权利要求：
CLAIMS
1. A build material supply system for an apparatus for the layerwise manufacture of 3D objects from build material, the build material supply system comprising: - a dosing device configured to supply a dosed amount of build material to a work surface of the apparatus, the dosed amount comprising a layer amount and an excess amount surplus to forming the layer;
- a buffer tank configured to mix build material for supplying to the dosing device; - an excess return chamber for receiving excess build material from a distribution device; - a supply tank for holding fresh build material for replenishing the buffer tank; - a build material pump for transporting build material within the build material supply system; and
- a controller;
wherein an inlet of the build material pump is coupled to the supply tank via a first valve, to the excess return chamber via a second valve, and to the buffer tank via a third valve; and wherein an outlet of the pump is coupled to the buffer tank via a fourth valve and to an inlet of the dosing device via a fifth valve;
wherein the controller is coupled to the build material pump, and the first, second, third, fourth and fifth valve, and is configured to:
control the first, second and fourth valve to close, the third and fifth valve to open,
and the pump to operate, to allow build material to flow along a dosing flow path
from the buffer tank through the pump to the dosing device;
control the third and fifth valve to close, the first and fourth valve to open, and the
pump to operate to allow fresh build material to flow along a supply flow path from
the supply tank through the pump and into the buffer tank; and
control the third and fifth valve to close, the second and fourth valve to open, and
the pump to operate to allow excess build material to flow along an excess return
flow path from the excess return chamber through the pump and into the buffer tank; so as to control the amount of fresh build material compared to the excess amount of build material transported into the buffer tank.
2. The build material supply system of claim 1, wherein the dosing device comprises a dosing chamber coupled to the outlet of the pump and configured to receive build material
from the buffer tank via the pump; the dosing device further comprising an overflow chamber coupled to the dosing chamber and configured to receive an oversupply amount of build material transferred from the buffer tank to the dosing chamber when the build material in the dosing chamber reaches a predefined level, wherein the overflow chamber is coupled to the inlet of the pump via a sixth valve, and wherein the controller is configured to control the third and fifth valves to close, the sixth and fourth valves to open and the pump to operate to allow oversupplied build material to flow from along an oversupply return flow path from the overflow chamber through the pump to the buffer tank.
3. The build material supply system of claim 1, wherein the dosing device comprises a dosing chamber, and a bypass chamber having an inlet and a bypass outlet at either end of an intermediate section, the intermediate section comprising one or more intermediate outlets, wherein the bypass inlet is coupled to the outlet of the pump via the fourth valve and the bypass outlet is coupled to the inlet of the buffer tank, and wherein the dosing chamber comprises one or more dosing chamber inlets configured to receive build material from the bypass chamber and coupled to the one or more intermediate outlets to form one or more intermediate flow paths; such that when the controller controls the first, second and fourth valves to close and the third and fifth valves to open, and the pump to operate, build material is caused to flow along the dosing flow path from the buffer tank through the pump to the bypass chamber of the dosing device and along the one or more intermediate flow paths from the bypass chamber to the dosing chamber so as to supply build material from the buffer tank to the dosing chamber, and an oversupply build material to return along a direct oversupply return flow path from the bypass chamber direct to the buffer tank.
4. The build material supply system of claim 3, wherein the bypass outlet is coupled to the inlet of the buffer tank via a sixth valve; such that when the controller controls the first, second and fourth valves to close and the third, fifth valve and sixth valve, to open, and controls the pump to operate, build material is caused to flow along the dosing flow path and the one or more intermediate flow paths, and oversupply build material is caused to return to the buffer tank along the direct oversupply return flow path.
S. The build material supply system of claim 4, wherein the bypass outlet is further coupled to the inlet of the build material pump via a seventh valve, wherein the controller is coupled to the seventh valve and configured to control:
(i) the third, fifth and sixth valves to open, while controlling the first, second, fourth and seventh valves to close, and the pump to operate, to allow build material to flow along the dosing flow path and oversupply build material to return along the direct oversupply return flow path from the bypass chamber direct to the buffer tank;
(i1) the third and sixth valves to close and the fifth and seventh valve to open, and the pump to operate, to allow build material to circulate from the bypass chamber through the build material pump and back to the bypass chamber so as to reuse the oversupply amount of build material to fill the dosing chamber;
(111) the fifth and seventh valve to close, the pump to operate, and:
the second and fourth valves to open to allow excess build material to flow along the
excess return path into the buffer tank; and
the first and fourth valves to open to allow fresh build material to flow along the
supply flow path into the buffer tank.
6. A build material supply system for an apparatus for the layerwise manufacture of 3D objects from build material, the build material supply system comprising: - a dosing device configured to supply a dosed amount of build material to a work surface of the apparatus, the dosed amount comprising a layer amount and an excess amount surplus to forming the layer;
- a buffer tank configured to mix build material for supplying to the dosing device; - an excess return chamber for receiving excess build material from a distribution device; - a supply tank for holding fresh build material for replenishing the buffer tank; - a build material pump for transporting build material within the build material supply system; and a controller;
wherein an inlet of the build material pump is coupled to the supply tank via a first valve and to an outlet of the excess return chamber; an outlet of the pump is coupled to an inlet of the buffer tank; and an outlet of the buffer tank is coupled to an inlet of the dosing device;
wherein the controller is coupled to the pump and the first valve and is configured to:
- to control the first valve to open and the pump to operate to allow fresh build material
to flow along a supply flow path from the supply tank through the pump and into the
buffer tank; and
- operate the pump to allow excess build material to flow along an excess return flow
path from the excess return chamber through the pump and into the buffer tank;
so as to control the amount of fresh build material compared to the amount of excess
build material transported into the buffer tank.
