DE102020203627A1 - Device for powder removal and / or powder recovery in continuous additive manufacturing - Google Patents

Abstract

The invention relates to a device (20) for powder removal and / or powder recovery of a continuously operating additive manufacturing system. In systems of this type which produce components (16) based on a powder bed, the production process cannot be interrupted in order to remove the manufactured components (16) and to free them from unprocessed powder (14). This must therefore also be done continuously. The powder cake (12) is therefore guided from a production area onto a roller conveyor (22, 32), where the unprocessed powder (14) falls down between the rollers of the roller conveyor (22, 32) into a collecting container (24) and from there into a conveyor system (28) is directed. This conveyor system (28) then feeds the unprocessed powder (14) to a powder preparation facility or it can also feed it directly for reuse.

Description

The invention relates to a device for powder removal and / or powder recovery of a continuously operating additive manufacturing plant.

Powder management poses a particular challenge in a continuously operating additive manufacturing system, i.e. a powder bed-based manufacturing system. Since manufacturing is not interrupted, the powder must be fed in continuously. Unprocessed powder must also be continuously separated from the component and removed when the component is removed.

During production it can happen that the powder forms agglomerates due to thermal effects and is therefore difficult or impossible to convey. The powder can also have an unsuitable temperature in order to be optimally conveyed.

The separated and discharged powder should generally be reprocessed and added to the fresh powder in a percentage that depends on the material. The manufactured components, which can be of different sizes, must not block the preparation process or get into the conveyor system for the powder to be removed. It must therefore be ensured that different additively manufactured component geometries can be reliably separated from unprocessed powder and ideally conveyed to a removal point.

Solutions based on discontinuous additive manufacturing are primarily known from the prior art. The removal of unprocessed powder causes an interruption in production, which is undesirable in continuous production and regularly cannot be implemented. The powder is essentially blown out or sucked off, but the unprocessed powder cannot be completely discharged, in particular not from the area of undercuts and the like.

In some solutions, a fluid stream is used to create a fluidized bed in order to loosen up the unprocessed powder and then to be able to remove it more easily, but this requires, as in the aforementioned solutions, a limited, enclosed installation space in which the component is manufactured in order to be able to subsequently to be able to blow out, suck off and / or produce a fluidized bed.

The invention is therefore based on the object of proposing a device with which a separation of manufactured components and unprocessed powder can be achieved easily and reliably in continuous additive manufacturing, i.e. powder-bed-based manufacturing, without the manufacturing having to be interrupted.

The object is achieved with a device according to claim 1. Further preferred embodiments of the invention emerge from the other features mentioned in the subclaims.

A device according to the invention for powder removal and / or powder recovery of a continuously operating additive manufacturing system has a roller conveyor, which is arranged downstream of a manufacturing area of the continuously operating additive manufacturing system and on which a powder cake is conveyed, a collecting container open at the bottom with at least one inclined side wall for collecting at least the falling powder, which is arranged below the roller conveyor, and a conveyor system for transporting away the fallen powder.

Additive manufacturing is also known as additive manufacturing (AM), generative manufacturing, 3D printing or rapid technology and a comprehensive term for all manufacturing processes in which material is applied layer by layer in order to create three-dimensional objects, which are usually referred to below as Components are designated. Starting materials for additive manufacturing can be liquid or solid materials that are arranged in layers and formed into objects by physical or chemical hardening or melting processes. For this purpose, binders and / or energy rays are incorporated into the starting materials or applied to the starting materials in a predetermined geometry. A temperature treatment can also take place. At the end of the manufacturing process, an object or component has been produced that is surrounded by layers of unprocessed raw material. This is known as a powder cake. The object or the component must be removed from this or the loose material must be removed. This process is also known as unpacking. This can be followed by a (fine) cleaning. In the context of the invention, a powder is assumed as the starting material, the layers of the powder from which the component is carved out being referred to as the powder bed. Additive manufacturing in the sense of the invention is therefore powder-bed-based. A powder is to be understood as a usually dry, solid substance consisting of a large number of particles that can flow freely when shaken or tilted. The size of the particles depends on the application and can therefore form a powdery to a granular mixture, such as sand.

The device according to the invention provides for powder recovery and / or powder removal in a continuously operating additive manufacturing process. This is understood to mean manufacturing in which production takes place simultaneously with transport activities and without any interruption in time. The production or manufacturing processes are therefore carried out while materials, semi-finished products, components and the like are being conveyed. The production or manufacture is therefore essentially not interrupted at any point in time.

For this purpose, the device has a roller conveyor. This is also known as a roller conveyor or roller conveyor. A roller conveyor is a stationary system with a large number of rollers that can be used to convey components from one location to another.

