Closable overflow mechanism and method for an additive manufacturing device

Abstract

The invention relates to a device for decoupling a process chamber (21) of a machine tool from a powder delivery region which is designed to receive and / or dispense material powder (33), wherein the machine tool is designed to build a workpiece layer by layer by means of applied material layers of the material powder (33), and the device is characterized in that at least one activatable sealing element (2, 3, 4, 5) is provided for decoupling the powder delivery region from the process chamber (21).

Description

[0001] Lockable overflow mechanism and method for an additive manufacturing device

[0002] The present invention relates to a lockable mechanism or closure mechanism for a machine tool for the layer-by-layer additive construction of workpieces and a method for removing excess powder using a fluid.

[0003] Prior art has revealed primary forming processes for the additive manufacturing of three-dimensional workpieces, in the course of which a workpiece is built up layer by layer from a provided material.

[0004] For this purpose, a powdered material is usually applied as a material layer to a carrier located in a process chamber of a machine tool and then solidified into a workpiece layer by site-specific irradiation, for example by melting or sintering the individual material particles of the material layer.

[0005] Once a workpiece layer has solidified, a new layer of raw material is applied to the substrate or to the already formed workpiece layer, and the area is irradiated again at a specific location. In this way, the workpiece is successively built up layer by layer from a multitude of material layers applied to the substrate.

[0006] During the coating process, a slightly larger quantity of powder (material powder) is typically applied than is geometrically necessary for the desired layer thickness. The excess, unprocessed material is then conveyed, for example, into a discharge opening. Current technology utilizes mechanical equipment, such as a screw drive, to remove the powder for subsequent processes. However, such mechanisms can negatively impact the manufacturing process, for example, through vibration.

[0007] During the manufacturing process, undesirable effects occur that negatively impact the process conditions within the process chamber (main process) and ultimately affect the manufacturing quality. For example, exhaust gases generated during solidification or the stirring up of unsolidified material contaminate the process chamber, and the process chamber is progressively heated by the waste heat generated during irradiation. To maintain optimal process conditions, a process gas flow is typically directed through the process chamber to remove contaminants and waste heat. This process gas flow can be precisely directed through one or more defined inlets and / or outlets.Further openings and extensions in the process chamber, which are necessary for secondary processes, for example, can negatively affect the flow and atmosphere of the main process.

[0008] One object of the present invention is therefore to reduce the influence on the main process while increasing process quality and stability. A further object is to provide improved powder removal. Additionally, it is an object to propose an optimized method for feeding or removing powder.

[0009] To solve these problems, the features of the independent claims are proposed. Advantageous further developments are found in the dependent claims. The respective dependent claims relate to preferred embodiments, which can be provided individually or in combination.

[0010] According to one aspect of the invention, a method for decoupling a process chamber of a machine tool configured for the layer-by-layer additive manufacturing of workpieces from layers of powder (material powder) is provided. The machine tool is, in particular, a manufacturing system for selective laser melting (SLM). Advantageously, at least one activatable sealing element is provided.

[0011] By using an activatable sealing element at an opening for powder feed or discharge, the process chamber can be operated in isolation from disturbances caused by secondary processes. At least one substantially elongated, activatable sealing element can be provided to close the openings. The activatable sealing element can be variable in shape and / or movable. As an advantageous application example, an inflatable rubber seal, particularly made of silicone, can be provided. An extruded profile seal can be supplied as a semi-finished product, and its ends can be closed by means of a plug.

[0012] A machine tool for additive manufacturing is particularly preferred. To decouple the process chamber from a powder conveying area, which is configured for receiving and / or discharging material powder, the machine tool can have at least one activatable sealing element for decoupling the powder conveying area from the process chamber. After the activated sealing element has decoupled a discharge chute for removing excess powder from the process chamber, namely by sealing the discharge opening in a powder- and pressure-tight manner, the powder can be removed. The main process can continue uninterrupted during this time. Since the discharge chute is separated from the process chamber in the decoupled state, there is virtually no further interaction between the atmospheres. Thus, the process quality can be improved, and the pressure decoupling allows for the operation of secondary processes at different pressures.Furthermore, gas / particle backflow into the (main) process can be prevented / reduced. Ultimately, process stability can be increased.

[0013] The machine tool can comprise at least one feed opening for supplying process powder into the process chamber and at least one discharge opening for removing process powder from the process chamber. The decoupling device, or the device according to the invention, can be located at the feed opening as well as, independently, at the discharge opening.

