SIEVING UNIT FOR SIEVING BUILD MATERIAL

Abstract

Sieving unit (1) for sieving build material (4) for an apparatus for additively manufacturing three-dimensional objects, which sieving unit (1) comprises a moving unit (17), in particular a vibrating unit, that is adapted to move a sieving element (2) for generating a sieving movement and conveying build material (4) to be sieved across the sieving element (2), wherein the sieving unit (1) comprises a determination unit (24) adapted to determine capacity information of the sieving element (2) relating to an amount of build material (4) to be sieved which is conveyed across the sieving element (2).

Claims

1. Sieving unit (1) for sieving build material (4) for an apparatus for additively manufacturing three-dimensional objects, which sieving unit (1) comprises a moving unit (17), in particular a vibrating unit, that is adapted to move a sieving element (2) for generating a sieving movement and conveying build material (4) to be sieved across the sieving element (2), characterized by a determination unit (24) adapted to determine capacity information of the sieving element (2) relating to an amount of build material (4) to be sieved which is conveyed across the sieving element (2).

2. Sieving unit according to claim 1, characterized in that the determination unit (24) comprises at least on line sensor (23) arranged above or beneath the sieving element (2) adapted to determine an intensity of a signal, in particular light, dependent on the amount of build material (4) being conveyed across the sieving element (2).

3. Sieving unit according to claim 1, characterized by a dose unit (3) for dosing, particularly powdery, build material (4), comprising a dose chamber (6) for receiving build material (4), wherein build material (4) is conveyed, in particular by gravity, between a build material inlet (7) and a build material outlet (8) of the dose chamber (6), wherein the dose unit (3) comprises at least one dose element (13) that is adapted to adjust a size of an aperture (14) of the build material outlet (8), in particular to at least one position between a fully opened position and a fully closed position, wherein an amount of build material (4) that is dosed onto the sieving element (2) can be controlled by the size of the aperture (14).

4. Sieving unit according to claim 3, characterized in that the dose element (13) is movable relative to the build material outlet (8), wherein dependent on an adjusted size of the aperture (14) of the build material outlet (8), the dose element (13) at least partially covers the build material outlet (8).

5. Sieving unit according to claim 3, characterized in that the dose element (13) is built as linearly movable plate-like element or pivotable flap or rotatable cam.

6. Sieving unit according to claim 3, characterized in that the position of the dose element (13) defines the build material flow through the build material outlet (8), in particular a layer thickness of build material (4) dispensable through the build material outlet (8).

7. Sieving unit according to claim 3, characterized in that the dose unit (3) is adapted to adjust the size of the aperture (14) of the build material outlet (8) dependent on at least one build material parameter, in particular a chemical and/or a physical and/or a mechanical build material (4) parameter.

8. Sieving unit according to claim 3, characterized in that the dose unit (3) is adapted to adjust the size of the aperture (14) of the build material outlet (8) and/or dependent on the capacity information.

9. Sieving unit according to claim 3, characterized in that the dose unit (3) is adapted to adjust the position of the dose element (13) in that the dose chamber (6) is self-sealing, wherein build material (4) received in the dose chamber (6) is withheld by the build material outlet (8).

10. Sieving unit according to claim 3, characterized in that the build material inlet (7) is arranged in an upper part of the dose chamber (6), in particular at the top of the dose chamber (6), and the build material outlet (8) is arranged in a lower part of the dose chamber (6), in particular at a lower edge of a side wall (9) of the dose chamber (6).

11. Sieving unit according to claim 3, characterized in that the build material outlet (8) is shaped as a slit or slit-like, in particular arranged in parallel to a bottom (10) of the dose chamber (6).

12. Sieving unit according to claim 3, characterized by a build material guiding element (11) that is arranged in the dose chamber (6) and is adapted to guide, in particular distribute, build material (4) entering the dose chamber (6) through the build material inlet (7) in the dose chamber (6).

13. Sieving unit according to claim 3, characterized by a fill level sensor that is adapted to determine a fill level of build material (4) in the dose chamber (6).

14. Apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material (4) which can be consolidated by means of an energy source, characterized by a sieving unit (1) according to claim 1.

15. Method for sieving build material (4) using a sieving unit (1), particularly a sieving unit (1) according to claim 1, in particular for an apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material (4) which can be consolidated by means of an energy source, characterized by determining capacity information of a sieving element (2) of the sieving unit (1) relating to an amount of build material (4) to be sieved which is conveyed across the sieving element (2).

Description

[0037] Exemplary embodiments of the invention are described with reference to the Fig. The Fig. are schematic diagrams, wherein

[0038] FIG. 1 shows an inventive sieving unit according to a first embodiment;

[0039] FIG. 2 shows a dose unit of the sieving unit from FIG. 1; and

[0040] FIG. 3 shows a dose unit according to a second embodiment.

