CN215704148U

CN215704148U - Powder conveying system and equipment for manufacturing three-dimensional workpiece

Info

Publication number: CN215704148U
Application number: CN202022494990.2U
Authority: CN
Inventors: 卡斯滕·胡宾格
Original assignee: SLM Solutions Group AG
Current assignee: Nikon Slm Solutions Co ltd
Priority date: 2019-10-31
Filing date: 2020-11-02
Publication date: 2022-02-01
Anticipated expiration: 2030-11-02
Also published as: DE202019106061U1

Abstract

A powder transport system and an apparatus for manufacturing a three-dimensional workpiece, wherein the powder transport system comprises: a delivery line; a delivery mechanism disposed within the delivery line and configured to generate a first pressure within a first segment of the delivery line disposed upstream of the delivery mechanism, the first pressure being less than a second pressure within a second segment of the delivery line disposed downstream of the delivery mechanism; a balance container arranged in the second section of the conveying pipeline downstream of the conveying mechanism; a control valve which is set up to control the supply of the medium flowing through the second section of the feed line into the equalization container in such a way that the third pressure in the third section of the feed line approaches a desired target value.

Description

Powder conveying system and equipment for manufacturing three-dimensional workpiece

Technical Field

The utility model relates to a powder conveying system suitable for use in an apparatus for manufacturing a three-dimensional workpiece by means of an additive stack construction method. The utility model also relates to a device for producing three-dimensional workpieces, equipped with such a powder conveying system.

Background

In additive stack construction methods for producing three-dimensional workpieces, in particular so-called powder bed melting, raw material powder is applied layer by layer to a substrate and is locally selectively subjected to electromagnetic radiation, for example laser radiation or particle radiation, depending on the desired geometry of the workpiece to be produced. The radiation entering the powder layer causes heating and thus melting or sintering of the raw powder particles. Next, other raw material powder layers are sequentially applied to the layer on the base material that has been subjected to the irradiation treatment until the workpiece has a desired shape and size. The raw material powder may comprise a ceramic material, a metallic material or a plastic material, but may also contain a mixture thereof. Additive stack construction methods, and in particular powder bed fusion methods, can be used, for example, for producing prototypes, tools, spare parts or medical prostheses, such as, for example, dental or orthopaedic prostheses, and for repairing components according to CAD data.

An apparatus for producing three-dimensional workpieces by powder bed melting is described, for example, in EP 3023227B 1. The apparatus includes a working chamber in which a substrate and a powder spreading device for applying a raw material powder to the substrate are disposed. The working chamber is provided with a powder inlet for supplying the raw material powder to the powder spreading device and a powder outlet for discharging excess raw material powder from the working chamber. A powder circulation line connects the powder outlet of the working chamber to the powder inlet of the working chamber, in which powder circulation line a conveying mechanism for conveying the raw material powder through the powder circulation line is disposed.

Furthermore, a removal system suitable for use in an apparatus for producing three-dimensional workpieces by powder bed melting is disclosed in EP 3165303B 1 or EP 3167984B 1 for removing finished workpieces from the working chamber of the apparatus. The extraction systems each include a suction system for removing excess raw powder from the extracted workpiece.

SUMMERY OF THE UTILITY MODEL

The utility model is based on the object of specifying a powder conveying system which is suitable in particular for use in a device for producing three-dimensional workpieces by means of an additive-layer-stack construction method and which can operate reliably and efficiently. The utility model is also based on the object of providing a device for producing three-dimensional workpieces, which is equipped with such a powder circuit.

The powder delivery system includes a delivery line. The feed line is in particular a feed line which is suitable for being flowed through at least in regions by the medium containing the powder. The powder can be, for example, a powder or a powder mixture of metal, metal alloy, ceramic or plastic. Preferably, the powder to be conveyed through the conveying line is suitable for processing in an apparatus for manufacturing three-dimensional workpieces by means of an additive-layer-build method, in particular powder-bed melting, and may for example have a particle size in the range of less than 100 micrometers. The feed line is preferably constructed of a material, such as metal or a suitable plastic material, which is sufficient to withstand the abrasive load of the powder to be fed by the feed line on the material of the feed line.