[0014] Upstream of the powder feed, secondary processes such as powder preparation, pre-dosing, etc., may occur. These processes are subject to different atmospheric conditions, for example, regarding pressure, temperature, and the composition of the process gas. Decoupling the process chamber from these secondary processes is desirable.

[0015] In the process for the layer-by-layer build-up of workpieces from powder (or metal powder), process gases, especially inert gases, are generally used. These can be directed precisely over the surface of the powder being processed by guiding the flow. This allows impurities in the process gas to be removed immediately. Particularly in the case of plastics as the material being processed, it is advantageous to control the ambient temperature in the area of ​​the powder surface in order to minimize thermal distortion. A device for producing shaped parts according to the principle of selective laser melting is known, for example, from DE 102019200680 A1. The subject matter of this application is hereby incorporated by reference. Excess process powder that is not required for coating must be removed from the process chamber.After the coating process, a recoater can transport excess powder into at least one discharge opening (or overflow opening). This is typically located within the area of ​​the material layer and preferably below it. Some process gases, preferably inert gases, especially argon, have the property of being denser than ambient air and tend to collect in lower-lying areas, particularly in the aforementioned discharge opening. In the case of a sealed discharge opening, reduced process gas consumption and / or reduced contamination of the discharge opening can be achieved.

[0016] A device for the layer-by-layer construction of objects from powdered material by means of optical interaction can comprise a process chamber and at least one optical module. The device can, in particular, utilize a selective laser melting process. The process chamber can be designed to provide a work area at a build platform. At least one optical module can be provided, which is part of an irradiation device or which forms an irradiation device for the site-selective irradiation of the material present in the build platform. Preferably, the optical module is arranged above and spaced apart from the process chamber. A primary support or a mounting element can enable the central connection of individual main components of the device. The mounting element or base element functions as a support structure for receiving or storing the main components of the device or manufacturing system.The main components include, in particular, those components of the device that are necessary for the manufacture of the object, in particular one or more optical modules, the process chamber, a recoater, and a Z-axis and / or lifting device.

[0017] For closing the openings (powder discharge opening and / or powder feed opening), at least one substantially elongated, activatable sealing element can be provided. The aspect ratio here is the sealing length in relation to the maximum profile height in the expanded or activated state. An element with an aspect ratio >2 can be considered elongated.

[0018] Specific states can be defined to control the condition of the sealing element. In the following, the terms "active" or "activated" refer to the extended or expanded state of the seal, in which the corresponding opening should be closed. "Inactive" or "deactivated" describes the desired state, in which a corresponding opening should be unobstructed. Alternatively, depending on the sealing element used, the opposite convention can be applied. Intermediate states are also possible.

[0019] A preferred embodiment involves the use of pressure from a fluid, preferably compressed air, which causes the sealing element to deform due to the pressure difference between its inner and outer surfaces. The pressure difference Ap is defined as the external pressure subtracted from the internal pressure of the sealing element. Activation is induced by setting Ap + po > 0. The constant po, which depends on the sealing element, describes the fact that the inflatable seal is either active, inactive, or in an intermediate position when Ap = 0. Depending on the sealing element used, an Ap + po < 0 is necessary to initiate deactivation. This is caused by effects such as the sealing element adhering to a opposite surface.

[0020] The outer contour of the sealing element can be substantially convex in its activated state. This includes, in particular, round, circular, and oval shapes. The description as a substantially convex structure remains unaffected by minor indentations towards the interior of the seal relative to the profile height of the sealing element. Designing an overlap with the mating element is helpful for compensating for tolerances and achieving the intended sealing effect. The integration of an internal cavity allows activation by pneumatic or hydraulic pressure.

[0021] The use of small raised sections above the average profile contour provides additional support. These can be triangular, like saw teeth, square, like crenellations, or polygonal. Partial or complete rounding of these raised sections is also possible.

[0022] In the deactivated state, the seal can have a substantially concave inner contour. Depending on the internal preload and / or the need to provide the shape through negative pressure relative to the seal's inner surface, the outer contour in the inactive state can also be flat or slightly convex.

[0023] The sealing element can be integrated into the sealing housing. The sealing housing can be provided, for example, in a one-piece, two-piece, or more than two-piece design. It is also possible for the sealing housing to be integrally installed in the machine tool.

