Apparatus for producing three-dimensional workpieces and method for operating same

Abstract

The invention relates, inter alia, to a method for operating an apparatus (10) for producing three-dimensional workpieces (12) by subjecting layers of powder to electromagnetic radiation or particle radiation in a process chamber (14), wherein: the apparatus (10) has at least one powder conveying section (201, 202; T1, T2, T3) for conveyance and / or storage of a powder; the powder conveying section (201, 202; T1, T2, T3) has an inlet and an outlet; in an inertization step, an inert gas is fed into the powder conveying section (201, 202; T1, T2, T3) via the inlet and a gas mixture comprising the inert gas is discharged via the outlet; and an inert gas flow rate adaptation unit within the powder conveying section (201, 202; T1, T2, T3) is used to successively and / or continuously increase the flow rate of the inert gas and / or the flow rate of the gas mixture comprising the inert gas from a flow rate starting value, which is preferably 0 m / s, to a predetermined, preferably maximum, flow rate end value within a predetermined period of time.

Description

[0001] Device for the production of three-dimensional workpieces and method for operating the same

[0002] Description

[0003] The invention relates to a method for operating a device for producing three-dimensional workpieces by bombarding powder layers with electromagnetic radiation or particle radiation in a process chamber. The invention also relates to a device for producing three-dimensional workpieces by bombarding powder layers with electromagnetic radiation or particle radiation in a process chamber.

[0004] In the prior art, so-called powder bed processes, an additive manufacturing method, involve irradiating the top layer of a powder bed with an energy source in a process chamber. This causes the particles of the powder bed to bond together, for example, through sintering, welding, melting, or by triggering a chemical reaction. After irradiating a layer, for example, with electromagnetic radiation, another layer of powder is applied by a powder bed recoater, allowing another layer to be irradiated. These processes are repeated until the workpiece can be removed from the powder bed.

[0005] Powder management and handling are crucial in the manufacturing process, as new or processed powder is regularly supplied to the process area via powder tanks. Additionally, used powder is collected in powder tanks and then fed to a processing plant or device.

[0006] Powder bed fusion is an additive or generative layer-by-layer process for manufacturing three-dimensional workpieces. It uses powdered raw materials, particularly metallic and / or ceramics, to create complex, three-dimensional workpieces. A layer of raw material powder is applied to a substrate in a process chamber and, depending on the desired geometry of the workpiece, selectively exposed to laser radiation or particle radiation as electromagnetic radiation. The electromagnetic radiation penetrating the powder layer causes it to heat up, resulting in the fusing or sintering of the raw material powder particles. Further layers of raw material powder are then successively applied to an already solidified layer on the substrate until the finished workpiece has the desired shape and size.Raw material powder layers include, for example, ceramic, metal or plastic materials as well as material mixtures.

[0007] For example, EP 3 023 227 A1 describes a device for producing three-dimensional workpieces by powder bed fusion, wherein the device comprises a process chamber containing a carrier for the workpiece to be produced and a powder application device for applying a layer of raw material powder to the carrier. The process chamber is provided, for example, 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 circulation line, in which a conveying device for transporting the raw material powder through the powder circulation line is arranged, connects the powder outlet of the process chamber to the powder inlet of the process chamber.

[0008] The unsolidified and excess raw material powder removed from the carrier and the process chamber is generally preferably reused for the production of a three-dimensional workpiece. For example, the unsolidified raw material powder removed from the carrier can be directly fed into a powder circuit and returned to the process chamber via the powder circuit to build up further layers of the three-dimensional workpiece. Alternatively or additionally, the recovered unsolidified raw material powder can first be used in a further manufacturing process for another workpiece after being removed from the process chamber. Before its reuse for the production of a three-dimensional workpiece, the raw material powder can be processed in a powder preparation process and, for example, sieved.

[0009] When loose powder or raw powder is removed from the process chamber by means of an exhaust air stream via an outlet on the process chamber, for example by an extraction system, particles or the extracted powder are conveyed in the exhaust air through ducts to a storage area or powder tank. The particles or powder removed from the process chamber can then be conveyed to a powder separator via a duct or an exhaust air duct of an exhaust system. A high powder load can build up in the exhaust air duct, which can cause an exhaust air filter installed in the duct to become clogged with powder.

[0010] One object of the invention is to enable the trouble-free, and in particular durable, production of three-dimensional workpieces using an additive layer manufacturing process, with a particular aim of reducing contamination in an exhaust air system.

[0011] This problem is solved by a method for operating a device for producing three-dimensional workpieces by bombarding powder layers with electromagnetic radiation or particle radiation in a process chamber, wherein the device has at least one powder conveying section for conveying and / or storing a powder, in particular metal powder, wherein the powder conveying section has an inlet and an outlet, wherein in an inerting step an inert gas is introduced into the powder conveying section via the inlet and a gas mixture containing the inert gas is discharged via the outlet, wherein by means of an inert gas flow velocity adjustment unit within the powder conveying section the flow velocity of the inert gas and / or the flow velocity of the gas mixture containing the inert gas is adjusted from an initial flow velocity value, preferably 0 m / s,The flow velocity is increased successively, preferably in several steps, and / or continuously up to a predetermined, preferably maximum, final value within a predetermined time period, in particular an inlet time. The invention is based on the idea that, prior to the start of the production of a three-dimensional workpiece or prior to the commissioning of a device for the production of three-dimensional workpieces, loose powder or raw powder, which, for example, adheres to the inner walls of the powder conveying section, should not be loosened or detached from the inner walls in an inerting step, so that these powder particles are not removed from the powder conveying section, particularly by the discharge of the gas mixture from the outlet. This reduces the amount of adhering powder that would fall into a powder bed, and also reduces the risk ofthat adhering powder is carried along during inerting of the process chamber and the device.

[0012] According to the invention, in the inerting step the powder conveying section is flooded with inert gas, whereby the gas in the powder conveying section forms a gas mixture with the introduced inert gas. Thus, during the inerting step, a gas mixture that forms with the inert gas is discharged via the outlet.

