Method and device for dosing of a powder for the additive manufacture of a product

1. A device for layered manufacture of at least a three-dimensional product based on a powder by an additive manufacturing technique, with

a build chamber with a vertically movable build platform on which said product is manufactured,

a powder dispenser for application of successive powder layers above the build platform in a horizontal build surface, where this powder dispenser can be moved back and forth over the build surface along a horizontal dispensing direction,

a hopper that must contain said powder to supply powder to said powder dispenser, where this hopper features a bottom in which a dosing opening is provided that lets out into said build chamber and that works in combination with a dosing valve,

wherein the intermediate position of the dosing valve, said dosing opening is completely covered by the dosing valve that extends laterally along both sides of the dosing opening over the bottom of the hopper, where a dosing space is present along both sides of the dosing opening between this bottom and the dosing valve, wherein the dosing spaces present practically the same volume in said intermediate position,

where the dosing valve has opposite edges extending along both sides of the dosing opening and situated at a level that corresponds to the level of the dosing opening or above this level,

where the dosing valve can go to a dosing position along both sides of the intermediate position, where the dosing valve can be moved back and forth between the two dosing positions, while the dosing opening is completely covered by the dosing valve,

where, in said dosing positions of the dosing valve, the volume of the dosing space on a side of the dosing opening is less than the volume of this space in the intermediate position, while on the opposite side of the dosing opening, the volume of the opposite dosing space is larger than the volume of the latter in the intermediate position.

2. A device according to claim 1 , wherein, due to the movement of the dosing valve to a dosing position, the volume of the dosing space is reduced on the side of the dosing opening opposite the side to which the dosing valve moves, while the volume of the dosing space increases on the latter side.

3. A device according to claim 1 , wherein both dosing spaces continuously remain connected to said dosing opening while moving the dosing valve between both dosing positions such that powder can flow from the hopper to at least one dosing space during said movement.

4. A device according to claim 1 , wherein said dosing space is formed by a dosing slit with a practically constant height that corresponds to the distance between said dosing valve and the bottom of said hopper.

5. A device according to claim 1 , wherein said bottom features a cylindrical convex surface, while the opposite surface of the dosing valve is concave cylindrical.

6. A device according to claim 1 , wherein the dosing valve is located primarily on a first side of the dosing opening in a first dosing position and on a second, opposite side of the dosing opening in a second dosing position.

7. A device according to claim 1 , wherein the dosing valve is movable with respect to the dosing opening to an open position where the dosing valve extends at least part way next to the dosing opening such that the latter is at least partly clear and powder can flow out from the hopper through the dosing opening.

8. A device according to claim 1 , wherein said dosing valve is mounted so it can rotate and thus may be subject to a pendulum motion between said dosing positions.

9. A device according to claim 1 , wherein the dosing opening contains an elongated recess in the bottom of the hopper, where the dosing valve is movable along a path that extends transverse to the longitudinal axis of said recess or of the dosing opening.

10. A device according to claim 1 , wherein the dosing valve can rotate around an axis of rotation that is parallel to a longitudinal axis of the dosing opening.

11. A device according to claim 1 , wherein the hopper features an inlet on the top that lets out onto a screening device with a screen to separate powder into a production fraction, which is suitable for manufacture of the product and that contains powder that flows through the screen and is collected in the hopper, and into a rejected fraction, which is removed from the hopper via the surface of said screen.

12. A device according to claim 1 , wherein said hopper extends laterally next to said build platform and where said powder dispenser contains at least two inlet openings for said powder between which a separator extends, where each inlet opening lets out onto a corresponding compartment, while the powder dispenser can be moved to a filling position in which the separator extends practically centered under said dosing opening so that each of said inlet openings extends on a side opposite the dosing opening in order to enable powder from the dosing space on the side opposite the dosing opening to flow to the side to which the dosing valve is moving, to the inlet opening located under this dosing space when the dosing valve is moved to a dosing position.

13. A device according to claim 12 , wherein a first compartment of the powder dispenser lets out onto the build surface, while a second compartment can be closed on the bottom such that a quantity of powder can be stored in this second compartment.

