Method for calibrating a manufacturing device for the additive manufacturing of a three-dimensional object, and manufacturing device

Abstract

The invention relates to a method for calibrating a manufacturing device (1) for the additive manufacturing of a three-dimensional object (19) by layer-by-layer application and selective solidification of a powder material (15) within a construction area in a processing plane (18), wherein the manufacturing device (1) comprises: at least one beam deflection unit (9a, 9b, 9c) which is designed to direct a beam (11a, 11b, 11c) generated by a respective beam generation unit (10a, 10b, 10c) onto different target points in the processing plane (18) which lie within a scanning region assigned to the respective beam deflection unit (9a, 9b, 9c); and a reference body (30) which is arranged in the construction area in the processing plane (18), wherein the reference body (30) has a plurality of markings (31) which are arranged at predetermined positions of the reference body (30), the method comprising the following steps: displacing the beam (11a, 11b, 11c) of the manufacturing device (1) in the scanning region over regions on the reference body (30) which contain one or more markings (31); detecting, in a location-dependent manner, signal values of light (20) of the beam (11a, 11b, 11c) remitted along an optical axis (A) of the beam (11a, 11b, 11c), wherein each location of the displacement of the beam (11a, 11b, 11c) in the scanning region (7) is assigned a signal value; obtaining spatially resolved information about the positions of the markings (31) on the reference body (30); comparing the obtained spatially resolved information with the predetermined positions of the markings (31) on the reference body (30) in order to calculate an alignment error between the beam (11a, 11b, 11c) and the predetermined positions of the markings (31) on the reference body (30); and correcting the alignment error by adapting the location-dependent positioning of the beam (11a, 11b, 11c).

Description

[0001] Method for calibrating a manufacturing device for additive manufacturing of a three-dimensional object and a manufacturing device

[0002] Technical area

[0003] The invention relates to a method for calibrating a manufacturing device for the additive manufacture of a three-dimensional object by layer-by-layer application and selective solidification of a powder material within a construction field in a processing plane and to a manufacturing device for the additive manufacture of a three-dimensional object by layer-by-layer application and selective solidification of a powder material within a construction field in a processing plane.

[0004] Background of the Revelation

[0005] In additive manufacturing, e.g., selective laser sintering or selective laser melting, a powdered material, e.g., a metal or ceramic powder, is irradiated with electromagnetic radiation. Thin powder layers are successively applied in a chamber on a build platform to form three-dimensional objects by irradiating the respective powder layers with an irradiation beam, e.g., a laser beam. Corresponding devices are referred to as additive manufacturing devices, 3D printing systems, selective laser sintering machines, or selective laser melting machines, and the like. For the operation of such a device, see, for example, EP 2 732 890 A2.

[0006] In recent years, the additive manufacturing of components has also gained importance in industrial settings. Additive manufacturing in a powder bed (Powder Bed Fusion, PBF), in which thin layers of powder, e.g., made of metal, ceramic, or thermoplastic powder, are gradually applied and locally solidified with one or more beams to successively build up the component, is particularly suitable for the production of complex and delicate components. Machines suitable for performing a PBF process are referred to below as PBF machines. Lasers and electron beam systems are typically used as beam generation units. When a laser source is used, the process is also referred to as Powder Bed Fusion - Laser Based (PBF-LB). The beam can sinter or melt the powder to solidify it, thereby bonding it to previously solidified component layers.Depending on the beam generation unit, sintering is referred to as selective laser sintering or electron beam sintering, while melting is referred to as selective laser melting or electron beam melting. Powder-bed-based additive manufacturing of metal powder using a laser beam is also known as laser metal fusion.

[0007] Since the component is produced layer by layer, such an additive manufacturing process is relatively time-consuming. To reduce production time, multiple energy beams—for example, 2, 3, 4, 8, 12, or 16 energy beams—are used instead of a single energy beam. The manufacturing device used in this process typically has at least one deflection unit or scanner device configured to shift the energy beams.

[0008] By using multiple energy beams, it is possible for a first energy beam to produce a first component in a work area of ​​the manufacturing device, while at the same time a second energy beam works on the same component and / or produces a second component in the work area.