A conveying mechanism is arranged in the conveying pipeline, and the conveying mechanism is set up to generate a first pressure in a first pipe section of the conveying pipeline arranged at the upstream of the conveying mechanism, and the first pressure is smaller than a second pressure in a second pipe section of the conveying pipeline arranged at the downstream of the conveying mechanism. In the context of the present application, the term "upstream" or "downstream" always relates to the flow direction of the medium in the conveying line conveyed through the conveying line by means of the conveying means.

Furthermore, the powder transport system comprises a balancing container provided in the second section of the transport line downstream of the transport mechanism. The equalization container is designed to receive at least a portion of the medium flowing through the second section of the feed line, so that a third pressure prevails in a third section of the feed line which is arranged downstream of the equalization container and is lower than the second pressure in the second section of the feed line. In operation of the powder conveying system, at least a part of the medium flowing through the second section of the conveying line can thus be diverted from the conveying line into the equalizing container, instead of being conducted directly into the third section of the conveying line.

The equalizing container thus allows to reduce the pressure difference which occurs during operation of the powder conveying system between the first end of the conveying line connected to the first tube section and the second end of the conveying line connected to the third tube section. Significant pressure fluctuations within the transfer line that may interfere with the operation of the powder transfer system may thereby be reduced. The powder conveying system can thus operate particularly reliably. Furthermore, by avoiding excessive pressure fluctuations in the conveying line, the conveying capacity of the conveying mechanism can be increased, so that the powder conveying system also works particularly efficiently.

The powder conveying system further comprises a control valve which is set up to control the supply of the medium flowing through the second section of the conveying line into the equalizing container in such a way that the third pressure in the third section of the conveying line approaches a desired target value. Thus, by means of the control valve, the third pressure in the third line section of the feed line can be adapted to a desired target value. For example, the third pressure in the third line section of the supply line can be set by means of the control valve to a target value which corresponds to the pressure in a system (e.g. a removal system) of the device for producing three-dimensional workpieces, which system is connected to the powder supply system.

The third pressure in the third section of the transfer line is preferably higher than the first pressure in the first section of the transfer line. The value of the third pressure prevailing in the third section of the feed line is accordingly preferably between the value of the first pressure in the first section of the feed line and the value of the second pressure in the second section of the feed line.

The first pressure is preferably a negative pressure below sea level atmospheric pressure. The underpressure in the first tube section of the feed line can originate, for example, from the flow resistance and/or flow losses of the powder-containing medium fed through the first tube section of the feed line. The losses due to the gas pressure resistance increase as the conveying range increases and the mass flow of powder through the first section of the conveying line increases. That is, the more powder that is transported through the first segment of the transport conduit, the lower the first pressure, i.e., the greater the negative pressure value, within the first segment of the transport conduit.

The second pressure in the second section of the transfer line is preferably a positive pressure above sea level atmospheric pressure, which is directly related to the first pressure in the first section of the transfer line. In particular, the lower the first pressure in the first section of the conveying line, i.e. the greater its negative pressure value, the higher the second (positive) pressure in the second section of the conveying line.

As with the second pressure, the third pressure prevailing in the third line section of the conveying line during operation of the conveying device by means of the equalization vessel is preferably also a positive pressure above the atmospheric pressure at sea level. However, as mentioned above, the third pressure is less than the second pressure, and therefore the equalization vessel prevents the second end of the transfer line, which is connected to the third section of the transfer line, from being subjected to the high second (positive) pressure.

In a particularly preferred embodiment of the powder delivery system, the equalizing container is an equalizing container with a variable receiving volume. In this way, a small or large part of the medium flowing through the second section of the conveying line can be discharged into the equalizing container as required during operation of the powder conveying system, in order to allow a desired reduced third pressure to occur in the third section of the conveying line.