[0013] The inerting step, among other things, uses the introduction of inert gas to create an inert atmosphere within the powder conveying sections and / or within the powder tank(s) before the start of the workpiece manufacturing process. This is achieved by introducing inert gas. Thus, the introduced inert gas and the resulting inert gas flow prevent or reduce the entrainment of powder particles by means of gentle flooding with inert gas. Furthermore, the inerting step according to the invention prevents powder particles adhering to the powder tank walls from being dislodged.In particular, according to the invention, the inerting step is carried out, for example, before the start and / or after the end of a bulk material conveying flow or bulk material flow for conveying raw material powder, which is preferably conveyed and used for the production of a three-dimensional workpiece by means of a device for the production of three-dimensional workpieces, and / or before the start and / or after the end of the manufacturing process of a three-dimensional workpiece.

[0014] Preferably, inert gases are understood to be protective gases, in particular inert gases that do not react with the powder used. For example, pure protective gases or noble gases such as argon, nitrogen, or helium are used for the inerting step of the powder conveying section.

[0015] During the inerting step, the flow velocity of the inert gas in the powder conveying section is gradually and / or continuously increased over a predetermined period from an initial flow velocity value to a predetermined, in particular maximum, final flow velocity value. A slow or gradual increase in the flow velocity of the inert gas within the powder conveying section ensures that as little powder as possible is stirred up within the discharge area and that the powder entrained by the flowing inert gas and the flowing gas mixture is removed from the powder conveying section, particularly via the outlet. According to the invention, the increase in the flow velocity of the inert gas from the initial flow velocity value to the maximum final flow velocity value is not abrupt.Within the scope of the invention, the temporal, and in particular continuous, profile of the flow velocity of the inert gas and / or the gas mixture containing the inert gas, from the initial flow velocity value, preferably 0 m / s, to a maximum final flow velocity value, is designed in an "S"-shaped or approximately "S"-shaped configuration. The temporal profile of the "S"-shaped flow velocity curve can be configured such that, starting with the initial flow velocity value, the derivative values, i.e., the slope of the temporal curve, increase to a maximum value and then decrease upon reaching the final flow velocity value. For example, the "S"-shaped temporal profile of the flow velocity has at least an approximation of a logistic function.If the flow velocity of the inert gas is successively increased in discrete steps or time intervals, the rate of change of the flow velocity, i.e., the gradient of the flow velocity, initially increases from the initial flow velocity value up to a maximum value. Subsequently, the rate of change of the flow velocity, i.e., the gradient of the shock velocity, decreases again until the flow velocity of the inert gas reaches its final value, in particular its maximum value.

[0016] Furthermore, the invention may also provide that the flow velocity is varied over time between the initial flow velocity value and the final flow velocity value, which is greater than the initial flow velocity value, by means of the inert gas flow velocity adjustment unit, wherein, for example, the flow velocity decreases after an increase or the flow velocity is increased again after a reduction.

[0017] For the introduction or introduction of the inert gas into the powder conveying section, the inert gas flow velocity adjustment unit has at least one controllable or adjustable valve.

[0018] Furthermore, by limiting the flow velocity of the inert gas to a maximum, and in particular predetermined, final flow velocity value, it is ensured that powder is not unintentionally conveyed from the powder conveying section and, in particular, does not enter the exhaust duct.

[0019] Within the scope of the invention, the powder conveying section is preferably part of a powder circuit of the device, wherein in one embodiment the powder conveying section has a powder tank for powder.

[0020] In particular, the method according to the invention reduces the powder load in one or more exhaust air lines, thereby preventing blockages or similar problems within the powder circuit. This enables the continuous operation of a device for the production of three-dimensional workpieces.

[0021] In a preferred embodiment of the method, the powder conveying section comprises at least one powder tank, preferably with a top surface, for receiving powder, in particular metal powder, and an inert gas supply line and an inert gas discharge line connected to the at least one powder tank. The inert gas is introduced into the powder tank via the inert gas supply line, and the gas mixture containing the inert gas is discharged from the powder tank via the inert gas discharge line. In a further embodiment, an opening at the end of the inert gas supply line is provided on the top surface of the powder tank, so that the inert gas supply line is connected to the powder tank. Furthermore, according to another aspect, the inert gas discharge line is connected to the powder tank via an opening in the region of the top surface of the powder tank.

[0022] Furthermore, in one embodiment of the method, it is preferred that the inert gas is introduced into the powder tank at the top of the at least one, in particular closed, powder tank and / or that the gas mixture containing the inert gas is discharged from the powder tank at the top of the powder tank.

[0023] According to another aspect, the method is characterized in that the powder conveying section has several powder tanks, preferably with a top surface, for receiving powder, in particular metal powder, wherein the powder tanks are supplied with the inert gas via the inert gas supply line in a sequential order or optionally in a parallel arrangement.

[0024] Preferably, in a further development, the powder tanks are connected in a parallel arrangement with a common inert gas discharge line section.

[0025] The method is advantageously further developed in that, in the case of a parallel arrangement of the powder tanks, the oxygen content of the discharged gas mixture in the respective inert gas discharge line is recorded by means of a respective oxygen sensor for measuring the oxygen.

[0026] Furthermore, according to one embodiment of the method, the oxygen content of the discharged gas mixture in the common inert gas discharge line section is recorded by means of an oxygen sensor, in particular a common and single one, for measuring the oxygen.

[0027] In one embodiment, if several powder tanks are arranged parallel to one another, with each of the parallel powder tanks being selectively supplied with inert gas via a common inert gas supply line, the invention provides that the powder tanks are connected to a common inert gas discharge line on the outlet side. In this embodiment, an oxygen sensor can be provided in the common inert gas discharge line to detect the oxygen content of the gas mixture being drawn from a powder tank via the inert gas discharge line. This ensures that a predetermined oxygen limit (as a safety threshold) is reached within each powder tank during the inerting process.

[0028] Depending on the type of use of the device, the maximum oxygen content within the inert gas discharge line should be less than 3.0 wt.%, in particular less than 2.5 wt.% or 2.0 wt.% or 1.5 wt.% or 1.0 wt.% or 0.5 wt.%.