[0041] FIG. 1 shows a sieving unit 1 with a sieving element 2, for example a mesh or a grid with a defined grid size/mesh size. The sieving unit 1 further comprises a dose unit 3 for dosing build material 4. The sieving unit 1 can, in particular, be used to sieve the build material 4 for an apparatus for additively manufacturing three-dimensional objects (not shown), for example build material 4 that was removed from a build chamber of an additive manufacturing apparatus after the additive manufacturing process is finished.

[0042] The build material 4 may be provided to the dose unit 3 via a build material supply unit 5, for example an automated build material transportation cycle attached to a build chamber or a removal unit of the additive manufacturing apparatus. The build material 4 that is provided to the dose unit 3 can be filled into a dose chamber 6 of the dose unit 3 via a build material inlet 7, wherein the build material 4 provided to the dose chamber 6 falls from the build material inlet 7 to a build material outlet 8 due to gravity. As can be derived from FIG. 1, the build material inlet 7 is arranged in an upper region of the dose unit 3, in particular at the top of the dose unit 3, whereas the build material outlet 8 is arranged in a lower region of the dose unit 3, in particular at a lower edge between a sidewall 9 and a bottom 10 of the dose unit 3. Hence, build material 4 received within the dose chamber 6 is carried via the bottom 10 of the dose chamber 6 and therefore, is decoupled from the sieving element 2. Thus, the volume of build material 4 is not in contact with the sieving element 2 before the build material 4 leaves the dose chamber 6 as it is dosed onto the sieving element 2.

[0043] The dose unit 3 further comprises a build material guiding unit 11 (optional) with several build material guiding elements 12 that are adapted to guide and distribute the build material 4 inside the dose chamber 6 of the dose unit 3. The dose rate/build material flow of build material 4 through the build material outlet 8 can be adjusted via a dose element 13 of the dose unit 3. In this exemplary embodiment, the dose element 13 is built as plate-like element that can be (linearly, vertically) moved relative to the build material outlet 8. In other words, an aperture size of an aperture 14 of the build material outlet 8 can be adjusted via the dose element 13. The dose element 13 can, in particular, be moved from a fully opened position in which the build material outlet 8 is fully opened to a fully closed position in which the build material outlet 8 is fully closed and of course, to any arbitrary position in between.

[0044] Hence, the size of the aperture 14 can be adjusted by positioning the dose element 13 relative to the build material outlet 8. Therefore, the thickness of a layer 15 of build material 4 that is dispensed through the aperture 14 can be adjusted via the position of the dose element 13. For example, in order to decrease the layer thickness of the layer 15 of build material 4 and thereby, the amount of build material 4 dispensed through the aperture 14, the dose element 13 can be lowered (indicated via arrow 16) and in order to increase the amount of build material 4 dispensed through the aperture 14, the dose element 13 can be raised (also indicated via arrow 16).

[0045] It is particularly possible that the dose chamber 6 of the dose unit 3 is self-sealing, wherein the, particularly slit-like, aperture 14, is adjusted via the position of the dose element 13, in that the build material 4 is withheld by the aperture 14 as long as no (dynamic) force is applied on the dose unit 3. The sieving unit 1 comprises a moving unit 17, in particular a vibratory conveyor, that is adapted to linearly move at least one part of the sieving unit 1 and the dose unit 3 together with the part of the sieving unit 1. Due to the vibratory movement of the moving unit 17, build material 4 is dispensed through the aperture 14 onto the sieving element 2. Dependent on various parameters of the build material 4, such as the particle size and parameters of the sieving element 2, such as the mesh size, build material 4 is conveyed over the sieving element 2 in a build material transport direction 18/conveying direction. Build material particles with a particle size matching a defined particle size, in particular that falls below a predefined particle size, as defined by the mesh size, will fall through the sieving element 2 into a build material receiving unit 19 and can afterwards be provided to another additive manufacturing process, for instance.

[0046] Oversized build material particles, such as build material particle conglomerates, are moved in build material transport direction 18 towards and into an overflow unit 20 and can therefore, be removed from the additive manufacturing process. The sieving unit 1 further comprises a vibratory unit 21 connected to the sieving element 2 for setting the sieving element 2 into vibration, such as an ultrasonic vibratory conveyor. The vibratory unit 21 further enhances the sieving process, as the sieving element 2 is set into vibration and therefore, allows for an improved sieving of the build material 4 resting on/being moved across the sieving element 2.

[0047] The dose element 13 of the dose unit 3 is connected to a drive mechanism 22, for example comprising an actuator and a control unit (optional, not shown), wherein the drive mechanism 22 is adapted to adjust the position of the dose element 13, particularly from outside the sieving unit 1. The position of the dose element 13 can particularly be adjusted dependent on various parameters, such as build material parameters, in particular physical, mechanical or chemical parameters of the build material 4. In particular, it is possible to adjust the position of the dose element 13 dependent on a layer thickness of the layer 15, in particular dependent on the aperture size of the aperture 14. In other words, if the amount of build material 4 that is dispensed on the sieving element 2 has to be adjusted, the drive mechanism 22 can be used to change the position of the dose element 13 relative to the build material outlet 8.