7. The build material supply system of claim 6, wherein the inlet of the pump is coupled to the excess return chamber via a second valve, and wherein the controller is coupled to the second valve.
8. The build material supply system of claim 6 or claim 7, wherein the dosing device comprises a dosing device inlet configured to receive build material from the outlet of the buffer tank, wherein the controller is coupled to the dosing device and configured to control the dosing device to release the dosed amount.
9. The build material supply system of any preceding claim, wherein the controller controls the first valve to close to shut off the supply flow path and to control the pump to operate, and, where present, the second valve to open, to allow the excess build material to flow along the excess return flow path.
10. The build material supply system of any one of claim 1 to 8, wherein the controller controls the first, and where present the fourth and/or second valves to open so as to allow excess build material and fresh build material to flow simultaneously along the supply flow path and the excess return flow path.
11. The build material supply system of claim 10 when dependent on claim 2, wherein the controller further controls the sixth valve to open to allow oversupply build material to flow from the overflow chamber into the buffer tank simultaneously with the excess build material and fresh build material while controlling the third and fifth valves to close to shut off the dosing flow path.
12. The build material supply system of claim 11, wherein the sixth valve is a variable valve, wherein the controller is configured to control the sixth valve to be partially open, so as to
apply a higher flow resistance to the flow of oversupply build material through the oversupply return flow path compared to the flow resistance to the flow of excess build material along the excess return flow path.
13. The build material supply system of any one of claims 10 to claim 12, wherein the supply flow path is configured to have a higher flow resistance to build material flow than the excess return flow path.
14. The build material supply system of any one of claims 10 to 13, wherein the first valve is a variable valve, wherein the controller is configured to control the first valve to be partially open so as to apply a higher flow resistance to the flow of fresh build material through the supply flow path compared to the flow resistance to the flow of excess build material along the excess return flow path and, where present, compared to the flow resistance to the flow of oversupply build material along the oversupply return flow path.
15. The build material supply system of any one of claims 1 to 8, wherein the controller is configured to prioritise the flow of build material to the buffer tank by applying the order of: firstly, allowing excess build material to flow along the excess return path by controlling the first valve to be at least partially closed; secondly, where present, allowing oversupply build material to flow along the oversupply return path while controlling the first and second valves to be at least partially closed; thirdly, allowing fresh build material to flow along the supply flow path while controlling the first valve to be at least partially open.
16. The build material supply system of any preceding claim, wherein the buffer tank comprises a fill level sensor configured to detect a fill level of build material inside the buffer tank, and wherein the controller is configured to open and shut the supply flow path based on the detected level of build material inside the buffer tank.
17. A method of transporting build material through a build material supply system of an apparatus for the layerwise manufacture of 3D objects from build material, the method comprising:
(a) operating a build material pump while opening a dosing flow path, from a buffer tank to a dosing device, to transport build material from the buffer tank to the dosing device;
(b) dosing a dosed amount of build material to a work surface of an apparatus, the dosed amount comprising a layer amount for forming a layer and an excess amount surplus to forming a layer;
(c) receiving excess build material within an excess return chamber;
(d) operating the build material pump while opening an excess return flow path to return excess build material from the excess return chamber to the buffer tank;
(e) operating the build material pump while opening a supply flow path, from a supply tank to the buffer tank, to transport build material from a supply tank to the buffer tank, until either a predetermined fill duration has passed or upon detecting that the level of build material in the buffer tank has reached a predefined fill level; and
(f) mixing the excess amount with the build material in the buffer tank.
18. The method of claim 17, comprising operating the build material pump continuously from step (a) to (f).
19. The method of claim 17 or 18, comprising closing the excess return and supply flow path before opening the dosing flow path at step (a), closing the dosing flow path and at least partially closing the supply flow path when opening the excess return flow path at step (d), and closing at least the dosing flow path when opening the supply flow path at step (e). 20. The method of any one of claims 17 to 19, comprising detecting a fill level of build material in the buffer tank and/or an excess build material level in the excess return chamber, and controlling a duration at step (d) over which the excess return path is open and/or a duration at step (e) over which the supply path is open.
21. The method of any one of claims 17 to 20, wherein the build material transported to the dosing device at step (a) comprises an oversupply amount of build material; wherein the step (b) further comprises a step (b1) of allowing the oversupply amount to flow out of the dosing device and a step (b2) of operating the pump while opening a further flow path from the dosing device to the buffer tank to return the oversupply amount to the buffer tank. 22. The method of claim 21, wherein step (b1) comprises allowing the oversupply amount to flow into an overflow chamber, and wherein step (b2) is applied while detecting a fill level of oversupply material in the overflow chamber, and/or upon detecting that a level of
excess build material in the excess return chamber and has fallen below a predefined excess build material level such that excess build material is returned to the buffer tank before oversupply build material is returned to the buffer tank.
23. The method of any one of claim 17 to claim 22, wherein excess build material at step (d) is returned to the buffer tank before transporting fresh build material from the supply tank to the buffer tank at step (e).
24. The method of any one of claim 17 to claim 22, wherein the steps (d) and (e) are applied simultaneously, and optionally comprise at least partially opening the respective flow paths s0 as to vary the flow resistances of the respective flow paths such that the amount of excess build material and fresh build material flowing into the buffer tank is at a predefined ratio. 25. The method of claim 23 or claim 24, wherein for a plurality of repeats of steps (a) to (f), step (d) and step (e) are controlled such that the predefined ratio remains substantially constant over the plurality of repeats.