METHOD FOR DISPENSING POWDER FROM AN INTERMEDIATE RESERVOIR OF A POWDER-BED FUSION APPARATUS AND A CORRESPONDING APPARATUS

Abstract

A dosing feeder for a powder-fusing apparatus that includes a powder inlet that is configured to receive powder from a discharge opening of a powder bunker, a powder outlet that is configured to release powder to a recoater reservoir of the powder fusion apparatus, and a powder support that is located in between the powder inlet and the powder outlet and that is configured to convey powder from the powder inlet to the powder outlet. The dosing feeder enables dosing of the powder transferred from the powder bunker to the recoater reservoir with high precision if the powder support is coupled to an ultrasonic transmitter and/or to a vibrational drive.

Claims

1. A dosing feeder for a powder-fusing apparatus, the dosing feeder comprising: a powder inlet configured to receive powderfrom a discharge opening of a powder bunker, a powder outlet configured to release powderto a recoater reservoir of the powder-fusing apparatus, a powder support being located in between the powder inlet and the powder outlet and configured to convey the powder from the powder inlet to the powder outlet, wherein: the powder support is coupled to an ultrasonic transmitter and/or to a vibrational drive, the powder supportcomprises a grate coupled to the ultrasonic transmitter and/or to the vibrational drive, thereby being configured to enable a powder flow through the grate by exiting the grateby operation of the ultrasonic transmitter and/or the vibrational drive.

2. The dosing feederof claim 1, wherein the powder supportcomprises a frame, wherein the grateis supported by the frame.

3. The dosing feeder of claim 1 further comprising a connecting element that connects the grate via the frameto the ultrasonic transmitterand/or to the vibrational drive.

4. The dosing feeder of claim 1, wherein: the dosing feedercomprises a feeder housing with a powder channel having a channel wall, wherein the powder channel connects the powder inlet and the powder outlet, and the grate is positioned transverse to a longitudinal extension of the powder channel, thereby separating the powder channel into an inlet facing upper channel portion and an outlet facing lower channel portion.

5. The dosing feeder of claim 4, wherein the channel wall forms a recess, into which the powder support sealingly engages.

6. The dosing feeder of claim 4, wherein the powder supporthas a recess into which a protrusion of the channel wall sealingly engages.

7. The dosing feeder of claim 4, wherein an elastic member is positioned between the powder support and the housing to prevent a direct transmission of vibrations from the powder support to the housing.

8. A powder-bed fusing apparatus, comprising: at least one dosing feeder according to claim 1, a process chamber, a powder bunker with a powder release opening connecting a volume of the bunker with the process chamber, and a recoater reservoirin the process chamber, wherein: the powder inlet of the dosing feeder is positioned below the powder release opening of the powder bunker, and the powder outlet of the dosing feeder dosing feeder’s powder outlet (53) is positioned above the recoater reservoir.

9. The powder bed fusing apparatus of claim 8, wherein the powder bunker has a powder inlet opening connected to a powder distribution system that is configured to convey powdervia the powder inlet opening of the bunker into the bunker, and wherein the powder inlet opening of the bunker is protected by a sieve configured to separate particles with a dimension above a predefined dimension, the sieve having a sieve mesh size.

10. The powder-bed fusing apparatus of claim 9, wherein the grate has a grate mesh size that is larger than the sieve mesh size.

11. A method for filling a recoater reservoir of a powder-fusing apparatus that includes a process chamber, a powder bunker, a recoater reservoir, and a dosing feeder (40), wherein the dosing feeder has a powder support, the method comprising the steps of: (i) Discharging powder from the powder bunkeronto or into a grate of the powder support, and (ii) Exciting ultrasound at least in the grate of the powder supportof the dosing feeder and/or exciting at least the grate of the powder support to vibrate relative to a process chamber wall to thereby convey powder via an outletof the dosing feeder to the recoater reservoir.

12. The method of claim 11, wherein the powder support being excited is a powder support of the dosing feeder according to claim 1, and/or wherein the powder support being excited is the powder support of the powder-bed fusion apparatus according to claim 8.

13. The dosing feeder of claim 4, wherein an elastic member is positioned between the powder support and the housing.

14. The dosing feeder of claim 1, wherein the grate has a mesh size that is greater than a size of powder grains for doing of which the dosing feeder is configured.

15. The dosing feeder of claim 14, wherein the mesh size is smaller than a critical mesh size, and wherein the critical mesh size is defined such that, when the grate of the dosing feeder is static and has the critical mesh size, the powder placed onto the grate falls through the grate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment and with reference to the drawings.

[0032] FIG. 1 shows a first example of a powder-bed fusing apparatus.

[0033] FIG. 2 shows a second example of a powder-bed fusing apparatus.

[0034] FIG. 3 shows an example of dosing feeder in a longitudinal sectional view.

[0035] FIG. 4 shows the dosing feeder of FIG. 4 in a cross-sectional view perpendicular to the view in FIG. 3.

[0036] Generally, the drawings are not to scale. Like elements and components are referred to by like labels and numerals. For the simplicity of illustrations, not all elements and components depicted and labeled in one drawing are necessarily labels in another drawing even if these elements and components appear in such other drawing.

