Method for measuring an additive manufacturing apparatus, measuring system for an additive manufacturing apparatus, and additive manufacturing apparatus

Abstract

The invention relates to a method for measuring an additive manufacturing apparatus, in which a measuring system comprising a measuring plate and a measuring bridge is provided, the measuring bridge comprising at least one distance measuring sensor. In an initial state, the measuring bridge rests on the measuring plate and a first distance between the measuring bridge and a first surface point on the measuring plate is measured. In a measuring state, the measuring bridge is in a predetermined pose with respect to a process chamber of the manufacturing apparatus and the measuring plate is movable in relation to the process chamber by a drive system of the manufacturing apparatus. In the measuring state, a distance is measured in order to record a difference between the first distance and a second distance between the measuring bridge and a second surface point on the measuring plate. A measuring system and a manufacturing apparatus are also described.

Description

[0001] Method for measuring an additive manufacturing apparatus, measuring system for an additive manufacturing apparatus, and additive manufacturing apparatus

[0002] The present invention relates to a method for measuring an additive manufacturing apparatus, a measuring system for an additive manufacturing apparatus, and an additive manufacturing apparatus.

[0003] The term additive manufacturing generally refers to processes in which a three-dimensional workpiece is produced by the targeted addition of material. For example, a layer of powdered raw material can be solidified by targeted irradiation with an energy beam (e.g., an electron or laser beam) or by the targeted application of solidifying material such as epoxy resin. The raw material can be plastic granules, a metal powder, a powder made of a metal alloy, or mixtures of different metal (alloy) powders. Additive manufacturing processes are also known in which a liquid raw material is locally polymerized by targeted irradiation.

[0004] Some additive manufacturing devices include a process chamber in which additive manufacturing, in particular the selective layer-by-layer solidification of the raw material, takes place. A desired process atmosphere can be set in the process chamber, in particular an oxygen-poor or oxygen-free atmosphere. For this purpose, a gas mixture with a desired composition can be fed into the process chamber, which is designed to be particularly gas-tight. The raw material is introduced into the process chamber and then solidified at the desired locations. This creates one layer of the three-dimensional workpiece. After the selectively solidified layer has been covered by additional raw material, further selective solidification takes place. This allows a workpiece to be additively manufactured layer by layer.

[0005] Some additive manufacturing devices are designed to produce the three-dimensional workpiece on a build plate which is movable relative to the process chamber by means of a drive system. The build plate can in particular be movably mounted in a build cylinder. In this way, a powder layer of the raw material can be applied to the build plate and, after this powder has selectively solidified, the build plate can be lowered by one layer thickness, after which the next powder layer is applied. Such a manufacturing device is known, for example, from EP 3 023 227 B1. To ensure that the raw material is solidified as desired, an additive manufacturing device can be measured in advance. For this purpose, for example, an impact position, a power and / or a caustic of an energy beam of the additive manufacturing device can be measured. The measured values ​​obtained can then be used to optimize the manufacturing device orto adjust individual components of the manufacturing apparatus and / or to control them based on measured values ​​in additive manufacturing, which can also be referred to as calibration.

[0006] Some types of such measurements are preferably performed relative to a reference plane. The position of this reference plane, particularly relative to the process chamber and / or other components of the additive manufacturing equipment, should be known for such measurements.

[0007] Against this background, a method for measuring an additive manufacturing apparatus, a measuring system and an additive manufacturing apparatus are provided.

[0008] Unless otherwise stated, directions used herein (e.g., "up" and "down") refer to the direction of gravity. Objects therefore fall from "up" to "down" due to gravity.

[0009] The additive manufacturing apparatus comprises a process chamber and a drive system. The manufacturing apparatus is configured to produce a three-dimensional workpiece by selectively solidifying a raw material (e.g., powdered and / or metallic) layer by layer (e.g., laser-induced) on a build plate provided in a build cylinder, which is movable relative to the process chamber of the manufacturing apparatus by the drive system.

[0010] The additive manufacturing apparatus comprises, in particular, a solidification device configured to direct an energy beam (e.g., an electron or laser beam) onto the raw material to selectively solidify it. The additive manufacturing apparatus can be designed to solidify the raw material by selective laser melting and / or sintering.

[0011] The build cylinder can be permanently or replaceably coupled to the process chamber. The build cylinder can be essentially trough-shaped or sleeve-shaped. The build cylinder can have an essentially rectangular or square inner contour in plan view. In particular, when the build cylinder is coupled to the process chamber, the build cylinder is open towards the process chamber. In other words, in this state, the interior of the build cylinder is accessible from above from the process chamber, at least if the build plate is positioned accordingly in the build cylinder. The process chamber can have a coupling opening designed for coupling to the build cylinder. When the build cylinder is coupled, the interior of the build cylinder is then accessible from the process chamber (e.g., from above) through the coupling opening. For example, the process chamber has a frame for the coupling opening.