[0029] In another embodiment, each of the parallel powder tanks is equipped with an oxygen sensor, allowing the oxygen content of each individual powder tank to be measured separately. This enables, for example, a parallel and simultaneous inerting step for the parallel powder tanks, ensuring that a predetermined oxygen limit is reached within each tank during the parallel inerting process.

[0030] In a further development of the process, it is also planned that the flow velocity of the inert gas is regulated by means of the inert gas flow velocity adjustment unit.

[0031] Furthermore, the method is characterized in one aspect by the fact that the flow rate of the inert gas, in particular the introduced gas, is regulated as a function of the oxygen content of the gas mixture in the inert gas discharge line or in the inert gas discharge line section, wherein in particular the regulation is set up such that the oxygen content in the gas mixture does not exceed a predetermined, in particular maximum, oxygen setpoint value on the outlet side of the powder conveying section.

[0032] According to a preferred embodiment of the method, the flow rate of the inert gas is regulated depending on the oxygen content in the gas mixture containing the inert gas in the inert gas discharge line or in the inert gas discharge line section, depending on the nature of the powder, in particular used for the production of a workpiece, and / or depending on the weight of the powder contained in the powder tank and / or depending on the fill level of the powder contained in the powder tank.

[0033] The predetermined maximum flow velocity depends on the type and density of the powder material used and / or on the powder level within the respective powder tank. For example, the maximum flow velocity may be predetermined to be higher when the powder tank is low than when it is high. Furthermore, the maximum flow velocity will be lower when the powder tank is full, for example, if the distance between the powder pile or bed and the tank inlet is small, compared to an empty powder tank. The powder tank level can be detected by a level sensor or similar device. For example, the level sensor may be a weighing cell, a distance sensor, or a photoelectric sensor. Additionally, a weight sensor is provided to measure the weight of the powder in the powder tank.

[0034] In a further development of the method, the inert gas flow velocity adjustment unit is provided that it has a flow sensor arranged on the inert gas supply line, wherein the flow velocity of the inert gas is detected by means of the flow sensor, and / or the inert gas flow velocity adjustment unit has a pressure regulator arranged in the inert gas supply line, wherein the pressure of the inert gas within the inert gas supply line is set, in particular regulated, by means of the pressure regulator, and / or that the inert gas flow velocity adjustment unit has a volume flow regulator arranged in the inert gas supply line, wherein the volume flow of the inert gas within the inert gas supply line is set, in particular regulated, by means of the volume flow regulator.

[0035] According to the invention, the flow sensor is provided for detecting the flow velocity of the inert gas or gas mixture. The flow sensor can, for example, be located in or on the inert gas supply line, preferably upstream of a pressure regulator and / or a volume flow controller located on the inert gas supply line. In another embodiment, the flow sensor is located in or on the inert gas discharge line.

[0036] The flow velocity of the inert gas and / or the gas mixture containing the inert gas introduced into the powder conveying section can be adjusted in one embodiment by the pressure regulator or the volume flow regulator, which are preferably arranged in or on the inert gas supply line. It is also possible within the scope of the invention for the flow velocity of the inert gas and / or the gas mixture to be adjusted by a combination of the pressure regulator and the volume flow regulator. Preferably, the pressure regulator and the volume flow regulator are arranged in series one after the other in the powder conveying section, particularly in or on the inert gas supply line.

[0037] Preferably, the method is designed so that during the inerting step, the velocity of the gas mixture at the outlet of the powder conveying section does not exceed a predetermined maximum flow velocity. In one embodiment, for example, the maximum flow velocity is less than 0.2 m / s, and in particular less than 0.1 m / s, when powder particles are present. If powder clouds are present within the powder conveying section, the maximum flow velocity can also be greater than 0.1 m / s or 0.2 m / s. In particular, the maximum flow velocity is selected from the range of 0.1 m / s, 0.2 m / s, 0.3 m / s, 0.4 m / s, 0.5 m / s, 0.6 m / s, 0.7 m / s, 0.8 m / s, 0.9 m / s up to 1.0 m / s.Furthermore, in a further development of the method, the flow velocity and / or the momentum, in particular the pressure momentum, of the inert gas is reduced in the powder conveying section by means of a diffuser unit and / or an inert gas flow control unit, especially when the inert gas is introduced into the at least one powder tank. Preferably, the diffuser unit is arranged at the end of the inert gas supply line at the inlet of a powder tank, which in particular ensures that the flow of the gas mixture introduced through the inlet of the powder tank is calmed. Thus, the velocity of the introduced gas mixture into the powder tank is reduced, which also reduces the momentum of the gas mixture, now with reduced flow velocity, acting on the powder or powder particles present in the powder tank.For example, in one embodiment, the diffuser unit is designed as a sintered filter element. With an inert gas flow guide unit, particularly at the inlet of the powder tank, the pressure pulses of the introduced gas mixture are also reduced. For example, in one embodiment, the inert gas flow guide unit is designed as a baffle plate or a guide plate for the gas mixture, or the like. In one embodiment, the inert gas flow guide unit can reduce the pressure pulses caused by the gas mixture on the powder particles or powder present in the powder tank by directing the gas mixture tangentially to the powder tank wall.

[0038] In a preferred embodiment of the method, the powder conveying section is subjected to at least one, preferably exclusively one, pressure pulse of the inert gas prior to the inerting step. By subjecting the powder conveying section to one or more pressure pulses of the inert gas, one or more initial pressure pulses are generated, so that adhering powder particles within the powder conveying section are removed from the inner walls and / or loosened. After the subjection of one or more pressure pulses, the inerting step according to the invention is only carried out after a predetermined time period has elapsed, during which the velocity of the gas mixture within the powder conveying section has stabilized.During the settling phase, the powder removed from the inner walls of the powder conveying section can, for example, fall into a powder bed of a powder tank, thereby reducing the amount of adhering powder or powder particles within the powder conveying section for the subsequent inerting step.

