DE202019106061U1 - Powder conveyor system and system for the production of a three-dimensional workpiece - Google Patents

Abstract

Powder conveying system (30) for use in a system (100) for producing a three-dimensional workpiece (18) using a generative layer construction method, the powder conveying system (30) comprising: - a conveying line (32), - a conveying device arranged in the conveying line (32) (38), which is designed to generate a first pressure (P1) in a first section (32a) of the conveyor line (32) arranged upstream of the conveyor (38), which is lower than a second pressure (P2) in a downstream of the conveying device (38) arranged second section (32b) of the conveying line (32), - an expansion tank (44) arranged downstream of the conveying device (38) in the second section (32b) of the conveying line (32), the equalizing tank (44) being added to this is set up to receive at least a part of a medium flowing through the second section (32b) of the delivery line (32), so that it is located in a downstream of the outlet third section (32c) of the conveying line (32) arranged in the equal container (44) sets a third pressure (P3) which is lower than the second pressure (P2) in the second section (32b) of the conveying line (32), and Control valve (48), which is designed to control the supply of a medium flowing through the second section (32b) of the delivery line (32) into the expansion tank (44) such that the third pressure (P3) in the third section (32c ) the delivery line (32) approximates a desired setpoint.

Description

The invention relates to a powder conveyor system which is suitable for use in a system for producing a three-dimensional workpiece using a generative layer construction method. Furthermore, the invention relates to a system equipped with such a powder conveying system for producing a three-dimensional workpiece.

In generative layer construction methods for producing three-dimensional workpieces, in particular so-called powder bed melting, a raw material powder is applied in layers to a carrier and, depending on the desired geometry of the workpiece to be produced, is subjected to location-selective electromagnetic radiation, for example laser radiation, or particle radiation. The radiation penetrating into the powder layer causes heating and consequently a fusion or sintering of the raw material powder particles. Subsequently, further layers of raw material powder are successively applied to the already radiation-treated layer on the carrier until the workpiece has the desired shape and size. The raw material powder can comprise ceramic, metal or plastic materials, but also material mixtures thereof. Generative layer construction processes and in particular powder bed melting processes can be used for example for the production of prototypes, tools, spare parts or medical prostheses, such as dental or orthopedic prostheses, as well as for the repair of components on the basis of CAD data.

A device for producing three-dimensional workpieces by powder bed melting is, for example, in US Pat EP 3 023 227 B1 described. The device comprises a process chamber in which a carrier and a powder application device for applying a raw material powder are accommodated on the carrier. The process chamber is provided with a powder inlet for supplying raw material powder to the powder application device and a powder outlet for removing excess raw material powder from the process chamber. A powder circuit line, in which a conveying device for conveying the raw material powder through the powder circuit line is arranged, connects the powder outlet of the process chamber to the powder inlet of the process chamber.

Furthermore, in the EP 3 165 303 B1 or the EP 3 167 984 B1 Unpacking systems suitable for use in a device for producing three-dimensional workpieces by powder bed melting are disclosed, which serve to remove the finished workpieces from a process chamber of the device. The unpacking systems each include a suction system that is used to free the unpacked workpiece from excess raw material powder.

The object of the invention is to provide a powder conveying system which is particularly suitable for use in a system for producing a three-dimensional workpiece with the aid of a generative layer construction method and which can be operated reliably and efficiently. Furthermore, the invention is directed to the task of providing a system equipped with such a powder circuit for producing a three-dimensional workpiece.

This object is achieved by a powder conveyor system according to claim 1 and by a system for producing a three-dimensional workpiece according to claim 13.

A powder delivery system includes a delivery line. The delivery line is, in particular, a delivery line which is suitable for being flowed through at least in sections by a medium which contains a powder. The powder can be, for example, a powder or a powder mixture of metal, a metal alloy, ceramic or plastic. The powder to be conveyed by the conveying line is preferably suitable for processing in a system for producing a three-dimensional workpiece by means of a generative layer construction method, in particular powder bed melting, and can for example have particle sizes in the range <100 μm. The conveying line preferably consists of a material, for example metal or a suitable plastic material, which is sufficiently resistant to the abrasive stress on the material of the conveying line by the powder to be conveyed by the conveying line.

