Device for powder bed-based additive manufacturing of metallic components

Abstract

Device (2) for powder bed-based additive manufacturing of metallic components, with a material reservoir (4) for receiving a powdered metal material that can be selectively melted by means of a melting device, wherein the material forms a powder bed (6) in the material reservoir, with at least one skimming element (32) for shaping the surface of the powder bed (6), wherein the skimming element (32) is designed in the manner of a doctor blade and defines a skimming edge (34), with a movable carrier (36) on which the or each squeegeeing element (32) is arranged, wherein the carrier (36) is designed such that the squeegeeing edge (34) is movable for squeegeeing the surface of the powder bed relative to the same in a squeegee plane (xy-plane, Fig. 3), wherein the or each puller element (32) is adjustably arranged on the carrier (36) along an adjustment axis (z-axis, 38) perpendicular to the puller plane for setting a puller position of the puller edge (34), wherein the puller position relative to the carrier (36) is at least phasewise fixed or variable around a zero position according to a high-frequency oscillation during the puller process and wherein a drive unit (40) is assigned to the adjusting axis (38), characterized by that the peeling edge (34) is formed by a plurality of peeling elements (44-50) arranged adjacent to one another in the longitudinal direction of the peeling edge (34), that at least two puller elements (44-50) are each assigned a separate, independently controllable drive unit, wherein the device (2) has a control device (12) for controlling the drive devices, wherein the device (2) comprises an optical measuring device (18) for three-dimensional measurement of the topography of the surface of the powder bed (6), wherein the measuring device (18) is in such a way as to be in signal transmission connection with the control device (12) for controlling the drive device (40) or the drive devices that the drive device (40) or the drive devices can be controlled depending on the measurement result of the measuring device (18), and wherein the control device (12) is programmed for automatic control of the drive device (40) or drive devices depending on the measurement result of the measuring device (18) such that a desired topography of the surface of the powder bed (6) is automatically formed.

Description

[0001] The invention relates to a device for powder bed-based additive manufacturing of metallic components.

[0002] Such devices, also known as 3D printers, are widely known and used to build three-dimensional workpieces. The workpieces are built layer by layer under computer control using at least one powdered metallic material. Physical melting processes take place to create the three-dimensional structure. These devices are particularly suitable for creating complex geometric structures.

[0003] The known devices have a material reservoir for receiving a melt of a fusible powdered metal material, wherein the material in the material reservoir forms a powder bed and is selectively melted by means of a melting device according to the cross-section of the component to be generated.

[0004] Furthermore, the known devices have a squeegee for shaping the surface of the powder bed, wherein the squeegee is designed in the manner of a doctor blade and defines a squeegee edge. The squeegee is arranged on a movable carrier, wherein the carrier is designed such that the squeegee edge is movable relative to the surface of the powder bed in a squeegee plane for squeegeeing it.

[0005] During the manufacturing of a component, the surface of the powder bed is smoothed by the finishing element before the melting process. Subsequently, the powdered metal material is selectively melted by the melting device, which is, for example, a laser, according to the cross-section of the component to be manufactured.

[0006] Following a melting process, a new layer of powder is applied to prepare for the next melting process. This is achieved by adding more powder to the material reservoir and distributing and smoothing it along the surface of the powder bed using the screeding element. To ensure that the surface of the powder bed remains in the same plane throughout the manufacturing process, and that the selective melting process also always occurs in the same plane, the component and the material reservoir are mounted on a fixture that is movable perpendicular to the surface of the powder bed. After each melting process, the fixture, with the component and the powder bed, is lowered by an amount corresponding to the thickness of the metal layer generated in that melting process.

[0007] DE 10 2004 022 387 A1 relates to devices for the rapid production of bodies, each with at least one build space comprising a carrier for bodies, a storage space for particles, a transport device for particles from the storage space to the build space and a laser, wherein laser beams can be guided over the cross-sectional area of ​​the build space and, when laser beams hit a layer of particles, both particles sinter and / or fuse with each other and with at least one layer of sintered and / or fused particles arranged below, and uses of such devices.

[0008] DE 10 2014 010 951 A1 relates to a method for producing three-dimensional components from individual layers of flowable building material, such as particle material or viscous pastes, which are fed layer by layer to a build area by a recoater. The invention provides that the recoater produces the layer by pushing the building material through a gap with one or more slides. By controlling the movement of the slide(s), the material flow can be selectively controlled so that the material is applied only to the required areas. Likewise, the component density can be selectively controlled by varying the contact pressure of the slide(s).DE 10 2015 224 395 A1 relates to a device and a method for manufacturing components in a layer-by-layer process with a container which defines a build space in which a powder bed can be produced layer by layer from a powdered starting material, an exposure device for generating a light beam with which areas of a layer of powdered starting material can be solidified, a coating device for producing a top layer of powdered starting material on the underlying powder bed characterized by a detection device for detecting surface irregularities on the powder bed.