The balancing container can, for example, be made at least in some regions of a flexible, stretchable material. For example, the equalization container can be designed in the form of a tube and at least partially made of an elastic (rubber) material. The expansion and contraction properties of the equalization vessel material may be selected based on the desired pressure equalization properties of the equalization vessel. For example, the material of the equalization container can be provided such that, when a defined pressure acts on the equalization container, the holding volume of the equalization container automatically increases according to the desired volume difference. This makes it possible to automatically adjust the third pressure in the third line section of the feed line.

Additionally or alternatively, the equalization vessel may comprise a bellows or be designed in the form of a bellows. The design of the bellows can also be selected such that, when a defined pressure acts on the equalization container, the holding volume of the equalization container is automatically increased by the desired volume difference in order to achieve an automatic adjustment of the third pressure in the third line section of the feed line.

In principle, it is conceivable to arrange the control valve in the inlet region of the equalization tank. Preferably, however, the control valve is arranged in the third line section of the feed line downstream of the equalization vessel. A particularly precise control of the third pressure in the third line section of the feed line can thereby be achieved.

The control valve can be designed, for example, in the form of a pinch valve or a proportional control disk valve. The control valve then allows a reliable and precise control of the supply of the medium flowing through the second section of the supply line into the equalizing container.

The feed line can preferably be flowed through by a mixture of powder and carrier gas at least in its first tube section which is arranged upstream of the feed device. In contrast, the feed line can preferably be flowed through by a substantially powder-free carrier gas at least in its second section downstream of the feed device. By "carrier gas substantially free of powder" is meant here a carrier gas which, although possibly also containing particulate impurities, no longer contains a significant amount of powder. The conveying means are therefore preferably designed to separate the powder contained in the mixture of powder and carrier gas from the carrier gas. The transport line can also be flowed through by a substantially powder-free carrier gas at least in its third section which is arranged downstream of the equalization vessel.

The carrier gas is preferably an inert gas. The carrier gas may be argon or nitrogen, for example. In particular, the carrier gas is provided to prevent undesired (oxidation) reactions of the powder conveyed through the conveying line. During operation of the powder conveying system, a portion of the carrier gas flowing at high pressure through the second section of the conveying line is directed into the equalizing vessel. A prior flushing or purging of the equalization vessel with carrier gas is not required here. Furthermore, since the equalization vessel is used for regulating the pressure in the third section of the conveying line, it is no longer necessary to provide additional (inert) carrier gas for pressure regulation. The carrier gas usage of the powder delivery system can thus be minimized.

The conveying mechanism preferably comprises a vacuum conveyor disposed in the conveying line. The vacuum conveyor may for example comprise a cyclone or be designed in the form of a cyclone. Furthermore, the conveying mechanism may comprise a vacuum generator provided in the conveying line downstream of the vacuum conveyor. The vacuum generator can be designed, for example, in the form of a pump or a blower. With such a design of the conveying mechanism, the vacuum conveyor can be used to separate powder from the mixture of powder and carrier gas supplied to the vacuum conveyor.

The powder conveying system may also comprise a storage container connected to the vacuum conveyor and set up for containing powder conveyed through the first tube section of the conveying line by means of the conveying mechanism. In other words, the storage container is preferably designed to receive powder which is separated by means of the vacuum conveyor from the mixture of powder and carrier gas which is fed to the vacuum conveyor.

The vacuum conveyor and the vacuum generator are preferably connected by a fourth tube section of the conveying line. In the fourth line section of the conveying line, a fourth pressure preferably occurs during operation of the powder conveying system. The fourth pressure may be substantially equal to the first (negative) pressure within the first segment of the transfer line. However, when the fourth section of the conveying line has been flowed through by the substantially powder-free carrier gas, the fourth pressure is preferably slightly higher, i.e. its underpressure is slightly lower than the first pressure.

An apparatus for manufacturing a three-dimensional workpiece by means of additive stack building comprises at least one powder conveying system as described above. The apparatus may also comprise a working chamber in which a movable powder spreading device is arranged, which is set up for applying a powder layer onto the substrate. Furthermore, the device may comprise an irradiation unit which is set up for selectively applying electromagnetic radiation or particle radiation, in particular laser radiation, to the powder layer applied to the substrate.

