DE102011088158A1 - Secondary circuit for device for producing three-dimensional metal object used in beam fusion plant, has return line that is provided for recycling of powder from overflow container in main circuit of device - Google Patents

Abstract

The present invention relates to a secondary circuit (10) for a device (100) for producing three-dimensional metallic objects, in particular for a beam melting system, wherein at least one overflow container (20) for receiving excess powder from a construction space (120) of the device (100). and a return line (30) for returning powder from the weir tank (20) to a main circuit (110) of the apparatus (100).

Description

The present invention relates to a secondary circuit for a device for manufacturing three-dimensional metallic objects, to such an apparatus, and to a method for handling excess powder in a device in the production of three-dimensional metallic objects.

It is known that generative processes are used for the production of three-dimensional metallic objects. These are in particular processes to be understood in which the objects are produced in layers from powdered starting materials in a three-dimensional manner. This can be done for example by laser sintering or laser welding. Such methods are used in particular for the production of individual components, ie prototypes. However, such devices can also be used to manufacture in small batches components in small numbers. The known devices have in common that they have in their space a platform which is movable in height. An application of the corresponding base powder takes place in layers in layers, in order to produce the desired solid structure in the layer. The application of the layer can be carried out, for example, with the aid of a slider or a doctor blade which, from a starting point, applies the powdery base substance as a layer in the installation space. In order to be able to suck the unconsolidated parts of the powder again after the process, a powder suction hose is usually present in the main circuit, with the aid of which the loose powder is sucked off and returned to the circulation, so that the powder is again stored in a main tank can. From this main tank, the powder is in turn made available to the next manufacturing step.

Known devices and methods have the disadvantage that when applying a new layer with the help of the coater, so for example the squeegee or the slider, an excess of powder is formed. This excess of powder falls at least on one side of the space in an overflow container. For example, an overflow tank is out of the DE 10 2004 064 050 B4 known. Such overflow containers serve to ensure that only the installation space itself is provided with a powder layer, while excess powder leaves the installation space in the overflow container. In known devices, these overflow containers are manually emptied after some time. The DE 10 2004 064 050 describes a method in which from the overflow container, the material is pushed back directly into the space. The manual emptying of the overflow container has the disadvantage that there is a contact of the operating personnel with the powder. In addition, due to the compactness of the entire manufacturing plants such containers are usually made relatively small. This can lead to the overflow container being filled up and the process having to be stopped within one pass, ie during the production of, for example, a component by such a method. When the powder is pushed up from the overflow container directly into the installation space, there is a risk that impurities, densities and in particular agglomerates of different powder particle sizes are pushed up into the installation space, which in turn can lead to uncontrollable errors in the production of the three-dimensional metallic objects.

It is an object of the present invention to at least partially overcome the problems described above. In particular, it is an object of the present invention to provide a subcircuit for a device for producing three-dimensional metallic objects, such a device for producing three-dimensional objects and a method for handling excess powder in a device for the production of three-dimensional metallic objects, the In an inexpensive and simple way, the handling of the excess powder improved.

The above object is achieved by a secondary circuit with the features of claim 1, a device having the features of claim 9 and a method having the features of claim 12. Further features and details of the invention will become apparent from the dependent claims, the description and the drawings. In this case, features and details that are described in connection with the secondary circuit according to the invention, of course, also in connection with the inventive method and apparatus according to the invention and in each case vice versa, so that with respect to the disclosure of the individual aspects of the invention always reciprocal reference is or may be.

A secondary circuit according to the invention is suitable for a device for producing three-dimensional metallic objects, in particular for a beam melting system. An ancillary circuit according to the invention is thus to be used in particular for the so-called rapid manufacturing methods and only to a limited extent for so-called rapid prototyping methods. The produced three-dimensional metallic objects are preferably mechanically resilient, so that they can take over a mechanical function task not only in prototypes but also in loaded components.

A secondary circuit according to the invention is characterized in that it has at least one overflow container for receiving excess powder from the installation space of the device and a return line for the return of powder from the overflow container into a main circuit of the device. This secondary circuit thus has the possibility that the overflow tank is emptied stepwise or continuously automatically. The emptying of the overflow container takes place in an explicit manner, namely by the return of the powder in the main circuit of the device. By excluding a return directly into the installation space, all facilities that serve in the main circuit, in particular the storage, cleaning and transport of the powder, can also be used for the secondary circuit. Thus, a particularly cost-effective solution for the secondary circuit can be created. Thus, for example, a cyclone is provided in the main circuit, which generates a negative pressure for conveying the powder both in the main circuit and in the secondary circuit. Also, in the main circuit, a sieve and / or a filter may be provided which removes impurities or agglomerates from the powder or destroys these agglomerates. Thus, the overflow container can be guided directly or indirectly into a main tank, in which the non-guided powder can be mixed with newly added powder and kept for the process.

