CALIBRATION SYSTEM AND METHOD FOR CALIBRATING A BUILD PLATFORM SYSTEM IN ADDITIVE MANUFACTURING APPARATUS - Patent application

Abstract

The present invention relates to a calibration system and method for calibrating a build platform system (1) arranged in a build space (2) of a laser-based additive manufacturing device. The calibration system includes a calibration plate (5) that can be fixed on the build platform system (1) and an optical module (4). The calibration plate (5) is made of a metallic substrate and has a surface layer of a contrasting color relative to the metallic substrate. A calibration pattern (6) is machined on the calibration plate (5) for calibrating the build platform system (1). The calibration pattern (6) is acquired in the form of an image by an optical detection unit (4.1). By evaluating the image, correction values ​​are determined, which serve to calibrate the build platform system (1) in the additive manufacturing device. Preferred fields of use for the calibration system and method are hybrid additive manufacturing of new components and the repair of conventionally manufactured or additively manufactured components (3).

Description

[Technical Field]

[0001] The present invention relates to a calibration system and method for calibrating a build platform system located in a build space of a laser-based additive manufacturing apparatus. Preferred fields of use for the calibration system and method are hybrid additive manufacturing of novel components and repair of conventional or additively manufactured components. [Background technology]

[0002] Additive manufacturing methods such as selective laser powder bed fusion (LPBF) are primarily conceived for producing complete new components with shapes close to their final contours. Based on a virtual 3D component model, material is solidified layer by layer on the build platform of the additive manufacturing machine until the component shape defined by this 3D model is completed. The starting material for producing high-value metallic components using selective laser powder bed fusion is usually a precisely defined and therefore costly metal powder, which is only partially melted to form the additively manufactured component. The majority of the powder acts exclusively as a filler and support material.

[0003] Additive manufacturing of metallic components by selective laser melting may still not be economically viable compared to conventional manufacturing methods in many fields due to long manufacturing times, poorly known material data, and high powder consumption. However, additive manufacturing is already well established when it comes to manufacturing high-value, geometrically complex or customized components, especially in the aeronautics or medical technology fields.

[0004] In addition to producing new parts, additive manufacturing also offers the possibility of repairing components to a shape close to the final contour. In the aircraft engine industry, for example, parts of rotating blades or guide vanes are repaired by adding additional buildup or deposition to the worn material.

[0005] Additive manufacturing, which deposits material onto an existing component or element in a shape that approximates the final contour, is also called hybrid (additive) manufacturing. Unlike full manufacturing, hybrid manufacturing requires precise positioning of the component within the manufacturing equipment or precise knowledge of the component's orientation on the build platform.

[0006] Generally, the component of an additive manufacturing apparatus on which a component is manufactured is referred to as a build platform. In the context of this disclosure, the entirety of all equipment components of an additive manufacturing apparatus that support the component to be manufactured is referred to as a build platform system, with the narrower definition of a build platform being understood to be the typically plate-like equipment element onto which the component to be additively manufactured is directly attached. Thus, a build platform system includes at least one build platform, and in its simplest structural configuration, a build platform system is limited to a build platform.

[0007] During hybrid additive manufacturing of a component, material is applied by additive deposition onto an existing substrate, hereinafter referred to as a base body. The additively deposited part of the calibration element, i.e. the deposition body, together with the base body forms a component after the additive manufacturing is completed.

[0008] For laser-based additive manufacturing methods, such as selective laser melting with a powder bed, hybrid additive manufacturing presents the challenge of controlling the laser (or more precisely, the laser scanner) in a separate coordinate system, i.e., the laser coordinate system. Geometry data for the build platform system and, if applicable, the base body present on the build platform system, are transmitted to the laser control unit, i.e., transferred to the laser coordinate system, before the additive manufacturing process begins. After this data transmission, the laser coordinate system is independent from the coordinate system that defines the actual orientation of the build platform system in the build space and the orientation of the base body already present on the build platform system. This latter coordinate system is called the build space coordinate system. When the base body is located at a defined position in the build space, the laser (or the laser spot) does not always hit the base body precisely enough during hybrid additive manufacturing. For each position of an object located in the build space that can be defined by build space coordinates in the build space coordinate system, a deviation, also called an offset, occurs between the build space coordinates in the build platform coordinate system and the laser coordinates in the laser coordinate system.