The roller conveyor is arranged at the end of a production area of the continuously operating additive manufacturing system. The components produced during production, embedded in unprocessed powder and thus in their entirety as a powder cake, are conveyed to the roller conveyor at the end of the production area. This can be done, for example, by a conveyor belt or conveyor belt in the production area. While the powder cake is moved further on the roller conveyor, the unprocessed powder falls downward due to the force of gravity and at least partly also due to the vibrations introduced as a result of the type of movement. The component or components are thereby exposed.

A collecting container which is open at the bottom and has at least one inclined side wall is arranged below the roller conveyor. The inclination takes place in such a way that the cross-section of the collecting container becomes smaller towards the bottom. The collecting container should at least catch the falling powder, but it can also catch smaller components that fall between the rollers of the roller conveyor. If the falling powder hits the at least one inclined side wall, any agglomerations that may be present disintegrate and the powder can slide loosely downwards along the at least one inclined side wall. Depending on the selected height of fall, that is to say the distance between the roller conveyor and the point of impact on the at least one inclined side wall, the separating effect can be adjusted.

Both or all of the side walls of the collecting container are preferably inclined, so that a downwardly tapering cross section of the collecting container is established. The side walls are at least the two side walls of the collecting container running in the conveying direction of the roller conveyor, but this can also include the side walls of the end faces.

The collecting container expediently has the same length as the roller conveyor in order to collect falling powder over its entire length.

The collecting container is open at the bottom so that the collected powder can be fed to a conveyor system for transporting the fallen powder away. The conveying system is designed and set up to receive the fallen powder and convey it to a powder processing system and / or to feed it directly to a storage container of the powder for reuse.

This device according to the invention makes it possible for a powder cake to be moved continuously from the production area onto the roller conveyor, where it is continuously moved on, with the component and the unprocessed powder being separated at the same time. Production does not have to be interrupted to unpack the finished components and the powder can be quickly made available for reuse.

In a first preferred embodiment of the invention it is provided that the inclination of the at least one side wall of the collecting container corresponds at least to the angle of repose of the powder. The angle of repose, also known as the angle of friction, is the angle at which a granular material, in this case the powder, can be loaded without slipping or failing. If the angle is exceeded, the powder will slide off. If the collecting container has an angle that corresponds at least to the angle of repose, the loose powder can flow to the end of the collecting container and into the conveyor system. The two longitudinal side walls of the collecting container are advantageously inclined at such an angle, with particular advantage all side walls of the collecting container are inclined at such an angle.

As an alternative or in addition, the collecting container can be subjected to at least some of the vibrations. The device according to the invention has a suitable device for generating vibrations and transmitting them to at least one of the side walls of the collecting container, preferably to several or all of the side walls of the collecting container. This vibration can ensure the flow of the fallen powder and, depending on the intensity of the vibration, contribute to the disintegration of possible agglomerations.

It can also be provided that the collecting container can be at least partially temperature-controlled. The collecting container or at least parts of it are cooled or heated for this purpose, especially its side walls. This brings about a temperature control of the falling, unprocessed powder, so that residual heat can be extracted from it or it can be heated. By adjusting the temperature of the powder, the transport of the powder both through the collecting container and within the adjoining conveyor system can be further optimized.

In a further advantageous embodiment, the conveyor system for removing the fallen powder is designed with a screw conveyor, a conveyor belt, a pneumatic conveyor, a hydraulic pusher and / or a mechanical pusher.

A screw conveyor is a conveyor system for bulk goods and is based on the functional principle of the Archimedean screw. It is usually driven by a motor and allows the powder supplied to be transported away continuously. While the fallen powder is transported in a screw conveyor, the screw conveyor acts on the powder. This creates considerable forces, primarily shear forces, which may loosen any agglomerations in the powder that may still be present. Preferred diameters of the screw conveyor are in the range from 50 mm to 500 mm, the other components of the screw conveyor being appropriately dimensioned in a professional manner.

A conveyor belt, also called assembly line, conveyor belt, belt conveyor, belt conveyor or belt conveyor, is also a conveyor system with which bulk goods and thus the unprocessed powder can be continuously transported away. The advantages of conveyor belts are their efficiency when conveying bulk goods and their low wear.

Pneumatic conveying means the transport of bulk goods with gas by means of positive or negative pressure. The gas can be air, for example. In principle, the conveyance takes place through pipes or hoses, possibly also through fluid channels.

Hydraulic and mechanical slides are used when the following transport or conveying means are to be charged with a defined mass flow of a bulk material. The outlet opening in the direction of the following transport or conveying means is opened gradually or continuously in a controlled manner in order to prevent the flow of bulk material from shooting through.

In particular, when small components are to be manufactured and unpacked by means of the device according to the invention, it is important that these small components do not fall down between the rollers of the roller conveyor or at least do not get through the collecting container into the conveyor system, where they would otherwise interfere with the Conveying the powder or damage the system. A small component is a component produced by means of continuous additive manufacturing that would fall through between the rollers of the roller conveyor if measures were not taken to prevent this.