Another advantage is that with a secondary circuit according to the invention no handling of the powder in a manual way must be performed more. Rather, the return of the powder is done automatically, so that the contact with the powder for the operator can be reduced to a minimum. It is also advantageous that in a secondary circuit according to the invention, the overflow container can be made relatively small or even can be reduced in size. This is only possible if, in a method according to the invention, a stepwise or continuous recycling of the powder into the main circuit is provided. Thus, the compactness of the overall system of such a device can be further reduced.

The overflow tank is preferably about 5 liters. The thickness of a layer of the order with a coating device preferably corresponds to approximately 50 μm. In a secondary circuit according to the invention in particular powdered metals are used, for example aluminum, steel, stainless steel or tool steel. Of course, other powdered metals or alloys can be used. The method for the production of three-dimensional metallic objects is carried out in particular by laser devices, for example by laser sintering or laser melting. The laser is preferably in a power class of about 400 watts.

In a secondary circuit according to the invention, the volume flow in the secondary circuit for the powder can be about 1 l / s. Of course, not only one, but also several identical or different three-dimensional metallic objects can be produced in one step in the installation space of the device. By returning the powder by means of the return line is also ensured that the powder from the overflow tank is loosened. Thus, adhesions, bonds or agglomerates can be prevented or reduced.

It may be advantageous if at least one overflow pipe for the transfer of excess powder from the installation space of the device is provided in the overflow container in a secondary circuit according to the invention. Such an overflow pipe is designed in particular for the gravity feed of the powder in the overflow container. By providing the overflow pipe, the actual position of the overflow tank can be chosen even more freely. In other words, the overflow tube represents the powder-communicating connection between the installation space and the overflow container.

It may also be advantageous if, in a secondary circuit according to the invention, the at least one overflow pipe has a shut-off valve. This shut-off valve is in particular a shut-off valve against the pressing powder. Preferably, this shut-off valve is also designed to produce a gas-tightness or substantially gas-tightness. Since the extraction of the overflow container is achieved by the return line, in particular by a negative pressure in the overflow container, the suction of the overflow container can continue to be carried out even when the device is open, ie with the main flap open to the installation space by closing the shut-off valve. Another advantage of the shut-off valve is that in this way the secondary circuit is even easier inertizable. Since the powder is often used with particularly fine grain sizes, there is a risk of explosion. By inerting the return line, ie by reducing the oxygen content, the risk of explosion can be significantly reduced.

It may therefore be advantageous if at least one connection for the supply of inert gas is arranged downstream of the shut-off valve in a secondary circuit according to the invention in the flow direction. The connection for inert gas, for example, brings with it the possibility for the introduction of nitrogen, argon or other inert gases with it. By the arrangement after the shut-off valve, an inert suction can be carried out even after the opening of the main door to the installation space on. Inert gas can be introduced both in the pressure vessel, as well as in the overflow pipe.

It is also advantageous if, in a secondary circuit according to the invention, the overflow container has at least one fill level sensor. The fill level sensor can be designed to be capacitive, for example. Basically, qualitative as well as quantitative sensor systems can be used for the level sensor. In qualitative sensors, these are preferably arranged in a larger number and at different heights of the overflow container. The level sensors are preferably connected to a control or regulating device and serve to control the suction in the secondary circuit. In particular, three filling situations are to be distinguished, which can be perceived by such a level sensor. These are the situations "empty", "medium" and "full". If the overflow tank is empty, the return of the secondary circuit is stopped. If the overflow tank is not empty, in particular half full, ie "medium", the return is started and the overflow tank emptied via the return line. If, despite the recycling process of the powder via the return line, the overflow container has run full, the process must be stopped. However, this will happen in significantly fewer situations than is the case with known devices which have only manual or no return of the powder from the overflow container. A targeted over-dimensioning of the powder entrained during powder application moreover ensures a stable coating. The excess powder is selectively conveyed into the powder overflow and allows the layer application of each subsequent layer with powder from the main tank.

It may also be advantageous if, in a secondary circuit according to the invention, the return line has a T-valve for connection to the main circuit at its end facing away from the overflow container. In addition to the otherwise possible embodiments by means of individual valves in the return line or in the main circuit, a T-valve can represent a particularly simple and cost-effective solution. In particular, the two circuits can be coupled and decoupled with each other in a particularly simple and cost-effective manner. So it is possible that the main circuit together with the secondary circuit, as well as the two circuits are each operated separately from each other. The same is of course conceivable with two separate shut-off valves in the two circuits.

It is also useful if at least the return line can be made inert in a secondary circuit according to the invention. Inertization can be carried out in particular with an inert gas, for example by nitrogen or argon. Thus, the risk of explosion, as already explained above, be significantly reduced.