[0009] To achieve high-precision control of the laser, and ultimately to ensure high accuracy in hybrid additive manufacturing, the build space coordinates can be corrected with correction values, and this corrected orientation information of the build platform system and base body can be transferred to the laser coordinate system.

[0010] The correction values ​​for the build space coordinates themselves can be determined by a calibration performed in the additive manufacturing machine. Calibration methods used for this purpose are usually based on photographic image detection of the pattern and reference markings. Such calibration methods—and the calibration devices or systems used for them—are known, inter alia, from EP 0 792 481 A1, DE 19918 631 A1, U.S. Pat. No. 6,483,596 A1, WO 2017 / 158327 A1, or DE 102021105918 A1. WO 2017 / 158327 A1 describes a calibration method in which a calibration pattern is machined into an aluminum plate using a laser from an additive manufacturing machine.

[0011] Furthermore, EP 4151342 A1 discloses a manufacturing system for additively manufacturing a workpiece, the manufacturing system comprising, inter alia, a build plate and an optical device for detecting image data of the build plate.WO 2020 / 212108 A1 describes a calibration method for a camera provided for monitoring an additive manufacturing process, in which an additively manufactured component is compared with a pattern on the component to calibrate the camera.

[0012] These known calibration methods and the calibration devices or systems used for these calibration methods usually focus on classical additive manufacturing, i.e. the production of completely new parts, or involve intervention in the machine control system. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] European Patent No. 0792481 [Patent Document 2] German Patent Application Publication No. 19918631 [Patent Document 3] U.S. Patent No. 6,483,596 [Patent Document 4] International Publication No. 2017 / 158327 [Patent Document 5] German Patent Application Publication No. 102021105918 [Patent Document 6] European Patent Application Publication No. 4151342 [Patent Document 7] International Publication No. 2020 / 212108 Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to improve a calibration system and a calibration method for calibrating a build platform system arranged in a build space of an additive manufacturing device, to enable accurate material deposition in hybrid laser additive manufacturing of calibration parts without requiring intervention in the machine control device. [Means for solving the problem]

[0015] This problem is solved by a calibration system having the features of claim 1 and by a calibration method according to claim 8. Expedient refinements of the invention are described in claims 2-7 and claims 9-11.

[0016] The calibration system and calibration method performed using the calibration system described below are useful for calibrating a build platform system located within a build space of an additive manufacturing device, where the additive manufacturing device has a controllable laser that solidifies material on the build platform system during additive manufacturing. In a general-purpose additive manufacturing device, such as a powder-bed selective laser melting installation, the build space is located within a build well, within which a build platform system is installed that is adjustable in at least height.

[0017] When a component is additively manufactured in this way using a laser on a build platform system of an additive manufacturing machine, the orientation of the build platform system in the build space—like all other objects in the build space—is defined by build space coordinates in the build space coordinate system. That is, in the case of hybrid additive manufacturing of a component consisting of a base body and a deposition body that is additively deposited on this base body, the orientation of the base body is also described by these build space coordinates in the build space coordinate system. The build space coordinates are transmitted to a control unit of the additive manufacturing machine that is provided for controlling the laser before additive manufacturing begins.

[0018] The calibration of the build platform system described below is based on transmitting known build space coordinates provided for controlling the laser, generated, for example, based on a computer model or based on preliminary measurements outside the additive manufacturing device, together with correction values ​​or correction factors for each individual build space coordinate to the control unit of the additive manufacturing device, thereby directing the laser as intended to a predefined actual position within the build space.

[0019] Therefore, determining these correction values ​​is the narrower purpose of the calibration method described below and the calibration system used for this calibration method.

[0020] According to the measures of the invention, the proposed calibration system comprises an optical system module and a calibration plate made of a predetermined substrate, preferably made of metal, which can be fixedly positioned on a build platform system.

[0021] The optical module includes an optical detection unit, an optical mount, and a mounting plate covering the build space of the additive manufacturing device. The mounting plate has an optical passage cutout, in the area of ​​which the optical detection unit is attached using the optical mount so as to be able to optically detect a calibration plate arranged in the build space. The optical detection unit is usually located on the side of the mounting plate facing away from the build space. Preferably, the optical axis of the optical detection unit is aligned perpendicular to the mounting plate. The optical detection unit can be, for example, a camera or a—preferably high-resolution—optical fringe projection unit.