[0012] The build plate can be mounted in the build cylinder so that it can move translationally. The build plate can be arranged on a positioning platform, in particular in an interchangeable manner. The positioning platform can be a permanent component of the production apparatus or can be coupled to the production apparatus together with the build cylinder. The positioning platform can be movable by the drive system. The positioning platform can carry the build plate on an upper side. The positioning platform can be coupled to the drive system by at least one side wall and / or a lower side. The positioning platform can be movable by the drive system, at least translationally (e.g. in the build cylinder). The drive system can be designed to controllably determine a position of the positioning platform and / or the build plate, in particular relative to the process chamber.

[0013] The drive system can be designed to move the positioning platform and / or the build plate up and down. The drive system can comprise at least one drive coupling which has a predetermined position in plan view relative to the positioning platform and / or the build plate. The at least one drive coupling can be in contact with an underside of the positioning platform and serve to transmit a (e.g. translational) movement of a drive unit of the drive system to the positioning platform. Alternatively, it is conceivable for the drive coupling to be in contact with an underside of the build plate. The drive system can comprise a respective drive unit for each drive coupling, for example a (e.g. vertically arranged) spindle drive. The drive system is designed in particular to controllably set or adapt positions of the drive couplings relative to the process chamber.The drive system can also be designed to cause a tilting movement (e.g. roll, pitch and / or yaw) of the positioning platform and / or the build plate, for example by differently adjusting the positions of the drive couplings.

[0014] The process chamber is particularly designed to ensure a controlled process gas atmosphere (e.g., above the surface of a raw material layer) during additive manufacturing. The process chamber may have an access opening that can be closed with a door or window, which, in particular, allows a user of the manufacturing apparatus to reach into the process chamber.

[0015] The manufacturing device can be equipped with the measuring system described herein and / or can be measured. In one variant, the manufacturing device includes the measuring system.

[0016] The manufacturing apparatus comprises, in particular, a control unit which is designed to calibrate and / or control (e.g. in the additive manufacturing of a workpiece) the additive manufacturing apparatus and / or individual components of the manufacturing apparatus (e.g. the solidification device), for example based on the respective difference described below and / or at least one measurement result which was / was obtained according to the method described herein using the manufacturing apparatus and the measurement system described herein.

[0017] The measuring system comprises a measuring plate and a measuring bridge, wherein the measuring bridge comprises at least one distance measuring sensor. The measuring system serves to measure the additive manufacturing apparatus and is particularly designed for use as a measuring system in the method described herein. Thus, the measuring system can also have one, several, or all of the features described herein with reference to the method.

[0018] The measuring plate can be designed to be arranged on the positioning platform, for example instead of the build platform. The measuring plate can be designed to be arranged on the build plate. The measuring plate can have the same outer contour as the build plate in plan view. The measuring plate can be designed such that it is movable in a (e.g. the) build cylinder using the drive system. The at least one distance measuring sensor can comprise a tactile and / or a non-tactile distance measuring sensor or be designed as a (non-)tactile distance measuring sensor. Such a tactile distance measuring sensor can have a measuring probe. The at least one distance measuring sensor can comprise a (e.g. analog or digital) dial gauge or be designed as a (e.g. analog or digital) dial gauge. The distance measuring sensors and / or dial gauges and / or measuring probes can be arranged in the same plane.

[0019] The measuring bridge can comprise at least three support elements, which are designed to rest on the measuring plate in the initial state and to come into contact with respective support points of the process chamber in the measuring state. The measuring bridge can comprise a frame, in particular a metallic frame, on which the support elements are arranged (e.g. as part of the frame or as a component attached thereto). The frame and / or the support elements can be substantially rigid and are in particular manufactured in one piece, for example from metal (e.g. aluminum) or a metal alloy (e.g. stainless steel). For example, the at least one distance measuring sensor is attached to the frame.

[0020] The support points can be provided at an edge of the coupling opening of the process chamber. For example, the frame of the process chamber (e.g., on its top side) has the support points. The support points can be covered by protective caps in standby mode and exposed in measurement mode.

[0021] For example, the at least one (e.g., each) distance measuring sensor is located within a circumference defined by the support elements in a plan view (e.g., in the measuring state). The support elements can be arranged on the outside, in particular at respective outer corners, of the frame, which is polygonal in a plan view (e.g., in the measuring state). The support elements can project downwards beyond the frame in a side view (e.g., in the measuring state), so that the frame, in the initial state, is held by the support elements (e.g., suspended and / or contactless) above the measuring plate.

[0022] For example, the measuring plate is provided with measuring aids designed for subsequent measurements. The measuring aids can, in particular, comprise at least one of the following measuring aids: an optical marking for a preferred impact position of an energy beam of the additive manufacturing apparatus; a positioning aid for establishing a predetermined measuring position of a measuring means, in particular a measuring device (e.g., energy, focus, caustic, flow, gas composition, or temperature), on the measuring plate; an optical calibration pattern for detection by an optical sensor of the additive manufacturing apparatus; a radiation source for detection by a sensor of the additive manufacturing apparatus; a robot arm movably supporting a device designed to take measurements and / or perform maintenance of the additive manufacturing apparatus.

