WO2022003004A1

WO2022003004A1 - Mixing device for producing a powder mixture

Info

Publication number: WO2022003004A1
Application number: PCT/EP2021/067957
Authority: WO
Inventors: Thomas Reichel
Original assignee: Eos Gmbh Electro Optical Systems
Priority date: 2020-07-01
Filing date: 2021-06-30
Publication date: 2022-01-06
Also published as: DE102020208252A1

Abstract

A mixing device (18) serves for producing a powder mixture from a first powder component and at least one second powder component for an additive manufacturing device (1). The mixing device (18) comprises a first container (30) for receiving the first and/or the second powder component, wherein a discharge opening (34) for discharging the first and/or second powder component is provided at a lower limit of the first container (30), and a second container (40) for receiving the first and/or the second powder component, wherein the second container (40) is designed at least partially open toward a top side. The second container (40) has at least one fluidization zone (47), in order to introduce a gas into the second container (40). The mixing device (18) further comprises a powder line (50), which is attached to the discharge opening (34) of the first container (30) and guided into the second container (40).

Description

Mixing device for producing a powder mixture

The present invention relates to a mixing device for producing a powder mixture, an additive manufacturing device for manufacturing a three-dimensional object using such a powder mixture or an additive manufacturing device with such a mixing device, and a method for manufacturing a powder mixture.

Devices and methods for the additive manufacture of a three-dimensional object by selective solidification of a building material layer by layer are used for example in rapid prototyping, rapid tooling or additive manufacturing. An example of such a process is known as "selective laser sintering or laser melting". A thin layer of a powdery building material is repeatedly applied and the building material is selectively solidified in each layer by selective irradiation of a cross section of the object to be produced with a laser beam.

As a rule, a portion of the powder used as building material remains in such a manufacturing process, for example in the form of powder surrounding the manufactured object or excess powder which was fed to an overflow container when applied in layers by the coater. Such a powder, which has already been used in a previous manufacturing process, is also referred to as waste powder. To increase the efficiency, in particular the cost efficiency of the manufacturing process, it may be desirable to use a proportion of old powder as the building material. For this purpose, the old powder is usually mixed with what is known as new powder, ie powder that has not yet been used in a previous manufacturing process, and is made available as a build-up material for a further manufacturing process. In the case of an additive manufacturing process, it may also be desirable or necessary to mix a powder used as a build-up material from different powder components according to certain specifications, for example with regard to chemical and / or physical properties.

In both cases it is necessary to obtain a powder mixture as homogeneous as possible from the various powder components, i. H. the old and new powder or chemically and / or physically different powder components, in order to obtain a three-dimensional object with good, in particular as homogeneous as possible, component properties.

DE 102010043 166 A1 describes a device for mixing powder for an additive manufacturing device. The container in which the powder is mixed comprises a fluid-permeable lower plate and a stirring device in the form of a stirring tool.

US 2009/0169664 A1 describes a system for mixing a powder for a laser sintering machine, a new powder and an old powder being mixed in a mixing container. To mix the powders, they are circulated in a circuit.

EP 2450 177 A1 describes a powder treatment system for a 3D printer, where the system comprises a plurality of powder holding containers and a vacuum pump to convey powder between the powder holding containers. A dosing container is provided as the powder container in order to dose a sufficient amount of powder for a layer application, as well as an external powder container for preparing the powder. The external powder container comprises a lid and a conical wall, as well as an internal nozzle through which powder is discharged upwards.

The object of the present invention is to provide an alternative or improved mixing device or an alternative or improved method for producing a powder mixture for an additive manufacturing device in which, in particular, the homogeneity of the powder mixture is improved can and / or which enables a mixing of powder components which can be carried out as easily as possible and / or reproducible and / or at least partially automatically carried out.

This object is achieved by a mixing device according to claim 1, an additive manufacturing device according to claim 13 and a method according to claim 14. Further developments of the invention are each specified in the subclaims. In this case, the method can also be developed further by the features of the devices listed below or in the subclaims, or vice versa, or the features of the devices can also be used among one another for further development.

A mixing device according to the invention is used to produce a powder mixture from a first powder component and at least one second powder component for an additive manufacturing device in which a three-dimensional object can be produced by layer-wise selective solidification of a build-up material comprising the powder mixture. The mixing device comprises a first container for receiving the first and / or the second powder component, a dispensing opening for dispensing the first and / or second powder component being provided on a lower boundary of the first container, and a second container for receiving the first and / or the second powder component / or the second powder component, the second container being designed to be open at least in sections towards an upper side.

In the following, the powder mixture is described as a mixture of the first and second powder components. However, the invention is not limited to the use of two powder components; rather, three or more powder components can also be provided for use with the mixing device, in particular mixed by it. The first and second powder components and any further powder components preferably differ from one another in their chemical and / or physical properties. For example, the first powder component can be an old powder, which was already left over in a previous construction process as non-solidified and / or excess powder, and the second powder component can be a new powder. The lower limit of the first or the second container is preferably a container bottom of the respective container. The lower boundary of the first or the second container is preferably provided opposite a container lid of the first container (see below) or the top of the second container.

Furthermore, the second container of the mixing device has at least one fluidization zone for introducing a gas into the second container. The at least one fluidization zone is preferably provided in a lower container region of the second container. The lower container area is in particular a flea area of the second container which is adjacent to the lower boundary of the second container. A further (second) fluidization zone for introducing a gas into the first container can optionally be provided. Preferably, the fluidization zone (s) is or are each formed by a flea space which is separated from the first or second container by a gas inlet element, in particular a perforated plate and / or a porous plate.