[0024] The device can be implemented using pairs of opposing sealing elements whose outer surfaces engage with each other when activated. This reduces the gap to be bridged by each sealing element, and thus the required volume of fluid used for actuation, as well as the reaction time. Alternatively, the two inflatable seals can be connected using a fitting, requiring only a single pressure connection for activation.

[0025] The sealing housing can be designed to be replaceable for simplified maintenance or when changing the process powder, thus preventing potential contamination. If this is not the case, a low-maintenance and easy-to-clean design is preferable.

[0026] The integration of the expanding sealing element (into the sealing housing) can be achieved, for example, through a form-fit connection, via geometric adaptation and / or the use of an inflation mechanism, or through a force-fit connection, via screws, or through a material-fit connection, via adhesive bonding. Other options are also possible, such as omitting an explicit connection mechanism. Combinations of the methods presented, as well as other possibilities, are also available.

[0027] In the application example of using one or more pneumatic sealing elements to implement the function of the locking mechanism, the pressure supply and / or pressure discharge can be provided by a fluid either inside the housing, outside the housing, or on the side faces of the sealing element. Combinations or other control options are also possible.

[0028] In the application example of using one or more mechanically displaceable sealing elements to implement the function of the closure mechanism, an installation space adapted to the specific requirements must be provided. The sealing system can comprise one or more sealing elements, not all of which necessarily need to be displaceable. For the application of powder removal, the geometric design of the housing for the closure mechanism is generally subject to the following functions: a. Containment of the powder b. Provision of the closure mechanism c. Temporary storage of the powder d. Removal of the powder e. If necessary, fluidization of the powder.

[0029] After completion of the powder application process in the process chamber, the coater can be moved to the edge and / or over the discharge opening (also called the minimum gap). Excess powder can be drawn into this opening by gravity. Alternatively, additional extraction through the discharge opening can be advantageous. The geometric design is advantageous because the surfaces have low roughness. The minimum gap can be achieved by a parabolic trajectory of the powder, which is initially propelled by the coater to the edge of the opening and then accelerated by gravity. The hopper walls of the opening are designed so that the powder does not rebound back into the process chamber after impacting the hopper walls. The process can be assisted by a fluid flow.

[0030] After passing through the inlet area (funnel walls) of the discharge opening, the process powder can pass the sealing element (or elements) with minimal disturbance. In a design with only one sealing element, the powder flow can preferentially contact the side opposite the sealing element.

[0031] The powder can collect at the lowest point or points of the structure (especially the sealing housing or discharge chute). The discharge chute is located in this area. Depending on the desired final position, the shape can be flat, convex, and / or concave. The discharge chute can be integrated into the sealing housing. A separate overflow reservoir is not required. A concave design offers advantages in that a fluid flow can be used as a transport mechanism for removing the excess powder. Advantageously, the discharge chute has numerous openings through which a fluid can be guided to fluidize the powder within the chute. The at least partially turbulent fluid detaches the powder from the surface of the discharge chute. A powder is fluidized when all particles are surrounded by gas and the powder particles are essentially no longer in contact with each other.The resistance of a single powder particle holds it freely in space, where it is moved by the mass flow of process gas. Afterwards, the discharge chute can be easily extracted or blown out. This method is gentler on the material, less complex in terms of component size, and vibration-free compared to conventional methods such as [example missing].

[0032] Worm drive or vibrating conveyor.

[0033] Flow simulations allow the cross-section to be optimized and adapted to the specific application requirements. A variable cross-section along the length of the drainage channel is also conceivable.

[0034] The fluid used for transport can be inert gas and / or compressed air drawn from a gas circuit. Decoupling the process chamber from the powder conveying area allows for different pressures in the secondary processes than in the main process. This increases energy efficiency and enhances process stability, particularly within the process chamber.

[0035] The control of the fluid flow for the removal of the process powder can be designed to depend on the active / inactive state of the activatable sealing element or be completely independent. Removal is not necessary for every coating cycle. Furthermore, the use of the activatable sealing element allows for targeted timing of the decoupling at times when the process in the process chamber is undisturbed by secondary processes. Activation and / or deactivation can be controlled via the position of the coater. A method for decoupling a process chamber of a machine tool from a powder conveying area designed for receiving and / or discharging material powder, wherein at least one activatable sealing element is provided, can include the step of decoupling the process chamber from the powder conveying area by changing the shape and / or displacement of the sealing element.In one embodiment, a sliding seal is used instead of an inflatable one. The sliding element can be achieved, for example, by mounting it on a (linear) guide, so that to activate the seal, the element is moved along the guide until contact is made and a seal is thus achieved. A combination of a sliding seal and an inflatable seal is also possible, resulting in a sliding inflatable seal.