[0022] On the build space side, lighting means for illuminating the build space, for example in the form of light-emitting diodes, are attached to the mounting plate, and the lighting means are preferably evenly distributed on the build space side of the mounting plate.

[0023] The calibration plate has a visible surface on one of its two planar sides, which faces the optical detection unit when the calibration system is properly assembled. The visible surface of the calibration plate has a surface layer that is contrasting in color with the substrate. That is, the surface layer has a clear color contrast with the color of the substrate. Preferably, the surface layer is dark, e.g., black, while the uncoated substrate has a light appearance (often a silver-metallic appearance in the case of a metallic substrate).

[0024] The calibration system may further include one or more fiducial mark supports each having a fiducial marking. These fiducial mark supports can be fixed to the build platform system at precise positions, and these fiducial mark supports serve as reference points for the build platform system fixed in the additive manufacturing apparatus. To ensure the optical detection unit's visibility to the fiducial markings, fiducial marking notches may be machined into the calibration plate.

[0025] A calibration method according to the present invention for calibrating a build platform system regularly mounted in a build space of a laser-based additive manufacturing device is performed by the above-mentioned calibration system including an optics module, a calibration plate, and a fiducial mark support with fiducial markings, and by an evaluation unit for evaluating attitude parameters to determine the above-mentioned correction values.

[0026] To calibrate the build platform system, the calibration plate and fiducial mark support are fixed in position such that when the visible surface of the calibration plate is viewed from above, the visible surface and the fiducial markings are simultaneously visible.

[0027] On the visible side of the calibration plate, a calibration pattern, also two-dimensional, consisting of two-dimensional pattern elements is produced in the visible surface plane of the calibration plate using a laser of the additive manufacturing device. The orientation of the individual pattern elements is defined by target orientation parameters. The target orientation parameters are stored in a computer model and transmitted to a control unit of the additive manufacturing device in the form of build space coordinates. Based on the target orientation parameters, a calibration pattern is produced, which is then detected in the form of actual orientation parameters. The evaluation unit is configured to determine correction values ​​for the build space coordinates based on a target-actual comparison between the predetermined target orientation parameters and the detected actual orientation parameters, taking into account and in relation to reference markings attached to the build platform system. Mathematical methods for determining correction values ​​based on a two-dimensional target-actual pattern comparison are basically known and will not be described further here.

[0028] According to the invention, the calibration method is carried out in the following method steps:

[0029] In a first step, the calibration plate and one or more fiducial mark supports with the fiducial markings are fixed to a build platform system arranged in the build space of an additive manufacturing machine, the build platform system itself being installed in the additive manufacturing machine as required.

[0030] In a next step, a controllable laser is used to locally remove, or ablate, the surface layer on the visible surface of the calibration plate, thereby fabricating a calibration pattern consisting of a plurality of pattern elements. In this case, the calibration pattern extends across the entire visible surface of the calibration plate. The local ablation results in a surface in the area of ​​the pattern elements that is a contrasting color relative to the surrounding surface layer. A dark periphery of a light pattern element has been found to be particularly suitable. Preferably, the laser is operated with parameters typical for a process for additive manufacturing in an additive manufacturing device when fabricating the calibration pattern on the calibration plate.

[0031] In a subsequent step, the build platform system together with the calibration plate mounted on the build platform system is brought into a predetermined position within the build space, i.e., into a predetermined operating distance of the optical detection unit, for example by lowering it into a build well of the additive manufacturing equipment.

[0032] In a next step, the optics module is mounted in the build space, with the mounting plate of the optics module covering the build space, preferably dimensioned so that the build space is completely shielded from the intrusion of ambient light due to the slight excess dimensions of the mounting plate.

[0033] In this position, a (preferably digital) image of the calibration plate is now acquired using the optical detection unit. This image may be, for example, a photograph or a point cloud. Preferably, the optical axis of the optical detection unit is aligned perpendicular to the calibration plate in order to acquire an image of the calibration plate without distortion in appearance.

[0034] The acquired image of the calibration plate is finally evaluated in an evaluation unit, i.e., actual orientation parameters are measured for each individual pattern element of the calibration pattern, and based on this, correction values ​​for the build space coordinates are then determined, also using the evaluation unit.

