sensor fields through several calibration apertures, with the control information defining target values.Several actual values ​​of the pilot laser beam's position information are now detected using the sensor fields. These actual values ​​are then compared with corresponding target values ​​of the position information for different locations or positions of the pilot laser beam, and the respective deviations are determined.

[0035] To control a laser device, a working laser beam is positioned within a working area using control information. According to the invention, the determined deviations are used as correction values ​​to determine the control information. A correction function can be generated by comparing actual and target values ​​of the position information of a working laser beam in order to interpolate the determined values ​​over a working area.

[0036] Furthermore, it can be provided that all sensor fields are covered by the perforated plate gauge, so that a calibration through-hole is arranged in the area of ​​each sensor field.

[0037] Thus, one aperture or a single perforated plate template is provided for all sensor fields of the sensor plate or sensor device.

[0038] The sensor fields can be arranged in an edge area of ​​the sensor plate.

[0039] The greatest distortions due to the thermal energy introduced by the laser device occur in the peripheral area of ​​a workspace or build platform of an additive manufacturing device. Therefore, it may be sufficient to identify only the relevant positions in the peripheral area of ​​the workspace. This results in a cost-effective device design.

[0040] The corresponding sensor devices of the sensor fields can preferably detect a position with an accuracy of a few µm or even one µm.

[0041] Preferably, approximately 10 to 50 or 15 to 40 and especially 20 to 30 sensor fields can be arranged on the sensor plate.

[0042] In addition, a laser device may be provided to supply a working laser beam.

[0043] The laser device could, for example, be a fiber laser. The laser can emit laser light with a power output of at least 200 watts, or at least 300 watts, up to a maximum of 400 watts, or up to a maximum of 600 watts, or up to a maximum of 800 watts, or up to a maximum of 1000 watts, or up to a maximum of 1200 watts.

[0044] The pilot laser device can be part of the laser device or designed as a separate pilot laser device.

[0045] For example, a laser from IPG Photonics, available under part number P21-010106, YLR-series SLED 3.0, can be used as the laser device. Such a laser beam can output a working laser beam and a pilot laser beam.

[0046] The pilot laser beam is preferably designed as a focused laser beam and can have a power output of approximately 0.1 watts.

[0047] The pilot laser beam can be formed, for example, by coupling less light into a laser generating unit of a laser device and / or by using a beam splitter, a polarization filter, a beam block, a deflection mirror, or by providing a laser with an adjustable pump stage whose pump stage can be switched off.

[0048] Therefore, both the working laser beam and the pilot laser beam can use the same fibers of a fiber laser.

[0049] Furthermore, the laser device can be configured to have several processing heads connected to a common laser, each emitting a laser beam in a multiplexing process. Alternatively, the laser device can also have several processing heads, each with its own laser (singleplex). These two types of configurations of the laser device with multiple processing heads for emitting laser beams are referred to as multi-laser devices within the scope of the present invention.

[0050] In such a multi-laser system, the lasers of the processing heads are initially each referenced with respect to their own coordinate system in an X / Y plane, meaning that each processing head is assigned a separate coordinate system. Thus, each laser of a processing head has its own coordinate system.

[0051] By calibrating the positions or location of the lasers of the processing heads using the device according to the invention, all lasers of the processing heads can be referenced with respect to the common main coordinate system, so that they are then calibrated with respect to the common main coordinate system in the working area.

[0052] During calibration, each processing head moves its laser beam to at least one, and preferably several, points within its own referenced coordinate system. These points are then mapped to corresponding points of a unified main coordinate system defined by the calibration device. This process calibrates the multi-laser system, or the multiple lasers of the multi-laser system, to this main coordinate system. In this way, all lasers of the processing heads can be aligned with respect to the unified main coordinate system.

[0053] Furthermore, the processing heads can be aligned or adjusted so that each optical axis of a respective laser beam from a processing head runs perpendicular to the working area of ​​the build platform or the processing surface. Due to the perpendicular laser beams, calibration can be performed independently of the plane, meaning that the distance of a processing head, and thus of the corresponding laser beam, can vary.

[0054] All optical axes of the multiple laser beams can be aligned perpendicular to a surface of the build platform. This means that the position of a laser beam on a corresponding sensor field of the sensor plate or the build platform changes when the distance of the laser device in the vertical direction (Z-coordinate) from the sensor plate changes.

[0055] Furthermore, a measuring device with appropriate sensors for measuring the diameter of a laser beam can be provided. The diameter of the laser beam can be, for example, at least 30 µm, in particular at least 50 µm or at least 100 µm. The diameter of the laser beam is preferably no more than 2 mm, in particular no more than 1 mm or no more than 500 µm.