A conveyor device is arranged in the conveyor line and is configured to generate a first pressure in a first section of the conveyor line arranged upstream of the conveyor device, which pressure is lower than a second pressure in a second section of the conveyor line arranged downstream of the conveyor device. In the context of this application, the terms “upstream” and “downstream” consistently refer to the direction of flow of the medium in the delivery line conveyed through the delivery line by means of the delivery device.

Furthermore, the powder delivery system comprises an expansion tank arranged downstream of the delivery device in the second section of the delivery line. The expansion tank is set up to receive at least part of a medium flowing through the second section of the delivery line, so that it is in a A third pressure of the delivery line arranged downstream of the expansion tank sets a third pressure which is lower than the second pressure in the second section of the delivery line. During operation of the powder delivery system, at least part of the medium flowing through the second section of the delivery line can thus be branched out of the delivery line into the expansion tank instead of being led directly into the third section of the delivery line.

The expansion tank thus enables a reduction in the pressure difference that occurs during operation of the powder delivery system between a first end of the delivery line connected to the first section and a second end of the delivery line connected to the third section. As a result, strong pressure fluctuations within the delivery line, which could disrupt the operation of the powder delivery system, can be reduced. The powder conveyor system can therefore be operated particularly reliably. Furthermore, the avoidance of excessive pressure fluctuations in the delivery line enables the delivery capacity of the delivery device to be increased, so that the powder delivery system also works particularly efficiently.

The powder delivery system further comprises a control valve which is set up to control the supply of a medium flowing through the second section of the delivery line into the expansion tank in such a way that the third pressure in the third section of the delivery line approaches a desired target value. With the aid of the control valve, it is consequently possible to adapt the third pressure in the third section of the delivery line to a desired setpoint. For example, the third pressure in the third section of the conveying line can be set with the help of the control valve to a setpoint value which corresponds to the pressure in a system connected to the powder conveying system, for example an unpacking system of a system for producing a three-dimensional workpiece.

The third pressure in the third section of the delivery line is preferably higher than the first pressure in the first section of the delivery line. The value of the third pressure arising in the third section of the delivery line is accordingly preferably between the value of the first pressure in the first section of the delivery line and the value of the second pressure in the second section of the delivery line.

The first pressure is preferably a negative pressure below atmospheric pressure at sea level. The negative pressure in the first section of the delivery line can result, for example, from the flow resistance of the powder-containing medium delivered through the first section of the delivery line and / or flow losses. With increasing delivery range and increasing powder mass flow through the first section of the delivery line, the losses due to the pneumatic resistances increase. That is, the more powder that is conveyed through the first section of the delivery line, the lower, i.e. the more negative the first pressure in the first section of the delivery line.

The second pressure in the second section of the delivery line is preferably a positive pressure above atmospheric pressure at sea level, which is directly related to the first pressure in the first section of the delivery line. In particular, the lower, i.e. the lower the positive second pressure in the second section of the delivery line. any negative is the first pressure in the first section of the delivery line.

The third pressure, which is set in the third section of the delivery line during operation of the conveying device with the aid of the expansion tank, is preferably, like the second pressure, a positive pressure which is above atmospheric pressure at sea level. However, as explained above, the third pressure is less than the second pressure, so that the expansion tank prevents the second end of the delivery line connected to the third section of the delivery line from being exposed to the high positive second pressure.

In a particularly preferred embodiment of the powder conveying system, the expansion tank is an expansion tank with a variable receiving volume. This makes it possible that during operation of the powder delivery system, depending on requirements, a smaller or a larger proportion of the medium flowing through the second section of the delivery line can be discharged into the expansion tank in order to set a desired reduced third pressure in the third section of the delivery line to enable.