[0009] With such a manufacturing device, there is fundamentally the requirement to monitor a work area in which a component is being additively built from a powder material. This particularly applies to the monitoring of newly applied powder layers, especially for potentially inadequately coated areas or break-off edges, the analysis of melted areas of a powder shift, the recording of the resulting component, and other requirements. Furthermore, it is increasingly becoming apparent that certain components are not manufactured entirely using additive manufacturing, particularly due to the resulting cost and speed advantages. Instead, specific sections of a component, where the advantages of this process are particularly realized, are built using additive manufacturing on a conventionally manufactured basic shape, a so-called preform.This makes it possible to produce the preform, for example a clamping shaft of a tool, for which additive manufacturing would not offer any advantages, quickly and, above all, cost-effectively using conventional methods. Subsequently, only the component geometry that could not be produced conventionally or could only be produced with significantly greater effort is then additively built on the preform. Precise knowledge of the position of the preform in the work area is essential for good component quality in such mixed components, which are also referred to as hybrid components, so that the additively manufactured component area can be built on the preform with high precision and without offset. In particular, it is necessary to record the position of the preform with an accuracy of a few tens of microns.In principle, separate measuring devices or measuring devices specifically integrated into the additive manufacturing device can be used for this purpose. However, two influencing factors influence the position determination: first, the accuracy of the measuring device itself, and second, the registration accuracy between the measuring device and a scanner device for relocating an optical working beam for additive manufacturing. The term "registration accuracy" refers in particular to the accuracy of a transformation from the coordinate system of the measuring device to the coordinate system of the scanner device. This registration accuracy, in particular, is directly influenced by instabilities and / or drifts in the measuring device as well as the scanner device.Such error contributions—especially when combined—directly lead to a reduction in the quality and / or accuracy of the resulting component, particularly to an offset between the preform and the additively manufactured component section built on it. This problem occurs regardless of the choice of measuring device for position determination, be it triangulation sensors, photogrammetric sensors, structured light projection sensors, optical cameras, photodiodes, or line sensors, which capture the work area independently of the scanning device.

[0010] The present invention is based on the object of providing a method for calibrating a manufacturing device for the additive manufacture of a three-dimensional object by layer-by-layer application and selective solidification of a powder material within a construction field in a processing plane and a manufacturing device for the additive manufacture of a three-dimensional object by layer-by-layer application and selective solidification of a powder material within a construction field in a processing plane, wherein the aforementioned disadvantages do not occur or are at least reduced.

[0011] In general, the present disclosure is directed, at least in part, to improving on or overcoming one or more aspects of prior systems. Thus, the present disclosure is directed, at least in part, to improving on or completely overcoming one or more aspects of prior systems. Summary of the Disclosure

[0012] The object is achieved by providing the present technical teaching, in particular the teaching of the independent claims as well as the preferred embodiments disclosed in the dependent claims and the description.

[0013] The object is achieved in particular by a method for calibrating a manufacturing device for the additive manufacture of a three-dimensional object by layer-by-layer application and selective solidification of a powder material within a construction field in a processing plane, wherein the manufacturing device comprises: at least one beam deflection unit orA scanning unit which is configured to direct a beam generated by a respective beam generation unit onto different target points in the processing plane which lie within a scanning range assigned to the respective beam deflection unit, and a reference body, such as a reference plate, which is arranged in the construction field in the processing plane, wherein the reference body has a plurality of markings which are arranged at predetermined positions of the reference body, the method comprising the following steps: displacing the beam of the production device in the scanning range over regions on the reference body which contain or have one or more markings.about the markings on the reference body, location-dependent detection of signal values ​​of light of the beam remitted along an optical axis of the beam, wherein a signal value is assigned to each location of the displacement of the beam in the scanning area, obtaining spatially resolved information about the positions of the markings on the reference body, comparing the obtained spatially resolved information with the predetermined positions of the markings on the reference body in order to calculate an alignment error between the beam and the predetermined positions of the markings on the reference body, and correcting the alignment error by adjusting the location-dependent positioning of the beam.