The apparatus may also include a take-out system for removing the three-dimensional workpiece from the working chamber of the apparatus. The first end of the delivery line of the powder delivery system may be connected to the powder outlet of the withdrawal system. And a second end of the delivery line of the powder delivery system may be connected to the gas inlet of the withdrawal system. Alternatively or additionally, however, the powder transport system can also be used in other parts of the apparatus which have to be supplied with powder.

Drawings

The utility model is described in detail below with reference to the schematic drawings, in which:

fig. 1 shows an apparatus for producing a three-dimensional workpiece by means of a additive stack construction method, which is equipped with a powder conveying system.

Detailed Description

As shown in fig. 1, the apparatus 100 includes a workpiece forming section 102 equipped with a working chamber 12. A powder laying device 14 arranged in the work chamber 12 is used to lay down raw material powder to be processed in the work chamber 12 on a substrate 16. The working chamber 12 may be sealed from the atmosphere. Substrate 16 may be vertically movable such that substrate 16 is gradually moved vertically downward toward build chamber 20 as the structural height of work piece 18 formed on substrate 16 layer by layer increases.

In addition, the device 100 comprises an irradiation unit 22 which is set up for selectively applying electromagnetic radiation or particle radiation, in particular laser radiation, locally to a powder layer applied to the substrate 16. The laser light emitted by the radiation source of the irradiation unit 22, which may be designed, for example, as a light-emitting diode-pumped ytterbium-doped fiber laser, has a wavelength of about 1070 nanometers to 1080 nanometers. The irradiation mechanism 22 further includes an optical unit for steering and processing the irradiated radiation emitted from the radiation source. The optical unit may comprise, inter alia, a radiation diffuser for diffusing the irradiated radiation, a scanning unit and an objective lens. Alternatively, the optical unit may comprise a radiation diffuser with focusing optics and a scanning unit. By means of the scanning unit, the focal position of the irradiated radiation can be changed and adjusted not only in the direction of the optical path of the irradiated radiation, but also in a plane perpendicular to the optical path. The scanning unit can be designed, for example, in the form of a galvanometer scanner and the objective lens can be an f-theta objective lens.

During operation of the device 100, the three-dimensional workpiece 18 is built up layer by selectively applying irradiation radiation locally to the raw material powder layers that are successively laid down on the substrate 16 by means of the powder laying device 14, and thus solidifying the raw material powder layers. The control of the irradiation radiation directed to the surface of the raw material powder layer can be performed, for example, in conjunction with CAD data of the workpiece 18 to be manufactured. After irradiation and thus locally selective solidification of each raw material powder layer, the substrate 16 is lowered vertically downwards towards the build chamber 20, the movement distance corresponding to the layer thickness. Finally, the finished workpiece 18 is completely removed within the build chamber 20. At this point, the workpiece 18 is embedded in the feedstock powder 24, which is laid down on the substrate 16 during the build process but is not irradiated.

After the end of the build process within the workpiece forming section 102 of the apparatus 100, the build chamber 20, together with the workpieces 18 contained therein, is closed by means of a lid (not shown). Build chamber mechanism 26, including substrate 16 with work piece 18 built thereon and build chamber 20, is then transferred from a work position within work piece forming section 102 adjacent work chamber 12 to a replacement position in build chamber replacement section 104 of apparatus 100. Once the build chamber mechanism 26 is transferred into the component chamber replacement section 104, a replacement substrate and replacement build chamber (not shown) may be installed within the workpiece forming section 102 so that a new build process may begin.