[0037] While various modifications and alternative forms, of implementation of the idea of the invention are within the scope of the invention, specific embodiments thereof are shown by way of example in the drawings and are described below in detail. It should be understood, however, that the drawings and related detailed description are not intended to limit the implementation of the idea of the invention to the particular form disclosed in this application, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION

[0038] The powder-bed fusing apparatus 1 in FIG. 1 includes a process chamber 10 being defined by a process chamber housing wall 12. In operation the process chamber 10 is preferably filled with an inert gas. In a preferred example, a flow of the inert gas enters the process chamber 10 via at least a first opening in the process chamber housing wall 12 and leaves it via at least one other opening.

[0039] The process chamber 10 includes a base plate 11 being considered as bottom 11 of the process chamber 10. The support opening 14 accommodates a movably supported workpiece support 13, supporting a workpiece 4. For manufacturing the workpiece 4 powder 9 of a powder bed 6 on top of the workpiece support 4 is fused by a beam being generated by a beam emitting unit 3. The beam emitting unit 3 comprises a beam deflector or a beam directing means, configured to deflect or direct the generated beam onto the powder bed 6.

[0040] To enable fusing successive layers 7 of powder 9 a new layer 7 of powder 9 is added on top of the powder bed 6 by a recoater 61 (or 62 see FIG. 2) each fusing step. Subsequently, a portion of the powder grains in the newly applied top layer 7 is attached to the workpiece 4 being covered by the top layer 7 by selectively heating the powder grains using the beam generating unit 3. After the grains of the topmost layer 7 have been attached to and thereby integrated into the workpiece 4 the workpiece support 13 is lowered and the recoater 61 travels over the support opening 14 to thereby apply a new layer 7 of powder 9.

[0041] As depicted in FIG. 1, the recoater 61 includes a recoater reservoir 65. Every time the recoater 61 applies a new layer 7 of powder to the powder bed, the powder level in the recoater reservoir is reduced, as at least a portion of the powder 9 being stored in the recoater reservoir 65 is added to the powder bed 6 by the recoater 61. Once the powder level in the recoater reservoir 65 is below a given level and/or after each recoating step the recoater reservoir 65 may be (re)filled. To this end, the recoater reservoir 65 is positioned below a discharge opening 22 of an intermediate reservoir 20, herein referred to as powder bunker 20 or briefly bunker 20 as explained above.

[0042] A dosing feeder 40 is positioned between the bunker’s 20 discharge opening 22 and the recoater reservoir 65. Hence, the dosing feeder 40 is configured to control the amount of powder being transferred from the bunker 20 to the recoater reservoir 65. The dosing feeder 40 is connected by at least one control line 101 to a controller 100 of the powder-bed fusing apparatus. Hence the controller may be configured to control the amount of powder being conveyed by the dosing feeder 40 to the recoater reservoir 65. In the depicted example, a drive 57 of the dosing feeder 40 is connected via the at least one control line 101 to the controller 100.

[0043] Preferably, the powder-bed fusing apparatus further includes or is connected to at least one main powder tank 8, being connected via powder lines of a powder distribution system 6 to a powder inlet 21 of a bunker(s) 20 as shown in FIG. 1 and FIG. 2. A (second) sieve is positioned upstream the bunker’s powder inlet 21.

[0044] The main powder tank 8 may be firmly connected to or separate from the housing enclosing the process chamber 10, the bunker 20 and the beam generating unit 3. Also, different bunkers 20 enclosed by different housings may be connected collectively at least one main powder tank 8. Generalizing, at least one a main powder tank 8 is connected to at least one of multiple different powder-bed fusing apparatuses and configured to feed the(ir) respective bunker(s) via a powder-supply line.

[0045] In FIG. 1 and FIG. 2, the main tanks 8 are depicted to be smaller than the bunkers 20, however, in practice the opposite is preferred.

[0046] Excess powder is collected in optional excess powder traps 15 in the bottom plate 11 and may be conveyed by the powder distribution system 6 via the optional (sieves) upstream the powder inlets 21 into the bunker 20.

[0047] It should be noted that FIG. 1 shows two bunkers and two dosing feeders. In other examples only a single bunker 20 and a single dosing feeder 40 may be employed. In this sense, the powder-bed fusing apparatus comprises at least one (1) bunker 20. In yet other examples, the bunker 20 can be omitted. In these examples the dosing feed may receive the powder to be dosed directly from the tank 8, e.g., via the optional (second) sieve upstream the dosing feeder. For example, the powder-bed fusing apparatus may comprise multiple bunkers 20 and/or dosing feeders 40, wherein different bunkers 20 and/or dosing feeders 40 may be configured to feed different powders (the powders may vary in grain size and/or material composition) to a recoater.