For this purpose, the roller diameter and / or the roller spacing of the roller conveyor can be selected in such a way that a disk formed during production, above which at least one small component is arranged, is to be conveyed. For this purpose, several layers of the powder can be processed during production in such a way that they form a disk on or above which the small component (s) are then produced in the powder bed. If the powder cake is then pushed from the production area onto the roller conveyor, the disk prevents the at least one small component located above it from passing between the rollers into the collecting container and thus the conveyor system. For this purpose, the roller diameter and / or the roller spacing should be dimensioned in such a way that the pane can be safely transported without tilting or tilting between the rollers or into the space between the rollers of the roller conveyor. The roller diameter and / or the roller spacing result from the dimensions of the pane to be manufactured, the dimensions of the pane being determined by manufacturing-related boundary conditions and economic considerations.

It can also be useful to arrange at least one grid in the collecting container. The at least one grid is intended to prevent the small components from falling through the collecting container into the subsequent conveyor system. In this way, it is also possible to sort the components according to size or at least in two size categories. Accordingly, the grid openings in a single grid are to be selected so that they are smaller than the smallest component to be manufactured. If there is more than one grid, the grid openings can be graded in size. The small components remain on the at least one grid and can be removed from this, for example through a flap. At the same time, any agglomerations of the powder that may still be present are loosened by the impact of the powder on the at least one grid.

Alternatively or additionally, at least one further roller conveyor can be arranged in the collecting container itself. This preferably has smaller roller diameters and distances than the roller conveyor above the collecting container, so that small components can also be collected by means of the at least one further roller conveyor and they cannot get into the subsequent conveyor system. As with a grid, small and large components are sorted by the (first) roller conveyor and the at least one further roller conveyor. The roll diameters and spacing are to be matched to the smallest component to be manufactured or the size classes to be achieved during sorting, as with a grid. A multi-level sorting of components of different sizes falling from the first roller conveyor can also take place in combination with at least one grid. The further roller conveyor also has the advantage that it can convey the collected components to an output location or a removal point, where they can be output or removed.

The at least one grid and / or the at least one further roller conveyor is advantageously arranged at an angle in the direction of a side wall of the collecting container. The at least one further roller conveyor and / or the at least one grid is therefore inclined in the direction of one of the side walls of the collecting container, that is to say rotated around a longitudinal axis at an angle. As a result, the components caught by the at least one further roller conveyor and / or the at least one grid can slide in the direction of the side wall and be collected there. The captured components can then be removed via a flap or another removal opening, preferably another closable removal opening.

It is also preferred if the roller conveyor and / or the at least one further roller conveyor have a drive, in particular a common drive. A drive that drives the rollers of a roller conveyor can move the objects on it further without additional external influences, such as the constant pushing in of powder cakes from continuous additive manufacturing or being pushed by an operator. A drive can be provided for each of the roller conveyors, but a single drive can also be provided which drives several or all of the roller belts. This would reduce the resources required and the installation space of the device.

With the device according to the invention for powder removal and / or powder recovery of a continuously operating additive manufacturing system, the manufacturing process can be continued uninterrupted. Here, unprocessed powder is separated from the finished components and fed to powder processing and / or directly to reuse. This can be done fully automatically. The device according to the invention provides a closed system from which no powder can escape. The production of particularly small components is also taken into account by means of suitable collecting solutions.

The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless stated otherwise in the individual case.

• 1 verschiedene Darstellungen einer beispielhaften Ausgestaltung der erfindungsgemäßen Vorrichtung,
• 2 und 3 weitere mögliche Ausgestaltungen der erfindungsgemäßen Vorrichtung.

The invention is explained below in exemplary embodiments with reference to the accompanying drawings. Show it:

• 1 various representations of an exemplary embodiment of the device according to the invention,
• 2 and 3 further possible configurations of the device according to the invention.

1 shows a schematic representation of a top view ( 1a) , a side view ( 1b) and a cut ( 1c ) of the device according to the invention in an exemplary embodiment. It is described below using all three sub-figures together.

In a manufacturing area 10 In a continuously operating additive manufacturing system, components are placed in a powder bed 16 made from unprocessed powder 14th are enclosed. The powder cake thus formed 12th is continuously from a conveyor belt of the production plant in the direction of the device according to the invention 20th and there on a driven roller conveyor 22nd pushed. The raw powder 14th loosens and falls between the rollers of the roller conveyor 22nd through to the bottom where there is a collection container 24 is caught. The components 16 exposed or unpacked and conveyed further in the direction of an extraction point (illustrated by an arrow).