[0014] The detection of remitted light makes it possible to observe the work area with a comparatively low optical output power of the working beam, as there is no need to rely on process lighting and / or thermal emissions, which occur in power ranges of the optical working beam in which materials arranged in the work area, be it a preform or powder material, can change. This means that the work area can be detected without causing damage and / or without affecting a subsequent build process for producing a generative component. Because the remitted light is detected along the optical axis of the optical working beam, the location-dependent detection of the signal values ​​takes place directly in the coordinate system of the scanner device, so that the otherwise required registration between a measuring device and the scanner device is completely eliminated.This also eliminates the previously mentioned sources of error, and the detection of the work area is very precise. This allows the position of a preform, in particular, to be determined very precisely. If the optical working beam is used to detect the work area, additional sensor components are also eliminated, which is both simple and cost-effective. The process is therefore very simple and cost-effective to implement. In particular, existing components of the additive manufacturing device can advantageously be used, so that only implementation of the process in the control software of the additive manufacturing device is required. This is quick, simple, cost-effective, and can also be retrofitted to existing additive manufacturing devices.

[0015] According to a further development of the invention, the signal value of the remitted light is detected by a photodiode arranged on the optical axis of the optical working beam. This represents a simple and cost-effective way of detecting the optical signal values. A silicon photodiode is preferably used as the photodiode. The photodiode can be sensitive in the visible and / or infrared spectral range. The sensitivity of the photodiode is preferably matched to the wavelength range of the optical working beam. An infrared photodiode or a pyrometer diode can preferably be used.

[0016] The signal value is preferably recorded with spatial resolution by assigning an output signal of the photodiode to a momentary state, in particular an internal state, of the scanner device in a time-dependent manner. The recording of the signal values, in this case the output signal of the photodiode, and the displacement of the optical working beam by corresponding control of the scanner device thus takes place in particular synchronously, so that each signal value can be assigned a state of the scanner device and thus simultaneously a location in the working area. The state of the scanner device is in particular a position of at least one movable mirror of the scanner device, in particular a galvanometric mirror, which in turn is assigned to a location in the working area at which the optical working beam is directed. The spatially resolved recording of the signal values ​​thus takes place directly in the coordinate system of the scanner device.The advantage of the present invention also lies in the fact that neither inaccuracies in the positioning of the detector relative to the optical axis of the main system nor the exact size of the detector's detection area / field of view have an impact on the resolution or accuracy of the detection. This depends solely on the beam size and quality of the light source / measurement beam, the temporal resolution of the detection, and the positioning accuracy of the beam deflection unit.

[0017] According to a further development of the invention, the resolution of the detection of the working area is set, preferably changed. In particular, the resolution is preferably selected as needed. The resolution is particularly preferably set by shifting the optical working beam with an appropriate step size. However, it is also possible to select the resolution through targeted time-dependent evaluation of the detection device, for example by not detecting the output signal continuously, but rather only at predetermined intervals that are greater than the time interval between two consecutive output signal values. By adjusting the resolution, it is possible, on the one hand, to provide a high resolution when this is desirable or necessary, and, on the other hand, to advantageously reduce the data volume when a lower resolution is sufficient.

[0018] Alternatively or additionally, a detection section of the working area is preferably set, preferably changed. In particular, the detection section is preferably selected as needed. It is also possible to define several separate detection sections. This can also be achieved by shifting the optical working beam only within a specific detection section or by evaluating the output signal of the detection device only within the specified detection section. The detection section is preferably selected such that the markings to be detected can be scanned within these sections.

[0019] The resolution and / or the detection range can be selected dynamically, preferably via software configuration. In particular, it is thus possible, for example, to perform a powder bed analysis with higher spatial resolution than detecting the position of a preform, in particular to be able to detect defects in the powder bed, particularly in a newly applied powder shift, more accurately. Alternatively, the beam for detecting the processing plane is operated with an optical output power that is reduced compared to a lower power limit for the optical output power of the beam for additive manufacturing.

[0020] According to a development of the invention, the optical working beam for detecting the work area is operated with an optical output power that is lower than a lower power limit for the optical output power of the optical working beam for generative manufacturing. In this way, a change in material arranged in the work area, be it powder material or a preform, is avoided. The lower power limit is selected in particular such that a material change, in particular sintering or melting, in particular of the powder material of the generative manufacturing device, only occurs from this lower power limit or above this lower power limit, so that generative manufacturing with the optical working beam is possible. The optical output power of the optical working beam is therefore preferably selected to be higher than the lower power limit for generative manufacturing.Thus, an operating mode for detecting the working area on the one hand and an operating mode for generative manufacturing on the other hand are clearly separated from each other with regard to the selected optical output power of the optical working beam.