[0009] EP 1 234 625 A1 relates to the production of a shaped body, which includes the selective application of a powder layer to areas of the surface of the shaped body using an application device and the fixing of the applied powder layer to an underlying layer using a focused laser beam. A separate claim is also included for a device for producing a shaped body by selective laser welding.

[0010] The invention is based on the objective of improving the function of a device of the type mentioned in the preamble of claim 1.

[0011] This problem is solved by the invention specified in claim 1.

[0012] The invention provides that the peeling edge is formed by a plurality of peeling elements arranged adjacent to one another in the longitudinal direction of the peeling edge, that at least two peeling elements are assigned a separate, independently controllable drive device, wherein the device has a control device for controlling the drive devices, wherein the device has an optical measuring device for three-dimensional measurement of the topography of the surface of the powder bed, wherein the measuring device is in signal transmission connection with the control device for controlling the drive device(s) such that the drive device(s) can be controlled or are controlled depending on the measurement result of the measuring device, and wherein the control device is for automatic control of the drive device(s).The drive devices are programmed depending on the measurement result of the measuring device, such that a desired topography of the surface of the powder bed is automatically formed.

[0013] The basic idea of ​​the invention is to design the device in such a way that the surface of the powder bed can be shaped according to a desired topography, in order to selectively influence process parameters of the manufacturing process. This basic idea is realized according to the invention by making the pulling element(s) movable relative to the carrier perpendicular to the pulling plane.

[0014] By adjusting the position of the screed edge along the adjustment axis, the surface of the powder bed can be shaped according to a desired topography with each layer application of powder.

[0015] Since the adjustment along the adjustment axis is carried out by means of a drive device, automatic adjustment of the puller element or elements is possible, so that the operation of a device according to the invention can be further automated.

[0016] According to the invention, it is not only possible to change the thickness of the applied powder layer or to modulate it in the screed direction. It is also possible to adjust the thickness of the powder layer longitudinally along the screed edge, i.e., perpendicular to the screed direction, according to a desired profile. This allows the topography of the powder bed surface to be adapted within wide limits to meet specific requirements. The more screed elements are provided, the finer the shaping or structuring of the powder layer surface can be. The screed elements, arranged side by side and adjacent to one another, together form the screed edge, which is structured according to the respective screed position (height) of each individual screed element, so that during the screeding process, a surface of the powder bed is formed that corresponds to the structure of the screed edge.It is also possible to adjust the screeding elements relative to each other during the screeding process, enabling a customized powder application at any point on the powder bed. This allows the topography of the powder bed surface to be finely structured according to specific requirements, with the fine structuring generally improving as the number of screeding elements increases.

[0017] The respective drive unit can be any type of motor drive unit. For example, at least one drive unit can be designed as a piezo actuator or motor.

[0018] By appropriately programming the control unit, the topography of the surface can be influenced during the peeling process according to the respective requirements, and the surface of the powder bed can thus be shaped accordingly.

[0019] According to the invention, the powder surface can first be measured using the measuring device and then shaped or structured according to the respective requirements during the peeling process. This allows the surface of the powder bed to be shaped with a high degree of certainty at any point according to the specific requirements. Because the topography of the powder surface can not only be specifically influenced but also measured, the process reliability of the device is significantly increased. Before applying a new powder layer, the measuring device can determine at which point on the powder bed which specific powder application is required to achieve the desired topography. It is also possible to check whether the desired topography of the powder surface has been achieved after applying a powder layer using the measuring device.

[0020] Due to the shaping of the surface of the powder bed made possible by the invention, the design scope of the process parameters for the melting process is expanded.

[0021] Another advantage of the invention is that the initial setup of the device, as well as any subsequent setup, for example after damage, is simplified.

[0022] As a result, the productivity of the device is significantly increased by the invention.

[0023] The position of the squeegee relative to the carrier can be fixed, at least in phases, during the squeegeeing process. This means that the squeegee position can remain unchanged throughout the entire process, resulting in a powder layer of essentially constant thickness. However, it is also possible to change the squeegee position relative to the carrier in phases during the squeegeeing process, so that the thickness of the applied powder layer is modulated according to the change in the squeegee position.

[0024] However, it is also possible to change the squeegee element in the dispensing position around a zero position by means of a high-frequency vibration, thus setting the squeegee element into vibration. With a suitable design, the zero position defines the actual thickness of the powder layer, while the high-frequency vibration improves the flowability of the powder.