The expansion tank can, for example, consist at least in sections of a flexible, stretchable material. For example, the expansion tank can be tubular and at least in sections consist of an elastic (rubber) material. The expansion properties of the material of the expansion tank can be selected depending on the desired pressure compensation properties of the expansion tank. For example, the material of the expansion tank can be such that the receiving volume of the expansion tank is automatically increased by a desired differential volume when a certain pressure acts on the expansion tank. This will make one automatic adjustment of the third pressure in the third section of the delivery line possible.

Additionally or alternatively, the expansion tank can comprise a bellows or be designed in the form of a bellows. The design of the bellows can also be chosen such that the receiving volume of the expansion tank is automatically increased by a desired differential volume when a certain pressure acts on the expansion tank in order to enable the third pressure in the third section of the delivery line to be set automatically.

Basically, it is conceivable to arrange the control valve in the area of an inlet of the expansion tank. Preferably, however, the control valve is arranged downstream of the expansion tank in the third section of the delivery line. This enables particularly precise control of the third pressure in the third section of the delivery line.

The control valve can be designed, for example, in the form of a pinch valve or in the form of a proportionally regulated butterfly valve. The control valve then enables reliable and precise control of the supply of the medium flowing through the second section of the delivery line into the expansion tank.

A powder / carrier gas mixture can preferably flow through the delivery line at least in its first section arranged upstream of the delivery device. In contrast to this, essentially powder-free carrier gas can preferably flow through the delivery line, at least in its second section arranged downstream of the delivery device. An “essentially powder-free carrier gas” is understood here to mean a carrier gas which may still contain particulate impurities, but no longer contains a significant powder volume. The conveying device is therefore preferably set up to separate the powder contained in the powder / carrier gas mixture from the carrier gas. Substantially powder-free carrier gas can also flow through the conveying line, at least in its third section arranged downstream of the expansion tank.

The carrier gas is preferably an inert gas. For example, the carrier gas can be argon or nitrogen. In particular, the carrier gas is set up to prevent undesired (oxidation) reactions of the powder conveyed through the conveying line. During operation of the powder delivery system, part of the carrier gas flowing through the second section of the delivery line at high pressure is conducted into the expansion tank. Flooding or purging the expansion tank with carrier gas is not necessary. In addition, the use of the expansion tank to regulate the pressure in the third section of the delivery line makes the provision of additional (inert) carrier gas for this pressure control superfluous. The carrier gas consumption of the powder delivery system can thus be minimized.

The conveyor device preferably comprises a vacuum conveyor arranged in the conveyor line. The vacuum conveyor can, for example, comprise a cyclone or be designed in the form of a cyclone. In addition, the conveyor device can comprise a vacuum generator arranged downstream of the vacuum conveyor in the conveyor line. The vacuum generator can be designed, for example, in the form of a pump or a blower. In such a configuration of the conveying device, the vacuum conveyor can be used to separate the powder from the powder / carrier gas mixture supplied to the vacuum conveyor.

The powder conveying system can further comprise a storage container connected to the vacuum conveyor, which is set up to receive powder conveyed through the first section of the conveying line by means of the conveying device. In other words, the storage container is preferably set up to receive the powder which is separated from the powder / carrier gas mixture supplied to the vacuum conveyor by means of the vacuum conveyor.

The vacuum conveyor and the vacuum generator are preferably connected to one another by a fourth section of the delivery line. A fourth pressure is preferably set in the fourth section of the delivery line during operation of the powder delivery system. The fourth pressure can substantially correspond to the negative first pressure in the first section of the delivery line. Preferably, however, the fourth pressure is slightly higher, i.e. slightly less negative than the first pressure when the fourth section of the delivery line is already being flowed through by essentially powder-free carrier gas.