[0023] The drive system can be designed to move the measuring plate up and down. The drive system can comprise at least one drive coupling that has a predetermined position relative to the measuring plate (e.g., in the measuring state) in plan view. It is conceivable for the drive coupling to be in contact with an underside of the measuring plate. The drive system can also be designed to cause a tilting movement (e.g., rolling, pitching, and / or yawing) of the measuring plate, for example, by varying the positions of the drive couplings.

[0024] The procedure includes:

[0025] (a) providing the measuring system with the measuring plate and the measuring bridge, wherein the measuring bridge comprises the at least one distance measuring sensor, and wherein the measuring system is provided in an initial state such that the measuring bridge rests on the measuring plate;

[0026] (b) measuring a respective first distance between the measuring bridge and a respective first surface point of the measuring plate by each distance measuring sensor in the initial state of the measuring system;

[0027] (c) arranging the measuring system in a measuring state such that the measuring bridge is arranged in a predetermined pose relative to the process chamber of the manufacturing apparatus and the measuring plate is movable relative to the process chamber by the drive system; and

[0028] (d) performing a distance measurement with each distance measuring sensor to detect a respective difference between (i) the respective first distance and (ii) a respective second distance between the measuring bridge and a respective second surface point of the measuring plate.

[0029] In step (b), if there are multiple distance measuring sensors, several first distances are measured, namely one first distance per distance sensor. In step (d), if there are multiple distance measuring sensors, several second distances are measured, namely one second distance per distance sensor. In this case, the differences are particularly distance-sensor-specific; thus, the difference is determined for each distance measuring sensor from the first and second distances measured by this distance measuring sensor.

[0030] Accordingly, the measuring system is designed such that it can be provided in an initial state such that the measuring bridge rests on the measuring plate, wherein each of the at least one distance measuring sensors is configured to measure a respective first distance between the measuring bridge and a respective first surface point of the measuring plate in the initial state. Furthermore, the measuring system is designed such that it can be arranged in a measuring state such that the measuring bridge is arranged in a predetermined pose relative to the process chamber of the manufacturing apparatus and the measuring plate is movable relative to the process chamber by the drive system, wherein each distance measuring sensor is configured to perform a distance measurement to detect a respective difference between (i) the respective first distance and (ii) a respective second distance between the measuring bridge and a respective second surface point of the measuring plate.

[0031] The measuring bridge can comprise an output unit configured to output information (e.g., electronically and / or optically) relating to the respective first distance, the respective second distance, the respective difference, and / or parameters derived from one or more of these data. The output unit can comprise one or more displays, for example, one display per distance measuring sensor. The output unit can be connected to the control unit of the production apparatus, for example, via a wired or wireless communication link. Thus, the control unit can be supplied with the aforementioned data and / or parameters without manual data entry.

[0032] It is conceivable that in the initial state, the at least three support elements of the measuring bridge rest on the measuring plate. For example, in the measuring state, the at least three support elements of the measuring bridge are in contact with the respective support points of the process chamber.

[0033] In the measuring state, the measuring bridge can be partially located outside an outer contour of the measuring plate in a top view. For example, in the measuring state, the support points of the process chamber are located outside, next to different outer sides of the measuring plate. In the measuring state, the measuring bridge can be arranged in the process chamber above a construction cylinder in which the measuring plate is movably mounted.

[0034] In its initial state, the measuring bridge can be positioned completely within the outer contour of the measuring plate in plan view. In its initial state, the measuring bridge can be arranged together with the measuring plate in a construction cylinder.

[0035] For example, the alignment of the measuring bridge relative to the measuring plate differs in plan view between the initial state and the measurement state. The measuring bridge can be rotated relative to the measuring plate (e.g., lifted from the measuring plate and rotated in plan view) to move it from the initial state to the measurement state.

[0036] The at least one drive coupling can have a predetermined position in plan view relative to the measuring plate, at least in the measuring state. It is conceivable that in the measuring state, the second surface point or at least one of the second surface points is centered in plan view relative to one of the at least one drive coupling. The second surface point or at least one of the second surface points can lie on a straight line between two of the at least one drive coupling. It is also conceivable that the second surface point or at least one of the second surface points lies on an angle bisector of connecting straight lines between three of the at least one drive coupling.

[0037] The first distance measured by a distance sensor can be set as zero for subsequent distance measurements by that distance sensor, so that the difference is measured directly when the distance measurement is performed by that distance sensor. In other words, the first distance can be used to zero that distance sensor.