[0025] The functionality of a device according to the invention is already improved compared to the prior art in that the or each pulling element is adjustable relative to the carrier along an adjustment axis perpendicular to the pulling plane, as provided by the invention.

[0026] To achieve a simple and cost-effective design of the device, a further development of the invention provides that at least one drive unit is designed as a piezoelectric actuator. Piezoelectric actuators are readily available as relatively simple and inexpensive standard components. In particular, actuator modules in the form of actuator strips are known and commercially available, comprising more than 80 actuators arranged closely together.

[0027] Another advantageous embodiment of the invention provides that the puller element or elements are arranged on a puller element module.

[0028] A further development of the aforementioned embodiment provides that the pull-off element module, or a part thereof, can be detachably connected to or attached to the carrier. This simplifies the replacement of the pull-off element(s), for example, as part of routine maintenance or replacement after damage.

[0029] An advantageous further development of the aforementioned embodiments provides that the peeling element module comprises a passive peeling edge module, on which a plurality of peeling edge elements, movable independently of one another along the adjustment axis, are arranged side by side, and an active actuator module, on which a plurality of independently controllable actuators are arranged, each of which is assigned to one of the peeling edge elements for adjusting it along the adjustment axis. Such a modular design allows, for example, and in particular, the peeling edge module to be replaced separately, while the actuator module remains on the carrier. In this way, replacing the peeling edge module, for example after wear or damage, is made particularly easy.

[0030] In embodiments with the peel-off edge module, the module can be designed in any suitable manner according to the respective requirements. To make the peel-off edge module particularly easy and cost-effective to manufacture, an advantageous further development provides that the peel-off edge module comprises a strip of sheet metal or another elastically deformable material, which is angled and has a first leg that is subdivided into tongue-shaped peel-off edge segments by incisions spaced apart from each other along the longitudinal direction of the peel-off edge, the other leg of which can be connected to or is connected to the support or to a component connected to the support, wherein each of the peel-off edge segments is movable along the adjustment axis by an associated actuator.

[0031] To improve the flowability of the powder during the peeling process, another advantageous embodiment of the invention provides a vibration device for subjecting the peeling element or elements to high-frequency vibrations.

[0032] Another advantageous embodiment of the invention provides that the carrier is designed and configured for translational movement along a linear pull-off axis.

[0033] Movement of the puller element along the adjustment axis can be achieved by moving the puller element translationally or linearly along the adjustment axis, for example by means of a linear drive. In this sense, an advantageous embodiment of the invention provides that at least one puller element is translationally movable for adjustment along the adjustment axis.

[0034] However, movement of the puller element along the adjustment axis can also be achieved by rotating the puller element about an (actual or virtual) axis of rotation that runs transversely to the adjustment axis. In this sense, another advantageous embodiment of the invention provides that at least one puller element is rotatable for adjustment along the adjustment axis about an axis of rotation. For example, an actuator can be assigned to each of the longitudinally located ends of an elongated puller element, so that the puller element is translationally movable by uniform actuation of both actuators and rotatable or tiltable by differential actuation of the actuators.

[0035] The invention is explained in more detail below with reference to the accompanying, highly schematic drawing and exemplary embodiments. The subject matter and disclosure of the application also include sub-combinations of the claims in which at least one feature of the respective claim is omitted or replaced by another feature.

[0036] It is evident to a person skilled in the art that the individual features of the embodiments further develop each embodiment independently, i.e., irrespective of the other features of the embodiment. The disclosure scope of the application also includes combinations of the features of the embodiments with one another, so that each feature of an embodiment can be transferred to the other embodiments independently of the other features of that embodiment.

[0037] It shows: Fig. 1 in a highly schematic perspective view an embodiment of a device according to the invention for powder bed-based additive manufacturing of metallic components, Fig. 2 another schematic perspective view of the device according to Fig. 1, Fig. 3 in a perspective schematic sketch a peeling element of a first embodiment of a device according to the invention, Fig. 4 in the same representation as Fig. 3 a second embodiment, Fig. 5 to illustrate the functionality of the exemplary embodiment according to Fig. 4 another schematic diagram, Fig. 6 in a highly schematic schematic diagram an embodiment of a peel-off edge module and Fig. 7 a block diagram of a device according to the invention.

[0038] With reference to Fig. 1 to Fig. Section 6 below describes the invention in more detail with reference to exemplary embodiments.

[0039] In the figures of the drawing, identical or corresponding components are provided with the same reference symbols.

[0040] In Fig. Figure 1 is a highly schematic embodiment of an inventive device 2 for powder bed-based additive manufacturing of metallic components, which has a material reservoir 4 shown only schematically for receiving a metallic powder material that can be melted by means of a melting device and which forms a powder bed 6 in the material reservoir 4.