[0021] In particular, the same optical working beam is used for both additive manufacturing and the acquisition of the work area, except for the reduction of the optical output power if necessary.

[0022] According to a preferred embodiment, the lower power limit is 100 W. To capture the working area, the optical working beam is preferably operated with an optical output power of at least 1 W to at most 99.9 W, in particular of at least 2 W to at most 50 W. For additive manufacturing, the optical working beam is preferably operated with an optical output power of at least 100 W, preferably more than 100 W, preferably of at least 100 W to 500 W. Higher power ranges are not excluded, in particular up to a range of 1.5 kW.

[0023] Preferably, the markings on the reference body consist of holes, notches, depressions, raised structures, roughened surfaces, dowel pins, or spheres. In a further embodiment, the markings on the reference body consist of a diaphragm with a hole and an underlying cavity, preferably a cone or a shaft. An absorbent surface is preferably applied to the back of the cavity to reduce possible back reflections.

[0024] Alternatively, the cover has a hole that is not centered on the cover.

[0025] Preferably, the aperture has a conical bore, wherein the cross section of the conical bore of the aperture decreases in the direction of the underlying cone.

[0026] Preferably, the cross-section of the cavity increases towards the aperture.

[0027] In a further embodiment, the cavity opens into another bore with a constant diameter.

[0028] In a further embodiment, the markings are directly integrated into the reference body or detachably connected to the reference body.

[0029] Alternatively, the reference body serves as a common reference for other sensor components, such as a camera or height reference for the coater / powder height.

[0030] The object is finally also achieved by creating a manufacturing device for the additive manufacturing of a three-dimensional object by layer-by-layer application and selective solidification of a powder material within a construction field in a processing plane, wherein the manufacturing device comprises: at least one beam deflection unit, which is configured to direct a beam generated by a respective beam generation unit onto different target points in the processing plane, which lie within a scanning range assigned to the respective beam deflection unit, a reference body, which is arranged in the construction field in the processing plane, wherein the reference body has a plurality of markings, which are arranged at predetermined positions of the reference body, a detection device, which is configured to detect light of the beam remitted along an optical axis of the beam,wherein the detection device is arranged on an optical axis of the beam, and a control device configured to control the beam deflection unit for displacing the beam in the processing plane over areas on the reference body containing one or more markings, or over the markings on the reference plate, to detect location-dependent signal values ​​of the detection device during the displacement of the beam, to assign a signal value of the detection device to each location of the displacement of the beam in the processing plane, to obtain spatially resolved information about the positions of the markings on the reference body, to compare the obtained spatially resolved information with the predetermined positions of the markings on the reference body, to calculate an alignment error between the beam and the predetermined positions of the markings on the reference body,and to correct the alignment error by adjusting the location-dependent positioning of the beam.

[0031] In particular, the control device is preferably configured to assemble, calculate or otherwise form the image of the working area from the location-dependent detected signal values.

[0032] Furthermore, the control device is preferably configured to evaluate the image of the work area to detect geometric structures, in particular to perform edge detection. In particular, the beam generation unit comprises a laser or is designed as a laser.

[0033] Preferably, the detection device comprises a photodiode or is designed as a photodiode, or wherein the detection device is designed as a planar sensor, such as a camera, preferably with low resolution, 4-quadrant diode, point sensors.

[0034] Other features and aspects of this disclosure will become apparent from the following description and the accompanying drawings.

[0035] Brief description of the drawings

[0036] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings:

[0037] Fig. 1 is a schematic representation of an embodiment of a manufacturing device for additively manufacturing a three-dimensional object, Fig. 2 is a schematic representation of an embodiment of a manufacturing device for additively manufacturing a three-dimensional object with a reference body,

[0038] Fig. 3 is a plan view of an embodiment of a reference body with markings,

[0039] Fig. 4 is a schematic representation of an embodiment of a marking, and

[0040] Fig. 5 shows a reference body with markings in a side view according to another embodiment of the present invention.

[0041] Detailed description

[0042] The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described herein and illustrated in the drawings are intended to teach the principles of the present disclosure and to enable one of ordinary skill in the art to implement and use the present disclosure in a variety of environments and for a variety of applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered, a limiting description of the scope of patent protection. Rather, the scope of patent protection is to be defined by the appended claims.