[0038] The method may include arranging the measuring system in its initial state in a construction cylinder or the construction cylinder. For this purpose, the measuring bridge can be placed on the measuring plate arranged in the construction cylinder. The measuring plate can also rest on a construction plate provided in the construction cylinder or replace such a construction plate. The measuring system can be transported in the construction cylinder.

[0039] Furthermore, the method can comprise a (e.g. gas-tight) coupling of one or the

[0040] The coupling of the build cylinder with the measuring system arranged therein in the initial state to the additive manufacturing apparatus, in particular to its process chamber, can comprise this coupling. After this coupling, the interior of the build cylinder can be accessible from the process chamber through the coupling opening.

[0041] The method can comprise moving the measuring system, which is arranged in particular in a construction cylinder (e.g., coupled to the production apparatus), in its initial state (e.g., into a handling position). This movement can be accomplished by the drive system, so that the measuring plate with the measuring bridge resting thereon is moved, in particular in the construction cylinder in the direction of the process chamber (e.g., upwards). The measuring plate can be moved upwards far enough for a user to reach through the access opening and thus reach the measuring bridge with their hands. This movement can be carried out automatically, for example, by the control unit.

[0042] For example, the drive system is controlled to roughly position the measuring plate in a predetermined position during the measurement process. The predetermined position can be selected so that the upper side of the measuring plate is approximately in the same plane as the (e.g., expected) surface of a raw material layer that will later be provided on the build plate and solidified, or approximately in the same plane as the surface of the build plate used during the subsequent selective solidification.

[0043] The measurement of the at least one first distance according to step (b) can be performed before or after arranging the measuring system in the construction cylinder. The measurement of the at least one first distance according to step (b) can be performed before or after coupling the construction cylinder. The measurement of the at least one first distance according to step (b) can be performed before or after moving the measuring system into the handling position.

[0044] The method may further comprise manually arranging the measuring system in the measuring state, such that in the measuring state (i) the measuring plate is at least partially arranged in a construction cylinder or / and (ii) the measuring bridge is arranged substantially entirely outside the construction cylinder and / or substantially entirely within the process chamber. For example, the user (e.g., after moving the measuring system into the handling position) can reach through the access opening into the process chamber, lift the measuring bridge from the measuring plate, and reposition it to arrange the measuring system in the measuring state.

[0045] The method can comprise adjusting the position of the measuring plate relative to the process chamber based on the determined difference(s). In this case, the position of the measuring plate can be adjusted based on the determined difference(s) so that it corresponds exactly to the predetermined position. The translational and / or rotational change in position required for this can be determined mathematically (e.g. by the control unit) on the basis of the determined difference(s). In this case, previously known geometric information can also be used, which in particular indicates the positions of the drive couplings relative to the positioning platform and / or the measuring plate. In this way, in particular for each drive unit, a position change to be carried out can be determined, which is necessary to align the measuring plate exactly in the predetermined position. The drive system can then be controlled to adjust the position of the measuring plate accordingly.The measuring plate can then be moved translationally and / or rotationally relative to the process chamber.

[0046] If necessary, step (d) can be performed again after moving the measuring plate to adjust its position. The difference(s) determined in this process can then be used again to adjust the position of the measuring plate. In other words, the adjustment can comprise an iterative movement of the measuring plate relative to the process chamber based on differences recorded in iterative distance measurements, each carried out according to step (d). During the adjustment, the measuring plate can be moved (e.g., iteratively) until one or more or all of the difference(s) satisfy at least one predetermined criterion (e.g., until the differences are within a predetermined interval and / or are above a predetermined minimum value and / or are below a predetermined maximum value and / or deviate relative to one another by less than a predetermined deviation tolerance).

[0047] For example, during adjustment, the measuring plate is moved translationally up or down by equal position changes of the drive couplings. The measuring plate can also be rotated during adjustment by different position changes of the drive couplings (e.g., roll, pitch, and / or yaw). It is conceivable to first perform the translational movement of the measuring plate and then the rotational movement, or vice versa. However, it is also conceivable to perform both translation and rotation of the measuring plate simultaneously.

[0048] The method can comprise arranging a measuring device on the measuring plate using the positioning aid. The method can comprise performing at least one further measurement using the measuring plate, in particular using at least one measuring aid arranged on the measuring plate. As mentioned above, the measuring aid can comprise an optical marking, a positioning aid, an optical calibration pattern, a radiation source and / or a robot arm. For example, a measuring device which has been arranged on the measuring plate using the positioning aid is used for the further measurement. The at least one further measurement is carried out in particular after the measuring bridge has been removed from the process chamber and / or after the position of the measuring plate has been adjusted.

[0049] The method can comprise calibrating the manufacturing apparatus and / or components of the manufacturing apparatus (e.g., the solidification device, the drive system, and / or the control unit) based on the determined difference(s) and / or measured values ​​obtained during the further measurement(s). In particular, the drive system can be calibrated such that, after replacing the measuring plate with the build plate, it can reliably and precisely position the build plate in the predetermined position. In particular, incorrect positioning of the individual drive couplings relative to one another can be corrected. The calibration can also be used to adjust a property (e.g., impact position, power, and / or causticity) of the energy beam subsequently used for selective solidification.