A plant for producing a three-dimensional workpiece using a generative layer construction method comprises at least one powder conveying system described above. The system can further comprise a process chamber in which a movable powder application device is arranged, which is set up to apply a layer of powder to a carrier. In addition, the system can comprise an irradiation unit which is set up to selectively apply an electromagnetic layer to a powder layer applied to the carrier Radiation or particle radiation, especially laser radiation.

The system can further comprise an unpacking system for removing the three-dimensional workpiece from the process chamber of the system. The first end of the delivery line of the powder delivery system can be connected to a powder outlet of the unpacking system. The second end of the delivery line of the powder delivery system, however, can be connected to a gas inlet of the unpacking system. As an alternative or in addition to this, however, the powder conveying system can also be used at other points in the system where powder has to be conveyed.

• 1 eine mit einem Pulverfördersystem ausgestattete Anlage zur Herstellung eines dreidimensionalen Werkstücks mithilfe eines generativen Schichtbauverfahrens zeigt.

The invention is described in more detail below with reference to the attached schematic figure, in which:

• 1 shows a system equipped with a powder conveying system for producing a three-dimensional workpiece using a generative layer construction method.

One in 1 shown plant 100 includes a workpiece creation section 102 with a process chamber 12 Is provided. One in the process chamber 12 arranged powder application device 14 serves one in the process chamber 12 Raw material powder to be processed on a carrier 16 applied. The process chamber 12 is sealable against the surrounding atmosphere. The carrier 16 can be moved in the vertical direction so that the carrier 16 with increasing overall height one in layers on the carrier 16 assembled workpiece 18 gradually in the vertical direction down into a building chamber 20 can be moved.

The facility also includes 100 an irradiation unit 22 that is set up one on the carrier 16 to apply applied powder layer in a location-selective manner with electromagnetic radiation or particle radiation, in particular laser radiation. A radiation source of the radiation unit 22 which can be in the form of a diode-pumped ytterbium fiber laser, for example, emits laser light with a wavelength of approximately 1070 and 1080 nm. The irradiation device 22 further comprises an optical unit for directing and processing the radiation beam emitted by the radiation source. In particular, the optical unit can comprise a beam expander for expanding the radiation beam, a scanning unit and an objective lens. As an alternative to this, the optical unit can comprise a beam expander with focusing optics and a scanning unit. With the aid of the scanning unit, the focus position of the radiation beam can be changed and adapted both in the direction of the beam path of the radiation beam and in a plane perpendicular to the beam path. The scanning unit can, for example, be in the form of a galvanometer scanner and the objective lens can be an f-theta objective lens.

In operation of the plant 100 the three-dimensional workpiece is built up in layers 18 by using the powder application device one after the other 14 on the carrier 16 applied raw material powder layers are irradiated locally with the radiation beam and thereby solidified. The radiation beam can be controlled via the raw material powder layers, for example on the basis of CAD data of the workpiece to be produced 18 respectively. After the irradiation and consequently location-selective solidification of each raw material powder layer, the carrier becomes 16 by a distance corresponding to the layer thickness in the vertical direction down into the building chamber 20 lowered. Finally, the finished workpiece 18 completely in the building chamber 20 added. The workpiece 18 is in raw material powder 24 embedded, which during the construction process on the carrier 16 applied but not irradiated.

After completion of the construction process in the workpiece production section 102 the plant 100 becomes the building chamber 20 with the workpiece contained in it 18 sealed using a lid (not shown). Then one becomes the carrier 16 with the workpiece built on it 18 as well as the building chamber 20 comprehensive construction chamber arrangement 26 from one to the process chamber 12 adjacent operating position in the workpiece generation section 102 in an exchange position in a construction chamber exchange section 104 the plant 100 transferred. Once the build chamber arrangement 26 in the building chamber exchange section 104 An exchange carrier and an exchange build chamber (not shown) can be transferred in the workpiece production section 102 be installed so that a new building process can be started.