[0056] It is not only possible to calibrate one laser of a processing head of the laser device, but the multiple lasers of a laser device can be calibrated and aligned relative to each other.

[0057] Thus, with the present invention, not only can a laser device with one laser be calibrated in the processing area, but several lasers from processing heads can be calibrated in the respective processing area, so that the several lasers of the processing heads of the multi-laser device are also calibrated relative to each other in the processing area.

[0058] The sensor device can include a printed circuit board and CMOS sensors, as well as preferably an electronic network connection.

[0059] The edges of the perforated plate gauge that define the calibration opening can be so sharp-edged and / or conically tapered that the perforated plate gauge is thin, at least in the area of ​​the calibration opening.

[0060] This way, parallax errors can be avoided.

[0061] The diameter of the calibration aperture can be approximately 4 to 5 mm smaller than the area of ​​a corresponding sensor field of a CMOS sensor.

[0062] The area of ​​a calibration through-hole can be smaller than the area of ​​a corresponding sensor field of the sensor device.

[0063] In particular, the calibration through-holes can be arranged in a grid or array with spacings between 50 mm and 500 mm.

[0064] Because the area of ​​the calibration through-hole is smaller than the area of ​​the corresponding sensor fields, the perforated plate gauge can be positioned easily.

[0065] The sensor plate and / or the perforated plate gauge may have a centering device for centered placement on a work area.

[0066] The work area is preferably a build platform for an additive manufacturing device. Accordingly, it can be provided that the sensor plate is centered and aligned on such a build platform by means of a first centering device.

[0067] Following this, the perforated plate gauge can be centered on the sensor plate using a second centering device.

[0068] Each calibration aperture can be fitted with a tube aperture pointing towards the laser device. Such a tube aperture allows for the generation of uniform diffuse light (dark-field light) in the area of ​​the sensor fields.

[0069] Furthermore, according to the invention, a system for calibrating a laser device is provided, comprising a device for calibrating a laser device as shown above, as well as a device for additive manufacturing with multiple processing heads for emitting laser beams.

[0070] Within the scope of the present invention, an additive manufacturing device is understood to be a device for the layer-by-layer construction of a three-dimensional component using a powder bed, a powder feeder, or a wire feeder, which serve as the starting material and are melted by means of a laser beam, an electron beam, plasma, or an electric arc. Accordingly, the additive manufacturing processes mentioned in the introductory description (3D printing: melting and solidification (Laser Engineered Net Shaping (LENS), as Direct Metal Deposition (DMD), or as Laser Additive Manufacturing (LAM)), local sintering or melting (Laser Sintering (SLS)), Metal Laser Sintering (DMLS), Metal Laser Sintering (IMLS), Electron Beam Melting (EBM), powder bed-based laser melting, Laser Powder Bed Fusion (LPBF), or laser cladding) are provided for an additive manufacturing device.

[0071] Furthermore, the invention provides a method for calibrating a laser device configured to freely position a working laser beam within a predetermined working area. This method can utilize a previously described device for calibrating a laser device and comprises the following steps. Arranging a sensor plate on the work area, wherein the sensor plate has multiple sensor fields; arranging a perforated plate gauge on the sensor plate, wherein the perforated plate gauge has multiple calibration apertures arranged in a predetermined arrangement relative to each other and each within the area of ​​a sensor field; exposing sensor fields of the sensor plate via the calibration aperture of the perforated plate gauge to determine the relative position of the sensor fields relative to each other; positioning a pilot laser beam on the sensor fields based on control information by means of a laser device, such that the pilot laser beam is directed onto multiple sensor fields, wherein the control information for positioning the pilot laser beam forms setpoint values; detecting multiple actual values ​​of position information of the pilot laser beam by means of the sensor fields.Comparing these actual values ​​with corresponding target values ​​from location information for different locations or positions of the pilot laser beam and determining the respective deviation.

[0072] The advantages of the method according to the invention correspond analogously to the advantages described above with reference to the device for calibrating a laser system. When calibrating the laser system, the perforated plate gauge can be arranged on the sensor plate. In this case, the sensor fields are only freely accessible and usable for calibrating the laser system in the area of ​​the calibration through-holes. Preferably, however, the perforated plate gauge is removed for calibrating the laser system, so that the entire sensor fields are available for calibrating the laser system.

[0073] The sensor fields, with the perforated plate template in place, can be exposed using the pilot laser beam or another light source. Suitable light sources are, in particular, those that emit diffuse light, such as dark-field light sources.