[0050] The process may involve replacing the measurement plate with the build plate or removing the measurement plate located on the build plate. To do this, the user can again reach into the process chamber through the access opening.

[0051] The method may comprise additive manufacturing of a three-dimensional workpiece and / or selective solidification of a layer of raw material by the (e.g. calibrated) manufacturing apparatus.

[0052] A system may further be provided that includes the additive manufacturing apparatus and the measuring system. The system may further include the build plate and / or the build cylinder and / or the positioning platform. For example, both the build plate and the measuring plate are designed to be arranged on the positioning platform. The system may be designed so that the build plate can be exchanged for the measuring plate and vice versa.

[0053] Exemplary embodiments are explained below with reference to the figures, wherein the same reference numerals indicate the same functional and / or mechanical features and wherein:

[0054] Fig. 1 shows an additive manufacturing apparatus;

[0055] Fig. 2 shows a perspective view of a measuring system in the initial state;

[0056] Fig. 3 shows a top view of the measuring system in the initial state;

[0057] Fig. 4 shows a side view of the measuring system in the initial state;

[0058] Fig. 5 shows a perspective view of the measuring system in the measuring state;

[0059] Fig. 6 shows a plan view of the measuring system in the measuring state; and

[0060] Fig. 7 shows a perspective view of the measuring plate of the measuring system and two measuring devices.

[0061] Fig. 1 shows an additive manufacturing apparatus 2, comprising a process chamber 4 with an access opening 8 closed by a door 6 and with a frame 10 enclosing a coupling opening 12 in the lower floor 13 of the process chamber 4. The manufacturing apparatus 2 further comprises a drive system 14 with three drive units 16, each of which comprises a drive coupling 18.

[0062] In the state shown, additive manufacturing of a three-dimensional workpiece 19 is taking place. For this purpose, a build cylinder 20 is coupled to the coupling opening 12 of the process chamber 4. A positioning plate 22 is arranged in said cylinder, which is in contact with or supported by the drive couplings 18. A build plate is fastened to the positioning plate 22. This plate is initially connected to the process gas in the process chamber 4. After a layer of powdered raw material 23 has been applied to the build plate 22 positioned at the top in the build cylinder by a raw material application unit (not shown), this layer is selectively solidified by a laser beam 26 emitted by the solidification device 24 in the direction of the raw material. The build plate 22 is then moved downward by the drive system 14, and the next powder layer is applied.Thus, the manufacturing apparatus 2 can produce the three-dimensional valuable piece layer by layer. The manufacturing apparatus 2 further comprises a control unit 28, which is configured to control and calibrate the manufacturing apparatus 2, in particular the solidification device 24 and / or the drive system 14.

[0063] It is conceivable for the solidification device to comprise a beam splitting device configured to split an incident laser beam into a low-energy part and a high-energy part. The beam splitting device can be designed such that, depending on the control by the control unit 28, either the undivided laser beam or the low-energy and high-energy parts are guided toward the coupling opening 12. The two parts are directed by the solidification device to different impact points. The high-energy part can also be provided such that it impacts a larger area than would be necessary for selective solidification. This comparatively large focal point of the high-energy part can prevent damage to the parts irradiated by it (e.g., the measuring plate described below).For selective solidification, the undivided laser beam should be used. The low-energy portion of the laser beam is primarily used for the additional measurements described below to prevent damage to the measuring instruments used for this purpose and / or to eliminate the need for complex cooling of the measuring instruments. Furthermore, the beam splitting device can be positioned in the undivided beam path in such a way that the diameter of the undivided laser beam incident on the optical components in the beam splitting device, such as deflection mirrors, is particularly large relative to the diameter of the focal point. This prevents damage to the optical components.

[0064] 2, 3 and 4 show a measuring system 30 in its initial state, which is designed for measuring the production apparatus 2. The measuring system 30 comprises a measuring bridge 32 and a measuring plate 34. The measuring bridge 32 comprises a rigid frame 36, on which, in a plan view, three dial gauges 38 with respective probes 39 as distance measuring sensors are arranged, essentially evenly distributed. In a plan view, the frame 36 has an essentially triangular shape with internal struts 40. In a plan view, support elements 48 are provided at the three corners 42, 44, 46. As can be seen in the side view, these support elements 48 protrude the same distance downwards beyond the frame 36. In the initial state, the support elements 48 rest on the upper side of the measuring plate 34, so that the rest of the frame 36 is essentially freely suspended above the measuring plate 34.The support elements 48 lie in the same plane and in plan view on a first circle, the dial gauges 38 or their probes 39 lie in the same plane on a second circle with a smaller diameter, which also lies within the first circle.