From the replacement position in component chamber replacement section 104, build chamber mechanism 26 is transferred further into a removal system 106, which is only schematically illustrated in fig. 1. In extraction system 106, build chamber mechanism 26 is cooled to a desired temperature. Finally, in the takeout system 106, the workpiece 18 is removed from the build chamber 20. The removal system 106 can be designed, for example, as a removal system as described in EP 3167984B 1. Work piece 18 is embedded in raw material powder 24 contained in build chamber 20 until it is removed from build chamber 20, and the powder is transported out of build chamber 20 and ultimately out of extraction system 106 by powder delivery system 30.

The powder delivery system 30 includes a delivery line 32 having a first end connected to a powder outlet 34 of the withdrawal system 106. And a second end of the delivery line 32 is connected to the intake port 36 of the extraction system 106. The powder outlet 34 of the extraction system 106 may be formed directly in the build chamber 20 housed within the extraction system 106. It is also contemplated that powder outlet 34 of withdrawal system 106 is connected to a separately formed powder outlet of build chamber 20. Similarly, the air inlet 36 of the extraction system 106 may be formed directly within a build chamber housed in the extraction system 106. It is also contemplated that gas inlet 36 of extraction system 106 is coupled to a separately formed gas inlet of build chamber 20.

It is important only that the mixture of powder and carrier gas can be transported from the take-off system 106 via the powder outlet 34 into the transport line 32 of the powder transport system 30, while the substantially powder-free carrier gas can be returned from the transport line 32 of the powder transport system 30 via the gas inlet 36 of the take-off system 106 to the take-off system 106. The carrier gas is preferably an inert gas, such as, for example, argon or nitrogen, which prevents undesired (oxidation) reactions of the starting powder 24.

A delivery device 38 is arranged in the delivery line 32, which is designed to generate a first pressure P1 in a first line section 32a of the delivery line 32 arranged upstream of the delivery device 38, which is lower than a second pressure P2 in a second line section 32b of the delivery line 32 arranged downstream of the delivery device 38. The first pressure P1 is a negative pressure below sea level atmospheric pressure resulting from flow resistance and/or flow losses of the powder-containing medium conveyed through the first pipe section 32a of the conveying line 32. The powder-containing medium conveyed through the first line portion 32a of the conveying line 32 is formed here by a mixture of the raw material powder 24 and the carrier gas, which is discharged from the discharge system 106. As the conveying range increases and the powder mass flow increases, the loss due to the air pressure resistance increases. That is, the more powder 24 that is transported through the first pipe section 32a of the transfer line 32, the lower the first pressure P1, i.e., the greater the negative pressure value, within the first pipe section 32a of the transfer line 32.

While the second pressure P2 within the second pipe segment 32b of the transfer line 32 is a positive pressure above sea level atmospheric pressure that is directly related to the first pressure P1 within the first pipe segment 32a of the transfer line 32. In particular, the lower the first pressure P1, i.e. the greater the negative pressure value thereof, in the first pipe section 32a of the feed line 32, the higher the second (positive) pressure P2 in the second pipe section 32b of the feed line 32.

The conveying means 38 comprise a vacuum conveyor 40, here designed as a cyclone, which is arranged in the conveying line 32. Further, the conveying mechanism 38 includes a vacuum generator 42 provided in the conveying line 32 downstream of the vacuum conveyor 40. The vacuum generator 42 can be designed, for example, in the form of a pump or a blower. While flowing through the vacuum conveyor 40, the mixture of powder and carrier gas is separated, i.e. the raw powder 24 contained in the mixture is separated from the carrier gas flow. The storage container 43 serves to accommodate the powder 24 which is conveyed by means of the conveying mechanism 38 through the first tube section 32a of the conveying line 32. The storage container 43 is connected to the vacuum conveyor 40, so that the powder 24 separated from the carrier gas stream by means of the vacuum conveyor 40 can be fed directly into the storage container 43.

Correspondingly, the feed line 32 is flowed through by the mixture of powder and carrier gas discharged from the discharge system 26 at least in its first line section 32a arranged upstream of the feed device 38. While the conveying line 32 is flowed through by the substantially powder-free carrier gas at least in its second pipe section 32b, which is arranged downstream of the conveying means 38.

The carrier gas is fed back into the withdrawal system 106 via the gas inlet 36 of the withdrawal system 106.