The collecting container 24 is formed in the manner of a funnel, so it is open at the bottom and its side walls 26th form a downward tapering cross-section, so are inclined. The angle of inclination of the side walls 26th corresponds at least to the angle of repose of the powder used 14th . Hit the raw powder 14th on the inclined side walls 26th This ensures that it is carried away further downwards and does not remain lying.

When the powder hits 14th are also due to the existing height of fall between the powder cake 12th and the side walls 26th of the collecting container 24 possibly existing agglomerations of the powder 14th solved.

About the removal of the falling powder 14th can optimize the side walls 26th cooled or heated (not shown) to improve the flow behavior of the powder 14th to influence. It can also help remove excess residual heat from the powder 14th to dissipate. Alternatively or in addition, vibrations can act on the side walls 26th of the collecting container 24 can be applied (not shown) to remove the powder 14th to further promote.

That through the collecting container 24 powder discharged downwards 14th is in a conveyor system 28 guided, in this exemplary embodiment with a screw conveyor 30th is trained. By means of this funding system 28 becomes the powder 14th a powder preparation so that it can be used again afterwards. The powder 14th but can also be recycled directly if necessary.

But there are also components 16 can be made by the rollers of the roller conveyor 22nd fall through are in 2 two embodiments of the device according to the invention 20th in which these small components 16b are prevented from entering the conveyor system 28 reach. For this purpose, only the differences between the top views are shown below 2a and 2 B to 1a as well as the cut of the 2c to 1c explained.

In 2a is another roller conveyor 32 inside the collecting container 24 arranged. Its roller spacing and roller diameter are noticeably smaller than those of the first roller conveyor 22nd . Now becomes the powder cake 12th on the roller conveyor 22nd the device 20th pushed, with the unprocessed powder 14th solves, larger components 16a from the rollers of the roller conveyor 22nd held, smaller components 16b fall through onto the further roller conveyor 32 and are prevented by this from entering the conveyor system 28 to get.

The other roller conveyor 32 can have its own drive or the same drive as the roller conveyor 22nd be driven (not shown). The smaller components 16b can thus also be conveyed to an extraction point in the direction indicated by an arrow.

In an alternative embodiment of the 2 B is in the collecting container 24 a grid 34 arranged. It is from the schematic shown 2c it can be seen that both embodiments according to 2a and 2 B can have a similar or identical schematic structure. The grid openings of the grid 34 are sized so that the powder 14th can fall through, but the smaller components 16b are caught. For example, you can use removal openings in one or both side walls 26th of the collecting container 24 (not shown) can be removed.

3 shows a section of the device 20th with a sloping grille 34 or another inclined roller conveyor 32 in the collecting container 24 is arranged. The small components 16b caught thereby slide in the direction of a side wall 26th of the collecting container 24 where they are through a removal flap 36 can be removed through.

List of reference symbols

10

Manufacturing area

12th

Powder cake

14th

powder

16

Component

20th

contraption

22nd

Roller conveyor

24

Collecting container

26th

side walls

28

Conveyor system

30th

Screw conveyor

32

further roller conveyor

34

Grid

36

Removal flap

Claims (10)

Device (20) for powder removal and / or powder recovery in a continuously operating additive manufacturing system a roller conveyor (22) which is arranged downstream of a production area (10) of the continuously operating additive production system and on which a powder cake (12) is conveyed, a downwardly open collecting container (24) with at least one inclined side wall (26) for collecting at least the falling powder (14), which is arranged below the roller conveyor (22), and a conveyor system (28) for removing the fallen powder (14). Device (20) after Claim 1 , characterized in that the inclination of the at least one side wall (26) of the collecting container (24) corresponds at least to the angle of repose of the powder (14). Device (20) after Claim 1 or 2 , characterized in that the collecting container (24) is at least partially to be subjected to vibration. Device (20) according to one of the preceding claims, characterized in that the collecting container (24) can be at least partially temperature-controlled. Device (20) according to one of the preceding claims, characterized in that the conveyor system (28) is designed to remove the fallen powder (14) with a screw conveyor (30), a conveyor belt, a pneumatic conveyor, a hydraulic pusher and / or a mechanical pusher is. Device (20) according to one of the preceding claims, characterized in that the roller diameter and / or the roller spacing of the roller conveyor (22) is selected such that a disk formed during production, above which at least one smaller component (16) is arranged, is to be promoted. Device (20) according to one of the preceding claims, characterized in that at least one grid (34) is arranged in the collecting container (24). Device (20) according to one of the preceding claims, characterized in that at least one further roller conveyor (32) is arranged in the collecting container (24). Device (20) after Claim 7 or 8th , characterized in that the at least one grid (34) and / or the at least one further roller conveyor (32) is arranged at an angle in the direction of a side wall (26) of the collecting container (24). Device (20) according to one of the preceding claims, characterized in that the roller conveyor (22) and / or the at least one further roller conveyor (32) have a drive, in particular a common drive.

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