Filter system with individually separable filter chambers

Abstract

The invention relates to a device for providing a process gas atmosphere in a process chamber (3) of an additive manufacturing device during a method for manufacturing a three-dimensional object (2), having a gas circulation system, the gas circulation system has a closed gas circuit during operation for a process gas conducted through the process chamber (3), a filter system (40) having a plurality of filter chambers (41a, 41b, 41c) is arranged in the closed gas circuit, there are at least three filter chambers, and the filter chambers (41a, 41b, 41c) are arranged in the closed gas circuit. Wherein each filter chamber has at least one filter element (43a, 43b, 43c) for filtering particles in the gas circuit, and there is a gas control device (80) for controlling the gas circuit, which gas control device is arranged such that it can separate some filter chambers (41a, 41b, 41c) from the gas circuit during the ongoing manufacturing process, it can be ensured that the number of filter chambers remaining in the gas circuit at least temporarily, preferably continuously, exceeds the number of filter chambers separated from the gas circuit.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for providing a process gas atmosphere during an additive manufacturing method, as well as an additive manufacturing method suitable therefor and an additive manufacturing apparatus suitable therefor. Background Art

[0002] Devices and methods for additive manufacturing of three-dimensional objects are used, for example, in methods known as “rapid prototyping”, “rapid tooling” and “additive manufacturing”. One example of such a method is known as “selective laser sintering” or “selective laser melting”. In this case, layers of a usually powdered building material are repeatedly applied and the building material in each layer is selectively solidified by selectively irradiating the locations corresponding to the cross section of the object to be manufactured in this layer with a laser beam, for example in that the building material is partially or completely melted at these locations by the energy provided by the laser beam and the melt subsequently solidifies during cooling. Further details are described, for example, in EP 2 978 589 B1.

[0003] During additive manufacturing, a process gas atmosphere is usually maintained in a process chamber in which the build material is selectively treated with the aid of radiation. The process gas atmosphere is usually an inert gas atmosphere (also called a "protective gas atmosphere"), since some build materials, in particular when they contain metals, tend to oxidize in the presence of high temperatures, which would prevent the formation of an object, or at least the formation of an object with the desired material structure. For example, titanium may begin to burn uncontrollably in the presence of oxygen.

[0004] During the production process, parts of the building material usually evaporate due to the irradiation, which results in the formation of condensates after the generated vapor solidifies again. In addition, parts of the building material are often also blown up. In addition, irradiation can produce splashes. This usually refers to solidified droplets of the melt of the building material, which have a diameter of, for example, 20 to 300 μm. For example, when the laser beam penetrates, splashes are ejected from the resulting melt or molten pool.

[0005] The effects mentioned when irradiating the building material also lead to impurities in the process gas atmosphere, which can have a negative impact on the additive manufacturing process and, in particular, can reduce the quality of the manufactured object. For example, a (scanning) laser beam that scans the building material can be absorbed, scattered or deflected by impurities contained in the process gas atmosphere. In addition, impurities can also be deposited on the coupling window for the laser beam or on the surface of the building material layer. In order to meet the high quality and efficiency requirements for the manufacturing process, such impurities must therefore be removed from the process chamber as quickly as possible, and for this purpose a gas flow is usually produced in the process chamber.

[0006] In order to reduce resource consumption, process gases, such as argon, are guided in a loop. However, this requires cleaning by filtering out impurities before the process gas is supplied again to the process chamber. For this purpose, a filter device with suitable filter elements is arranged in the process gas loop. Since the filter elements used become increasingly contaminated during operation, they must be replaced or substituted at regular intervals. For this purpose, the process gas circulation is interrupted and the filter element is removed. After the new filter element is inserted, the process gas loop is restarted.

[0007] In order to further reduce the resource consumption, DE 10 2014 207 160 A1 proposes to carry out regular cleaning of the filter element by means of gas pressure surges in order to extend the replacement intervals of the filter element.

[0008] EP 3 321 071 A1 is directed to the problem that when replacing a filter element, the operation of an additive manufacturing device must be interrupted, because the additive manufacturing process can only be performed when filtering the process gas flow. In order to solve this problem, a switching device is proposed, by means of which a plurality of filter modules can be individually switched into an operating state and a non-operating state, in which the process gas can flow through the plurality of filter modules, and in which the process gas cannot flow through the plurality of filter modules. This ensures that the operation of the additive manufacturing device does not need to be interrupted during the replacement of the filter element.

[0009] The present inventors have discovered that the cleaning and replacement process of the filter element may result in quality-impairing drift and discoloration of the manufactured object. Summary of the invention

[0010] It is therefore an object of the present invention to provide a device and a method by means of which the quality of manufactured objects can be improved.

[0011] The object is achieved by a device and a method for providing a process gas atmosphere according to claims 1 and 14 and by an additive manufacturing device and an additive manufacturing method according to claims 13 and 20. Further developments of the invention are described in the dependent claims. The methods can also be developed by the device features described in the description or in the dependent device claims. Likewise, the devices can also be developed by the method features described in the description or in the dependent method claims.

[0012] According to the invention, a device for providing a process gas atmosphere in a processing chamber of an additive manufacturing device during a method for manufacturing a three-dimensional object, in which the object is manufactured in the manufacturing method by applying a building material layer by layer and solidifying the building material by delivering radiation energy to a solidification location in each layer corresponding to a cross-section of the object in the layer, the device has a gas circulation system, the gas circulation system has a gas circuit that is closed during operation for a process gas guided through the processing chamber, wherein a filter system with a plurality of filter chambers is arranged in the closed gas circuit, characterized in that there are at least three filter chambers, each of which has at least one filter element for filtering particles in the gas circuit, and there is a gas control device for controlling the gas circuit, the gas control device being arranged so that it can separate some filter chambers from the gas circuit during the ongoing manufacturing method, and thereby can ensure that the number of filter chambers remaining in the gas circuit at least temporarily, preferably continuously, exceeds the number of filter chambers separated from the gas circuit.

[0013] The additive manufacturing devices to which the invention relates are in particular devices suitable for the generative production of three-dimensional objects, in particular the production of three-dimensional objects from metal-containing construction materials. This relates in particular to such production devices in which objects are constructed layer by layer, i.e., for example, laser melting devices and laser sintering devices. For supplying the radiation energy, for example, one or more gas lasers or solid-state lasers or any other type of laser can be used, for example, laser diodes, in particular VCSELs (vertical cavity surface emitting lasers) or VECSELs (vertical external cavity surface emitting lasers) or a row of such lasers can also be used. For example, other light sources, electron beams or any other energy source or radiation source suitable for curing the construction material can be used instead of the laser.

[0014] Furthermore, it can also be used in non-layer-by-layer generative devices that operate at high process temperatures in order to melt building materials with high melting points, such as laser cladding devices. In all of the above cases, it is also possible to use devices in which an electron beam is used to introduce the energy required to melt the building material instead of a device with a laser.

[0015] Preferably, metal-containing materials of construction are used, for example iron- and / or titanium-containing materials of construction, but also copper-, magnesium-, aluminum-, tungsten-, cobalt-, chromium- and / or nickel-containing materials can be used. The elements can be present in almost pure form (together accounting for more than 80 weight percent of the material of construction) or as constituents of an alloy.