Furthermore, the powder transport system 30 comprises a balancing container 44 arranged in the second tube section 32b of the transport line 32 downstream of the transport mechanism 38. The equalization container 44 is designed to receive at least a portion of the medium flowing through the second pipe section 32a of the feed line 32, so that a third pressure P3 arises in a third pipe section 32c of the feed line 32, which is arranged downstream of the equalization container 44, which is lower than the second pressure P2 in the second pipe section 32b of the feed line 32. Thus, in operation of the powder delivery system 30, a portion of the substantially powder-free carrier gas flowing through the second segment 32b of the delivery line 32 is discharged from the delivery line 32 to the equalization vessel 44. The third tube section 32c of the feed line 32, which is arranged upstream of the equalization vessel 44, is flowed through by a substantially powder-free portion of the carrier gas which is not diverted into the equalization vessel 40.

As with the second pressure P2, the third pressure P3 occurring in the third section 32c of the conveying line 32 during operation of the conveying means 30 by means of the equalization vessel 44 is also a positive pressure above the atmospheric pressure at sea level and is therefore higher than the first (negative) pressure P1 in the first section 32a of the conveying line 32. However, the third pressure P3 is less than the second pressure P2, so that the equalization vessel 44 prevents the second end of the transfer line 32, which is connected to the third section 32c of the transfer line 32 and opens into the intake 36 of the extraction system 106, from experiencing the high second (positive) pressure P2.

In the embodiment of the powder conveying system 30 shown here, the equalization container 44 has a variable holding volume. Thus, in operation of the powder delivery system 30, a smaller or larger portion of the gas flow flowing through the second segment 32b of the delivery conduit 32 may be discharged to the equalization container 44 as needed to present the desired reduced third pressure P3 at the third segment 32c of the delivery conduit 32.

The equalization container 44 can be made of a flexible, stretchable material, for example, at least in some regions. For example, the equalization container 44 can be formed at least in regions from an elastic (rubber) material, wherein the elasticity of the material of the equalization container 44 can be selected depending on the desired pressure equalization behavior of the equalization container 44. Alternatively, the equalization container 44 may comprise a bellows 46 for this purpose, as shown in fig. 1.

Finally, the powder conveying system 30 comprises a control valve 48, which is set up to control the supply of the medium flowing through the second section 32b of the conveying line 32 into the equalizing container 44 in such a way that the third pressure P3 in the third section 32c of the conveying line approaches a desired target value. The control valve 48 has a variably adjustable flow cross section and can be designed, for example, as a pinch valve or as a proportional control disk valve. Correspondingly, the smaller the flow cross section of the control valve 48 is set, the more carrier gas can be conducted into the equalization vessel 44 in a controlled manner. The third pressure P3 in the third pipe section 32c of the feed line 32 can therefore be adapted to the desired target value by means of the control valve 48. In the exemplary embodiment of the powder delivery system 30 shown here, the third pressure P3 is controlled by means of the control valve 48 in such a way that it corresponds to the pressure prevailing in the removal system 106.

In principle, it is conceivable to arrange the control valve 32 in the inlet region of the equalization tank 44. However, in the exemplary embodiment of the powder conveying system 30 shown here, the control valve 32 is arranged downstream of the equalization container 44 in the third line section 32c of the conveying line 32.

The vacuum conveyor 40 and the vacuum generator 42 are connected by the fourth tube section 32d of the conveying line 32. In the fourth line section 32d of the feed line 32, a fourth pressure P4 occurs during operation of the powder feed system 30. The fourth pressure P4 is slightly higher, i.e. its negative pressure value is slightly smaller than the first pressure P1, because the fourth section 32d of the conveying line 32 has been flowed through by the substantially powder-free carrier gas.