[0074] In particular, the method can be designed for multiple lasers of processing heads of a multi-laser device, wherein the following steps are performed: Positioning a pilot laser beam based on control information by means of a laser device through the calibration aperture of the perforated plate gauge onto the sensor fields, so that the pilot laser beam is directed onto the sensor fields, wherein the control information forms target values; detecting multiple actual values ​​of position information of the pilot laser beam by means of the sensor fields. Comparing these actual values ​​with corresponding target values ​​of location information from different locations or positions of the pilot laser beam and determining the respective deviation for the individual laser beams of the processing heads, and calibrating the multiple laser beams of the processing heads of the multi-laser device relative to each other in the processing area.

[0075] Furthermore, the invention provides a method for controlling a laser beam for a system described above, wherein a working laser beam is positioned in a working area by means of control information. The method is characterized in that the deviations determined above are used as correction values ​​to determine the control information.

[0076] A correction function can be generated by comparing actual and target values ​​of location information for a working laser beam in order to interpolate the determined correction values ​​over a working area.

[0077] The present invention will be described in more detail below with reference to exemplary embodiments illustrated in the figures. These show: Figure 1 a schematic perspective exploded view of a device according to the invention for calibrating a laser device, Figure 2 a schematic side view of a calibration through-hole of a perforated plate gauge of the device, and Figure 3 A schematic perspective view of a tube aperture for a calibration through-hole of a perforated plate gauge of the device.

[0078] In the following, a device 1 according to the invention for calibrating a laser device is described in more detail ( Figures 1 to 3The device 1 is designed to freely position a working laser beam within a predetermined working area. The working area is preferably a build platform 2 of a device for additive manufacturing (not shown).

[0079] The device 1 comprises a sensor plate 3 and a perforated plate gauge 4.

[0080] The device 1 further comprises a pilot laser unit (not shown) for providing a pilot laser beam along the beam path of a working laser beam in order to calibrate a laser unit. Preferably, the pilot laser unit is an integral part of a laser unit of an additive manufacturing device (not shown), or such a laser unit is configured to provide a pilot laser beam. Alternatively, the pilot laser unit can also be a standalone laser unit.

[0081] The sensor plate 3 has an approximately rectangular shape. In the present embodiment, twelve sensor devices with corresponding sensor fields 5 are arranged circumferentially in the area of ​​the edges of the sensor plate 3.

[0082] The sensor plate 3 is made of a material that exhibits a similar distortion to a corresponding build platform of an additive manufacturing device, such as a corresponding additively manufactured component.

[0083] According to this embodiment, the sensor fields 5 are arranged in an edge region of the sensor plate. A different suitable number of sensor fields 5 or sensor devices can also be used. For example, at least four, six, eight, ten, twelve, 14, 16, 18, 20, 22, 24, 26, 28, or 30 sensor fields and a maximum of 32, 34, 36, 38, 40, 42, 44, 46, 48, or 50 sensor fields 5 can be provided. Alternatively, the individual sensor fields 5 can also be arranged in a grid or array at approximately equal intervals.

[0084] The sensor plate 3 is formed from a printed circuit board, wherein the sensor devices or fields 5 are formed by CMOS sensors.

[0085] Furthermore, sensor plate 3 has a network connection (not shown) for connecting to a corresponding data network.

[0086] The sensor plate 3 has a centering device (not shown), e.g. by means of dowel pins, to position it centrally on a work area or build platform 2. This ensures that the sensor plate is fixed to the laser device during the calibration process.

[0087] The perforated plate gauge 4 also has an approximately rectangular shape. Furthermore, calibration through-holes 6 are formed in the perforated plate gauge 4, the number of which corresponds to the number of sensor fields 5 of the sensor plate 3. The calibration through-holes 6 are thus arranged in the perforated plate gauge 4 corresponding to the positions of the sensor fields 5 of the sensor plate 3.

[0088] The perforated plate gauge 4 is made of a material with high inherent stiffness or a very stable material, and thus a material with high mechanical strength, so that the perforated plate gauge 4 exhibits no distortion or virtually no distortion when thermal energy is introduced. This is very advantageous because the calibration through-holes 6 are then always arranged in the same location or position relative to the build platform.

[0089] The corresponding calibration through-holes 6 of the perforated plate gauge 4 are mapped onto the sensor fields 5 of the sensor plate 3 during use.

[0090] In this process, at least one calibration opening 6 of the perforated plate gauge 4 is assigned to each sensor field 5, so that a calibration opening 6 is arranged in the area of ​​each sensor field 5.

[0091] The edges or borders of the perforated plate gauge 4, which limit the calibration through-holes 6, are designed to be so sharp-edged or thin that parallax errors can be avoided.