The mixing device further comprises a powder line which connects to the dispensing opening of the first container and is led into the second container. The powder line is preferably provided substantially outside the first container. “Essentially outside of the first container” means that the powder line is provided over the majority of its line length outside of the first container, and in particular only the section of the powder line inserted into the second container is provided inside the first container.

The powder line thus forms, for example as a pipeline, a pulverfüh-generating connection between the dispensing opening of the first container and the interior of the second container. This enables, for example, the first and / or second powder component to be conveyed in a circuit, for example the powder component (s) exiting or exiting the second container through fluidization in the second container via its upper side, which is at least partially open, and into the first container arrives or arrive and from there in turn via the powder back into the second container. This promotion in a circuit can, for example, lead to good mixing of the two powder components. The fluidization zone is provided in or on the second container and the dispensing opening to which the powder line connects is seen on the first container, ie the area in which the powder is fluidized (ie in the second container) and a Dispensing areas of the powder (a lower area of the first container near the dispensing opening) are spatially separated from one another. In this way, for example, the longest possible distance can be achieved that the powder covers in a circuit during conveyance or over which the powder components can mix with one another. Overall, the mixing device according to the invention can provide a device for mixing different powder components with which a mixing process can be carried out in a simple manner and / or at least partially automatically and / or as reproducibly as possible and / or with which a powder mixture that is as homogeneous as possible can be produced .

Preferably, the second container is arranged substantially within the first container. Thus, according to this preferred embodiment, the first container is designed as an outer container and the second container is designed as an inner container, the second container also being able to protrude over the first container, for example. This makes it possible, for example, to have a compact as possible, i. H. Space-saving, mixing device to provide and / or to make the operation and / or construction of the Mischvorrich device as simple as possible, since the powder emerging from the second container by fluidization flows directly into the first container and thus, for example, no further structural elements, such as Powder lines are required as an additional connection between the two containers.

More preferably, the second container is provided in substantially all spatial directions from the first container in the latter, even more preferably substantially in the center of the first container. The term "essentially spaced from the first container in all spatial directions" means that touching the first and second containers in sections is not excluded Connect containers together. By spacing the two containers apart, it is possible, for example, to achieve improved mixing of the two powder components and / or good circulation in the circuit (see above).

Preferably, the first container can be closed on an upper side by a container lid and the second container is provided within the first container in such a way that an upper boundary of the second container is spaced from the container lid of the first container. The upper delimitation of the second container can be designed, for example, as a container edge of the second container. More preferably, the powder line is led into the second container through the container cover of the first container. As an alternative or in addition, the powder line is preferably led into an area of the second container that corresponds to the lower half, more preferably the lower third, of a distance between the lower limit, for example a container bottom, of the second container from the upper limit, for example a container edge, of the second container corresponds. In general, it is preferred that an inlet formed by the powder line is provided into the second container below the upper limit of the second container.

Because the second container is designed to be open at least in sections towards an upper side and its upper boundary is spaced from the container lid of the first container, it is possible, for example, that the powder which is in the second container by introducing the gas into a fluid-like state ver is set, can exit over the upper limit of the second container and enter the first container. This can, for example, be a conveyance of the powder in a circuit, i. H. from the second container into the first container and from there through the powder line back into the second container, and thus lead to particularly good, in particular homogeneous, mixing of the powder or mixing of the two or more powder components.

A powder opening for dispensing the first and / or the second powder component is preferably provided on the lower boundary, for example a container bottom, of the second container. This makes it possible, for example, to Ren of the (mixed) powder to the additive manufacturing device or a Vorratsbe container to remove the powder present in the mixing device as completely as possible, ie in particular to empty the second container as completely as possible.

Furthermore, the mixing device preferably comprises at least one first closure device which is designed to close and / or release the dispensing opening of the first container. As an alternative or in addition, the mixing device preferably comprises at least one second closure device which is designed to close and / or release the powder opening of the second container.

The first and / or second closure device can be designed, for example, as a powder valve and / or as a pinch valve and / or as a cone valve. Further preferably, the first closure device and the second closure device are designed to close and / or release the respective dispensing opening or powder opening depending on an operating state of the respective other closure device and / or depending on a defined operating mode of the mixing device. An operating state refers in particular to a state in which the dispensing opening or powder opening is closed or released by the respective closure devices, i.e. H. is open. In particular, powder can emerge from the respective container through the dispensing opening or powder opening when the respective opening is released. Accordingly, it is not possible for powder to escape through the respective opening if it is closed by the respective closure device. More preferably, the first and / or second closure device is designed to set a flow of powder (powder volume flowing through it per unit of time) through it. With regard to the closure devices, at least one of the following operating states is preferably provided for the mixing device:

- A first state in which the dispensing opening of the first container is freege ben and the powder opening of the second container is closed;

- A second state in which the dispensing opening of the first container closed ver and the powder opening of the second container is released;

a third state in which the dispensing opening of the first container and the powder opening of the second container are both closed (first variant) or both are released (second variant). The operating states of the mixing device are preferably assigned to different operating modes of the mixing device. For example, a “filling” operating mode can be provided in which the first and / or second powder component is supplied to the first and / or second container, ie the container (s) is / are filled. In this operating mode, the dispensing opening of the first container is preferably closed so that no powder emerges through it. The powder opening of the second container can optionally be opened, ie released, in order to permit powder exchange between the second and the first container, or it can also be closed. This corresponds to the above second operating state or the above first variant of the third operating state.