[0065] It is provided that in the initial state of the measuring system 30, in a step (b), each dial gauge 38 measures a respective first distance between the measuring bridge 32 and a respective first surface point of the measuring plate 34. For example, the dial gauges are zeroed based on these first distances.

[0066] As can be seen in Figs. 2 to 4, the measuring bridge 32 is designed such that, in its initial state, it lies completely within an outer contour of the measuring plate 34 in a plan view. The measuring bridge 32 can thus be arranged together with the measuring plate 34 in one and the same build cylinder 20. For example, the build plate 24 can be replaced by the measuring plate 34 even before the build cylinder 20 is coupled to the production apparatus 2. This allows the measuring system 30 to be transported safely. After the build cylinder has been coupled to the production apparatus, the measuring plate 34 can be moved upwards by the drive system until the measuring bridge 32 can be reached by a user by reaching into it through the access opening 8 of the process chamber 4. It is understood that the measuring system 30 can alternatively also be introduced through the access opening 8 into an already coupled build cylinder 20.

[0067] It is intended that the measuring system 30 is manually put into a measuring state after step (b). To do so, the user can reach into the process chamber through the access opening 8, lift the measuring bridge 32 from the measuring plate, and rotate it so that the support elements 48 protrude beyond the outer contour of the measuring plate 34 in a plan view. The user can then place the measuring bridge 32 in such a way that the support elements 48 are in contact with the support points 50 provided for this purpose on the frame 10.

[0068] 5 and 6, the measuring system 30 is shown in the measuring state. Here, the measuring bridge 32 is arranged in a predetermined pose (e.g., at least one of a predetermined position and a predetermined orientation) relative to the process chamber 4 of the manufacturing apparatus, and the measuring plate 34 is movable relative to the process chamber 4 by the drive system 14. The predetermined pose is predetermined by the support elements 48 and the support points 50. The measuring bridge 32 lies essentially completely outside the construction cylinder 20, while the measuring plate 34 is movably arranged within the construction cylinder 20.

[0069] The measuring plate 34 can now be roughly positioned in a predetermined position, for example, such that its upper side lies in a plane that typically also includes the surface of the raw material to be solidified. This can be achieved by automatically moving the measuring plate 34 using the drive system 14, whereby reaching the predetermined position can be detected, for example, by sensors of the drive system 14.

[0070] It is intended that a new distance measurement is performed with the dial gauges 38 in the measuring state in order to determine a respective difference between the respective first distance and a respective second distance between the measuring bridge 32 and a respective second surface point of the measuring plate 34. If the dial gauges 38 were zeroed in the initial state based on the first distances, the distances can simply be measured in the measuring state to obtain these differences.

[0071] In an ideal scenario, the differences determined are equal, in particular equal to zero. However, it can happen that the measuring plate 34 is not positioned exactly in the predetermined position relative to the process chamber 4 during the measurement in the measuring state, for example due to positioning errors of the individual drive couplings 18 and / or measurement errors of the sensors of the drive system 14. The determined differences therefore provide an actual current position of the measuring plate 34, which usually differs from the predetermined position. Since the dial gauges 38 have previously measured the first distances in the initial state or have been zeroed, the determined differences are particularly reliable.

[0072] The differences can now be used to adjust the position of the measuring plate 34. For this purpose, the measuring plate 34 can be moved translationally and / or rotationally by individually controlling the individual drive units 16 by the control unit 28 to effect the same or different position changes of the drive couplings 18. The control unit can control the drive system 14 such that the measuring plate 34 is brought precisely into the predetermined position.

[0073] As indicated in Fig. 6, the drive couplings 18 can be arranged at different positions in the measuring state of the measuring system 30 in plan view, or can be located at different positions below the measuring plate 34. For example, each drive unit 16 is designed as a vertically arranged spindle drive having a drive coupling 18 at its upper end, which is connected to the positioning plate 22 at a predetermined position. The probe 39 of the dial gauge 38 shown on the left in Fig. 6 is centered in plan view with respect to a drive coupling 18. In contrast, the probes 39 of the two other dial gauges 38 each lie, in plan view, on an angle bisector 52 of connecting straight lines 54 between the three drive couplings 18.This embodiment is particularly advantageous because, knowing this arrangement of the dial gauges 38 relative to the drive couplings 18, the necessary position change of the individual drive couplings 18 can be determined particularly easily from the differences determined (e.g. by the control unit 28).

[0074] It is conceivable to perform the adjustment iteratively, i.e., to measure respective second distances several times and then readjust the position of the measuring plate 34 accordingly. It is also possible to first perform a translational correction of the position of the measuring plate 34 followed by a rotational correction, or vice versa. Of course, both are also possible simultaneously.