[0048] FIG. 2 shows another powder-bed fusing apparatus 1, being very similar to the powder-bed fusing apparatus 1 in FIG. 1 and the description of FIG. 1 can be read on FIG. 2 as well, except for the recoater: In FIG. 2, the recoater 62 fails to have a movable reservoir like recoater 61 in FIG. 1. The recoater 62 in FIG. 2 includes a distribution means, e.g. a blade, being movably supported to travel forth and back over the support opening 14 to thereby distribute an amount of powder 9 being deposited on top of the process chamber’s 10 base plate 11, defining the bottom of the process chamber 10. The location where the powder embankment has been deposited is thus a powder reservoir 65. This powder embankment may be pushed over the support opening 14 by the recoater 62 to thereby apply a new powder layer 7 to the powder bed 6. In this sense, the location on the base plate 11 supporting the powder 9 embankment can be considered as a recoater reservoir 65. As explained with respect to FIG. 1, a dosing feeder is positioned below the bunker’s 20 discharge opening 22. Thereby, powder 9 in the bunker 20 flows onto the powder support plate 55 until the accumulates powder 9 embankment on the support plate 55 blocks the discharge opening 22. Thus, the discharge opening 22 can be considered to define the dosing feeder’s 40 powder inlet 51.

[0049] As depicted in FIG. 2, in an embodiment, the powder support plate 55 is connected to a drive 57 (shown as 57a and 57b). The drive 57 is preferably an ultrasonic transmitter, being coupled to at least one support plate 55 to thereby couple ultrasound waves into the powder support plate 55. Alternatively, the drive may reciprocate the powder support plate or excite other kind of vibrations of the powder support plate 55. The ultrasound and/or the vibrations at least partially fluidize the powder embankment on the powder support plate, and the powder thus flows over the process chamber 10 facing edge 551 of the powder support plate 55 onto the location 65 (the recoater reservoir 65) on the base plate 11. The edge 551 can thus be considered as a powder outlet of the dosing feeder 40 in FIG. 2.

[0050] In an Embodiment, the amount of powder 9 being dosed onto the location 65 is controlled by the controller 100, e.g. by the time the respective drive 47 is operated, assuming the amplitude and frequency of the excitation to be constant, but of course, in another embodiment, the controller is as well configured to control the frequency and/or the amplitude of the excitation.

[0051] Another preferred example of a dosing feeder is depicted in FIG. 3 and FIG. 4: The dosing feeder 40 may replace the dosing feeders 40 in FIG. 1 and/or FIG. 2.

[0052] As shown in FIG. 3 and FIG. 4, the dosing feeder 40 includes a housing 50 with a channel 52 being delimited by a channel wall 521. The channel wall 521 includes at least a first opening 51, the powder inlet 51 and second opening 53, the powder outlet 53. In other words, the channel 52 provides a fluid communication from the powder inlet 51 to the powder outlet 53 (if the channel is not filled with powder).

[0053] The channel 52 includes a recess 522. A frame 54 of a powder support engages into the recess 544 to thereby maintain the powder support in a position in which it traverses the channel 52. The powder support thus separates the channel 52 in an upper and an lower portion, wherein the powder inlet faces upwards to the bunker’s 20 discharge opening (if mounted as intended) and the powder outlet 53 downwards to the reservoir. In a preferred embodiment the powder inlet is attached to the powder discharge opening 22 (see FIG. 1).

[0054] In an example, the frame 54 engages preferably peripherally into the recess 522 and the gap between the frame 54 and the channel wall 521 is preferably sealed, e.g., by at least one gasket 523. The frame 54 supports a powder support grate 55 being a sieve. The mesh size of the sieve is preferably bigger than the specified median grain size of the powder 9, but smaller than the critical mesh size. Hence, as long as the powder support grate 55 is not excited by a drive 47, being an ultrasonic transmitter and/or a vibrational drive, the powder 9 falling down through the bunker’s discharge opening 22 into the channel 52 accumulates on the grate, with only negligible powder fall through. Operating the drive 47, however, releases a powder flow through the grate 55 and the lower portion of the channel 52 into (or onto) the recoater reservoir 65. Similar to the examples in FIG. 1 and FIG. 2, the drive 47 is controlled by a controller 100 via a control line 101.

[0055] It will be appreciated by those skilled in the art having the benefit of this disclosure that this invention is believed to provide dosing feeder for a powder-fusing apparatus, a powder-fusing apparatus and a method for filling a recoater, e.g., of a powder-fusing apparatus. Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.

TABLE-US-00001 LIST OF REFERENCE NUMERALS 1 powder-bed fusing apparatus 3 beam emitting unit 5 workpiece 6 powder bed 7 powder layer 8 main powder tank 9 powder 10 process chamber 11 base plate / bottom 12 process chamber housing wall 13 workpiece support 14 support opening 15 excess powder trap 16 powder conveying system 20 Bunker/ intermediate reservoir 21 powder inlet of bunker 22 discharge opening of bunker 40 dosing feeder 50 housing of dosing feeder 51 powder inlet of dosing feeder 52 channel of dosing feeder 521 channel wall 522 recess in channel wall 523 gasket 53 powder outlet of dosing feeder 54 frame 55 powder support grate /powder support plate 551 edge of powder support plate 55 56 connecting element 57a, 57b vibrational drive / ultrasonic transmitter 61 recoater (type (i)) 62 recoater (type (ii)) 65 recoater reservoir 100 control unit 101 control lines