[0016] The process chamber is considered to be that area of ​​the production plant in which the additive manufacturing takes place and which is enclosed by a jacket so that a gas atmosphere different from that of the environment of the production plant can be maintained inside it. The process gas inside the process chamber can be in particular an inert gas, i.e., for example nitrogen, helium or argon, wherein the process gas can also contain a mixture of different chemical elements and the pressure in the process chamber can optionally also be below atmospheric pressure. In particular, it is also conceivable that the process gas has other components in addition to inert gases.

[0017] The gas circulation system has a gas conveying device, such as a high-pressure fan or a centrifugal fan, and a gas line system, by means of which the gas can be conducted through the process chamber in a closed circuit, so that a gas flow can be provided in the process chamber during the production process.

[0018] When the gas circulation system is in operation, the gas delivery device ensures a continuous process gas flow, wherein the process gas that has been guided through the treatment chamber is supplied to the filter system and from the filter system to the treatment chamber, thereby forming a closed gas circuit. The filter system here comprises at least one filter chamber through which the process gas flow is guided. The side of the filter chamber on which the process gas flow enters the filter chamber is also referred to as the untreated gas side. The side of the filter chamber on which the process gas flow leaves the filter chamber again after flowing through the filter element is also referred to as the clean gas side.

[0019] At least one filter element is present in each filter chamber, which means that two or more filter elements may also be present in the filter chamber, which filter elements can be serviced after the filter chamber has been isolated from the gas circuit.

[0020] The gas control device may include a CPU, the operation of which is controlled by a computer program (software). The computer program may be stored on a storage medium, from which the computer program may be downloaded to the gas control device. Alternatively, the gas control device may also be implemented in the form of a control program, which is executed by a control unit for controlling the additive manufacturing process in the additive manufacturing device. A prerequisite for this is that the corresponding control unit is connected to the hardware components by means of a connecting line or wirelessly, by means of which the filter chamber can be separated from the gas circuit. The wireless connection can be achieved by radio, WLAN, NFC, Bluetooth, etc., in that the control unit has a corresponding receiver and transmitter.

[0021] For example, it can be achieved by a control unit included in the gas control device to ensure that the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit. It has been found that by this ensuring, the quality of the manufactured object can be improved. A preliminary explanation for this is as follows:

[0022] In order to manufacture high-quality objects, the manufacturing process must be carried out as uninterrupted as possible, and in addition, fluctuations in the process gas flow must be minimized during the ongoing manufacturing process. In other words, the volume flow in the gas circuit should be as constant as possible. When multiple filter chambers are arranged in parallel with each other in a closed gas circuit, each filter chamber produces a total flow resistance due to the filters arranged therein, and the total flow resistance is the result of the parallel connection of the flow resistances of the individual filter chambers. If the individual filter chambers are separated from the gas circuit, the total flow resistance will change suddenly. It is precisely in the case of large volume flows that the gas delivery device has limited ability to match the delivery power to the changed total flow resistance. Therefore, this will cause fluctuations in the volume flow flowing through the processing chamber and therefore cause discontinuities or structural heterogeneities in the manufactured objects.

[0023] Large volume flows are usually accompanied by high velocities of the process gas flowing through the process chamber. By means of the method according to the invention, it is ensured that the process gas velocity remains essentially constant, i.e. fluctuates at most within a small range. Thus, when the manufacturing process is carried out in the manner according to the invention in the process chamber of the additive manufacturing device, it is ensured that impurities (splashes, fumes, etc.) generated during the construction process are continuously discharged. However, for example, when no construction process is carried out in the process chamber, it is possible to abandon the requirement to ensure that the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers separated from the gas circuit in order to avoid contamination of the process chamber from the outside, but to still maintain a process gas flow in the process chamber even if the process gas velocity is reduced.

[0024] By ensuring that the number of filter cavities remaining in the gas circuit exceeds the number of filter cavities separated from the gas circuit, fluctuations in the volume flow when separating the filter cavities can be limited and thus a high quality of the manufactured object can be ensured. This applies in particular to large volume flows, which have the advantage of being able to increase the surface area of ​​the filter, thereby extending the maintenance intervals of the filter element (e.g. cleaning or replacement of the filter element).

[0025] For example, ensuring that the number of filter chambers remaining in the gas circuit exceeds the number of filter chambers isolated from the gas circuit can be achieved in the following way: before isolating the filter chambers from the process gas flow, it is checked whether the number of filter chambers remaining in the gas circuit due to the isolation no longer exceeds the number of filter chambers isolated from the gas circuit, and the isolation is only carried out if this is not the case. In other words, the gas control device prevents more than a maximum number of filter chambers from being separated from the process gas flow at a certain time. The value of this maximum number can in particular be stored in a memory and can be stored in the total number N total When changing, it can match the filter chamber connected to the processing chamber.

[0026] It should also be noted that in this application, reference is often made to the cleaning or replacement of the filter element with regard to the invention, but the invention is not limited thereto. On the contrary, the invention has advantages in all cases, regardless of the reasons, in which the filter chamber is always to be separated from the gas circuit or is to be introduced additionally into the gas circuit.

[0027] In a preferred embodiment, there are at least five filter chambers, each of which has at least one filter element, and the device is designed to isolate a plurality of filter chambers from the gas circuit simultaneously for maintenance processes (e.g., cleaning or replacing filter elements). Maintenance can thus be performed more efficiently, since the filter elements can be cleaned or replaced in parallel.

[0028] In a special embodiment, each of the filter chambers has at least one filter element for filtering particles in the gas circuit, which filter element can be cleaned and / or replaced by a gas pressure surge.

[0029] Over time, a filter material layer consisting of a layer of compressed and / or mutually adhered particles is formed on the filter element, which layer is usually called a "filter cake". This filter cake hinders the flow of gas and causes the pressure drop on the filter to continue to increase. Therefore, the most common maintenance process for the filter chamber is to reduce the pressure drop on the filter chamber. This is usually achieved by cleaning the filter element with the help of gas pressure shock. Additionally or alternatively, the filter element with deposits can be removed from the filter chamber and replaced with other filter elements without deposits. For this purpose, the filter chamber must usually be opened, so that components of the ambient atmosphere may enter the opened filter chamber and reach the filter element to be replaced. The filter element itself preferably does not have a housing for preventing ambient air from entering the filter element when the filter element is replaced.

[0030] In a special design, the plurality of filter cavities have substantially the same volume; and / or

[0031] The filter elements have substantially the same filter surface and / or the same filter medium; and / or

[0032] The inlet pipes and the outlet pipes respectively connected to the plurality of filter chambers have substantially the same opening cross-sections.

[0033] In other words, the filter chambers in which the filter elements without sediment are arranged preferably have the same flow resistance. This is further preferably applicable to each filter chamber combination consisting of a filter chamber and an inlet line and an outlet line leading to / from the filter chamber separately. Here, the filter chamber combination includes all other elements in addition to the filter chamber, which are arranged together with the filter chamber in parallel to other filter chamber combinations in the gas circuit. Here, the flow resistance of the inlet line and the outlet line is determined in particular by the (minimum) opening cross-sectional area. For example, the same flow resistance can be achieved in the following way, that is, all filter chambers (especially all filter elements) have the same structure, so that when the filter chambers are arranged in parallel to each other in the air flow, the contribution of the filter chambers to the total flow resistance is the same. In particular, the filter elements of all filter chambers can also have the same filter medium, which means that these filter elements are composed of the same material (for example, a fabric filter or a PE sintered filter with 20 μm polyester fibers) and / or belong to the same filter grade.

