Electron beam installation and method for working powdered material

Abstract

An electron beam installation, which is used for processing powdered material, has a powder container, which can accommodate a powder bed made of the powdered material to be processed. Furthermore, it has an electron beam generator, which is configured to direct an electron beam onto laterally differing locations of the powder bed. To reduce the dispersion of the powdered material during the processing using the electron beam, the electron beam installation has a frit device, which, by applying an AC voltage between at least two electrodes, generates an electromagnetic alternating field, which bonds the powdered material of the powder bed, at least in regions over the powder bed.

Claims

1. An electron beam installation, which is used for processing powdered material, comprising: a powder container, which can accommodate a powder bed made of the powdered material to be processed; an electron beam generator, which is configured to direct an electron beam onto laterally differing locations of the powder bed; and a coherer device which is configured to apply an AC voltage between at least two electrodes to generate an electromagnetic alternating field, which bonds the powdered material of the powder bed, at least in regions over the powder bed, wherein the frequency of the AC voltage is greater than 5 kHz.

2. The electron beam installation of claim 1, wherein the power and/or the frequency of the AC voltage of the coherer device and the power of the electron beam are selected so that the bonded powdered material is not dispersed during subsequent processing using the electron beam, wherein the powdered material at locations at which no processing takes place using the electron beam is only bonded by the coherer device such that the powdered material can be detached again at the locations by impacts.

3. The electron beam installation of claim 2, wherein the subsequent processing using the electron beam comprises melting of the powdered material.

4. The electron beam installation of claim 1, wherein at least one of the electrodes of the coherer device is arranged at a fixed position inside the electron beam installation.

5. The electron beam installation of claim 1, wherein the at least two electrodes of the coherer device are arranged horizontally in a plane parallel to an uppermost powder layer of the powder bed.

6. The electron beam installation of claim 1, wherein the at least two electrodes of the coherer device are arranged symmetrically in relation to a lateral region in which the electron beam can be directed onto the powder bed.

7. The electron beam installation of claim 1, wherein at least one of the electrodes of the coherer device is configured to be moved along at least one axis above the powder bed.

8. The electron beam installation of claim 1, wherein the powder container has a powder bed table base, which is electrically conductive and at the same time forms at least one of the electrodes of the coherer device.

9. The electron beam installation of claim 1, wherein at least one of the electrodes of the coherer device is formed by the electron beam itself, by the electron beam generator being operated in a pulsed manner, and/or by the electron beam being deflected at high deflection speed.

10. The electron beam installation of claim 1, wherein the powdered material is a metallic powder, and the electron beam is configured to selectively fuse particles of the powdered material with one another to create a 3D structure.

11. A method for processing powdered material using the electron beam installation of claim 1, the method comprising the following steps: applying an AC voltage between the at least two electrodes using the coherer device to generate the electromagnetic alternating field; and processing the powdered material using the electron beam.

12. An electron beam installation, which is used for selective melting of powdered material to form a 3D structure, comprising: a powder container, which can accommodate a powder bed made of the powdered material to be selectively fused; an electron beam generator, which is configured to direct an electron beam onto laterally differing locations of the powder bed to selectively fuse the powdered material; and a coherer device which is configured to apply an AC voltage between at least two electrodes to generate an electromagnetic alternating field, which bonds the powdered material of the powder bed, at least in regions over the powder bed, before the selective fusion with the electron beam generator, wherein the frequencies at which the AC voltage of the coherer device is operated are greater than 5 kHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are explained in greater detail hereafter on the basis of the drawings. In the figures:

(2) FIG. 1 shows a perspective view of an electron beam installation according to the invention comprising a powder bed table base as a powder container and a coherer device;

(3) FIG. 2 shows a sectional view of an electron beam installation according to a second exemplary embodiment having a differently designed powder container for the powder bed;

(4) FIG. 3 shows an explanatory illustration on the procedure of cohering.

DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

(5) FIG. 1 shows an electron beam installation 10 comprising a vacuum housing 12, in which an electron beam gun 14 is arranged for generating an electron beam 16.

(6) In the present exemplary embodiment, the electron beam gun 14 is arranged above a lifting table 18 comprising an electrically conductive lifting plate 19 and comprising a receptacle frame 20, which is used as a spatially delimited powder container, which accommodates a powder bed 22 made of a powdered material to be processed. In this case, further side walls (not shown here) can be provided for the further lateral delimitation of the powder bed 22.