[0041] In the illustrated embodiment, the melting device has a laser 8 whose laser beam 10 is movable and variable in intensity, controlled by a control unit 12, for the selective melting of the powdered metal material along the surface of the powder bed 6. Arrows 14 and 16 in the drawing indicate that the laser beam 10 can be changed two-dimensionally in its position relative to the powder bed 6, so that any desired position within the powder bed 6 can be reached.

[0042] To smooth the surface of the powder bed 6, a device for shaping, in particular smoothing, the surface of the powder bed 6 is provided, which, however, for reasons of simplification, is shown in Fig. 1 is only schematically indicated and is designated with the reference symbol 17.

[0043] Devices and methods for powder bed-based additive manufacturing of metallic components are, moreover, generally known to those skilled in the art and are therefore not explained in more detail here, unless their details are specific to the invention.

[0044] According to the invention, the illustrated embodiment provides optical means for determining the topography of the surface of the powder bed 6. In the illustrated embodiment, these optical means comprise a 3D-measuring optical measuring device 18 with an optical sensor, which in the illustrated embodiment is designed as a line sensor and is arranged on a sensor carrier 20 that is movable relative to the powder bed 6 along a linear axis, as indicated by arrow 22 in the drawing. The line sensor extends over the full width of the powder bed 6, so that by linearly moving the sensor in the direction of arrow 22, every point on the surface of the powder bed 6 can be scanned.

[0045] The line sensor has a line-shaped arrangement of sensor elements and an integrated lighting device for illuminating the surface of the powder bed 6 in the area detected by the line sensor. The line sensor and the lighting device are integrated to form a sensor / lighting unit.

[0046] The output signals of the line sensor are fed to an evaluation unit 24.

[0047] By means of the line-like arrangement of sensor elements of the line sensor, each point on the surface of the powder bed 6 can be viewed from different angles, as indicated in the drawing by two dashed lines 28, 30 for a point 26. In the illustrated embodiment, the evaluation unit 24 is designed and configured for evaluating the output signals of the line sensor using the stereo triangulation method. The operation of the stereo triangulation method is generally known and is therefore not explained in detail here.

[0048] The sensor / illumination unit can, in principle, be constructed in a manner similar to that used in flatbed scanners. However, unlike flatbed scanners, the evaluation unit 24 is designed and programmed to evaluate the output signals of the line sensor using stereo triangulation. This allows the output signals of the line sensor to generate an image of the scanned surfaces of the powder bed 6, as is known from flatbed scanners. Furthermore, the evaluation unit 24 uses stereo triangulation to derive surface depth information from the output signals of the line sensor, thus reconstructing the three-dimensional topography of the powder bed 6 surface.

[0049] The functioning of the device 2 according to the invention is as follows: In a powder bed-based additive manufacturing process for metallic components, the surface of the powder bed 6 is smoothed by a device 17 prior to a melting process. After smoothing, the surface of the powder bed 6 is scanned by the sensor / illumination unit by moving the sensor carrier 20 along the linear axis 22, with the output signals of the line sensor being transmitted to the evaluation unit 24. In the evaluation unit 24, the output signals of the line sensor are evaluated using the stereo triangulation method, whereby the three-dimensional topography of the surface of the powder bed 6 is reconstructed based on the output signals of the line sensor. Based on the reconstruction, it can then be determined whether the surface of the powder bed 6 is sufficiently smoothed for the subsequent melting process.If sufficient smoothing is detected, the control unit 12 can activate the laser 8 to perform the next melting process. In the case of insufficient smoothing, the control unit 12 can activate the device 17 to smooth the surface of the powder bed 6 again, after which the surface of the powder bed 6 is scanned again using the line sensor. If sufficient smoothing is then present, the melting process can be carried out. Otherwise, the laser 8 may not be activated and an error message may be issued.

[0050] If desired or necessary, the output signals that the line sensor outputs during scanning can also be combined to form an optical image of the surface of the powder bed 6.

[0051] According to the invention, it is also possible to store the topographies of the surface of the powder bed 6 determined in the evaluation device 24 in order to have indications of which layer of the workpiece may contain a workpiece defect when checking the manufactured workpiece at a later time.

[0052] In order to be able to measure not only the surface of the powder bed 6, but also the component during its manufacture, the evaluation device 24 is designed and set up for testing and / or measuring a cross-sectional area of ​​the component to be manufactured, formed by melting the powder, using the output signals of the optical sensor.