[0034] In a particular design, the gas control device is arranged to ensure that, during an ongoing manufacturing method, the ratio of the number of filter chambers that are not isolated from the process gas circuit to the number of filter chambers that are isolated from the process gas circuit is at least temporarily, preferably continuously, greater than or equal to a minimum value of 55:45, preferably 60:40, more preferably 2:1, more preferably 70:30, even more preferably 3:1, and particularly preferably 4:1.

[0035] The greater the ratio of filter chambers that are not isolated from the process gas circuit to filter chambers that are isolated from the process gas circuit, that is, the greater the ratio of filter chambers that are in an operating state of filtering process gas to filter chambers that are not in an operating state of filtering process gas, the smaller the fluctuations in the volume flow caused by the isolation of some filter chambers. It is therefore preferred that, precisely with the increase in the number of filter chambers (the increase in this number is in principle unlimited, i.e., it can basically even reach several hundred or thousands), a minimum value can be preset for the ratio, which the ratio must not fall below. For example, a minimum value of 3:2 can be preset when there are 5 filter chambers, a minimum value of 60:40 can be preset when there are 10 filter chambers, or a minimum value of 55:45 can be preset when there are 20 filter chambers.

[0036] In a special embodiment, all filter chambers arranged in the gas circuit are always arranged in parallel with one another.

[0037] It is also possible that a plurality of filter chambers are arranged one behind the other and that these filter chambers arranged one behind the other are arranged in parallel with other filter chambers or other filter chambers arranged one behind the other. In the case of a filter chamber arrangement one behind the other, the filter element located upstream can pre-filter the process gas, so that the filter element located downstream can perform fine filtering. It is also possible, for example, that when the filter chambers are arranged one behind the other, only the filter element located upstream is designed to be cleanable and / or replaceable.

[0038] In a special embodiment, the at least three filter chambers are subchambers of one or more main chambers of the filter system which are separated in a gas-tight manner from one another.

[0039] For the total flow resistance that is important within the scope of the present invention, it is unimportant whether the multiple filter chambers are spatially separated from each other or whether the multiple filter chambers are subchambers of a single chamber (main chamber). In the latter case, it is only important that the subchambers are separated from each other in an airtight manner, so that the individual filter chambers can be isolated independently from each other with respect to the gas circuit. Similarly, if the filter chambers are spatially separated from each other, it can be ensured that the flow resistances of the individual filter chambers do not differ from each other due to excessive differences in the flow resistances of the inlet and outlet lines of the individual filter chambers. Finally, a plurality of main chambers separated from each other in space can also be provided, the main chamber having sub-areas therein, wherein each sub-area is used as a filter chamber.

[0040] In a special embodiment, a switching unit is provided upstream and / or downstream for each of the at least three filter chambers, by means of which the filter chamber can be isolated from the gas circuit separately from the other filter chambers.

[0041] The gas control device is preferably designed so that it can control one or more switch units or valves upstream and / or one or more switch units or valves downstream of the plurality of filter chambers. Thus, for example during maintenance of the filter chambers, the gas control device can isolate one or more filter chambers from the gas circuit so that the process gas flows from this moment on through the filter chambers that are still retained in the gas circuit. The switch unit can in particular be a controllable valve, such as an extrusion valve. The switch unit can be controlled via a connecting line or wirelessly. This can be done independently of the manufacturing method running in the additive manufacturing device.

[0042] Although multiple filter chambers can be isolated together with respect to the gas circuit, greater freedom is provided if each filter chamber can be individually isolated from the gas circuit.

[0043] In a special embodiment, a pressure sensor is provided upstream and downstream of each of the at least three filter chambers, so that a pressure difference between the raw gas side and the clean gas side of the filter element in the filter chamber can be determined.

[0044] By providing a pressure sensor for each of the filter chambers, the occupancy of the filter element can be derived from the pressure difference for each filter chamber individually and it can be determined individually for each filter chamber whether the filter element must be cleaned or replaced. Even if, in theory, other components besides the filter element can influence the pressure difference determined by means of the pressure sensor, the filter element still plays a major role in determining the existing pressure difference.

[0045] In a special design scheme, in order to determine the pressure difference between the raw gas side and the clean gas side of multiple filter chambers, preferably all filter chambers, a pressure sensor is arranged upstream of the branching part of the input pipeline of the raw gas to the multiple filter chambers, and a pressure sensor is arranged downstream of the confluence of the discharge pipeline of the clean gas from the multiple filter chambers, and the pressure difference is determined by comparing the pressure values ​​of the two pressure sensors.

[0046] The reduction in the number of pressure sensors results in lower cost of the device.

[0047] In a more specific design, the gas control device is connected to pressure sensors upstream and downstream of the filter chamber via signal connections and is configured to initiate cleaning of the filter element between these pressure sensors if the pressure difference received by the pressure sensors exceeds a preset maximum value.

[0048] In this way of handling, the device can autonomously ensure the maintenance of the filter element by cleaning or replacement. The signal connection can be a signal line or a wireless connection (for example, by radio, WLAN, NFC, Bluetooth, etc.), which allows communication between the gas control device and the pressure sensor, in particular the transmission of the sensor value to the gas control device. The pressure difference determined upstream and downstream by means of two pressure sensors generally provides information about the occupancy state of the filter element arranged between the pressure sensors. If multiple filter chambers are arranged between the two pressure sensors, the filter element can be cleaned or replaced when a preset maximum value of all these filter chambers is exceeded, taking into account the number of filter chambers retained in the gas circuit according to the present invention.

[0049] In a special design, a sensor for determining the volume flow of the process gas in a closed gas circuit is arranged downstream of the filter system, and the sensor is connected to the gas control device via a signal connection, wherein the gas control device is configured to start cleaning the filter element if the value of the volume flow received by the sensor is lower than a preset minimum value.

[0050] The excessively large drop in the volume flow of process gas downstream of the filter system indicates that the filter system has too large a flow resistance due to the occupied filter element. The excessive drop in the volume flow may lead to insufficient discharge of impurities from the processing chamber. When the flow sensor is connected to the gas control device through a signal connection, the device can automatically eliminate the undesirable fluctuations of the volume flow (and thus improve the quality of the manufactured object). In addition to the pressure sensor for determining the pressure difference upstream and downstream of the filter chamber, the sensor for determining the volume flow can be used as an alternative or additional safeguard to start the cleaning or replacement of the filter element. It can also be considered that the volume flow sensor is not arranged downstream of the entire filter system, but is arranged downstream of a filter chamber or downstream of the confluence of the discharge pipeline of multiple filter chambers, so as to replace or supplement the pressure sensor upstream and downstream of the filter chamber in this way. If the pressure difference value applied to each filter chamber is considered in addition to the value of the sensor for determining the volume flow, it can be determined quite differently by the joint action of the information of the pressure sensor and the sensor for the volume flow, when to clean or replace which filter elements.

[0051] In a special embodiment, the gas circulation system has a fan.

[0052] The fan of the gas delivery system may in particular be a high-pressure fan. In particular, the gas delivery system should preferably be designed such that if the flow resistance changes suddenly, for example due to the separation of the filter chamber from the gas circuit or the introduction of the filter chamber into the gas circuit, the gas delivery system can react sufficiently quickly to the change in the flow resistance (the volume flow can be kept sufficiently constant). In particular, the fan may be a centrifugal fan.