[0039] Furthermore, a further development of the process is characterized by the fact that the inerting step is carried out before the start of the production of a three-dimensional workpiece in the process space by commissioning the device for the production of a three-dimensional workpiece and / or that the inerting step is carried out after completion of the production of one or the three-dimensional workpiece in the process space by decommissioning the device for the production of a three-dimensional workpiece.

[0040] Furthermore, the problem is solved by a device for producing three-dimensional workpieces by bombarding powder layers with electromagnetic radiation or particle radiation in a process chamber, wherein the device has at least one powder conveying section for conveying and / or storing a powder, in particular metal powder, wherein the powder conveying section has an inlet and an outlet, wherein an inert gas is introduced into the powder conveying section via the inlet and a gas mixture containing the inert gas is discharged via the outlet, wherein an inert gas flow velocity adjustment unit is provided within the powder conveying section, wherein in particular the device is configured such that a process with the process steps described above is carried out or can be carried out in an inerting step.To avoid repetition, explicit reference is made to the above statements.

[0041] In a further development of the device, it is provided that the powder conveying section has at least one powder tank, preferably designed with a top, for receiving powder, in particular metal powder, and an inert gas supply line and an inert gas discharge line connected to the at least one powder tank, wherein the inert gas can be introduced or is introduced into the powder tank via the inert gas supply line and the inert gas and a gas mixture containing the inert gas can be discharged or is discharged from the powder tank via the inert gas discharge line.

[0042] Furthermore, one embodiment of the device is characterized by the fact that the inert gas can be introduced into the powder tank at the top of the at least one, in particular closed, powder tank, or is introduced into the powder tank, and / or the inert gas can be drawn out of the powder tank at the top of the powder tank, or is drawn out.

[0043] According to another aspect, the device is characterized in that the powder conveying section has several powder tanks, preferably with a top surface, for receiving powder, in particular metal powder, wherein the powder tanks can be or are supplied with the inert gas via the inert gas supply line in a sequential arrangement or the powder tanks can optionally be supplied with the inert gas in a parallel arrangement.

[0044] In particular, the powder tanks are connected to a common inert gas discharge line section when arranged in parallel.

[0045] Preferably, in a parallel arrangement of the powder tanks, an oxygen sensor is provided in each case to measure the oxygen content of the discharged gas mixture in the respective inert gas discharge line.

[0046] Furthermore, in an advantageous embodiment, it is provided that an oxygen sensor, in particular a common and single one, is provided for measuring the oxygen content of the discharged inert gas in the common inert gas discharge line section.

[0047] Advantageously, the inert gas flow velocity adjustment unit is set up to regulate the flow velocity of the inert gas.

[0048] Furthermore, the device is further developed in that the flow rate of the inert gas is adjustable or controlled depending on the oxygen content of the gas mixture in the inert gas discharge line or in the inert gas discharge line section, wherein in particular the control is arranged such that the oxygen content in the gas mixture does not exceed a predetermined, in particular maximum, oxygen setpoint value on the outlet side of the powder conveying section.According to a further embodiment, the device provides that the flow rate of the inert gas is adjustable or controlled depending on the oxygen content of the gas mixture in the inert gas discharge line or in the inert gas discharge line section, depending on the nature of the powder, in particular used for the manufacture of a workpiece, and / or depending on the weight of the powder contained in the powder tank and / or depending on the fill level of the powder contained in the powder tank.

[0049] One embodiment of the device is characterized in that the inert gas flow velocity adjustment unit has a flow sensor arranged on the inert gas supply line, wherein the flow velocity of the inert gas can be detected or is detected by means of the flow sensor, and / or the inert gas flow velocity adjustment unit has a pressure regulator arranged in the inert gas supply line, wherein the pressure of the inert gas within the inert gas supply line is set, in particular regulated, by means of the pressure regulator, and / or that the inert gas flow velocity adjustment unit has a volume flow regulator arranged in the inert gas supply line, wherein the volume flow of the inert gas within the inert gas supply line is set, in particular regulated, by means of the volume flow regulator.

[0050] Preferably, a diffuser unit and / or an inert gas flow control unit are provided in the powder conveying section, wherein the diffuser unit and / or the inert gas flow control unit are designed to reduce the flow velocity of the inert gas and / or the momentum, in particular pressure momentum, of the inert gas, especially when the inert gas is introduced into the at least one powder tank.

[0051] In particular, according to one embodiment, the device is arranged such that, prior to the execution of the inerting step, the powder conveying section is or is subjected to at least one, preferably exclusively one, pressure pulse of the inert gas.

[0052] Furthermore, in a further training, the device is set up so that the inerting step is carried out before the start of the production of a three-dimensional workpiece in the process room by commissioning the device for the production of a three-dimensional workpiece and / or so that the inerting step is carried out after completion of the production of one or the three-dimensional workpiece in the process room by decommissioning the device for the production of a three-dimensional workpiece.

[0053] Further features of the invention will become apparent from the description of embodiments according to the invention, together with the claims and the accompanying drawings. Embodiments according to the invention may fulfill individual features or a combination of several features.

[0054] Within the scope of the invention, features marked with "in particular" or "preferably" are to be understood as optional features.

[0055] The invention is described below, without limiting the general concept, with reference to exemplary embodiments and the drawings, whereby for all details of the invention not explained in detail in the text, explicit reference is made to the drawings. The drawings show:

[0056] Fig. 1 schematically shows a view of a device for producing a three-dimensional workpiece;

[0057] Fig. 2 schematically shows a section of a powder tank of a device for producing a three-dimensional workpiece according to a first embodiment;

[0058] Fig. 3 shows a schematic flowchart for controlling an inerting step of a device for manufacturing a three-dimensional workpiece;

[0059] Fig. 4a schematically shows the time course of the gas velocity in an inerting step according to the state of the art;

[0060] Fig. 4b schematically shows the time course of the gas velocity in an inerting step according to the invention;

[0061] Fig. 5 schematically shows in detail an arrangement of powder tanks arranged parallel to each other of a device for the production of three-dimensional workpieces according to a further embodiment and

[0062] Fig. 6 schematically shows in detail an arrangement of powder tanks arranged parallel to each other of a device for the production of three-dimensional workpieces according to a further embodiment.