[0035] One advantage of the calibration system and method according to the present invention is the use of a calibration plate with a surface layer that is locally ablated by a laser to machine a calibration pattern, which ablation requires adjusting the laser parameters, e.g., the laser power, relatively close to the laser parameters during additive manufacturing of the component.

[0036] This form of calibration pattern production ensures that all machine-induced deviations are accurately reproduced in the detected image of the calibration pattern. Highly accurate spatially resolved correction values ​​can be determined for each position of the build platform system. Since the build space coordinates with the correction values ​​are transmitted to the control unit that controls the laser, no intervention is required in the control system, i.e., no intervention in the machine control of the additive manufacturing equipment. This is particularly important when the additive manufacturing equipment is subject to certification requirements. Due to the lack of intervention in the machine control of the additive manufacturing equipment, equipment certification is maintained when using the calibration methods described herein.

[0037] Another advantage of the compact configuration of the optics module with the mounting plate is that no external light enters the build space during image acquisition: the calibration plate is always uniformly illuminated during image acquisition via predefined illumination means attached to the mounting plate on the build space side.

[0038] Calibrating a build platform system in an additive manufacturing device using the calibration methods described above can be performed quickly and simply, with the calibration process typically taking only a few minutes.

[0039] The calibration system and method are - based on the improved manufacturing accuracy during additive manufacturing due to the calibration - particularly suitable for reducing costs during hybrid additive manufacturing of new parts, during repair of additively designed components and conventionally manufactured components, or during repair of additively manufactured components after so-called "failed build jobs", i.e., repairs to correct erroneous additive deposition.

[0040] The build platform system is preferably configured as described in German Patent Application No. DE 102022129035.2 or International Patent Application No. PCT / DE2023 / 150027, the contents of which are hereby incorporated by reference.

[0041] According to one configuration of the calibration system, a material is selected as the substrate forming the calibration plate, which corresponds to the material of the component to be additively manufactured or is particularly similar in terms of manufacturing parameters. Usually, this is a metallic substrate. In this case, for example, steel has proven to be relatively universally usable in this respect. Generally, a material with a viscosity of 4 g cm -3 ~10g·cm -3 Preferably, a metallic material having a density in the range of is used as the substrate of the calibration plate.

[0042] To improve contrast, the surface layer on the visible side of the calibration plate preferably has a matte appearance. This surface layer can be an adhesion layer or a conversion layer, i.e., a surface layer resulting from conversion of the surface of the substrate. Preferably, the surface layer is an oxidation conversion layer of the—especially metallic—substrate of the calibration plate, such as a black oxide layer if the substrate is steel, or an anodized layer if the substrate is titanium or aluminum. The oxidation conversion layer provides very good adhesion, i.e., is abrasion-resistant, and usually has a matte appearance. It can be appropriately colored, unless it is already darkly colored.

[0043] Besides metallic materials, glass materials, for example, can also be used as the substrate for the calibration plate.

[0044] According to another configuration, the optical module of the calibration system includes one or more sensors. Such sensors may be distance sensors that detect the distance between a calibration plate fixedly positioned on the build platform system and an optical detection unit attached to the build space. Suitable distance sensors are, in particular, inductively operated distance sensors or laser-based distance sensors. The distance sensors allow for precise adjustment or recalibration of the predetermined operating distance of the optical detection unit.

[0045] Furthermore, the optical system module may have a tilt sensor to determine the alignment of the optical detection unit and / or to monitor the vertical alignment of the optical detection unit. The tilt sensor is used to ensure that the optical detection unit is aligned (vertically) without tilt within the optical system module. The calibration plate and / or the build platform system below the calibration plate may also be equipped with a tilt sensor to confirm or ensure the vertical alignment of the optical axis of the optical detection unit relative to the calibration plate. If a tilt is detected, it can be mathematically compensated or corrected later within the framework of the evaluation.

[0046] Alternatively, the tilt can be ascertained via multiple distance sensors, which determine the distance between the optics module and the calibration plate at, for example, three or four positions.

[0047] Furthermore, a temperature sensor may be installed in the optical module to verify whether a predetermined measurement temperature or a predetermined measurement temperature range is maintained for the optical detection unit and the calibration plate.

[0048] The optical module may further comprise an RFID transponder for contactless data storage and data interrogation of identification data. The abbreviation RFID (English: radio-frequency identification) is a known technology for automatically and contactlessly identifying and locating objects using radio waves, and an RFID system usually includes an RFID transponder and a reader. The RFID transponder of the optical module can be used to control access to the calibration system, for example, with the release of the calibration system having to be authorized by an operator.