[0053] The additive manufacturing device according to the invention having a process chamber for producing a three-dimensional object has the device according to the invention for providing a process gas atmosphere.

[0054] This additive manufacturing device allows the manufacture of objects with higher quality.

[0055] According to the method of the present invention, a process gas atmosphere is provided in a processing chamber of an additive manufacturing device during a method for manufacturing a three-dimensional object. In this manufacturing method, the object is manufactured by applying a building material layer by layer and solidifying the building material by delivering radiation energy to a solidification location in each layer corresponding to a cross-section of the object in the layer. In the method for providing a process gas atmosphere, a process gas guided through the processing chamber is moved in a closed gas circuit by means of a gas circulation system. In the closed gas circuit, a filter system with a plurality of filter chambers is arranged, characterized in that there are at least three filter chambers, each of which has at least one filter element for filtering particles in the gas circuit, the filter element being cleanable by a gas pressure shock, and some of the filter chambers are separated from the gas circuit during the ongoing manufacturing method, wherein it is ensured that the number of filter chambers remaining in the gas circuit at least temporarily, preferably continuously, exceeds the number of filter chambers separated from the gas circuit.

[0056] With regard to the details and advantages of this method for providing a process gas atmosphere, the above statements regarding the corresponding device for providing a process gas atmosphere also apply.

[0057] In a special embodiment, in a filter chamber arranged in the gas circuit, a pressure difference is determined which is applied to a filter element arranged in the filter chamber, and the filter element is cleaned when the determined pressure difference exceeds a predefined maximum value.

[0058] In this manner, maintenance of the filter element by cleaning or replacing the filter element can be ensured, in particular, automatically during the manufacturing method, without the need for user monitoring of the manufacturing method. The pressure difference determined by means of pressure sensors upstream and downstream of the filter chamber provides information about the occupancy state of the filter element arranged between the pressure sensors. If exactly one filter chamber is arranged between two pressure sensors, based on which the pressure difference is determined, the occupancy state can be determined in great detail. If a plurality of filter chambers are arranged between two pressure sensors, based on which the pressure difference is determined, the filter element can be cleaned or replaced when a preset maximum value of all these filter chambers is exceeded, taking into account the number of filter chambers remaining in the gas circuit according to the invention.

[0059] In a special embodiment, the process gas is moved in a closed gas circuit at a volume flow rate that exceeds 50 m 3 / h, preferably 100 m 3 / h, preferably 200 m 3 / h and / or less than 2000m 3 / h, preferably 500 m 3 / h, preferably 400 m3 / h.

[0060] From the point of view of optimally removing impurities from the process gas atmosphere in the treatment chamber which are generated by irradiating the building material, it is desirable to select a volume flow density value which is as high as possible. On the other hand, high volume flow density values ​​lead to increased wind-up of the building material. In practice, therefore, the target value of the volume flow density is adjusted as a function of the parameters selected when irradiating the building material and as a function of the building material used. In this context, it is ensured by the method according to the invention that the percentage fluctuations of the volume flow remain within limits.

[0061] In a special embodiment, a value for the volume flow of the process gas in a closed gas circuit downstream of the filter system is determined, and the filter element is cleaned if the determined value for the volume flow falls below a predefined minimum value.

[0062] By directly monitoring the volume flow of the process gas, it is possible to directly detect whether a volume flow value range to be maintained for producing objects with high quality has been exceeded. In this way, the occupancy state of the filter element in the filter chamber can be determined independently of the detection of the filter chamber pressure difference.

[0063] In a special embodiment, the filter system is connected to at least two process chambers of some additive manufacturing devices, wherein each process chamber is particularly preferably equipped with at least one centrifuge, wherein the method for manufacturing a three-dimensional object is carried out in each of the at least two process chambers with temporal overlap. The construction materials used in the process chambers can all be identical or can also be different from one another. In particular, the filter system is fluidically connected to at least two process chambers. The term "fluidically connected" should be understood here to mean that the connection is designed so that process gas can flow from the filter system to the additive manufacturing device and vice versa.

[0064] In particular, the gas circuit can be designed so that the filtered process gas flow from the filter system is split so as to flow through a plurality of process chambers in parallel. Before the process gas to be filtered enters the filter system, the partial gas flows of the individual process chambers can be reunited so as to be conveyed together to the filter system. This method presupposes that the same process gas atmosphere is used in all process chambers. This is not a problem if the construction materials in the process chambers are the same, but if different construction materials are used in the process chambers, the same process gas, for example a protective gas such as argon, can still be used.

[0065] A cyclone separator or centrifugal separator in the vicinity of the process gas outlet of the treatment chamber or upstream of the process gas inlet of the filter system has the advantage that coarse impurities can be separated from the process gas flow before they contaminate the pipeline system for gas transport or the filter system and, in the worst case, clog these systems.

[0066] In particular, the processing chambers can belong to different additive manufacturing systems for which a common (central) filter system is provided. The provision of a common filter system reduces costs on the one hand, since not every additive manufacturing system has to be equipped with a complex filter system individually. In addition, impurities removed from the filters and replaced filters filled with impurities are difficult materials to handle. On the one hand, depending on the construction materials used, they can spontaneously ignite or even explode when in contact with air. On the other hand, impurity residues on the filters can also pose a health hazard to personnel who have to handle them. In any case, the central handling of these hazardous substances makes it easier to dispose of them safely and in a controlled manner, since the complex equipment for handling these substances (e.g. a suitable protective gas atmosphere) only needs to be stored at one location.

[0067] Preferably, at least three process chambers are connected to the filter system, in particular to ensure that the number of process chambers through which process gas flows exceeds the number of process chambers through which process gas does not flow, as long as the production method is carried out in one of the process chambers.

[0068] If the additive manufacturing processes in different process chambers do not completely overlap in time, in particular have different durations, it is often desirable to isolate the process chamber that has completed the manufacturing method from the process gas circuit, for example, in order to be able to remove the manufactured object. This may also lead to sudden changes in the flow resistance, which can be counteracted by the described treatment method in order not to affect the manufacturing process in the process chamber that is still flowed through by the process gas.

[0069] A further method according to the invention is for providing a process gas atmosphere during an additive manufacturing method for producing a three-dimensional object in a plurality of process chambers of a plurality of additive manufacturing devices, in each of which at least one object is produced, by applying a building material layer by layer in the process chambers and curing the building material by supplying radiation energy to curing locations in each layer corresponding to the cross section of the object in this layer, wherein a gas circulation system is present, which has a closed gas circuit for a process gas guided through the process chambers, wherein a filter system with a number, preferably a plurality, of filter chambers is arranged in the closed gas circuit, wherein the filter system is connected to at least two process chambers, wherein particularly preferably each process chamber is equipped with at least one centrifuge, wherein the method for producing a three-dimensional object is carried out in each of the at least two process chambers with temporal overlap, wherein at least three process chambers are connected to the filter system, in particular to ensure that the number of process chambers through which the process gas flows exceeds the number of process chambers through which the process gas does not flow, as long as the manufacturing method is carried out in one of the process chambers.