[0075] After adjusting the position of the measuring plate 34, further measurements can be carried out using the measuring plate 34, which is now arranged exactly in the predetermined position relative to the process chamber 4. For this purpose, the measuring plate 34 can be provided with measuring aids. In the example shown, the measuring plate 34 comprises optical markings 56 for preferred impact positions of various energy beams 26 emitted by the solidification device 24, such as the impact point of a setup laser, first positioning aids 60, each with a plurality of fastening means for determining predetermined measuring positions of a power meter for measuring the power of energy beams 26 emitted by the solidification device 24 (e.g.the low-energy part of the split laser beam), as well as second positioning aids 62 for establishing predetermined measuring positions of a caustic measuring device for measuring the causticity of energy beams 26 emitted by the solidification device 24 (e.g., the low-energy part of the split laser beam). The measuring plate 34 can be equipped or provided with further measuring aids, such as, for example, an optical calibration pattern for detection by an optical sensor of the additive manufacturing apparatus, a radiation source for detection by a sensor of the additive manufacturing apparatus, and / or a robot arm. The robot can, for example, movably carry a device designed to take measurements and / or perform maintenance on the additive manufacturing apparatus 2.

[0076] As shown in Fig. 7, one or more measuring devices 64 can be arranged on the measuring plate 34 using the positioning aids 60 after the measuring bridge 32 has been removed. Further measurements can then be performed using the measuring devices 64, with the exact position of the measuring devices 64 relative to the process chamber 4 being known by previously determining the differences and / or adjusting the position of the measuring plate 34. This increases the reliability and comparability of the subsequent measurements.

[0077] The differences and / or the measurement results obtained during the further measurements can be used to calibrate the manufacturing apparatus (e.g. by means of the control unit 28), in particular the drive system 14 and / or the solidification system 24. The differences can be used in particular (e.g. by the control unit 28) to position the build plate 24 used instead of the measuring plate 34 in the desired positions in the build cylinder during subsequent additive manufacturing.

[0078] It is understood that the present disclosure is not limited to the examples explained with reference to the figures. Some of the features explained therein are not absolutely necessary and can therefore be omitted. The features mentioned with reference to the figures can also be combined with one another or with other features. Further adaptations and advantages will become apparent to those skilled in the art from the present disclosure.

Claims

Patent claims 1. A method for measuring an additive manufacturing apparatus (2) which is designed to produce a three-dimensional workpiece (19) by selectively solidifying a raw material (23) layer by layer on a build plate (24) provided in a build cylinder (20) which is movable relative to a process chamber (4) of the manufacturing apparatus (2) by a drive system (14), the method comprising: (a) providing a measuring system (30) having a measuring plate (32) and a measuring bridge (34), wherein the measuring bridge (34) comprises at least one distance measuring sensor (38), and wherein the measuring system (30) is provided in an initial state such that the measuring bridge (32) rests on the measuring plate (34); (b) measuring a respective first distance between the measuring bridge (32) and a respective first surface point of the measuring plate (34) by each distance measuring sensor (38) in the initial state of the measuring system (30); (c) arranging the measuring system (30) in a measuring state such that the measuring bridge (32) is arranged in a predetermined pose relative to the process chamber (4) of the manufacturing apparatus (2) and the measuring plate (34) is movable relative to the process chamber (4) by the drive system (14); and (d) performing a distance measurement with each distance measuring sensor (38) to detect a respective difference between (i) the respective first distance and (ii) a respective second distance between the measuring bridge (32) and a respective second surface point of the measuring plate (34).

2. Method according to claim 1, wherein in the initial state at least three support elements (48) of the measuring bridge (32) rest on the measuring plate (34), and wherein in the measuring state the at least three support elements (48) of the measuring bridge (32) are in contact with respective support points (50) of the process chamber (4).

3. Method according to claim 1 or 2, wherein the measuring bridge (32) in the measuring state (i) in plan view lies partly outside an outer contour of the (34) measuring plate, or / and (ii) is arranged in the process chamber (4) above a construction cylinder (20) in which the measuring plate (34) is movably mounted.

4. Method according to one of claims 1 to 3, wherein the measuring bridge (32) in the initial state (i) in plan view lies completely within an outer contour of the measuring plate (34), or / and (ii) is arranged together with the measuring plate (34) in a construction cylinder (20).

5. Method according to one of claims 1 to 4, wherein the drive system (14) comprises at least one drive coupling (18), and wherein in the measuring state the second surface point in plan view (i) centered relative to one of the at least one drive coupling (18), or (ii) on a straight line (54) between two of the at least one drive coupling (18), or (iii) lies on an angle bisector (52) of connecting straight lines (54) between three of the at least one drive coupling (18).