It is also advantageous if, in a secondary circuit according to the invention, the return line is designed as a steel tube for conveying powder. The provision of a steel pipe allows a particularly inexpensive and simple embodiment for connection to an existing device. In addition, the steel pipe has sufficient mechanical stability to promote powder therein. Also, the wear on the inner walls of the steel tube can be reduced to an acceptable level during powder delivery. In particular, the training is to be distinguished with a steel pipe of plastic pipes, as they can be used for example in the field of so-called rapid prototyping method.

Another object of the present invention is a device for the production of a three-dimensional metallic object, comprising a main circuit for metallic powder with a main tank, a cyclone and / or a sieve. Furthermore, a construction space is provided in which the object is produced by irradiation of the metallic powder made available from the main tank. Under irradiation is preferably an energy input by radiation to understand. This energy input is in particular a light energy input, preferably a laser beam with preferably up to 400 watts of power. A device according to the invention is characterized by a secondary circuit according to the present invention. As already described in the introduction of this application, in a device according to the invention the individual layers are applied during the production of the three-dimensional metallic object with the aid of a slider or a doctor blade. In this case, excess powder is transferred in accordance with the invention in an overflow container and made available from there by the secondary circuit according to the invention the main circuit again. Accordingly, a device according to the invention brings about the same advantages as have been explained in detail with reference to a secondary circuit according to the invention.

A device according to the invention can advantageously be further developed such that the main circuit has a powder suction hose for the extraction of powder from the installation space. In particular, this is used at the end of the manufacturing process. He serves that the excess, so still powdery, powder can be sucked off after the manufacturing process. Of course, it is possible that the main suction takes place only through the overflow container and then only the remaining powder residues, in particular small agglomerates can be eliminated by the powder suction hose. Preferably, the powder suction hose forms part of the main circuit so that the powder can be returned directly or indirectly via the cyclone and / or the screen into the main tank.

It may also be advantageous if, in a device according to the invention, the secondary circuit is connected in the direction of flow to the installation space and in front of the cyclone and / or the screen to the main circuit. As a result, the return of the powder into the main circuit passes at a point which allows the further treatment and in particular the cleaning of the recirculated powder in the main circuit. In particular, this ensures the quality of the recycled powder in the desired manner. Thus, a substantially continuous cycle can be provided which minimizes the loss of unused powder.

Another object of the present invention is a method for handling excess powder in a device for the production of three-dimensional metallic objects. A method according to the invention is characterized in that the excess powder is collected in an overflow container and returned from the overflow container via a return line to a main circuit of the device. In particular, the overflow container and the return line form a secondary circuit according to the invention. An inventive method is used for direct return of the excess powder from the overflow tank into the main circuit. The device is preferably designed in accordance with the invention. Accordingly, a method according to the invention entails the same advantages as have been explained in detail with reference to a device according to the invention or with reference to a secondary circuit according to the invention.

The present invention will be explained in more detail with reference to the accompanying drawing figures. The terms "left", "right", "top" and "bottom" used herein refer to an alignment of the drawing figures with normally readable reference numerals. They show schematically:

1 a flow diagram of a device according to the prior art and

2 a flow diagram representation according to the present invention.

In 1 is basically a device 100 for the production of three-dimensional metallic objects. It has a central processing chamber 170 with a space 120 on. In the process chamber 170 is a coater 160 , for example in the form of a squeegee, provided with a main tank 130 in powder-communicating compound. From the main tank 130 Powder becomes the coater 160 fed, which in turn within the process chamber 170 a layer in the installation space 120 applying. After the application of this layer, the desired layer sections are exposed, that is, for example, treated with a laser, so that by melting and / or sintering this layer solidified at the desired locations and the next component layer can be applied.

During application with the help of the coater 160 There is an excess of powder, which is in an overflow container 20 must be introduced. From the overflow tank 20 Either the powder is discarded manually as waste or returned to the main tank 130 returned. In addition, in the process room 170 a connection for the main circuit 110 provided, which a return conveyance of the remaining powder after completion of the method for producing the three-dimensional metallic objects via a sieve 150 and a cyclone 140 allows.

In 2 is an embodiment of a method according to the invention or a device according to the invention 100 with a secondary circuit according to the invention 10 shown. The reference numerals designate the same components as in FIG 1 , Accordingly, only the differences from the device according to the prior art will be explained in more detail.

The device 100 according to 2 has a secondary circuit 10 on, which with an overflow container 20 and a return line 30 Is provided. The overflow tank 20 is over two overflow pipes 22 with the process room 170 the device 100 connected. About these overflow pipes 22 can during the coating process applied excess powder in the overflow tank 20 reach. About the return line 30 can from the overflow tank 20 the stored powder in the main circuit 110 the device 100 be supplied. The supply takes place via a T-valve 32 , The feed takes place in a place which is the process room 170 So also the space 120 , downstream in the flow direction and the sieve 150 and with it also the cyclone 140 is upstream.