[0036] The change in shape and / or displacement of the sealing element can advantageously be achieved by generating a pressure difference between an inside and an outside of the sealing element.

[0037] The sealing element can be switched to an activated state and to a deactivated state, and a coating unit can be provided for applying a powder coating. The activation and / or deactivation can be advantageously controlled depending on the position of the coating unit.

[0038] Furthermore, a computer-implemented method is proposed which, when applied to the described machine tool and a controllable computing unit, causes the device to perform at least one or more of the aforementioned process steps.

[0039] Advantageous embodiments and further details of the present invention are described below with reference to various exemplary embodiments and schematic figures. The connection is explained in more detail in the schematic drawings. Brief description of the figures

[0040] Figure 1: shows the process gas flow within the process chamber of a machine tool for the layer-by-layer additive manufacturing of workpieces;

[0041] Figure 2: shows a flow diagram of the process gas flow for powder removal;

[0042] Figures 3a to 3c: show the process of closing the process chamber in an exemplary embodiment using a simple inflatable seal;

[0043] Figures 4a to 4c: show the process of closing the process chamber in a further embodiment using a double inflatable seal;

[0044] Figure 5: shows a cross-sectional view through a multi-part housing at a feed opening with an activated inflation seal;

[0045] Detailed description of preferred embodiments

[0046] Exemplary embodiments of the present invention are described in detail below with reference to exemplary figures. The features of the exemplary embodiments can be combined in whole or in part, and the present invention is not limited to the described exemplary embodiments.

[0047] Figure 1 schematically shows a cross-section of a process chamber 21, laterally bounded by process chamber walls 21a, of a machine tool for the layer-by-layer build-up of a workpiece from powder (in particular, a manufacturing system for selective laser melting, SLM). This includes at least one laser light source which, via a control system coupled to the machine tool, generates a light beam modified for interaction with the material powder 51 to be processed, and this light beam is focused, by means of various optical elements, preferably integrated in a scan head, such as focusing or diverging lenses, mirrors, optical filters, etc., via a predefined light path onto the aforementioned material 51, which is usually positioned in the process chamber 21. The light source is preferably separated from the process chamber 21 by a protective glass 47.Openings for powder supply and powder removal, as well as other features such as the coater, are not shown.

[0048] Furthermore, a controlled process gas flow is used to create the most homogeneous environment possible, enabling ideal process conditions during the irradiation of the powder material. For this purpose, the process gas inlets 45 and 50 establish a preferred flow direction of the process gas into the process chamber 21, which is indicated by arrows. The process gas is intended to exit the process chamber 21 through the process gas outlet 46 and be supplied to secondary processes, such as conditioning and recirculation back into the process chamber.

[0049] The process gas flow and atmosphere in the process chamber are of fundamental importance in additive manufacturing. The removal of excess or overdosed powder from the process chamber is conventionally achieved using mechanical elements such as a screw drive. However, such mechanisms negatively impact the manufacturing process through vibrations, flow obstructions, and pressure differences, and can also disrupt the process gas flow in the main process. Therefore, it is necessary to enable the removal (or supply) of material powder as independently as possible from the main process and to ensure efficient powder feed and removal.

[0050] Figure 2 schematically shows an application example according to the invention for a process gas flow for the removal of the powder (material powder or metal powder in an SLM process) from the process chamber 21 of a manufacturing plant.

[0051] The material layer made of powder is located within process chamber 21. In the SLM system (i.e., the manufacturing system), a material powder to be processed is applied layer by layer to a movable base plate and locally remelted by means of focused laser irradiation so that, through continuous deposition,

[0052] By exposing and fusing further layers of material, a three-dimensional workpiece (i.e., the object to be manufactured) can be generated (additive manufacturing). Before each iterative process of the interaction between the laser irradiation and the powder for the layer-by-layer construction of the workpiece, the coater 31 applies a thin, primarily homogeneous layer of unprocessed powder. The directional arrow on the coater 31 indicates, for example, a possible conveying direction (e.g., x-direction) of the powder, in the extension of which an overflow mechanism or closure mechanism 1A; 1B is located. The section plane AA is explained in more detail in Figures 3a to 3c and 4a to 4c. The closure mechanism 1A, 1B generally describes an overflow mechanism for receiving excess powder from the process chamber 21, while simultaneously allowing the overflow to be closed off from the process chamber 21.