[0070] In an additive manufacturing method according to the invention for manufacturing a three-dimensional object in a process chamber of an additive manufacturing device, wherein the object is manufactured by means of the additive manufacturing device in that a building material is applied layer by layer into the process chamber and the building material is cured by delivering radiation energy to curing locations in each layer that correspond to the cross-section of the object in this layer, the method according to the invention for providing a process gas atmosphere is used during the manufacturing method.

[0071] This additive manufacturing method allows the manufacture of objects with higher quality.

[0072] Further features and advantages of the invention emerge from the description of exemplary embodiments with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In the attached picture:

[0074] Figure 1 The schematic diagram shows an exemplary additive manufacturing device according to the invention, partially in section, which has an exemplary device according to the invention for providing a process gas atmosphere.

[0075] Figure 2 A schematic diagram showing one embodiment of an apparatus for providing a process gas atmosphere is shown.

[0076] Figure 3 Show Figure 2 , in which an exemplary arrangement of sensors in a gas circuit is additionally shown.

[0077] Figure 4 An exemplary process for cleaning a filter element is shown.

[0078] Figure 5 An exemplary method sequence is shown for replacing or cleaning filter elements. DETAILED DESCRIPTION

[0079] The following reference Figure 1 First, the basic structure of the additive manufacturing equipment involved in the present invention is explained by taking a laser sintering device or a laser melting device as an example. Figure 1 The laser melting system 1 shown in FIG. 1 comprises a process chamber 3 having a chamber wall 4 for forming an object 2 .

[0080] Arranged in the treatment chamber 3 is an upwardly open container 5 having a container wall 6. The upper opening of the container 5 defines a working plane 10, wherein the region of the working plane 10 located within the opening and which can be used to construct the object 2 is referred to as the construction zone.

[0081] A support 7 that can move in a vertical direction V is arranged in the container 5, on which a base plate 8 is mounted, which closes the container 5 downwards and thus forms the bottom of the container. The base plate 8 can be a plate that is constructed separately from the support 7 and is fixed to the support 7, or the base plate can be constructed integrally with the support 7. Depending on the powder and process used, a construction platform 9 can also be mounted on the base plate 8 as a construction base plate, on which the object 2 is constructed. However, the object 2 can also be constructed directly on the base plate 8, so that the base plate serves as a construction base plate. Figure 1 In FIG. 1 , the object 2 to be formed in the container 5 on the building platform 9 is shown below the working plane 10 in an intermediate state with a plurality of solidified layers which are surrounded by the still unsolidified building material 11 .

[0082] The laser melting device 1 further comprises a supply container 12 for a powdered or pasty building material 13 curable by electromagnetic radiation and an applicator 14 for applying the building material 13 within the building zone, movable in a horizontal direction H. The applicator 14 preferably extends transversely to its direction of movement over the entire area to be coated.

[0083] The wall 4 of the process chamber 3 comprises, on its upper side, an induction window 15 for a laser beam 22 for curing the powder 13 .

[0084] The laser melting device 1 further comprises an irradiation device 20 having a laser 21 which generates a laser beam 22 which is deflected by a deflection device 23 and focused by a focusing device 24 via the coupling window 15 onto the working plane 10 .

[0085] The laser melting device 1 also has a control unit 29, by which the various components of the laser melting device 1 are controlled in a coordinated manner in order to perform the construction process. The control unit may include a CPU, the operation of which is controlled by a computer program (software). The computer program may be stored on a storage medium, from which the computer program may be downloaded into the device, in particular into the control unit. In the present application, the term "control unit" includes any computer-based control unit that is capable of controlling or regulating the operation of an additive manufacturing device, in particular the operation of a component of an additive manufacturing device. Here, the connection between the control unit and the controlled component does not necessarily have to be wired, but can also be achieved by means of radio, WLAN, NFC, Bluetooth, etc., in that the control unit has corresponding receivers and transmitters.

[0086] In operation, in order to apply a layer of building material, the support 7 is first lowered to a height corresponding to the desired layer thickness. The applicator 14 then moves through the building zone and applies a layer of building material 13 there onto the building substrate or onto an existing layer of building material that has already been selectively cured. The application takes place at least over the entire cross section of the object 2 to be produced, preferably over the entire building zone, i.e., the area defined by the container wall 6.

[0087] Subsequently, the cross section of the object 2 to be manufactured is scanned by the laser beam 22, so that the powdered building material 13 solidifies at locations corresponding to the cross section of the object 2 to be manufactured. In this case, the powder particles are partially or completely melted at these locations by means of the energy introduced by the irradiation, so that they are bonded to each other and exist as a solid after cooling. These steps are repeated until the object 2 is manufactured and can be removed from the processing chamber 3.

[0088] As already mentioned at the outset, when irradiating with a laser beam, depending on the type of building material used, in particular when sintering or melting metal powders, spatter, smoke, vapor and / or gases are generated, which propagate into the process chamber and have a negative impact on the production process, also known as welding smoke. In order to avoid such negative effects on the production process, the process gas flow is guided through the working plane 10. Therefore, in order to generate a laminar gas flow 33 above the working plane 10, the laser melting device 1 comprises a gas supply channel 31, a gas inlet nozzle 32, a gas outlet nozzle 34 and a gas exhaust channel 35. The gas supply and gas exhaust can be controlled by a separate gas control device 80 (in Figure 1 The gas exhausted from the process chamber 3 is controlled by the filter system 40 (shown separately from the control unit in FIG. 3 ), but can also be controlled by the control unit 29. The gas exhausted from the process chamber 3 is supplied to the filter system 40 via the gas exhaust channel 35, which filters out (especially metallic) impurities from the process gas and then supplies it to the process chamber 3 again via the gas supply channel 31. The gas supply channel 31, the gas inlet nozzle 32, the gas outlet nozzle 34, the gas exhaust channel 35 and the gas conveying device 50 (such as a circulation fan, especially a high-pressure fan) form a gas circulation system, which can realize that the process gas guided through the process chamber forms a closed gas loop during operation.

[0089] Figure 2 A schematic diagram of an example of an apparatus for providing a process gas atmosphere in a processing chamber is shown. In addition to the gas circulation system, the apparatus also has a filter system 40 and a gas control device 80, which are already Figure 1 is shown in and Figure 2 This is shown in more detail in Figure 2In the example of FIG. 4 , the filter system 40 includes three filter chambers 41 a , 41 b and 41 c , which are shown in the figure as sub-chambers of a main chamber that are separated from each other in an airtight manner, but may also be chambers that are separated from each other in space.

[0090] According to the invention, there are at least three filter chambers. In other words, there may also be more than Figure 2 The greater number of filter chambers shown in FIG. 1 and all descriptions of the method according to the invention in this application also apply equally to the presence of four, five or more filter chambers which can be arranged parallel to one another in the process gas circuit.

[0091] Each filter chamber 41a, 41b, 41c includes a filter element 43a, 43b or 43c. For example, a fabric filter or a PE sintered filter with 20 μm polyester fiber can be used as a filter element. In addition, in each filter chamber, there are untreated gas chambers 44a, 44b or 44c and clean gas chambers 45a, 45b or 45c on both sides of the filter elements 43a, 43b, 43c. Here, the gas containing impurities (usually referred to as untreated gas) can be supplied to each untreated gas chamber 44a, 44b or 44c through the gas exhaust channel 35. The filtered gas (usually referred to as clean gas) is supplied to the processing chamber 3 from each clean gas chamber 45a, 45b, 45c via the gas supply channel 31, and the filtered gas enters the gas inlet 32 ​​arranged in the chamber wall 4 at this place.