(7) If the lifting plate 19 is moved downward, the powder bed 22 can gradually occupy a region which becomes larger, so that the powder bed 22 is enlarged layer-by-layer.

(8) For this purpose, a powder application device 24 comprising a squeegee, which can be moved using a travel device 26 over the lifting table 18, is arranged above the receptacle frame 20. The powder application device 24 has a container (not shown) for the powdered material, from which the material can be squeegeed flatly onto the powder bed 22 by a travel movement as the respective uppermost loose layer 28.

(9) The travel device 26 furthermore also carries a coherer electrode rail 30 in the exemplary embodiment shown here, which is connected via an electric line 32 to a coherer control unit 34. The coherer electrode rail 30 can also be moved in another manner over the powder bed 22, however.

(10) In contrast, the coherer control unit 34 is connected to the lifting plate 19 as a counter electrode via another electric line 36.

(11) The coherer control unit 34 has an AC voltage source 35, using which AC voltage can be applied to the coherer electrode rail 30 as the first electrode and the lifting plate 19 as the second electrode.

(12) The coherer electrode rail 30, the lifting plate 19, and also the coherer control unit 34 together form a coherer device, which can comprise still further components and the purpose of which will be explained in greater detail hereafter.

(13) Furthermore, a 3D structure illustrated as a star by way of example is identified by the reference sign 80 in FIG. 1, which was gradually formed or printed by fusing individual particles in the powder bed 22 with the aid of the electron beam 16.

(14) A modified exemplary embodiment of the electron beam installation 10 is shown in FIG. 2, wherein functional or structurally similar components are identified by the same reference signs as in FIG. 1.

(15) The lifting table 18 comprising a lifting plate 19, which is not necessarily electrically conductive here, can be seen in a section in FIG. 2.

(16) However, the receptacle frame 20 supports a first strip-shaped coherer lateral electrode 30, which is connected via the line 32 to the coherer control unit 34, on its upper end on one side of the powder bed 22. An associated counter electrode is arranged as a second coherer lateral electrode 31 on the laterally opposite side of the powder bed 22 and is connected via the line 36 to the coherer control unit 34. The coherer lateral electrodes 30, 31 are thus arranged on both sides of a lateral region onto which the electron beam 16 can be directed.

(17) Furthermore, a 3D structure 80 is clearly recognizable from FIG. 2, which is also complexly structured with recesses and bulges in the perpendicular direction in relation to the horizontal surface of the powder bed 22.

(18) Finally, in this exemplary embodiment, the coherer control unit 34 is arranged outside the vacuum housing 12.

(19) The electron beam installation 10 according to the invention operates as follows:

(20) Firstly, the uppermost loose layer 28 made of powdered material is applied using the powder application device 24. Trailing the movement of the powder application device 24, still during the movement or also following the movement, an AC voltage is then applied between the electrodes 30, 31, and 19 using the coherer control unit 34.

(21) Using an AC voltage, the frequency and power of which are selected accordingly adapted to the powdered material, as is apparent from FIG. 3, individual powder particles 42 of the loose layer 28 of the powder bed 22 are then bonded to one another by slight melting. As can be seen in FIG. 3 on the basis of the filter necks between the powder particles, a chain of powder particles 42 thus results, which has a higher and/or more continuous electrical conductivity than the loose powder particles 42 in the powder bed 22.

(22) During this procedure, the powder particles 42 are not dispersed out of the powder bed 22, since as a result of the AC voltage, the powder particles 42 do not become electrostatically charged and nonetheless a sufficiently high coherer current can be generated, which causes at least a part of the powder particles 42 to melt and agglomerate with one another.

(23) Subsequently, a more solid bond is created using the electron beam gun 14 by stronger melting of the powder particles 42 at points predetermined by the 3D structure 80 to be created of the powder bed 22 prepared via the coherer device and/or its uppermost loose layer 28. More solid in this context means that at the points processed by the electron beam 16, the powder particles 42 are more solidly bonded to one another in such a way that, for example, the 3D structure 80 can be removed from the powder bed 22 by dusting off the powder particles 42 which are only cohered.

(24) The above-described steps are each repeated layer-by-layer until the 3D structure 80 is ended.