[0053] The coater 31 is moved along the direction of coater movement during the manufacturing process. The coater 31 can therefore be moved from a first to a second end position along an x-direction to spread a layer of powder (material powder) onto a base plate in a first traverse movement. In a subsequent second traverse movement, the coater can be moved in the opposite direction, namely from the second end position back to the first. Such a coater is described, for example, in DE 102022114418 A1, the disclosure of which is hereby incorporated. The coater comprises, on its underside, a spreading element facing the base plate, which in this case is designed as a coater lip and is configured to spread a layer of powder located on the carrier during a traverse movement.During the movement to the first and / or second end position, the coater 31 conveys excess powder 33 into one (or more) discharge openings 37 in the area of ​​the closure mechanism 1A, 1B, where it can be collected, for example, in a discharge chute.

[0054] To enable the removal of material powder as independently as possible from the main process and thus achieve efficient powder removal without disrupting the main process, the invention proposes the use of an activatable seal (here an inflatable seal). This inflatable seal is installed in a side wall of the discharge chute, and when the seal is activated, i.e., when it is inflated, for example, until it makes sealing contact with an opposing sealing surface of the discharge opening, a powder- and pressure-tight closure of the discharge opening 37 can be achieved.

[0055] Advantageously, a control system activates the seal as soon as the coater reaches an endpoint and thus the excess powder has been pushed into the discharge opening 37 by means of the coater lip. Preferably, the seal can be inflated until a predetermined contact pressure is reached on the opposite sealing surface, so that the required seal can be achieved by the seal.

[0056] Once the activated seal has decoupled the discharge chute from the process chamber 21 by sealing the discharge opening 37 in a powder- and pressure-tight manner, the powder can be transported into the discharge chute. The main process can continue uninterrupted during this time, and the coater 31 can, for example, apply another layer or the exposure process can be carried out. Because the discharge chute is separated from the process chamber in the decoupled state, there is virtually no further interaction between the atmospheres.

[0057] The gas circuit shown in Figure 2, depicted as a closed system in this application example, runs clockwise. A process gas generator 26, for example, generates a differential pressure between its inlet and outlet by means of fan blades. This results in a mass flow of process gases. In the area of ​​the closure mechanism 1A; 1B, the coater 31 introduces the excess powder from the coating process into the process gas flow system. A preferred direction of movement is symbolized by 53. The mass flow is designed such that it is capable of transporting the powder. The required mass flow can be reduced particularly advantageously by fluidizing the powder.

[0058] In the downstream section of the sealing mechanism 1A; 1B, the process gas stream can, for example, split. In the application example, a first branch leads to a separator 22, which is designed, for example, as a cyclone and separates the process powder from the process gas. In the next step, the process powder is transferred to a powder storage container 24. Another (alternative or additional) branch leads to a further separator 23, which can also be designed as a cyclone and feeds the separated process powder to a powder processing unit 25.

[0059] Further downstream of separators 22 and 23, the process gas streams merge and complete the circuit at the process gas generator 26. The process flow illustrated here can also be extended to include other process steps. Likewise, their sequence and number are not exclusive. For example, the process gas generator can also be located downstream of the closure mechanism with respect to the preferred flow direction. In a particularly advantageous embodiment, the gas circuit shown in Figure 2 is integrated into the main gas circuit, so that one gas circuit is used both for powder removal at the closure mechanism and for providing a primary and a secondary flow in the process chamber.

[0060] Figures 3a to 3c show the process steps in an application example according to the invention. A simple inflatable rubber seal 2 is used as the activatable sealing element (dynamic seal). The dynamic seal can be controlled via an electronic solenoid valve, and a pressure reducer can also be provided.

[0061] Figure 3a shows the closure mechanism 1A in a deactivated state and therefore in the state of the first process step. A sealing housing 32A, 32B comprises a discharge opening 37 (also referred to as an overflow opening), an activatable sealing element 2, and a discharge chute 49. After a coating process, the coater 31 uses its coater lip to convey excess process powder 33 to the edge of the discharge opening 37, from where it is transported gravimetrically past the discharge opening 37 and the sealing element 2 into the discharge chute 49.