[0063] In the drawings, identical or similar elements and / or parts are provided with the same reference numbers, so that a re-presentation is omitted.

[0064] Figure 1 schematically shows a device 10 for producing a three-dimensional workpiece 12 using an additive manufacturing process. In particular, the device 10 is configured for the additive manufacturing of three-dimensional workpieces by means of selective laser melting.

[0065] The device 10 has a process chamber 14, with a controllable deflection unit 16 arranged at the top of the process chamber 14. For selective laser melting, a laser 18 is provided to generate a laser beam, the laser beam being directed downwards into the process chamber 14 by means of the deflection unit 16. By controlling the laser beam, the workpiece 12 is produced, whereby powder material is not solidified by the laser beam in some areas.

[0066] The device 10 further comprises a vertically movable carrier 20 on its underside, on which the three-dimensional workpiece is manufactured and which is moved by means of a lifting unit 22. The device 10 also includes a powder intermediate storage 24 for raw material powder supply and a coater 26, which is horizontally controlled and movable within the process chamber 14 to apply (new) raw material powder layers after the carrier 20 has been lowered within the process chamber 14 by the layer height following completion of a previous layer.

[0067] Powder overflow tanks 28 are provided at the bottom of process chamber 14 to collect excess powder from the process chamber 14. The excess powder in the powder overflow tanks 28 is conveyed via a powder conveying line 30 to a powder sieving machine 32. After sieving the returned powder, the sieved powder is introduced into the powder storage tank 34. A storage tank 36 for new powder, particularly metal powder, is also provided to ensure a sufficient supply of powder in the powder storage tank 34 for the manufacturing process. Powder is drawn from the powder storage tank 34 to feed the intermediate powder storage tank 24.

[0068] For the manufacturing process, the device 10 also has a gas supply (not shown here) with which a protective gas, in particular an inert gas, is introduced into the process chamber 14 in order to provide a protective gas atmosphere for the manufacturing process of the three-dimensional workpiece 12.

[0069] Figure 2 shows a first embodiment of a powder tank T1 of a device for manufacturing a three-dimensional workpiece, as schematically depicted in Figure 1. The closed powder tank T1 is connected at its top via a tank inlet 101 to an inert gas supply line 201, through which an inert gas is introduced into the interior of the powder tank T1. The inert gas supply line 201 has a tank inlet valve E1. Preferably, the tank inlet valve E1 is designed as a proportional pressure regulating valve. Using a proportional pressure regulating valve as the tank inlet valve E1 makes it possible to easily control the pressure of the inert gas being introduced and thus also the velocity of the inert gas when it is introduced into the powder tank T1.

[0070] Upstream of the tank inlet valve E1, a volume flow regulator 211 for controlling the volume flow of the inert gas and a pressure regulator 213 for controlling the pressure of the inert gas in the inert gas supply line 201 are provided. Before the device 10 (see Fig. 1) is put into operation, an inert gas, such as helium, argon, etc., is introduced into the powder tank T1 via the inert gas supply line 201. Furthermore, a gas velocity sensor 215 is provided on the inert gas supply line 201 to measure the velocity of the gas through the inert gas supply line 201.

[0071] The upper tank inlet 101 is enlarged compared to the flow cross-section of the inert gas supply line 201 and has a diffuser element SF.

[0072] To discharge the inert gas introduced into powder tank T1, a tank outlet 102 is arranged at the top of the tank and is connected to an inert gas discharge line 202. The inert gas discharge line 202 serves to discharge the gas mixture containing the inert gas from powder tank T1 and has an outlet valve A1. Downstream of the outlet valve A1, an exhaust air filter 204 and an oxygen sensor 206 for measuring the oxygen content in the gas mixture discharged through the inert gas discharge line are arranged.

[0073] Before the device 10 is put into operation for the production of a three-dimensional workpiece, the inert gas supply line 201 is pressurized with an inert gas, with the outlet valve A1 open. At or before the start of the inerting step, the inlet valve E1 in the inert gas supply line 201 is closed. To prevent unintentional discharge of powder from the powder tank T1, the inlet valve E1 is continuously and slowly opened by a control unit (not shown here), thereby gradually increasing the flow velocity of the inert gas in the inert gas supply line 201 up to a maximum flow velocity. For this purpose, the pressure regulator 213 and the volume flow regulator 211 are adjusted accordingly.The inert gas is fed into the inert gas supply line 201 at point A and flows past the gas velocity sensor 215, then through the pressure regulator 213 and the volume flow regulator 211, as well as the open inlet valve E1. A sintered metal filter, for example, is arranged as a diffuser element SF in the serviced tank inlet 101 to calm the incoming inert gas. The incoming inert gas mixes with the gas in the powder tank T1 to form a gas mixture and is discharged from the powder tank T1 via the tank outlet 102 into the inert gas discharge line 202. The resulting inert gas flow passes through the powder tank T1 (see point B) and through the exhaust air filter 204 via the outlet valve A1. Subsequently, the gas mixture containing the inert gas flows past the oxygen measuring sensor 206 in the inert gas discharge line 202 to determine the oxygen content in the outgoing gas mixture.

[0074] Figure 3 schematically illustrates a flow diagram for controlling the gas velocity of the inert gas during the inerting step of the device 10. After the inerting step begins, in step S10, the outlet valve A1 is opened. Additionally, the inlet valve E1 in the inert gas supply line 201 is opened. Furthermore, the pressure regulator 213 and the volume flow regulator 211 are or are already open. Subsequently, after step S11, in step S12, the oxygen content in the exiting gas mixture in the inert gas discharge line 202 is measured by the oxygen sensor 206. The exiting gas mixture is then released into the atmosphere (see section C).

[0075] If the measured oxygen content in the gas mixture in the inert gas discharge line 202 exceeds a predetermined oxygen content setpoint, the subsequent process step S13 compares whether the velocity of the introduced inert gas into the inert gas supply line 201, measured by the gas velocity sensor 215, is below a maximum, and in particular predetermined, flow velocity limit. If the measured velocity of the inert gas is below the predetermined maximum flow velocity limit, the volume flow controller 211 is then opened further to increase the volume flow in step S14. Following this, step S15 determines whether the flow velocity of the inert gas in the inert gas supply line 201 has increased and whether the pressure of the inert gas in the inert gas supply line 201 is below a safety limit.If this is the case, steps S1 1 and S12 are then executed again.