[0049] For example, in larger additive manufacturing equipment with multiple lasers, i.e., so-called multi-laser systems, it may be provided that the optical module has multiple optical detection units, and each of the multiple lasers is assigned to one of these optical detection units. This allows calibration to be performed simultaneously for each processing field of each specific laser. According to another configuration of the optical module, the optical module may have a movable, for example positionably adjustable, optical detection unit. For this purpose, the optical detection unit is moved to a defined position in order to sequentially acquire images for each processing field of each specific laser.

[0050] The reference mark support of the calibration system can be configured in different ways, for example as a positioning pin that is insertable and fixed in position into the build platform system, and is preferably attached to the build platform system so that its reference markings are flush with the visible surface of the calibration plate—to avoid visibility defects during image acquisition.

[0051] Preferably, a plurality of evenly distributed fiducial marking supports or fiducial markings are mounted on the build platform system, for example, four fiducial markings arranged at the corners of a rectangle and one fiducial marking arranged in the center. Via the fiducial markings, possible tilt of the optical detection unit relative to the calibration plate can be mathematically compensated for. In this case, a homography matrix is ​​determined via the defined and known fiducial markings. Based on this, an "untilted" image can be calculated by multiplying each point of the image by the homography matrix.

[0052] As an alternative to locating pins, any other form of fiducial marking support that can be defined and fixed in position on the build platform system can be used, for example a magnetic hemisphere.

[0053] The calibration plate can be fixed in position on the build platform system using, for example, a screw connection. Alternatively, a magnetic mount can be used, the advantage of which is that no mounting element loses area on the visible surface, thus providing more space for the pattern elements of the calibration pattern.

[0054] According to one configuration, the calibration system may have a calibration platform that fixes the calibration plate in the build platform system, where the calibration plate is mounted on the calibration platform. A unit consisting of the calibration plate and the calibration platform is mounted to the build platform system for calibration. The reference mark support is then fixedly installed on the calibration platform at a precise position. To calibrate the build platform system, the calibration plate and the reference mark support are mounted or can be fixed in position on the build platform system via the calibration platform, i.e., indirectly.

[0055] According to one configuration of the calibration method, the calibration pattern machined into the surface layer on the visible surface of the calibration plate using a laser comprises a plurality of individual pattern elements, each having the same two-dimensional geometric shape, spaced apart from one another in rows and columns on the visible surface of the calibration plate, and preferably having a minimum spacing between adjacent pattern elements in the same row or column that is equal to or greater than the extension or extent of the pattern element.

[0056] Each individual pattern element preferably has four-fold rotational symmetry, at least two straight line segments perpendicular to each other, and an individual circle or point element. One example of such a pattern element configuration is a crosshair consisting of two straight line segments perpendicular to each other and intersecting in the middle, with the intersection of the crosshairs simultaneously forming an individual point element. Another pattern element configuration is a square with an inscribed circle element. Due to the four-fold rotational symmetry, the individual circle or point element is necessarily always located at the center point of the pattern element. Based on the circle or point element, the pattern element's orientation coordinate or position in a plane is determined as part of its orientation parameters, and based on the line segments, the angular rotation is determined as part of the orientation parameters. If target orientation parameters for a specific pattern element of the calibration pattern are set, e.g., defined in the form of a target X orientation coordinate, a target Y orientation coordinate, and a target angular position, an actual X orientation coordinate, an actual Y orientation coordinate, and an actual angular position are obtained after evaluating an image of the calibration pattern for this pattern element. Based on the difference, i.e. by means of a target-actual comparison of the attitude parameters, a correction value is determined for each build space coordinate in the build space coordinate system using an evaluation unit.