[0062] The upper part (i.e., the part facing the coater 31) of the discharge opening 37 is funnel-shaped and therefore functions as a funnel, channeling the material transported from the coater 31 via the discharge opening 37 to lower-lying components. The activatable seal 2 is in a deactivated state and opens the passage to the discharge shaft 49.

[0063] In other words, the discharge opening 37 therefore comprises a funnel section, which represents the first entry area for the powder to be discharged. The walls or side walls of the discharge opening converge in a funnel shape in this area, converging towards a common center, without, however, touching or closing the opening. Following the funnel section is a region in which the side walls of the discharge opening 37 are arranged parallel to each other. The sealing element 2 is also provided in one of the side walls in this region. Preferably, the side walls in this region are vertically aligned and parallel to each other. Thus, in the activated state, the sealing element 2 contacts a vertical side wall of the discharge opening 37. In the deactivated state, the sealing element 3 does not project beyond the side wall (in the horizontal direction).Preferably, in the deactivated state, the sealing element is located horizontally spaced from the side wall and thus further away from a center of the discharge opening 37 than the (inner) side wall of the discharge opening 37.

[0064] The outer contour of the inflatable seal 2 is designed, in this application example concavely, such that the excess process powder 33 can pass through the seal largely unimpeded. Preferably, a sealing surface of the sealing element (or the outer surface of the sealing element facing the discharge opening) is flush with a side surface of the discharge opening 37 in the deactivated state, so that, in the deactivated state of the sealing element, the powder can be drawn into the discharge chute without obstruction. The inwardly concave area of ​​the sealing element "rolls" outwards when pressurized, thus reaching its maximum stroke. For example, the sealing element is inserted into a groove, screwed in, or glued in place. The discharge chute is essentially round or slightly oval and provides a deepest area around which the collected powder can accumulate.Preferably, the discharge chute 49 is located directly below the discharge opening 37, so that the powder 33 can be moved directly through the discharge opening (especially by gravity) into the discharge chute 49. In Figure 3b, the process powder 33 has reached a lower position in the discharge chute 49 and remains there. The inflatable seal 2 was activated by applying a differential pressure Ap that satisfies the condition Ap + po > 0. The outer contour of the sealing element is now essentially convex and contacts the opposing wall (counter-bearing or sealing surface).

[0065] The discharge opening 37, and thus the process chamber 21 above it, is decoupled from the discharge shaft 49 and therefore from the downstream powder conveying area. The use of the inflatable seal ensures that the decoupling (in particular, the separation) is designed to provide a high degree of pressure decoupling between the process chamber 21 and the powder conveying area.

[0066] The achieved decoupling is at least a pressure decoupling between an atmosphere in the process chamber 21 and an atmosphere in the powder conveying area (i.e. discharge opening with discharge shaft) where the powder conveying area is a powder discharge area for the removal of material powder.

[0067] In Figure 3c, the inflation seal 2 remains active. In this process step, the powder 33 is transported away. The process gas flow provided by the process gas generator 26 points, for example, into the plane of the image. The at least partially turbulent fluid detaches the powder from the surface of the discharge chute 49. A resistance force of an individual powder particle holds it freely in space, and it is carried along by the mass flow of process gas.

[0068] With material powders of increased density and / or coarser texture, the flow component caused by turbulence, which runs perpendicular to the main flow, may not result in continuous detachment of the powder particles. In this case, the material may be transported by sliding, rolling, or bouncing across the surface.

[0069] As an optional solution to aid removal, the possibility of intentionally swirling the process powder-fluid mixture is presented, giving it fluid-like properties. This is generally referred to as fluidization. This can be achieved, for example, using fluid outlets located in the housing wall. In the application example, inlets on the underside of the housing are symbolized by arrows.

[0070] Figures 4a to 4c describe the process steps analogously to Figures 3a to 3c in a further application example. In contrast to Figures 3a to 3c, two opposing sealing elements are used. Preferably, the sealing elements are inserted opposite each other into respective grooves in the side wall of the discharge opening 37 and aligned with each other.

[0071] In Fig. 4a, the two inflation seals 3, 4 are in the inactive state. Their geometric shape (especially a concave or flat outer surface in the inactive state) allows the powder to pass through as undisturbed as possible.