[0076] If step S15 reveals that the flow rate of the inert gas is not increased and / or the pressure is not below the safety limit, the pressure is increased in the subsequent step S16. Steps S1 and S12 are then executed.

[0077] Steps S11 to S15 or S16 are repeated iteratively until, in step S12, it is determined that the measured oxygen content in the gas mixture falls below a threshold value (target oxygen content). Then, in a subsequent process step S20, the inlet valve E1 and the outlet valve A1 are closed. In the following process step S21, the pressure regulator 213 and the volume flow regulator 211 are closed. The inerting step then concludes with step S22.

[0078] Preferably, the control or regulation of the process steps during the execution of the inerting step, and thus before the creation of a three-dimensional workpiece, is carried out, for example, by means of a programmable logic controller (PLC) of the device 10 (not shown here). By using a programmable logic controller, the inerting step is executed automatically, thereby eliminating, for example, the need for manual adjustment of the pressure regulator or manual opening and closing of the valves.

[0079] Furthermore, within the scope of the invention, it is possible for the programmable logic controller to adjust the various devices before the inerting step according to the invention is carried out, such that at least one or more pressure pulses are generated by the inert gas within the inert gas supply line 201, the powder tank T1, and the inert gas discharge line 202, so that powder particles adhering to the inner walls are dislodged by means of the pressure pulses. A settling phase takes place before the inerting step is carried out.

[0080] The inerting step according to the invention ensures that the flow velocity of the introduced inert gas does not increase abruptly to a maximum final flow velocity value, but rather approaches the maximum final flow velocity value continuously or in several small steps.

[0081] Figure 4a schematically illustrates the temporal profile of the flow velocity according to the prior art. Here, upon opening the inlet valve, the maximum final flow velocity of the inert gas is reached within a short period, for example, a few milliseconds. Figure 4b shows the temporal profile of the inert gas flow velocity during the execution of the inerting step according to the invention. The temporal profile of the increasing flow velocity is not abrupt and has an "S"-shaped curve or a gradual progression according to a logistic function. The temporal profile of the "S"-shaped flow velocity curve is, for example, such that, starting with the initial flow velocity value of 0 m / s, the derivative values, i.e.,The slope of the time-dependent curve increases until it reaches a maximum value, and then the derivative values ​​decrease upon reaching the final flow velocity value Vmax. The flow velocity of the inert gas is gradually and continuously increased over a longer period to minimize the disturbance of powder or powder particles within the inert gas supply line 201 and / or in the powder tank T1.

[0082] By implementing the inerting step according to the invention, the powder load in the lines, powder tanks, exhaust filters, etc., is reduced, and potential blockages in the lines are avoided. Overall, this results in longer and trouble-free operation of the apparatus for the production of a three-dimensional workpiece. Furthermore, it ensures that less raw powder is lost, thus making more raw powder available for the manufacturing process.

[0083] Fig. 5 shows a further embodiment of an arrangement of several powder tanks T1, T2, T3 connected in parallel. Depending on the position of the inlet valves E1, E2, E3, these tanks are selectively connected to the inert gas supply line 201 to introduce inert gas from the inert gas supply line 201 into each of the powder tanks T1, T2, T3. Furthermore, outlet valves A1, A2, A3 are provided at the outlets of the powder tanks T1, T2, T3. These outlet valves are connected to the inert gas discharge line 202, depending on their position, to discharge the gas mixtures from the powder tanks T1, T2, T3. Preferably, the inlet valves E1, E2, E3 are configured as proportional pressure regulating valves.

[0084] In contrast to the embodiment shown in Fig. 2, in this embodiment the pressure of the gas mixture inside the powder tank T1 is measured by means of a pressure sensor 208. Furthermore, an oxygen sensor 209 is provided on the powder tank T1 to measure the oxygen content of the gas mixture inside the powder tank T1. A level sensor 210 is also arranged on the powder tank T1 to detect the fill level of a powder bed inside the powder tank T1. Even when considering the fill level of powder in a powder tank, it is possible within the scope of the invention to regulate or control the flow velocity of the inert gas accordingly and / or to determine the maximum final flow velocity value.

[0085] Figure 6 shows a further embodiment of an arrangement of powder tanks T1, T2, and T3 arranged parallel to one another. In this embodiment, the flow velocity of the gas mixture containing the inert gas, which is discharged from powder tank T1, is measured by means of a gas velocity sensor 216 arranged in the inert gas discharge line 202. Furthermore, the pressure of the gas mixture inside powder tank T1 is measured by means of the pressure sensor 208.

[0086] According to the invention, it is provided that during the execution of the inerting step, and thus before the commissioning or productive start-up of the device for the manufacture of a three-dimensional workpiece, the maximum flow velocity of the introduced inert gas into the inert gas supply line(s) and / or the maximum flow velocity of the gas mixture (after introduction of the inert gas) into the powder tank and / or in the inert gas discharge line is selected or predetermined, for example, from the range of 0.1 m / s, 0.2 m / s, 0.3 m / s, 0.4 m / s, 0.5 m / s, 0.6 m / s, 0.7 m / s, 0.8 m / s, 0.9 m / s to 1.0 m / s.

[0087] All features mentioned, including those discernible from the drawings alone as well as individual features disclosed in combination with other features, are considered essential to the invention, both individually and in combination. Inventive embodiments may be fulfilled by individual features or by a combination of several features.