[0053] Fig. Figure 2 shows a further schematic perspective view of the device 2. The device 17 for shaping the surface of the powder bed 6 has a squeegee element 32, which is designed in the manner of a squeegee and has a squeegee edge 34 (see Figure 2). Fig. 3) defined. The squeegee 32 is arranged on a movable support 36, which is only schematically indicated in the drawing. The support 36 is designed such that the squeegee edge 34 for squeegeeing the surface of the powder bed 6 is located in a squeegee plane (xy-plane) relative to the surface of the powder bed 6. Fig. 3) is movable. In the illustrated embodiment, the carrier 36 is designed and configured for translational movement along a linear pull-off axis, wherein the linear pull-off axis is in Fig. 3 corresponds to the x-axis. The resulting subtraction direction is in Fig. 3 marked by an arrow 37.

[0054] Other kinematics of the movement of the carrier 26 for removing the surface of the powder bed 6 by means of the removal element 32, for example a windshield wiper-like movement, are also possible according to the invention.

[0055] In Fig. 3 corresponds to the peeling plane of the xy-plane. According to the invention, the peeling element 32 is adjustably arranged on the carrier 36 along an adjustment axis perpendicular to the peeling plane relative to the carrier 36 in order to set a peeling position of the peeling edge 34. Fig. 3 corresponds to the adjustment axis of the z-axis, as in Fig. 3 arranged by a double arrow 38. A drive unit 40 is assigned to the adjustment axis, which is located in Fig. 3 is shown purely schematically.

[0056] According to the invention, the position of the squeegee 32, and thus the squeegee edge 34, can be adjusted along the adjustment axis (z-axis) by means of the drive unit 40. It is evident that by appropriately adjusting the squeegee 32 relative to the surface of the powder bed 6, the thickness of the powder layer to be applied can be set. Thus, according to the invention, the surface of the powder bed 6 can be shaped according to a desired topography.

[0057] During operation of the device 2, after a melting process has been carried out to form a layer of the workpiece to be generated, a new layer of powder is applied. To ensure that a subsequent melting process is carried out in the same plane as the previous melting process, a support (base plate) on which the material reservoir with the powder bed 6 and the workpiece to be generated are arranged is first lowered by a height corresponding to the thickness of the layer of the component generated in the previous melting process.

[0058] Subsequently, further powdered metal material, hereinafter also referred to simply as powder, is introduced into the material reservoir. In the illustrated embodiment, the x-axis corresponds to the linear axis along which the puller element 32 moves during a pull-off process (pulling axis). If the puller element 32 is located, for example, in the Fig. In the position shown in Figure 2, the powder is introduced into the material reservoir in the pulling direction in front of the pulling element 32, so that the introduced powder is in the material reservoir during the pulling process, i.e., during a movement of the pulling element 32 along the x-axis. Fig. 2 or Fig. 3 from left to right, in the form of a "bow wave" in front of the pull-off element 32, as in Fig. 3 is indicated at reference numeral 40. By setting a corresponding peeling position of the peeling edge 34 along the adjustment axis (z-axis), the layer thickness of a powder layer applied during this peeling process can be adjusted.

[0059] The peeling position can be fixed relative to the carrier 36 during the peeling process, so that when the peeling edge 34 moves over the entire surface of the powder bed 6, a powder layer of uniform thickness (corresponding to the peeling position of the peeling edge) is applied.

[0060] However, it is also possible to change the peeling position during the peeling process, so that the thickness of the powder layer varies along the peeling axis (x-axis) during the peeling process, i.e., along the surface of the powder bed 6. The peeling position is adjusted by the control unit 12 by correspondingly controlling the drive unit 40 (see figure). Fig. 3 and Fig. 7).

[0061] To improve the flowability of the powder, it is also possible to move the screed edge 34 around a zero position during the screeding process according to a high-frequency vibration. The zero position then defines the screeding position, in other words, the width of the gap between the screed edge 34 and the surface of the powder bed 6.

[0062] The in Fig. The embodiment shown in section 3 thus enables the topography of the surface of the powder bed 6 to be influenced.

[0063] After a peeling process has been carried out, the measuring device 18 can be used to check whether the surface of the powder bed has the desired topography. If the peeling process has resulted in the desired topography, for example a powder layer that is flat along the entire surface of the powder bed 6, the control device 12 can, after the measurement, activate the laser 8 to carry out the next melting process.

[0064] The corresponding processes run fully automatically until the component is generated in the desired manner.

[0065] Fig. Figure 4 shows a further embodiment, which differs from the embodiment according to Fig. 3 differs in that the peeling edge 34 is formed by at least two peeling elements arranged next to each other and adjacent to each other in the longitudinal direction of the peeling edge 34.