From the exchange position in a construction chamber exchange section 104 becomes the building chamber arrangement 26 further into one in the 1 only schematically shown unpacking system 106 transferred. In the unpacking system 106 becomes the building chamber arrangement 26 cooled to a desired temperature. Finally, in the unpacking system 106 the workpiece 18 from the building chamber 20 taken. The unpacking system 106 can for example in the form of a EP 3 167 984 B1 Unpacking system described be formed. That in the building chamber 20 contained raw material powder 24 into which the workpiece 18 until it is removed from the building chamber 20 is embedded using a powder feed system 30 from the building chamber 20 and finally the unpacking system 106 dissipated.

The powder conveyor system 30 includes a conveyor line 32 , the first end with a powder outlet 34 the unpacking system 106 connected is. A second end of the delivery line 32 is against it with a gas inlet 36 the unpacking system 106 connected. The powder outlet 34 the unpacking system 106 can directly in the in the unpacking system 106 recorded building chamber 20 be trained. However, it is also conceivable that the powder outlet 34 the unpacking system 106 with a separately designed powder outlet from the building chamber 20 communicates. Similarly, the gas inlet 36 the unpacking system 106 directly in the in the unpacking system 106 recorded construction chamber be formed. However, it is also conceivable that the gas inlet 36 the unpacking system 106 with a separate gas inlet in the building chamber 20 communicates.

The only essential thing is that through the powder outlet 34 a powder / carrier gas mixture from the unpacking system 106 into the delivery line 32 of the powder conveyor system 30 can be directed while via the gas inlet 36 the unpacking system 106 essentially powder-free carrier gas from the delivery line 32 of the powder conveyor system 30 into the unpacking system 106 can be returned. The carrier gas is preferably an inert gas, such as argon or nitrogen, which undesired (oxidation) reactions of the raw material powder 24 prevented.

In the delivery line 32 is a funding agency 38 arranged, which is arranged in an upstream of the conveyor 38 arranged first section 32a the delivery line 32 a first print P1 generate less than a second pressure P2 in a downstream of the conveyor 38 arranged second section 32b the delivery line 32 , The first print P1 is a negative pressure below atmospheric pressure at sea level, which results from the flow resistance through the first section 32a the delivery line 32 conveyed powder-containing medium, and / or flow losses result. That through the first section 32a the delivery line 32 conveyed powder-containing medium is here through the mixture from the unpacking system 106 removed raw material powder 24 and the carrier gas. With increasing delivery range and increasing powder mass flow, the losses due to the pneumatic resistances increase. Ie, the more powder 24 through the first section 32a the delivery line 32 is promoted, the lower, ie the more negative the first pressure P1 in the first section 32a the delivery line 32 ,

The second print P2 in the second section 32b the delivery line 32 is, on the other hand, a positive pressure that is above atmospheric pressure at sea level, and that immediately corresponds to the first pressure P1 in the first section 32a the delivery line 32 related. In particular, the positive second pressure P2 in the second section 32b the delivery line 32 the higher, the lower, ie every negative the first pressure P1 in the first section 32a the delivery line 32 is.

The conveyor 38 includes one in the delivery line 32 arranged vacuum conveyor 40 , which is designed here in the form of a cyclone. In addition, the funding facility includes 38 one downstream of the vacuum conveyor 40 in the delivery line 32 arranged vacuum generator 42 , The vacuum generator 42 can be designed, for example, in the form of a pump or a blower. When flowing through the vacuum conveyor 40 the powder / carrier gas mixture is separated, ie the raw material powder contained in the mixture 24 is separated from the carrier gas stream. A storage container 43 serves that by means of the conveyor 38 through the first section 32a the delivery line 32 extracted powder 24 take. The storage container 43 is with the vacuum conveyor 40 connected so that by means of the vacuum conveyor 40 powder separated from the carrier gas stream 24 directly into the storage container 43 can be directed.

Accordingly, the delivery line 32 at least in their upstream of the conveyor 38 arranged first section 32a from which from the unpacking system 26 flows through discharged powder / carrier gas mixture. At least in their downstream of the conveyor 38 arranged second section 32b becomes the delivery line 32 on the other hand, essentially powder-free carrier gas flows through it.