[0088] List of references

[0089] 10 Device

[0090] 12 workpieces

[0091] 14 Process room

[0092] 16 Deflection unit

[0093] 18 lasers

[0094] 19 Laser beam

[0095] 20 carriers

[0096] 22 lifting units

[0097] 24 powder intermediate storage

[0098] 26 coaters

[0099] 28 Powder overflow tank

[0100] 30 Powder conveying line

[0101] 32 Powder sieve machine

[0102] 34 Buffer storage tank

[0103] 36 Storage tank

[0104] 101 Fuel tank inlet

[0105] 102 Tank outlet

[0106] 201 Supply line

[0107] 202 Drain line

[0108] 204 exhaust air filters

[0109] 206 Oxygen sensor

[0110] 208 Pressure sensor

[0111] 209 Oxygen sensor

[0112] 210 Level sensor

[0113] 21 1 Volume flow controller

[0114] 213 Pressure regulator

[0115] 215 gas speed measurement sensor

[0116] 216 Gas velocity measuring sensor A1, A2, A3 Exhaust valve

[0117] E1, E2, E3 Inlet valve

[0118] SF diffuser element

[0119] T1, T2, T3 Powder Tank

Claims

1. Method for operating a device (10) for producing three-dimensional workpieces (12) by applying electromagnetic radiation or particle radiation to powder layers in a process chamber (14), wherein the device (10) has at least one powder conveying section (201, 202; T1, T2, T3) for conveying and / or storing a powder, in particular metal powder, wherein the powder conveying section (201, 202; T1, T2, T3) has an inlet and an outlet, wherein in an inerting step an inert gas is introduced into the powder conveying section (201, 202; T1, T2, T3) via the inlet and a gas mixture containing the inert gas is discharged via the outlet, wherein the flow velocity of the powder conveying section (201, 202; T1, T2, T3) is adjusted by means of an inert gas flow velocity adjustment unit within the powder conveying section (201, 202; T1, T2, T3). Inert gas and / or the flow velocity of the gas mixture containing the inert gas is increased from an initial flow velocity value, preferably 0 m / s, successively, preferably in several steps, and / or continuously to a predetermined, preferably maximum, final flow velocity value within a predetermined time period, in particular inlet time period.

2. Method according to claim 1, characterized in that the powder conveying section (201, 202; T1, T2, T3) has at least one powder tank (T1, T2, T3) for receiving powder, in particular metal powder, preferably with a top surface, and an inert gas supply line (201) and an inert gas discharge line (202) connected to the at least one powder tank (T1, T2, T3), wherein the inert gas is introduced into the powder tank (T1, T2, T3) via the inert gas supply line (201) and the gas mixture containing the inert gas is discharged from the powder tank (T1, T2, T3) via the inert gas discharge line (202).

3. Method according to claim 2, characterized in that the inert gas is introduced into the powder tank (T1 , T2, T3) at the top of the at least one, in particular closed, powder tank (T1 , T2, T3) and / or the gas mixture containing the inert gas is discharged from the powder tank (T1 , T2, T3) at the top of the powder tank (T1 , T2, T3).

4. Method according to claim 2 or 3, characterized in that the powder conveying section (201, 202; T1, T2, T3) has several powder tanks (T1, T2, T3), preferably with a top surface, for receiving powder, in particular metal powder, wherein the powder tanks (T1 , T2, T3) are supplied with the inert gas via the inert gas supply line (201) in a sequential order or the powder tanks (T1 , T2, T3) are optionally supplied with the inert gas in a parallel arrangement.

5. Method according to claim 4, characterized in that the powder tanks (T1 , T2, T3) are connected in a parallel arrangement with a common inert gas discharge line section.

6. Method according to claim 4 or 5, characterized in that, in a parallel arrangement of the powder tanks (T1 , T2, T3), the oxygen content of the discharged gas mixture in the respective inert gas discharge line (202) is detected by means of a respective oxygen sensor (206, 209) for measuring the oxygen.

7. Method according to claim 4 or 5, characterized in that the oxygen content of the discharged gas mixture in the common inert gas discharge line section is detected by means of an oxygen sensor (206, 209), in particular a common and single oxygen sensor.

8. Method according to one of claims 1 to 7, characterized in that the flow velocity of the inert gas is controlled by means of the inert gas flow velocity adjustment unit.

9. Method according to claim 8, characterized in that the flow rate of the inert gas depends on the oxygen content of the gas mixture in the inert gas discharge line. tung (202) or in the inert gas discharge line section, wherein in particular the control is set up such that on the outlet side of the powder conveying section (201 , 202; T1 , T2, T3) the oxygen content in the gas mixture does not exceed a predetermined, in particular maximum, oxygen setpoint.

10. Method according to one of claims 1 to 9, characterized in that the flow rate of the inert gas is controlled as a function of the oxygen content in the gas mixture containing the inert gas in the inert gas discharge line (202) or in the inert gas discharge line section as a function of the nature of the powder, in particular used for the manufacture of a workpiece (12), and / or as a function of the weight of the powder contained in the powder tank (T1 , T2, T3) and / or as a function of the fill level of the powder contained in the powder tank (T1 , T2, T3).

11. Method according to any one of claims 2 to 10, characterized in that the inert gas flow velocity adjustment unit has a flow sensor (215) arranged on the inert gas supply line (201), wherein the flow velocity of the inert gas is detected by means of the flow sensor and / or the inert gas flow velocity adjustment unit has a pressure regulator (213) arranged in the inert gas supply line (201), wherein the pressure of the inert gas within the inert gas supply line (201) is set, in particular regulated, by means of the pressure regulator (213) and / or that the inert gas flow velocity adjustment unit has a volume flow controller (211) arranged in the inert gas supply line (201), wherein the volume flow of the inert gas within the inert gas supply line (201) is set, in particular regulated, by means of the volume flow controller (21 1 ).

12. Method according to one of claims 1 to 1 1 , characterized in that in the powder conveying section (201 , 202; T1 , T2, T3) the flow velocity of the inert gas and / or the momentum, in particular pressure momentum, of the inert gas, particularly when introducing the inert gas into the at least one powder tank (T1 , T2, T3), is reduced by means of a diffuser unit (SF) and / or an inert gas flow control unit.

13. Method according to one of claims 1 to 12, characterized in that, prior to the execution of the inerting step, the powder conveying section (201 , 202; T 1 , T2, T3) is subjected to at least one, preferably exclusively one, pressure pulse of the inert gas.