[0043] Figure 1 schematically shows a manufacturing device 1 with a build space 3 or a build chamber and a control unit 5. The control unit 5 has a data storage medium for storing control programs. In this embodiment, the manufacturing device 1 further comprises three beam deflection units 9a, 9b, 9c, each deflecting a beam 11a, 11b, 11c along an optical axis A by means of a beam generation unit 10a, 10b, 10c. For example, each beam deflection unit 9a, 9b, 9c for a beam or laser beam can comprise a scanner mirror (not shown) that can be rotated in two directions or two scanner mirrors that can be rotated in one direction. For example, the beam deflection unit 9a, 9b, 9c can comprise a galvanometer scanner. Alternatively, the beam deflection unit 9a, 9b, 9c for an electron beam may comprise several pairs of electrodes between which an electric field may be applied to deflect the electron beam.

[0044] The production device 1 further comprises a substrate plate 13, which is arranged below the beam deflection units 9a, 9b, 9c and onto which a build material 15, such as a powder or a powder bed, is applied layer by layer. For this purpose, the substrate plate 13 is adjusted by a desired distance in the Z direction, i.e. in the direction of increasing distance from the beam deflection units 9a, 9b, 9c, and a new layer of build material is then applied using an application device 17, such as a coater or a powder pusher. Scrapers, blades, or rollers, for example, can also be considered as application devices 17. In this special case, the beam deflection units 9a, 9b, 9c are suitable for deflecting their respective beams 11a, 11b, 11c over the entire build space 3. Thus, in this embodiment, the entire build space surface represents a common processing plane 18 in which the beams 11a, 11b, 11c can solidify the build material 15.After the topmost build material layer has solidified, the substrate plate 13 can be moved again in the Z direction in its build cylinder 14 and a new build material layer is applied via the application device 17 in order to produce a three-dimensional object 19 layer by layer.

[0045] The build space 3 or the build chamber is gas-tight and includes an inflow channel 21 and an exhaust channel 23. The build space 3 can be filled with an inert gas such as nitrogen or argon via the inflow channel 21 to prevent oxidation of the build material 15. Together with the exhaust channel 23, a uniform protective gas flow can also be created over the build material 15 to remove condensate, powder particles, and other particles that are ejected into the atmosphere during solidification with laser beams, thus reducing potential interference with the laser beam. The exhaust channel 23 can also be used to evacuate the build space 3 so that electron beams can be used as beams 11a, 11b, 11c. For this purpose, the build space 3 must be made vacuum-tight.

[0046] The control unit 5 can also have a data interface, via which, for example, control programs can be imported. When executing a control program via a control interface, the control unit 5 can perform all steps on the device necessary for layer-by-layer additive manufacturing, such as activating or deactivating beams 11a, 11b, 11c, deflecting them with the beam deflection units 9a, 9b, 9c, adjusting the substrate plate 13 along the Z-axis, or initiating a build material application. Figure 2 shows a schematic representation of an embodiment of a manufacturing device 1 for the additive manufacturing of a three-dimensional object 19 with a reference body 30 or, in this embodiment, a reference plate 30.

[0047] In the present embodiment, the reference plate 30 is arranged in the processing plane 18 and fastened to the substrate plate 13. The reference plate 30 can thus be moved up or down in the Z direction together with the substrate plate 13.

[0048] Furthermore, as also shown in Figure 3, the reference plate 30 has a plurality of markings 31 arranged at predetermined positions on the reference plate 30. The positioning of the markings 31 on the reference plate 30 was measured in advance using a suitable method, so that the reference plate 30, with its precisely arranged markings 31, can serve as a reference for calibration. Preferably, the markings 31 are arranged at a uniform distance from one another and distributed across the entire reference plate 30.

[0049] If the beam 11a now hits one of the markings 31 of the reference plate 30, the remitted light 20 is reflected back again.