Furthermore, for example, a “mixing” operating mode of the mixing device can be provided in which the first and second powder components are mixed with one another. This is preferably done with the above-described conveyance of the powder in a circuit. In this operating mode, the output opening of the first container is preferably released and the powder opening of the second container is closed, corresponding to the above first operating state.

Furthermore, for example, a "conveying" operating mode of the mixing device can be provided in which the first and / or second powder component or the powder mixture is supplied to the additive Fierstellvorrichtung and / or a storage container. In this operating mode, both the dispensing opening and the powder opening are preferably released in order, for example, to enable the mixing device to be emptied as completely as possible. This corresponds to the above second variant of the third operating state.

Overall, the closure devices thus enable different processes to be carried out in or by means of the mixing device, for example.

A lower area of the first container, in particular its lower boundary, and / or the lower area of the second container, in particular its lower boundary, is or are preferably funnel-shaped at least in sections. educated. In this way, for example, dispensing the first and / or second powder component through the dispensing opening of the first container or the powder opening of the second container can be simplified and / or the powder can essentially be completely removed from the respective container. In particular, the funnel-shaped configuration can, for example, prevent poorly mixed areas from forming in the respective container.

A lower region of the first container, in particular the discharge opening, can preferably be connected to a conveyor module or is connected to it. The conveyor module can in particular comprise a pump, preferably a pneumatic powder pump, for conveying the first and / or second powder component. The connection of the dispensing opening to the delivery module can in particular mean a connection by means of the powder line. The pump is preferably designed for stoßwei sen conveyance of the powder. Alternatively, the pump can also be designed for continuous delivery of the powder. As an alternative to the integral provision of a conveyor module with the mixing device, it can also be provided separately from the mixing device, i. H. as an external conveyor module. For example, the conveyor module can be part of a docking station of the Fierstellvor direction, wherein the docking station for receiving the mixing device is ausgebil det.

At least one deflection element is preferably provided on the second container, which essentially extends from a container wall and / or the upper boundary of the second container in the direction of at least one nearest wall of the first container. More preferably, the deflecting element is inclined starting from the container wall or the upper boundary of the second container in the direction of the lower boundary of the first container and / or in the direction of the output opening of the first container. The deflecting element can, for example, cause the powder fluidized in the second container and exiting it to flow more evenly, in particular by deflecting the powder exiting the second container in the direction of the wall of the first container, which can improve the mixing of the powders, for example. In particular the latter can be counteracted by providing the deflecting element, a core flow of the powder being conveyed within the first and / or second container. The deflecting element preferably extends over substantially the entire circumference of the second container. This means that the deflecting element surrounds the second container essentially without any gaps in a section plane, in particular a horizontal section plane.

The first and / or second container can preferably be filled manually and / or partially automatically and / or automatically, i.e. it can be filled manually and / or partially automatically and / or automatically, in particular via the powder line. For this purpose, the powder line introduced into the second container can have, for example, a filling opening outside the container, via which the first and / or second powder component is supplied, for example from an external powder supply, or the powder line itself can be connected or connected to such an external powder supply , or a separately provided feed line can be led into the first and / or second container or, for example, connected to the powder line via a (powder) valve. In the case of a (partially) automatic filling of the first and / or second container, sensors for detecting a powder level in the respective container are preferably provided, for example to determine a defined powder quantity or level in the respective container and / or a defined mixing ratio of the powder components to be able to ensure. Alternatively or additionally, the container (s) can be filled, in particular manually, by opening the container lid of the first container and the powder level can be checked, for example, through a viewing window in the first and / or second container. The filling described here preferably corresponds to the "Filling" operating mode of the mixing device described above.

Alternatively or additionally, the powder line is preferably connected to an extraction line for removing the powder mixture or the first and / or second powder component from the mixing device. The extraction line can in particular be led into the additive Fierstellvorrichtung into, for example to a storage container for receiving the powdery building material, which in the Manufacture of a three-dimensional object is used. The extraction line, for example a pipeline, can be connected to the powder line of the mixing device, for example via a valve. Alternatively, the removal line can be connected directly to the dispensing opening of the first container, for example. A process of removing the powder mixture from the mixing device is preferably an above-described "conveying" operating mode of the mixing device.

The mixing device preferably further comprises a moistening device for moistening the first and / or second powder component in the powder line. The moistening device can, for example, comprise a container with a liquid in which an atomizer is located, and a powder container in which the powder to be moistened is located, i. H. which is in connection with the powder line. For example, a fluidizing plate through which a gas is introduced into the powder is arranged in the powder container. The gas is preferably conducted in a circuit, where it is humidified when passing through the container comprising the liquid, d. H. the moisture content of the gas is increased, and when it is passed through the powder container, this moisture is released back into the powder. A filter system for cleaning powder particles from the gas is preferably also provided in the circuit in which the gas is passed.

As an alternative or in addition to the provision of a humidifying device, the gas which is introduced into the second container through the at least one fluidization zone can have a high moisture content and thus serve to humidify the powder or the second container of the mixing device can be used as one described above Be formed powder container of a humidifier. By moistening the powder, for example, discharge and / or electrostatic charging of small powder particles during the mixing and conveying of the powder components can be prevented or at least reduced.

The mixing device is preferably movable, in particular displaceable, ausgebil det. This makes it possible, for example, to provide powder mixtures for various additive manufacturing devices by means of the mixing device, since the Mixing device can be brought to the respective manufacturing device in a simple manner.