[0057] The invention will now be explained in more detail by way of example and with reference to the diagrammatic drawings in which the same or similar features are provided with the same reference numbers. [Brief explanation of the drawings]

[0058] [Figure 1] FIG. 1 is a perspective view of a build platform system with components attached. [Figure 2] FIG. 1 is a perspective view of a calibration system installed in an additive manufacturing device according to a first embodiment. [Figure 3] 1 is a perspective view of a calibration system according to a first embodiment, prior to application of a calibration pattern; FIG. [Figure 4] 1 is a perspective view of a calibration system according to a first embodiment after application of a calibration pattern; FIG. [Figure 5]FIG. 1 is a top plan view of a calibration plate with a calibration pattern. [Figure 6] FIG. 10 illustrates a target-actual comparison of posture parameters based on pattern elements. [Figure 7] FIG. 10 is a perspective view of a calibration system according to a second embodiment. [Figure 8] FIG. 10 is a perspective view of a calibration system according to a second embodiment. [Figure 9] FIG. 10 is a perspective view showing details of a calibration system according to a second embodiment. [Figure 10] FIG. 10 is an exploded view showing details of a calibration system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0059] According to an embodiment (see FIG. 1 ), the build platform 1 to be calibrated comprises a machine interface unit 1.1 and a build platform 1.2 that can be fixed at a precise position on the machine interface unit 1.1, and the build platform 1.2 itself supports components 3. FIG. 1 shows 48 components 3 manufactured by hybrid additive manufacturing, here, turbine blades for an aircraft engine, for example. Within the framework of hybrid additive manufacturing, stacked bodies 3.2, in each case, blade tips of turbine blades, are additively deposited onto the base body 3.1 of the component 3, thereby resulting in a complete component 3 from the base body 3.1 and the stacked bodies 3.2. Because the base body 3.1 is fixedly anchored on the build platform 1.2, which itself is fixedly locked on the machine interface unit 1.1, before the start of manufacturing, it is only necessary to calibrate the machine interface unit 1.1 for this build platform system 1.

[0060] With regard to the build platform system 1 illustrated in this embodiment, and in particular with regard to the specific structure of this build platform system 1, further reference is made to the specification of International Patent Application PCT / DE2023 / 150027, the contents of which are to be considered as part of this patent application.

[0061] The additive manufacturing apparatus shown in Figure 2 has a build well, the interior space of which is a build space 2. Inserted within the build space 2 is a build platform system 1 in the form of a machine interface unit 1.1 with a calibration plate 5 mounted on the machine interface unit 1.1.

[0062] An optics module 4 is installed above the build well, with a mounting plate 4.3 mounted on the build well wall over the build well to prevent ambient light from entering the build space 2 during image (here, photograph) capture of the calibration plate 5. An optical detection unit 4.1, here a camera, used for image capture is attached to the mounting plate 4.3 using an optics mount 4.2 such that the optical axis or field of view of the optical detection unit 4.1 is aligned perpendicular to the mounting plate 4.3. Thus, when the optics module 4 is installed as specified, the optical axis of the optical detection unit 4.1 is directed vertically into the build space 2 of the additive manufacturing device and perpendicular to the calibration plate 5.

[0063] In FIG. 3, a first embodiment of a calibration system for calibrating a build platform system 1 in the form of a machine interface unit 1.1 is illustrated in structural detail.

[0064] The mounting plate 4.3 has on its underside (not visible) a light emitting diode that illuminates the calibration plate 5. The optical detection unit 4.1 of the optics module 4 is mounted on a light passage notch (not numbered) of the mounting plate 4.3 using an optics mount 4.2.

[0065] 3, before machining of the calibration pattern 6, the calibration plate 5 fixed in position on the machine interface unit 1.1 has five reference mark notches 5.1 that allow the optical detection unit 4.1 to see a reference marking 8 centrally attached to the end face of the reference mark carrier 7. According to the present embodiment, the reference mark carrier 7 is formed as a calibration locating pin 7.1 that fits into the machine interface unit 1.1 or as a hemispherical element 7.2 that can be magnetically fixed in the machine interface unit 1.1.

[0066] The calibration plate 5 is mounted on the machine interface unit 1.1 using mounting screws 9, with a spacer 10 inserted between the calibration plate 5 and the machine interface unit 1.1. The spacer 10 ensures that the fiducial marks 8 lie in a plane with the visible surface of the calibration plate 5.

[0067] The calibration system shown in Figure 4 corresponds to the calibration system shown in Figure 3, but further shows a calibration pattern 6 consisting of individual pattern elements 6.1 arranged periodically in rows or columns, machined on the visible side of the calibration plate 5 using a laser in an additive manufacturing device.