[0050] Figure 4 shows a schematic sectional view of an embodiment of a marking 31. Here, the markings 31 on the reference plate 30 consist of a diaphragm 31a with a bore 31b and an underlying cavity 31c, preferably a cone, wherein an absorbing surface 31d is preferably applied to the rear side of the cavity 31c, which reduces possible back reflections. The diaphragm 31a has a bore 31b that is not centered on the diaphragm 31a. Furthermore, the bore 31b of the diaphragm 31a is a conical bore 31b, wherein the cross-section of the conical bore 31b of the diaphragm 31a decreases in the direction of the underlying cone. Furthermore, the cross-section of the cavity 31c increases in the direction of the diaphragm 31a. At the end of the cavity 31c opposite the aperture 31a, the cavity opens into a further bore 31e of constant diameter.

[0051] Figure 5 shows a reference plate 30 with markings 31 in a sectional side view according to a further embodiment of the present invention. As shown in this embodiment, the substrate plate 13 can be moved up and down in the Z direction within the build cylinder 14 of the production device 1. The reference plate 30 is attached to the substrate plate 13 and, in this embodiment, is mounted on supports 32 so that the reference plate 30 does not rest directly on the substrate plate 13. This forms a cavity 31c between the reference plate 30 and the substrate plate 13. The reference plate 30 has markings 31, which in this embodiment are designed as bores 31b. The cavity 31c serves in particular to absorb light. To enhance this effect, an absorbing surface 31d in the form of a black absorber plate is attached to the substrate plate 13.

[0052] It is expressly understood that all features disclosed in the description and / or the claims are intended to be disclosed separately and independently of one another for the purpose of original disclosure and for the purpose of limiting the claimed invention, regardless of the composition of the features in the embodiments and / or the claims. It is expressly understood that all ranges of values ​​or indications of groups of units disclose every possible intermediate value or intermediate value for the purpose of original disclosure and for the purpose of limiting the claimed invention, in particular as limits of ranges of values.

[0053] Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.

[0054] List of reference symbols

[0055] 1 manufacturing device

[0056] 3 Build space or build chamber

[0057] 5 Control unit

[0058] 9a, 9b, 9c Beam deflection unit

[0059] 10a, 10b, 10c Beam generation unit

[0060] 11a, 11b, 11c beam

[0061] 13 Substrate plate

[0062] 14 building cylinders

[0063] 15 Powder material or building material

[0064] 17 Application device

[0065] 18 processing level

[0066] 19 Component or three-dimensional object

[0067] 20 remitted light

[0068] 21 Inlet channel

[0069] 23 Suction channel

[0070] 30 reference bodies or reference plates

[0071] 31 Marking

[0072] 31a aperture

[0073] 31b bore

[0074] 31c Cavity

[0075] 3 Id absorbing area

[0076] 31 further drilling

[0077] 32 support

[0078] 40 photodiode

[0079] 50 detection device

[0080] A optical axis

Claims

Claims 1. A method for calibrating a manufacturing device (1) for additively manufacturing a three-dimensional object (19) by layer-by-layer application and selective solidification of a powder material (15) within a construction field in a processing plane (18), wherein the manufacturing device (1) comprises: at least one beam deflection unit (9a, 9b, 9c) which is configured to direct a beam (11a, 11b, 11c) generated by a respective beam generation unit (10a, 10b, 10c) onto different target points in the processing plane (18) that lie within a scanning range assigned to the respective beam deflection unit (9a, 9b, 9c), and a reference body (30) which is arranged in the construction field in the processing plane (18), wherein the reference body (30) has a plurality of markings (31) which are located at predetermined positions of the reference body (30). are arranged, the method comprising the following steps: Displacing the beam (11a, 11b, 11c) of the manufacturing device (1) in the scanning area over areas on the reference body (30) which contain one or more markings (31), location-dependent detection of signal values ​​of light (20) of the beam (11a, 11b, 11c) remitted along an optical axis (A) of the beam (11a, 11b, 11c), wherein a signal value is assigned to each location of the displacement of the beam (11a, 11b, 11c) in the scanning area (7), Obtaining spatially resolved information about the positions of the markings (31) on the reference body (30), Comparing the obtained spatially resolved information with the predetermined positions of the markings (31) on the reference body (30) to calculate an alignment error between the beam (11a, 11b, 11c) and the predetermined positions of the markings (31) on the reference body (30), and correcting the alignment error by adjusting the location-dependent positioning of the beam (11a, 11b, 11c).