[0066] In the illustrated embodiment, four screeding elements 44, 46, 48, 50 are shown purely as examples and symbols to clarify the functional principle. It is evident that, depending on the specific requirements, a multitude of screeding elements arranged side by side and adjacent to one another along the longitudinal direction of the screeding edge 34 is possible and desirable in order to achieve the finest possible spatial resolution of the topography of the powder bed surface 6.

[0067] Each of the puller elements 44 to 50 is assigned a separate, independently controllable drive unit, the control of the drive units being carried out by the control unit 12 (see Fig. 7) is carried out. In the illustrated embodiment, each of the drive devices is designed by a piezo actuator.

[0068] While in the embodiment according to Fig. 3. The embodiment according to enables a spatially resolved structuring of the surface of the powder bed 6 along the pull-off axis (z-axis). Fig. 4. Furthermore, a spatially resolved structuring of the surface of the powder bed 6 in the longitudinal direction of the screed edge 34 and thus transversely to the screed axis, i.e., along the y-axis. The spatial resolution of the structuring is higher the more screed elements are provided. A high resolution can therefore be achieved in principle by using a corresponding number of screed elements 44 to 50.

[0069] By appropriately controlling the drive devices assigned to the pulling elements 44-50, any desired topography of the surface of the powder bed 6 can be set within the given spatial resolution.

[0070] If the screeding edge 34 is inclined relative to a base plate on which the powder bed 6 rests, a different height adjustment of the screeding elements 44-50 along the y-axis can be used to compensate for the inclination of the screeding edge 34 relative to the base plate, as shown in Fig. 5 is indicated by reference numeral 51.

[0071] To structure the surface of the powder bed 6 according to a desired topography, the topography of the powder surface is first measured three-dimensionally using the measuring device 18. The measuring device 18 is connected to the control unit 12 for controlling the drive units in such a way that the drive units are controlled depending on the measurement result of the measuring device 18. The control unit 12 is programmed for automatic control of the drive units depending on the measurement result of the measuring device, such that a desired topography of the surface of the powder bed 6 is automatically formed during the peeling process.

[0072] If a uniform layer thickness is desired over the entire extent of the surface of the powder bed 6 in the x-direction, the position of the peeling elements 44-50 (peeling position) set by the control device 12 is maintained during the peeling process.

[0073] If, on the other hand, a topography varying in the x-direction is desired or required, the control device 12 controls the drive devices of the puller elements 44 to 50 accordingly during the puller process.

[0074] In this way, virtually any surface structuring of the powder bed 6 is possible within the limits of the achievable spatial resolution and the properties of the powder, thus expanding the design scope for the process parameters of the powder bed-based additive manufacturing process. In particular, automatic adjustment of the peening edge 34 to the base plate on which the powder bed 6 rests is enabled with regard to its angular orientation.

[0075] In particular, both initial setup and resetting of the squeegee edge 34 after damage are possible automatically. Furthermore, powder consumption can be minimized due to the design according to the invention.

[0076] Overall, this results in higher productivity for device 2.

[0077] The pull-off elements 44-50 can be arranged on a pull-off element module, wherein the pull-off element module or a part of the pull-off element module can be detachably connected or joined to the carrier 36.

[0078] The peeling element module can preferably have a passive peeling edge module, on which a plurality of peeling edge elements are arranged side by side and which are movable independently of the direction along the adjustment axis, and an active actuator module, on which a plurality of independently controllable actuators are arranged as drive devices, each of which is assigned to one of the peeling edge elements for adjusting it along the adjustment axis.

[0079] In Fig. Figure 6 shows an exemplary embodiment of a corresponding peeling edge module 52, which has a strip 54 made of sheet metal, which is angled and has a first leg 56, which is divided into tongue-like peeling edge segments by incisions spaced apart from each other along the longitudinal direction of the peeling edge 34. Fig. 6 are examples of two incisions designated with reference numbers 58, 60 and two peeling edge segments designated with reference numbers 62, 64.

[0080] The second leg 66 of the strip 54 is arranged on the support 36. The mobility of the sheet metal edges, which function as pull-off edge segments 62, 64, is achieved by elastic bending of the leg 66 clamped at 68.

[0081] The thickness of the strip 54 and the width of the incisions 58, 60, which can be produced by cutting with an ultrashort pulse laser or by etching, are coordinated such that the individual peeling edge segments 62, 64 move essentially parallel to each other in the z-direction in their lower region, at least for the relatively small deflections compared to the cantilever length. This ensures that as little powder as possible from the "bow wave" can pass through the gaps between the peeling edge segments 62, 64.