[0068] In Figure 5, a plan view from above of the visible side of the calibration plate 5 shown in Figure 4 is shown. The image created within the scope of the calibration method corresponds to the drawing shown in Figure 5. Based on this image, the actual pose parameters for each two-dimensional pattern element 6.1 are determined and processed by means of an evaluation unit.

[0069] Figure 6 shows a target-actual comparison of target and actual attitude parameters for one pattern element 6.1 of multiple pattern elements 6.1 in a coordinate system. The target attitude parameters of the two-dimensional pattern element 6.1 are the two set target attitude coordinates X and Y and the target angular position in a two-dimensional plane. According to the settings, the pattern element 6.1 has no twist, i.e., it always has a target angular position of 0°. The actual attitude parameters determined by the photograph are the two measured actual attitude coordinates X' and Y' of the pattern element 6.1 and the measured angular position deviation R'.

[0070] 7-10 illustrate a second embodiment of a calibration system for calibrating the build platform system 1. As shown in FIG.

[0071] On the mechanical interface unit 1.1—see FIG. 7 in this regard—is mounted a calibration platform 1.3 on which a calibration plate 5 is mounted for calibrating the mechanical interface unit 1.1. The optics module 4 located thereon includes an optical detection unit 4.1, here also a camera (the camera's objective is visible in FIG. 7), an optics mount 4.2, and a plate-like cover. This cover is a sandwich structure consisting of a mounting plate 4.3 that closes downwards, an LED panel, and a diffusion plate. FIG. 8, a view corresponding to FIG. 7, shows the housing 4.4 of the optics module 4. This housing 4.4 accommodates or shields the optical detection unit 4.1, the optics mount 4.2, and the plate-like cover.

[0072] A detailed view of the machine interface unit 1.1, the calibration platform 1.3 and the calibration plate 5 mounted on the calibration platform 1.3 according to a second embodiment of the calibration system is evident from FIGS.

[0073] The calibration pattern 6 shown in Figure 9, consisting of individual pattern elements 6.1 arranged periodically in rows or columns, which are machined on the visible side of the calibration plate 5 using a laser of an additive manufacturing device, differs from the first embodiment of the calibration system shown in Figure 4 in terms of the arrangement of the pattern elements 6.1.

[0074] The calibration plate 5, which is fixed in position on the calibration platform 1.3 using mounting screws 9, has five reference mark notches 5.1 that allow the optical detection unit 4.1 to see a reference marking 8 centrally provided on the end face of the reference mark support 7.

[0075] According to a second embodiment, the reference mark carriers 7 are formed as calibration pins 7.3, which are fixedly mounted on the calibration platform 1.3 (see FIG. 10 in this regard). The calibration plate 5 has a thickness corresponding to the height of the calibration pins 7.3, so that the reference marks 8 lie in a plane with the visible surface of the calibration plate 5.

[0076] As can also be seen in FIG. 10, the calibration platform 1.3 is positionally mountable on the machine interface unit 1.1 by a zero point clamping system guided by locating pins. [Explanation of symbols]

[0077] 1 Build Platform System 1.1 Machine Interface Unit 1.2 Build Platform 1.3 Calibration Platform 2 Build Space 3. Components 3.1 Base molded body 3.2 Deposited compact 4 Optical module 4.1 Optical detection unit 4.2 Optical system mount 4.3 Mounting Plate 4.4 Housing 5 Calibration Plate 5.1 Reference mark notch 6 Calibration Pattern 6.1 Pattern Elements 7 Reference Mark Support 7.1 Calibration Locating Pin 7.2 Hemispherical elements 7.3 Calibration Pin 8 Fiducial Markings 9 Mounting screws 10 spacer X,Y Predetermined target posture coordinates X',Y' Measured actual posture coordinates R' Measured angular position deviation

Claims

1. 1. A calibration system for calibrating a build platform system (1) arranged in a build space (2) of an additive manufacturing apparatus, the additive manufacturing apparatus having a controllable laser for solidifying material during additive manufacturing on the build platform system (1), the calibration system comprising: a calibration plate (5) positionably fixable on the build platform system (1); and an optical system module (4), the calibration plate (5) consists of a given substrate, the calibration plate (5) has a visible surface on one of its two planarly extending plate sides, the visible surface being provided with a surface layer of a contrasting color to the substrate, - the optical system module (4) comprises an optical detection unit (4.1), an optical system mount (4.2) and a mounting plate (4.3) covering the build space (2) of the additive manufacturing device, the optical detection unit (4.1) being attached to the mounting plate (4.3) by means of the optical system mount (4.2) in the area of ​​an optical passage notch provided in the mounting plate (4.3) for optical image detection of the calibration plate (5) fixed in position on the build platform system (1), and an illumination means being attached to the mounting plate (4.3) on the build space side for illuminating the build space (2).