To the suction from the overflow tank 20 ensure and control, respectively control, are level sensors 26 on the overflow tank 20 intended. These designate a lower, a middle and an upper level limit, wherein in the case of an empty overflow container, the return line through the return line 30 stopped, with half full overflow tank 20 the return via the return line 30 started and with full overflow tank 20 the entire manufacturing process by the manufacturing device 100 is stopped.

The return line 30 and in particular also the overflow container 20 as well as the overflow pipes 22 are preferably inertizable. For this is a, not shown, connection for inert gas available. This is preferably in the overflow pipes 22 and / or the overflow tank 20 arranged. The arrangement is preferably carried downstream in the flow direction behind two shut-off valves 24 the overflow pipes 22 , Will the process room 170 open, the shut-off valves can 24 be closed, so that subsequently continue an inerting of the secondary circuit 10 can take place. Also, the promotion can be continued with the help of negative pressure, if in the process room 170 an opened main flap is present.

The above explanations of the embodiments describe the present invention by way of example only. Of course, individual features of the embodiments, if technically feasible, can be combined freely with one another, without departing from the scope of the present invention.

LIST OF REFERENCE NUMBERS

10

Secondary circuit

20

Overflow tank

22

Overflow pipe

24

shut-off valve

26

level sensor

30

Return line

32

T-valve

100

Device for the production of three-dimensional metallic objects

110

Main circuit

112

Powder suction hose

120

space

130

main tank

140

cyclone

150

scree

160

coaters

170

process chamber

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004064050 B4 [0003]
• DE 102004064050 [0003]

Claims (13)

Secondary circuit ( 10 ) for a device ( 100 ) for producing three-dimensional metallic objects, in particular for a jet melting plant, characterized by at least one overflow container ( 20 ) for taking up excess powder from a construction space ( 120 ) of the device ( 100 ) and a return line ( 30 ) for the return of powder from the overflow tank ( 20 ) into a main circuit ( 110 ) of the device ( 100 ). Secondary circuit ( 10 ) according to claim 1, characterized in that at least one overflow pipe ( 22 ) for the transfer of the excess powder from the installation space ( 120 ) of the device ( 100 ) in the overflow container ( 20 ) is provided. Secondary circuit ( 10 ) according to claim 2, characterized in that the at least one overflow pipe ( 22 ) a shut-off valve ( 24 ) having. Secondary circuit ( 10 ) according to claim 3, characterized in that in the flow direction the shut-off valve ( 24 ) arranged downstream of at least one connection for the supply of inert gas. Secondary circuit ( 10 ) according to one of the preceding claims, characterized in that the overflow container ( 20 ) at least one level sensor ( 26 ) having. Secondary circuit ( 10 ) according to one of the preceding claims, characterized in that the return line ( 30 ) at her the overflow tank ( 20 ) facing away from a T-valve ( 32 ) for connection to the main circuit ( 110 ) having. Secondary circuit ( 10 ) according to one of the preceding claims, characterized in that at least the return line ( 30 ) is inertizable. Secondary circuit ( 10 ) according to one of the preceding claims, characterized in that the return line ( 30 ) is designed as a steel tube for powder delivery. Contraption ( 10 ) for the production of three-dimensional metallic objects, comprising a main circuit ( 110 ) for metallic powder with a main tank ( 130 ), a cyclone ( 140 ) and / or a sieve ( 150 ), wherein a space ( 120 ) in which the object is irradiated by irradiation of one of the main tank ( 130 ) provided metallic powder, characterized in that a secondary circuit ( 10 ) is provided with the features of one of claims 1 to 8. Contraption ( 100 ) according to claim 9, characterized in that the main circuit ( 110 ) a powder suction hose ( 112 ) for the extraction of powder from the installation space ( 120 ) having. Contraption ( 100 ) according to one of claims 9 or 10, characterized in that the secondary circuit ( 10 ) in the flow direction according to the installation space ( 120 ) and before the cyclone ( 140 ) and / or the sieve ( 150 ) with the main circuit ( 110 ) connected is. Method for handling excess powder in a device ( 100 ) for the production of three-dimensional metallic objects, characterized in that the excess powder in an overflow container ( 20 ) and from the overflow container ( 20 ) via a return line ( 30 ) a main circuit ( 110 ) of the device ( 100 ) is supplied, wherein the overflow container ( 20 ) and the return line ( 30 ), in particular a secondary circuit ( 10 ) with the features of one of claims 1 to 8 form. Method according to claim 12, characterized in that the method for a device ( 100 ) is used with the features of one of claims 9 to 11.

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