Claims

1. A powder transport system for use in an apparatus (100) for manufacturing a three-dimensional workpiece (18) by means of an additive-stack construction method, wherein the powder transport system (30) comprises:

-a delivery line (32),

-a conveying means (38) arranged in the conveying line (32) and set up to generate a first pressure (P1) in a first section (32a) of the conveying line (32) arranged upstream of the conveying means (38), which is lower than a second pressure (P2) in a second section (32b) of the conveying line (32) arranged downstream of the conveying means (38),

-an equalization container (44) arranged in the second section (32b) of the conveying line (32) downstream of the conveying means (38), wherein the equalization container (44) is designed to accommodate at least a part of the medium flowing through the second section (32b) of the conveying line (32), so that a third pressure (P3) occurs in a third section (32c) of the conveying line (32) arranged downstream of the equalization container (44), which third pressure is lower than the second pressure (P2) in the second section (32b) of the conveying line (32), and

-a control valve (48) which is set up to control the supply of medium flowing through the second section (32b) of the feed line (32) into the equalizing vessel (44) in such a way that the third pressure (P3) in the third section (32c) of the feed line (32) approaches a desired target value.

2. The powder delivery system according to claim 1, wherein the third pressure (P3) in the third section (32c) of the delivery line (32) is higher than the first pressure (P1) in the first section (32a) of the delivery line (32).

3. Powder delivery system according to claim 1 or 2, wherein the first pressure (P1) is a negative pressure below sea level atmospheric pressure, and/or the second pressure (P2) is a positive pressure above sea level atmospheric pressure, and/or the third pressure (P3) is a positive pressure above sea level atmospheric pressure.

4. Powder delivery system according to claim 1 or 2, wherein the balancing container (44) is a balancing container (44) with a variable receiving volume.

5. Powder delivery system according to claim 1 or 2, wherein the balancing container (44) is at least partly made of a flexible, stretchable material.

6. Powder delivery system according to claim 1 or 2, wherein the control valve (48) is arranged in the third section (32c) of the delivery line (32) downstream of the equalizing container (44).

7. Powder delivery system according to claim 1 or 2, wherein the control valve (48) is designed in the form of a squeeze valve or a proportional control disk valve.

8. Powder conveying system according to claim 1 or 2, wherein the conveying line (32) is capable of being flowed through by a mixture of powder and carrier gas at least in its first section (32a) which is arranged upstream of the conveying means (38), and/or wherein the conveying line (32) is capable of being flowed through by a substantially powder-free carrier gas at least in its second section (32b) which is arranged downstream of the conveying means (38), and/or wherein the conveying line (32) is capable of being flowed through by a substantially powder-free carrier gas at least in its third section (32c) which is arranged downstream of the equalizing container (44).

9. The powder delivery system of claim 8, wherein the carrier gas is an inert gas.

10. Powder conveying system according to claim 1 or 2, wherein the conveying mechanism (38) comprises a vacuum conveyor (40) arranged in the conveying line (32) and a vacuum generator (42) arranged in the conveying line (32) downstream of the vacuum conveyor (40).

11. Powder conveying system according to claim 10, wherein the powder conveying system (30) further comprises a storage container (43) connected to the vacuum conveyor (40), which storage container is set up for accommodating powder (24) conveyed through the first tube section (32a) of the conveying line (32) by means of the conveying mechanism (38).

12. Powder conveying system according to claim 10, wherein the vacuum conveyor (40) and the vacuum generator (42) are connected by a fourth section (32d) of the conveying line (32), in which a fourth pressure (P4) occurs.

13. Powder delivery system according to claim 1 or 2, wherein the balancing container (44) comprises a bellows (46).

14. An apparatus for manufacturing three-dimensional workpieces, characterized in that it comprises at least one powder transport system (30) according to any one of claims 1 to 13.

15. The apparatus for producing three-dimensional workpieces according to claim 14, characterized in that the apparatus (100) comprises a take-out system (106) for removing the three-dimensional workpiece (18) from the working chamber (12) of the apparatus (100), wherein a first end of the conveying line (32) is connected to a powder outlet (34) of the take-out system (106) and/or wherein a second end of the conveying line (32) is connected to a gas inlet (36) of the take-out system (106).