[0082] It is desirable that the powder passes through the screed edge module 52 as far as possible exclusively below the parts of the screed edge segments 62 that define the screed edge 34. If required according to the specific requirements, elastic sealing material can be used, as indicated in section 72. The height expansion and viscosity of the sealing material are adjusted so that, on the one hand, relatively free movement of the individual screed edge segments 62, 64 in the z-direction remains possible. On the other hand, the sealing material 72 should prevent the passage of powder between the screed edge segments 62, 64 as much as possible. As a side effect, the elastic sealing material 72 can also act as a vibration damper, which facilitates rapid height adjustment of the screed edge segments 62, 64.

[0083] The pulling direction is in Fig. 6 marked by an arrow 74.

[0084] In order to actuate the peeling edge segments 62, 64 and the further peeling edge segments independently of one another, each peeling edge segment is assigned an independently actuating drive device, which in the illustrated embodiment is formed by a piezo actuator. A piezo actuator assigned to peeling edge segment 62 is in Fig. 6 is indicated purely schematically and labelled with reference numeral 76. An impact axis of actuator 76 is shown in Fig. 5 is marked with a dashed line 78. For illustrative purposes, in Fig. Figure 5 shows the piezo actuator 76 and the associated pull-off edge segment 62 relatively far apart. In practice, the piezo actuator rests against the pull-off edge segment 62 for a short actuation path, so that when the piezo actuator is actuated along the adjustment axis, the segment is deflected, as shown in Figure 5. Fig. 6 indicated by a double arrow 80.

[0085] Typical dimensions for implementing the peeling edge module 52 are in Fig. 6 in millimeters (reference numeral 11 corresponds to 11 mm; analogously, for reference numerals 12, 13, 14 and 15, the lengths 12 mm, 13 mm, 14 mm and 15 mm apply). Fig. 6).

[0086] Piezoelectric elements in stacked or bimorph configurations can be used as piezoelectric actuators. These actuators offer advantages for the intended application because they can be modulated quickly and require very little additional energy to maintain a specific position. Corresponding actuator modules are also known and established in other products. Actuator strips with more than 80 closely spaced actuators are commercially available.

[0087] In its mounting position on the peel-off edge module 52, the actuator module is preferably clamped to the passive peel-off edge module 52 with a certain mechanical preload along the adjustment axis (z-axis). The preload of the individual actuators shifts the working range of the piezoelectrics from a symmetrical position in the tensile-compression range to a position closer to the compression range.

[0088] Due to component tolerances in the passive or active module, the basic deflection of the peeling edge segments 62, 64 will typically differ. In conjunction with a measuring 3D topography system (measuring device 18), an initial test peel can be performed in the powder bed. The resulting difference in the height of the powder bed strips is measured using the measuring device 18 and compensated for as an offset during subsequent regular operation. By repeating the process for one or more other deflections of the piezoelectric elements, the sensitivity factor (in deflection per applied voltage) can be determined as a nonlinearity for each peeling edge segment 62, 64, if required, and then compensated.

[0089] A further development of the device 2, which has an independent inventive significance both in combination with the puller element movable along an adjustment axis by means of a drive device, but also independently thereof, is a device 82 (cf. Fig.6) for removing material from the powder bed 6 and / or relocating material within the powder bed 6. The device 82 is controlled by the control unit 12 and, in this embodiment, is designed as a suction device functioning like a vacuum cleaner. The device 82 serves to selectively remove material from the powder bed. If, during the optical measurement of the powder bed using the optical measuring device 18, it is determined that, for example, melt residues from a previous melting process are present in the powder bed, these melt residues can be selectively removed from the powder bed using the device 82. This prevents the melt residues from impairing the subsequent additive manufacturing process and, in particular, from causing defects in the component being manufactured.

[0090] The device 82 can be arranged together with the puller element 32 on the movable support 36.

[0091] In order to be able to reach every point on the surface of the powder bed 6 during the peeling process, it is advantageous if the device 82 is not only movable (preferably together with the peeling element 82) in the peeling direction (x-direction), but also transversely to the peeling direction, i.e. in the y-direction.

[0092] For the sake of a simple design, it is advantageous if the device 82 is arranged together with the pull-off element 32 on the movable carrier 36. However, it is also possible to arrange the device 82 on a separate carrier, by means of which the device 82 is movable along the surface of the powder bed 6, i.e. at least in the x direction, but advantageously in both the x and y directions.

[0093] According to the invention, the device 82 can also serve to selectively remove powder from the powder bed.

[0094] Another further development of the device 2, which has an independent inventive significance in combination with the aforementioned embodiments, but also independently thereof, provides a device 84 for selectively introducing powder material into the powder bed, which can be controlled by the control device 12.