[0072] After completion of the first step and passage of the powder 33 to the discharge chute 49, both inflatable seals 2, 3 are activated (particularly synchronously), as shown in Fig. 4b. The inflatable seals 2, 3 are pressurized to a predetermined internal pressure, causing them to inflate. The gap between the outer surfaces of the seals then decreases until contact is achieved. For example, when the predetermined internal pressure in the sealing elements is reached, the inflation process can be stopped and the seals can enter a static (inflated) state. Alternatively or additionally, sufficient contact can also be determined by measuring the contact forces of the sealing surfaces of the inflatable seals. Once the activated state is fully reached, the seals seal the discharge chute 49 from the process chamber 21.This separates process chamber 21 from the powder conveying area.

[0073] Fig. 4c shows the removal of the process powder by the process gas flow. In this application example as well, the removal can be supported by the fluidization mechanism. Figure 5 shows an exemplary cross-sectional view through a multi-part sealing housing 32A at a feed opening 36 with a single, activated inflatable seal 5.

[0074] The cross-sectional view reveals the multi-part sealing housing 32A, which is composed of the base carrier 35 and the sealing carrier 43. The feed opening 36 penetrates the base carrier 35. At the upper end of the image, the powder conveying area for powder supply is located, while the lower part of the image borders an area leading to the process chamber 21. The feed opening is designed such that the passing powder slides gravimetrically along the right wall of the base carrier into the process chamber 21.

[0075] The inflatable seal 5 is attached to the seal carrier 43 on its inner side by means of a screw connection 52. The elongated sealing element 5 is closed at its ends and is pressurized relative to its interior to activate it at the pressure port 44, to which a pressure passage through the seal carrier 43 is connected.

[0076] The sealing carrier 43 is connected to the base carrier 35 via screw connections 39, 40 and decoupled from the supply opening 36 by sealing elements 41, 42.

[0077] The achieved pressure decoupling of the feed (powder feeder) allows the powder supply to be decoupled from the main process. This enables the dosing process to take place independently of the main process. Only when powder is required is the inflatable seal opened and the powder transferred to the process. This minimizes the impact on the main process.

[0078] The decoupling between an atmosphere in the process chamber 21 and an atmosphere in the powder conveying area can thus also be achieved in a powder feed area for the supply of material powder by means of the sealing arrangement according to the invention. In a particularly preferred embodiment, a sealing arrangement according to the invention with an activatable seal is provided in both a powder feed area and a powder discharge area. This allows the process quality to be increased, and the pressure decoupling enables work to be carried out in secondary processes at different pressures. In addition, gas / particle backflow into the (main) process can be prevented / reduced. Ultimately, process stability can be increased.

[0079] The features, components, and specific details provided can be exchanged and / or combined to create further embodiments, depending on the required purpose. Any modifications that are within the knowledge of a person skilled in the art are implicitly disclosed in this description.

[0080] Reference symbol:

[0081] 1A; 1B Locking mechanism

[0082] 2-5 Sealing element

[0083] 21st Tribunal

[0084] 21 a Process chamber walls

[0085] 22-23 separators

[0086] 24 powder storage

[0087] 25 Powder processing unit

[0088] 26 process gas generators

[0089] 31 coaters

[0090] 32A; 32B Sealing housing

[0091] 33 powders

[0092] 34 Fluidization

[0093] 35 base carriers

[0094] 36 Inlet

[0095] 37,38 Collection opening

[0096] 43 sealing carriers

[0097] 44 Pressure connection

[0098] 39, 40 screw connection

[0099] 41, 42 Sealing element

[0100] 45.50 process gas inlets

[0101] 46 Process gas outlet

[0102] 47 Protective glass

[0103] 48 screw connection

[0104] 49 Discharge shaft

[0105] 51 Material layer

[0106] 52 screw connection

[0107] 53 Direction of movement

Claims

Claims 1. Device for decoupling a process chamber (21) of a machine tool from a powder conveying area which is set up for receiving and / or discharging material powder (33), wherein the machine tool is set up for the layer-by-layer construction of a workpiece by means of applied material layers made of the material powder (33) and the device is characterized in that at least one activatable sealing element (2, 3, 4, 5) is provided for decoupling the powder conveying area from the process chamber (21).