An additive manufacturing device according to the invention is used to manufacture a three-dimensional object by selectively solidifying a build-up material in layers. The building material comprises a powder mixture provided by a mixing device described above. As an alternative or in addition, the manufacturing device has and / or is connected to a mixing device described above. The above-described effects of the mixing device can therefore also be achieved, for example, when the powder mixture is used in an additive manufacturing device or in an additive manufacturing process.

A method according to the invention is used to produce a powder mixture from a first powder component and at least one second powder component in a mixing device. In the method, the first and / or the second powder component is or is by one, i. H. received in a, first container, wherein a dispensing opening for dispensing the first and / or second powder component is provided at a lower limit of the first container, and the first and / or the second powder component is or is through a, d. H. accommodated in a second container, the second container being designed to be open at least in sections towards an upper side. The second container has, in particular in a lower container area, at least one first fluidization zone for introducing a gas into the second container, and the mixing device further comprises a powder line which can be or is connected to the dispensing opening of the first container and into the second container can be introduced or is introduced. Thus, for example, a method for producing a powder mixture is provided with which the same effects can be achieved as in the mixing device described above. It should be noted here again that the method can also be carried out with more than two powder components.

The method preferably comprises at least one of the following steps, preferably all of the following steps: a) introducing a gas through the first fluidization zone into the second container and / or through a second fluidization zone into the first container; b) manual and / or semi-automatic and / or automatic filling of the first and / or second powder component into the first and / or second container; c) mixing the first and second powder components from the first and / or second container, in particular in combination with step a); d) Diverting the first and / or second powder component through the output opening of the first container from the first container via the powder line into the additive Fierstellvorrichtung and / or a storage container, in particular in combination with step a).

Step a) is preferably omitted when the first and / or second container is filled manually.

The introduction of a gas through the first and / or second fluidization zone in step a) is preferably carried out at least temporarily. However, it is also possible that no gas is introduced at least temporarily through at least one of the two fluidizing zones.

The filling of the first and / or second powder component (step b) can be carried out separately for each powder component. Alternatively, the two powder components can also be filled in simultaneously or together, for example in a pre-mixed state that does not correspond to the degree of mixing to be achieved by the mixing device. The filling can take place, for example, as described above with reference to the mixing device, by supplying the first and / or second powder component from an external powder supply. Step b) preferably corresponds to the "filling" operating mode of the mixing device described above.

When mixing the first and second powder components in step c), the powder, ie the first and / or second powder component, is preferably in a cycle promoted as described above. Preferably, step c) corresponds to the above-described "Mixing" operating mode of the mixing device. Preferably, step c) is carried out until a predetermined degree of mixing of the first and second powder components is reached and / or during a predetermined period of time. Step d) preferably corresponds to the "conveying" operating mode of the mixing device described above.

Further features and usefulnesses of the invention emerge from the description of exemplary embodiments with reference to the accompanying drawings.

Fig. 1 is a schematic, partially sectioned view of a device for generative Fierstellen a three-dimensional object with a mixing device according to an embodiment of the present invention.

Fig. 2 is a schematic, sectional view of the mixer shown in Fig. 1 th.

FIG. 3 is a schematic view of a lower region of an inner container of the mixing device shown in FIG. 2.

4a to 4c are schematic views of the mixing device shown in FIGS. 2 and 3 in a first, second and third operating state.

Fig. 5 shows schematically steps of a method according to the invention for producing a powder mixture using the mixing device shown in Figures 2 to 4c.

In the following, an embodiment of an additive manufacturing device with a mixing device according to the invention is described with reference to FIG. 1. The device shown in FIG. 1 is designed purely by way of example as a laser sintering or laser melting device 1. To build up an object 2, it contains a process chamber 3 with a chamber wall 4. In the process chamber 3, an upwardly open container 5 with a container wall 6 is arranged. A working plane 7 is defined by the upper opening of the container 5, the area of the working plane 7 lying within the opening, which can be used to build the object 2, is referred to as construction field 8.

In the container 5 is a movable in a vertical direction V carrier 10 is arranged on which a base plate 11 is attached, which closes the container 5 down and thus forms the bottom. Optionally, a construction platform 12 is on the base plate 11, the construction platform 12 or the base plate 11 serving as a construction base on which the object 2 is built. In Fig. 1 the object 2 to be formed in the container 5 on the construction platform 12 is shown below the working plane 7 in an intermediate position with several solidified layers, surrounded by building material 13 that remained unsolidified.

The laser sintering device 1 also contains a storage container 14 for a powdery building material 15 that can be solidified by electromagnetic radiation Fig. 2 and 3 will be described in more detail ben. In the embodiment of the laser sintering device 1 shown in FIG. 1, the mixing device 18 is provided outside the process chamber 3; however, it can also be provided at least partially inside the process chamber 3. The mixing device 18 is connected to the storage container 14 via a withdrawal line 19, for example a pipe line, in order to supply the storage container 14 with pulveriform building material 15 from the mixing device 18. The mixing device 18 can be at least partially formed integrally with the manufacturing device 1, i. H. be provided in this, or be ausgebil det separately from the laser sintering device 1, d. H. be provided externally from this.

Various types of powder, in particular mixed powder, can be used as the building material, in particular metal powder, plastic powder, ceramic powder, sand or filled powder. Instead of powder, other suitable ones can also be used Materials are used as building material which contain at least one powder mixture provided by the mixing device.

The laser sintering device 1 further includes a in a horizontal direction H be movable coater 16 for applying the building material 15 within the construction field 8. Preferably, the coater 16 extends transversely to its direction of movement over the entire area to be coated. Optionally, a radiant heater 17 is arranged in the process chamber 3 for heating the applied building material 15.