[0092] The gas inlet of the filter chamber is preferably designed so that the supplied gas flow is not directed directly to the filter element. For example, the gas can be directed laterally on a circular path into the filter chamber. This utilizes the cyclone effect and larger particles, such as co-conveyed components of the construction material (e.g. metal powder), cannot reach the filter element at all.

[0093] also, Figure 2 A gas delivery device 50, such as a high-pressure fan, arranged in the gas circuit is shown, wherein the flow direction in the gas circuit is shown by arrows. Not shown in the figure is a fine filter preferably present and arranged upstream of the gas delivery device 50 and an optional particle separator in the gas outlet channel 35, such as a centrifugal separator or a cyclone separator.

[0094] Over time, the filtered particles are deposited on the fabric of the filter element 43a, 43b or 43c. They are compacted by the pressure applied by the process gas flow and can agglomerate depending on the material and temperature. Therefore, over time, a filter material layer commonly referred to as a "filter cake" is formed by a compacted and / or mutually adhered particle layer. The filter cake hinders the gas flow and causes the pressure drop on the filter to increase continuously, that is, the increase of the pressure difference between the raw gas side and the clean gas side of the filter element, that is, the increase of the pressure difference between the raw gas chamber 44a, 44b or 44c and the clean gas chamber 45a, 45b or 45c. Therefore, the filter element 43a, 43b or 43c must be cleaned from time to time to remove or replace the filter cake.

[0095] With the help of Figure 4 The figure schematically shows a cleaning device 70 which is connected to the clean gas chamber 45a, 45b or 45c of the filter element 43a, 43b or 43c (in the figure, the clean gas chamber 45a and the filter element 43a are shown as examples).

[0096] In order to clean the filter element 43a, a gas pressure shock is generated by the cleaning device 70, which is introduced into the clean gas chamber 45a via the cleaning nozzle 71. For example, the cleaning device 70 can include a pressure vessel with pressurized protective gas for this purpose, from which individual gas pressure shocks are extracted as required. The gas pressure shock has a peak pressure of 5 or 10 bar, for example, and passes through the filter element 43a to be cleaned in the opposite direction to the normal filtering direction, in which the process gas to be filtered flows through the filter element 43a. As a result, the gas pressure shock acts on the filter cake from the outlet side of the filter element 43a. The filter cake is thus flatly detached from the filter element 43a, broken into pieces and pressed away from the filter element 43a by the gas pressure shock. The individual pieces of the filter cake fall downward due to gravity attraction and reach the collecting funnel 72, in the lower section of which there is a closure 73, such as an iris baffle or a pneumatic / electrically actuated disc valve, by means of which the collecting funnel 72 can be closed gas-tightly downward. Below it is a collecting container 74 (sometimes also referred to as a waste container). Optionally, a passivation connection 75 is provided, which can be used to fill the collecting container 74 with passivation material. However, it is also possible not to introduce passivation material. In addition, a protective gas connection (not shown in the figure) can be optionally provided in the collecting container 74 for introducing protective gas, which can be the same protective gas used in the process chamber. For the sake of clarity, in the schematic diagram Figure 4 Further device details known to the person skilled in the art, such as, for example, venting of the filter chamber for inerting or level sensors or pressure sensors in the collecting container 74 , are not shown.

[0097] like Figure 2 As shown, the gas outlet channel 35 is divided into three sub-channels (without reference numerals), through which the gas to be filtered is supplied to the unprocessed gas chambers 44a, 44b, 44c of the filter chambers 41a, 41b, 41c. The outlets of the clean gas chambers 45a, 45b, 45c are also brought together so that the filtered gas is supplied to the processing chamber 3 via the gas supply channel 31. Here, the gas supply to the unprocessed gas chambers 44a, 44b, 44c can be interrupted individually by switching units 36a, 36b, 36c (for example, valves that can be electrically or electromagnetically operated). Similarly, the gas discharged from the clean gas chambers 45a, 45b, 45c can be interrupted individually by switching units 37a, 37b, 37c (for example, valves that can be electrically or electromagnetically operated). It can be ensured that when the filter element is replaced, no ambient air enters the process gas atmosphere or when the filter element is cleaned by means of a gas pressure shock, the pressure in the processing chamber is not negatively affected.

[0098] exist Figure 2 , a gas control device 80 is shown, which is connected to the switch units 36a, 36b, 36c and the switch units 37a, 37b, 37c by means of control lines (without reference numerals) shown with dashed lines, so as to be able to operate these switch units. Although the control lines are clearly shown in the figures, it should also be understood that the communication between the gas control device 80 and the individual switch units can also be carried out wirelessly, for example by means of radio, WLAN, NFC, Bluetooth, etc., in that the control unit and the individual switch units have corresponding receivers and transmitters. The same applies to the optional control signal connection between the gas control device 80 and the gas delivery device 50.

[0099] In the case where one or more filter elements, such as filter element 43a, should be cleaned or replaced, the gas control device 80 controls the corresponding switch units, such as 36a and 37a, so as to disconnect the assigned filter chamber 41a from the gas circuit passing through the processing chamber 3. Here, the gas control device 80 ensures that the number of filter chambers arranged in the gas circuit exceeds the number of filter chambers not arranged in the gas circuit. For example, the control system (for example, executed by means of software) in the gas control device is designed accordingly. In particular, the device can check whether the number of filter chambers to be disconnected from the gas circuit passing through the processing chamber 3 is greater than or equal to the number of filter chambers remaining in the gas circuit passing through the processing chamber 3, and if so, automatically disconnect the smaller number of filter chambers from the gas circuit. In particular, this can also be done step by step. This means that first check whether the number of filter chambers to be disconnected is still greater than or equal to the number of filter chambers remaining in the gas circuit passing through the processing chamber 3 by reducing the number of filter chambers to be disconnected, and if so, reduce the number of filter chambers to be disconnected by one more to check again. Only when it is checked that the number of filter chambers to be disconnected is less than the number of filter chambers remaining in the gas circuit, the current number of filter chambers to be disconnected is actually disconnected from the gas circuit.

[0100] In order to determine how many filter chambers are currently arranged in the gas circuit and / or how many filter chambers are disconnected, the gas control device can check the switching state of the switch unit 36a, 36b, 36c, 37a, 37b or 37c. However, the value N of the maximum permissible number of filter chambers that can be disconnected from the gas circuit at the same time can be set. max The gas control device then compares the number of filter chambers currently disconnected from the gas circuit with the value N. max For comparison, if the next filter chamber is disconnected, the value N will be exceeded. max , for example, a blocking mark is set. The total number N of filter chambers that can be connected to the processing chamber can be total Fixed preset value N for the maximum number of filter chambers that can be disconnected from the gas circuit at the same time max Alternatively, this value can be input by a user of the additive manufacturing device before the start of the manufacturing process, in particular after a change in the number of filter chambers provided for filtering the process gas flow.

[0101] In an alternative method, when the filter element should be cleaned or replaced, the maximum permissible number N is always max The filter chambers are separated from the gas circuit. In this way, it is also ensured that the number of filter chambers arranged in the gas circuit always exceeds the number of filter chambers not arranged in the gas circuit.