[0092] Additionally and / or alternatively, the calibration openings 6 or the edges of the perforated plate gauge 4 limiting the calibration openings 6 can be conically tapered in the direction of the sensor fields 5 in order to also avoid parallax errors ( Figure 2 ).

[0093] The area of ​​the calibration through-hole 6 is smaller than the area of ​​a corresponding sensor field 5 in order to be completely covered by the respective sensor field 5. In this way, the calibration through-holes 6 can be easily positioned and aligned with the sensor fields 5 of the sensor plate 3.

[0094] Additionally, a pipe aperture 7 pointing towards the laser device can be arranged on each of the calibration passage openings 6 ( Figure 3 ). By means of the tube aperture 7, uniform diffuse light (dark-field light) can be generated in the area of ​​the sensor fields 5.

[0095] A system according to the invention for calibrating a laser device (not shown) comprises the device 1 for calibrating a laser device described above and a device for additive manufacturing. The device for additive manufacturing can be a corresponding device for one of the additive manufacturing processes described above. Such a device comprises several processing heads for emitting a laser beam each.

[0096] Furthermore, according to the invention, a method for calibrating a laser device is provided, which is configured to freely position a working laser beam in a predetermined working area. The method uses the device 1 described above for calibrating a laser device.

[0097] The process comprises the following steps: First, a sensor plate 3 is arranged on a work area, in particular a build platform 2 of an additive manufacturing device (S1). The sensor plate is centered and aligned on the build platform by means of a centering device.

[0098] Subsequently, a perforated plate gauge 4 is arranged on the sensor plate 3, wherein the perforated plate gauge 4 has several calibration passage openings 6 which are arranged in a predetermined arrangement relative to each other (S2).

[0099] The sensor fields 5 are now exposed. Exposure is achieved through the calibration apertures 6 of the perforated plate gauge 4 to determine the relative position of the sensor fields 5 to each other (S3). The complete calibration apertures 6 are projected onto the respective sensor fields 5.

[0100] Subsequently, a pilot laser beam is positioned on the sensor fields through the calibration openings 6 of the perforated plate gauge 4 using a laser device (S4), based on control information. In this way, the pilot laser beam is directed onto the sensor fields through several calibration openings 6. The corresponding control information establishes target values.

[0101] Using the sensor fields 5, several actual values ​​of position information of the pilot laser beam are then detected (S5).

[0102] Finally, these actual values ​​are compared with corresponding target values ​​of location information for different locations or positions of the pilot laser beam (S6).

[0103] Based on these values, the respective deviations of the target values ​​from the actual values ​​can be determined (S7).

[0104] Furthermore, according to the invention, a method for controlling a laser beam is provided using a system as described above, wherein a working laser beam with control information is positioned in a working area. The deviations determined by the method for calibrating a laser device are used as correction values ​​to determine the control information.

[0105] A correction function is generated by comparing actual and target values ​​of the positional information of a working laser beam. Using this correction function, the determined values ​​can be interpolated across a working range.

[0106] Instead of a device for additive manufacturing, the device according to the invention can, for example, also be used for calibrating a laser beam for a laser cutting device or similar.

[0107] Key components of a laser cutting device or laser beam cutting machine are the laser beam source, the laser beam guidance system, and the processing head (focusing optics) including the cutting nozzle. The beam exiting the laser beam source can be guided to the focusing optics at the processing point via fiber optic cables in the near-infrared range (Nd:YAG lasers, fiber lasers, disk lasers), or via deflecting mirrors in the case of CO2 lasers. The focusing optics concentrate the laser beam into a focus, thus generating the intensity required for cutting.

[0108] Systems using CO2 lasers typically consist of a stationary laser beam source and a so-called "flying" optic. A reflecting telescope ensures a constant raw beam diameter on the focusing lens across the entire processing area. This is necessary because the beam exiting the laser has a fixed divergence. Without compensation by the reflecting telescope, varying beam path lengths for different processing positions would change the raw beam diameter on the lens, resulting in different aperture values ​​and intensities.

[0109] The beam guidance between the optical resonator (laser beam source) and the focusing optics is achieved using mirrors, which may be water-cooled. These mirrors are gold- or molybdenum-coated and made of monocrystalline silicon or pure copper. Laser radiation in a wavelength range of approximately 1 µm (Nd:YAG lasers, fiber lasers, disk lasers), on the other hand, can be guided over long distances using fiber optic cables.

[0110] For direction-independent cutting quality, phase-rotating mirrors are arranged between the resonator and telescope when using linearly polarized laser beams.