The laser sintering device 1 also contains an exposure device 20 with a laser 21 which generates a laser beam 22 which is deflected via a deflection device 23 and through a focusing device 24 via a coupling window 25 which is attached to the top of the process chamber 3 in the chamber wall 4, is focused on the working level 7.

The laser sintering device 1 also contains a control unit 29, via which the individual components of the device 1 are controlled in a coordinated manner for carrying out the construction process. Alternatively, the control unit can also be attached partially or entirely outside the device. The control unit can contain a CPU, the operation of which is controlled by a computer program (software). The computer program can be stored separately from the device on a storage medium from which it can be loaded into the device, in particular into the control unit.

During operation, powdery building material 15 is fed from the mixing container 18 to the storage container 14 via the removal line 19. The powdery building material 15 is mixed beforehand in the mixing container 18, preferably mixed from two or more different powder components. The mixing of the pulveriform build-up material and its supply to the storage container 14 is described in more detail below with reference to FIGS. 4a-c and FIG. Then, to apply a layer of powder, the carrier 10 is lowered by a height that corresponds to the desired layer thickness and the coater 16 moves to the storage container 14 and takes from it a sufficient amount of the building material 15 to apply a layer. Then he drives over the construction field 8, there applies powdery construction material 15 to the construction base or an already existing powder layer and pulls it out to form a powder layer. Optionally, the powdery building material 15 is heated to a working temperature by means of a radiant heater 17. The cross section of the object 2 to be produced is then scanned by the laser beam 22, so that the powdery build-up material 15 is solidified at the points which correspond to the cross section of the object 2 to be produced. These steps are repeated until the object 2 is finished and can be removed from the process chamber 3.

The mixing device 18 is described in more detail below with reference to FIGS. 2 and 3. The mixing device 18 comprises, for receiving at least one first and / or second powder component, a first container in the form of an outer container 30 and a second container in the form of an inner container 40, which is inside the outer container 30, i. H. in the interior of which is arranged. The outer container can be designed to be movable, for example attached to or on a traversing device 35 with rollers, wheels, rails or the like.

The outer container 30 is delimited laterally by a container wall 31, towards its top it is delimited by a container lid 32 and towards its underside by a lower delimitation in the form of a container bottom 33 Position closes the outer container 30 in a powder-tight manner towards its upper side and, in an open position, at least partially, preferably completely, releases or opens the outer container 30 towards its upper side. The container bottom 33 of the outer container 30 is preferably funnel-shaped in front of and has a dispensing opening 34 for dispensing the first and / or second powder component.

The inner container 40 is delimited laterally by a container wall 41 and towards its underside by a lower delimitation in the form of a container bottom 42 limited. The container bottom 42 of the inner container 40 is preferably funnel-shaped and has a powder opening 43 for dispensing the first and / or second powder component. The inner container 40 is designed to be at least partially, preferably completely, open towards its upper side and has an upper delimitation in the form of a container edge 44 on its upper side. The inner container 40 extends over a height h between its lowest point, the Pul opening 43 in FIG. 2, and its container edge 44.

The inner container 40 is provided in essentially all spatial directions from the outer container 30 at a distance therein, d. H. the two container walls 31, 41, the two container bottoms 33, 42 and the two upper boundaries (i.e. the container lid 32 and the container rim 44) of the two containers 30, 40 are each spaced from one another. The inner container 40 is preferably provided essentially centrally in the outer container 30.

On the container wall 41 of the inner container 40, preferably on the edge 44 of the container, a deflection element in the form of a deflector plate 45 is provided. The baffle 45 is preferably arranged without a gap on the container wall 41 and extends outwardly from a first end 45a at or near the container wall 41 to a second end 45b, i. H. in the direction of the container wall 31 of the outer container 30. In the vertical direction, the first end 45a of the deflector plate is provided above the second end 45b, so that the deflector plate 45 is inclined downward, ie in the direction of the container bottom 33 or the discharge opening 34 of the outer container 30 is. The second end 45b of the baffle 45 is preferably seen at a distance from the container wall 31 of the outer container 30 so that a gap 46 is provided between the container wall 31 of the outer container 30 and the deflector 45. This gap 46 is dimensioned in such a way that the first and / or second powder component can pass through. Preferably, he extends the deflection element 45 over the entire circumference of the inner container (not shown in Fig. 2).

The container bottom 42 of the inner container 40 further comprises a fluidization zone 47. As can best be seen from FIG. 3, the fluidization zone 47 is through a Gas inlet element 48, for example a perforated plate or a porous plate, is formed, which is provided at a distance from the container bottom 42. A cavity 48a is formed between the gas guide element 48 and the container bottom 42 and is in gas-conducting connection with a gas supply line 49. The gas inlet element 48 is designed or the holes of the perforated plate or the pores of the porous plate are dimensioned such that gas introduced through the gas supply line 49 into the cavity 48a through the gas inlet element 48 or the holes in the perforated plate or the pores of the porous plate can get into the inner container 40, but no pulverför Miges construction material (ie the first and second powder components) can escape from the inner container 40 through the gas inlet element. The fluidization zone 47 can extend over the entire container bottom 42 of the inner container 42 or only be formed on it in sections. The gas supply line 49 is preferably in connection with a gas reservoir not shown in detail in the figures. The gas reservoir can in particular be seen outside of the outer container 30 and the gas feed line 49 can for this purpose, for example, be guided through the container wall 31 of the outer container 30 to the inner container 30.