14. Method according to one of claims 1 to 13, characterized in that the inerting step is carried out before the start of the production of a three-dimensional workpiece (12) in the process space (14) by commissioning the device (10) for the production of a three-dimensional workpiece (12) and / or that the inerting step is carried out after completion of the production of one or the three-dimensional workpiece (12) in the process space (14) by decommissioning the device (10) for the production of a three-dimensional workpiece (12).

15. Device (10) for producing three-dimensional workpieces (12) by applying electromagnetic radiation or particle radiation to powder layers in a process chamber (14), wherein the device (10) has at least one Powder conveying section (201, 202; T1, T2, T3) for conveying and / or storing a powder, in particular metal powder, wherein the powder conveying section (201, 202; T1, T2, T3) has an inlet and an outlet, wherein an inert gas is introduced into the powder conveying section (201, 202; T1, T2, T3) via the inlet and a gas mixture containing the inert gas is discharged via the outlet, wherein an inert gas flow velocity adjustment unit is provided within the powder conveying section (201, 202; T1, T2, T3), wherein in particular the device (10) is configured such that a method according to one of claims 1 to 14 is carried out or can be carried out in an inerting step.

16. Device (10) according to claim 15, characterized in that the powder conveying section (201, 202; T1, T2, T3) has at least one powder tank (T1, T2, T3) for receiving powder, in particular metal powder, preferably with a top surface, and an inert gas supply line (201) and an inert gas discharge line (202) connected to the at least one powder tank (T1, T2, T3), wherein the inert gas can be introduced or is introduced into the powder tank (T1, T2, T3) via the inert gas supply line (201) and the inert gas and a gas mixture containing the inert gas can be discharged or is discharged from the powder tank (T1, T2, T3) via the inert gas discharge line (202).

17. Device (10) according to claim 16, characterized in that the inert gas is introduced into the powder tank (T1, T2, T3) at the top of the at least one, in particular closed, powder tank (T1, T2, T3). The inert gas can be introduced or is introduced into the powder tank (T1 , T2, T3) and / or the inert gas can be vented or is vented from the powder tank (T1 , T2, T3) at the top of the powder tank (T1 , T2, T3).

18. Device (10) according to claim 16 or 17, characterized in that the powder conveying section (201 , 202; T1 , T2, T3) has several powder tanks (T1 , T2, T3) for receiving powder, in particular metal powder, preferably having a top surface, wherein the powder tanks (T1 , T2, T3) can be or are supplied with the inert gas via the inert gas supply line (201) in a sequential arrangement or the powder tanks (T1 , T2, T3) can be optionally supplied with the inert gas via the inert gas supply line (201) in a parallel arrangement.

19. Device (10) according to claim 18, characterized in that the powder tanks (T 1 , T2, T3) are connected in a parallel arrangement with a common inert gas discharge line section.

20. Device (10) according to claim 18 or 19, characterized in that, in the case of a parallel arrangement of the powder tanks (T1 , T2, T3), an oxygen sensor (206, 209) is provided for measuring the oxygen content of the discharged gas mixture in the respective inert gas discharge line (202).

21. Device (10) according to claim 18 or 19, characterized in that an oxygen sensor (206, 209), in particular a common and single, is provided for measuring the oxygen content of the discharged inert gas in the common inert gas discharge line section.

22. Device (10) according to one of claims 15 to 21 , characterized in that the inert gas flow velocity adjustment unit is configured to regulate the flow velocity of the inert gas.

23. Device (10) according to claim 22, characterized in that the flow rate of the inert gas is adjustable or controlled as a function of the oxygen content of the gas mixture in the inert gas discharge line (202) or in the inert gas discharge line section, wherein in particular the control is arranged such that on the outlet side of the powder conveying section (201 , 202; T1 , T2, T3) the oxygen content in the gas mixture does not exceed a predetermined, in particular maximum, oxygen setpoint.

24. Device (10) according to one of claims 15 to 23, characterized in that the flow rate of the inert gas is adjustable or is controlled depending on the oxygen content of the gas mixture in the inert gas discharge line (202) or in the inert gas discharge line section depending on the nature of the powder, in particular used for the manufacture of a workpiece (12), and / or depending on the weight of the powder contained in the powder tank (T1 , T2, T3) and / or depending on the fill level of the powder contained in the powder tank (T1 , T2, T3).

25. Device (10) according to one of claims 16 to 24, characterized in that the inert gas flow velocity adjustment unit has a flow sensor (215) arranged on the inert gas supply line (201), wherein the flow velocity of the inert gas is detectable or is detected and / or the inert gas flow velocity adjustment unit has a pressure regulator (213) arranged in the inert gas supply line (201), wherein the pressure of the inert gas within the inert gas supply line (201) is set, in particular regulated, by means of the pressure regulator (213) and / or that the inert gas flow velocity adjustment unit has a volume flow regulator (211) arranged in the inert gas supply line (201), wherein the volume flow (211) of the inert gas within the inert gas supply line (201) is set, in particular regulated, by means of the volume flow regulator (211).

26. Device (10) according to one of claims 15 to 25, characterized in that a diffuser unit (SF) and / or an inert gas flow control unit are provided in the powder conveying section (201 , 202; T1 , T2, T3), wherein the diffuser unit (SF) and / or the inert gas flow control unit are configured to reduce the flow velocity of the inert gas and / or the momentum, in particular pressure momentum, of the inert gas, especially when the inert gas is introduced into the at least one powder tank (T1 , T2, T3).

27. Device (10) according to one of claims 15 to 26, characterized in that the device (10) is arranged such that, prior to the execution of the inerting step, the powder conveying section (201 , 202; T 1 , T2, T3) is or is subjected to at least one, preferably exclusively one, pressure pulse of the inert gas.

28. Device (10) according to one of claims 15 to 27, characterized in that the device (10) is configured such that the inerting step is carried out before the start of the production of a three-dimensional workpiece (12) in the process room (14) by commissioning the device (10) for the production of a three-dimensional workpiece (12) and / or that the inerting step is carried out after completion of the production of one or the three-dimensional workpiece (12) in the process room (14) by decommissioning the device (10) for the production of a three-dimensional workpiece (12).

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