2. 2. The calibration system according to claim 1, characterized in that the surface layer of the visible side of the calibration plate (5) is an oxidation conversion layer consisting of the base material of the calibration plate (5).

3. 3. The calibration system according to claim 2, characterized in that the calibration plate (5) is made of a steel material and the surface layer on the visible side of the calibration plate (5) is a black oxide layer.

4. 4. Calibration system according to claim 1, characterized in that the lighting means attached to the mounting plate (4.3) on the build space side are uniformly distributed light-emitting diodes.

5. 5. The calibration system of claim 1, wherein the optical system module (4) comprises one or more sensors, at least one of which is a distance sensor that detects the distance of the calibration plate (5), which is fixedly positioned on the build platform system (1), to the optical detection unit (4.2), which is attached to the build space (2).

6. 6. The calibration system according to claim 1, further comprising one or more reference mark supports (7) each having a reference marking, the reference mark supports (7) being fixable to the build platform system (1) at precise positions, and the calibration plate (5) having a reference mark notch (5.1) that enables the optical detection unit (4.1) to view the reference marking (8) of the reference mark support (7) fixed to the build platform system (1) when the calibration plate (5) is attached to the build platform system (1).

7. 7. The calibration system of claim 6, further comprising a calibration platform (1.3) for positionally fixing the calibration plate (5) on the build platform system (1), and the reference mark support (7) is fixedly installed on the calibration platform (1.3) at a precise position.

8. 1. A method for calibrating a build platform system (1) arranged in a build space (2) of an additive manufacturing apparatus, the additive manufacturing apparatus having a controllable laser for solidifying material during additive manufacturing on the build platform system (1), - the orientation of the build platform system (1) and the orientation of an object mounted on the build platform system (1) in the build space (2) are defined by build space coordinates in a build space coordinate system; and - determining correction values ​​for the build space coordinates using an evaluation unit based on a target-actual comparison of predetermined target and detected actual pose parameters of two-dimensional pattern elements (6.1) of the laser-generated calibration pattern (6) relative to one or more fiducial markings (8) attached to the build platform system (1). In the method, The calibration method is carried out with the evaluation unit and the calibration system according to claim 6 in the following method steps: - fixing the calibration plate (5) and the one or more fiducial mark supports (7) with the fiducial markings (8) to the build platform system (1) arranged in the build space (2) of the additive manufacturing device; - machining on said calibration plate (5) a calibration pattern (6) extending over said visible surface of said calibration plate (5) by locally ablating a surface layer on said visible surface of said calibration plate (5) using the controllable laser of said additive manufacturing device; - positioning the build platform system (1) with the calibration plate (5) in the build space (2) at a predetermined working distance of the optical detection unit (4.1); - mounting the optical module (4) in the build space (2) and covering the build space (2) with the mounting plate (4.3) of the optical module (4); - acquiring an image of said calibration plate (5) using said optical detection unit (4.1); evaluating the image of the calibration plate (5) using the evaluation unit and determining correction values ​​for the build space coordinates; A calibration method characterized by being carried out by

9. The calibration pattern (6) machined into a surface layer on the visible surface of the calibration plate (5) using the laser comprises a number of individual pattern elements (6.1) having identical two-dimensional geometric shapes, the pattern elements (6.1) being arranged on the visible surface of the calibration plate (5) spaced apart from one another in rows or columns, and each individual pattern element (6.1) having: -4-fold rotational symmetry, - at least two straight line segments that are perpendicular to each other, and - Individual circle or point elements 9. The calibration method of claim 8, further comprising:

10. 10. The calibration method according to claim 9, characterized in that each pattern element (6.1) has a minimum spacing with respect to each adjacent pattern element (6.1) in the same row or column that is equal to or greater than the extension length of said pattern element (6.1).

11. 11. The calibration method according to any one of claims 8 to 10, characterized in that the laser is operated at parameters typical for a process for additive manufacturing in the additive manufacturing device when machining the calibration pattern (6) on the calibration plate (5).

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