The mixing device 18 further comprises a first closure device 61 which is designed to optionally close or release the dispensing opening 34 of the outer container 30. A second closure device 62 is also provided, which is designed to selectively close or release the powder opening 43 of the inner container 40. The closure devices 61, 62 can be designed as valves, for example. The closure devices 61, 62 can be manually operated by a user, but preferably they can be operated automatically, in particular by a control unit of the mixing device (not shown in the figures) or by the control unit of the laser sintering device 1 (see Fig.

Fig. 1) controllable. In FIGS. 2 and 3, the closure devices 61, 62 are shown in a closed state in which they close the dispensing opening 34 and the powder opening 43, respectively.

In a plan view from above (not shown in the figures), a geometric shape of the outer container 30 can be, for example, rectangular, square or round or any other desired, preferably regular, geometric shape aufwei sen. In a plan view from above (not shown in the figures), the inner container 40 can likewise have, for example, a rectangular, square or round geometrical shape or any other desired, preferably regular, geometrical shape. In a plan view from above, the inner container 40 preferably has the same geometric shape as the outer container 30, but on a smaller scale.

As shown in Fig. 2, the container edge 44 of the inner container 40 is provided spaced from the container lid 32 when the container lid 32 closes the outer container 30 to the top thereof. Next, the container wall 41 of the inner container 40 is provided at a distance from the container wall 31 of the outer container 30 and the container bottom 42 of the inner container 40 is spaced from the container bottom 33 of the outer container 30. The inner container 40 is preferably provided essentially centrally in the outer container 30.

The mixing device 18 further comprises a powder line 50 formed, for example, as a pipeline, which connects to the dispensing opening 34 of the outer container 30 in order to discharge the first and / or second powder component from the outer container 30. The powder line 50 is guided outside of the outer container 30 to its loading container lid 32 and through the container lid 32 into the inner container 40. The powder line 50 is preferably led into a lower region of the inner container 40, in particular into a lower half, more preferably a lower third of the inner container 40 with regard to its fleas h.

A pump 51, in particular a pneumatic powder pump, is provided in or on the powder line 50 in order to convey powder in the powder line 50. The pump 51 can be designed for intermittent or continuous delivery of the powder in the Pulverlei device 50. The pump can be designed as a component of the mixing device 18, as shown in FIG. 2, or it can be provided separately from the mixing device 18 as an external pump, for example as a component of a delivery module. Furthermore, the powder line 50 is connected to the removal line 19 via a valve 52 in order to enable powder to be supplied from the mixing device 18 to the storage container 14 (see FIG. 1). The valve 52 is designed to feed powder dispensed through the dispensing opening 34 of the outer container 30, ie the first and / or second powder component, either through the powder line 50 to the inner container 40 of the mixing device 18 or through the removal line 19 to the storage container 14 of the manufacturing device 1 feed. For example, the valve 52 can be designed as a directional valve, in particular as a 3-2 -way valve.

Furthermore, a humidifying device 53 is optionally available in the powder line 50 for humidifying the powder conveyed through the powder line 50, i. H. to increase the sen moisture content. As an alternative or in addition to the humidification device 53, the gas passed through the fluidization zone 47 into the inner container 40 can be humidified.

The closure devices 61, 62 can be brought into three different operating states, preferably as a function of one another, which are shown in FIGS. 4a, 4b and 4c. Fig.

4a shows a first operating state in which the dispensing opening 34 of the outer container 30 is closed by the first closure device 61 and the powder opening 43 of the inner container 40 is closed by the second closure device 62. In this first operating state, essentially no powder can get from the inner container 40 through the powder opening 43 into the outer container 30.

Likewise, essentially no powder can get from the outer container 30 through the dispensing opening 34 into the powder line 50. In this first operating state, the mixing device can, for example, be operated in a “filling” operating mode (see below).

4b shows a second operating state in which the powder opening 43 of the inner container 40 is closed by the second closure device 62 and the output opening 34 of the outer container 30 is released, i.e. not closed by the first closure device 61. In this second operating state, powder can be transferred from the outer container 30 through the dispensing opening 34 into the powder line 50. long, but essentially no powder can get through the powder opening 43 from the inner container 40 into the outer container 30. In this second operating state, the mixing device can be operated, for example, in a “mixing” operating mode (see below).

Fig. 4c shows a third operating state in which both the powder opening 43 of the inner container 40 and the output opening 34 of the outer container 30 is ben freege. In this third operating state, powder can pass from the inner container 40 through the powder opening 43 into the outer container 30 and from the outer container 30 through the discharge opening 34 into the powder line 50. In this third operating state, the mixing device can, for example, be operated in a "conveying" operating mode (see below).

The operation of the mixing device 18 is described below with reference to FIGS. 4a-4c and FIG. In a first step S1, which is also referred to as a "filling" operating mode of the mixing device 18, the mixing device is supplied with a first powder component and / or a second powder component, and optionally further powder component (s). The first and second powder components preferably differ from one another in their chemical and / or physical properties. For example, in step S1 the first powder component can be fed to the inner container 40 and the second powder component to the outer container 30, but the two powder components can also be fed to the outer and / or inner container in a mixed manner. It is also possible that one of the two powder components is already present in the inner and / or outer container.

To fill in the powder components, for example, the container lid 32 of the outer container 30 can be opened and the first and / or second powder component can be manually fed to the outer and / or inner container by a user. Alternatively or additionally, the first and / or second powder component can be introduced into the inner container 40 through the powder line 50 and / or a further supply line not shown in the figures. The container lid is preferably used here 32 in its closed position and through the fluidization zone 47 of the inner container 40, gas is introduced in order to fluidize the powder supplied and thus to supply it to the outer container 30.