[0095] As described above, the application of a new powder layer is carried out such that the powder is introduced in the peeling direction in front of the peeling edge 34 and distributed as a uniform layer across the surface of the powder bed during the peeling process. By means of the device 84, which is preferably movable two-dimensionally along the surface of the powder bed, i.e., in the x and y directions, powder can be selectively introduced to surface areas of the powder bed 6 independently of this, if necessary. The device 84 can, for example, be designed in the form of an outlet nozzle 84. The device 84 can be arranged on the carrier 36 of the peeling element 32, so that the device 84 moves together with the peeling element.However, in order to decouple the peeling process (peeling element 32) from the process of selectively introducing powder (device 84), it is advantageous if the device 84 is arranged on a separate carrier movable along the surface of the powder bed.

Claims

[1] Device (2) for powder bed-based generative manufacturing of metallic components, with a material reservoir (4) for receiving a powdered metal material which can be selectively melted by means of a melting device, the material forming a powder bed (6) in the material reservoir, with at least one stripping element (32) for shaping the surface of the powder bed (6), wherein the stripping element (32) is designed in the manner of a doctor blade and defines a stripping edge (34), with a movable support (36) on which the or each stripping element (32) is arranged, wherein the support (36) is designed such that the stripping edge (34) for stripping the surface of the powder bed is arranged relative to the latter in a stripping plane (xy plane, Fig. 3) is movable, wherein the or each stripping element (32) is arranged on the carrier (36) so as to be adjustable along an adjustment axis (z-axis, 38) perpendicular to the stripping plane relative to the carrier (36) for setting a stripping position of the stripping edge (34), wherein the stripping position relative to the carrier (36) is fixed at least in phases during the stripping process or is variable around a zero position in accordance with a high-frequency oscillation and wherein the adjustment axis (38) is assigned a drive device (40), characterized by , that the peeling edge (34) is formed by a plurality of peeling elements (44-50) arranged adjacent to one another in the longitudinal direction of the peeling edge (34), that at least two pulling elements (44-50) are each assigned a separate, independently controllable drive device, wherein the device (2) has a control device (12) for controlling the drive devices, wherein the device (2) comprises an optical measuring device (18) for three-dimensional measurement of the topography of the surface of the powder bed (6), wherein the measuring device (18) is in signal transmission connection with the control device (12) for controlling the drive device (40) or the drive devices in such a way that the drive device (40) or the drive devices can be controlled depending on the measurement result of the measuring device (18), and wherein the control device (12) is programmed for automatic control of the drive device (40) or the drive devices as a function of the measurement result of the measuring device (18), such that a desired topography of the surface of the powder bed (6) is automatically formed. [2] Device according to claim 1, wherein each of the stripping elements (44-50) is assigned a separate, independently controllable drive device. [3] Device according to claim 1 or 2, wherein at least one drive device is designed as a piezo actuator. [4] Device according to one of the preceding claims, wherein the peeling elements (44-50) are arranged on a peeling element module. [5] Device according to claim 4, wherein the peeling element module or a part of the peeling element module is detachably connectable or connected to the carrier (36). [6] Device according to claim 4 or 5, wherein the peeling element module comprises a passive peeling edge module (52), on which a plurality of peeling edge elements movable independently of one another in the direction along the adjustment axis (38) are arranged next to one another, and an active actuator module, on which a plurality of independently controllable actuators are arranged, each of which is assigned to one of the peeling edge elements for adjusting the same along the adjustment axis (38). [7] Device according to claim 6, wherein the actuator module is fixedly connected to the carrier (36) and the peel-off edge module (52) is detachably connected to the carrier (36). [8] Device according to claim 6 or 7, wherein the peeling edge module (52) comprises a strip (54) made of sheet metal or another elastically springy material, which is angularly shaped and has a first leg (56) which is divided into tongue-like peeling edge segments (42, 64) by incisions (58, 60) spaced apart from one another along the longitudinal direction of the peeling edge (34), and the other leg of which is connectable or connected to the carrier (36) or to a component connected to the carrier (36), each of the peeling edge segments (62, 64) being movable along the adjustment axis by an associated actuator (76). [9] Device according to one of the preceding claims, with a vibration device for subjecting the stripping element (32) or the stripping elements (44-50) to high-frequency vibrations. [10] Device according to one of the preceding claims, wherein the carrier (36) is designed and arranged for a translational movement along a linear pull-off axis. [11] Device according to one of the preceding claims, wherein at least one pulling element (32) is translationally movable for adjustment along the adjustment axis. [12] Device according to one of the preceding claims, wherein at least one pulling element (32) is rotatable about a rotation axis for adjustment along the adjustment axis.

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