[0111] The jet emerges in a focused manner through the so-called cutting nozzle, which is usually made of copper and also directs the blowing or process gas to the processing point. Reference symbol list

[0112] 1 Device 2 Construction platform 3 Sensor plate 4 Perforated plate gauge 5 Sensor field 6 Calibration through-hole 7 Pipe orifice

Claims

1. A device (1) for calibrating a laser device which is designed to freely position a working laser beam in a predetermined working range, comprising a sensor plate (3) with several sensor fields (5) for arrangement in a working area, a perforated plate gauge (4) with a plurality of calibration openings (6), wherein the plurality of calibration openings (6) are each arranged in the region of one of the sensor fields (5), the surface of the calibration openings (6) being smaller than the respective surface of a corresponding sensor field (5) of the sensor plate (3), a control device for determining the relative position of the sensor fields (5) to each other after exposing them through the calibration openings (6) of the perforated plate gauge (4), a pilot laser device for providing a pilot laser beam along the path of the working laser beam in order to calibrate a laser device by scanning the pilot laser beam by means of the sensor fields.

2. The device (1) according to claim 1, characterized in that all sensor fields (5) are covered by the perforated plate gauge (4), so that a calibration opening (6) is arranged in the area of each sensor field (5).

3. The device (1) according to claim 1 or 2, characterized in that the sensor fields (5) are arranged in an edge region of the sensor plate (3).

4. The device (1) according to any one of the claims 1 to 3, characterized in that a laser device is designed to provide a working laser beam.

5. The device (1) according to claim 4, characterized in that the pilot laser device is part of the laser device or is designed as a separate pilot laser device.

6. The device (1) according to any one of the claims 1 to 5, characterized in that the sensor plate (3) comprises a printed circuit board and CMOS sensors and / or CCD sensors and preferably an electronic network connection.

7. The device (1) according to any one of the claims 1 to 6, characterized in that the edges of the perforated plate gauge (4) bounding the calibration openings (6) are sharpedged and / or conical in such a way that the perforated plate is so thin, at least in the region of the calibrating openings (6), that parallax errors can be avoided.

8. The device (1) according to any one of the claims 1 to 7, characterized in that, the calibrating openings (6) are arranged in a grid with spacings of between 50 mm and 500 mm.

9. The device (1) according to any one of the claims 1 to 8, characterized in that, the sensor plate (3) and / or the perforated plate gauge (4) have a centering device for centered arrangement in a working area.

10. The device (1) according to any one of the claims 1 to 9, characterized in that, a tubular diaphragm (7) pointing in the direction of the laser device is arranged on each of the calibration openings (6) in order to generate uniform diffuse light in the area of the sensor fields.

11. A system for calibrating a laser device comprising a device (1) for calibrating a laser device according to any one of the claims 1 to 10, and a device (1) for additive manufacturing, wherein the device (1) for additive manufacturing comprises a plurality of processing heads for emitting a respective laser beam.

12. A method for calibrating a laser device adapted to freely position a working laser beam in a predetermined working area with a device (1) according to any one of the claims 1 to 10, comprising the following steps: arrangement of a sensor plate (3) on the working area, wherein the sensor plate is having a plurality of sensor fields (5), arrangement of a perforated plate gauge (4) on the sensor plate (3), the perforated plate gauge (4) having a plurality of calibration openings (6), which are arranged in a predetermined arrangement relative to one another and in each case in the region of a sensor field, exposure of sensor fields (5) of the sensor plate (3) via the calibration openings (6) of the perforated plate gauge (4) in order to determine the relative position of the sensor fields (5) to one another, positioning of a pilot laser beam on the basis of control information by means of a laser device onto the sensor fields (5), so that the pilot laser beam is directed onto a plurality of sensor fields (5), wherein the control information for positioning the pilot laser beam forms target values, detection of several actual values of location information of the pilot laser beam by means of the sensor fields (5), comparison of these actual values with corresponding target values of location information for different locations of the pilot laser beam, and determine the respective deviations.

13. The method according to claim 12, characterized in that, the deviations determined are used as correction values to determine the control information for positioning a working laser beam.

14. The method according to claim 13, characterized in that, a correction function is generated on the basis of a comparison of actual values and target values of location information of a working laser beam in order to interpolate the determined values over a working range.

15. The method according to any one of the claims 12 to 14, characterized in that, the method is designed for a plurality of laser beams from processing heads of a multi-laser device, the following further steps being carried out, determining the respective deviation for the individual laser beams of the processing heads, and calibrating the multiple laser beams of the processing heads of the multi-laser device relative to each other in the processing area.