2. Device according to claim 1, wherein the sealing element is substantially elongated; and / or the shape variation of the sealing element (2, 3, 4, 5) is caused by a pressure difference from the inside of the sealing element (2, 3, 4, 5) to the outside of the sealing element (2, 3, 4, 5) and wherein a hydraulic pressure or a pneumatic pressure is preferably present on the inside.

3. Device according to at least one of the preceding claims, wherein the decoupling is at least a pressure decoupling between an atmosphere in the process chamber (21) and an atmosphere in the powder conveying area, and preferably the powder conveying area is a powder removal area for removing material powder (33) from the process chamber (21) or a powder supply area for supplying material powder (33).

4. Device according to at least one of the preceding claims, wherein the sealing element (2, 3, 4, 5) has an inner cavity and wherein the sealing element (2, 3, 4, 5) has a substantially convex outer contour in an activated state; and / or the sealing element (2 ,3 ,4 ,5) has a crenellated, arcuate and / or sawtooth-shaped outer contour in an activated state; and / or the sealing element (2, 3, 4, 5) is substantially flattened or concave in a deactivated state.

5. Device according to at least one of the preceding claims, wherein the sealing element (2, 3, 4, 5) is formed from an elastic material and the sealing element (2, 3, 4, 5) is in particular an inflatable rubber seal.

6. Device according to at least one of the preceding claims, wherein at least two activatable sealing elements (2, 3, 4, 5) are provided, which are arranged opposite each other and for decoupling, outer surfaces of the sealing elements (2, 3, 4, 5) contact each other.

7. Device according to at least one of the preceding claims, further comprising: in a powder supply area, at least one supply opening (36) for supplying material powder (33) from the powder supply area; and in a powder discharge area, at least one discharge opening (37, 38) for removing material powder (33), in particular excess and / or overdosed material powder (33), from the process chamber (21), wherein the discharge opening (37, 38) is preferably a powder overflow.

8. Device according to at least one of the preceding claims, wherein the sealing element (2, 3, 4, 5) is provided at at least one discharge opening (37, 38) for separating a powder discharge area from the process chamber (21).

9. Device according to at least one of the preceding claims, further comprising a sealing housing (32A; 32B) in which the at least one sealing element is inserted. (3, 4, 5, 6) is inserted at one end so that a sealing surface of the sealing element (3, 4, 5, 6) is exposed and wherein the sealing housing (32A; 32B) is designed as a single piece or in multiple parts; and / or wherein the sealing housing (32A; 32B) is provided in an interchangeable manner, in particular depending on the material powder (33) used; and / or wherein at least one discharge chute (49) is provided for the discharge of material powder (33) is provided in the powder removal area and the removal shaft is preferably integrated into the sealing housing (32A; 32B).

10. Device according to at least one of the preceding claims, wherein a flowing fluid is provided for the removal of the material powder (33) transported into the at least one discharge opening (37, 38), and wherein the fluid is preferably inert gas and / or compressed air from a gas circuit of the machine tool.

11. Device according to at least one of the preceding claims, wherein the discharge shaft (49) has one or more fluid openings on an inner surface for introducing fluid into the material powder (33) to fluidize (34) of the material powder (33) as a mechanism to support the removal of the material powder (33).

12. Method for decoupling a process chamber (21) of a machine tool from a powder conveying area configured for receiving and / or discharging material powder (33), wherein the machine tool is configured for the layer-by-layer construction of the workpiece from applied material layers of material powder (33) and wherein at least one activatable sealing element (2, 3, 4, 5) is provided; the method is characterized in that by a change in shape and / or displacement of the sealing element (2, 3, 4, 5) a decoupling of the process chamber (21 ) from the powder conveying area is achieved.

13. Method according to claim 12, wherein the change in shape and / or displacement of the sealing element (2, 3, 4, 5) is achieved by generating a pressure difference between an inside and an outside of the sealing element (2, 3, 4, 5).

14. Method according to at least one of claims 12 or 13, wherein the at least one sealing element (2, 3, 4, 5) can be moved to an activated state and to a deactivated state by deactivation, and wherein a coater (31) is provided for applying a powder layer (51); and wherein the activation and / or deactivation is controlled depending on the position of the coater (31).

15. Computer-implemented method which, when applied to a computing unit controllable by the device according to claim 1, controls the device according to claim 1. Claim 1 causes at least the process steps according to claim 12 to be carried out.

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