2. Method according to claim 1, wherein the signal value of the remitted light (15) is determined by a photodiode (40) arranged on the optical axis (A) of the beam (11a, 11b, 11c) is detected, wherein the signal value is detected in a spatially resolved manner by assigning an output signal of the photodiode (40) in a time-dependent manner to a synchronous state of a scanner device (9) for displacing the beam (11a, 11b, 11c).

3. Method according to claim 1 or 2, wherein a resolution of the detection and / or a detection section of the processing plane (18) is / are set.

4. The method according to any one of claims 1 to 3, wherein the beam (11a, 11b, 11c) for detecting the machining plane (18) is operated with an optical output power that is reduced compared to a lower power limit for the optical output power of the beam (11a, 11b, 11c) for additive manufacturing.

5. Method according to one of claims 1 to 4, wherein the markings (31) on the reference body (30) consist of bores, notches, depressions, raised structures, roughened surfaces, dowel pins or balls.

6. Method according to one of claims 1 to 4, wherein the markings (31) on the reference body (30) consist of a diaphragm (31a) with a bore (31b) and an underlying cavity (31c), preferably a cone or a shaft, wherein an absorbing surface (31d) is preferably attached to the back of the cavity (31c), which reduces possible back reflections.

7. The method according to claim 6, wherein the aperture (31a) has a bore (31b) which is not centered on the aperture (31a).

8. The method according to claim 6 or 7, wherein the aperture (31a) has a conical bore (31b), and wherein the cross section of the conical bore (31b) of the aperture (31a) decreases in the direction of the underlying cone.

9. Method according to one of claims 6 to 8, wherein the cross-section of the cavity (31c) increases in the direction of the aperture (31a).

10. Method according to one of claims 6 to 9, wherein the cavity (31c) opens into a further bore (31e) of constant diameter.

11. Method according to one of claims 1 to 10, wherein the markings (31) are directly integrated into the reference body (30) or are detachably connected to the reference body (30).

12. Method according to one of claims 1 to 11, wherein the reference body (30) serves as a common reference for further sensor components, such as a camera or height reference for coater / powder height.

13. Manufacturing device (1) for the additive manufacturing of a three-dimensional object (19) by layer-by-layer application and selective solidification of a powder material (15) within a construction field in a processing plane (18), wherein the manufacturing device (1) comprises: - at least one beam deflection unit (9a, 9b, 9c) which is designed to direct a beam (11a, 11b, 11c) generated by a respective beam generation unit (10a, 10b, 10c) to different target points in the processing plane (18) which lie within a scanning area assigned to the respective beam deflection unit (9a, 9b, 9c), - a reference body (30) which is arranged in the construction field in the processing plane (18), wherein the reference body (30) has a plurality of markings (31) which are arranged at predetermined positions of the reference body (30), - a detection device (50) which is arranged to detect light of the beam (11a, 11b, 11c) remitted along an optical axis (A) of the beam (11a, 11b, 11c), wherein the detection device (50) is arranged on an optical axis (A) of the beam (11a, 11b, 11c), and - a control device (5) which is designed to control the beam deflection unit (9a, 9b, 9c) for displacing the beam (11a, 11b, 11c) in the processing plane (18) over areas on the reference body (30) which contain one or more markings (31), in order to detect location-dependent signal values ​​of the detection device (50) during the displacement of the beam (11a, 11b, 11c), in order to assign a signal value of the detection device (50) to each location of the displacement of the beam (11a, 11b, 11c) in the processing plane (18), in order to obtain spatially resolved information about the positions of the markings (31) on the reference body (30), in order to to compare spatially resolved information with the predetermined positions of the markings (31) on the reference body (30) in order to calculate an alignment error between the beam (11a, 11b, 11c) and the predetermined positions of the markings (31) on the reference body (30), and to compensate for the alignment error by adjusting the location-dependent positioning of the beam (11a, 1 lb, 11c) to be corrected.

14. Manufacturing device according to claim 13, wherein the beam generating unit (10a, 10b, 10c) comprises a laser or is designed as a laser.

15. Manufacturing device according to claim 13 or 14, wherein the detection device (50) comprises a photodiode (40) or is designed as a photodiode (40), or wherein the Detection device (50) is designed as a planar sensor, such as a camera, preferably with low resolution, 4-quadrant diode, point sensors.

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