This carrier gas is through the gas inlet 36 the unpacking system 106 into the unpacking system 106 recycled.

The powder conveying system also includes 30 one downstream of the conveyor 38 in the second section 32b the delivery line 32 arranged expansion tank 44 , The expansion tank 44 is set up to at least a part of the second section 32a the delivery line 32 through flowing medium so that it is in a downstream of the expansion tank 44 arranged third section 32c the delivery line 32 a third print P3 that is less than the second pressure P2 in the second section 32b the delivery line 32 , In the operation of the powder conveyor system 30 thus becomes part of the second section 32b the delivery line 32 flowing through essentially powder-free carrier gas from the delivery line 32 in the expansion tank 44 derived. The upstream of the expansion tank 44 arranged third section 32c the delivery line 32 is flowed through by the part of the substantially powder-free carrier gas that is not in the expansion tank 40 is branched off.

The third print P3 who is in operation of the conveyor 30 using the expansion tank 44 in the third section 32c the delivery line 32 is set, as is the second pressure P2 , a positive pressure above atmospheric pressure at sea level and therefore higher than the (negative) first pressure P1 in the first section 32a the delivery line 32 , The third print P3 however, is less than the second pressure P2 so that the expansion tank 44 prevents that from the third section 32c the delivery line 32 connected and in the gas inlet 36 the unpacking system 106 mouth of the second end of the delivery line 32 the high positive second pressure P2 is exposed.

In the exemplary embodiment of a powder conveying system illustrated here 30 is the expansion tank 44 a variable recording volume. This can result in the operation of the powder conveyor system 30 Depending on your needs, a smaller or a larger proportion of the second section 32b the delivery line 32 flowing gas flow into the expansion tank 44 to be derived in the third section 32c the delivery line 32 a desired reduced third pressure P3 to set.

The expansion tank 44 can for example consist of a flexible, stretchable material at least in sections. For example, the expansion tank 44 consist at least in sections of an elastic (rubber) material, the expansion properties of the material of the expansion tank 44 depending on the desired pressure compensation properties of the expansion tank 44 can be chosen. Additionally or alternatively, the expansion tank can 44 , as in 1 shown a bellows 46 include.

Finally, the powder delivery system includes 30 a control valve 48 which is set up to feed the second section 32b the delivery line 32 flowing medium into the expansion tank 44 to control such that the third pressure P3 in the third section 32c the delivery line approaches a desired setpoint. The control valve 48 has a variably adjustable flow cross-section and can be designed, for example, in the form of a pinch valve or in the form of a proportionally regulated disc valve. Accordingly, the more carrier gas can enter the expansion tank in a controlled manner 44 are directed, the smaller the flow cross section of the control valve 48 is set. Using the control valve 48 is therefore an adjustment of the third pressure P3 in the third section 32c the delivery line 32 to a desired setpoint. In the exemplary embodiment of a powder conveying system shown here 30 becomes the third print P3 with the help of the control valve 48 controlled so that one in the unpacking system 106 prevailing pressure.

In principle, it is conceivable for the control valve 32 in the area of an inlet of the expansion tank 44 to arrange. In the exemplary embodiment of a powder conveying system shown here 30 is the control valve 32 however, downstream of the expansion tank 44 in the third section 32c the delivery line 32 arranged.