[0102] It should be understood that the same approach can be used if the ratio of the number of filter chambers not isolated from the process gas circuit to the number of filter chambers isolated from the process gas circuit (e.g. 2:1) is not less than that ensured. In this case, the variable N can be adjusted accordingly. max The value of .

[0103] Optionally, the gas control device 80 may output a warning signal whenever the number of filter chambers to be disconnected from the gas circuit passing through the process chamber 3 is greater than or equal to the number of filter chambers remaining in the gas circuit passing through the process chamber 3 or is lower than the ratio of the number of filter chambers not isolated from the process gas circuit to the number of filter chambers isolated from the process gas circuit. The warning signal may be an acoustic and / or optical signal.

[0104] In the case of three filter chambers, this means that it is ensured that at least two filter chambers are always arranged in the process gas circuit during the production process. In the case of four or five filter chambers, this means that it is ensured that at least three filter chambers are always arranged in the process gas circuit during the production process. In the case of six or seven filter chambers, this means that it is ensured that at least four filter chambers are always arranged in the process gas circuit during the production process.

[0105] Sensors arranged upstream and downstream of the filter chamber in the gas circuit can be used to determine when the filter element should be replaced or cleaned. Figure 3 To illustrate this point.

[0106] Figure 3 and Figure 2 Very similar to Figure 2 The difference is that in Figure 3 Also shown are sensors 38a, 38b, 38c, 38g, 39a, 39b, 39c and 39g, which are Figure 2 The pressure difference between the filter chamber 41a, 41b and 41c can be determined by comparing the values ​​determined by the sensors 38a and 39a, 38b and 39b or 38c and 39c. If the pressure difference applied to a filter chamber exceeds a preset maximum value, it can be used as an indication that the filter element in the corresponding filter chamber should be replaced or cleaned.

[0107] Although two sensors 38g and 39g are shown in addition to sensors 38a, 38b, 38c, 39a, 39b and 39c, they can also be arranged in the gas circuit instead of sensors 38a, 38b, 38c, 39a, 39b and 39c. By comparing the values ​​determined by sensors 38g and 39g, the pressure difference applied to the filter chambers arranged parallel to each other in the gas circuit can be determined, and based on this pressure difference it can be determined whether a certain filter element must be replaced or cleaned. It should be noted that, alternatively or additionally, the pressure difference of only a part of the entirety of the filter chambers arranged parallel to each other in the gas circuit can also be determined by means of two sensors upstream and downstream of this part of the filter in the gas circuit.

[0108] exist Figure 3 In the figure, for the sake of clarity, reference numeral 90 generally represents a signal line (dashed line) between the sensor and the gas control device 80, through which the pressure values ​​determined by the various sensors can be transmitted to the gas control device 80, and represents a signal line between the gas control device 80 and the switch unit. The gas control device 80 can determine the pressure difference applied to the filter chamber based on the pressure value transmitted by the sensor and independently decide when the filter element needs to be replaced or cleaned. Although the signal line is clearly shown in the figure, it should be understood that the communication can also be wireless, for example by means of radio, WLAN, NFC, Bluetooth, etc., in that the gas control device and the various switch units have corresponding receivers and transmitters.

[0109] at last, Figure 3 Also shown is a sensor 51 for determining the volume flow in the gas circuit, which is likewise connected to the gas control device 80 via a signal connection. Figure 3 In the embodiment, the sensor 51 is shown as being located upstream of the gas delivery device 50, but it can also be arranged downstream as an alternative. If the sensor 51 indicates that the volume flow has fallen below a preset minimum value, it can be decided independently of the pressure difference value determined by means of the pressure sensor that the filter element should be cleaned or replaced. However, if the pressure difference value applied to the individual filter chambers is also taken into account for the decision, it can be decided quite differently when and which filter elements should be cleaned or replaced by the interaction of the information of the pressure sensor and the sensor for the volume flow.

[0110] Refer to the following Figure 5 A possible method sequence is described when replacing or cleaning a number of filter elements with the aid of a correspondingly adapted gas control device 80. The starting point of the method sequence (step S0) is the decision at which time the filter elements in a plurality of filter chambers must be replaced or cleaned. This decision can be made automatically by the gas control device 80, for example, based on the pressure differences present at the individual filter chambers.

[0111] Next, in step S1, it is determined whether the number N of filter cavities of the filter element that must be replaced or cleaned i Is it greater than or equal to the total number of filter chambers N that can be connected to the additive manufacturing equipment during the manufacturing process? total If yes, then step S1' is executed, in which the number of filter cavities N is checked. i-1 Is it also greater than or equal to half of the total number of filter chambers? If this is not the case, method step S2 is then performed. If the number of filter chambers N i-1 is also greater than or equal to half of the total number of filter cavities, then check the number of filter cavities N in turn i-2 、N i-3 Is it greater than or equal to half of the total number of filter cavities, until the number N i-j (j>1) is no longer the case, and the method can then proceed to step S2.

[0112] In step S2, the gas control device 80 controls the switch units downstream and upstream of those filter chambers whose filter elements are to be cleaned or replaced in order to isolate these filter chambers from the gas flow. If method step S1' has already been performed, then N is not isolated accordingly. i filter chambers, but separate N i-1 or N i-j A filter chamber.

[0113] Then, in step S3, a cleaning process of the filter elements is carried out in the separated filter chambers or a replacement of the filter elements in these filter chambers is carried out in a known manner. Then, at the end of the cleaning process or the replacement process, an end signal is transmitted to the gas control device 80. This is done automatically during the cleaning process and can also be done during the replacement process, but it can also be done manually. After receiving the end signal indicating that the filter chamber is ready for use again, in step S4, the gas control device 80 reopens the switch unit downstream and upstream of the filter chamber so that the process gas flows through the filter chamber again.

[0114] It should be noted that the filter chambers to be separated from the gas circuit do not necessarily have to be separated from the gas circuit at the same time, but can also be separated from the gas circuit one after the other. This applies in particular if the pressure difference in each filter chamber is not determined individually by means of sensors upstream and downstream of each filter chamber, but for example by means of Figure 3 The sensors 38g and 39g in the filter chamber determine the overall pressure difference of a plurality of filter chambers arranged parallel to one another in the air flow.

[0115] In addition, if the number of filter cavities N of the filter element that must be replaced or cleaned is not checked i Is it greater than or equal to the total number of filter cavities N? totalInstead, check the total number of filter cavities N. total With the number N i The difference between the number N i The ratio of (N total -N i ) / N i If it is lower than the preset minimum value, you can refer to Figure 5 The described method sequence is carried out in the same way.

[0116] Finally, it should be pointed out again that the device described in detail above is only an embodiment, which can be modified by a person skilled in the art in completely different ways without departing from the scope of the invention. For example, instead of using a laser, curing can also be carried out with the help of other energy beams. In addition, the use of the indefinite article "a" does not exclude that the feature involved can also be multiple. Similarly, the term "unit" does not exclude that it consists of a plurality of cooperating subcomponents, which can also be spatially distributed if necessary. The term "some" should be understood as "at least one".