14. A device according to claim 12 , wherein a floor of at least said second compartment features closing means in order to close said floor when the powder dispenser is in said filling position.

15. A device according to claim 14 , wherein drive means are provided to open said closing means when the powder dispenser is located on the side of the build platform opposite the hopper in order to enable powder to flow from said second compartment to the build surface.

16. A device according to claim 12 , wherein the powder dispenser contains a dispensing member that extends up to said build surface for uniform dispensing of powder in a powder layer on the build surface during movement of the powder dispenser over the build surface, where this dispensing member contains a cylindrical roller and/or a scraper.

17. A device according to claim 16 , wherein said dispensing member extends between said compartments and where said first compartment is located between said second compartment and the build platform when the powder dispenser is placed in said filling position.

18. A device according to claim 1 , where said hopper contains a bleed channel that connects to said build chamber and extends into the vicinity of said dosing opening on the inside of the hopper, where this bleed channel allows the evacuation of air located in the powder present in the hopper when lowering the air pressure in the build chamber and/or in the hopper.

19. A device according to claim 18 , wherein said bleed channel contains a space that extends into a double wall of the hopper.

20. A method for the manufacture of at least a three-dimensional product by an additive manufacture technique, where successive powder layers are dispensed onto a build surface above a build platform,

where powder for the manufacture of said product is supplied to a hopper and the powder from the hopper flows to a powder dispenser, where the powder dispenser moves over said build surface to apply a powder layer to the build surface,

where a dosing valve is provided extending in front of a dosing opening of the hopper and the powder flows from the hopper through the dosing opening to the dosing valve, wherein between the dosing valve and the bottom of the hopper, at both sides of the dosing opening, a dosing space is created, where the dosing valve is moved between a first and a second dosing position wherein in each dosing position a corresponding powder flow is generated,

characterized in that, when moving the dosing valve to the first dosing position, a first powder flow is generated by making the powder flow from the first dosing space over a first edge of the dosing valve and thus the first dosing space is emptied at least partially while powder flows simultaneously through the dosing opening to the second dosing space to fill this space at least partially,

wherein a second powder stream is then generated by moving the dosing valve to the second dosing position where powder flows from the second dosing space over a second edge of the dosing valve such that the second dosing space is at least partially emptied while powder flows simultaneously through the dosing opening to the first dosing space to fill this space at least partially,

where the dosing valve is moved back and forth to each of both dosing positions in order to generate at each of said edges a corresponding powder flow,

where, during the displacement of the dosing valve between said dosing positions, each of said edges is maintained at a level that is equal to, or higher than, the level of the dosing opening, while each edge is kept at a corresponding side of the dosing opening such that the dosing opening remains covered by the dosing valve.

21. A method according to claim 20 , wherein two separate powder flows are created from the hopper by moving the dosing valve in combination with said dosing space along a back and forth axis between two dosing positions so that powder, under the influence of gravity, flows out of the dosing space alternating between opposite ends of the dosing space, thus generating a corresponding powder flow on each end, while powder is concurrently supplied from the hopper to the dosing space.

22. A method according to claim 21 , wherein said powder dispenser contains at least a first compartment and a second compartment with corresponding inlet openings for said powder, where said powder dispenser is moved to a filling position under the hopper and each of the powder flows through an inlet opening to the corresponding compartment.

23. A method according to claim 22 , wherein powder flows from said first compartment to said build surface while said powder dispenser is located in the filling position, while powder is stored in said second compartment.

24. A method according to claim 23 , wherein powder from said first compartment is dispensed on a build surface by moving said powder dispenser over this build surface to an opposite side of the build platform, while the powder stored in said second compartment is transported to this opposite side with the powder dispenser.

25. A method according to claim 24 , wherein on said opposite side, powder from the second compartment is applied to the build surface and dispensed over the build surface to create a subsequent powder layer, while said powder dispenser is moved back to the filling position.

26. A method according to claim 20 , wherein said dosing valve is submitted to a pendulum movement between said dosing positions to create said powder flows, while a fixed distance is maintained between the bottom of the hopper and the dosing valve.