6. The method according to any one of claims 1 to 5, further comprising at least one of the following steps: Arranging the measuring system (30) in the initial state in a construction cylinder (20); Coupling a construction cylinder (20) with a measuring system (30) arranged therein in the initial state to the additive manufacturing apparatus (2) so that the construction cylinder (20) is accessible from an interior of the process chamber (4); Moving the measuring system (30), which is arranged in particular in a construction cylinder (20), in the initial state, by the drive system (14), so that the measuring plate (34) with the measuring bridge (32) resting thereon is moved in the direction of the process chamber (4); manually arranging the measuring system (30) in the measuring state, so that (i) the measuring plate (34) is at least partially in a construction cylinder (20) is arranged, or / and (ii) the measuring bridge (32) is arranged substantially entirely outside the construction cylinder (20) and / or substantially entirely within the process chamber (4).

7. The method according to any one of claims 1 to 6, further comprising at least one of the following steps: Adjusting the position of the measuring plate (32) relative to the process chamber (4) based on the determined difference(s); Carrying out at least one further measurement using the measuring plate (32), in particular with at least one measuring device (64) arranged on the measuring plate (32).

8. The method according to claim 7, wherein adjusting the position of the measuring plate (34) comprises: Moving the measuring plate (34) such that the determined difference(s) meet a predetermined criterion; and / or translational and / or rotational movement of the measuring plate (34) relative to the process chamber (4); and / or iterative movement of the measuring plate (34) relative to the process chamber (4) based on differences that are recorded in iterative distance measurements carried out in each case according to step (d).

9. Measuring system (30) for an additive manufacturing apparatus (2) which is designed to produce a three-dimensional workpiece (19) by selectively solidifying a raw material (23) layer by layer on a building plate (24) provided in a building cylinder (20) which is movable relative to a process chamber (4) of the manufacturing apparatus (2) by a drive system (14), the measuring system (30) comprising: a measuring plate (34); and a measuring bridge (32), wherein the measuring bridge (32) comprises at least one distance measuring sensor (38), wherein the measuring system (30) is designed such that it can be provided in an initial state such that the measuring bridge (32) rests on the measuring plate (34), wherein each of the at least one distance measuring sensor (38) is designed to measure a respective first distance between the measuring bridge (32) and a respective first surface point of the measuring plate (34) in the initial state, wherein the measuring system (30) is designed such thatthat it can be arranged in a measuring state such that the measuring bridge (32) is arranged in a predetermined pose relative to the process chamber (4) of the manufacturing apparatus (2) and the measuring plate (34) is movable relative to the process chamber (4) by the drive system (14), wherein each distance measuring sensor (38) is arranged to carry out a distance measurement for detecting a respective difference between (i) the respective first distance and (ii) a respective second distance between the, Measuring bridge (32) and a respective second surface point of the measuring plate (34).

10. The measuring system (30) of claim 9, further adapted for use as the measuring system (30) in the method of any one of claims 1 to 8.

11. Measuring system (30) according to claim 9 or 10, wherein the measuring bridge (32) comprises at least three support elements (48) which are designed to rest on the measuring plate (32) in the initial state and to come into contact with respective support points (50) of the process chamber (4) in the measuring state, wherein, optionally, {i} the at least one distance measuring sensor (38) is located in plan view within a circumference defined by the support elements (48), and / or {ii} the measuring bridge (32) comprises a frame (36), wherein {a} the support elements (48) are arranged on the outside in plan view, in particular at respective outer corners (42, 44, 46) of the polygonal frame (36) in plan view, or / and {b} the support elements (48) project downwards beyond the frame (36) in side view, so that the frame (36) is held in the initial state by the support elements (48) floating above the measuring plate (34).

12. The measuring system (30) according to any one of claims 9 to 11, wherein the measuring plate (34) is provided with measuring aids (56; 58; 60) designed for subsequent measurements, wherein the measuring aids (56; 58; 60) in particular comprise at least one of the following measuring aids: an optical marking (56; 58) for a preferred impact position of an energy beam (26) of the additive manufacturing apparatus (2); a positioning aid (60) for establishing a predetermined measuring position of a measuring means, in particular a measuring device, on the measuring plate (34); an optical calibration pattern for detection by means of an optical sensor of the additive manufacturing apparatus (2); a radiation source for detection by means of a sensor of the additive manufacturing apparatus (2); a robot arm movably supporting a device designed to perform measurements and / or maintenance of the additive manufacturing apparatus (2).

13. Additive manufacturing apparatus (2) comprising a process chamber (4) and a Drive system (14), and configured to produce a three-dimensional workpiece (19) by selectively solidifying a raw material (23) layer by layer on a build plate (24) provided in a build cylinder (20) which is movable relative to the process chamber (4) of the manufacturing apparatus (2) by the drive system (14), wherein the manufacturing apparatus (2) is or can be equipped with the measuring system (30) according to one of claims 9 to 12 and in particular comprises a control unit (28) which is designed to calibrate and / or control the additive manufacturing apparatus (2) based on the respective difference and / or at least one measurement result which was / were obtained according to the method according to one of claims 1 to 8 using the manufacturing apparatus (2) and the measuring system (30).

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