Claims

1. A device for providing a process gas atmosphere in a process chamber (3) of an additive manufacturing device during a method for manufacturing a three-dimensional object (2), wherein the object is manufactured by applying a building material (13) layer by layer and curing the building material by delivering radiation energy to a curing location in each layer, the curing location corresponding to the cross section of the object in this layer, The device for providing a process gas atmosphere has a gas circulation system with a gas circuit which is closed during operation for a process gas which is conducted through the treatment chamber (3), wherein: A filter system (40) having a plurality of filter chambers (41a, 41b, 41c) is arranged in the closed gas circuit. characterised in that there are at least three filter chambers, each of which has at least one filter element (43a, 43b, 43c) for filtering particles in the gas circuit, and A gas control device (80) is provided for controlling a gas circuit, the gas control device being arranged such that it can isolate some filter chambers (41a, 41b, 41c) from the gas circuit during an ongoing manufacturing method and thereby ensure that the number of filter chambers remaining in the gas circuit at least temporarily, preferably permanently, exceeds the number of filter chambers isolated from the gas circuit.

2. The device according to claim 1, wherein: Each of the filter chambers (41a, 41b, 41c) has at least one filter element (43a, 43b, 43c) for filtering particles in the gas circuit, wherein the filter element can be cleaned by a gas pressure surge and / or can be replaced.

3. The device according to claim 1 or 2, wherein: The plurality of filter chambers (41a, 41b, 41c) have substantially the same volume, and / or The filter elements (43a, 43b, 43c) have substantially the same filter surface and / or the same filter medium, and / or The inlet pipes and the outlet pipes respectively connected to the plurality of filter chambers (41a, 41b, 41c) have substantially the same opening cross-sections.

4. The device according to any one of the preceding claims, wherein: The gas control device (80) is arranged so that it ensures that during the ongoing manufacturing method, the ratio of the number of filter chambers that are not isolated from the process gas circuit to the number of filter chambers that are isolated from the process gas circuit is at least temporarily, preferably continuously, greater than or equal to a minimum value of 55:45, preferably 60:40, more preferably 2:1, even more preferably 70:30, even more preferably 3:1, and particularly preferably 4:

1.

5. Apparatus according to any one of the preceding claims, wherein: All filter chambers ( 41 a , 41 b , 41 c ) arranged in the gas circuit are always arranged in parallel connection with one another.

6. The device according to any one of the preceding claims, wherein: The at least three filter chambers (41a, 41b, 41c) are sub-chambers of one or more main chambers of the filter system (40) that are separated from each other in an airtight manner.

7. Apparatus according to any one of the preceding claims, wherein: For each of the at least three filter chambers (41a, 41b, 41c), a switch unit (36a, 36b, 36c) is arranged upstream and / or a switch unit (37a, 37b, 37c) is arranged downstream, by means of which the filter chamber can be isolated from the other filter chambers relative to the gas circuit.

8. Apparatus according to any one of the preceding claims, wherein: For each of the at least three filter chambers (41a, 41b, 41c), a pressure sensor (38a, 38b, 38c, 39a, 39b, 39c) is arranged upstream and downstream, respectively, so that the pressure difference between the raw gas side and the clean gas side of the filter element (43a, 43b, 43c) in the filter chamber (41a, 41b, 41c) can be determined.

9. The device according to any one of claims 1 to 7, wherein: In order to determine the pressure difference between the raw gas side and the clean gas side of multiple filter chambers, preferably all filter chambers, a pressure sensor (38g) is arranged upstream of the branching part of the supply pipeline of the raw gas to the multiple filter chambers, and a pressure sensor (39g) is arranged downstream of the confluence of the discharge pipeline of the clean gas from the multiple filter chambers, and the pressure difference is determined by comparing the pressure values ​​of the two pressure sensors.

10. The device according to claim 8 or 9, wherein: The gas control device (80) is connected to pressure sensors upstream and downstream of the filter chamber via signal connections (90) and is arranged to initiate cleaning of the filter element between these pressure sensors if the pressure difference received by the pressure sensors exceeds a preset maximum value.

11. Apparatus according to any one of the preceding claims, wherein: A sensor (51) for determining the volume flow of the process gas in the closed gas circuit is arranged downstream of the filter system and is connected to the gas control device via a signal connection, wherein the gas control device is configured to initiate cleaning of the filter element if the value of the volume flow received by the sensor is below a preset minimum value.

12. Apparatus according to any one of the preceding claims, wherein: The gas circulation system has a fan (50).

13. An additive manufacturing device comprising: a processing chamber (3) for manufacturing a three-dimensional object, The additive manufacturing device comprises a device according to any one of claims 1 to 12.

14. A method for providing a process gas atmosphere in a processing chamber (3) of an additive manufacturing device during a method for manufacturing a three-dimensional object (2), wherein the object is manufactured by applying a building material (13) layer by layer and curing the building material by delivering radiation energy to a curing location in each layer, the curing location corresponding to the cross section of the object in this layer, In a method for providing a process gas atmosphere, a process gas guided through the treatment chamber (3) is moved in a closed gas circuit by means of a gas circulation system, wherein: A filter system (40) having a plurality of filter chambers (41a, 41b, 41c) is arranged in the closed gas circuit. Characterized in that there are at least three filter chambers, each of which has at least one filter element (43a, 43b, 43c) for filtering particles in the gas circuit, the filter element being cleanable by gas pressure shocks, and During the ongoing production method, some filter chambers (41a, 41b, 41c) are isolated from the gas circuit, wherein it is ensured that the number of filter chambers remaining in the gas circuit at least temporarily, preferably permanently, exceeds the number of filter chambers isolated from the gas circuit.

15. The method according to claim 14, wherein: In a filter chamber (41a, 41b, 41c) arranged in the gas circuit, a pressure difference applied to a filter element (43a, 43b, 43c) arranged in the filter chamber is determined, and when the determined pressure difference exceeds a preset maximum value, the filter element is cleaned.

16. The method according to claim 14 or 15, wherein: The process gas is moved in a closed gas circuit at a volume flow rate that exceeds 50 m 3 / h, preferably 100 m 3 / h, preferably 200 m 3 / h, and / or less than 2000 m 3 / h, preferably 500 m 3 / h, preferably 400 m 3 / h.

17. The method according to any one of claims 14 to 16, wherein: The value of the volume flow of the process gas downstream of the filter system (40) in the closed gas circuit is determined, and the filter elements (43a, 43b, 43c) are cleaned when the value of the determined volume flow is below a predefined minimum value.

18. A method according to any one of the preceding claims, wherein: The filtering system (40) is connected to at least two processing chambers (3a, 3b) of some additive manufacturing equipment, Particularly preferably, each treatment chamber (3a, 3b) is equipped with at least one centrifuge. The method for producing a three-dimensional object is performed in each of the at least two process chambers (3a, 3b) with temporal overlap.

19. The method according to claim 18, wherein: At least three process chambers are connected to the filter system (40), in particular to ensure that the number of process chambers through which process gas flows exceeds the number of process chambers through which process gas does not flow, as long as the production method is carried out in one of the process chambers.

20. An additive manufacturing method for manufacturing a three-dimensional object in a processing chamber of an additive manufacturing device, in, An object (2) is manufactured by means of the additive manufacturing device, in the following manner: A construction material (13) is applied layer by layer in the processing chamber (3), and the construction material is cured by delivering radiation energy to a curing location in each layer, the curing location corresponding to a cross section of the object in the layer. Therein, the method according to any one of claims 14 to 19 is used during the production method.

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