[0048] The sieving unit for further comprises 2 sensors 23, for example line sensors, that extend across the sieving element 2. The 2 sensors 23 arranged in different positions, wherein after the second sensor 23 a safety area 26 is arranged in conveying direction 18 between the sensor 23 and the overflow 20. In this exemplary embodiment the census 23 are adapted to generate a signal, in particular a light signal, between a signal generator and the signal receiver, wherein dependent on the amount of build material for that is currently conveyed across the region of the sieving element to the sensor 23 is assigned to, a corresponding signal can be received. In other words, a signal generator that is arranged above or beneath the sieving element to generate a signal that can be received with the corresponding signal receiver. Dependent on the amount of build material that is arranged between the signal generator and the signal receiver, the signal of various, in particular the intensity of the signal, such as a light signal.

[0049] Thus, it is possible to control the amount of build material for that is dispensed onto the sieving element to dependent on a capacity information that can be determined via a determination unit 24, e.g. a control unit, that is coupled with the sensors 23. Of course, it is also possible to use only one sensor 23. Thus, it is possible that the signal that is received via the signal receiver of the sensor 23 can be received via the determination unit 24, wherein the determination unit 24 is adapted to control the drive mechanism 22 and therefore, adjust the position of the dose element 13 and therefore, adjust the size of the aperture 14. Hence, dependent on the amount of build material for that can be determined via the sensor 23, e.g. arranged in advance to the safety area 26, it is possible to control the amount of build material for dispensed onto the sieving element 2. Therefore, the sieving process can be controlled more efficiently, as it is ensured that the sieving element to is used over the entire length of the sieving element 2 in conveying direction 18 and that good build material, e.g. build material 4 of a defined particle size, is not wasted and dispensed into the overflow 20.

[0050] FIG. 2 shows the dose unit 3 from FIG. 1 in a perspective view. For the sake of simplicity, the various parts of the sieving unit 1 are omitted, wherein only parts of the dose unit 3 are depicted. As can be derived from FIG. 2, the dose unit 3 comprises the build material inlet 7 arranged at the top of the dose unit 3, leading build material 4 into the dose chamber 6 towards the build material outlet 8 that is arranged in a lower region of the dose chamber 6, in particular at the edge between the sidewall 9 and the bottom 10 of the dose chamber 6. The dose element 13 partially covers the build material outlet 8 and therefore, adjusts an aperture size of the aperture 14 through which build material 4 can be conveyed and therefore, a layer 15 of build material 4 can be dispensed through the aperture 14. As described before, the thickness of the layer 15 can be adjusted by changing the position of 13 according to arrow 16, wherein by lowering the dose element 13 the layer thickness of the layer 15 can be decreased and by raising the dose element 13 of the layer thickness of the layer 15 can be increased.

[0051] The change in position of the dose element 13 can be controlled by the drive mechanism 22, in particular comprising an actuator and a control unit, as also described before. Dependent on the movement of the moving unit 17 (cf. FIG. 1) build material 4 exiting the aperture 14 is conveyed in build material flow direction 18.

[0052] FIG. 3 shows a dose unit 3 according to a second embodiment, wherein the same numerals are used for the same parts. The dose unit 3, as depicted in FIG. 3, also comprises a dose chamber 6 with a build material inlet 7 arranged at the top of the dose chamber 6 and a build material outlet 8 arranged in a lower region of the dose chamber 6, in particular arranged at the edge of the sidewall 9 and the bottom 10 of the dose chamber 6. Build material 4 can be filled into the dose chamber 6 through the build material inlet 7 via a build material supply unit 5, as also described before.

[0053] Deviant from the dose unit 3 according to the first embodiment, the dose unit 3 according to the second embodiment comprises a dose element 13 that is built as rotatable cam that can be rotated about an axis 25. The position of the dose element 13, in particular the rotation of the cam can be controlled via the drive mechanism 22. Dependent on the position of the dose element 13, in particular dependent on the rotation of the dose element 13, the thickness of the layer 15 of build material 4 that is dispensed through the aperture 14 can be adjusted. For example, by rotating the dose element 13 (in this Fig.) clockwise, the size of the aperture 14 can be decreased and rotating the dose element 13 counterclockwise increases the size of the aperture 14 and thereby, the thickness of the layer 15 of build material 4 dispensed through the aperture 14.

[0054] Of course, the inventive method can be performed on the inventive sieving unit 1, particularly using the inventive sieving unit 3. All features, details and advantages described with respect to the individual embodiments can arbitrarily combined, exchanged and transferred.