During the supply of the first and / or second powder component (step S1), the closure devices 61, 62 can be in the first operating state described above with reference to FIG. 4a. This can prevent powder from escaping through the powder opening 43 and the discharge opening 34. As an alternative to the first operating state shown in FIG. 4a, the powder opening 43 of the inner container 40 can also be released in order to enable the first and / or second powder component to pass from the inner container 40 through the powder opening 43 into the outer container 30. Here, too, the dispensing opening 34 is closed by the first closing device 61.

In a second step S2, which is also referred to as a “mixing” operating mode of the mixing device 18, the first powder component and the second powder component are mixed with one another in the mixing device 18. In this operating mode, the closure devices 61, 62 are provided in the second operating state described above with reference to FIG. 4b, and the pump 51 is active. In this operating mode, the valve 52 closes the extraction line 19 and releases the powder line 50 leading into the inner container 40, and gas is introduced into the inner container 40 through the fluidization zone 47.

By introducing the gas, the powder in the inner container 40 is placed in a fluid-like state and exits the container 40 from the inner container via the container edge 44 of the inner container. Through the deflector 45, the sloshing, fluidized powder is directed outwards, ie in the direction of the container wall 31 of the outer container 30, and passes through the gap 46 between the deflector 45 and the container wall 31 of the outer container 30 in the outer container in the direction of its container bottom 33, whereby there is a thorough mixing with the powder located in the outer container 30. The powder passes through the dispensing opening 34 into the powder line 50 and is conveyed through the powder line 50 by means of the pump 51 and fed back to the inner container 30. Optionally, the powder is in the powder line 50 is humidified by means of the humidifier 53 and / or in the Innenbehäl ter 40 by introducing a humidified gas.

This second step S2 is carried out until a predetermined degree of mixing of the two powder components is reached and / or is carried out during a predetermined period of time. By circulating the powder through the powder line 50 and the inner and outer container, a good mixing of the powder is achieved. H. mixing the two powder components, he aims.

Subsequently, in a third step S3, which is also referred to as a "conveying" operating mode of the mixing device 18, the powder components mixed with one another are transferred to the storage container 14 as powdery building material 15 (see FIG.

Fig. 1) supplied. In this operating mode, the closure devices 61, 62 are provided in the third operating state described above with reference to FIG. 4c, and the pump 51 is active. In this operating mode, the valve 52 releases the extraction line 19 and closes the powder line 50 leading into the inner container 40 the powder line 50, where it is fed to the Vorratsbe container 14 (see FIG. 1) via the removal line 19. In step S3, gas is preferably introduced into the inner container 40 through the fluidization zone 47. As a result, the powder can essentially be completely removed from the inner container 40 or the amount of powder remaining in the inner container 40 (residual powder) is reduced. This third step S3 is preferably carried out until a predetermined powder fill level is reached in the storage container 14 and / or the mixing device 18 and / or during a predetermined period of time.

The invention is not limited to the embodiment of a mixing device described above. Rather, modifications and developments are possible without deviating from the subject matter of the present invention. For example, the powder opening 43 of the inner container 40 and / or the discharge opening 34 of the outer container 30 do not have to be provided in the respective container bottom 42 or 33. For example, they can also be provided in a side area of the respective container, preferably they are provided in a lower area of the respective container. The container bottoms 33, 42 also do not have to be funnel-shaped; they can, for example, also be flat or have any other suitable shape. Likewise, the fluidization zone 47 shown in FIGS. 2 and 3 does not have to be formed in or on the container bottom 42 of the inner container 40. Alternatively or additionally, a fluidization zone can also be formed on or in another area of the inner container and / or the outer container, in particular a lower area of the respective container.

In the case of the laser sintering or laser melting device 1 described above, the storage container 14 can also be provided integrally with the coater 16 or the powdery build-up material can be fed directly to the coater 16 from the mixing device 18 via the removal line 19.

According to a further development of the mixing device 18 described above, a further fluidization zone (not shown in detail in the figures) for introducing a gas into the outer container 30 can be provided alternatively or in addition to the fluidization zone 47 for introducing a gas into the inner container 40. This can be designed analogously to the fluidization zone of the inner container 40, for example.

In the mixing apparatus described above, the inner container 40 (generally: a second container) is provided in the outer container 30 (generally: a first container). As an alternative to this embodiment, a first and a second container can also be spatially separated, for example next to one another, and the first and / or second powder component can be exchanged between the containers or conveyed in a circuit via corresponding structural elements, for example powder lines or pipes will. Even if the present invention has been described using a laser sintering or laser melting device, it is not limited to laser sintering or laser melting. It can be applied to any method for the generative production of a three-dimensional object by applying layers and selectively consolidating a building material which comprises at least one powder mixture.

The exposure device of the additive manufacturing device can, for example, one or more gas or solid-state lasers or any other type of laser such as laser diodes, in particular VCSEL (Vertical Cavity Surface Emitting Laser) or VECSEL (Vertical External Cavity Surface Emitting Laser), or a line of these La ser include. In general, any device can be used as the exposure device with which energy as wave or particle radiation can be applied selectively to a layer of the building material, for example another light source, an electron beam or any other energy or radiation source that is suitable To solidify building material. Instead of deflecting a beam, exposure with a movable line exposure unit can also be used. Also on selective mask sintering, in which an extended light source and a mask are used, or on high-speed sintering (HSS), in which a material is selectively applied to the building material that increases the radiation absorption at the corresponding points (absorption sintering ) or reduced (inhibition onssintern), and then unselectively exposed over a large area or with a movable line illuminator, the invention can be used.