The vacuum conveyor 40 and the vacuum generator 42 are through a fourth section 32d the delivery line 32 connected with each other. In the fourth section 32d the delivery line 32 arises in the operation of the powder conveyor system 30 a fourth print P4 on. The fourth print P4 is slightly higher, ie slightly less negative than the first pressure P1 because the fourth section 32d the delivery line 32 Substantially powder-free carrier gas is already flowing through.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 3023227 B1 [0003]
• EP 3165303 B1 [0004]
• EP 3167984 B1 [0004, 0033]

Claims (14)

Powder conveyor system (30) for use in a system (100) for producing a three-dimensional workpiece (18) using a generative layer construction method, the powder conveyor system (30) comprising: - a delivery line (32), - A conveying device (38) arranged in the conveying line (32), which is set up to generate a first pressure (P1) which is lower in a first section (32a) of the conveying line (32) arranged upstream of the conveying device (38) as a second pressure (P2) in a second section (32b) of the delivery line (32) arranged downstream of the delivery device (38), - an expansion tank (44) arranged downstream of the delivery device (38) in the second section (32b) of the delivery line (32), the expansion tank (44) being set up to at least a part of the second section (32b) of the delivery line (32 ) flowing through medium, so that a third pressure (P3) is set in a third section (32c) of the delivery line (32) arranged downstream of the expansion tank (44), which pressure is lower than the second pressure (P2) in the second section ( 32b) the delivery line (32), and. - A control valve (48) which is set up to control the supply of a medium flowing through the second section (32b) of the delivery line (32) into the expansion tank (44) such that the third pressure (P3) is in the third section (32c) the delivery line (32) approximates a desired setpoint. Powder conveyor system (30) 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). Powder conveyor system (30) Claim 1 or 2 , wherein - the first pressure (P1) is a negative pressure lying below atmospheric pressure at sea level and / or - the second pressure (P2) is a positive pressure lying above atmospheric pressure at sea level and / or - the third pressure (P3) is a is positive pressure above atmospheric pressure at sea level. Powder conveyor system (30) according to one of the Claims 1 to 3 , wherein the surge tank (44) is a surge tank (44) with a variable receiving volume. Powder conveyor system (30) according to one of the Claims 1 to 4 wherein the expansion tank (44) consists at least in sections of a flexible, stretchable material and / or comprise a bellows (46). Powder conveyor system (30) according to one of the Claims 1 to 5 , wherein the control valve (48) is arranged downstream of the expansion tank (44) in the third section (32c) of the delivery line (32). Powder conveyor system (30) according to one of the Claims 1 to 6 , wherein the control valve (48) is designed in the form of a pinch valve or in the form of a proportionally regulated disc valve. Powder conveyor system (30) according to one of the Claims 1 to 7 wherein a powder / carrier gas mixture can flow through the delivery line (32) at least in its first section (32a) arranged upstream of the delivery device (38) and / or wherein the delivery line (32) is arranged at least in its downstream direction of the delivery device (38) essentially powder-free carrier gas can flow through the second section (32b) and / or wherein essentially powder-free carrier gas can flow through the delivery line (32) at least in its third section (32c) arranged downstream of the expansion tank (44). Powder conveyor system (30) Claim 8 , wherein the carrier gas is an inert gas. Powder conveyor system (30) according to one of the Claims 1 to 9 The conveyor device (38) comprises a vacuum conveyor (40) arranged in the conveyor line (32) and a vacuum generator (42) arranged downstream of the vacuum conveyor (40) in the conveyor line (32). Powder conveyor system (30) Claim 10 , wherein the powder conveying system (30) further comprises a storage container (43) connected to the vacuum conveyor (40), which is set up to convey powder (24) conveyed by the conveying device (38) through the first section (32a) of the conveying line (32) take. Powder conveyor system (30) Claim 10 or 11 , wherein the vacuum conveyor (40) and the vacuum generator (42) are connected to one another by a fourth section (32d) of the delivery line (32), in which a fourth pressure (P4) is established. System (100) for producing a three-dimensional workpiece (18) using a generative layer construction method, the at least one powder conveyor system (30) according to one of the Claims 1 to 12 includes. Appendix (100) to Claim 13 , wherein the system (100) an unpacking system (106) for Removing the three-dimensional workpiece (18) from a process chamber (12) of the system (100), wherein a first end of the delivery line (32) is connected to a powder outlet (34) of the unpacking system (106) and / or a second end of the Delivery line (32) is connected to a gas inlet (36) of the unpacking system (106).

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