Instead of introducing energy, the selective solidification of the applied build-up material can also take place by means of 3D printing, for example by applying an adhesive. In general, the invention relates to the additive manufacturing of an object by means of layer-by-layer application and selective solidification of a building material, regardless of the manner in which the building material is solidified. Instead of a powdery build-up material, another suitable build-up material, for example a pasty build-up material, can also be used, which contains at least one powder mixture provided by the mixing device described above.

Claims

1. Mixing device for producing a powder mixture from a first powder component and at least one second powder component for an additive Her adjusting device (1), in which a three-dimensional object (2) by layer-wise selective solidification of a building material (15) which comprises the powder mixture, can be produced, the mixing device (18) comprising: a first container (30) for receiving the first and / or the second powder component, with a dispensing opening (34) at a lower limit (33) of the first container (30) for dispensing the first and / or second powder component is provided, and a second container (40) for receiving the first and / or the second powder component, the second container (40) being at least partially open towards an upper side, the second container (40), in particular in a lower container area, at least one fluidization zone (47) for introducing a gas into d en second container and wherein the mixing device (18) further comprises a powder line (50) which connects to the dispensing opening (34) of the first container (30) and is led into the second container (40).

2. Mixing device according to claim 1, wherein the second container (40) is arranged within the first container (30).

3. Mixing device according to claim 2, wherein the first container (30) can be closed on an upper side by a container lid (32) and wherein the second container (40) is provided within the first container (30) so that an upper limit ( 44) of the second container (40) is spaced from the container lid (32) of the first container (30) and wherein the powder line (50) is preferably led through the container lid (32) of the first container into the second container.

4. Mixing device according to one of claims 1 to 3, wherein a powder opening (43) for dispensing the first and / or the second powder component is provided on a lower boundary (42) of the second container (40).

5. Mixing device according to one of the preceding claims, further comprising at least one first closure device (61) which is designed to close and / or release the dispensing opening (34) of the first container (30) and / or at least one second closure device (62), which is designed to close and / or open the powder opening (43) of the second container (40).

6. Mixing device according to claim 5, in which the first closure device (61) and the second closure device (62) are formed, the respective output opening (34) or powder opening (43) depending on an operating state of the respective other closure device and / or to close and / or release depending on a defined operating mode of the mixing device (18).

7. Mixing device according to claim 6, in which at least one of the following operating states is provided: a first state in which the dispensing opening (34) of the first container (30) is released and the powder opening (43) of the second container (40) is closed and / or a second state in which the dispensing opening (34) of the first container (30) is closed and the powder opening (43) of the second container (40) is exposed and / or a third state in which the dispensing opening (34) of the first container (30 ) and the powder opening (43) of the second container (40) are both closed or both released.

8. Mixing device according to one of claims 1 to 7, wherein a lower region of the first container (30), in particular its lower limit (33), and / or the lower region of the second container (40), in particular its lower limit tongue (42), is or are funnel-shaped at least in sections and where preferably a lower region of the first container (30), in particular the output opening (34), can be connected to a conveyor module.

9. Mixing device according to one of claims 1 to 8, wherein the second container (40) is provided in essentially all spatial directions from the first container (30) spaced in this, preferably is provided essentially in the center of the first container.

10. Mixing device according to one of claims 1 to 9, wherein on the second loading container (40) at least one deflection element (45) is provided, which we sentlichen from the upper limit (44) of the second container in the direction of at least one closest Wall (31) of the first container (30) extends and wherein the deflecting element (45) is preferably inclined starting from the upper limit (44) of the second container (40) in the direction of the lower limit (33) of the first container (30) .

11. Mixing device according to one of claims 1 to 10, wherein the first and / or second container can be filled manually and / or semi-automatically and / or automatically, in particular via the powder line (50), and / or wherein the powder line (50) is connected to a removal line (19) for removing the powder mixture from the mixing device (18).

12. Mixing device according to one of claims 1 to 11, further comprising a moistening device (53) for moistening the first and / or second powder component in the powder line (50).

13. Additive manufacturing device for manufacturing a three-dimensional object (2) by layer-wise selective solidification of a building material (15), wherein the building material comprises a powder mixture provided by a mixing device (18) according to one of claims 1 to 12 and / or wherein the manufacturing device (1 ) has a mixing device (18) according to one of claims 1 to 12 and / or is connected to it.

14. A method for producing a powder mixture from a first powder component and at least one second powder component in a mixing device (18), the first and / or the second powder component being received by a first container (30), with a lower boundary (33 ) the first Behäl age a dispensing opening (34) is provided for dispensing the first and / or second powder component, and the first and / or the second powder component is received by a second container (40), the second container towards an upper side is designed to be open at least in sections, the second container (40), in particular in a lower container area, having at least one first fluidization zone (47) for introducing a gas into the second container and wherein the mixing device (18) further includes a powder line (50 ) which can be connected to the dispensing opening (34) of the first container (30) and into the second container (40) is practicable.

15. The method according to claim 14, characterized by the following steps: a) introducing a gas through the first fluidization zone (47) into the second container (40) and / or through a second fluidization zone into the first container (30) and b) manually or and / or semi-automatic and / or automatic filling (S1) of the first and / or second powder component into the first and / or second container (30, 40), c) mixing (S2) of the first and second powder components from the first and / or second container (30, 40), d) discharging (S3) the first and / or second powder component through the dispensing opening (34) of the first container (30) from the first container (30) via the powder line (50) into the additive manufacturing device (1) and / or a storage container (14).